diff --git a/OWNERS b/OWNERS
index 682a067..96b4f54 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1 +1,2 @@
+# Bug component: 128577
 enh@google.com
diff --git a/bootstat/Android.bp b/bootstat/Android.bp
index ca59ef3..0c8760c 100644
--- a/bootstat/Android.bp
+++ b/bootstat/Android.bp
@@ -72,9 +72,6 @@
     ],
     init_rc: ["bootstat.rc"],
     product_variables: {
-        pdk: {
-            enabled: false,
-        },
         debuggable: {
             init_rc: ["bootstat-debug.rc"],
         },
diff --git a/debuggerd/Android.bp b/debuggerd/Android.bp
index d20de6b..5393e25 100644
--- a/debuggerd/Android.bp
+++ b/debuggerd/Android.bp
@@ -188,6 +188,7 @@
 cc_library_static {
     name: "libdebuggerd",
     defaults: ["debuggerd_defaults"],
+    ramdisk_available: true,
     recovery_available: true,
     vendor_ramdisk_available: true,
 
@@ -221,9 +222,6 @@
         "libbase",
         "libcutils",
     ],
-    runtime_libs: [
-        "libdexfile",           // libdexfile_support dependency
-    ],
 
     whole_static_libs: [
         "libasync_safe",
@@ -250,6 +248,19 @@
                 "libdexfile",
             ],
         },
+        ramdisk: {
+            exclude_static_libs: [
+                "libdexfile_support",
+            ],
+            exclude_runtime_libs: [
+                "libdexfile",
+            ],
+        },
+        android: {
+            runtime_libs: [
+                "libdexfile",           // libdexfile_support dependency
+            ],
+        },
     },
 
     product_variables: {
diff --git a/debuggerd/crasher/arm/crashglue.S b/debuggerd/crasher/arm/crashglue.S
index e4adf40..0def8ae 100644
--- a/debuggerd/crasher/arm/crashglue.S
+++ b/debuggerd/crasher/arm/crashglue.S
@@ -23,10 +23,11 @@
 	ldr lr, [lr]
 	b .
 	.cfi_endproc
+	.size crash1, .-crash1
 
-.globl crashnostack
-.type crashnostack, %function
-crashnostack:
+.globl crash_no_stack
+.type crash_no_stack, %function
+crash_no_stack:
 	.cfi_startproc
 	mov r1, sp
 	.cfi_def_cfa_register r1
@@ -35,3 +36,4 @@
 	ldr r0, [r0]
 	b .
 	.cfi_endproc
+	.size crash_no_stack, .-crash_no_stack
diff --git a/debuggerd/crasher/arm64/crashglue.S b/debuggerd/crasher/arm64/crashglue.S
index 97c824e..c56e19a 100644
--- a/debuggerd/crasher/arm64/crashglue.S
+++ b/debuggerd/crasher/arm64/crashglue.S
@@ -41,11 +41,12 @@
 	ldr x30, [x30]
 	b .
 	.cfi_endproc
+	.size crash1, .-crash1
 
 
-.globl crashnostack
-.type crashnostack, %function
-crashnostack:
+.globl crash_no_stack
+.type crash_no_stack, %function
+crash_no_stack:
 	.cfi_startproc
 	mov x1, sp
 	.cfi_def_cfa_register x1
@@ -54,3 +55,41 @@
 	ldr x0, [x0]
 	b .
 	.cfi_endproc
+	.size crash_no_stack, .-crash_no_stack
+
+
+.globl crash_bti
+.type crash_bti, %function
+crash_bti:
+	.cfi_startproc
+	adr x16, 1f
+	br x16
+1:	// Deliberatly not a bti instruction so we crash here.
+	b .
+	.cfi_endproc
+	.size crash_bti, .-crash_bti
+
+
+.globl crash_pac
+.type crash_pac, %function
+crash_pac:
+	.cfi_startproc
+	paciasp
+	// Since sp is a pac input, this ensures a mismatch.
+	sub sp, sp, #16
+	autiasp
+	b .
+	.cfi_endproc
+	.size crash_pac, .-crash_pac
+
+// Set the PAC and BTI bits for this object file.
+.section .note.gnu.property, "a"
+.balign 8
+.long 4
+.long 0x10
+.long 0x5
+.asciz "GNU"
+.long 0xc0000000
+.long 4
+.long 0x3
+.long 0
diff --git a/debuggerd/crasher/crasher.cpp b/debuggerd/crasher/crasher.cpp
index 12ba502..3b52776 100644
--- a/debuggerd/crasher/crasher.cpp
+++ b/debuggerd/crasher/crasher.cpp
@@ -19,6 +19,7 @@
 #include <assert.h>
 #include <dirent.h>
 #include <errno.h>
+#include <error.h>
 #include <fcntl.h>
 #include <pthread.h>
 #include <signal.h>
@@ -29,6 +30,9 @@
 #include <sys/prctl.h>
 #include <unistd.h>
 
+#include <android-base/file.h>
+#include <android-base/strings.h>
+
 // We test both kinds of logging.
 #include <android-base/logging.h>
 #include <log/log.h>
@@ -59,8 +63,10 @@
 // Avoid name mangling so that stacks are more readable.
 extern "C" {
 
-void crash1(void);
-void crashnostack(void);
+void crash1();
+void crash_no_stack();
+void crash_bti();
+void crash_pac();
 
 int do_action(const char* arg);
 
@@ -196,13 +202,6 @@
     fprintf(stderr, "  fdsan_file            close a file descriptor that's owned by a FILE*\n");
     fprintf(stderr, "  fdsan_dir             close a file descriptor that's owned by a DIR*\n");
     fprintf(stderr, "  seccomp               fail a seccomp check\n");
-#if defined(__arm__)
-    fprintf(stderr, "  kuser_helper_version  call kuser_helper_version\n");
-    fprintf(stderr, "  kuser_get_tls         call kuser_get_tls\n");
-    fprintf(stderr, "  kuser_cmpxchg         call kuser_cmpxchg\n");
-    fprintf(stderr, "  kuser_memory_barrier  call kuser_memory_barrier\n");
-    fprintf(stderr, "  kuser_cmpxchg64       call kuser_cmpxchg64\n");
-#endif
     fprintf(stderr, "  xom                   read execute-only memory\n");
     fprintf(stderr, "\n");
     fprintf(stderr, "  LOG_ALWAYS_FATAL      call liblog LOG_ALWAYS_FATAL\n");
@@ -223,6 +222,20 @@
     fprintf(stderr, "\n");
     fprintf(stderr, "  no_new_privs          set PR_SET_NO_NEW_PRIVS and then abort\n");
     fprintf(stderr, "\n");
+#if defined(__arm__)
+    fprintf(stderr, "Also, since this is an arm32 binary:\n");
+    fprintf(stderr, "  kuser_helper_version  call kuser_helper_version\n");
+    fprintf(stderr, "  kuser_get_tls         call kuser_get_tls\n");
+    fprintf(stderr, "  kuser_cmpxchg         call kuser_cmpxchg\n");
+    fprintf(stderr, "  kuser_memory_barrier  call kuser_memory_barrier\n");
+    fprintf(stderr, "  kuser_cmpxchg64       call kuser_cmpxchg64\n");
+#endif
+#if defined(__aarch64__)
+    fprintf(stderr, "Also, since this is an arm64 binary:\n");
+    fprintf(stderr, "  bti                   fail a branch target identification (BTI) check\n");
+    fprintf(stderr, "  pac                   fail a pointer authentication (PAC) check\n");
+#endif
+    fprintf(stderr, "\n");
     fprintf(stderr, "prefix any of the above with 'thread-' to run on a new thread\n");
     fprintf(stderr, "prefix any of the above with 'exhaustfd-' to exhaust\n");
     fprintf(stderr, "all available file descriptors before crashing.\n");
@@ -231,6 +244,21 @@
     return EXIT_FAILURE;
 }
 
+[[maybe_unused]] static void CheckCpuFeature(const std::string& name) {
+    std::string cpuinfo;
+    if (!android::base::ReadFileToString("/proc/cpuinfo", &cpuinfo)) {
+        error(1, errno, "couldn't read /proc/cpuinfo");
+    }
+    std::vector<std::string> lines = android::base::Split(cpuinfo, "\n");
+    for (std::string_view line : lines) {
+        if (!android::base::ConsumePrefix(&line, "Features\t:")) continue;
+        std::vector<std::string> features = android::base::Split(std::string(line), " ");
+        if (std::find(features.begin(), features.end(), name) == features.end()) {
+          error(1, 0, "/proc/cpuinfo does not report feature '%s'", name.c_str());
+        }
+    }
+}
+
 noinline int do_action(const char* arg) {
     // Prefixes.
     if (!strncmp(arg, "wait-", strlen("wait-"))) {
@@ -256,7 +284,7 @@
     } else if (!strcasecmp(arg, "stack-overflow")) {
       overflow_stack(nullptr);
     } else if (!strcasecmp(arg, "nostack")) {
-      crashnostack();
+      crash_no_stack();
     } else if (!strcasecmp(arg, "exit")) {
       exit(1);
     } else if (!strcasecmp(arg, "call-null")) {
@@ -350,6 +378,14 @@
     } else if (!strcasecmp(arg, "kuser_cmpxchg64")) {
         return __kuser_cmpxchg64(0, 0, 0);
 #endif
+#if defined(__aarch64__)
+    } else if (!strcasecmp(arg, "bti")) {
+        CheckCpuFeature("bti");
+        crash_bti();
+    } else if (!strcasecmp(arg, "pac")) {
+        CheckCpuFeature("paca");
+        crash_pac();
+#endif
     } else if (!strcasecmp(arg, "no_new_privs")) {
         if (prctl(PR_SET_NO_NEW_PRIVS, 1) != 0) {
           fprintf(stderr, "prctl(PR_SET_NO_NEW_PRIVS, 1) failed: %s\n", strerror(errno));
diff --git a/debuggerd/crasher/riscv64/crashglue.S b/debuggerd/crasher/riscv64/crashglue.S
index 42f59b3..f179e33 100644
--- a/debuggerd/crasher/riscv64/crashglue.S
+++ b/debuggerd/crasher/riscv64/crashglue.S
@@ -43,10 +43,11 @@
 	ld t2, 0(zero)
 	j .
 	.cfi_endproc
+	.size crash1, .-crash1
 
 
-.globl crashnostack
-crashnostack:
+.globl crash_no_stack
+crash_no_stack:
 	.cfi_startproc
 	mv t1, sp
 	.cfi_def_cfa_register t1
@@ -54,3 +55,4 @@
 	ld t2, 0(zero)
 	j .
 	.cfi_endproc
+	.size crash_no_stack, .-crash_no_stack
diff --git a/debuggerd/crasher/x86/crashglue.S b/debuggerd/crasher/x86/crashglue.S
index e8eb3a7..453035b 100644
--- a/debuggerd/crasher/x86/crashglue.S
+++ b/debuggerd/crasher/x86/crashglue.S
@@ -6,13 +6,15 @@
 
 	movl $0, %edx
 	jmp *%edx
+	.size crash1, .-crash1
 
 
-.globl crashnostack
-crashnostack:
+.globl crash_no_stack
+crash_no_stack:
 	.cfi_startproc
 	movl %esp, %eax
 	.cfi_def_cfa_register %eax
 	movl $0, %esp
 	movl (%esp), %ebx
 	.cfi_endproc
+	.size crash_no_stack, .-crash_no_stack
diff --git a/debuggerd/crasher/x86_64/crashglue.S b/debuggerd/crasher/x86_64/crashglue.S
index 8f67214..c3d39c4 100644
--- a/debuggerd/crasher/x86_64/crashglue.S
+++ b/debuggerd/crasher/x86_64/crashglue.S
@@ -6,13 +6,15 @@
 
 	movl $0, %edx
 	jmp *%rdx
+	.size crash1, .-crash1
 
 
-.globl crashnostack
-crashnostack:
+.globl crash_no_stack
+crash_no_stack:
 	.cfi_startproc
 	movq %rsp, %rax
 	.cfi_def_cfa_register %rax
 	movq $0, %rsp
 	movq (%rsp), %rbx
 	.cfi_endproc
+	.size crash_no_stack, .-crash_no_stack
diff --git a/debuggerd/proto/Android.bp b/debuggerd/proto/Android.bp
index 73cf573..804f805 100644
--- a/debuggerd/proto/Android.bp
+++ b/debuggerd/proto/Android.bp
@@ -35,6 +35,7 @@
         "com.android.runtime",
     ],
 
+    ramdisk_available: true,
     recovery_available: true,
     vendor_ramdisk_available: true,
 }
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index faee5e2..71a228e 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -120,6 +120,9 @@
 static std::vector<Image> images = {
         // clang-format off
     { "boot",     "boot.img",         "boot.sig",     "boot",     false, ImageType::BootCritical },
+    { "bootloader",
+                  "bootloader.img",   "",             "bootloader",
+                                                                  true,  ImageType::Extra },
     { "init_boot",
                   "init_boot.img",    "init_boot.sig",
                                                       "init_boot",
@@ -132,6 +135,7 @@
     { "odm_dlkm", "odm_dlkm.img",     "odm_dlkm.sig", "odm_dlkm", true,  ImageType::Normal },
     { "product",  "product.img",      "product.sig",  "product",  true,  ImageType::Normal },
     { "pvmfw",    "pvmfw.img",        "pvmfw.sig",    "pvmfw",    true,  ImageType::BootCritical },
+    { "radio",    "radio.img",        "",             "radio",    true,  ImageType::Extra },
     { "recovery", "recovery.img",     "recovery.sig", "recovery", true,  ImageType::BootCritical },
     { "super",    "super.img",        "super.sig",    "super",    true,  ImageType::Extra },
     { "system",   "system.img",       "system.sig",   "system",   false, ImageType::Normal },
@@ -630,6 +634,9 @@
             " --skip-reboot              Don't reboot device after flashing.\n"
             " --disable-verity           Sets disable-verity when flashing vbmeta.\n"
             " --disable-verification     Sets disable-verification when flashing vbmeta.\n"
+            " --disable-super-optimization\n"
+            "                            Disables optimizations on flashing super partition.\n"
+            " --disable-fastboot-info    Will collects tasks from image list rather than $OUT/fastboot-info.txt.\n"
             " --fs-options=OPTION[,OPTION]\n"
             "                            Enable filesystem features. OPTION supports casefold, projid, compress\n"
             // TODO: remove --unbuffered?
@@ -1949,7 +1956,6 @@
     }
     ZipImageSource zp = ZipImageSource(zip);
     fp->source = &zp;
-    fp->wants_wipe = false;
     FlashAllTool tool(fp);
     tool.Flash();
 
diff --git a/fastboot/fastboot.h b/fastboot/fastboot.h
index 3fb00e0..75b8d29 100644
--- a/fastboot/fastboot.h
+++ b/fastboot/fastboot.h
@@ -27,6 +27,7 @@
  */
 #pragma once
 
+#include <functional>
 #include <string>
 #include "fastboot_driver.h"
 #include "fastboot_driver_interface.h"
diff --git a/fs_mgr/Android.bp b/fs_mgr/Android.bp
index 0a836e4..87db98b 100644
--- a/fs_mgr/Android.bp
+++ b/fs_mgr/Android.bp
@@ -60,7 +60,6 @@
     defaults: ["fs_mgr_defaults"],
     export_include_dirs: ["include"],
     local_include_dirs: ["include/"],
-    include_dirs: ["system/vold"],
     cflags: [
         "-D_FILE_OFFSET_BITS=64",
     ],
@@ -90,8 +89,6 @@
     static_libs: [
         "libavb",
         "libfs_avb",
-        "libfstab",
-        "libdm",
         "libgsi",
     ],
     export_static_lib_headers: [
@@ -175,44 +172,22 @@
 }
 
 cc_library_static {
-    // Do not ever make this a shared library as long as it is vendor_available.
-    // It does not have a stable interface.
-    name: "libfstab",
-    vendor_available: true,
+    name: "libfs_mgr_file_wait",
+    defaults: ["fs_mgr_defaults"],
+    export_include_dirs: ["include"],
+    cflags: [
+        "-D_FILE_OFFSET_BITS=64",
+    ],
+    srcs: [
+        "file_wait.cpp",
+    ],
+    shared_libs: [
+        "libbase",
+    ],
+    host_supported: true,
     ramdisk_available: true,
     vendor_ramdisk_available: true,
     recovery_available: true,
-    apex_available: [
-        "//apex_available:anyapex",
-        "//apex_available:platform",
-    ],
-    host_supported: true,
-    defaults: ["fs_mgr_defaults"],
-    local_include_dirs: ["include/"],
-    srcs: [
-        "fs_mgr_fstab.cpp",
-        "fs_mgr_boot_config.cpp",
-        "fs_mgr_slotselect.cpp",
-    ],
-    target: {
-        darwin: {
-            enabled: false,
-        },
-        vendor: {
-            cflags: [
-                // Skipping entries in fstab should only be done in a system
-                // process as the config file is in /system_ext.
-                // Remove the op from the vendor variant.
-                "-DNO_SKIP_MOUNT",
-            ],
-        },
-    },
-    export_include_dirs: ["include_fstab"],
-    header_libs: [
-        "libbase_headers",
-        "libgsi_headers",
-    ],
-    min_sdk_version: "31",
 }
 
 cc_binary {
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index e568a9b..d55f8d3 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -2227,8 +2227,8 @@
 }
 
 bool fs_mgr_mount_overlayfs_fstab_entry(const FstabEntry& entry) {
-    auto overlayfs_valid_result = fs_mgr_overlayfs_valid();
-    if (overlayfs_valid_result == OverlayfsValidResult::kNotSupported) {
+    const auto overlayfs_check_result = android::fs_mgr::CheckOverlayfs();
+    if (!overlayfs_check_result.supported) {
         LERROR << __FUNCTION__ << "(): kernel does not support overlayfs";
         return false;
     }
@@ -2280,10 +2280,7 @@
         }
     }
 
-    auto options = "lowerdir=" + lowerdir;
-    if (overlayfs_valid_result == OverlayfsValidResult::kOverrideCredsRequired) {
-        options += ",override_creds=off";
-    }
+    const auto options = "lowerdir=" + lowerdir + overlayfs_check_result.mount_flags;
 
     // Use "overlay-" + entry.blk_device as the mount() source, so that adb-remout-test don't
     // confuse this with adb remount overlay, whose device name is "overlay".
@@ -2339,30 +2336,34 @@
     return context;
 }
 
-OverlayfsValidResult fs_mgr_overlayfs_valid() {
-    // Overlayfs available in the kernel, and patched for override_creds?
-    if (access("/sys/module/overlay/parameters/override_creds", F_OK) == 0) {
-        return OverlayfsValidResult::kOverrideCredsRequired;
-    }
+namespace android {
+namespace fs_mgr {
+
+OverlayfsCheckResult CheckOverlayfs() {
     if (!fs_mgr_filesystem_available("overlay")) {
-        return OverlayfsValidResult::kNotSupported;
+        return {.supported = false};
     }
     struct utsname uts;
     if (uname(&uts) == -1) {
-        return OverlayfsValidResult::kNotSupported;
+        return {.supported = false};
     }
     int major, minor;
     if (sscanf(uts.release, "%d.%d", &major, &minor) != 2) {
-        return OverlayfsValidResult::kNotSupported;
+        return {.supported = false};
     }
-    if (major < 4) {
-        return OverlayfsValidResult::kOk;
+    // Overlayfs available in the kernel, and patched for override_creds?
+    if (access("/sys/module/overlay/parameters/override_creds", F_OK) == 0) {
+        auto mount_flags = ",override_creds=off"s;
+        if (major > 5 || (major == 5 && minor >= 15)) {
+            mount_flags += ",userxattr"s;
+        }
+        return {.supported = true, .mount_flags = mount_flags};
     }
-    if (major > 4) {
-        return OverlayfsValidResult::kNotSupported;
+    if (major < 4 || (major == 4 && minor <= 3)) {
+        return {.supported = true};
     }
-    if (minor > 3) {
-        return OverlayfsValidResult::kNotSupported;
-    }
-    return OverlayfsValidResult::kOk;
+    return {.supported = false};
 }
+
+}  // namespace fs_mgr
+}  // namespace android
diff --git a/fs_mgr/fs_mgr_boot_config.cpp b/fs_mgr/fs_mgr_boot_config.cpp
deleted file mode 100644
index 75d1e0d..0000000
--- a/fs_mgr/fs_mgr_boot_config.cpp
+++ /dev/null
@@ -1,173 +0,0 @@
-/*
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <algorithm>
-#include <iterator>
-#include <string>
-#include <vector>
-
-#include <android-base/file.h>
-#include <android-base/stringprintf.h>
-#include <android-base/strings.h>
-#include <android-base/properties.h>
-
-#include "fs_mgr_priv.h"
-
-std::vector<std::pair<std::string, std::string>> fs_mgr_parse_cmdline(const std::string& cmdline) {
-    static constexpr char quote = '"';
-
-    std::vector<std::pair<std::string, std::string>> result;
-    size_t base = 0;
-    while (true) {
-        // skip quoted spans
-        auto found = base;
-        while (((found = cmdline.find_first_of(" \"", found)) != cmdline.npos) &&
-               (cmdline[found] == quote)) {
-            // unbalanced quote is ok
-            if ((found = cmdline.find(quote, found + 1)) == cmdline.npos) break;
-            ++found;
-        }
-        std::string piece;
-        auto source = cmdline.substr(base, found - base);
-        std::remove_copy(source.begin(), source.end(),
-                         std::back_insert_iterator<std::string>(piece), quote);
-        auto equal_sign = piece.find('=');
-        if (equal_sign == piece.npos) {
-            if (!piece.empty()) {
-                // no difference between <key> and <key>=
-                result.emplace_back(std::move(piece), "");
-            }
-        } else {
-            result.emplace_back(piece.substr(0, equal_sign), piece.substr(equal_sign + 1));
-        }
-        if (found == cmdline.npos) break;
-        base = found + 1;
-    }
-
-    return result;
-}
-
-std::vector<std::pair<std::string, std::string>> fs_mgr_parse_proc_bootconfig(
-        const std::string& cmdline) {
-    static constexpr char quote = '"';
-
-    std::vector<std::pair<std::string, std::string>> result;
-    for (auto& line : android::base::Split(cmdline, "\n")) {
-        line.erase(std::remove(line.begin(), line.end(), quote), line.end());
-        auto equal_sign = line.find('=');
-        if (equal_sign == line.npos) {
-            if (!line.empty()) {
-                // no difference between <key> and <key>=
-                result.emplace_back(std::move(line), "");
-            }
-        } else {
-            result.emplace_back(android::base::Trim(line.substr(0, equal_sign)),
-                                android::base::Trim(line.substr(equal_sign + 1)));
-        }
-    }
-
-    return result;
-}
-
-bool fs_mgr_get_boot_config_from_bootconfig(const std::string& bootconfig,
-                                            const std::string& android_key, std::string* out_val) {
-    FS_MGR_CHECK(out_val != nullptr);
-
-    const std::string bootconfig_key("androidboot." + android_key);
-    for (const auto& [key, value] : fs_mgr_parse_proc_bootconfig(bootconfig)) {
-        if (key == bootconfig_key) {
-            *out_val = value;
-            return true;
-        }
-    }
-
-    *out_val = "";
-    return false;
-}
-
-bool fs_mgr_get_boot_config_from_kernel(const std::string& cmdline, const std::string& android_key,
-                                        std::string* out_val) {
-    FS_MGR_CHECK(out_val != nullptr);
-
-    const std::string cmdline_key("androidboot." + android_key);
-    for (const auto& [key, value] : fs_mgr_parse_cmdline(cmdline)) {
-        if (key == cmdline_key) {
-            *out_val = value;
-            return true;
-        }
-    }
-
-    *out_val = "";
-    return false;
-}
-
-// Tries to get the given boot config value from bootconfig.
-// Returns true if successfully found, false otherwise.
-bool fs_mgr_get_boot_config_from_bootconfig_source(const std::string& key, std::string* out_val) {
-    std::string bootconfig;
-    if (!android::base::ReadFileToString("/proc/bootconfig", &bootconfig)) return false;
-    if (!bootconfig.empty() && bootconfig.back() == '\n') {
-        bootconfig.pop_back();
-    }
-    return fs_mgr_get_boot_config_from_bootconfig(bootconfig, key, out_val);
-}
-
-// Tries to get the given boot config value from kernel cmdline.
-// Returns true if successfully found, false otherwise.
-bool fs_mgr_get_boot_config_from_kernel_cmdline(const std::string& key, std::string* out_val) {
-    std::string cmdline;
-    if (!android::base::ReadFileToString("/proc/cmdline", &cmdline)) return false;
-    if (!cmdline.empty() && cmdline.back() == '\n') {
-        cmdline.pop_back();
-    }
-    return fs_mgr_get_boot_config_from_kernel(cmdline, key, out_val);
-}
-
-// Tries to get the boot config value in device tree, properties and
-// kernel cmdline (in that order).  Returns 'true' if successfully
-// found, 'false' otherwise.
-bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) {
-    FS_MGR_CHECK(out_val != nullptr);
-
-    // firstly, check the device tree
-    if (is_dt_compatible()) {
-        std::string file_name = get_android_dt_dir() + "/" + key;
-        if (android::base::ReadFileToString(file_name, out_val)) {
-            if (!out_val->empty()) {
-                out_val->pop_back();  // Trims the trailing '\0' out.
-                return true;
-            }
-        }
-    }
-
-    // next, check if we have "ro.boot" property already
-    *out_val = android::base::GetProperty("ro.boot." + key, "");
-    if (!out_val->empty()) {
-        return true;
-    }
-
-    // next, check if we have the property in bootconfig
-    if (fs_mgr_get_boot_config_from_bootconfig_source(key, out_val)) {
-        return true;
-    }
-
-    // finally, fallback to kernel cmdline, properties may not be ready yet
-    if (fs_mgr_get_boot_config_from_kernel_cmdline(key, out_val)) {
-        return true;
-    }
-
-    return false;
-}
diff --git a/fs_mgr/fs_mgr_overlayfs_control.cpp b/fs_mgr/fs_mgr_overlayfs_control.cpp
index 69a2ac0..68576f2 100644
--- a/fs_mgr/fs_mgr_overlayfs_control.cpp
+++ b/fs_mgr/fs_mgr_overlayfs_control.cpp
@@ -18,17 +18,10 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/fs.h>
-#include <selinux/selinux.h>
-#include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
-#include <sys/mount.h>
-#include <sys/param.h>
 #include <sys/stat.h>
 #include <sys/statvfs.h>
 #include <sys/types.h>
-#include <sys/utsname.h>
-#include <sys/vfs.h>
 #include <unistd.h>
 
 #include <algorithm>
@@ -38,13 +31,9 @@
 #include <vector>
 
 #include <android-base/file.h>
-#include <android-base/macros.h>
 #include <android-base/properties.h>
 #include <android-base/strings.h>
-#include <android-base/unique_fd.h>
-#include <ext4_utils/ext4_utils.h>
 #include <fs_mgr.h>
-#include <fs_mgr/file_wait.h>
 #include <fs_mgr_dm_linear.h>
 #include <fs_mgr_overlayfs.h>
 #include <fstab/fstab.h>
@@ -71,22 +60,25 @@
 
 constexpr char kDataScratchSizeMbProp[] = "fs_mgr.overlayfs.data_scratch_size_mb";
 
+constexpr char kPhysicalDevice[] = "/dev/block/by-name/";
+constexpr char kScratchImageMetadata[] = "/metadata/gsi/remount/lp_metadata";
+
+constexpr char kMkF2fs[] = "/system/bin/make_f2fs";
+constexpr char kMkExt4[] = "/system/bin/mke2fs";
+
 // Return true if everything is mounted, but before adb is started.  Right
 // after 'trigger load_persist_props_action' is done.
 static bool fs_mgr_boot_completed() {
     return android::base::GetBoolProperty("ro.persistent_properties.ready", false);
 }
 
-constexpr auto kPhysicalDevice = "/dev/block/by-name/";
-constexpr char kScratchImageMetadata[] = "/metadata/gsi/remount/lp_metadata";
-
 // Note: this is meant only for recovery/first-stage init.
 static bool ScratchIsOnData() {
     // The scratch partition of DSU is managed by gsid.
     if (fs_mgr_is_dsu_running()) {
         return false;
     }
-    return fs_mgr_access(kScratchImageMetadata);
+    return access(kScratchImageMetadata, F_OK) == 0;
 }
 
 static bool fs_mgr_rm_all(const std::string& path, bool* change = nullptr, int level = 0) {
@@ -131,7 +123,7 @@
 }
 
 std::string fs_mgr_overlayfs_setup_dir(const std::string& dir) {
-    auto top = dir + kOverlayTopDir;
+    auto top = dir + "/" + kOverlayTopDir;
 
     AutoSetFsCreateCon createcon(kOverlayfsFileContext);
     if (!createcon.Ok()) {
@@ -195,10 +187,6 @@
     return SlotNumberForSlotSuffix(fs_mgr_get_slot_suffix());
 }
 
-static std::string fs_mgr_overlayfs_super_device(uint32_t slot_number) {
-    return kPhysicalDevice + fs_mgr_get_super_partition_name(slot_number);
-}
-
 static bool fs_mgr_overlayfs_has_logical(const Fstab& fstab) {
     for (const auto& entry : fstab) {
         if (entry.fs_mgr_flags.logical) {
@@ -258,8 +246,8 @@
     }
 
     auto slot_number = fs_mgr_overlayfs_slot_number();
-    auto super_device = fs_mgr_overlayfs_super_device(slot_number);
-    if (!fs_mgr_rw_access(super_device)) {
+    const auto super_device = kPhysicalDevice + fs_mgr_get_super_partition_name();
+    if (access(super_device.c_str(), R_OK | W_OK)) {
         return OverlayfsTeardownResult::Ok;
     }
 
@@ -290,9 +278,9 @@
 
 bool fs_mgr_overlayfs_teardown_one(const std::string& overlay, const std::string& mount_point,
                                    bool* change, bool* should_destroy_scratch = nullptr) {
-    const auto top = overlay + kOverlayTopDir;
+    const auto top = overlay + "/" + kOverlayTopDir;
 
-    if (!fs_mgr_access(top)) {
+    if (access(top.c_str(), F_OK)) {
         if (should_destroy_scratch) *should_destroy_scratch = true;
         return true;
     }
@@ -300,7 +288,7 @@
     auto cleanup_all = mount_point.empty();
     const auto partition_name = android::base::Basename(mount_point);
     const auto oldpath = top + (cleanup_all ? "" : ("/" + partition_name));
-    const auto newpath = cleanup_all ? overlay + "/." + (kOverlayTopDir + 1) + ".teardown"
+    const auto newpath = cleanup_all ? overlay + "/." + kOverlayTopDir + ".teardown"
                                      : top + "/." + partition_name + ".teardown";
     auto ret = fs_mgr_rm_all(newpath);
     if (!rename(oldpath.c_str(), newpath.c_str())) {
@@ -346,72 +334,6 @@
     return ret;
 }
 
-// Mount kScratchMountPoint
-bool MountScratch(const std::string& device_path, bool readonly = false) {
-    if (readonly) {
-        if (!fs_mgr_access(device_path)) {
-            LOG(ERROR) << "Path does not exist: " << device_path;
-            return false;
-        }
-    } else if (!fs_mgr_rw_access(device_path)) {
-        LOG(ERROR) << "Path does not exist or is not readwrite: " << device_path;
-        return false;
-    }
-
-    std::vector<const char*> filesystem_candidates;
-    if (fs_mgr_is_f2fs(device_path)) {
-        filesystem_candidates = {"f2fs", "ext4"};
-    } else if (fs_mgr_is_ext4(device_path)) {
-        filesystem_candidates = {"ext4", "f2fs"};
-    } else {
-        LOG(ERROR) << "Scratch partition is not f2fs or ext4";
-        return false;
-    }
-
-    AutoSetFsCreateCon createcon(kOverlayfsFileContext);
-    if (!createcon.Ok()) {
-        return false;
-    }
-    if (mkdir(kScratchMountPoint, 0755) && (errno != EEXIST)) {
-        PERROR << "create " << kScratchMountPoint;
-        return false;
-    }
-
-    FstabEntry entry;
-    entry.blk_device = device_path;
-    entry.mount_point = kScratchMountPoint;
-    entry.flags = MS_NOATIME | MS_RDONLY;
-    if (!readonly) {
-        entry.flags &= ~MS_RDONLY;
-        entry.flags |= MS_SYNCHRONOUS;
-        entry.fs_options = "nodiscard";
-        fs_mgr_set_blk_ro(device_path, false);
-    }
-    // check_fs requires apex runtime library
-    if (fs_mgr_overlayfs_already_mounted("/data", false)) {
-        entry.fs_mgr_flags.check = true;
-    }
-    bool mounted = false;
-    for (auto fs_type : filesystem_candidates) {
-        entry.fs_type = fs_type;
-        if (fs_mgr_do_mount_one(entry) == 0) {
-            mounted = true;
-            break;
-        }
-    }
-    if (!createcon.Restore()) {
-        return false;
-    }
-    if (!mounted) {
-        rmdir(kScratchMountPoint);
-        return false;
-    }
-    return true;
-}
-
-const std::string kMkF2fs("/system/bin/make_f2fs");
-const std::string kMkExt4("/system/bin/mke2fs");
-
 // Note: The scratch partition of DSU is managed by gsid, and should be initialized during
 // first-stage-mount. Just check if the DM device for DSU scratch partition is created or not.
 static std::string GetDsuScratchDevice() {
@@ -456,14 +378,14 @@
     // thus do not rely on fsck to correct problems that could creep in.
     auto fs_type = ""s;
     auto command = ""s;
-    if (!access(kMkF2fs.c_str(), X_OK) && fs_mgr_filesystem_available("f2fs")) {
+    if (!access(kMkF2fs, X_OK) && fs_mgr_filesystem_available("f2fs")) {
         fs_type = "f2fs";
-        command = kMkF2fs + " -w ";
+        command = kMkF2fs + " -w "s;
         command += std::to_string(getpagesize());
         command += " -f -d1 -l" + android::base::Basename(kScratchMountPoint);
-    } else if (!access(kMkExt4.c_str(), X_OK) && fs_mgr_filesystem_available("ext4")) {
+    } else if (!access(kMkExt4, X_OK) && fs_mgr_filesystem_available("ext4")) {
         fs_type = "ext4";
-        command = kMkExt4 + " -F -b 4096 -t ext4 -m 0 -O has_journal -M " + kScratchMountPoint;
+        command = kMkExt4 + " -F -b 4096 -t ext4 -m 0 -O has_journal -M "s + kScratchMountPoint;
     } else {
         LERROR << "No supported mkfs command or filesystem driver available, supported filesystems "
                   "are: f2fs, ext4";
@@ -506,7 +428,7 @@
 
     auto partition_create = !*partition_exists;
     auto slot_number = fs_mgr_overlayfs_slot_number();
-    auto super_device = fs_mgr_overlayfs_super_device(slot_number);
+    const auto super_device = kPhysicalDevice + fs_mgr_get_super_partition_name();
     auto builder = MetadataBuilder::New(super_device, slot_number);
     if (!builder) {
         LERROR << "open " << super_device << " metadata";
@@ -646,8 +568,8 @@
 
 static bool CanUseSuperPartition(const Fstab& fstab) {
     auto slot_number = fs_mgr_overlayfs_slot_number();
-    auto super_device = fs_mgr_overlayfs_super_device(slot_number);
-    if (!fs_mgr_rw_access(super_device) || !fs_mgr_overlayfs_has_logical(fstab)) {
+    const auto super_device = kPhysicalDevice + fs_mgr_get_super_partition_name();
+    if (access(super_device.c_str(), R_OK | W_OK) || !fs_mgr_overlayfs_has_logical(fstab)) {
         return false;
     }
     auto metadata = ReadMetadata(super_device, slot_number);
@@ -697,8 +619,8 @@
     // If the partition exists, assume first that it can be mounted.
     if (partition_exists) {
         if (MountScratch(scratch_device)) {
-            if (fs_mgr_access(std::string(kScratchMountPoint) + kOverlayTopDir) ||
-                fs_mgr_filesystem_has_space(kScratchMountPoint)) {
+            const auto top = kScratchMountPoint + "/"s + kOverlayTopDir;
+            if (access(top.c_str(), F_OK) == 0 || fs_mgr_filesystem_has_space(kScratchMountPoint)) {
                 return true;
             }
             // declare it useless, no overrides and no free space
@@ -717,32 +639,6 @@
     return MountScratch(scratch_device);
 }
 
-// NOTE: OverlayfsSetupAllowed() must be "stricter" than OverlayfsTeardownAllowed().
-// Setup is allowed only if teardown is also allowed.
-bool OverlayfsSetupAllowed(bool verbose = false) {
-    if (!kAllowOverlayfs) {
-        if (verbose) {
-            LOG(ERROR) << "Overlayfs remounts can only be used in debuggable builds";
-        }
-        return false;
-    }
-    // Check mandatory kernel patches.
-    if (fs_mgr_overlayfs_valid() == OverlayfsValidResult::kNotSupported) {
-        if (verbose) {
-            LOG(ERROR) << "Kernel does not support overlayfs";
-        }
-        return false;
-    }
-    // in recovery or fastbootd, not allowed!
-    if (fs_mgr_in_recovery()) {
-        if (verbose) {
-            LOG(ERROR) << "Unsupported overlayfs setup from recovery";
-        }
-        return false;
-    }
-    return true;
-}
-
 constexpr bool OverlayfsTeardownAllowed() {
     // Never allow on non-debuggable build.
     return kAllowOverlayfs;
@@ -844,7 +740,7 @@
     if (!info.device.empty()) {
         return {std::move(info)};
     }
-    if (!fs_mgr_in_recovery()) {
+    if (!InRecovery()) {
         return {};
     }
 
@@ -867,8 +763,7 @@
     }
 
     // Avoid uart spam by first checking for a scratch partition.
-    auto metadata_slot = fs_mgr_overlayfs_slot_number();
-    auto super_device = fs_mgr_overlayfs_super_device(metadata_slot);
+    const auto super_device = kPhysicalDevice + fs_mgr_get_super_partition_name();
     auto metadata = ReadCurrentMetadata(super_device);
     if (!metadata) {
         return {};
@@ -1030,7 +925,7 @@
     if (!OverlayfsTeardownAllowed()) {
         return;
     }
-    if (!fs_mgr_in_recovery()) {
+    if (!InRecovery()) {
         LERROR << __FUNCTION__ << "(): must be called within recovery.";
         return;
     }
diff --git a/fs_mgr/fs_mgr_overlayfs_control.h b/fs_mgr/fs_mgr_overlayfs_control.h
index 50e83e8..b175101 100644
--- a/fs_mgr/fs_mgr_overlayfs_control.h
+++ b/fs_mgr/fs_mgr_overlayfs_control.h
@@ -14,8 +14,6 @@
 
 #pragma once
 
-#include <string>
-
 #include <fstab/fstab.h>
 
 // If "mount_point" is non-null, set up exactly one overlay.
diff --git a/fs_mgr/fs_mgr_overlayfs_mount.cpp b/fs_mgr/fs_mgr_overlayfs_mount.cpp
index c057c2b..8fb63b1 100644
--- a/fs_mgr/fs_mgr_overlayfs_mount.cpp
+++ b/fs_mgr/fs_mgr_overlayfs_mount.cpp
@@ -14,26 +14,20 @@
  * limitations under the License.
  */
 
-#include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/fs.h>
 #include <selinux/selinux.h>
-#include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 #include <sys/mount.h>
-#include <sys/param.h>
 #include <sys/stat.h>
 #include <sys/statvfs.h>
 #include <sys/types.h>
-#include <sys/utsname.h>
 #include <sys/vfs.h>
 #include <unistd.h>
 
 #include <algorithm>
 #include <memory>
-#include <optional>
 #include <string>
 #include <vector>
 
@@ -45,7 +39,6 @@
 #include <ext4_utils/ext4_utils.h>
 #include <fs_mgr.h>
 #include <fs_mgr/file_wait.h>
-#include <fs_mgr_dm_linear.h>
 #include <fs_mgr_overlayfs.h>
 #include <fstab/fstab.h>
 #include <libdm/dm.h>
@@ -62,39 +55,21 @@
 
 constexpr char kPreferCacheBackingStorageProp[] = "fs_mgr.overlayfs.prefer_cache_backing_storage";
 
-bool fs_mgr_access(const std::string& path) {
-    return access(path.c_str(), F_OK) == 0;
-}
+constexpr char kCacheMountPoint[] = "/cache";
+constexpr char kPhysicalDevice[] = "/dev/block/by-name/";
 
-const auto kLowerdirOption = "lowerdir=";
-const auto kUpperdirOption = "upperdir=";
-
-bool fs_mgr_in_recovery() {
-    // Check the existence of recovery binary instead of using the compile time
-    // __ANDROID_RECOVERY__ macro.
-    // If BOARD_USES_RECOVERY_AS_BOOT is true, both normal and recovery boot
-    // mode would use the same init binary, which would mean during normal boot
-    // the '/init' binary is actually a symlink pointing to
-    // init_second_stage.recovery, which would be compiled with
-    // __ANDROID_RECOVERY__ defined.
-    return fs_mgr_access("/system/bin/recovery");
-}
+constexpr char kLowerdirOption[] = "lowerdir=";
+constexpr char kUpperdirOption[] = "upperdir=";
 
 bool fs_mgr_is_dsu_running() {
     // Since android::gsi::CanBootIntoGsi() or android::gsi::MarkSystemAsGsi() is
     // never called in recovery, the return value of android::gsi::IsGsiRunning()
     // is not well-defined. In this case, just return false as being in recovery
     // implies not running a DSU system.
-    if (fs_mgr_in_recovery()) return false;
+    if (InRecovery()) return false;
     return android::gsi::IsGsiRunning();
 }
 
-const auto kCacheMountPoint = "/cache";
-
-static bool IsABDevice() {
-    return !android::base::GetProperty("ro.boot.slot_suffix", "").empty();
-}
-
 std::vector<const std::string> OverlayMountPoints() {
     // Never fallback to legacy cache mount point if within a DSU system,
     // because running a DSU system implies the device supports dynamic
@@ -105,7 +80,8 @@
 
     // For non-A/B devices prefer cache backing storage if
     // kPreferCacheBackingStorageProp property set.
-    if (!IsABDevice() && android::base::GetBoolProperty(kPreferCacheBackingStorageProp, false) &&
+    if (fs_mgr_get_slot_suffix().empty() &&
+        android::base::GetBoolProperty(kPreferCacheBackingStorageProp, false) &&
         android::base::GetIntProperty("ro.vendor.api_level", -1) < __ANDROID_API_T__) {
         return {kCacheMountPoint, kScratchMountPoint};
     }
@@ -118,11 +94,6 @@
     return !stat(path.c_str(), &st) && S_ISDIR(st.st_mode);
 }
 
-bool fs_mgr_rw_access(const std::string& path) {
-    if (path.empty()) return false;
-    return access(path.c_str(), R_OK | W_OK) == 0;
-}
-
 // At less than 1% or 8MB of free space return value of false,
 // means we will try to wrap with overlayfs.
 bool fs_mgr_filesystem_has_space(const std::string& mount_point) {
@@ -141,13 +112,11 @@
            (static_cast<uint64_t>(vst.f_bfree) * vst.f_frsize) >= kSizeThreshold;
 }
 
-const auto kPhysicalDevice = "/dev/block/by-name/";
-
 static bool fs_mgr_update_blk_device(FstabEntry* entry) {
     if (entry->fs_mgr_flags.logical) {
         fs_mgr_update_logical_partition(entry);
     }
-    if (fs_mgr_access(entry->blk_device)) {
+    if (access(entry->blk_device.c_str(), F_OK) == 0) {
         return true;
     }
     if (entry->blk_device != "/dev/root") {
@@ -155,10 +124,10 @@
     }
 
     // special case for system-as-root (taimen and others)
-    auto blk_device = std::string(kPhysicalDevice) + "system";
-    if (!fs_mgr_access(blk_device)) {
+    auto blk_device = kPhysicalDevice + "system"s;
+    if (access(blk_device.c_str(), F_OK)) {
         blk_device += fs_mgr_get_slot_suffix();
-        if (!fs_mgr_access(blk_device)) {
+        if (access(blk_device.c_str(), F_OK)) {
             return false;
         }
     }
@@ -237,28 +206,17 @@
     if (!fs_mgr_is_dir(mount_point)) return "";
     const auto base = android::base::Basename(mount_point) + "/";
     for (const auto& overlay_mount_point : OverlayMountPoints()) {
-        auto dir = overlay_mount_point + kOverlayTopDir + "/" + base;
+        auto dir = overlay_mount_point + "/" + kOverlayTopDir + "/" + base;
         auto upper = dir + kUpperName;
         if (!fs_mgr_is_dir(upper)) continue;
         auto work = dir + kWorkName;
         if (!fs_mgr_is_dir(work)) continue;
-        if (!fs_mgr_rw_access(work)) continue;
+        if (access(work.c_str(), R_OK | W_OK)) continue;
         return dir;
     }
     return "";
 }
 
-static inline bool KernelSupportsUserXattrs() {
-    struct utsname uts;
-    uname(&uts);
-
-    int major, minor;
-    if (sscanf(uts.release, "%d.%d", &major, &minor) != 2) {
-        return false;
-    }
-    return major > 5 || (major == 5 && minor >= 15);
-}
-
 const std::string fs_mgr_mount_point(const std::string& mount_point) {
     if ("/"s != mount_point) return mount_point;
     return "/system";
@@ -270,13 +228,7 @@
     auto candidate = fs_mgr_get_overlayfs_candidate(mount_point);
     if (candidate.empty()) return "";
     auto ret = kLowerdirOption + mount_point + "," + kUpperdirOption + candidate + kUpperName +
-               ",workdir=" + candidate + kWorkName;
-    if (fs_mgr_overlayfs_valid() == OverlayfsValidResult::kOverrideCredsRequired) {
-        ret += ",override_creds=off";
-    }
-    if (KernelSupportsUserXattrs()) {
-        ret += ",userxattr";
-    }
+               ",workdir=" + candidate + kWorkName + android::fs_mgr::CheckOverlayfs().mount_flags;
     for (const auto& flag : android::base::Split(entry.fs_options, ",")) {
         if (android::base::StartsWith(flag, "context=")) {
             ret += "," + flag;
@@ -527,13 +479,13 @@
 }
 
 // Mount kScratchMountPoint
-static bool MountScratch(const std::string& device_path, bool readonly = false) {
+bool MountScratch(const std::string& device_path, bool readonly) {
     if (readonly) {
-        if (!fs_mgr_access(device_path)) {
+        if (access(device_path.c_str(), F_OK)) {
             LOG(ERROR) << "Path does not exist: " << device_path;
             return false;
         }
-    } else if (!fs_mgr_rw_access(device_path)) {
+    } else if (access(device_path.c_str(), R_OK | W_OK)) {
         LOG(ERROR) << "Path does not exist or is not readwrite: " << device_path;
         return false;
     }
@@ -589,9 +541,6 @@
     return true;
 }
 
-const std::string kMkF2fs("/system/bin/make_f2fs");
-const std::string kMkExt4("/system/bin/mke2fs");
-
 // Note: The scratch partition of DSU is managed by gsid, and should be initialized during
 // first-stage-mount. Just check if the DM device for DSU scratch partition is created or not.
 static std::string GetDsuScratchDevice() {
@@ -633,7 +582,7 @@
 
 // NOTE: OverlayfsSetupAllowed() must be "stricter" than OverlayfsTeardownAllowed().
 // Setup is allowed only if teardown is also allowed.
-bool OverlayfsSetupAllowed(bool verbose = false) {
+bool OverlayfsSetupAllowed(bool verbose) {
     if (!kAllowOverlayfs) {
         if (verbose) {
             LOG(ERROR) << "Overlayfs remounts can only be used in debuggable builds";
@@ -641,14 +590,14 @@
         return false;
     }
     // Check mandatory kernel patches.
-    if (fs_mgr_overlayfs_valid() == OverlayfsValidResult::kNotSupported) {
+    if (!android::fs_mgr::CheckOverlayfs().supported) {
         if (verbose) {
             LOG(ERROR) << "Kernel does not support overlayfs";
         }
         return false;
     }
     // in recovery or fastbootd, not allowed!
-    if (fs_mgr_in_recovery()) {
+    if (InRecovery()) {
         if (verbose) {
             LOG(ERROR) << "Unsupported overlayfs setup from recovery";
         }
@@ -728,7 +677,7 @@
     // if verity is still disabled, i.e. no reboot occurred), and skips calling
     // fs_mgr_overlayfs_mount_all().
     auto scratch_device = GetBootScratchDevice();
-    if (!fs_mgr_rw_access(scratch_device)) {
+    if (access(scratch_device.c_str(), R_OK | W_OK)) {
         return;
     }
     if (!WaitForFile(scratch_device, 10s)) {
@@ -737,7 +686,8 @@
     if (!MountScratch(scratch_device, true /* readonly */)) {
         return;
     }
-    auto has_overlayfs_dir = fs_mgr_access(std::string(kScratchMountPoint) + kOverlayTopDir);
+    const auto top = kScratchMountPoint + "/"s + kOverlayTopDir;
+    const bool has_overlayfs_dir = access(top.c_str(), F_OK) == 0;
     fs_mgr_overlayfs_umount_scratch();
     if (has_overlayfs_dir) {
         MountScratch(scratch_device);
diff --git a/fs_mgr/fs_mgr_overlayfs_mount.h b/fs_mgr/fs_mgr_overlayfs_mount.h
index ae3ea84..f0afac1 100644
--- a/fs_mgr/fs_mgr_overlayfs_mount.h
+++ b/fs_mgr/fs_mgr_overlayfs_mount.h
@@ -20,9 +20,12 @@
 
 #include <fstab/fstab.h>
 
-bool fs_mgr_overlayfs_already_mounted(const std::string& mount_point, bool overlay_only = true);
-bool fs_mgr_wants_overlayfs(android::fs_mgr::FstabEntry* entry);
-android::fs_mgr::Fstab fs_mgr_overlayfs_candidate_list(const android::fs_mgr::Fstab& fstab);
+constexpr char kOverlayfsFileContext[] = "u:object_r:overlayfs_file:s0";
+
+constexpr char kScratchMountPoint[] = "/mnt/scratch";
+constexpr char kOverlayTopDir[] = "overlay";
+constexpr char kUpperName[] = "upper";
+constexpr char kWorkName[] = "work";
 
 #if ALLOW_ADBD_DISABLE_VERITY
 constexpr bool kAllowOverlayfs = true;
@@ -45,18 +48,13 @@
     bool restored_ = false;
 };
 
-constexpr auto kScratchMountPoint = "/mnt/scratch";
-constexpr char kOverlayfsFileContext[] = "u:object_r:overlayfs_file:s0";
-
-constexpr auto kUpperName = "upper";
-constexpr auto kWorkName = "work";
-constexpr auto kOverlayTopDir = "/overlay";
-
 bool fs_mgr_is_dsu_running();
-bool fs_mgr_in_recovery();
-bool fs_mgr_access(const std::string& path);
-bool fs_mgr_rw_access(const std::string& path);
 bool fs_mgr_filesystem_has_space(const std::string& mount_point);
 const std::string fs_mgr_mount_point(const std::string& mount_point);
+bool OverlayfsSetupAllowed(bool verbose = false);
+bool MountScratch(const std::string& device_path, bool readonly = false);
 bool fs_mgr_overlayfs_umount_scratch();
 std::vector<const std::string> OverlayMountPoints();
+bool fs_mgr_overlayfs_already_mounted(const std::string& mount_point, bool overlay_only = true);
+bool fs_mgr_wants_overlayfs(android::fs_mgr::FstabEntry* entry);
+android::fs_mgr::Fstab fs_mgr_overlayfs_candidate_list(const android::fs_mgr::Fstab& fstab);
diff --git a/fs_mgr/fs_mgr_priv.h b/fs_mgr/fs_mgr_priv.h
index 46cdb62..7e4d5e5 100644
--- a/fs_mgr/fs_mgr_priv.h
+++ b/fs_mgr/fs_mgr_priv.h
@@ -23,15 +23,7 @@
 #include <fs_mgr.h>
 #include <fstab/fstab.h>
 
-#include "fs_mgr_priv_boot_config.h"
-
-/* The CHECK() in logging.h will use program invocation name as the tag.
- * Thus, the log will have prefix "init: " when libfs_mgr is statically
- * linked in the init process. This might be opaque when debugging.
- * Appends "in libfs_mgr" at the end of the abort message to explicitly
- * indicate the check happens in fs_mgr.
- */
-#define FS_MGR_CHECK(x) CHECK(x) << "in libfs_mgr "
+#include "libfstab/fstab_priv.h"
 
 #define FS_MGR_TAG "[libfs_mgr] "
 
@@ -89,28 +81,25 @@
 using namespace std::chrono_literals;
 
 bool fs_mgr_set_blk_ro(const std::string& blockdev, bool readonly = true);
-bool fs_mgr_update_for_slotselect(android::fs_mgr::Fstab* fstab);
 bool fs_mgr_is_device_unlocked();
-const std::string& get_android_dt_dir();
-bool is_dt_compatible();
 
 bool fs_mgr_is_ext4(const std::string& blk_device);
 bool fs_mgr_is_f2fs(const std::string& blk_device);
 
-bool fs_mgr_teardown_verity(android::fs_mgr::FstabEntry* fstab);
-
 bool fs_mgr_filesystem_available(const std::string& filesystem);
 std::string fs_mgr_get_context(const std::string& mount_point);
 
-enum class OverlayfsValidResult {
-    kNotSupported = 0,
-    kOk,
-    kOverrideCredsRequired,
-};
-OverlayfsValidResult fs_mgr_overlayfs_valid();
-
 namespace android {
 namespace fs_mgr {
+
 bool UnmapDevice(const std::string& name);
+
+struct OverlayfsCheckResult {
+    bool supported;
+    std::string mount_flags;
+};
+
+OverlayfsCheckResult CheckOverlayfs();
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/fs_mgr_priv_boot_config.h b/fs_mgr/fs_mgr_priv_boot_config.h
deleted file mode 100644
index 6a38401..0000000
--- a/fs_mgr/fs_mgr_priv_boot_config.h
+++ /dev/null
@@ -1,37 +0,0 @@
-/*
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef __CORE_FS_MGR_PRIV_BOOTCONFIG_H
-#define __CORE_FS_MGR_PRIV_BOOTCONFIG_H
-
-#include <sys/cdefs.h>
-#include <string>
-#include <utility>
-#include <vector>
-
-std::vector<std::pair<std::string, std::string>> fs_mgr_parse_cmdline(const std::string& cmdline);
-
-bool fs_mgr_get_boot_config_from_kernel(const std::string& cmdline, const std::string& key,
-                                        std::string* out_val);
-bool fs_mgr_get_boot_config_from_kernel_cmdline(const std::string& key, std::string* out_val);
-bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val);
-std::vector<std::pair<std::string, std::string>> fs_mgr_parse_proc_bootconfig(
-        const std::string& bootconfig);
-bool fs_mgr_get_boot_config_from_bootconfig(const std::string& bootconfig, const std::string& key,
-                                            std::string* out_val);
-bool fs_mgr_get_boot_config_from_bootconfig_source(const std::string& key, std::string* out_val);
-
-#endif /* __CORE_FS_MGR_PRIV_BOOTCONFIG_H */
diff --git a/fs_mgr/fs_mgr_remount.cpp b/fs_mgr/fs_mgr_remount.cpp
index 4c45828..4b3a5d3 100644
--- a/fs_mgr/fs_mgr_remount.cpp
+++ b/fs_mgr/fs_mgr_remount.cpp
@@ -128,12 +128,11 @@
 }
 
 static android::sp<android::os::IVold> GetVold() {
+    auto sm = android::defaultServiceManager();
     while (true) {
-        if (auto sm = android::defaultServiceManager()) {
-            if (auto binder = sm->getService(android::String16("vold"))) {
-                if (auto vold = android::interface_cast<android::os::IVold>(binder)) {
-                    return vold;
-                }
+        if (auto binder = sm->checkService(android::String16("vold"))) {
+            if (auto vold = android::interface_cast<android::os::IVold>(binder)) {
+                return vold;
             }
         }
         std::this_thread::sleep_for(2s);
diff --git a/fs_mgr/fs_mgr_vendor_overlay.cpp b/fs_mgr/fs_mgr_vendor_overlay.cpp
index 6b32b4d..bacfa4b 100644
--- a/fs_mgr/fs_mgr_vendor_overlay.cpp
+++ b/fs_mgr/fs_mgr_vendor_overlay.cpp
@@ -85,10 +85,8 @@
         return false;
     }
 
-    auto options = kLowerdirOption + source_directory + ":" + vendor_mount_point;
-    if (fs_mgr_overlayfs_valid() == OverlayfsValidResult::kOverrideCredsRequired) {
-        options += ",override_creds=off";
-    }
+    const auto options = kLowerdirOption + source_directory + ":" + vendor_mount_point +
+                         android::fs_mgr::CheckOverlayfs().mount_flags;
     auto report = "__mount(source=overlay,target="s + vendor_mount_point + ",type=overlay," +
                   options + ")=";
     auto ret = mount("overlay", vendor_mount_point.c_str(), "overlay", MS_RDONLY | MS_NOATIME,
@@ -120,7 +118,7 @@
 
     const auto vendor_overlay_dirs = fs_mgr_get_vendor_overlay_dirs(vndk_version);
     if (vendor_overlay_dirs.empty()) return true;
-    if (fs_mgr_overlayfs_valid() == OverlayfsValidResult::kNotSupported) {
+    if (!android::fs_mgr::CheckOverlayfs().supported) {
         LINFO << "vendor overlay: kernel does not support overlayfs";
         return false;
     }
diff --git a/fs_mgr/include_fstab b/fs_mgr/include_fstab
new file mode 120000
index 0000000..728737f
--- /dev/null
+++ b/fs_mgr/include_fstab
@@ -0,0 +1 @@
+libfstab/include
\ No newline at end of file
diff --git a/fs_mgr/libfiemap/Android.bp b/fs_mgr/libfiemap/Android.bp
index ddda648..c8d5756 100644
--- a/fs_mgr/libfiemap/Android.bp
+++ b/fs_mgr/libfiemap/Android.bp
@@ -24,6 +24,7 @@
     vendor_ramdisk_available: true,
     recovery_available: true,
     export_include_dirs: ["include"],
+    host_supported: true,
 }
 
 filegroup {
diff --git a/fs_mgr/libfiemap/fiemap_writer_test.cpp b/fs_mgr/libfiemap/fiemap_writer_test.cpp
index bd97a78..c37329c 100644
--- a/fs_mgr/libfiemap/fiemap_writer_test.cpp
+++ b/fs_mgr/libfiemap/fiemap_writer_test.cpp
@@ -27,6 +27,7 @@
 #include <sys/vfs.h>
 #include <unistd.h>
 
+#include <cstring>
 #include <string>
 #include <utility>
 
@@ -518,7 +519,8 @@
         ASSERT_EQ(ret, 0);
 
         // mount the file system
-        ASSERT_EQ(mount(loop_dev.device().c_str(), mntpoint_.c_str(), "f2fs", 0, nullptr), 0);
+        ASSERT_EQ(mount(loop_dev.device().c_str(), mntpoint_.c_str(), "f2fs", 0, nullptr), 0)
+                << strerror(errno);
     }
 
     void TearDown() override {
diff --git a/fs_mgr/libfstab/Android.bp b/fs_mgr/libfstab/Android.bp
new file mode 100644
index 0000000..df0269c
--- /dev/null
+++ b/fs_mgr/libfstab/Android.bp
@@ -0,0 +1,62 @@
+//
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package {
+    default_applicable_licenses: [
+        "Android-Apache-2.0",
+        "system_core_fs_mgr_license",
+    ],
+}
+
+cc_library_static {
+    // Do not ever make this a shared library as long as it is vendor_available.
+    // It does not have a stable interface.
+    name: "libfstab",
+    vendor_available: true,
+    ramdisk_available: true,
+    vendor_ramdisk_available: true,
+    recovery_available: true,
+    host_supported: true,
+    defaults: ["fs_mgr_defaults"],
+    export_include_dirs: ["include"],
+    header_libs: [
+        "libbase_headers",
+        "libgsi_headers",
+    ],
+    srcs: [
+        "fstab.cpp",
+        "boot_config.cpp",
+        "slotselect.cpp",
+    ],
+    target: {
+        darwin: {
+            enabled: false,
+        },
+        vendor: {
+            cflags: [
+                // Skipping entries in fstab should only be done in a system
+                // process as the config file is in /system_ext.
+                // Remove the op from the vendor variant.
+                "-DNO_SKIP_MOUNT",
+            ],
+        },
+    },
+    apex_available: [
+        "//apex_available:anyapex",
+        "//apex_available:platform",
+    ],
+    min_sdk_version: "31",
+}
diff --git a/fs_mgr/libfstab/boot_config.cpp b/fs_mgr/libfstab/boot_config.cpp
new file mode 100644
index 0000000..b21495e
--- /dev/null
+++ b/fs_mgr/libfstab/boot_config.cpp
@@ -0,0 +1,205 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <algorithm>
+#include <iterator>
+#include <string>
+
+#include <android-base/file.h>
+#include <android-base/properties.h>
+#include <android-base/strings.h>
+
+#include "fstab_priv.h"
+#include "logging_macros.h"
+
+namespace android {
+namespace fs_mgr {
+
+const std::string& GetAndroidDtDir() {
+    // Set once and saves time for subsequent calls to this function
+    static const std::string kAndroidDtDir = [] {
+        std::string android_dt_dir;
+        if ((GetBootconfig("androidboot.android_dt_dir", &android_dt_dir) ||
+             GetKernelCmdline("androidboot.android_dt_dir", &android_dt_dir)) &&
+            !android_dt_dir.empty()) {
+            // Ensure the returned path ends with a /
+            if (android_dt_dir.back() != '/') {
+                android_dt_dir.push_back('/');
+            }
+        } else {
+            // Fall back to the standard procfs-based path
+            android_dt_dir = "/proc/device-tree/firmware/android/";
+        }
+        LINFO << "Using Android DT directory " << android_dt_dir;
+        return android_dt_dir;
+    }();
+    return kAndroidDtDir;
+}
+
+void ImportBootconfigFromString(const std::string& bootconfig,
+                                const std::function<void(std::string, std::string)>& fn) {
+    for (std::string_view line : android::base::Split(bootconfig, "\n")) {
+        const auto equal_pos = line.find('=');
+        std::string key = android::base::Trim(line.substr(0, equal_pos));
+        if (key.empty()) {
+            continue;
+        }
+        std::string value;
+        if (equal_pos != line.npos) {
+            value = android::base::Trim(line.substr(equal_pos + 1));
+            // If the value is a comma-delimited list, the kernel would insert a space between the
+            // list elements when read from /proc/bootconfig.
+            // BoardConfig.mk:
+            //      BOARD_BOOTCONFIG := key=value1,value2,value3
+            // /proc/bootconfig:
+            //      key = "value1", "value2", "value3"
+            if (key == "androidboot.boot_device" || key == "androidboot.boot_devices") {
+                // boot_device[s] is a special case where a list element can contain comma and the
+                // caller expects a space-delimited list, so don't remove space here.
+                value.erase(std::remove(value.begin(), value.end(), '"'), value.end());
+            } else {
+                // In order to not break the expectations of existing code, we modify the value to
+                // keep the format consistent with the kernel cmdline by removing quote and space.
+                std::string_view sv(value);
+                android::base::ConsumePrefix(&sv, "\"");
+                android::base::ConsumeSuffix(&sv, "\"");
+                value = android::base::StringReplace(sv, R"(", ")", ",", true);
+            }
+        }
+        // "key" and "key =" means empty value.
+        fn(std::move(key), std::move(value));
+    }
+}
+
+bool GetBootconfigFromString(const std::string& bootconfig, const std::string& key,
+                             std::string* out) {
+    bool found = false;
+    ImportBootconfigFromString(bootconfig, [&](std::string config_key, std::string value) {
+        if (!found && config_key == key) {
+            *out = std::move(value);
+            found = true;
+        }
+    });
+    return found;
+}
+
+void ImportBootconfig(const std::function<void(std::string, std::string)>& fn) {
+    std::string bootconfig;
+    android::base::ReadFileToString("/proc/bootconfig", &bootconfig);
+    ImportBootconfigFromString(bootconfig, fn);
+}
+
+bool GetBootconfig(const std::string& key, std::string* out) {
+    std::string bootconfig;
+    android::base::ReadFileToString("/proc/bootconfig", &bootconfig);
+    return GetBootconfigFromString(bootconfig, key, out);
+}
+
+void ImportKernelCmdlineFromString(const std::string& cmdline,
+                                   const std::function<void(std::string, std::string)>& fn) {
+    static constexpr char quote = '"';
+
+    size_t base = 0;
+    while (true) {
+        // skip quoted spans
+        auto found = base;
+        while (((found = cmdline.find_first_of(" \"", found)) != cmdline.npos) &&
+               (cmdline[found] == quote)) {
+            // unbalanced quote is ok
+            if ((found = cmdline.find(quote, found + 1)) == cmdline.npos) break;
+            ++found;
+        }
+        std::string piece = cmdline.substr(base, found - base);
+        piece.erase(std::remove(piece.begin(), piece.end(), quote), piece.end());
+        auto equal_sign = piece.find('=');
+        if (equal_sign == piece.npos) {
+            if (!piece.empty()) {
+                // no difference between <key> and <key>=
+                fn(std::move(piece), "");
+            }
+        } else {
+            std::string value = piece.substr(equal_sign + 1);
+            piece.resize(equal_sign);
+            fn(std::move(piece), std::move(value));
+        }
+        if (found == cmdline.npos) break;
+        base = found + 1;
+    }
+}
+
+bool GetKernelCmdlineFromString(const std::string& cmdline, const std::string& key,
+                                std::string* out) {
+    bool found = false;
+    ImportKernelCmdlineFromString(cmdline, [&](std::string config_key, std::string value) {
+        if (!found && config_key == key) {
+            *out = std::move(value);
+            found = true;
+        }
+    });
+    return found;
+}
+
+void ImportKernelCmdline(const std::function<void(std::string, std::string)>& fn) {
+    std::string cmdline;
+    android::base::ReadFileToString("/proc/cmdline", &cmdline);
+    ImportKernelCmdlineFromString(android::base::Trim(cmdline), fn);
+}
+
+bool GetKernelCmdline(const std::string& key, std::string* out) {
+    std::string cmdline;
+    android::base::ReadFileToString("/proc/cmdline", &cmdline);
+    return GetKernelCmdlineFromString(android::base::Trim(cmdline), key, out);
+}
+
+}  // namespace fs_mgr
+}  // namespace android
+
+// Tries to get the boot config value in device tree, properties, kernel bootconfig and kernel
+// cmdline (in that order).
+// Returns 'true' if successfully found, 'false' otherwise.
+bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) {
+    FSTAB_CHECK(out_val != nullptr);
+
+    // firstly, check the device tree
+    if (is_dt_compatible()) {
+        std::string file_name = android::fs_mgr::GetAndroidDtDir() + key;
+        if (android::base::ReadFileToString(file_name, out_val)) {
+            if (!out_val->empty()) {
+                out_val->pop_back();  // Trims the trailing '\0' out.
+                return true;
+            }
+        }
+    }
+
+    // next, check if we have "ro.boot" property already
+    *out_val = android::base::GetProperty("ro.boot." + key, "");
+    if (!out_val->empty()) {
+        return true;
+    }
+
+    // next, check if we have the property in bootconfig
+    const std::string config_key = "androidboot." + key;
+    if (android::fs_mgr::GetBootconfig(config_key, out_val)) {
+        return true;
+    }
+
+    // finally, fallback to kernel cmdline, properties may not be ready yet
+    if (android::fs_mgr::GetKernelCmdline(config_key, out_val)) {
+        return true;
+    }
+
+    return false;
+}
diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/libfstab/fstab.cpp
similarity index 91%
rename from fs_mgr/fs_mgr_fstab.cpp
rename to fs_mgr/libfstab/fstab.cpp
index c85e831..32460b1 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/libfstab/fstab.cpp
@@ -36,7 +36,8 @@
 #include <android-base/strings.h>
 #include <libgsi/libgsi.h>
 
-#include "fs_mgr_priv.h"
+#include "fstab_priv.h"
+#include "logging_macros.h"
 
 using android::base::EndsWith;
 using android::base::ParseByteCount;
@@ -50,11 +51,10 @@
 namespace fs_mgr {
 namespace {
 
-constexpr char kDefaultAndroidDtDir[] = "/proc/device-tree/firmware/android";
 constexpr char kProcMountsPath[] = "/proc/mounts";
 
 struct FlagList {
-    const char *name;
+    const char* name;
     uint64_t flag;
 };
 
@@ -80,7 +80,7 @@
 off64_t CalculateZramSize(int percentage) {
     off64_t total;
 
-    total  = sysconf(_SC_PHYS_PAGES);
+    total = sysconf(_SC_PHYS_PAGES);
     total *= percentage;
     total /= 100;
 
@@ -328,8 +328,7 @@
     // some recovery fstabs still contain the FDE options since they didn't do
     // anything in recovery mode anyway (except possibly to cause the
     // reservation of a crypto footer) and thus never got removed.
-    if (entry->fs_mgr_flags.crypt && !entry->fs_mgr_flags.vold_managed &&
-        access("/system/bin/recovery", F_OK) != 0) {
+    if (entry->fs_mgr_flags.crypt && !entry->fs_mgr_flags.vold_managed && !InRecovery()) {
         LERROR << "FDE is no longer supported; 'encryptable' can only be used for adoptable "
                   "storage";
         return false;
@@ -337,25 +336,14 @@
     return true;
 }
 
-std::string InitAndroidDtDir() {
-    std::string android_dt_dir;
-    // The platform may specify a custom Android DT path in kernel cmdline
-    if (!fs_mgr_get_boot_config_from_bootconfig_source("android_dt_dir", &android_dt_dir) &&
-        !fs_mgr_get_boot_config_from_kernel_cmdline("android_dt_dir", &android_dt_dir)) {
-        // Fall back to the standard procfs-based path
-        android_dt_dir = kDefaultAndroidDtDir;
-    }
-    return android_dt_dir;
-}
-
 bool IsDtFstabCompatible() {
     std::string dt_value;
-    std::string file_name = get_android_dt_dir() + "/fstab/compatible";
+    std::string file_name = GetAndroidDtDir() + "fstab/compatible";
 
     if (ReadDtFile(file_name, &dt_value) && dt_value == "android,fstab") {
         // If there's no status property or its set to "ok" or "okay", then we use the DT fstab.
         std::string status_value;
-        std::string status_file_name = get_android_dt_dir() + "/fstab/status";
+        std::string status_file_name = GetAndroidDtDir() + "fstab/status";
         return !ReadDtFile(status_file_name, &status_value) || status_value == "ok" ||
                status_value == "okay";
     }
@@ -368,7 +356,7 @@
         return {};
     }
 
-    std::string fstabdir_name = get_android_dt_dir() + "/fstab";
+    std::string fstabdir_name = GetAndroidDtDir() + "fstab";
     std::unique_ptr<DIR, int (*)(DIR*)> fstabdir(opendir(fstabdir_name.c_str()), closedir);
     if (!fstabdir) return {};
 
@@ -401,7 +389,7 @@
 
         std::string mount_point;
         file_name =
-            android::base::StringPrintf("%s/%s/mnt_point", fstabdir_name.c_str(), dp->d_name);
+                android::base::StringPrintf("%s/%s/mnt_point", fstabdir_name.c_str(), dp->d_name);
         if (ReadDtFile(file_name, &value)) {
             LINFO << "dt_fstab: Using a specified mount point " << value << " for " << dp->d_name;
             mount_point = value;
@@ -417,14 +405,16 @@
         }
         fstab_entry.push_back(value);
 
-        file_name = android::base::StringPrintf("%s/%s/mnt_flags", fstabdir_name.c_str(), dp->d_name);
+        file_name =
+                android::base::StringPrintf("%s/%s/mnt_flags", fstabdir_name.c_str(), dp->d_name);
         if (!ReadDtFile(file_name, &value)) {
             LERROR << "dt_fstab: Failed to find type for partition " << dp->d_name;
             return {};
         }
         fstab_entry.push_back(value);
 
-        file_name = android::base::StringPrintf("%s/%s/fsmgr_flags", fstabdir_name.c_str(), dp->d_name);
+        file_name =
+                android::base::StringPrintf("%s/%s/fsmgr_flags", fstabdir_name.c_str(), dp->d_name);
         if (!ReadDtFile(file_name, &value)) {
             LERROR << "dt_fstab: Failed to find type for partition " << dp->d_name;
             return {};
@@ -520,6 +510,9 @@
 // ramdisk's copy of the fstab had to be located in the root directory, but now
 // the system/etc directory is supported too and is the preferred location.
 std::string GetFstabPath() {
+    if (InRecovery()) {
+        return "/etc/recovery.fstab";
+    }
     for (const char* prop : {"fstab_suffix", "hardware", "hardware.platform"}) {
         std::string suffix;
 
@@ -835,19 +828,11 @@
     fstab->clear();
     ReadFstabFromDt(fstab, false /* verbose */);
 
-    std::string default_fstab_path;
-    // Use different fstab paths for normal boot and recovery boot, respectively
-    if ((access("/sbin/recovery", F_OK) == 0) || (access("/system/bin/recovery", F_OK) == 0)) {
-        default_fstab_path = "/etc/recovery.fstab";
-    } else {  // normal boot
-        default_fstab_path = GetFstabPath();
-    }
-
     Fstab default_fstab;
+    const std::string default_fstab_path = GetFstabPath();
     if (!default_fstab_path.empty() && ReadFstabFromFile(default_fstab_path, &default_fstab)) {
-        for (auto&& entry : default_fstab) {
-            fstab->emplace_back(std::move(entry));
-        }
+        fstab->insert(fstab->end(), std::make_move_iterator(default_fstab.begin()),
+                      std::make_move_iterator(default_fstab.end()));
     } else {
         LINFO << __FUNCTION__ << "(): failed to find device default fstab";
     }
@@ -877,40 +862,33 @@
 }
 
 std::set<std::string> GetBootDevices() {
+    std::set<std::string> boot_devices;
     // First check bootconfig, then kernel commandline, then the device tree
-    std::string dt_file_name = get_android_dt_dir() + "/boot_devices";
     std::string value;
-    if (fs_mgr_get_boot_config_from_bootconfig_source("boot_devices", &value) ||
-        fs_mgr_get_boot_config_from_bootconfig_source("boot_device", &value)) {
-        std::set<std::string> boot_devices;
-        // remove quotes and split by spaces
-        auto boot_device_strings = base::Split(base::StringReplace(value, "\"", "", true), " ");
-        for (std::string_view device : boot_device_strings) {
-            // trim the trailing comma, keep the rest.
+    if (GetBootconfig("androidboot.boot_devices", &value) ||
+        GetBootconfig("androidboot.boot_device", &value)) {
+        // split by spaces and trim the trailing comma.
+        for (std::string_view device : android::base::Split(value, " ")) {
             base::ConsumeSuffix(&device, ",");
             boot_devices.emplace(device);
         }
         return boot_devices;
     }
 
-    if (fs_mgr_get_boot_config_from_kernel_cmdline("boot_devices", &value) ||
-        ReadDtFile(dt_file_name, &value)) {
-        auto boot_devices = Split(value, ",");
-        return std::set<std::string>(boot_devices.begin(), boot_devices.end());
+    const std::string dt_file_name = GetAndroidDtDir() + "boot_devices";
+    if (GetKernelCmdline("androidboot.boot_devices", &value) || ReadDtFile(dt_file_name, &value)) {
+        auto boot_devices_list = Split(value, ",");
+        return {std::make_move_iterator(boot_devices_list.begin()),
+                std::make_move_iterator(boot_devices_list.end())};
     }
 
-    std::string cmdline;
-    if (android::base::ReadFileToString("/proc/cmdline", &cmdline)) {
-        std::set<std::string> boot_devices;
-        const std::string cmdline_key = "androidboot.boot_device";
-        for (const auto& [key, value] : fs_mgr_parse_cmdline(cmdline)) {
-            if (key == cmdline_key) {
-                boot_devices.emplace(value);
-            }
+    ImportKernelCmdline([&](std::string key, std::string value) {
+        if (key == "androidboot.boot_device") {
+            boot_devices.emplace(std::move(value));
         }
-        if (!boot_devices.empty()) {
-            return boot_devices;
-        }
+    });
+    if (!boot_devices.empty()) {
+        return boot_devices;
     }
 
     // Fallback to extract boot devices from fstab.
@@ -936,18 +914,22 @@
     return base_device + "-verity";
 }
 
+bool InRecovery() {
+    // Check the existence of recovery binary instead of using the compile time
+    // __ANDROID_RECOVERY__ macro.
+    // If BOARD_USES_RECOVERY_AS_BOOT is true, both normal and recovery boot
+    // mode would use the same init binary, which would mean during normal boot
+    // the '/init' binary is actually a symlink pointing to
+    // init_second_stage.recovery, which would be compiled with
+    // __ANDROID_RECOVERY__ defined.
+    return access("/system/bin/recovery", F_OK) == 0 || access("/sbin/recovery", F_OK) == 0;
+}
+
 }  // namespace fs_mgr
 }  // namespace android
 
-// FIXME: The same logic is duplicated in system/core/init/
-const std::string& get_android_dt_dir() {
-    // Set once and saves time for subsequent calls to this function
-    static const std::string kAndroidDtDir = android::fs_mgr::InitAndroidDtDir();
-    return kAndroidDtDir;
-}
-
 bool is_dt_compatible() {
-    std::string file_name = get_android_dt_dir() + "/compatible";
+    std::string file_name = android::fs_mgr::GetAndroidDtDir() + "compatible";
     std::string dt_value;
     if (android::fs_mgr::ReadDtFile(file_name, &dt_value)) {
         if (dt_value == "android,firmware") {
diff --git a/fs_mgr/libfstab/fstab_priv.h b/fs_mgr/libfstab/fstab_priv.h
new file mode 100644
index 0000000..5105da0
--- /dev/null
+++ b/fs_mgr/libfstab/fstab_priv.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <functional>
+#include <string>
+
+#include <fstab/fstab.h>
+
+// Do not include logging_macros.h here as this header is used by fs_mgr, too.
+
+bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val);
+
+bool fs_mgr_update_for_slotselect(android::fs_mgr::Fstab* fstab);
+bool is_dt_compatible();
+
+namespace android {
+namespace fs_mgr {
+
+bool InRecovery();
+bool ParseFstabFromString(const std::string& fstab_str, bool proc_mounts, Fstab* fstab_out);
+bool SkipMountWithConfig(const std::string& skip_config, Fstab* fstab, bool verbose);
+std::string GetFstabPath();
+
+void ImportBootconfigFromString(const std::string& bootconfig,
+                                const std::function<void(std::string, std::string)>& fn);
+
+bool GetBootconfigFromString(const std::string& bootconfig, const std::string& key,
+                             std::string* out);
+
+void ImportKernelCmdlineFromString(const std::string& cmdline,
+                                   const std::function<void(std::string, std::string)>& fn);
+
+bool GetKernelCmdlineFromString(const std::string& cmdline, const std::string& key,
+                                std::string* out);
+
+}  // namespace fs_mgr
+}  // namespace android
diff --git a/fs_mgr/fuzz/Android.bp b/fs_mgr/libfstab/fuzz/Android.bp
similarity index 100%
rename from fs_mgr/fuzz/Android.bp
rename to fs_mgr/libfstab/fuzz/Android.bp
diff --git a/fs_mgr/fuzz/fs_mgr_fstab_fuzzer.cpp b/fs_mgr/libfstab/fuzz/fs_mgr_fstab_fuzzer.cpp
similarity index 97%
rename from fs_mgr/fuzz/fs_mgr_fstab_fuzzer.cpp
rename to fs_mgr/libfstab/fuzz/fs_mgr_fstab_fuzzer.cpp
index b5fdad4..b09b273 100644
--- a/fs_mgr/fuzz/fs_mgr_fstab_fuzzer.cpp
+++ b/fs_mgr/libfstab/fuzz/fs_mgr_fstab_fuzzer.cpp
@@ -20,6 +20,8 @@
 #include <fstab/fstab.h>
 #include <fuzzer/FuzzedDataProvider.h>
 
+#include "../fstab_priv.h"
+
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
     FuzzedDataProvider fdp(data, size);
 
diff --git a/fs_mgr/fuzz/fstab.dict b/fs_mgr/libfstab/fuzz/fstab.dict
similarity index 100%
rename from fs_mgr/fuzz/fstab.dict
rename to fs_mgr/libfstab/fuzz/fstab.dict
diff --git a/fs_mgr/include_fstab/fstab/fstab.h b/fs_mgr/libfstab/include/fstab/fstab.h
similarity index 80%
rename from fs_mgr/include_fstab/fstab/fstab.h
rename to fs_mgr/libfstab/include/fstab/fstab.h
index 9cb1546..150a47d 100644
--- a/fs_mgr/include_fstab/fstab/fstab.h
+++ b/fs_mgr/libfstab/include/fstab/fstab.h
@@ -19,6 +19,7 @@
 #include <stdint.h>
 #include <sys/types.h>
 
+#include <functional>
 #include <set>
 #include <string>
 #include <vector>
@@ -93,13 +94,6 @@
 // Unless explicitly requested, a lookup on mount point should always return the 1st one.
 using Fstab = std::vector<FstabEntry>;
 
-// Exported for testability. Regular users should use ReadFstabFromFile().
-bool ParseFstabFromString(const std::string& fstab_str, bool proc_mounts, Fstab* fstab_out);
-// Exported for testability. Regular users should use ReadDefaultFstab().
-std::string GetFstabPath();
-// Exported for testability.
-bool SkipMountWithConfig(const std::string& skip_config, Fstab* fstab, bool verbose);
-
 bool ReadFstabFromFile(const std::string& path, Fstab* fstab);
 bool ReadFstabFromProcMounts(Fstab* fstab);
 bool ReadFstabFromDt(Fstab* fstab, bool verbose = true);
@@ -131,5 +125,25 @@
 // expected name.
 std::string GetVerityDeviceName(const FstabEntry& entry);
 
+// Returns the Android Device Tree directory as specified in the kernel bootconfig or cmdline.
+// If the platform does not configure a custom DT path, returns the standard one (based in procfs).
+const std::string& GetAndroidDtDir();
+
+// Import the kernel bootconfig by calling the callback |fn| with each key-value pair.
+void ImportBootconfig(const std::function<void(std::string, std::string)>& fn);
+
+// Get the kernel bootconfig value for |key|.
+// Returns true if |key| is found in bootconfig.
+// Otherwise returns false and |*out| is not modified.
+bool GetBootconfig(const std::string& key, std::string* out);
+
+// Import the kernel cmdline by calling the callback |fn| with each key-value pair.
+void ImportKernelCmdline(const std::function<void(std::string, std::string)>& fn);
+
+// Get the kernel cmdline value for |key|.
+// Returns true if |key| is found in the kernel cmdline.
+// Otherwise returns false and |*out| is not modified.
+bool GetKernelCmdline(const std::string& key, std::string* out);
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/libfstab/logging_macros.h b/fs_mgr/libfstab/logging_macros.h
new file mode 100644
index 0000000..7ea1b77
--- /dev/null
+++ b/fs_mgr/libfstab/logging_macros.h
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <android-base/logging.h>
+
+#define FSTAB_TAG "[libfstab] "
+
+/* The CHECK() in logging.h will use program invocation name as the tag.
+ * Thus, the log will have prefix "init: " when libfs_mgr is statically
+ * linked in the init process. This might be opaque when debugging.
+ * Append a library name tag at the end of the abort message to aid debugging.
+ */
+#define FSTAB_CHECK(x) CHECK(x) << "in " << FSTAB_TAG
+
+// Logs a message to kernel
+#define LINFO LOG(INFO) << FSTAB_TAG
+#define LWARNING LOG(WARNING) << FSTAB_TAG
+#define LERROR LOG(ERROR) << FSTAB_TAG
+#define LFATAL LOG(FATAL) << FSTAB_TAG
+
+// Logs a message with strerror(errno) at the end
+#define PINFO PLOG(INFO) << FSTAB_TAG
+#define PWARNING PLOG(WARNING) << FSTAB_TAG
+#define PERROR PLOG(ERROR) << FSTAB_TAG
+#define PFATAL PLOG(FATAL) << FSTAB_TAG
diff --git a/fs_mgr/fs_mgr_slotselect.cpp b/fs_mgr/libfstab/slotselect.cpp
similarity index 97%
rename from fs_mgr/fs_mgr_slotselect.cpp
rename to fs_mgr/libfstab/slotselect.cpp
index 09c1b7e..97b2ba1 100644
--- a/fs_mgr/fs_mgr_slotselect.cpp
+++ b/fs_mgr/libfstab/slotselect.cpp
@@ -18,8 +18,8 @@
 
 #include <string>
 
-#include "fs_mgr.h"
-#include "fs_mgr_priv.h"
+#include "fstab_priv.h"
+#include "logging_macros.h"
 
 // Realistically, this file should be part of the android::fs_mgr namespace;
 using namespace android::fs_mgr;
diff --git a/fs_mgr/liblp/super_layout_builder.cpp b/fs_mgr/liblp/super_layout_builder.cpp
index 37f28e1..5349e41 100644
--- a/fs_mgr/liblp/super_layout_builder.cpp
+++ b/fs_mgr/liblp/super_layout_builder.cpp
@@ -46,21 +46,21 @@
 bool SuperLayoutBuilder::Open(const LpMetadata& metadata) {
     for (const auto& partition : metadata.partitions) {
         if (partition.attributes & LP_PARTITION_ATTR_SLOT_SUFFIXED) {
-            // Retrofit devices are not supported.
+            LOG(ERROR) << "Retrofit devices are not supported";
             return false;
         }
         if (!(partition.attributes & LP_PARTITION_ATTR_READONLY)) {
-            // Writable partitions are not supported.
+            LOG(ERROR) << "Writable partitions are not supported";
             return false;
         }
     }
     if (!metadata.extents.empty()) {
-        // Partitions that already have extents are not supported (should
-        // never be true of super_empty.img).
+        LOG(ERROR) << "Partitions that already have extents are not supported";
+        // should never be true of super_empty.img.
         return false;
     }
     if (metadata.block_devices.size() != 1) {
-        // Only one "super" is supported.
+        LOG(ERROR) << "Only one 'super' is supported";
         return false;
     }
 
diff --git a/fs_mgr/libsnapshot/Android.bp b/fs_mgr/libsnapshot/Android.bp
index 8f35381..04b5a02 100644
--- a/fs_mgr/libsnapshot/Android.bp
+++ b/fs_mgr/libsnapshot/Android.bp
@@ -44,7 +44,7 @@
         "libext2_uuid",
         "libext4_utils",
         "libfstab",
-        "libsnapshot_snapuserd",
+        "libsnapuserd_client",
         "libz",
     ],
     header_libs: [
@@ -101,7 +101,7 @@
 }
 
 cc_library_static {
-    name: "libsnapshot",
+    name: "libsnapshot_static",
     defaults: [
         "libsnapshot_defaults",
         "libsnapshot_hal_deps",
@@ -112,6 +112,25 @@
     ],
 }
 
+cc_library {
+    name: "libsnapshot",
+    defaults: [
+        "libsnapshot_defaults",
+        "libsnapshot_cow_defaults",
+        "libsnapshot_hal_deps",
+    ],
+    srcs: [":libsnapshot_sources"],
+    shared_libs: [
+        "libfs_mgr_binder",
+        "liblp",
+        "libprotobuf-cpp-lite",
+    ],
+    static_libs: [
+        "libc++fs",
+        "libsnapshot_cow",
+    ]
+}
+
 cc_library_static {
     name: "libsnapshot_init",
     native_coverage : true,
@@ -247,7 +266,7 @@
         "libgsi",
         "libgmock",
         "liblp",
-        "libsnapshot",
+        "libsnapshot_static",
         "libsnapshot_cow",
         "libsnapshot_test_helpers",
         "libsparse",
@@ -330,8 +349,6 @@
         "libbrotli",
         "libc++fs",
         "libfstab",
-        "libsnapshot",
-        "libsnapshot_cow",
         "libz",
         "update_metadata-protos",
     ],
@@ -344,6 +361,7 @@
         "liblog",
         "liblp",
         "libprotobuf-cpp-lite",
+        "libsnapshot",
         "libstatslog",
         "libutils",
     ],
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
index 3a81f63..c9a4dee 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
@@ -161,6 +161,10 @@
     kCowCompressLz4 = 3,
     kCowCompressZstd = 4,
 };
+struct CowCompression {
+    CowCompressionAlgorithm algorithm = kCowCompressNone;
+    uint32_t compression_level = 0;
+};
 
 static constexpr uint8_t kCowReadAheadNotStarted = 0;
 static constexpr uint8_t kCowReadAheadInProgress = 1;
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
index df532ee..c056a19 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
@@ -624,7 +624,7 @@
     bool CollapseSnapshotDevice(LockedFile* lock, const std::string& name,
                                 const SnapshotStatus& status);
 
-    struct MergeResult {
+    struct [[nodiscard]] MergeResult {
         explicit MergeResult(UpdateState state,
                              MergeFailureCode failure_code = MergeFailureCode::Ok)
             : state(state), failure_code(failure_code) {}
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/cow_reader.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/cow_reader.cpp
index 489669a..f37aed1 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/cow_reader.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/cow_reader.cpp
@@ -310,9 +310,34 @@
 bool CowReader::VerifyMergeOps() {
     auto itr = GetMergeOpIter(true);
     std::unordered_map<uint64_t, const CowOperation*> overwritten_blocks;
+    bool non_ordered_op_found = false;
+
     while (!itr->AtEnd()) {
         const auto& op = itr->Get();
         uint64_t offset;
+
+        // Op should not be a metadata
+        if (IsMetadataOp(*op)) {
+            LOG(ERROR) << "Metadata op: " << op << " found during merge sequence";
+            return false;
+        }
+
+        // Sequence ops should contain all the ordered ops followed
+        // by Replace and Zero ops. If we find the first op which
+        // is not ordered, that means all ordered ops processing
+        // has been completed.
+        if (!IsOrderedOp(*op)) {
+            non_ordered_op_found = true;
+        }
+
+        // Since, all ordered ops processing has been completed,
+        // check that the subsequent ops are not ordered.
+        if (non_ordered_op_found && IsOrderedOp(*op)) {
+            LOG(ERROR) << "Invalid sequence - non-ordered and ordered ops"
+                       << " cannot be mixed during sequence generation";
+            return false;
+        }
+
         if (!GetSourceOffset(op, &offset)) {
             itr->Next();
             continue;
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/test_v2.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/test_v2.cpp
index 31b9a58..ab275d4 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/test_v2.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/test_v2.cpp
@@ -472,9 +472,10 @@
     if (strcmp(GetParam(), "none") == 0) {
         GTEST_SKIP();
     }
-
+    CowCompression compression;
     auto algorithm = CompressionAlgorithmFromString(GetParam());
     ASSERT_TRUE(algorithm.has_value());
+    compression.algorithm = algorithm.value();
 
     std::string expected = "The quick brown fox jumps over the lazy dog.";
     expected.resize(4096, '\0');
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
index c549969..cbd7569 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
@@ -124,7 +124,7 @@
         LOG(ERROR) << "unrecognized compression: " << options_.compression;
         return false;
     }
-    compression_ = *algorithm;
+    compression_.algorithm = *algorithm;
 
     if (options_.cluster_ops == 1) {
         LOG(ERROR) << "Clusters must contain at least two operations to function.";
@@ -165,7 +165,7 @@
         return;
     }
     for (int i = 0; i < num_compress_threads_; i++) {
-        auto wt = std::make_unique<CompressWorker>(compression_, header_.block_size);
+        auto wt = std::make_unique<CompressWorker>(compression_.algorithm, header_.block_size);
         threads_.emplace_back(std::async(std::launch::async, &CompressWorker::RunThread, wt.get()));
         compress_threads_.push_back(std::move(wt));
     }
@@ -320,8 +320,8 @@
     const uint8_t* iter = reinterpret_cast<const uint8_t*>(data);
     compressed_buf_.clear();
     if (num_threads <= 1) {
-        return CompressWorker::CompressBlocks(compression_, options_.block_size, data, num_blocks,
-                                              &compressed_buf_);
+        return CompressWorker::CompressBlocks(compression_.algorithm, options_.block_size, data,
+                                              num_blocks, &compressed_buf_);
     }
 
     // Submit the blocks per thread. The retrieval of
@@ -366,7 +366,7 @@
     while (num_blocks) {
         size_t pending_blocks = (std::min(kProcessingBlocks, num_blocks));
 
-        if (compression_ && num_compress_threads_ > 1) {
+        if (compression_.algorithm && num_compress_threads_ > 1) {
             if (!CompressBlocks(pending_blocks, iter)) {
                 return false;
             }
@@ -386,19 +386,19 @@
                 op.source = next_data_pos_;
             }
 
-            if (compression_) {
+            if (compression_.algorithm) {
                 auto data = [&, this]() {
                     if (num_compress_threads_ > 1) {
                         auto data = std::move(*buf_iter_);
                         buf_iter_++;
                         return data;
                     } else {
-                        auto data =
-                                CompressWorker::Compress(compression_, iter, header_.block_size);
+                        auto data = CompressWorker::Compress(compression_.algorithm, iter,
+                                                             header_.block_size);
                         return data;
                     }
                 }();
-                op.compression = compression_;
+                op.compression = compression_.algorithm;
                 op.data_length = static_cast<uint16_t>(data.size());
 
                 if (!WriteOperation(op, data.data(), data.size())) {
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
index 809ae57..1aa8518 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
@@ -63,7 +63,7 @@
 
   private:
     CowFooter footer_{};
-    CowCompressionAlgorithm compression_ = kCowCompressNone;
+    CowCompression compression_;
     uint64_t current_op_pos_ = 0;
     uint64_t next_op_pos_ = 0;
     uint64_t next_data_pos_ = 0;
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index 09d35cf..86ff5f7 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -1248,14 +1248,12 @@
            GetMetadataPartitionState(*current_metadata, name) == MetadataPartitionState::Updated);
 
     if (UpdateUsesUserSnapshots(lock)) {
-        std::string merge_status;
-        if (EnsureSnapuserdConnected()) {
-            // Query the snapshot status from the daemon
-            merge_status = snapuserd_client_->QuerySnapshotStatus(name);
-        } else {
-            MergeResult(UpdateState::MergeFailed, MergeFailureCode::QuerySnapshotStatus);
+        if (!EnsureSnapuserdConnected()) {
+            return MergeResult(UpdateState::MergeFailed, MergeFailureCode::QuerySnapshotStatus);
         }
 
+        // Query the snapshot status from the daemon
+        const auto merge_status = snapuserd_client_->QuerySnapshotStatus(name);
         if (merge_status == "snapshot-merge-failed") {
             return MergeResult(UpdateState::MergeFailed, MergeFailureCode::UnknownTargetType);
         }
diff --git a/fs_mgr/libsnapshot/snapuserd/Android.bp b/fs_mgr/libsnapshot/snapuserd/Android.bp
index a9b96e2..6548cc8 100644
--- a/fs_mgr/libsnapshot/snapuserd/Android.bp
+++ b/fs_mgr/libsnapshot/snapuserd/Android.bp
@@ -19,7 +19,7 @@
 }
 
 cc_defaults {
-    name: "libsnapshot_snapuserd_defaults",
+    name: "libsnapuserd_client_defaults",
     defaults: [
         "fs_mgr_defaults",
     ],
@@ -33,15 +33,15 @@
 }
 
 cc_library_static {
-    name: "libsnapshot_snapuserd",
+    name: "libsnapuserd_client",
     defaults: [
         "fs_mgr_defaults",
-        "libsnapshot_snapuserd_defaults",
+        "libsnapuserd_client_defaults",
     ],
     recovery_available: true,
     static_libs: [
         "libcutils_sockets",
-        "libfs_mgr",
+        "libfs_mgr_file_wait",
     ],
     shared_libs: [
         "libbase",
@@ -60,32 +60,37 @@
     local_include_dirs: ["include/"],
     srcs: [
         "dm-snapshot-merge/snapuserd.cpp",
-        "dm-snapshot-merge/snapuserd_worker.cpp",
         "dm-snapshot-merge/snapuserd_readahead.cpp",
+        "dm-snapshot-merge/snapuserd_worker.cpp",
+        "dm_user_block_server.cpp",
         "snapuserd_buffer.cpp",
         "user-space-merge/handler_manager.cpp",
+        "user-space-merge/merge_worker.cpp",
         "user-space-merge/read_worker.cpp",
         "user-space-merge/snapuserd_core.cpp",
-        "user-space-merge/snapuserd_merge.cpp",
         "user-space-merge/snapuserd_readahead.cpp",
         "user-space-merge/snapuserd_transitions.cpp",
         "user-space-merge/snapuserd_verify.cpp",
         "user-space-merge/worker.cpp",
+        "utility.cpp",
     ],
     static_libs: [
         "libbase",
         "libdm",
+        "libext2_uuid",
         "libext4_utils",
         "libsnapshot_cow",
         "liburing",
     ],
     include_dirs: ["bionic/libc/kernel"],
+    export_include_dirs: ["include"],
     header_libs: [
         "libstorage_literals_headers",
     ],
     ramdisk_available: true,
     vendor_ramdisk_available: true,
     recovery_available: true,
+    host_supported: true,
 }
 
 cc_defaults {
@@ -104,12 +109,13 @@
         "libbrotli",
         "libcutils_sockets",
         "libdm",
-        "libfs_mgr",
+        "libext2_uuid",
+        "libfs_mgr_file_wait",
         "libgflags",
         "liblog",
         "libsnapshot_cow",
-        "libsnapshot_snapuserd",
         "libsnapuserd",
+        "libsnapuserd_client",
         "libz",
         "liblz4",
         "libext4_utils",
@@ -144,6 +150,9 @@
     init_rc: [
         "snapuserd.rc",
     ],
+    static_libs: [
+        "libsnapuserd_client",
+    ],
     ramdisk_available: false,
     vendor_ramdisk_available: true,
 }
@@ -186,12 +195,13 @@
         "libbrotli",
         "libgtest",
         "libsnapshot_cow",
-        "libsnapshot_snapuserd",
+        "libsnapuserd_client",
         "libcutils_sockets",
         "libz",
-        "libfs_mgr",
         "libdm",
+        "libext2_uuid",
         "libext4_utils",
+        "libfs_mgr_file_wait",
     ],
     header_libs: [
         "libstorage_literals_headers",
@@ -211,6 +221,9 @@
         "libsnapshot_cow_defaults",
     ],
     srcs: [
+        "testing/dm_user_harness.cpp",
+        "testing/harness.cpp",
+        "testing/host_harness.cpp",
         "user-space-merge/snapuserd_test.cpp",
     ],
     shared_libs: [
@@ -221,17 +234,20 @@
         "libbrotli",
         "libcutils_sockets",
         "libdm",
+        "libext2_uuid",
         "libext4_utils",
-        "libfs_mgr",
+        "libfs_mgr_file_wait",
         "libgflags",
         "libgtest",
         "libsnapshot_cow",
-        "libsnapshot_snapuserd",
         "libsnapuserd",
         "liburing",
         "libz",
     ],
-    include_dirs: ["bionic/libc/kernel"],
+    include_dirs: [
+        "bionic/libc/kernel",
+        ".",
+    ],
     header_libs: [
         "libstorage_literals_headers",
         "libfiemap_headers",
diff --git a/fs_mgr/libsnapshot/snapuserd/dm-snapshot-merge/snapuserd.cpp b/fs_mgr/libsnapshot/snapuserd/dm-snapshot-merge/snapuserd.cpp
index 978a7f2..71664bf 100644
--- a/fs_mgr/libsnapshot/snapuserd/dm-snapshot-merge/snapuserd.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/dm-snapshot-merge/snapuserd.cpp
@@ -734,8 +734,8 @@
     off_t offset = 0;
 
     for (int i = 0; i < num_threads; i++) {
-        std::async(std::launch::async, &Snapuserd::ReadBlocksToCache, this, dm_block_device,
-                   partition_name, offset, read_sz_per_thread);
+        (void)std::async(std::launch::async, &Snapuserd::ReadBlocksToCache, this, dm_block_device,
+                         partition_name, offset, read_sz_per_thread);
 
         offset += read_sz_per_thread;
     }
diff --git a/fs_mgr/libsnapshot/snapuserd/dm_user_block_server.cpp b/fs_mgr/libsnapshot/snapuserd/dm_user_block_server.cpp
new file mode 100644
index 0000000..e988335
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/dm_user_block_server.cpp
@@ -0,0 +1,152 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <snapuserd/dm_user_block_server.h>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <snapuserd/snapuserd_kernel.h>
+#include "snapuserd_logging.h"
+
+namespace android {
+namespace snapshot {
+
+using android::base::unique_fd;
+
+DmUserBlockServer::DmUserBlockServer(const std::string& misc_name, unique_fd&& ctrl_fd,
+                                     Delegate* delegate, size_t buffer_size)
+    : misc_name_(misc_name), ctrl_fd_(std::move(ctrl_fd)), delegate_(delegate) {
+    buffer_.Initialize(buffer_size);
+}
+
+bool DmUserBlockServer::ProcessRequests() {
+    struct dm_user_header* header = buffer_.GetHeaderPtr();
+    if (!android::base::ReadFully(ctrl_fd_, header, sizeof(*header))) {
+        if (errno != ENOTBLK) {
+            SNAP_PLOG(ERROR) << "Control-read failed";
+        }
+
+        SNAP_PLOG(DEBUG) << "ReadDmUserHeader failed....";
+        return false;
+    }
+
+    SNAP_LOG(DEBUG) << "Daemon: msg->seq: " << std::dec << header->seq;
+    SNAP_LOG(DEBUG) << "Daemon: msg->len: " << std::dec << header->len;
+    SNAP_LOG(DEBUG) << "Daemon: msg->sector: " << std::dec << header->sector;
+    SNAP_LOG(DEBUG) << "Daemon: msg->type: " << std::dec << header->type;
+    SNAP_LOG(DEBUG) << "Daemon: msg->flags: " << std::dec << header->flags;
+
+    if (!ProcessRequest(header)) {
+        if (header->type != DM_USER_RESP_ERROR) {
+            SendError();
+        }
+        return false;
+    }
+    return true;
+}
+
+bool DmUserBlockServer::ProcessRequest(dm_user_header* header) {
+    // Use the same header buffer as the response header.
+    int request_type = header->type;
+    header->type = DM_USER_RESP_SUCCESS;
+    header_response_ = true;
+
+    // Reset the output buffer.
+    buffer_.ResetBufferOffset();
+
+    switch (request_type) {
+        case DM_USER_REQ_MAP_READ:
+            return delegate_->RequestSectors(header->sector, header->len);
+
+        case DM_USER_REQ_MAP_WRITE:
+            // We should not get any write request to dm-user as we mount all
+            // partitions as read-only.
+            SNAP_LOG(ERROR) << "Unexpected write request from dm-user";
+            return false;
+
+        default:
+            SNAP_LOG(ERROR) << "Unexpected request from dm-user: " << request_type;
+            return false;
+    }
+}
+
+void* DmUserBlockServer::GetResponseBuffer(size_t size, size_t to_write) {
+    return buffer_.AcquireBuffer(size, to_write);
+}
+
+bool DmUserBlockServer::SendBufferedIo() {
+    return WriteDmUserPayload(buffer_.GetPayloadBytesWritten());
+}
+
+void DmUserBlockServer::SendError() {
+    struct dm_user_header* header = buffer_.GetHeaderPtr();
+    header->type = DM_USER_RESP_ERROR;
+    // This is an issue with the dm-user interface. There
+    // is no way to propagate the I/O error back to dm-user
+    // if we have already communicated the header back. Header
+    // is responded once at the beginning; however I/O can
+    // be processed in chunks. If we encounter an I/O error
+    // somewhere in the middle of the processing, we can't communicate
+    // this back to dm-user.
+    //
+    // TODO: Fix the interface
+    CHECK(header_response_);
+
+    WriteDmUserPayload(0);
+}
+
+bool DmUserBlockServer::WriteDmUserPayload(size_t size) {
+    size_t payload_size = size;
+    void* buf = buffer_.GetPayloadBufPtr();
+    if (header_response_) {
+        payload_size += sizeof(struct dm_user_header);
+        buf = buffer_.GetBufPtr();
+    }
+
+    if (!android::base::WriteFully(ctrl_fd_, buf, payload_size)) {
+        SNAP_PLOG(ERROR) << "Write to dm-user failed size: " << payload_size;
+        return false;
+    }
+
+    // After the first header is sent in response to a request, we cannot
+    // send any additional headers.
+    header_response_ = false;
+
+    // Reset the buffer for use by the next request.
+    buffer_.ResetBufferOffset();
+    return true;
+}
+
+DmUserBlockServerOpener::DmUserBlockServerOpener(const std::string& misc_name,
+                                                 const std::string& dm_user_path)
+    : misc_name_(misc_name), dm_user_path_(dm_user_path) {}
+
+std::unique_ptr<IBlockServer> DmUserBlockServerOpener::Open(IBlockServer::Delegate* delegate,
+                                                            size_t buffer_size) {
+    unique_fd fd(open(dm_user_path_.c_str(), O_RDWR | O_CLOEXEC));
+    if (fd < 0) {
+        SNAP_PLOG(ERROR) << "Could not open dm-user path: " << dm_user_path_;
+        return nullptr;
+    }
+    return std::make_unique<DmUserBlockServer>(misc_name_, std::move(fd), delegate, buffer_size);
+}
+
+std::shared_ptr<IBlockServerOpener> DmUserBlockServerFactory::CreateOpener(
+        const std::string& misc_name) {
+    auto dm_path = "/dev/dm-user/" + misc_name;
+    return std::make_shared<DmUserBlockServerOpener>(misc_name, dm_path);
+}
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/block_server.h b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/block_server.h
new file mode 100644
index 0000000..406bf11
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/block_server.h
@@ -0,0 +1,95 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <memory>
+
+namespace android {
+namespace snapshot {
+
+// These interfaces model the block device driver component of snapuserd (eg,
+// dm-user).
+
+// An open connection to a userspace block device control
+class IBlockServer {
+  public:
+    class Delegate {
+      public:
+        virtual ~Delegate() {}
+
+        // Respond to a request for reading a contiguous run of sectors. This
+        // call should be followed by calls to GetResponseBuffer/CommitBuffer
+        // until the |size| is fulfilled.
+        //
+        // If false is returned, an error will be automatically reported unless
+        // SendError was called.
+        virtual bool RequestSectors(uint64_t sector, uint64_t size) = 0;
+    };
+
+    virtual ~IBlockServer() {}
+
+    // Process I/O requests. This can block the worker thread until either a
+    // request is available or the underlying connection has been destroyed.
+    //
+    // True indicates that one or more requests was processed. False indicates
+    // an unrecoverable condition and processing should stop.
+    virtual bool ProcessRequests() = 0;
+
+    // Return a buffer for fulfilling a RequestSectors request. This buffer
+    // is valid until calling SendBufferedIo. This cannot be called outside
+    // of RequestSectors().
+    //
+    // "to_write" must be <= "size". If it is < size, the excess bytes are
+    // available for writing, but will not be send via SendBufferedIo, and
+    // may be reallocated in the next call to GetResponseBuffer.
+    //
+    // All buffers returned are invalidated after SendBufferedIo or returning
+    // control from RequestSectors.
+    virtual void* GetResponseBuffer(size_t size, size_t to_write) = 0;
+
+    // Send all outstanding buffers to the driver, in order. This should
+    // be called at least once in response to RequestSectors. This returns
+    // ownership of any buffers returned by GetResponseBuffer.
+    //
+    // If false is returned, an error is automatically reported to the driver.
+    virtual bool SendBufferedIo() = 0;
+
+    void* GetResponseBuffer(size_t size) { return GetResponseBuffer(size, size); }
+};
+
+class IBlockServerOpener {
+  public:
+    virtual ~IBlockServerOpener() = default;
+
+    // Open a connection to the service. This is called on the daemon thread.
+    //
+    // buffer_size is the maximum amount of buffered I/O to use.
+    virtual std::unique_ptr<IBlockServer> Open(IBlockServer::Delegate* delegate,
+                                               size_t buffer_size) = 0;
+};
+
+class IBlockServerFactory {
+  public:
+    virtual ~IBlockServerFactory() {}
+
+    // Return a new IBlockServerOpener given a unique device name.
+    virtual std::shared_ptr<IBlockServerOpener> CreateOpener(const std::string& misc_name) = 0;
+};
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/dm_user_block_server.h b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/dm_user_block_server.h
new file mode 100644
index 0000000..f1f8da1
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/dm_user_block_server.h
@@ -0,0 +1,68 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <android-base/unique_fd.h>
+
+#include <string>
+
+#include <snapuserd/block_server.h>
+#include <snapuserd/snapuserd_buffer.h>
+
+namespace android {
+namespace snapshot {
+
+class DmUserBlockServer : public IBlockServer {
+  public:
+    DmUserBlockServer(const std::string& misc_name, android::base::unique_fd&& ctrl_fd,
+                      Delegate* delegate, size_t buffer_size);
+
+    bool ProcessRequests() override;
+    void* GetResponseBuffer(size_t size, size_t to_write) override;
+    bool SendBufferedIo() override;
+    void SendError();
+
+  private:
+    bool ProcessRequest(dm_user_header* header);
+    bool WriteDmUserPayload(size_t size);
+
+    std::string misc_name_;
+    android::base::unique_fd ctrl_fd_;
+    Delegate* delegate_;
+
+    // Per-request state.
+    BufferSink buffer_;
+    bool header_response_ = false;
+};
+
+class DmUserBlockServerOpener : public IBlockServerOpener {
+  public:
+    DmUserBlockServerOpener(const std::string& misc_name, const std::string& dm_user_path);
+
+    std::unique_ptr<IBlockServer> Open(IBlockServer::Delegate* delegate,
+                                       size_t buffer_size) override;
+
+  private:
+    std::string misc_name_;
+    std::string dm_user_path_;
+};
+
+class DmUserBlockServerFactory : public IBlockServerFactory {
+  public:
+    std::shared_ptr<IBlockServerOpener> CreateOpener(const std::string& misc_name) override;
+};
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_buffer.h b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_buffer.h
index a6b6a7f..c5ca2b1 100644
--- a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_buffer.h
+++ b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_buffer.h
@@ -36,6 +36,21 @@
     struct dm_user_header* GetHeaderPtr();
     void ResetBufferOffset() { buffer_offset_ = 0; }
     void* GetPayloadBufPtr();
+    loff_t GetPayloadBytesWritten() { return buffer_offset_; }
+
+    // Same as calling GetPayloadBuffer and then UpdateBufferOffset.
+    //
+    // This is preferred over GetPayloadBuffer as it does not require a
+    // separate call to UpdateBufferOffset.
+    void* AcquireBuffer(size_t size) { return AcquireBuffer(size, size); }
+
+    // Same as AcquireBuffer, but separates the requested size from the buffer
+    // offset. This is useful for a situation where a full run of data will be
+    // read, but only a partial amount will be returned.
+    //
+    // If size != to_write, the excess bytes may be reallocated by the next
+    // call to AcquireBuffer.
+    void* AcquireBuffer(size_t size, size_t to_write);
 
   private:
     std::unique_ptr<uint8_t[]> buffer_;
@@ -43,19 +58,5 @@
     size_t buffer_size_;
 };
 
-class XorSink final {
-  public:
-    void Initialize(BufferSink* sink, size_t size);
-    void Reset();
-    void* GetBuffer(size_t requested, size_t* actual);
-    bool ReturnData(void* buffer, size_t len);
-
-  private:
-    BufferSink* bufsink_;
-    std::unique_ptr<uint8_t[]> buffer_;
-    size_t buffer_size_;
-    size_t returned_;
-};
-
 }  // namespace snapshot
 }  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
index 46952c4..7ab75dc 100644
--- a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
+++ b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
@@ -14,6 +14,8 @@
 
 #pragma once
 
+#include <linux/types.h>
+
 namespace android {
 namespace snapshot {
 
@@ -40,6 +42,7 @@
  * multiple of 512 bytes. Hence these two constants.
  */
 static constexpr uint32_t SECTOR_SHIFT = 9;
+static constexpr uint64_t SECTOR_SIZE = (1ULL << SECTOR_SHIFT);
 
 static constexpr size_t BLOCK_SZ = 4096;
 static constexpr size_t BLOCK_SHIFT = (__builtin_ffs(BLOCK_SZ) - 1);
@@ -69,7 +72,7 @@
 
     /* In sectors */
     uint32_t chunk_size;
-} __packed;
+} __attribute__((packed));
 
 // A disk exception is a mapping of old_chunk to new_chunk
 // old_chunk is the chunk ID of a dm-snapshot device.
@@ -77,7 +80,7 @@
 struct disk_exception {
     uint64_t old_chunk;
     uint64_t new_chunk;
-} __packed;
+} __attribute__((packed));
 
 // Control structures to communicate with dm-user
 // It comprises of header and a payload
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_buffer.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_buffer.cpp
index ab763ab..490c0e6 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_buffer.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_buffer.cpp
@@ -15,22 +15,36 @@
  */
 
 #include <snapuserd/snapuserd_buffer.h>
+
+#include <android-base/logging.h>
 #include <snapuserd/snapuserd_kernel.h>
 
 namespace android {
 namespace snapshot {
 
 void BufferSink::Initialize(size_t size) {
-    buffer_size_ = size;
+    buffer_size_ = size + sizeof(struct dm_user_header);
     buffer_offset_ = 0;
-    buffer_ = std::make_unique<uint8_t[]>(size);
+    buffer_ = std::make_unique<uint8_t[]>(buffer_size_);
+}
+
+void* BufferSink::AcquireBuffer(size_t size, size_t to_write) {
+    CHECK(to_write <= size);
+
+    void* ptr = GetPayloadBuffer(size);
+    if (!ptr) {
+        return nullptr;
+    }
+    UpdateBufferOffset(to_write);
+    return ptr;
 }
 
 void* BufferSink::GetPayloadBuffer(size_t size) {
-    if ((buffer_size_ - buffer_offset_) < size) return nullptr;
-
     char* buffer = reinterpret_cast<char*>(GetBufPtr());
     struct dm_user_message* msg = (struct dm_user_message*)(&(buffer[0]));
+    if ((buffer_size_ - buffer_offset_ - sizeof(msg->header)) < size) {
+        return nullptr;
+    }
     return (char*)msg->payload.buf + buffer_offset_;
 }
 
@@ -59,38 +73,5 @@
     return msg->payload.buf;
 }
 
-void XorSink::Initialize(BufferSink* sink, size_t size) {
-    bufsink_ = sink;
-    buffer_size_ = size;
-    returned_ = 0;
-    buffer_ = std::make_unique<uint8_t[]>(size);
-}
-
-void XorSink::Reset() {
-    returned_ = 0;
-}
-
-void* XorSink::GetBuffer(size_t requested, size_t* actual) {
-    if (requested > buffer_size_) {
-        *actual = buffer_size_;
-    } else {
-        *actual = requested;
-    }
-    return buffer_.get();
-}
-
-bool XorSink::ReturnData(void* buffer, size_t len) {
-    uint8_t* xor_data = reinterpret_cast<uint8_t*>(buffer);
-    uint8_t* buff = reinterpret_cast<uint8_t*>(bufsink_->GetPayloadBuffer(len + returned_));
-    if (buff == nullptr) {
-        return false;
-    }
-    for (size_t i = 0; i < len; i++) {
-        buff[returned_ + i] ^= xor_data[i];
-    }
-    returned_ += len;
-    return true;
-}
-
 }  // namespace snapshot
 }  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_logging.h b/fs_mgr/libsnapshot/snapuserd/snapuserd_logging.h
new file mode 100644
index 0000000..bc470ce
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_logging.h
@@ -0,0 +1,20 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <android-base/logging.h>
+
+#define SNAP_LOG(level) LOG(level) << misc_name_ << ": "
+#define SNAP_PLOG(level) PLOG(level) << misc_name_ << ": "
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/dm_user_harness.cpp b/fs_mgr/libsnapshot/snapuserd/testing/dm_user_harness.cpp
new file mode 100644
index 0000000..7cadf25
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/testing/dm_user_harness.cpp
@@ -0,0 +1,67 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "dm_user_harness.h"
+
+#include <fcntl.h>
+
+#include <android-base/file.h>
+#include <fs_mgr/file_wait.h>
+#include <libdm/dm.h>
+#include <snapuserd/dm_user_block_server.h>
+
+namespace android {
+namespace snapshot {
+
+using namespace std::chrono_literals;
+using android::base::unique_fd;
+
+DmUserDevice::DmUserDevice(std::unique_ptr<Tempdevice>&& dev) : dev_(std::move(dev)) {}
+
+const std::string& DmUserDevice::GetPath() {
+    return dev_->path();
+}
+
+bool DmUserDevice::Destroy() {
+    return dev_->Destroy();
+}
+
+DmUserTestHarness::DmUserTestHarness() {
+    block_server_factory_ = std::make_unique<DmUserBlockServerFactory>();
+}
+
+std::unique_ptr<IUserDevice> DmUserTestHarness::CreateUserDevice(const std::string& dev_name,
+                                                                 const std::string& misc_name,
+                                                                 uint64_t num_sectors) {
+    android::dm::DmTable dmuser_table;
+    dmuser_table.Emplace<android::dm::DmTargetUser>(0, num_sectors, misc_name);
+    auto dev = std::make_unique<Tempdevice>(dev_name, dmuser_table);
+    if (!dev->valid()) {
+        return nullptr;
+    }
+
+    auto misc_device = "/dev/dm-user/" + misc_name;
+    if (!android::fs_mgr::WaitForFile(misc_device, 10s)) {
+        return nullptr;
+    }
+
+    return std::make_unique<DmUserDevice>(std::move(dev));
+}
+
+IBlockServerFactory* DmUserTestHarness::GetBlockServerFactory() {
+    return block_server_factory_.get();
+}
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/dm_user_harness.h b/fs_mgr/libsnapshot/snapuserd/testing/dm_user_harness.h
new file mode 100644
index 0000000..cf26bed
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/testing/dm_user_harness.h
@@ -0,0 +1,54 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <android-base/unique_fd.h>
+
+#include "harness.h"
+#include "temp_device.h"
+
+namespace android {
+namespace snapshot {
+
+using android::base::unique_fd;
+
+class DmUserBlockServerFactory;
+
+class DmUserDevice final : public IUserDevice {
+  public:
+    explicit DmUserDevice(std::unique_ptr<Tempdevice>&& dev);
+    const std::string& GetPath() override;
+    bool Destroy() override;
+
+  private:
+    std::unique_ptr<Tempdevice> dev_;
+};
+
+class DmUserTestHarness final : public ITestHarness {
+  public:
+    DmUserTestHarness();
+
+    std::unique_ptr<IUserDevice> CreateUserDevice(const std::string& dev_name,
+                                                  const std::string& misc_name,
+                                                  uint64_t num_sectors) override;
+    IBlockServerFactory* GetBlockServerFactory() override;
+    bool HasUserDevice() override { return true; }
+
+  private:
+    std::unique_ptr<DmUserBlockServerFactory> block_server_factory_;
+};
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/harness.cpp b/fs_mgr/libsnapshot/snapuserd/testing/harness.cpp
new file mode 100644
index 0000000..02ae549
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/testing/harness.cpp
@@ -0,0 +1,116 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "harness.h"
+
+#ifdef __ANDROID__
+#include <linux/memfd.h>
+#endif
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+#include <android-base/file.h>
+#include <ext4_utils/ext4_utils.h>
+#include <libdm/loop_control.h>
+#include "snapuserd_logging.h"
+
+namespace android {
+namespace snapshot {
+
+using namespace std::chrono_literals;
+using android::base::unique_fd;
+using android::dm::LoopDevice;
+
+#ifdef __ANDROID__
+// Prefer this on device since it is a real block device, which is more similar
+// to how we use snapuserd.
+class MemoryBackedDevice final : public IBackingDevice {
+  public:
+    bool Init(uint64_t size) {
+        memfd_.reset(memfd_create("snapuserd_test", MFD_ALLOW_SEALING));
+        if (memfd_ < 0) {
+            PLOG(ERROR) << "memfd_create failed";
+            return false;
+        }
+        if (ftruncate(memfd_.get(), size) < 0) {
+            PLOG(ERROR) << "ftruncate failed";
+            return false;
+        }
+        if (fcntl(memfd_.get(), F_ADD_SEALS, F_SEAL_GROW | F_SEAL_SHRINK) < 0) {
+            PLOG(ERROR) << "fcntl seal failed";
+            return false;
+        }
+        dev_ = std::make_unique<LoopDevice>(memfd_, 10s);
+        return dev_->valid();
+    }
+    const std::string& GetPath() override { return dev_->device(); }
+    uint64_t GetSize() override {
+        unique_fd fd(open(GetPath().c_str(), O_RDONLY | O_CLOEXEC));
+        if (fd < 0) {
+            PLOG(ERROR) << "open failed: " << GetPath();
+            return 0;
+        }
+        return get_block_device_size(fd.get());
+    }
+
+  private:
+    unique_fd memfd_;
+    std::unique_ptr<LoopDevice> dev_;
+};
+#endif
+
+class FileBackedDevice final : public IBackingDevice {
+  public:
+    bool Init(uint64_t size) {
+        if (temp_.fd < 0) {
+            return false;
+        }
+        if (ftruncate(temp_.fd, size) < 0) {
+            PLOG(ERROR) << "ftruncate failed: " << temp_.path;
+            return false;
+        }
+        path_ = temp_.path;
+        return true;
+    }
+
+    const std::string& GetPath() override { return path_; }
+    uint64_t GetSize() override {
+        off_t off = lseek(temp_.fd, 0, SEEK_END);
+        if (off < 0) {
+            PLOG(ERROR) << "lseek failed: " << temp_.path;
+            return 0;
+        }
+        return off;
+    }
+
+  private:
+    TemporaryFile temp_;
+    std::string path_;
+};
+
+std::unique_ptr<IBackingDevice> ITestHarness::CreateBackingDevice(uint64_t size) {
+#ifdef __ANDROID__
+    auto dev = std::make_unique<MemoryBackedDevice>();
+#else
+    auto dev = std::make_unique<FileBackedDevice>();
+#endif
+    if (!dev->Init(size)) {
+        return nullptr;
+    }
+    return dev;
+}
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/harness.h b/fs_mgr/libsnapshot/snapuserd/testing/harness.h
new file mode 100644
index 0000000..ffe9f7b
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/testing/harness.h
@@ -0,0 +1,56 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <stddef.h>
+#include <sys/types.h>
+
+#include <memory>
+
+#include <android-base/unique_fd.h>
+#include <snapuserd/block_server.h>
+
+namespace android {
+namespace snapshot {
+
+// Interface for a "block driver in userspace" device.
+class IUserDevice {
+  public:
+    virtual ~IUserDevice() {}
+    virtual const std::string& GetPath() = 0;
+    virtual bool Destroy() = 0;
+};
+
+// Interface for an fd/temp file that is a block device when possible.
+class IBackingDevice {
+  public:
+    virtual ~IBackingDevice() {}
+    virtual const std::string& GetPath() = 0;
+    virtual uint64_t GetSize() = 0;
+};
+
+class ITestHarness {
+  public:
+    virtual ~ITestHarness() {}
+    virtual std::unique_ptr<IUserDevice> CreateUserDevice(const std::string& dev_name,
+                                                          const std::string& misc_name,
+                                                          uint64_t num_sectors) = 0;
+    virtual IBlockServerFactory* GetBlockServerFactory() = 0;
+    virtual bool HasUserDevice() = 0;
+    virtual std::unique_ptr<IBackingDevice> CreateBackingDevice(uint64_t size);
+};
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/host_harness.cpp b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.cpp
new file mode 100644
index 0000000..0d230ad
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.cpp
@@ -0,0 +1,112 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "host_harness.h"
+
+#include "snapuserd_logging.h"
+
+namespace android {
+namespace snapshot {
+
+void TestBlockServerQueue::WaitForShutdown() {
+    std::unique_lock lock(m_);
+    if (shutdown_) {
+        return;
+    }
+    cv_.wait(lock, [this]() -> bool { return shutdown_; });
+}
+
+void TestBlockServerQueue::Shutdown() {
+    std::unique_lock lock(m_);
+    shutdown_ = true;
+    cv_.notify_all();
+}
+
+TestBlockServer::TestBlockServer(std::shared_ptr<TestBlockServerQueue> queue,
+                                 const std::string& misc_name)
+    : queue_(queue), misc_name_(misc_name) {}
+
+bool TestBlockServer::ProcessRequests() {
+    queue_->WaitForShutdown();
+    return false;
+}
+
+void* TestBlockServer::GetResponseBuffer(size_t size, size_t to_write) {
+    std::string buffer(size, '\0');
+    buffered_.emplace_back(std::move(buffer), to_write);
+    return buffered_.back().first.data();
+}
+
+bool TestBlockServer::SendBufferedIo() {
+    for (const auto& [data, to_write] : buffered_) {
+        sent_io_ += data.substr(0, to_write);
+    }
+    buffered_.clear();
+    return true;
+}
+
+TestBlockServerOpener::TestBlockServerOpener(std::shared_ptr<TestBlockServerQueue> queue,
+                                             const std::string& misc_name)
+    : queue_(queue), misc_name_(misc_name) {}
+
+std::unique_ptr<IBlockServer> TestBlockServerOpener::Open(IBlockServer::Delegate*, size_t) {
+    return std::make_unique<TestBlockServer>(queue_, misc_name_);
+}
+
+std::shared_ptr<TestBlockServerOpener> TestBlockServerFactory::CreateTestOpener(
+        const std::string& misc_name) {
+    if (queues_.count(misc_name)) {
+        LOG(ERROR) << "Cannot create opener for " << misc_name << ", already exists";
+        return nullptr;
+    }
+    auto queue = std::make_shared<TestBlockServerQueue>();
+    queues_.emplace(misc_name, queue);
+    return std::make_shared<TestBlockServerOpener>(queue, misc_name);
+}
+
+std::shared_ptr<IBlockServerOpener> TestBlockServerFactory::CreateOpener(
+        const std::string& misc_name) {
+    return CreateTestOpener(misc_name);
+}
+
+bool TestBlockServerFactory::DeleteQueue(const std::string& misc_name) {
+    auto iter = queues_.find(misc_name);
+    if (iter == queues_.end()) {
+        LOG(ERROR) << "Cannot delete queue " << misc_name << ", not found";
+        return false;
+    }
+    iter->second->Shutdown();
+    queues_.erase(iter);
+    return true;
+}
+
+HostUserDevice::HostUserDevice(TestBlockServerFactory* factory, const std::string& misc_name)
+    : factory_(factory), misc_name_(misc_name) {}
+
+bool HostUserDevice::Destroy() {
+    return factory_->DeleteQueue(misc_name_);
+}
+
+std::unique_ptr<IUserDevice> HostTestHarness::CreateUserDevice(const std::string&,
+                                                               const std::string& misc_name,
+                                                               uint64_t) {
+    return std::make_unique<HostUserDevice>(&factory_, misc_name);
+}
+
+IBlockServerFactory* HostTestHarness::GetBlockServerFactory() {
+    return &factory_;
+}
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/host_harness.h b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.h
new file mode 100644
index 0000000..ec0bd29
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.h
@@ -0,0 +1,105 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <condition_variable>
+#include <mutex>
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#include "harness.h"
+
+namespace android {
+namespace snapshot {
+
+class TestBlockServerQueue final {
+  public:
+    void WaitForShutdown();
+    void Shutdown();
+
+  private:
+    std::mutex m_;
+    std::condition_variable cv_;
+    bool shutdown_ = false;
+};
+
+class TestBlockServer final : public IBlockServer {
+  public:
+    TestBlockServer(std::shared_ptr<TestBlockServerQueue> queue, const std::string& misc_name);
+    bool ProcessRequests() override;
+    void* GetResponseBuffer(size_t size, size_t to_write) override;
+    bool SendBufferedIo() override;
+
+    std::string&& sent_io() { return std::move(sent_io_); }
+
+  private:
+    std::shared_ptr<TestBlockServerQueue> queue_;
+    std::string misc_name_;
+    std::string sent_io_;
+    std::vector<std::pair<std::string, size_t>> buffered_;
+};
+
+class TestBlockServerOpener final : public IBlockServerOpener {
+  public:
+    TestBlockServerOpener(std::shared_ptr<TestBlockServerQueue> queue,
+                          const std::string& misc_name);
+    std::unique_ptr<IBlockServer> Open(IBlockServer::Delegate* delegate,
+                                       size_t buffer_size) override;
+
+  private:
+    std::shared_ptr<TestBlockServerQueue> queue_;
+    std::string misc_name_;
+};
+
+class TestBlockServerFactory final : public IBlockServerFactory {
+  public:
+    std::shared_ptr<IBlockServerOpener> CreateOpener(const std::string& misc_name) override;
+    std::shared_ptr<TestBlockServerOpener> CreateTestOpener(const std::string& misc_name);
+    bool DeleteQueue(const std::string& misc_name);
+
+  private:
+    std::unordered_map<std::string, std::shared_ptr<TestBlockServerQueue>> queues_;
+};
+
+class TestBlockServerFactory;
+
+class HostUserDevice final : public IUserDevice {
+  public:
+    HostUserDevice(TestBlockServerFactory* factory, const std::string& misc_name);
+    const std::string& GetPath() override { return empty_path_; }
+    bool Destroy();
+
+  private:
+    TestBlockServerFactory* factory_;
+    std::string misc_name_;
+    std::string empty_path_;
+};
+
+class HostTestHarness final : public ITestHarness {
+  public:
+    std::unique_ptr<IUserDevice> CreateUserDevice(const std::string& dev_name,
+                                                  const std::string& misc_name,
+                                                  uint64_t num_sectors) override;
+    IBlockServerFactory* GetBlockServerFactory() override;
+    bool HasUserDevice() override { return false; }
+
+  private:
+    TestBlockServerFactory factory_;
+};
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/temp_device.h b/fs_mgr/libsnapshot/snapuserd/testing/temp_device.h
new file mode 100644
index 0000000..2a6d3ea
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/testing/temp_device.h
@@ -0,0 +1,72 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <chrono>
+#include <string>
+
+#include <libdm/dm.h>
+
+namespace android {
+namespace snapshot {
+
+using android::dm::DeviceMapper;
+using android::dm::DmTable;
+
+class Tempdevice {
+  public:
+    Tempdevice(const std::string& name, const DmTable& table)
+        : dm_(DeviceMapper::Instance()), name_(name), valid_(false) {
+        valid_ = dm_.CreateDevice(name, table, &path_, std::chrono::seconds(5));
+    }
+    Tempdevice(Tempdevice&& other) noexcept
+        : dm_(other.dm_), name_(other.name_), path_(other.path_), valid_(other.valid_) {
+        other.valid_ = false;
+    }
+    ~Tempdevice() {
+        if (valid_) {
+            dm_.DeleteDeviceIfExists(name_);
+        }
+    }
+    bool Destroy() {
+        if (!valid_) {
+            return true;
+        }
+        valid_ = false;
+        return dm_.DeleteDeviceIfExists(name_);
+    }
+    const std::string& path() const { return path_; }
+    const std::string& name() const { return name_; }
+    bool valid() const { return valid_; }
+
+    Tempdevice(const Tempdevice&) = delete;
+    Tempdevice& operator=(const Tempdevice&) = delete;
+
+    Tempdevice& operator=(Tempdevice&& other) noexcept {
+        name_ = other.name_;
+        valid_ = other.valid_;
+        other.valid_ = false;
+        return *this;
+    }
+
+  private:
+    DeviceMapper& dm_;
+    std::string name_;
+    std::string path_;
+    bool valid_;
+};
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.cpp
index 4105b4b..d979e20 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.cpp
@@ -14,13 +14,14 @@
 
 #include "handler_manager.h"
 
+#include <pthread.h>
 #include <sys/eventfd.h>
 
 #include <android-base/logging.h>
 
+#include "merge_worker.h"
 #include "read_worker.h"
 #include "snapuserd_core.h"
-#include "snapuserd_merge.h"
 
 namespace android {
 namespace snapshot {
@@ -50,9 +51,10 @@
 std::shared_ptr<HandlerThread> SnapshotHandlerManager::AddHandler(
         const std::string& misc_name, const std::string& cow_device_path,
         const std::string& backing_device, const std::string& base_path_merge,
-        int num_worker_threads, bool use_iouring, bool perform_verification) {
+        std::shared_ptr<IBlockServerOpener> opener, int num_worker_threads, bool use_iouring,
+        bool perform_verification) {
     auto snapuserd = std::make_shared<SnapshotHandler>(misc_name, cow_device_path, backing_device,
-                                                       base_path_merge, num_worker_threads,
+                                                       base_path_merge, opener, num_worker_threads,
                                                        use_iouring, perform_verification);
     if (!snapuserd->InitCowDevice()) {
         LOG(ERROR) << "Failed to initialize Snapuserd";
@@ -131,6 +133,8 @@
 void SnapshotHandlerManager::RunThread(std::shared_ptr<HandlerThread> handler) {
     LOG(INFO) << "Entering thread for handler: " << handler->misc_name();
 
+    pthread_setname_np(pthread_self(), "Handler");
+
     if (!handler->snapuserd()->Start()) {
         LOG(ERROR) << " Failed to launch all worker threads";
     }
@@ -200,9 +204,8 @@
 
     handler->snapuserd()->MonitorMerge();
 
-    if (!is_merge_monitor_started_) {
-        std::thread(&SnapshotHandlerManager::MonitorMerge, this).detach();
-        is_merge_monitor_started_ = true;
+    if (!merge_monitor_.joinable()) {
+        merge_monitor_ = std::thread(&SnapshotHandlerManager::MonitorMerge, this);
     }
 
     merge_handlers_.push(handler);
@@ -219,6 +222,7 @@
 }
 
 void SnapshotHandlerManager::MonitorMerge() {
+    pthread_setname_np(pthread_self(), "Merge Monitor");
     while (!stop_monitor_merge_thread_) {
         uint64_t testVal;
         ssize_t ret =
@@ -356,8 +360,12 @@
         if (th.joinable()) th.join();
     }
 
-    stop_monitor_merge_thread_ = true;
-    WakeupMonitorMergeThread();
+    if (merge_monitor_.joinable()) {
+        stop_monitor_merge_thread_ = true;
+        WakeupMonitorMergeThread();
+
+        merge_monitor_.join();
+    }
 }
 
 auto SnapshotHandlerManager::FindHandler(std::lock_guard<std::mutex>* proof_of_lock,
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.h
index b7ddac1..b1605f0 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/handler_manager.h
@@ -21,6 +21,7 @@
 #include <vector>
 
 #include <android-base/unique_fd.h>
+#include <snapuserd/block_server.h>
 
 namespace android {
 namespace snapshot {
@@ -55,6 +56,7 @@
                                                       const std::string& cow_device_path,
                                                       const std::string& backing_device,
                                                       const std::string& base_path_merge,
+                                                      std::shared_ptr<IBlockServerOpener> opener,
                                                       int num_worker_threads, bool use_iouring,
                                                       bool perform_verification) = 0;
 
@@ -91,6 +93,7 @@
                                               const std::string& cow_device_path,
                                               const std::string& backing_device,
                                               const std::string& base_path_merge,
+                                              std::shared_ptr<IBlockServerOpener> opener,
                                               int num_worker_threads, bool use_iouring,
                                               bool perform_verification) override;
     bool StartHandler(const std::string& misc_name) override;
@@ -119,9 +122,9 @@
     std::mutex lock_;
     HandlerList dm_users_;
 
-    bool is_merge_monitor_started_ = false;
     bool stop_monitor_merge_thread_ = false;
     int active_merge_threads_ = 0;
+    std::thread merge_monitor_;
     int num_partitions_merge_complete_ = 0;
     std::queue<std::shared_ptr<HandlerThread>> merge_handlers_;
     android::base::unique_fd monitor_merge_event_fd_;
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.cpp
similarity index 97%
rename from fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.cpp
rename to fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.cpp
index 563f6ad..11b8d7c 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.cpp
@@ -13,9 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#include "snapuserd_merge.h"
+#include "merge_worker.h"
+
+#include <pthread.h>
 
 #include "snapuserd_core.h"
+#include "utility.h"
 
 namespace android {
 namespace snapshot {
@@ -106,9 +109,9 @@
         for (size_t i = 0; i < replace_zero_vec.size(); i++) {
             const CowOperation* cow_op = replace_zero_vec[i];
 
-            void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
+            void* buffer = bufsink_.AcquireBuffer(BLOCK_SZ);
             if (!buffer) {
-                SNAP_LOG(ERROR) << "Failed to acquire buffer in merge";
+                SNAP_LOG(ERROR) << "AcquireBuffer failed in MergeReplaceOps";
                 return false;
             }
             if (cow_op->type == kCowReplaceOp) {
@@ -120,8 +123,6 @@
                 CHECK(cow_op->type == kCowZeroOp);
                 memset(buffer, 0, BLOCK_SZ);
             }
-
-            bufsink_.UpdateBufferOffset(BLOCK_SZ);
         }
 
         size_t io_size = linear_blocks * BLOCK_SZ;
@@ -199,6 +200,7 @@
         // Wait for RA thread to notify that the merge window
         // is ready for merging.
         if (!snapuserd_->WaitForMergeBegin()) {
+            SNAP_LOG(ERROR) << "Failed waiting for merge to begin";
             return false;
         }
 
@@ -304,7 +306,7 @@
                     // will fallback to synchronous I/O.
                     ret = io_uring_wait_cqe(ring_.get(), &cqe);
                     if (ret) {
-                        SNAP_LOG(ERROR) << "Merge: io_uring_wait_cqe failed: " << ret;
+                        SNAP_LOG(ERROR) << "Merge: io_uring_wait_cqe failed: " << strerror(-ret);
                         status = false;
                         break;
                     }
@@ -547,17 +549,22 @@
 
 bool MergeWorker::Run() {
     SNAP_LOG(DEBUG) << "Waiting for merge begin...";
+
+    pthread_setname_np(pthread_self(), "MergeWorker");
+
     if (!snapuserd_->WaitForMergeBegin()) {
         SNAP_LOG(ERROR) << "Merge terminated early...";
         return true;
     }
 
-    if (setpriority(PRIO_PROCESS, gettid(), kNiceValueForMergeThreads)) {
-        SNAP_PLOG(ERROR) << "Failed to set priority for TID: " << gettid();
+    if (!SetThreadPriority(kNiceValueForMergeThreads)) {
+        SNAP_PLOG(ERROR) << "Failed to set thread priority";
     }
 
     SNAP_LOG(INFO) << "Merge starting..";
 
+    bufsink_.Initialize(PAYLOAD_BUFFER_SZ);
+
     if (!Init()) {
         SNAP_LOG(ERROR) << "Merge thread initialization failed...";
         snapuserd_->MergeFailed();
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.h
similarity index 98%
rename from fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.h
rename to fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.h
index f35147f..478d4c8 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/merge_worker.h
@@ -39,6 +39,7 @@
     void FinalizeIouring();
 
   private:
+    BufferSink bufsink_;
     std::unique_ptr<ICowOpIter> cowop_iter_;
     std::unique_ptr<struct io_uring> ring_;
     size_t ra_block_index_ = 0;
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.cpp
index dd2996b..b9ecfa5 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.cpp
@@ -16,7 +16,10 @@
 
 #include "read_worker.h"
 
+#include <pthread.h>
+
 #include "snapuserd_core.h"
+#include "utility.h"
 
 namespace android {
 namespace snapshot {
@@ -26,28 +29,23 @@
 using android::base::unique_fd;
 
 void ReadWorker::CloseFds() {
-    ctrl_fd_ = {};
+    block_server_ = {};
     backing_store_fd_ = {};
     Worker::CloseFds();
 }
 
 ReadWorker::ReadWorker(const std::string& cow_device, const std::string& backing_device,
-                       const std::string& control_device, const std::string& misc_name,
-                       const std::string& base_path_merge,
-                       std::shared_ptr<SnapshotHandler> snapuserd)
+                       const std::string& misc_name, const std::string& base_path_merge,
+                       std::shared_ptr<SnapshotHandler> snapuserd,
+                       std::shared_ptr<IBlockServerOpener> opener)
     : Worker(cow_device, misc_name, base_path_merge, snapuserd),
       backing_store_device_(backing_device),
-      control_device_(control_device) {}
+      block_server_opener_(opener) {}
 
 // Start the replace operation. This will read the
 // internal COW format and if the block is compressed,
 // it will be de-compressed.
-bool ReadWorker::ProcessReplaceOp(const CowOperation* cow_op) {
-    void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
-    if (!buffer) {
-        SNAP_LOG(ERROR) << "ProcessReplaceOp failed to allocate buffer";
-        return false;
-    }
+bool ReadWorker::ProcessReplaceOp(const CowOperation* cow_op, void* buffer) {
     if (!reader_->ReadData(cow_op, buffer, BLOCK_SZ)) {
         SNAP_LOG(ERROR) << "ProcessReplaceOp failed for block " << cow_op->new_block;
         return false;
@@ -55,12 +53,7 @@
     return true;
 }
 
-bool ReadWorker::ReadFromSourceDevice(const CowOperation* cow_op) {
-    void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
-    if (buffer == nullptr) {
-        SNAP_LOG(ERROR) << "ReadFromBaseDevice: Failed to get payload buffer";
-        return false;
-    }
+bool ReadWorker::ReadFromSourceDevice(const CowOperation* cow_op, void* buffer) {
     uint64_t offset;
     if (!reader_->GetSourceOffset(cow_op, &offset)) {
         SNAP_LOG(ERROR) << "ReadFromSourceDevice: Failed to get source offset";
@@ -85,60 +78,43 @@
 
 // Start the copy operation. This will read the backing
 // block device which is represented by cow_op->source.
-bool ReadWorker::ProcessCopyOp(const CowOperation* cow_op) {
-    if (!ReadFromSourceDevice(cow_op)) {
+bool ReadWorker::ProcessCopyOp(const CowOperation* cow_op, void* buffer) {
+    if (!ReadFromSourceDevice(cow_op, buffer)) {
         return false;
     }
-
     return true;
 }
 
-bool ReadWorker::ProcessXorOp(const CowOperation* cow_op) {
-    if (!ReadFromSourceDevice(cow_op)) {
+bool ReadWorker::ProcessXorOp(const CowOperation* cow_op, void* buffer) {
+    if (!ReadFromSourceDevice(cow_op, buffer)) {
         return false;
     }
 
-    xorsink_.Reset();
-
-    size_t actual = 0;
-    void* buffer = xorsink_.GetBuffer(BLOCK_SZ, &actual);
-    if (!buffer || actual < BLOCK_SZ) {
-        SNAP_LOG(ERROR) << "ProcessXorOp failed to get buffer of " << BLOCK_SZ << " size, got "
-                        << actual;
-        return false;
+    if (xor_buffer_.empty()) {
+        xor_buffer_.resize(BLOCK_SZ);
     }
-    ssize_t size = reader_->ReadData(cow_op, buffer, BLOCK_SZ);
+    CHECK(xor_buffer_.size() == BLOCK_SZ);
+
+    ssize_t size = reader_->ReadData(cow_op, xor_buffer_.data(), xor_buffer_.size());
     if (size != BLOCK_SZ) {
         SNAP_LOG(ERROR) << "ProcessXorOp failed for block " << cow_op->new_block
                         << ", return value: " << size;
         return false;
     }
-    if (!xorsink_.ReturnData(buffer, size)) {
-        SNAP_LOG(ERROR) << "ProcessXorOp failed to return data";
-        return false;
+
+    auto xor_out = reinterpret_cast<uint8_t*>(buffer);
+    for (size_t i = 0; i < BLOCK_SZ; i++) {
+        xor_out[i] ^= xor_buffer_[i];
     }
     return true;
 }
 
-bool ReadWorker::ProcessZeroOp() {
-    // Zero out the entire block
-    void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
-    if (buffer == nullptr) {
-        SNAP_LOG(ERROR) << "ProcessZeroOp: Failed to get payload buffer";
-        return false;
-    }
-
+bool ReadWorker::ProcessZeroOp(void* buffer) {
     memset(buffer, 0, BLOCK_SZ);
     return true;
 }
 
-bool ReadWorker::ProcessOrderedOp(const CowOperation* cow_op) {
-    void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
-    if (buffer == nullptr) {
-        SNAP_LOG(ERROR) << "ProcessOrderedOp: Failed to get payload buffer";
-        return false;
-    }
-
+bool ReadWorker::ProcessOrderedOp(const CowOperation* cow_op, void* buffer) {
     MERGE_GROUP_STATE state = snapuserd_->ProcessMergingBlock(cow_op->new_block, buffer);
 
     switch (state) {
@@ -148,7 +124,7 @@
             SNAP_LOG(DEBUG) << "Merge-completed: Reading from base device sector: "
                             << (cow_op->new_block >> SECTOR_SHIFT)
                             << " Block-number: " << cow_op->new_block;
-            if (!ReadDataFromBaseDevice(ChunkToSector(cow_op->new_block), BLOCK_SZ)) {
+            if (!ReadDataFromBaseDevice(ChunkToSector(cow_op->new_block), buffer, BLOCK_SZ)) {
                 SNAP_LOG(ERROR) << "ReadDataFromBaseDevice at sector: "
                                 << (cow_op->new_block >> SECTOR_SHIFT) << " after merge-complete.";
                 return false;
@@ -158,9 +134,9 @@
         case MERGE_GROUP_STATE::GROUP_MERGE_PENDING: {
             bool ret;
             if (cow_op->type == kCowCopyOp) {
-                ret = ProcessCopyOp(cow_op);
+                ret = ProcessCopyOp(cow_op, buffer);
             } else {
-                ret = ProcessXorOp(cow_op);
+                ret = ProcessXorOp(cow_op, buffer);
             }
 
             // I/O is complete - decrement the refcount irrespective of the return
@@ -185,7 +161,7 @@
     return false;
 }
 
-bool ReadWorker::ProcessCowOp(const CowOperation* cow_op) {
+bool ReadWorker::ProcessCowOp(const CowOperation* cow_op, void* buffer) {
     if (cow_op == nullptr) {
         SNAP_LOG(ERROR) << "ProcessCowOp: Invalid cow_op";
         return false;
@@ -193,17 +169,17 @@
 
     switch (cow_op->type) {
         case kCowReplaceOp: {
-            return ProcessReplaceOp(cow_op);
+            return ProcessReplaceOp(cow_op, buffer);
         }
 
         case kCowZeroOp: {
-            return ProcessZeroOp();
+            return ProcessZeroOp(buffer);
         }
 
         case kCowCopyOp:
             [[fallthrough]];
         case kCowXorOp: {
-            return ProcessOrderedOp(cow_op);
+            return ProcessOrderedOp(cow_op, buffer);
         }
 
         default: {
@@ -224,26 +200,26 @@
         return false;
     }
 
-    ctrl_fd_.reset(open(control_device_.c_str(), O_RDWR));
-    if (ctrl_fd_ < 0) {
-        SNAP_PLOG(ERROR) << "Unable to open " << control_device_;
+    block_server_ = block_server_opener_->Open(this, PAYLOAD_BUFFER_SZ);
+    if (!block_server_) {
+        SNAP_PLOG(ERROR) << "Unable to open block server";
         return false;
     }
-
-    xorsink_.Initialize(&bufsink_, BLOCK_SZ);
     return true;
 }
 
 bool ReadWorker::Run() {
     SNAP_LOG(INFO) << "Processing snapshot I/O requests....";
 
-    if (setpriority(PRIO_PROCESS, gettid(), kNiceValueForMergeThreads)) {
-        SNAP_PLOG(ERROR) << "Failed to set priority for TID: " << gettid();
+    pthread_setname_np(pthread_self(), "ReadWorker");
+
+    if (!SetThreadPriority(kNiceValueForMergeThreads)) {
+        SNAP_PLOG(ERROR) << "Failed to set thread priority";
     }
 
     // Start serving IO
     while (true) {
-        if (!ProcessIORequest()) {
+        if (!block_server_->ProcessRequests()) {
             break;
         }
     }
@@ -254,35 +230,9 @@
     return true;
 }
 
-// Send the payload/data back to dm-user misc device.
-bool ReadWorker::WriteDmUserPayload(size_t size) {
-    size_t payload_size = size;
-    void* buf = bufsink_.GetPayloadBufPtr();
-    if (header_response_) {
-        payload_size += sizeof(struct dm_user_header);
-        buf = bufsink_.GetBufPtr();
-    }
-
-    if (!android::base::WriteFully(ctrl_fd_, buf, payload_size)) {
-        SNAP_PLOG(ERROR) << "Write to dm-user failed size: " << payload_size;
-        return false;
-    }
-
-    // After the first header is sent in response to a request, we cannot
-    // send any additional headers.
-    header_response_ = false;
-    return true;
-}
-
-bool ReadWorker::ReadDataFromBaseDevice(sector_t sector, size_t read_size) {
+bool ReadWorker::ReadDataFromBaseDevice(sector_t sector, void* buffer, size_t read_size) {
     CHECK(read_size <= BLOCK_SZ);
 
-    void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
-    if (buffer == nullptr) {
-        SNAP_LOG(ERROR) << "ReadFromBaseDevice: Failed to get payload buffer";
-        return false;
-    }
-
     loff_t offset = sector << SECTOR_SHIFT;
     if (!android::base::ReadFullyAtOffset(base_path_merge_fd_, buffer, read_size, offset)) {
         SNAP_PLOG(ERROR) << "ReadDataFromBaseDevice failed. fd: " << base_path_merge_fd_
@@ -303,7 +253,6 @@
         size_t read_size = std::min(PAYLOAD_BUFFER_SZ, remaining_size);
 
         size_t total_bytes_read = 0;
-        bufsink_.ResetBufferOffset();
 
         while (read_size) {
             // We need to check every 4k block to verify if it is
@@ -314,11 +263,17 @@
                                        std::make_pair(sector, nullptr), SnapshotHandler::compare);
             bool not_found = (it == chunk_vec.end() || it->first != sector);
 
+            void* buffer = block_server_->GetResponseBuffer(BLOCK_SZ, size);
+            if (!buffer) {
+                SNAP_LOG(ERROR) << "AcquireBuffer failed in ReadAlignedSector";
+                return false;
+            }
+
             if (not_found) {
                 // Block not found in map - which means this block was not
                 // changed as per the OTA. Just route the I/O to the base
                 // device.
-                if (!ReadDataFromBaseDevice(sector, size)) {
+                if (!ReadDataFromBaseDevice(sector, buffer, size)) {
                     SNAP_LOG(ERROR) << "ReadDataFromBaseDevice failed";
                     return false;
                 }
@@ -327,25 +282,24 @@
             } else {
                 // We found the sector in mapping. Check the type of COW OP and
                 // process it.
-                if (!ProcessCowOp(it->second)) {
+                if (!ProcessCowOp(it->second, buffer)) {
                     SNAP_LOG(ERROR) << "ProcessCowOp failed";
                     return false;
                 }
 
-                ret = BLOCK_SZ;
+                ret = std::min(BLOCK_SZ, read_size);
             }
 
             read_size -= ret;
             total_bytes_read += ret;
             sector += (ret >> SECTOR_SHIFT);
-            bufsink_.UpdateBufferOffset(ret);
         }
 
-        if (!WriteDmUserPayload(total_bytes_read)) {
+        if (!SendBufferedIo()) {
             return false;
         }
 
-        SNAP_LOG(DEBUG) << "WriteDmUserPayload success total_bytes_read: " << total_bytes_read
+        SNAP_LOG(DEBUG) << "SendBufferedIo success total_bytes_read: " << total_bytes_read
                         << " remaining_size: " << remaining_size;
         remaining_size -= total_bytes_read;
     } while (remaining_size > 0);
@@ -356,40 +310,37 @@
 int ReadWorker::ReadUnalignedSector(
         sector_t sector, size_t size,
         std::vector<std::pair<sector_t, const CowOperation*>>::iterator& it) {
-    size_t skip_sector_size = 0;
-
     SNAP_LOG(DEBUG) << "ReadUnalignedSector: sector " << sector << " size: " << size
                     << " Aligned sector: " << it->first;
 
-    if (!ProcessCowOp(it->second)) {
+    int num_sectors_skip = sector - it->first;
+    size_t skip_size = num_sectors_skip << SECTOR_SHIFT;
+    size_t write_size = std::min(size, BLOCK_SZ - skip_size);
+    auto buffer =
+            reinterpret_cast<uint8_t*>(block_server_->GetResponseBuffer(BLOCK_SZ, write_size));
+    if (!buffer) {
+        SNAP_LOG(ERROR) << "ProcessCowOp failed to allocate buffer";
+        return -1;
+    }
+
+    if (!ProcessCowOp(it->second, buffer)) {
         SNAP_LOG(ERROR) << "ReadUnalignedSector: " << sector << " failed of size: " << size
                         << " Aligned sector: " << it->first;
         return -1;
     }
 
-    int num_sectors_skip = sector - it->first;
-
-    if (num_sectors_skip > 0) {
-        skip_sector_size = num_sectors_skip << SECTOR_SHIFT;
-        char* buffer = reinterpret_cast<char*>(bufsink_.GetBufPtr());
-        struct dm_user_message* msg = (struct dm_user_message*)(&(buffer[0]));
-
-        if (skip_sector_size == BLOCK_SZ) {
+    if (skip_size) {
+        if (skip_size == BLOCK_SZ) {
             SNAP_LOG(ERROR) << "Invalid un-aligned IO request at sector: " << sector
                             << " Base-sector: " << it->first;
             return -1;
         }
-
-        memmove(msg->payload.buf, (char*)msg->payload.buf + skip_sector_size,
-                (BLOCK_SZ - skip_sector_size));
+        memmove(buffer, buffer + skip_size, write_size);
     }
-
-    bufsink_.ResetBufferOffset();
-    return std::min(size, (BLOCK_SZ - skip_sector_size));
+    return write_size;
 }
 
 bool ReadWorker::ReadUnalignedSector(sector_t sector, size_t size) {
-    bufsink_.ResetBufferOffset();
     std::vector<std::pair<sector_t, const CowOperation*>>& chunk_vec = snapuserd_->GetChunkVec();
 
     auto it = std::lower_bound(chunk_vec.begin(), chunk_vec.end(), std::make_pair(sector, nullptr),
@@ -458,7 +409,6 @@
     // requested offset in this case is beyond the last mapped COW op size (which
     // is block 1 in this case).
 
-    size_t total_bytes_read = 0;
     size_t remaining_size = size;
     int ret = 0;
     if (!merge_complete && (requested_offset >= final_offset) &&
@@ -472,11 +422,10 @@
         }
 
         remaining_size -= ret;
-        total_bytes_read += ret;
         sector += (ret >> SECTOR_SHIFT);
 
         // Send the data back
-        if (!WriteDmUserPayload(total_bytes_read)) {
+        if (!SendBufferedIo()) {
             return false;
         }
 
@@ -494,26 +443,21 @@
         // Find the diff of the aligned offset
         size_t diff_size = aligned_offset - requested_offset;
         CHECK(diff_size <= BLOCK_SZ);
-        if (remaining_size < diff_size) {
-            if (!ReadDataFromBaseDevice(sector, remaining_size)) {
-                return false;
-            }
-            total_bytes_read += remaining_size;
 
-            if (!WriteDmUserPayload(total_bytes_read)) {
-                return false;
-            }
-        } else {
-            if (!ReadDataFromBaseDevice(sector, diff_size)) {
-                return false;
-            }
+        size_t read_size = std::min(remaining_size, diff_size);
+        void* buffer = block_server_->GetResponseBuffer(BLOCK_SZ, read_size);
+        if (!buffer) {
+            SNAP_LOG(ERROR) << "AcquireBuffer failed in ReadUnalignedSector";
+            return false;
+        }
+        if (!ReadDataFromBaseDevice(sector, buffer, read_size)) {
+            return false;
+        }
+        if (!SendBufferedIo()) {
+            return false;
+        }
 
-            total_bytes_read += diff_size;
-
-            if (!WriteDmUserPayload(total_bytes_read)) {
-                return false;
-            }
-
+        if (remaining_size >= diff_size) {
             remaining_size -= diff_size;
             size_t num_sectors_read = (diff_size >> SECTOR_SHIFT);
             sector += num_sectors_read;
@@ -527,81 +471,17 @@
     return true;
 }
 
-void ReadWorker::RespondIOError() {
-    struct dm_user_header* header = bufsink_.GetHeaderPtr();
-    header->type = DM_USER_RESP_ERROR;
-    // This is an issue with the dm-user interface. There
-    // is no way to propagate the I/O error back to dm-user
-    // if we have already communicated the header back. Header
-    // is responded once at the beginning; however I/O can
-    // be processed in chunks. If we encounter an I/O error
-    // somewhere in the middle of the processing, we can't communicate
-    // this back to dm-user.
-    //
-    // TODO: Fix the interface
-    CHECK(header_response_);
-
-    WriteDmUserPayload(0);
-}
-
-bool ReadWorker::DmuserReadRequest() {
-    struct dm_user_header* header = bufsink_.GetHeaderPtr();
-
+bool ReadWorker::RequestSectors(uint64_t sector, uint64_t len) {
     // Unaligned I/O request
-    if (!IsBlockAligned(header->sector << SECTOR_SHIFT)) {
-        return ReadUnalignedSector(header->sector, header->len);
+    if (!IsBlockAligned(sector << SECTOR_SHIFT)) {
+        return ReadUnalignedSector(sector, len);
     }
 
-    return ReadAlignedSector(header->sector, header->len);
+    return ReadAlignedSector(sector, len);
 }
 
-bool ReadWorker::ProcessIORequest() {
-    // Read Header from dm-user misc device. This gives
-    // us the sector number for which IO is issued by dm-snapshot device
-    struct dm_user_header* header = bufsink_.GetHeaderPtr();
-    if (!android::base::ReadFully(ctrl_fd_, header, sizeof(*header))) {
-        if (errno != ENOTBLK) {
-            SNAP_PLOG(ERROR) << "Control-read failed";
-        }
-
-        SNAP_PLOG(DEBUG) << "ReadDmUserHeader failed....";
-        return false;
-    }
-
-    SNAP_LOG(DEBUG) << "Daemon: msg->seq: " << std::dec << header->seq;
-    SNAP_LOG(DEBUG) << "Daemon: msg->len: " << std::dec << header->len;
-    SNAP_LOG(DEBUG) << "Daemon: msg->sector: " << std::dec << header->sector;
-    SNAP_LOG(DEBUG) << "Daemon: msg->type: " << std::dec << header->type;
-    SNAP_LOG(DEBUG) << "Daemon: msg->flags: " << std::dec << header->flags;
-
-    // Use the same header buffer as the response header.
-    int request_type = header->type;
-    header->type = DM_USER_RESP_SUCCESS;
-    header_response_ = true;
-
-    bool ok;
-    switch (request_type) {
-        case DM_USER_REQ_MAP_READ:
-            ok = DmuserReadRequest();
-            break;
-
-        case DM_USER_REQ_MAP_WRITE:
-            // TODO: We should not get any write request
-            // to dm-user as we mount all partitions
-            // as read-only. Need to verify how are TRIM commands
-            // handled during mount.
-            ok = false;
-            break;
-
-        default:
-            ok = false;
-            break;
-    }
-
-    if (!ok && header->type != DM_USER_RESP_ERROR) {
-        RespondIOError();
-    }
-    return ok;
+bool ReadWorker::SendBufferedIo() {
+    return block_server_->SendBufferedIo();
 }
 
 }  // namespace snapshot
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h
index c3a4c34..6dbae81 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h
@@ -17,41 +17,42 @@
 #include <utility>
 #include <vector>
 
+#include <snapuserd/block_server.h>
 #include "worker.h"
 
 namespace android {
 namespace snapshot {
 
-class ReadWorker : public Worker {
+class ReadWorker : public Worker, public IBlockServer::Delegate {
   public:
     ReadWorker(const std::string& cow_device, const std::string& backing_device,
-               const std::string& control_device, const std::string& misc_name,
-               const std::string& base_path_merge, std::shared_ptr<SnapshotHandler> snapuserd);
+               const std::string& misc_name, const std::string& base_path_merge,
+               std::shared_ptr<SnapshotHandler> snapuserd,
+               std::shared_ptr<IBlockServerOpener> opener);
 
     bool Run();
     bool Init() override;
     void CloseFds() override;
+    bool RequestSectors(uint64_t sector, uint64_t size) override;
+
+    IBlockServer* block_server() const { return block_server_.get(); }
 
   private:
-    // Functions interacting with dm-user
-    bool ProcessIORequest();
-    bool WriteDmUserPayload(size_t size);
-    bool DmuserReadRequest();
-    void RespondIOError();
+    bool SendBufferedIo();
 
-    bool ProcessCowOp(const CowOperation* cow_op);
-    bool ProcessXorOp(const CowOperation* cow_op);
-    bool ProcessOrderedOp(const CowOperation* cow_op);
-    bool ProcessCopyOp(const CowOperation* cow_op);
-    bool ProcessReplaceOp(const CowOperation* cow_op);
-    bool ProcessZeroOp();
+    bool ProcessCowOp(const CowOperation* cow_op, void* buffer);
+    bool ProcessXorOp(const CowOperation* cow_op, void* buffer);
+    bool ProcessOrderedOp(const CowOperation* cow_op, void* buffer);
+    bool ProcessCopyOp(const CowOperation* cow_op, void* buffer);
+    bool ProcessReplaceOp(const CowOperation* cow_op, void* buffer);
+    bool ProcessZeroOp(void* buffer);
 
     bool ReadAlignedSector(sector_t sector, size_t sz);
     bool ReadUnalignedSector(sector_t sector, size_t size);
     int ReadUnalignedSector(sector_t sector, size_t size,
                             std::vector<std::pair<sector_t, const CowOperation*>>::iterator& it);
-    bool ReadFromSourceDevice(const CowOperation* cow_op);
-    bool ReadDataFromBaseDevice(sector_t sector, size_t read_size);
+    bool ReadFromSourceDevice(const CowOperation* cow_op, void* buffer);
+    bool ReadDataFromBaseDevice(sector_t sector, void* buffer, size_t read_size);
 
     constexpr bool IsBlockAligned(size_t size) { return ((size & (BLOCK_SZ - 1)) == 0); }
     constexpr sector_t ChunkToSector(chunk_t chunk) { return chunk << CHUNK_SHIFT; }
@@ -59,11 +60,10 @@
     std::string backing_store_device_;
     unique_fd backing_store_fd_;
 
-    std::string control_device_;
-    unique_fd ctrl_fd_;
+    std::shared_ptr<IBlockServerOpener> block_server_opener_;
+    std::unique_ptr<IBlockServer> block_server_;
 
-    XorSink xorsink_;
-    bool header_response_ = false;
+    std::basic_string<uint8_t> xor_buffer_;
 };
 
 }  // namespace snapshot
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
index e52d752..c295851 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
@@ -22,9 +22,10 @@
 #include <android-base/properties.h>
 #include <android-base/scopeguard.h>
 #include <android-base/strings.h>
+#include <snapuserd/dm_user_block_server.h>
 
+#include "merge_worker.h"
 #include "read_worker.h"
-#include "snapuserd_merge.h"
 
 namespace android {
 namespace snapshot {
@@ -35,12 +36,12 @@
 
 SnapshotHandler::SnapshotHandler(std::string misc_name, std::string cow_device,
                                  std::string backing_device, std::string base_path_merge,
-                                 int num_worker_threads, bool use_iouring,
-                                 bool perform_verification) {
+                                 std::shared_ptr<IBlockServerOpener> opener, int num_worker_threads,
+                                 bool use_iouring, bool perform_verification) {
     misc_name_ = std::move(misc_name);
     cow_device_ = std::move(cow_device);
     backing_store_device_ = std::move(backing_device);
-    control_device_ = "/dev/dm-user/" + misc_name_;
+    block_server_opener_ = std::move(opener);
     base_path_merge_ = std::move(base_path_merge);
     num_worker_threads_ = num_worker_threads;
     is_io_uring_enabled_ = use_iouring;
@@ -49,8 +50,9 @@
 
 bool SnapshotHandler::InitializeWorkers() {
     for (int i = 0; i < num_worker_threads_; i++) {
-        auto wt = std::make_unique<ReadWorker>(cow_device_, backing_store_device_, control_device_,
-                                               misc_name_, base_path_merge_, GetSharedPtr());
+        auto wt = std::make_unique<ReadWorker>(cow_device_, backing_store_device_, misc_name_,
+                                               base_path_merge_, GetSharedPtr(),
+                                               block_server_opener_);
         if (!wt->Init()) {
             SNAP_LOG(ERROR) << "Thread initialization failed";
             return false;
@@ -280,20 +282,6 @@
         return false;
     }
 
-    unique_fd fd(TEMP_FAILURE_RETRY(open(base_path_merge_.c_str(), O_RDONLY | O_CLOEXEC)));
-    if (fd < 0) {
-        SNAP_LOG(ERROR) << "Cannot open block device";
-        return false;
-    }
-
-    uint64_t dev_sz = get_block_device_size(fd.get());
-    if (!dev_sz) {
-        SNAP_LOG(ERROR) << "Failed to find block device size: " << base_path_merge_;
-        return false;
-    }
-
-    num_sectors_ = dev_sz >> SECTOR_SHIFT;
-
     return ReadMetadata();
 }
 
@@ -307,8 +295,6 @@
     if (ra_thread_) {
         ra_thread_status =
                 std::async(std::launch::async, &ReadAhead::RunThread, read_ahead_thread_.get());
-
-        SNAP_LOG(INFO) << "Read-ahead thread started...";
     }
 
     // Launch worker threads
@@ -460,5 +446,21 @@
     merge_thread_ = nullptr;
 }
 
+uint64_t SnapshotHandler::GetNumSectors() const {
+    unique_fd fd(TEMP_FAILURE_RETRY(open(base_path_merge_.c_str(), O_RDONLY | O_CLOEXEC)));
+    if (fd < 0) {
+        SNAP_LOG(ERROR) << "Cannot open base path: " << base_path_merge_;
+        return false;
+    }
+
+    uint64_t dev_sz = get_block_device_size(fd.get());
+    if (!dev_sz) {
+        SNAP_LOG(ERROR) << "Failed to find block device size: " << base_path_merge_;
+        return false;
+    }
+
+    return dev_sz / SECTOR_SIZE;
+}
+
 }  // namespace snapshot
 }  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
index cdc38c0..622fc50 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
@@ -28,6 +28,7 @@
 #include <iostream>
 #include <limits>
 #include <mutex>
+#include <ostream>
 #include <string>
 #include <thread>
 #include <unordered_map>
@@ -43,6 +44,7 @@
 #include <libsnapshot/cow_reader.h>
 #include <libsnapshot/cow_writer.h>
 #include <liburing.h>
+#include <snapuserd/block_server.h>
 #include <snapuserd/snapuserd_buffer.h>
 #include <snapuserd/snapuserd_kernel.h>
 #include <storage_literals/storage_literals.h>
@@ -67,12 +69,13 @@
 #define SNAP_PLOG(level) PLOG(level) << misc_name_ << ": "
 
 enum class MERGE_IO_TRANSITION {
+    INVALID,
     MERGE_READY,
     MERGE_BEGIN,
     MERGE_FAILED,
     MERGE_COMPLETE,
     IO_TERMINATED,
-    READ_AHEAD_FAILURE,
+    READ_AHEAD_FAILURE
 };
 
 class MergeWorker;
@@ -102,14 +105,14 @@
 class SnapshotHandler : public std::enable_shared_from_this<SnapshotHandler> {
   public:
     SnapshotHandler(std::string misc_name, std::string cow_device, std::string backing_device,
-                    std::string base_path_merge, int num_workers, bool use_iouring,
-                    bool perform_verification);
+                    std::string base_path_merge, std::shared_ptr<IBlockServerOpener> opener,
+                    int num_workers, bool use_iouring, bool perform_verification);
     bool InitCowDevice();
     bool Start();
 
     const std::string& GetControlDevicePath() { return control_device_; }
     const std::string& GetMiscName() { return misc_name_; }
-    const uint64_t& GetNumSectors() { return num_sectors_; }
+    uint64_t GetNumSectors() const;
     const bool& IsAttached() const { return attached_; }
     void AttachControlDevice() { attached_ = true; }
 
@@ -202,8 +205,6 @@
 
     unique_fd cow_fd_;
 
-    uint64_t num_sectors_;
-
     std::unique_ptr<CowReader> reader_;
 
     // chunk_vec stores the pseudo mapping of sector
@@ -221,7 +222,7 @@
     bool populate_data_from_cow_ = false;
     bool ra_thread_ = false;
     int total_ra_blocks_merged_ = 0;
-    MERGE_IO_TRANSITION io_state_;
+    MERGE_IO_TRANSITION io_state_ = MERGE_IO_TRANSITION::INVALID;
     std::unique_ptr<ReadAhead> read_ahead_thread_;
     std::unordered_map<uint64_t, void*> read_ahead_buffer_map_;
 
@@ -244,7 +245,10 @@
 
     std::unique_ptr<struct io_uring> ring_;
     std::unique_ptr<UpdateVerify> update_verify_;
+    std::shared_ptr<IBlockServerOpener> block_server_opener_;
 };
 
+std::ostream& operator<<(std::ostream& os, MERGE_IO_TRANSITION value);
+
 }  // namespace snapshot
 }  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp
index 399f7b8..d2128c5 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp
@@ -16,7 +16,10 @@
 
 #include "snapuserd_readahead.h"
 
+#include <pthread.h>
+
 #include "snapuserd_core.h"
+#include "utility.h"
 
 namespace android {
 namespace snapshot {
@@ -427,7 +430,7 @@
         // will fallback to synchronous I/O.
         int ret = io_uring_wait_cqe(ring_.get(), &cqe);
         if (ret) {
-            SNAP_LOG(ERROR) << "Read-ahead - io_uring_wait_cqe failed: " << ret;
+            SNAP_LOG(ERROR) << "Read-ahead - io_uring_wait_cqe failed: " << strerror(-ret);
             status = false;
             break;
         }
@@ -492,7 +495,7 @@
         if (xor_op_index < xor_op_vec.size()) {
             const CowOperation* xor_op = xor_op_vec[xor_op_index];
             if (xor_op->new_block == new_block) {
-                void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
+                void* buffer = bufsink_.AcquireBuffer(BLOCK_SZ);
                 if (!buffer) {
                     SNAP_LOG(ERROR) << "ReadAhead - failed to allocate buffer for block: "
                                     << xor_op->new_block;
@@ -506,7 +509,6 @@
                 }
 
                 xor_op_index += 1;
-                bufsink_.UpdateBufferOffset(BLOCK_SZ);
             }
         }
         block_index += 1;
@@ -593,7 +595,7 @@
             // Check if this block is an XOR op
             if (xor_op->new_block == new_block) {
                 // Read the xor'ed data from COW
-                void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
+                void* buffer = bufsink.GetPayloadBuffer(BLOCK_SZ);
                 if (!buffer) {
                     SNAP_LOG(ERROR) << "ReadAhead - failed to allocate buffer";
                     return false;
@@ -691,6 +693,7 @@
     // window. If there is a crash during this time frame, merge should resume
     // based on the contents of the scratch space.
     if (!snapuserd_->WaitForMergeReady()) {
+        SNAP_LOG(ERROR) << "ReadAhead failed to wait for merge ready";
         return false;
     }
 
@@ -752,6 +755,10 @@
 }
 
 bool ReadAhead::RunThread() {
+    SNAP_LOG(INFO) << "ReadAhead thread started.";
+
+    pthread_setname_np(pthread_self(), "ReadAhead");
+
     if (!InitializeFds()) {
         return false;
     }
@@ -766,10 +773,11 @@
 
     InitializeIouring();
 
-    if (setpriority(PRIO_PROCESS, gettid(), kNiceValueForMergeThreads)) {
-        SNAP_PLOG(ERROR) << "Failed to set priority for TID: " << gettid();
+    if (!SetThreadPriority(kNiceValueForMergeThreads)) {
+        SNAP_PLOG(ERROR) << "Failed to set thread priority";
     }
 
+    SNAP_LOG(INFO) << "ReadAhead processing.";
     while (!RAIterDone()) {
         if (!ReadAheadIOStart()) {
             break;
@@ -780,7 +788,7 @@
     CloseFds();
     reader_->CloseCowFd();
 
-    SNAP_LOG(INFO) << " ReadAhead thread terminating....";
+    SNAP_LOG(INFO) << " ReadAhead thread terminating.";
     return true;
 }
 
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
index c953f1a..13b9a00 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
@@ -31,6 +31,7 @@
 #include <android-base/scopeguard.h>
 #include <android-base/strings.h>
 #include <fs_mgr/file_wait.h>
+#include <snapuserd/dm_user_block_server.h>
 #include <snapuserd/snapuserd_client.h>
 #include "snapuserd_server.h"
 
@@ -48,6 +49,7 @@
 UserSnapshotServer::UserSnapshotServer() {
     terminating_ = false;
     handlers_ = std::make_unique<SnapshotHandlerManager>();
+    block_server_factory_ = std::make_unique<DmUserBlockServerFactory>();
 }
 
 UserSnapshotServer::~UserSnapshotServer() {
@@ -130,7 +132,12 @@
             return Sendmsg(fd, "fail");
         }
 
-        auto retval = "success," + std::to_string(handler->snapuserd()->GetNumSectors());
+        auto num_sectors = handler->snapuserd()->GetNumSectors();
+        if (!num_sectors) {
+            return Sendmsg(fd, "fail");
+        }
+
+        auto retval = "success," + std::to_string(num_sectors);
         return Sendmsg(fd, retval);
     } else if (cmd == "start") {
         // Message format:
@@ -358,8 +365,11 @@
         perform_verification = false;
     }
 
+    auto opener = block_server_factory_->CreateOpener(misc_name);
+
     return handlers_->AddHandler(misc_name, cow_device_path, backing_device, base_path_merge,
-                                 num_worker_threads, io_uring_enabled_, perform_verification);
+                                 opener, num_worker_threads, io_uring_enabled_,
+                                 perform_verification);
 }
 
 bool UserSnapshotServer::WaitForSocket() {
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h
index 988c01a..be28541 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h
@@ -31,6 +31,7 @@
 #include <vector>
 
 #include <android-base/unique_fd.h>
+#include <snapuserd/block_server.h>
 #include "handler_manager.h"
 #include "snapuserd_core.h"
 
@@ -50,6 +51,7 @@
     bool is_server_running_ = false;
     bool io_uring_enabled_ = false;
     std::unique_ptr<ISnapshotHandlerManager> handlers_;
+    std::unique_ptr<IBlockServerFactory> block_server_factory_;
 
     std::mutex lock_;
 
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
index efe0c14..01fe06f 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
@@ -17,7 +17,6 @@
 
 #include <fcntl.h>
 #include <linux/fs.h>
-#include <linux/memfd.h>
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
@@ -37,10 +36,16 @@
 #include <libdm/dm.h>
 #include <libdm/loop_control.h>
 #include <libsnapshot/cow_writer.h>
+#include <snapuserd/dm_user_block_server.h>
 #include <storage_literals/storage_literals.h>
-
 #include "handler_manager.h"
+#include "merge_worker.h"
+#include "read_worker.h"
 #include "snapuserd_core.h"
+#include "testing/dm_user_harness.h"
+#include "testing/host_harness.h"
+#include "testing/temp_device.h"
+#include "utility.h"
 
 DEFINE_string(force_config, "", "Force testing mode with iouring disabled");
 
@@ -53,186 +58,54 @@
 using namespace std::chrono_literals;
 using namespace android::dm;
 using namespace std;
+using testing::AssertionFailure;
+using testing::AssertionResult;
+using testing::AssertionSuccess;
 
-class Tempdevice {
-  public:
-    Tempdevice(const std::string& name, const DmTable& table)
-        : dm_(DeviceMapper::Instance()), name_(name), valid_(false) {
-        valid_ = dm_.CreateDevice(name, table, &path_, std::chrono::seconds(5));
-    }
-    Tempdevice(Tempdevice&& other) noexcept
-        : dm_(other.dm_), name_(other.name_), path_(other.path_), valid_(other.valid_) {
-        other.valid_ = false;
-    }
-    ~Tempdevice() {
-        if (valid_) {
-            dm_.DeleteDeviceIfExists(name_);
-        }
-    }
-    bool Destroy() {
-        if (!valid_) {
-            return true;
-        }
-        valid_ = false;
-        return dm_.DeleteDeviceIfExists(name_);
-    }
-    const std::string& path() const { return path_; }
-    const std::string& name() const { return name_; }
-    bool valid() const { return valid_; }
-
-    Tempdevice(const Tempdevice&) = delete;
-    Tempdevice& operator=(const Tempdevice&) = delete;
-
-    Tempdevice& operator=(Tempdevice&& other) noexcept {
-        name_ = other.name_;
-        valid_ = other.valid_;
-        other.valid_ = false;
-        return *this;
-    }
-
-  private:
-    DeviceMapper& dm_;
-    std::string name_;
-    std::string path_;
-    bool valid_;
-};
-
-class SnapuserdTest : public ::testing::Test {
-  public:
-    bool SetupDefault();
-    bool SetupOrderedOps();
-    bool SetupOrderedOpsInverted();
-    bool SetupCopyOverlap_1();
-    bool SetupCopyOverlap_2();
-    bool Merge();
-    void ValidateMerge();
-    void ReadSnapshotDeviceAndValidate();
-    void Shutdown();
-    void MergeInterrupt();
-    void MergeInterruptFixed(int duration);
-    void MergeInterruptRandomly(int max_duration);
-    void StartMerge();
-    void CheckMergeCompletion();
-
-    static const uint64_t kSectorSize = 512;
-
+class SnapuserdTestBase : public ::testing::Test {
   protected:
-    void SetUp() override {}
-    void TearDown() override { Shutdown(); }
-
-  private:
-    void SetupImpl();
-
-    void SimulateDaemonRestart();
-
-    std::unique_ptr<ICowWriter> CreateCowDeviceInternal();
-    void CreateCowDevice();
-    void CreateCowDeviceOrderedOps();
-    void CreateCowDeviceOrderedOpsInverted();
-    void CreateCowDeviceWithCopyOverlap_1();
-    void CreateCowDeviceWithCopyOverlap_2();
-    bool SetupDaemon();
+    void SetUp() override;
+    void TearDown() override;
     void CreateBaseDevice();
-    void InitCowDevice();
+    void CreateCowDevice();
     void SetDeviceControlName();
-    void InitDaemon();
-    void CreateDmUserDevice();
+    std::unique_ptr<ICowWriter> CreateCowDeviceInternal();
 
-    unique_ptr<LoopDevice> base_loop_;
-    unique_ptr<Tempdevice> dmuser_dev_;
-
+    std::unique_ptr<ITestHarness> harness_;
+    size_t size_ = 10_MiB;
+    int total_base_size_ = 0;
     std::string system_device_ctrl_name_;
     std::string system_device_name_;
 
+    unique_ptr<IBackingDevice> base_dev_;
     unique_fd base_fd_;
+
     std::unique_ptr<TemporaryFile> cow_system_;
+
     std::unique_ptr<uint8_t[]> orig_buffer_;
-    std::unique_ptr<uint8_t[]> merged_buffer_;
-    SnapshotHandlerManager handlers_;
-    bool setup_ok_ = false;
-    bool merge_ok_ = false;
-    size_t size_ = 100_MiB;
-    int cow_num_sectors_;
-    int total_base_size_;
 };
 
-static unique_fd CreateTempFile(const std::string& name, size_t size) {
-    unique_fd fd(syscall(__NR_memfd_create, name.c_str(), MFD_ALLOW_SEALING));
-    if (fd < 0) {
-        return {};
-    }
-    if (size) {
-        if (ftruncate(fd, size) < 0) {
-            perror("ftruncate");
-            return {};
-        }
-        if (fcntl(fd, F_ADD_SEALS, F_SEAL_GROW | F_SEAL_SHRINK) < 0) {
-            perror("fcntl");
-            return {};
-        }
-    }
-    return fd;
+void SnapuserdTestBase::SetUp() {
+#if __ANDROID__
+    harness_ = std::make_unique<DmUserTestHarness>();
+#else
+    harness_ = std::make_unique<HostTestHarness>();
+#endif
 }
 
-void SnapuserdTest::Shutdown() {
-    ASSERT_TRUE(dmuser_dev_->Destroy());
+void SnapuserdTestBase::TearDown() {}
 
-    auto misc_device = "/dev/dm-user/" + system_device_ctrl_name_;
-    ASSERT_TRUE(handlers_.DeleteHandler(system_device_ctrl_name_));
-    ASSERT_TRUE(android::fs_mgr::WaitForFileDeleted(misc_device, 10s));
-    handlers_.TerminateMergeThreads();
-}
-
-bool SnapuserdTest::SetupDefault() {
-    SetupImpl();
-    return setup_ok_;
-}
-
-bool SnapuserdTest::SetupOrderedOps() {
-    CreateBaseDevice();
-    CreateCowDeviceOrderedOps();
-    return SetupDaemon();
-}
-
-bool SnapuserdTest::SetupOrderedOpsInverted() {
-    CreateBaseDevice();
-    CreateCowDeviceOrderedOpsInverted();
-    return SetupDaemon();
-}
-
-bool SnapuserdTest::SetupCopyOverlap_1() {
-    CreateBaseDevice();
-    CreateCowDeviceWithCopyOverlap_1();
-    return SetupDaemon();
-}
-
-bool SnapuserdTest::SetupCopyOverlap_2() {
-    CreateBaseDevice();
-    CreateCowDeviceWithCopyOverlap_2();
-    return SetupDaemon();
-}
-
-bool SnapuserdTest::SetupDaemon() {
-    SetDeviceControlName();
-
-    CreateDmUserDevice();
-    InitCowDevice();
-    InitDaemon();
-
-    setup_ok_ = true;
-
-    return setup_ok_;
-}
-
-void SnapuserdTest::CreateBaseDevice() {
-    unique_fd rnd_fd;
-
+void SnapuserdTestBase::CreateBaseDevice() {
     total_base_size_ = (size_ * 5);
-    base_fd_ = CreateTempFile("base_device", total_base_size_);
+
+    base_dev_ = harness_->CreateBackingDevice(total_base_size_);
+    ASSERT_NE(base_dev_, nullptr);
+
+    base_fd_.reset(open(base_dev_->GetPath().c_str(), O_RDWR | O_CLOEXEC));
     ASSERT_GE(base_fd_, 0);
 
-    rnd_fd.reset(open("/dev/random", O_RDONLY));
-    ASSERT_TRUE(rnd_fd > 0);
+    unique_fd rnd_fd(open("/dev/random", O_RDONLY));
+    ASSERT_GE(rnd_fd, 0);
 
     std::unique_ptr<uint8_t[]> random_buffer = std::make_unique<uint8_t[]>(1_MiB);
 
@@ -242,13 +115,220 @@
     }
 
     ASSERT_EQ(lseek(base_fd_, 0, SEEK_SET), 0);
+}
 
-    base_loop_ = std::make_unique<LoopDevice>(base_fd_, 10s);
-    ASSERT_TRUE(base_loop_->valid());
+std::unique_ptr<ICowWriter> SnapuserdTestBase::CreateCowDeviceInternal() {
+    cow_system_ = std::make_unique<TemporaryFile>();
+
+    CowOptions options;
+    options.compression = "gz";
+
+    unique_fd fd(cow_system_->fd);
+    cow_system_->fd = -1;
+
+    return CreateCowWriter(kDefaultCowVersion, options, std::move(fd));
+}
+
+void SnapuserdTestBase::CreateCowDevice() {
+    unique_fd rnd_fd;
+    loff_t offset = 0;
+
+    auto writer = CreateCowDeviceInternal();
+    ASSERT_NE(writer, nullptr);
+
+    rnd_fd.reset(open("/dev/random", O_RDONLY));
+    ASSERT_TRUE(rnd_fd > 0);
+
+    std::unique_ptr<uint8_t[]> random_buffer_1_ = std::make_unique<uint8_t[]>(size_);
+
+    // Fill random data
+    for (size_t j = 0; j < (size_ / 1_MiB); j++) {
+        ASSERT_EQ(ReadFullyAtOffset(rnd_fd, (char*)random_buffer_1_.get() + offset, 1_MiB, 0),
+                  true);
+
+        offset += 1_MiB;
+    }
+
+    size_t num_blocks = size_ / writer->GetBlockSize();
+    size_t blk_end_copy = num_blocks * 2;
+    size_t source_blk = num_blocks - 1;
+    size_t blk_src_copy = blk_end_copy - 1;
+
+    uint32_t sequence[num_blocks * 2];
+    // Sequence for Copy ops
+    for (int i = 0; i < num_blocks; i++) {
+        sequence[i] = num_blocks - 1 - i;
+    }
+    // Sequence for Xor ops
+    for (int i = 0; i < num_blocks; i++) {
+        sequence[num_blocks + i] = 5 * num_blocks - 1 - i;
+    }
+    ASSERT_TRUE(writer->AddSequenceData(2 * num_blocks, sequence));
+
+    size_t x = num_blocks;
+    while (1) {
+        ASSERT_TRUE(writer->AddCopy(source_blk, blk_src_copy));
+        x -= 1;
+        if (x == 0) {
+            break;
+        }
+        source_blk -= 1;
+        blk_src_copy -= 1;
+    }
+
+    source_blk = num_blocks;
+    blk_src_copy = blk_end_copy;
+
+    ASSERT_TRUE(writer->AddRawBlocks(source_blk, random_buffer_1_.get(), size_));
+
+    size_t blk_zero_copy_start = source_blk + num_blocks;
+    size_t blk_zero_copy_end = blk_zero_copy_start + num_blocks;
+
+    ASSERT_TRUE(writer->AddZeroBlocks(blk_zero_copy_start, num_blocks));
+
+    size_t blk_random2_replace_start = blk_zero_copy_end;
+
+    ASSERT_TRUE(writer->AddRawBlocks(blk_random2_replace_start, random_buffer_1_.get(), size_));
+
+    size_t blk_xor_start = blk_random2_replace_start + num_blocks;
+    size_t xor_offset = BLOCK_SZ / 2;
+    ASSERT_TRUE(writer->AddXorBlocks(blk_xor_start, random_buffer_1_.get(), size_, num_blocks,
+                                     xor_offset));
+
+    // Flush operations
+    ASSERT_TRUE(writer->Finalize());
+    // Construct the buffer required for validation
+    orig_buffer_ = std::make_unique<uint8_t[]>(total_base_size_);
+    std::string zero_buffer(size_, 0);
+    ASSERT_EQ(android::base::ReadFullyAtOffset(base_fd_, orig_buffer_.get(), size_, size_), true);
+    memcpy((char*)orig_buffer_.get() + size_, random_buffer_1_.get(), size_);
+    memcpy((char*)orig_buffer_.get() + (size_ * 2), (void*)zero_buffer.c_str(), size_);
+    memcpy((char*)orig_buffer_.get() + (size_ * 3), random_buffer_1_.get(), size_);
+    ASSERT_EQ(android::base::ReadFullyAtOffset(base_fd_, &orig_buffer_.get()[size_ * 4], size_,
+                                               size_ + xor_offset),
+              true);
+    for (int i = 0; i < size_; i++) {
+        orig_buffer_.get()[(size_ * 4) + i] =
+                (uint8_t)(orig_buffer_.get()[(size_ * 4) + i] ^ random_buffer_1_.get()[i]);
+    }
+}
+
+void SnapuserdTestBase::SetDeviceControlName() {
+    system_device_name_.clear();
+    system_device_ctrl_name_.clear();
+
+    std::string str(cow_system_->path);
+    std::size_t found = str.find_last_of("/\\");
+    ASSERT_NE(found, std::string::npos);
+    system_device_name_ = str.substr(found + 1);
+
+    system_device_ctrl_name_ = system_device_name_ + "-ctrl";
+}
+
+class SnapuserdTest : public SnapuserdTestBase {
+  public:
+    void SetupDefault();
+    void SetupOrderedOps();
+    void SetupOrderedOpsInverted();
+    void SetupCopyOverlap_1();
+    void SetupCopyOverlap_2();
+    bool Merge();
+    void ValidateMerge();
+    void ReadSnapshotDeviceAndValidate();
+    void Shutdown();
+    void MergeInterrupt();
+    void MergeInterruptFixed(int duration);
+    void MergeInterruptRandomly(int max_duration);
+    bool StartMerge();
+    void CheckMergeCompletion();
+
+    static const uint64_t kSectorSize = 512;
+
+  protected:
+    void SetUp() override;
+    void TearDown() override;
+
+    void SetupImpl();
+
+    void SimulateDaemonRestart();
+
+    void CreateCowDeviceOrderedOps();
+    void CreateCowDeviceOrderedOpsInverted();
+    void CreateCowDeviceWithCopyOverlap_1();
+    void CreateCowDeviceWithCopyOverlap_2();
+    void SetupDaemon();
+    void InitCowDevice();
+    void InitDaemon();
+    void CreateUserDevice();
+
+    unique_ptr<IUserDevice> dmuser_dev_;
+
+    std::unique_ptr<uint8_t[]> merged_buffer_;
+    std::unique_ptr<SnapshotHandlerManager> handlers_;
+    int cow_num_sectors_;
+};
+
+void SnapuserdTest::SetUp() {
+    ASSERT_NO_FATAL_FAILURE(SnapuserdTestBase::SetUp());
+    handlers_ = std::make_unique<SnapshotHandlerManager>();
+}
+
+void SnapuserdTest::TearDown() {
+    SnapuserdTestBase::TearDown();
+    Shutdown();
+}
+
+void SnapuserdTest::Shutdown() {
+    if (dmuser_dev_) {
+        ASSERT_TRUE(dmuser_dev_->Destroy());
+    }
+
+    auto misc_device = "/dev/dm-user/" + system_device_ctrl_name_;
+    ASSERT_TRUE(handlers_->DeleteHandler(system_device_ctrl_name_));
+    ASSERT_TRUE(android::fs_mgr::WaitForFileDeleted(misc_device, 10s));
+    handlers_->TerminateMergeThreads();
+    handlers_->JoinAllThreads();
+    handlers_ = std::make_unique<SnapshotHandlerManager>();
+}
+
+void SnapuserdTest::SetupDefault() {
+    ASSERT_NO_FATAL_FAILURE(SetupImpl());
+}
+
+void SnapuserdTest::SetupOrderedOps() {
+    ASSERT_NO_FATAL_FAILURE(CreateBaseDevice());
+    ASSERT_NO_FATAL_FAILURE(CreateCowDeviceOrderedOps());
+    ASSERT_NO_FATAL_FAILURE(SetupDaemon());
+}
+
+void SnapuserdTest::SetupOrderedOpsInverted() {
+    ASSERT_NO_FATAL_FAILURE(CreateBaseDevice());
+    ASSERT_NO_FATAL_FAILURE(CreateCowDeviceOrderedOpsInverted());
+    ASSERT_NO_FATAL_FAILURE(SetupDaemon());
+}
+
+void SnapuserdTest::SetupCopyOverlap_1() {
+    ASSERT_NO_FATAL_FAILURE(CreateBaseDevice());
+    ASSERT_NO_FATAL_FAILURE(CreateCowDeviceWithCopyOverlap_1());
+    ASSERT_NO_FATAL_FAILURE(SetupDaemon());
+}
+
+void SnapuserdTest::SetupCopyOverlap_2() {
+    ASSERT_NO_FATAL_FAILURE(CreateBaseDevice());
+    ASSERT_NO_FATAL_FAILURE(CreateCowDeviceWithCopyOverlap_2());
+    ASSERT_NO_FATAL_FAILURE(SetupDaemon());
+}
+
+void SnapuserdTest::SetupDaemon() {
+    SetDeviceControlName();
+
+    ASSERT_NO_FATAL_FAILURE(CreateUserDevice());
+    ASSERT_NO_FATAL_FAILURE(InitCowDevice());
+    ASSERT_NO_FATAL_FAILURE(InitDaemon());
 }
 
 void SnapuserdTest::ReadSnapshotDeviceAndValidate() {
-    unique_fd fd(open(dmuser_dev_->path().c_str(), O_RDONLY));
+    unique_fd fd(open(dmuser_dev_->GetPath().c_str(), O_RDONLY));
     ASSERT_GE(fd, 0);
     std::unique_ptr<uint8_t[]> snapuserd_buffer = std::make_unique<uint8_t[]>(size_);
 
@@ -278,19 +358,6 @@
     ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 4), size_), 0);
 }
 
-std::unique_ptr<ICowWriter> SnapuserdTest::CreateCowDeviceInternal() {
-    std::string path = android::base::GetExecutableDirectory();
-    cow_system_ = std::make_unique<TemporaryFile>(path);
-
-    CowOptions options;
-    options.compression = "gz";
-
-    unique_fd fd(cow_system_->fd);
-    cow_system_->fd = -1;
-
-    return CreateCowWriter(kDefaultCowVersion, options, std::move(fd));
-}
-
 void SnapuserdTest::CreateCowDeviceWithCopyOverlap_2() {
     auto writer = CreateCowDeviceInternal();
     ASSERT_NE(writer, nullptr);
@@ -487,145 +554,42 @@
     }
 }
 
-void SnapuserdTest::CreateCowDevice() {
-    unique_fd rnd_fd;
-    loff_t offset = 0;
-
-    auto writer = CreateCowDeviceInternal();
-    ASSERT_NE(writer, nullptr);
-
-    rnd_fd.reset(open("/dev/random", O_RDONLY));
-    ASSERT_TRUE(rnd_fd > 0);
-
-    std::unique_ptr<uint8_t[]> random_buffer_1_ = std::make_unique<uint8_t[]>(size_);
-
-    // Fill random data
-    for (size_t j = 0; j < (size_ / 1_MiB); j++) {
-        ASSERT_EQ(ReadFullyAtOffset(rnd_fd, (char*)random_buffer_1_.get() + offset, 1_MiB, 0),
-                  true);
-
-        offset += 1_MiB;
-    }
-
-    size_t num_blocks = size_ / writer->GetBlockSize();
-    size_t blk_end_copy = num_blocks * 2;
-    size_t source_blk = num_blocks - 1;
-    size_t blk_src_copy = blk_end_copy - 1;
-
-    uint32_t sequence[num_blocks * 2];
-    // Sequence for Copy ops
-    for (int i = 0; i < num_blocks; i++) {
-        sequence[i] = num_blocks - 1 - i;
-    }
-    // Sequence for Xor ops
-    for (int i = 0; i < num_blocks; i++) {
-        sequence[num_blocks + i] = 5 * num_blocks - 1 - i;
-    }
-    ASSERT_TRUE(writer->AddSequenceData(2 * num_blocks, sequence));
-
-    size_t x = num_blocks;
-    while (1) {
-        ASSERT_TRUE(writer->AddCopy(source_blk, blk_src_copy));
-        x -= 1;
-        if (x == 0) {
-            break;
-        }
-        source_blk -= 1;
-        blk_src_copy -= 1;
-    }
-
-    source_blk = num_blocks;
-    blk_src_copy = blk_end_copy;
-
-    ASSERT_TRUE(writer->AddRawBlocks(source_blk, random_buffer_1_.get(), size_));
-
-    size_t blk_zero_copy_start = source_blk + num_blocks;
-    size_t blk_zero_copy_end = blk_zero_copy_start + num_blocks;
-
-    ASSERT_TRUE(writer->AddZeroBlocks(blk_zero_copy_start, num_blocks));
-
-    size_t blk_random2_replace_start = blk_zero_copy_end;
-
-    ASSERT_TRUE(writer->AddRawBlocks(blk_random2_replace_start, random_buffer_1_.get(), size_));
-
-    size_t blk_xor_start = blk_random2_replace_start + num_blocks;
-    size_t xor_offset = BLOCK_SZ / 2;
-    ASSERT_TRUE(writer->AddXorBlocks(blk_xor_start, random_buffer_1_.get(), size_, num_blocks,
-                                     xor_offset));
-
-    // Flush operations
-    ASSERT_TRUE(writer->Finalize());
-    // Construct the buffer required for validation
-    orig_buffer_ = std::make_unique<uint8_t[]>(total_base_size_);
-    std::string zero_buffer(size_, 0);
-    ASSERT_EQ(android::base::ReadFullyAtOffset(base_fd_, orig_buffer_.get(), size_, size_), true);
-    memcpy((char*)orig_buffer_.get() + size_, random_buffer_1_.get(), size_);
-    memcpy((char*)orig_buffer_.get() + (size_ * 2), (void*)zero_buffer.c_str(), size_);
-    memcpy((char*)orig_buffer_.get() + (size_ * 3), random_buffer_1_.get(), size_);
-    ASSERT_EQ(android::base::ReadFullyAtOffset(base_fd_, &orig_buffer_.get()[size_ * 4], size_,
-                                               size_ + xor_offset),
-              true);
-    for (int i = 0; i < size_; i++) {
-        orig_buffer_.get()[(size_ * 4) + i] =
-                (uint8_t)(orig_buffer_.get()[(size_ * 4) + i] ^ random_buffer_1_.get()[i]);
-    }
-}
-
 void SnapuserdTest::InitCowDevice() {
     bool use_iouring = true;
     if (FLAGS_force_config == "iouring_disabled") {
         use_iouring = false;
     }
 
+    auto factory = harness_->GetBlockServerFactory();
+    auto opener = factory->CreateOpener(system_device_ctrl_name_);
     auto handler =
-            handlers_.AddHandler(system_device_ctrl_name_, cow_system_->path, base_loop_->device(),
-                                 base_loop_->device(), 1, use_iouring, false);
+            handlers_->AddHandler(system_device_ctrl_name_, cow_system_->path, base_dev_->GetPath(),
+                                  base_dev_->GetPath(), opener, 1, use_iouring, false);
     ASSERT_NE(handler, nullptr);
     ASSERT_NE(handler->snapuserd(), nullptr);
+#ifdef __ANDROID__
     ASSERT_NE(handler->snapuserd()->GetNumSectors(), 0);
+#endif
 }
 
-void SnapuserdTest::SetDeviceControlName() {
-    system_device_name_.clear();
-    system_device_ctrl_name_.clear();
-
-    std::string str(cow_system_->path);
-    std::size_t found = str.find_last_of("/\\");
-    ASSERT_NE(found, std::string::npos);
-    system_device_name_ = str.substr(found + 1);
-
-    system_device_ctrl_name_ = system_device_name_ + "-ctrl";
-}
-
-void SnapuserdTest::CreateDmUserDevice() {
-    unique_fd fd(TEMP_FAILURE_RETRY(open(base_loop_->device().c_str(), O_RDONLY | O_CLOEXEC)));
-    ASSERT_TRUE(fd > 0);
-
-    uint64_t dev_sz = get_block_device_size(fd.get());
-    ASSERT_TRUE(dev_sz > 0);
+void SnapuserdTest::CreateUserDevice() {
+    auto dev_sz = base_dev_->GetSize();
+    ASSERT_NE(dev_sz, 0);
 
     cow_num_sectors_ = dev_sz >> 9;
 
-    DmTable dmuser_table;
-    ASSERT_TRUE(dmuser_table.AddTarget(
-            std::make_unique<DmTargetUser>(0, cow_num_sectors_, system_device_ctrl_name_)));
-    ASSERT_TRUE(dmuser_table.valid());
-
-    dmuser_dev_ = std::make_unique<Tempdevice>(system_device_name_, dmuser_table);
-    ASSERT_TRUE(dmuser_dev_->valid());
-    ASSERT_FALSE(dmuser_dev_->path().empty());
-
-    auto misc_device = "/dev/dm-user/" + system_device_ctrl_name_;
-    ASSERT_TRUE(android::fs_mgr::WaitForFile(misc_device, 10s));
+    dmuser_dev_ = harness_->CreateUserDevice(system_device_name_, system_device_ctrl_name_,
+                                             cow_num_sectors_);
+    ASSERT_NE(dmuser_dev_, nullptr);
 }
 
 void SnapuserdTest::InitDaemon() {
-    ASSERT_TRUE(handlers_.StartHandler(system_device_ctrl_name_));
+    ASSERT_TRUE(handlers_->StartHandler(system_device_ctrl_name_));
 }
 
 void SnapuserdTest::CheckMergeCompletion() {
     while (true) {
-        double percentage = handlers_.GetMergePercentage();
+        double percentage = handlers_->GetMergePercentage();
         if ((int)percentage == 100) {
             break;
         }
@@ -635,27 +599,26 @@
 }
 
 void SnapuserdTest::SetupImpl() {
-    CreateBaseDevice();
-    CreateCowDevice();
+    ASSERT_NO_FATAL_FAILURE(CreateBaseDevice());
+    ASSERT_NO_FATAL_FAILURE(CreateCowDevice());
 
     SetDeviceControlName();
 
-    CreateDmUserDevice();
-    InitCowDevice();
-    InitDaemon();
-
-    setup_ok_ = true;
+    ASSERT_NO_FATAL_FAILURE(CreateUserDevice());
+    ASSERT_NO_FATAL_FAILURE(InitCowDevice());
+    ASSERT_NO_FATAL_FAILURE(InitDaemon());
 }
 
 bool SnapuserdTest::Merge() {
-    StartMerge();
+    if (!StartMerge()) {
+        return false;
+    }
     CheckMergeCompletion();
-    merge_ok_ = true;
-    return merge_ok_;
+    return true;
 }
 
-void SnapuserdTest::StartMerge() {
-    ASSERT_TRUE(handlers_.InitiateMerge(system_device_ctrl_name_));
+bool SnapuserdTest::StartMerge() {
+    return handlers_->InitiateMerge(system_device_ctrl_name_);
 }
 
 void SnapuserdTest::ValidateMerge() {
@@ -666,158 +629,260 @@
 }
 
 void SnapuserdTest::SimulateDaemonRestart() {
-    Shutdown();
+    ASSERT_NO_FATAL_FAILURE(Shutdown());
     std::this_thread::sleep_for(500ms);
     SetDeviceControlName();
-    CreateDmUserDevice();
-    InitCowDevice();
-    InitDaemon();
+    ASSERT_NO_FATAL_FAILURE(CreateUserDevice());
+    ASSERT_NO_FATAL_FAILURE(InitCowDevice());
+    ASSERT_NO_FATAL_FAILURE(InitDaemon());
 }
 
 void SnapuserdTest::MergeInterruptRandomly(int max_duration) {
     std::srand(std::time(nullptr));
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
 
     for (int i = 0; i < 20; i++) {
         int duration = std::rand() % max_duration;
         std::this_thread::sleep_for(std::chrono::milliseconds(duration));
-        SimulateDaemonRestart();
-        StartMerge();
+        ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
+        ASSERT_TRUE(StartMerge());
     }
 
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
     ASSERT_TRUE(Merge());
 }
 
 void SnapuserdTest::MergeInterruptFixed(int duration) {
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
 
     for (int i = 0; i < 25; i++) {
         std::this_thread::sleep_for(std::chrono::milliseconds(duration));
-        SimulateDaemonRestart();
-        StartMerge();
+        ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
+        ASSERT_TRUE(StartMerge());
     }
 
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
     ASSERT_TRUE(Merge());
 }
 
 void SnapuserdTest::MergeInterrupt() {
     // Interrupt merge at various intervals
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
     std::this_thread::sleep_for(250ms);
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
 
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
     std::this_thread::sleep_for(250ms);
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
 
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
     std::this_thread::sleep_for(150ms);
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
 
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
     std::this_thread::sleep_for(100ms);
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
 
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
     std::this_thread::sleep_for(800ms);
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
 
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
     std::this_thread::sleep_for(600ms);
-    SimulateDaemonRestart();
+    ASSERT_NO_FATAL_FAILURE(SimulateDaemonRestart());
 
     ASSERT_TRUE(Merge());
 }
 
 TEST_F(SnapuserdTest, Snapshot_IO_TEST) {
-    ASSERT_TRUE(SetupDefault());
+    if (!harness_->HasUserDevice()) {
+        GTEST_SKIP() << "Skipping snapshot read; not supported";
+    }
+    ASSERT_NO_FATAL_FAILURE(SetupDefault());
     // I/O before merge
-    ReadSnapshotDeviceAndValidate();
+    ASSERT_NO_FATAL_FAILURE(ReadSnapshotDeviceAndValidate());
     ASSERT_TRUE(Merge());
     ValidateMerge();
     // I/O after merge - daemon should read directly
     // from base device
-    ReadSnapshotDeviceAndValidate();
-    Shutdown();
+    ASSERT_NO_FATAL_FAILURE(ReadSnapshotDeviceAndValidate());
 }
 
 TEST_F(SnapuserdTest, Snapshot_MERGE_IO_TEST) {
-    ASSERT_TRUE(SetupDefault());
+    if (!harness_->HasUserDevice()) {
+        GTEST_SKIP() << "Skipping snapshot read; not supported";
+    }
+    ASSERT_NO_FATAL_FAILURE(SetupDefault());
     // Issue I/O before merge begins
     std::async(std::launch::async, &SnapuserdTest::ReadSnapshotDeviceAndValidate, this);
     // Start the merge
     ASSERT_TRUE(Merge());
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_MERGE_IO_TEST_1) {
-    ASSERT_TRUE(SetupDefault());
+    if (!harness_->HasUserDevice()) {
+        GTEST_SKIP() << "Skipping snapshot read; not supported";
+    }
+    ASSERT_NO_FATAL_FAILURE(SetupDefault());
     // Start the merge
-    StartMerge();
+    ASSERT_TRUE(StartMerge());
     // Issue I/O in parallel when merge is in-progress
     std::async(std::launch::async, &SnapuserdTest::ReadSnapshotDeviceAndValidate, this);
     CheckMergeCompletion();
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_Merge_Resume) {
-    ASSERT_TRUE(SetupDefault());
-    MergeInterrupt();
+    ASSERT_NO_FATAL_FAILURE(SetupDefault());
+    ASSERT_NO_FATAL_FAILURE(MergeInterrupt());
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_COPY_Overlap_TEST_1) {
-    ASSERT_TRUE(SetupCopyOverlap_1());
+    ASSERT_NO_FATAL_FAILURE(SetupCopyOverlap_1());
     ASSERT_TRUE(Merge());
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_COPY_Overlap_TEST_2) {
-    ASSERT_TRUE(SetupCopyOverlap_2());
+    ASSERT_NO_FATAL_FAILURE(SetupCopyOverlap_2());
     ASSERT_TRUE(Merge());
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_COPY_Overlap_Merge_Resume_TEST) {
-    ASSERT_TRUE(SetupCopyOverlap_1());
-    MergeInterrupt();
+    ASSERT_NO_FATAL_FAILURE(SetupCopyOverlap_1());
+    ASSERT_NO_FATAL_FAILURE(MergeInterrupt());
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_Merge_Crash_Fixed_Ordered) {
-    ASSERT_TRUE(SetupOrderedOps());
-    MergeInterruptFixed(300);
+    ASSERT_NO_FATAL_FAILURE(SetupOrderedOps());
+    ASSERT_NO_FATAL_FAILURE(MergeInterruptFixed(300));
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_Merge_Crash_Random_Ordered) {
-    ASSERT_TRUE(SetupOrderedOps());
-    MergeInterruptRandomly(500);
+    ASSERT_NO_FATAL_FAILURE(SetupOrderedOps());
+    ASSERT_NO_FATAL_FAILURE(MergeInterruptRandomly(500));
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_Merge_Crash_Fixed_Inverted) {
-    ASSERT_TRUE(SetupOrderedOpsInverted());
-    MergeInterruptFixed(50);
+    ASSERT_NO_FATAL_FAILURE(SetupOrderedOpsInverted());
+    ASSERT_NO_FATAL_FAILURE(MergeInterruptFixed(50));
     ValidateMerge();
-    Shutdown();
 }
 
 TEST_F(SnapuserdTest, Snapshot_Merge_Crash_Random_Inverted) {
-    ASSERT_TRUE(SetupOrderedOpsInverted());
-    MergeInterruptRandomly(50);
+    ASSERT_NO_FATAL_FAILURE(SetupOrderedOpsInverted());
+    ASSERT_NO_FATAL_FAILURE(MergeInterruptRandomly(50));
     ValidateMerge();
-    Shutdown();
+}
+
+class HandlerTest : public SnapuserdTestBase {
+  protected:
+    void SetUp() override;
+    void TearDown() override;
+
+    AssertionResult ReadSectors(sector_t sector, uint64_t size, void* buffer);
+
+    TestBlockServerFactory factory_;
+    std::shared_ptr<TestBlockServerOpener> opener_;
+    std::shared_ptr<SnapshotHandler> handler_;
+    std::unique_ptr<ReadWorker> read_worker_;
+    TestBlockServer* block_server_;
+    std::future<bool> handler_thread_;
+};
+
+void HandlerTest::SetUp() {
+    ASSERT_NO_FATAL_FAILURE(SnapuserdTestBase::SetUp());
+    ASSERT_NO_FATAL_FAILURE(CreateBaseDevice());
+    ASSERT_NO_FATAL_FAILURE(CreateCowDevice());
+    ASSERT_NO_FATAL_FAILURE(SetDeviceControlName());
+
+    opener_ = factory_.CreateTestOpener(system_device_ctrl_name_);
+    ASSERT_NE(opener_, nullptr);
+
+    handler_ = std::make_shared<SnapshotHandler>(system_device_ctrl_name_, cow_system_->path,
+                                                 base_dev_->GetPath(), base_dev_->GetPath(),
+                                                 opener_, 1, false, false);
+    ASSERT_TRUE(handler_->InitCowDevice());
+    ASSERT_TRUE(handler_->InitializeWorkers());
+
+    read_worker_ = std::make_unique<ReadWorker>(cow_system_->path, base_dev_->GetPath(),
+                                                system_device_ctrl_name_, base_dev_->GetPath(),
+                                                handler_->GetSharedPtr(), opener_);
+    ASSERT_TRUE(read_worker_->Init());
+    block_server_ = static_cast<TestBlockServer*>(read_worker_->block_server());
+
+    handler_thread_ = std::async(std::launch::async, &SnapshotHandler::Start, handler_.get());
+}
+
+void HandlerTest::TearDown() {
+    ASSERT_TRUE(factory_.DeleteQueue(system_device_ctrl_name_));
+    ASSERT_TRUE(handler_thread_.get());
+    SnapuserdTestBase::TearDown();
+}
+
+AssertionResult HandlerTest::ReadSectors(sector_t sector, uint64_t size, void* buffer) {
+    if (!read_worker_->RequestSectors(sector, size)) {
+        return AssertionFailure() << "request sectors failed";
+    }
+
+    std::string result = std::move(block_server_->sent_io());
+    if (result.size() != size) {
+        return AssertionFailure() << "size mismatch in result, got " << result.size()
+                                  << ", expected " << size;
+    }
+
+    memcpy(buffer, result.data(), size);
+    return AssertionSuccess();
+}
+
+// This test mirrors ReadSnapshotDeviceAndValidate.
+TEST_F(HandlerTest, Read) {
+    std::unique_ptr<uint8_t[]> snapuserd_buffer = std::make_unique<uint8_t[]>(size_);
+
+    // COPY
+    loff_t offset = 0;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), orig_buffer_.get(), size_), 0);
+
+    // REPLACE
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + size_, size_), 0);
+
+    // ZERO
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 2), size_), 0);
+
+    // REPLACE
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 3), size_), 0);
+
+    // XOR
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 4), size_), 0);
+}
+
+TEST_F(HandlerTest, ReadUnalignedSector) {
+    std::unique_ptr<uint8_t[]> snapuserd_buffer = std::make_unique<uint8_t[]>(BLOCK_SZ);
+
+    ASSERT_TRUE(ReadSectors(1, BLOCK_SZ, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), orig_buffer_.get() + SECTOR_SIZE, BLOCK_SZ), 0);
+}
+
+TEST_F(HandlerTest, ReadUnalignedSize) {
+    std::unique_ptr<uint8_t[]> snapuserd_buffer = std::make_unique<uint8_t[]>(SECTOR_SIZE);
+
+    ASSERT_TRUE(ReadSectors(0, SECTOR_SIZE, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), orig_buffer_.get(), SECTOR_SIZE), 0);
 }
 
 }  // namespace snapshot
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp
index 28c9f68..52e4f89 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp
@@ -199,6 +199,7 @@
 
             if (io_state_ == MERGE_IO_TRANSITION::READ_AHEAD_FAILURE ||
                 io_state_ == MERGE_IO_TRANSITION::IO_TERMINATED) {
+                SNAP_LOG(ERROR) << "WaitForMergeBegin failed with state: " << io_state_;
                 return false;
             }
         }
@@ -211,6 +212,7 @@
 
         if (io_state_ == MERGE_IO_TRANSITION::READ_AHEAD_FAILURE ||
             io_state_ == MERGE_IO_TRANSITION::IO_TERMINATED) {
+            SNAP_LOG(ERROR) << "WaitForMergeBegin failed with state: " << io_state_;
             return false;
         }
 
@@ -277,6 +279,7 @@
         if (io_state_ == MERGE_IO_TRANSITION::MERGE_FAILED ||
             io_state_ == MERGE_IO_TRANSITION::MERGE_COMPLETE ||
             io_state_ == MERGE_IO_TRANSITION::IO_TERMINATED) {
+            SNAP_LOG(ERROR) << "Wait for merge ready failed: " << io_state_;
             return false;
         }
         return true;
@@ -668,5 +671,26 @@
     }
 }
 
+std::ostream& operator<<(std::ostream& os, MERGE_IO_TRANSITION value) {
+    switch (value) {
+        case MERGE_IO_TRANSITION::INVALID:
+            return os << "INVALID";
+        case MERGE_IO_TRANSITION::MERGE_READY:
+            return os << "MERGE_READY";
+        case MERGE_IO_TRANSITION::MERGE_BEGIN:
+            return os << "MERGE_BEGIN";
+        case MERGE_IO_TRANSITION::MERGE_FAILED:
+            return os << "MERGE_FAILED";
+        case MERGE_IO_TRANSITION::MERGE_COMPLETE:
+            return os << "MERGE_COMPLETE";
+        case MERGE_IO_TRANSITION::IO_TERMINATED:
+            return os << "IO_TERMINATED";
+        case MERGE_IO_TRANSITION::READ_AHEAD_FAILURE:
+            return os << "READ_AHEAD_FAILURE";
+        default:
+            return os << "unknown";
+    }
+}
+
 }  // namespace snapshot
 }  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.cpp
index aa15630..65208fb 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.cpp
@@ -27,18 +27,7 @@
     snapuserd_ = snapuserd;
 }
 
-void Worker::InitializeBufsink() {
-    // Allocate the buffer which is used to communicate between
-    // daemon and dm-user. The buffer comprises of header and a fixed payload.
-    // If the dm-user requests a big IO, the IO will be broken into chunks
-    // of PAYLOAD_BUFFER_SZ.
-    size_t buf_size = sizeof(struct dm_user_header) + PAYLOAD_BUFFER_SZ;
-    bufsink_.Initialize(buf_size);
-}
-
 bool Worker::Init() {
-    InitializeBufsink();
-
     if (!InitializeFds()) {
         return false;
     }
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.h
index 813b159..c89d1b4 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/worker.h
@@ -40,14 +40,11 @@
     virtual bool Init();
 
   protected:
-    // Initialization
-    void InitializeBufsink();
     bool InitializeFds();
     bool InitReader();
     virtual void CloseFds() { base_path_merge_fd_ = {}; }
 
     std::unique_ptr<CowReader> reader_;
-    BufferSink bufsink_;
 
     std::string misc_name_;  // Needed for SNAP_LOG.
 
diff --git a/fs_mgr/libsnapshot/snapuserd/utility.cpp b/fs_mgr/libsnapshot/snapuserd/utility.cpp
new file mode 100644
index 0000000..a84a7c1
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/utility.cpp
@@ -0,0 +1,36 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "utility.h"
+
+#include <sys/resource.h>
+#include <unistd.h>
+
+#include <android-base/file.h>
+
+namespace android {
+namespace snapshot {
+
+using android::base::unique_fd;
+
+bool SetThreadPriority([[maybe_unused]] int priority) {
+#ifdef __ANDROID__
+    return setpriority(PRIO_PROCESS, gettid(), priority) != -1;
+#else
+    return true;
+#endif
+}
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/utility.h b/fs_mgr/libsnapshot/snapuserd/utility.h
new file mode 100644
index 0000000..58ec3e6
--- /dev/null
+++ b/fs_mgr/libsnapshot/snapuserd/utility.h
@@ -0,0 +1,23 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+namespace android {
+namespace snapshot {
+
+bool SetThreadPriority(int priority);
+
+}  // namespace snapshot
+}  // namespace android
diff --git a/fs_mgr/tests/Android.bp b/fs_mgr/tests/Android.bp
index b9bae25..2aeba0a 100644
--- a/fs_mgr/tests/Android.bp
+++ b/fs_mgr/tests/Android.bp
@@ -38,7 +38,8 @@
     ],
     static_libs: [
         "libfs_mgr",
-        "libfstab",
+        "libgmock",
+        "libgtest",
     ],
     srcs: [
         "file_wait_test.cpp",
@@ -109,7 +110,6 @@
     ],
     static_libs: [
         "libfs_mgr",
-        "libfstab",
         "libgmock",
         "libgtest",
     ],
diff --git a/fs_mgr/tests/fs_mgr_test.cpp b/fs_mgr/tests/fs_mgr_test.cpp
index 5f889ca..322bf1b 100644
--- a/fs_mgr/tests/fs_mgr_test.cpp
+++ b/fs_mgr/tests/fs_mgr_test.cpp
@@ -29,11 +29,13 @@
 #include <android-base/strings.h>
 #include <fs_mgr.h>
 #include <fstab/fstab.h>
+#include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
-#include "../fs_mgr_priv_boot_config.h"
+#include "../fs_mgr_priv.h"
 
 using namespace android::fs_mgr;
+using namespace testing;
 
 namespace {
 
@@ -119,37 +121,42 @@
         {"terminator", "truncated"},
 };
 
-const std::string bootconfig =
-        "androidboot.bootdevice = \"1d84000.ufshc\"\n"
-        "androidboot.boot_devices = \"dev1\", \"dev2,withcomma\", \"dev3\"\n"
-        "androidboot.baseband = \"sdy\"\n"
-        "androidboot.keymaster = \"1\"\n"
-        "androidboot.serialno = \"BLAHBLAHBLAH\"\n"
-        "androidboot.slot_suffix = \"_a\"\n"
-        "androidboot.hardware.platform = \"sdw813\"\n"
-        "androidboot.hardware = \"foo\"\n"
-        "androidboot.revision = \"EVT1.0\"\n"
-        "androidboot.bootloader = \"burp-0.1-7521\"\n"
-        "androidboot.hardware.sku = \"mary\"\n"
-        "androidboot.hardware.radio.subtype = \"0\"\n"
-        "androidboot.dtbo_idx = \"2\"\n"
-        "androidboot.mode = \"normal\"\n"
-        "androidboot.hardware.ddr = \"1GB,combuchi,LPDDR4X\"\n"
-        "androidboot.ddr_info = \"combuchiandroidboot.ddr_size=2GB\"\n"
-        "androidboot.hardware.ufs = \"2GB,combushi\"\n"
-        "androidboot.boottime = \"0BLE:58,1BLL:22,1BLE:571,2BLL:105,ODT:0,AVB:123\"\n"
-        "androidboot.ramdump = \"disabled\"\n"
-        "androidboot.vbmeta.device = \"PARTUUID=aa08f1a4-c7c9-402e-9a66-9707cafa9ceb\"\n"
-        "androidboot.vbmeta.avb_version = \"1.1\"\n"
-        "androidboot.vbmeta.device_state = \"unlocked\"\n"
-        "androidboot.vbmeta.hash_alg = \"sha256\"\n"
-        "androidboot.vbmeta.size = \"5248\"\n"
-        "androidboot.vbmeta.digest = \""
-        "ac13147e959861c20f2a6da97d25fe79e60e902c022a371c5c039d31e7c68860\"\n"
-        "androidboot.vbmeta.invalidate_on_error = \"yes\"\n"
-        "androidboot.veritymode = \"enforcing\"\n"
-        "androidboot.verifiedbootstate = \"orange\"\n"
-        "androidboot.space = \"sha256 5248 androidboot.nospace = nope\"\n";
+const std::string bootconfig = R"(
+androidboot.bootdevice = "1d84000.ufshc"
+androidboot.boot_devices = "dev1", "dev2,withcomma", "dev3"
+androidboot.baseband = "sdy"
+androidboot.keymaster = "1"
+androidboot.serialno = "BLAHBLAHBLAH"
+androidboot.slot_suffix = "_a"
+androidboot.hardware.platform = "sdw813"
+androidboot.hardware = "foo"
+androidboot.revision = "EVT1.0"
+androidboot.bootloader = "burp-0.1-7521"
+androidboot.hardware.sku = "mary"
+androidboot.hardware.radio.subtype = "0"
+androidboot.dtbo_idx = "2"
+androidboot.mode = "normal"
+androidboot.hardware.ddr = "1GB,combuchi,LPDDR4X"
+androidboot.ddr_info = "combuchiandroidboot.ddr_size=2GB"
+androidboot.hardware.ufs = "2GB,combushi"
+androidboot.boottime = "0BLE:58,1BLL:22,1BLE:571,2BLL:105,ODT:0,AVB:123"
+androidboot.ramdump = "disabled"
+androidboot.vbmeta.device = "PARTUUID=aa08f1a4-c7c9-402e-9a66-9707cafa9ceb"
+androidboot.vbmeta.avb_version = "1.1"
+androidboot.vbmeta.device_state = "unlocked"
+androidboot.vbmeta.hash_alg = "sha256"
+androidboot.vbmeta.size = "5248"
+androidboot.vbmeta.digest = "ac13147e959861c20f2a6da97d25fe79e60e902c022a371c5c039d31e7c68860"
+androidboot.vbmeta.invalidate_on_error = "yes"
+androidboot.veritymode = "enforcing"
+androidboot.verifiedbootstate = "orange"
+androidboot.space = "sha256 5248 androidboot.nospace = nope"
+just.key
+key.empty.value =
+dessert.value = "ice, cream"
+dessert.list = "ice", "cream"
+ambiguous.list = ", ", ", "
+)";
 
 const std::vector<std::pair<std::string, std::string>> bootconfig_result_space = {
         {"androidboot.bootdevice", "1d84000.ufshc"},
@@ -182,6 +189,11 @@
         {"androidboot.veritymode", "enforcing"},
         {"androidboot.verifiedbootstate", "orange"},
         {"androidboot.space", "sha256 5248 androidboot.nospace = nope"},
+        {"just.key", ""},
+        {"key.empty.value", ""},
+        {"dessert.value", "ice, cream"},
+        {"dessert.list", "ice,cream"},
+        {"ambiguous.list", ", ,, "},
 };
 
 bool CompareFlags(FstabEntry::FsMgrFlags& lhs, FstabEntry::FsMgrFlags& rhs) {
@@ -212,44 +224,61 @@
 
 }  // namespace
 
-TEST(fs_mgr, fs_mgr_parse_cmdline) {
-    EXPECT_EQ(result_space, fs_mgr_parse_cmdline(cmdline));
+TEST(fs_mgr, ImportKernelCmdline) {
+    std::vector<std::pair<std::string, std::string>> result;
+    ImportKernelCmdlineFromString(
+            cmdline, [&](std::string key, std::string value) { result.emplace_back(key, value); });
+    EXPECT_THAT(result, ContainerEq(result_space));
 }
 
-TEST(fs_mgr, fs_mgr_get_boot_config_from_kernel_cmdline) {
+TEST(fs_mgr, GetKernelCmdline) {
     std::string content;
-    for (const auto& entry : result_space) {
-        static constexpr char androidboot[] = "androidboot.";
-        if (!android::base::StartsWith(entry.first, androidboot)) continue;
-        auto key = entry.first.substr(strlen(androidboot));
-        EXPECT_TRUE(fs_mgr_get_boot_config_from_kernel(cmdline, key, &content)) << " for " << key;
-        EXPECT_EQ(entry.second, content);
-    }
-    EXPECT_FALSE(fs_mgr_get_boot_config_from_kernel(cmdline, "vbmeta.avb_versio", &content));
-    EXPECT_TRUE(content.empty()) << content;
-    EXPECT_FALSE(fs_mgr_get_boot_config_from_kernel(cmdline, "nospace", &content));
-    EXPECT_TRUE(content.empty()) << content;
-}
-
-TEST(fs_mgr, fs_mgr_parse_bootconfig) {
-    EXPECT_EQ(bootconfig_result_space, fs_mgr_parse_proc_bootconfig(bootconfig));
-}
-
-TEST(fs_mgr, fs_mgr_get_boot_config_from_bootconfig) {
-    std::string content;
-    for (const auto& entry : bootconfig_result_space) {
-        static constexpr char androidboot[] = "androidboot.";
-        if (!android::base::StartsWith(entry.first, androidboot)) continue;
-        auto key = entry.first.substr(strlen(androidboot));
-        EXPECT_TRUE(fs_mgr_get_boot_config_from_bootconfig(bootconfig, key, &content))
-                << " for " << key;
-        EXPECT_EQ(entry.second, content);
+    for (const auto& [key, value] : result_space) {
+        EXPECT_TRUE(GetKernelCmdlineFromString(cmdline, key, &content)) << " for " << key;
+        EXPECT_EQ(content, value);
     }
 
-    EXPECT_FALSE(fs_mgr_get_boot_config_from_bootconfig(bootconfig, "vbmeta.avb_versio", &content));
-    EXPECT_TRUE(content.empty()) << content;
-    EXPECT_FALSE(fs_mgr_get_boot_config_from_bootconfig(bootconfig, "nospace", &content));
-    EXPECT_TRUE(content.empty()) << content;
+    const std::string kUnmodifiedToken = "<UNMODIFIED>";
+    content = kUnmodifiedToken;
+    EXPECT_FALSE(GetKernelCmdlineFromString(cmdline, "", &content));
+    EXPECT_EQ(content, kUnmodifiedToken) << "output parameter shouldn't be overridden";
+
+    content = kUnmodifiedToken;
+    EXPECT_FALSE(GetKernelCmdlineFromString(cmdline, "androidboot.vbmeta.avb_versio", &content));
+    EXPECT_EQ(content, kUnmodifiedToken) << "output parameter shouldn't be overridden";
+
+    content = kUnmodifiedToken;
+    EXPECT_FALSE(GetKernelCmdlineFromString(bootconfig, "androidboot.nospace", &content));
+    EXPECT_EQ(content, kUnmodifiedToken) << "output parameter shouldn't be overridden";
+}
+
+TEST(fs_mgr, ImportBootconfig) {
+    std::vector<std::pair<std::string, std::string>> result;
+    ImportBootconfigFromString(bootconfig, [&](std::string key, std::string value) {
+        result.emplace_back(key, value);
+    });
+    EXPECT_THAT(result, ContainerEq(bootconfig_result_space));
+}
+
+TEST(fs_mgr, GetBootconfig) {
+    std::string content;
+    for (const auto& [key, value] : bootconfig_result_space) {
+        EXPECT_TRUE(GetBootconfigFromString(bootconfig, key, &content)) << " for " << key;
+        EXPECT_EQ(content, value);
+    }
+
+    const std::string kUnmodifiedToken = "<UNMODIFIED>";
+    content = kUnmodifiedToken;
+    EXPECT_FALSE(GetBootconfigFromString(bootconfig, "", &content));
+    EXPECT_EQ(content, kUnmodifiedToken) << "output parameter shouldn't be overridden";
+
+    content = kUnmodifiedToken;
+    EXPECT_FALSE(GetBootconfigFromString(bootconfig, "androidboot.vbmeta.avb_versio", &content));
+    EXPECT_EQ(content, kUnmodifiedToken) << "output parameter shouldn't be overridden";
+
+    content = kUnmodifiedToken;
+    EXPECT_FALSE(GetBootconfigFromString(bootconfig, "androidboot.nospace", &content));
+    EXPECT_EQ(content, kUnmodifiedToken) << "output parameter shouldn't be overridden";
 }
 
 TEST(fs_mgr, fs_mgr_read_fstab_file_proc_mounts) {
diff --git a/fs_mgr/tests/vts_fs_test.cpp b/fs_mgr/tests/vts_fs_test.cpp
index 4d771fa..32947b5 100644
--- a/fs_mgr/tests/vts_fs_test.cpp
+++ b/fs_mgr/tests/vts_fs_test.cpp
@@ -23,6 +23,8 @@
 #include <gtest/gtest.h>
 #include <libdm/dm.h>
 
+#include "../fs_mgr_priv.h"
+
 using testing::Contains;
 using testing::Not;
 
diff --git a/init/Android.bp b/init/Android.bp
index 1af398a..d4852d6 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -166,11 +166,9 @@
         "libbootloader_message",
         "libc++fs",
         "libcgrouprc_format",
-        "libfsverity_init",
         "liblmkd_utils",
         "liblz4",
         "libzstd",
-        "libmini_keyctl_static",
         "libmodprobe",
         "libprocinfo",
         "libprotobuf-cpp-lite",
@@ -394,6 +392,10 @@
     ],
 
     static_executable: true,
+    lto: {
+        // b/169004486 ThinLTO breaks x86 static executables.
+        never: true,
+    },
     system_shared_libs: [],
 
     cflags: [
@@ -537,6 +539,7 @@
         "libprotobuf-cpp-lite",
     ],
     static_libs: [
+        "libfs_mgr",
         "libhidl-gen-utils",
     ],
 }
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 2176233..fa5e36d 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -1297,7 +1297,6 @@
         return create_dirs.error();
     }
     auto parse_configs = ParseApexConfigs(/*apex_name=*/"");
-    ServiceList::GetInstance().MarkServicesUpdate();
     if (!parse_configs.ok()) {
         return parse_configs.error();
     }
@@ -1307,6 +1306,8 @@
         return update_linker_config.error();
     }
 
+    // Now start delayed services
+    ServiceList::GetInstance().MarkServicesUpdate();
     return {};
 }
 
diff --git a/init/devices.cpp b/init/devices.cpp
index d29ffd6..e76786a 100644
--- a/init/devices.cpp
+++ b/init/devices.cpp
@@ -32,6 +32,7 @@
 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
+#include <fs_mgr.h>
 #include <libdm/dm.h>
 #include <private/android_filesystem_config.h>
 #include <selinux/android.h>
@@ -203,8 +204,8 @@
                 partition_map.emplace_back(map_pieces[0], map_pieces[1]);
             }
         };
-        ImportKernelCmdline(parser);
-        ImportBootconfig(parser);
+        android::fs_mgr::ImportKernelCmdline(parser);
+        android::fs_mgr::ImportBootconfig(parser);
         return partition_map;
     }();
 
@@ -568,6 +569,8 @@
         return;
     } else if (uevent.subsystem == "misc" && StartsWith(uevent.device_name, "dm-user/")) {
         devpath = "/dev/dm-user/" + uevent.device_name.substr(8);
+    } else if (uevent.subsystem == "misc" && uevent.device_name == "vfio/vfio") {
+        devpath = "/dev/" + uevent.device_name;
     } else {
         devpath = "/dev/" + Basename(uevent.path);
     }
diff --git a/init/property_service.cpp b/init/property_service.cpp
index 8da6982..f5de17d 100644
--- a/init/property_service.cpp
+++ b/init/property_service.cpp
@@ -57,6 +57,7 @@
 #include <android-base/result.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
+#include <fs_mgr.h>
 #include <property_info_parser/property_info_parser.h>
 #include <property_info_serializer/property_info_serializer.h>
 #include <selinux/android.h>
@@ -1317,7 +1318,8 @@
         return;
     }
 
-    std::unique_ptr<DIR, int (*)(DIR*)> dir(opendir(get_android_dt_dir().c_str()), closedir);
+    std::unique_ptr<DIR, int (*)(DIR*)> dir(opendir(android::fs_mgr::GetAndroidDtDir().c_str()),
+                                            closedir);
     if (!dir) return;
 
     std::string dt_file;
@@ -1328,7 +1330,7 @@
             continue;
         }
 
-        std::string file_name = get_android_dt_dir() + dp->d_name;
+        std::string file_name = android::fs_mgr::GetAndroidDtDir() + dp->d_name;
 
         android::base::ReadFileToString(file_name, &dt_file);
         std::replace(dt_file.begin(), dt_file.end(), ',', '.');
@@ -1340,7 +1342,7 @@
 constexpr auto ANDROIDBOOT_PREFIX = "androidboot."sv;
 
 static void ProcessKernelCmdline() {
-    ImportKernelCmdline([&](const std::string& key, const std::string& value) {
+    android::fs_mgr::ImportKernelCmdline([&](const std::string& key, const std::string& value) {
         if (StartsWith(key, ANDROIDBOOT_PREFIX)) {
             InitPropertySet("ro.boot." + key.substr(ANDROIDBOOT_PREFIX.size()), value);
         }
@@ -1349,7 +1351,7 @@
 
 
 static void ProcessBootconfig() {
-    ImportBootconfig([&](const std::string& key, const std::string& value) {
+    android::fs_mgr::ImportBootconfig([&](const std::string& key, const std::string& value) {
         if (StartsWith(key, ANDROIDBOOT_PREFIX)) {
             InitPropertySet("ro.boot." + key.substr(ANDROIDBOOT_PREFIX.size()), value);
         }
diff --git a/init/reboot_utils.cpp b/init/reboot_utils.cpp
index e6b868e..547b186 100644
--- a/init/reboot_utils.cpp
+++ b/init/reboot_utils.cpp
@@ -27,6 +27,7 @@
 #include <android-base/properties.h>
 #include <android-base/strings.h>
 #include <cutils/android_reboot.h>
+#include <fs_mgr.h>
 #include <unwindstack/AndroidUnwinder.h>
 
 #include "capabilities.h"
@@ -48,13 +49,9 @@
 
     const std::string kInitFatalPanicParamString = "androidboot.init_fatal_panic";
     if (cmdline.find(kInitFatalPanicParamString) == std::string::npos) {
-        init_fatal_panic = false;
-        ImportBootconfig(
-                [kInitFatalPanicParamString](const std::string& key, const std::string& value) {
-                    if (key == kInitFatalPanicParamString && value == "true") {
-                        init_fatal_panic = true;
-                    }
-                });
+        std::string value;
+        init_fatal_panic = (android::fs_mgr::GetBootconfig(kInitFatalPanicParamString, &value) &&
+                            value == "true");
     } else {
         const std::string kInitFatalPanicString = kInitFatalPanicParamString + "=true";
         init_fatal_panic = cmdline.find(kInitFatalPanicString) != std::string::npos;
@@ -68,11 +65,7 @@
     const std::string kRebootTargetString = "androidboot.init_fatal_reboot_target";
     auto start_pos = cmdline.find(kRebootTargetString);
     if (start_pos == std::string::npos) {
-        ImportBootconfig([kRebootTargetString](const std::string& key, const std::string& value) {
-            if (key == kRebootTargetString) {
-                init_fatal_reboot_target = value;
-            }
-        });
+        android::fs_mgr::GetBootconfig(kRebootTargetString, &init_fatal_reboot_target);
         // We already default to bootloader if no setting is provided.
     } else {
         const std::string kRebootTargetStringPattern = kRebootTargetString + "=";
diff --git a/init/selinux.cpp b/init/selinux.cpp
index e0ef491..f34474f 100644
--- a/init/selinux.cpp
+++ b/init/selinux.cpp
@@ -74,10 +74,8 @@
 #include <android-base/unique_fd.h>
 #include <fs_avb/fs_avb.h>
 #include <fs_mgr.h>
-#include <fsverity_init.h>
 #include <libgsi/libgsi.h>
 #include <libsnapshot/snapshot.h>
-#include <mini_keyctl_utils.h>
 #include <selinux/android.h>
 #include <ziparchive/zip_archive.h>
 
@@ -103,23 +101,14 @@
 enum EnforcingStatus { SELINUX_PERMISSIVE, SELINUX_ENFORCING };
 
 EnforcingStatus StatusFromProperty() {
-    EnforcingStatus status = SELINUX_ENFORCING;
-
-    ImportKernelCmdline([&](const std::string& key, const std::string& value) {
-        if (key == "androidboot.selinux" && value == "permissive") {
-            status = SELINUX_PERMISSIVE;
-        }
-    });
-
-    if (status == SELINUX_ENFORCING) {
-        ImportBootconfig([&](const std::string& key, const std::string& value) {
-            if (key == "androidboot.selinux" && value == "permissive") {
-                status = SELINUX_PERMISSIVE;
-            }
-        });
+    std::string value;
+    if (android::fs_mgr::GetKernelCmdline("androidboot.selinux", &value) && value == "permissive") {
+        return SELINUX_PERMISSIVE;
     }
-
-    return status;
+    if (android::fs_mgr::GetBootconfig("androidboot.selinux", &value) && value == "permissive") {
+        return SELINUX_PERMISSIVE;
+    }
+    return SELINUX_ENFORCING;
 }
 
 bool IsEnforcing() {
@@ -510,7 +499,6 @@
 
 constexpr const char* kSigningCertRelease =
         "/system/etc/selinux/com.android.sepolicy.cert-release.der";
-constexpr const char* kFsVerityProcPath = "/proc/sys/fs/verity";
 const std::string kSepolicyApexMetadataDir = "/metadata/sepolicy/";
 const std::string kSepolicyApexSystemDir = "/system/etc/selinux/apex/";
 const std::string kSepolicyZip = "SEPolicy.zip";
@@ -614,24 +602,6 @@
     return {};
 }
 
-Result<void> LoadSepolicyApexCerts() {
-    key_serial_t keyring_id = android::GetKeyringId(".fs-verity");
-    if (keyring_id < 0) {
-        return Error() << "Failed to find .fs-verity keyring id";
-    }
-
-    // TODO(b/199914227) the release key should always exist. Once it's checked in, start
-    // throwing an error here if it doesn't exist.
-    if (access(kSigningCertRelease, F_OK) == 0) {
-        LoadKeyFromFile(keyring_id, "fsv_sepolicy_apex_release", kSigningCertRelease);
-    }
-    return {};
-}
-
-Result<void> SepolicyFsVerityCheck() {
-    return Error() << "TODO implement support for fsverity SEPolicy.";
-}
-
 Result<void> SepolicyCheckSignature(const std::string& dir) {
     std::string signature;
     if (!android::base::ReadFileToString(dir + kSepolicySignature, &signature)) {
@@ -654,18 +624,7 @@
     return verifySignature(sepolicyStr, signature, *releaseKey);
 }
 
-Result<void> SepolicyVerify(const std::string& dir, bool supportsFsVerity) {
-    if (supportsFsVerity) {
-        auto fsVerityCheck = SepolicyFsVerityCheck();
-        if (fsVerityCheck.ok()) {
-            return fsVerityCheck;
-        }
-        // TODO(b/199914227) If the device supports fsverity, but we fail here, we should fail to
-        // boot and not carry on. For now, fallback to a signature checkuntil the fsverity
-        // logic is implemented.
-        LOG(INFO) << "Falling back to standard signature check. " << fsVerityCheck.error();
-    }
-
+Result<void> SepolicyVerify(const std::string& dir) {
     auto sepolicySignature = SepolicyCheckSignature(dir);
     if (!sepolicySignature.ok()) {
         return Error() << "Apex SEPolicy failed signature check";
@@ -698,23 +657,19 @@
 // 6. Sets selinux into enforcing mode and continues normal booting.
 //
 void PrepareApexSepolicy() {
-    bool supportsFsVerity = access(kFsVerityProcPath, F_OK) == 0;
-    if (supportsFsVerity) {
-        auto loadSepolicyApexCerts = LoadSepolicyApexCerts();
-        if (!loadSepolicyApexCerts.ok()) {
-            // TODO(b/199914227) If the device supports fsverity, but we fail here, we should fail
-            // to boot and not carry on. For now, fallback to a signature checkuntil the fsverity
-            // logic is implemented.
-            LOG(INFO) << loadSepolicyApexCerts.error();
-        }
-    }
     // If apex sepolicy zip exists in /metadata/sepolicy, use that, otherwise use version on
-    // /system.
-    auto dir = (access((kSepolicyApexMetadataDir + kSepolicyZip).c_str(), F_OK) == 0)
-                       ? kSepolicyApexMetadataDir
-                       : kSepolicyApexSystemDir;
+    // /system. If neither exists, do nothing.
+    std::string dir;
+    if (access((kSepolicyApexMetadataDir + kSepolicyZip).c_str(), F_OK) == 0) {
+        dir = kSepolicyApexMetadataDir;
+    } else if (access((kSepolicyApexSystemDir + kSepolicyZip).c_str(), F_OK) == 0) {
+        dir = kSepolicyApexSystemDir;
+    } else {
+        LOG(INFO) << "APEX Sepolicy not found";
+        return;
+    }
 
-    auto sepolicyVerify = SepolicyVerify(dir, supportsFsVerity);
+    auto sepolicyVerify = SepolicyVerify(dir);
     if (!sepolicyVerify.ok()) {
         LOG(INFO) << "Error: " << sepolicyVerify.error();
         // If signature verification fails, fall back to version on /system.
diff --git a/init/util.cpp b/init/util.cpp
index d0478e8..e760a59 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -42,6 +42,10 @@
 #include <cutils/sockets.h>
 #include <selinux/android.h>
 
+#if defined(__ANDROID__)
+#include <fs_mgr.h>
+#endif
+
 #ifdef INIT_FULL_SOURCES
 #include <android/api-level.h>
 #include <sys/system_properties.h>
@@ -60,8 +64,6 @@
 namespace android {
 namespace init {
 
-const std::string kDefaultAndroidDtDir("/proc/device-tree/firmware/android/");
-
 const std::string kDataDirPrefix("/data/");
 
 void (*trigger_shutdown)(const std::string& command) = nullptr;
@@ -240,33 +242,6 @@
     return -1;
 }
 
-void ImportKernelCmdline(const std::function<void(const std::string&, const std::string&)>& fn) {
-    std::string cmdline;
-    android::base::ReadFileToString("/proc/cmdline", &cmdline);
-
-    for (const auto& entry : android::base::Split(android::base::Trim(cmdline), " ")) {
-        std::vector<std::string> pieces = android::base::Split(entry, "=");
-        if (pieces.size() == 2) {
-            fn(pieces[0], pieces[1]);
-        }
-    }
-}
-
-void ImportBootconfig(const std::function<void(const std::string&, const std::string&)>& fn) {
-    std::string bootconfig;
-    android::base::ReadFileToString("/proc/bootconfig", &bootconfig);
-
-    for (const auto& entry : android::base::Split(bootconfig, "\n")) {
-        std::vector<std::string> pieces = android::base::Split(entry, "=");
-        if (pieces.size() == 2) {
-            // get rid of the extra space between a list of values and remove the quotes.
-            std::string value = android::base::StringReplace(pieces[1], "\", \"", ",", true);
-            value.erase(std::remove(value.begin(), value.end(), '"'), value.end());
-            fn(android::base::Trim(pieces[0]), android::base::Trim(value));
-        }
-    }
-}
-
 bool make_dir(const std::string& path, mode_t mode) {
     std::string secontext;
     if (SelabelLookupFileContext(path, mode, &secontext) && !secontext.empty()) {
@@ -375,45 +350,18 @@
     return dst;
 }
 
-static std::string init_android_dt_dir() {
-    // Use the standard procfs-based path by default
-    std::string android_dt_dir = kDefaultAndroidDtDir;
-    // The platform may specify a custom Android DT path in kernel cmdline
-    ImportKernelCmdline([&](const std::string& key, const std::string& value) {
-        if (key == "androidboot.android_dt_dir") {
-            android_dt_dir = value;
-        }
-    });
-    // ..Or bootconfig
-    if (android_dt_dir == kDefaultAndroidDtDir) {
-        ImportBootconfig([&](const std::string& key, const std::string& value) {
-            if (key == "androidboot.android_dt_dir") {
-                android_dt_dir = value;
-            }
-        });
-    }
-
-    LOG(INFO) << "Using Android DT directory " << android_dt_dir;
-    return android_dt_dir;
-}
-
-// FIXME: The same logic is duplicated in system/core/fs_mgr/
-const std::string& get_android_dt_dir() {
-    // Set once and saves time for subsequent calls to this function
-    static const std::string kAndroidDtDir = init_android_dt_dir();
-    return kAndroidDtDir;
-}
-
 // Reads the content of device tree file under the platform's Android DT directory.
 // Returns true if the read is success, false otherwise.
 bool read_android_dt_file(const std::string& sub_path, std::string* dt_content) {
-    const std::string file_name = get_android_dt_dir() + sub_path;
+#if defined(__ANDROID__)
+    const std::string file_name = android::fs_mgr::GetAndroidDtDir() + sub_path;
     if (android::base::ReadFileToString(file_name, dt_content)) {
         if (!dt_content->empty()) {
             dt_content->pop_back();  // Trims the trailing '\0' out.
             return true;
         }
     }
+#endif
     return false;
 }
 
diff --git a/init/util.h b/init/util.h
index 3f0a4e0..2d02182 100644
--- a/init/util.h
+++ b/init/util.h
@@ -53,16 +53,11 @@
 Result<uid_t> DecodeUid(const std::string& name);
 
 bool mkdir_recursive(const std::string& pathname, mode_t mode);
-int wait_for_file(const char *filename, std::chrono::nanoseconds timeout);
-void ImportKernelCmdline(const std::function<void(const std::string&, const std::string&)>&);
-void ImportBootconfig(const std::function<void(const std::string&, const std::string&)>&);
+int wait_for_file(const char* filename, std::chrono::nanoseconds timeout);
 bool make_dir(const std::string& path, mode_t mode);
 bool is_dir(const char* pathname);
 Result<std::string> ExpandProps(const std::string& src);
 
-// Returns the platform's Android DT directory as specified in the kernel cmdline.
-// If the platform does not configure a custom DT path, returns the standard one (based in procfs).
-const std::string& get_android_dt_dir();
 // Reads or compares the content of device tree file under the platform's Android DT directory.
 bool read_android_dt_file(const std::string& sub_path, std::string* dt_content);
 bool is_android_dt_value_expected(const std::string& sub_path, const std::string& expected_content);
diff --git a/libcutils/OWNERS b/libcutils/OWNERS
index 7529cb9..e1cbe4a 100644
--- a/libcutils/OWNERS
+++ b/libcutils/OWNERS
@@ -1 +1,2 @@
+# Bug component: 128577
 include platform/system/core:/janitors/OWNERS
diff --git a/libcutils/fs_config.cpp b/libcutils/fs_config.cpp
index f90a1bc..26ac576 100644
--- a/libcutils/fs_config.cpp
+++ b/libcutils/fs_config.cpp
@@ -214,6 +214,7 @@
 #endif
     { 00755, AID_ROOT,      AID_ROOT,      0, "first_stage_ramdisk/system/bin/resize2fs" },
     { 00755, AID_ROOT,      AID_ROOT,      0, "first_stage_ramdisk/system/bin/snapuserd" },
+    { 00755, AID_ROOT,      AID_ROOT,      0, "first_stage_ramdisk/system/bin/snapuserd_ramdisk" },
     { 00755, AID_ROOT,      AID_ROOT,      0, "first_stage_ramdisk/system/bin/tune2fs" },
     { 00755, AID_ROOT,      AID_ROOT,      0, "first_stage_ramdisk/system/bin/fsck.f2fs" },
     // generic defaults
diff --git a/libcutils/include/cutils/threads.h b/libcutils/include/cutils/threads.h
index 0082c6c..9bc3429 100644
--- a/libcutils/include/cutils/threads.h
+++ b/libcutils/include/cutils/threads.h
@@ -13,28 +13,3 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
-#pragma once
-
-#include  <sys/types.h>
-
-#if defined(_WIN32)
-#include <windows.h>
-#else
-#include <pthread.h>
-#endif
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-//
-// Deprecated: use android::base::GetThreadId instead, which doesn't truncate on Mac/Windows.
-//
-#if !defined(__GLIBC__) || __GLIBC__ >= 2 && __GLIBC_MINOR__ < 32
-extern pid_t gettid();
-#endif
-
-#ifdef __cplusplus
-}
-#endif
diff --git a/libcutils/threads.cpp b/libcutils/threads.cpp
index 6ece7a3..cca50c1 100644
--- a/libcutils/threads.cpp
+++ b/libcutils/threads.cpp
@@ -14,22 +14,24 @@
 ** limitations under the License.
 */
 
-#include <cutils/threads.h>
+#include <sys/types.h>
 
 #if defined(__APPLE__)
+#include <pthread.h>
 #include <stdint.h>
 #elif defined(__linux__)
+#include <pthread.h>
 #include <syscall.h>
 #include <unistd.h>
 #elif defined(_WIN32)
 #include <windows.h>
 #endif
 
-#if defined(__BIONIC__) || defined(__GLIBC__) && __GLIBC_MINOR__ >= 32
+#if defined(__BIONIC__) || defined(__GLIBC__) && __GLIBC_MINOR__ >= 30
 // No definition needed for Android because we'll just pick up bionic's copy.
-// No definition needed for Glibc >= 2.32 because it exposes its own copy.
+// No definition needed for Glibc >= 2.30 because it exposes its own copy.
 #else
-pid_t gettid() {
+extern "C" pid_t gettid() {
 #if defined(__APPLE__)
   uint64_t tid;
   pthread_threadid_np(NULL, &tid);
diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index 06d386f..4506439 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -206,11 +206,11 @@
 }
 
 static std::string ConvertUidToPath(const char* cgroup, uid_t uid) {
-    return StringPrintf("%s/uid_%d", cgroup, uid);
+    return StringPrintf("%s/uid_%u", cgroup, uid);
 }
 
 static std::string ConvertUidPidToPath(const char* cgroup, uid_t uid, int pid) {
-    return StringPrintf("%s/uid_%d/pid_%d", cgroup, uid, pid);
+    return StringPrintf("%s/uid_%u/pid_%d", cgroup, uid, pid);
 }
 
 static int RemoveProcessGroup(const char* cgroup, uid_t uid, int pid, unsigned int retries) {
diff --git a/libprocessgroup/task_profiles.cpp b/libprocessgroup/task_profiles.cpp
index 44dba2a..f51b076 100644
--- a/libprocessgroup/task_profiles.cpp
+++ b/libprocessgroup/task_profiles.cpp
@@ -114,9 +114,26 @@
 
 IProfileAttribute::~IProfileAttribute() = default;
 
-void ProfileAttribute::Reset(const CgroupController& controller, const std::string& file_name) {
+const std::string& ProfileAttribute::file_name() const {
+    if (controller()->version() == 2 && !file_v2_name_.empty()) return file_v2_name_;
+    return file_name_;
+}
+
+void ProfileAttribute::Reset(const CgroupController& controller, const std::string& file_name,
+                             const std::string& file_v2_name) {
     controller_ = controller;
     file_name_ = file_name;
+    file_v2_name_ = file_v2_name;
+}
+
+bool ProfileAttribute::GetPathForProcess(uid_t uid, pid_t pid, std::string* path) const {
+    if (controller()->version() == 2) {
+        // all cgroup v2 attributes use the same process group hierarchy
+        *path = StringPrintf("%s/uid_%u/pid_%d/%s", controller()->path(), uid, pid,
+                             file_name().c_str());
+        return true;
+    }
+    return GetPathForTask(pid, path);
 }
 
 bool ProfileAttribute::GetPathForTask(int tid, std::string* path) const {
@@ -129,12 +146,11 @@
         return true;
     }
 
-    const std::string& file_name =
-            controller()->version() == 2 && !file_v2_name_.empty() ? file_v2_name_ : file_name_;
     if (subgroup.empty()) {
-        *path = StringPrintf("%s/%s", controller()->path(), file_name.c_str());
+        *path = StringPrintf("%s/%s", controller()->path(), file_name().c_str());
     } else {
-        *path = StringPrintf("%s/%s/%s", controller()->path(), subgroup.c_str(), file_name.c_str());
+        *path = StringPrintf("%s/%s/%s", controller()->path(), subgroup.c_str(),
+                             file_name().c_str());
     }
     return true;
 }
@@ -144,9 +160,7 @@
         return true;
     }
 
-    const std::string& file_name =
-            controller()->version() == 2 && !file_v2_name_.empty() ? file_v2_name_ : file_name_;
-    *path = StringPrintf("%s/uid_%d/%s", controller()->path(), uid, file_name.c_str());
+    *path = StringPrintf("%s/uid_%u/%s", controller()->path(), uid, file_name().c_str());
     return true;
 }
 
@@ -205,18 +219,7 @@
 
 #endif
 
-bool SetAttributeAction::ExecuteForProcess(uid_t, pid_t pid) const {
-    return ExecuteForTask(pid);
-}
-
-bool SetAttributeAction::ExecuteForTask(int tid) const {
-    std::string path;
-
-    if (!attribute_->GetPathForTask(tid, &path)) {
-        LOG(ERROR) << "Failed to find cgroup for tid " << tid;
-        return false;
-    }
-
+bool SetAttributeAction::WriteValueToFile(const std::string& path) const {
     if (!WriteStringToFile(value_, path)) {
         if (access(path.c_str(), F_OK) < 0) {
             if (optional_) {
@@ -236,6 +239,28 @@
     return true;
 }
 
+bool SetAttributeAction::ExecuteForProcess(uid_t uid, pid_t pid) const {
+    std::string path;
+
+    if (!attribute_->GetPathForProcess(uid, pid, &path)) {
+        LOG(ERROR) << "Failed to find cgroup for uid " << uid << " pid " << pid;
+        return false;
+    }
+
+    return WriteValueToFile(path);
+}
+
+bool SetAttributeAction::ExecuteForTask(int tid) const {
+    std::string path;
+
+    if (!attribute_->GetPathForTask(tid, &path)) {
+        LOG(ERROR) << "Failed to find cgroup for tid " << tid;
+        return false;
+    }
+
+    return WriteValueToFile(path);
+}
+
 bool SetAttributeAction::ExecuteForUID(uid_t uid) const {
     std::string path;
 
@@ -816,7 +841,7 @@
                 attributes_[name] =
                         std::make_unique<ProfileAttribute>(controller, file_attr, file_v2_attr);
             } else {
-                iter->second->Reset(controller, file_attr);
+                iter->second->Reset(controller, file_attr, file_v2_attr);
             }
         } else {
             LOG(WARNING) << "Controller " << controller_name << " is not found";
diff --git a/libprocessgroup/task_profiles.h b/libprocessgroup/task_profiles.h
index a62c5b0..4663f64 100644
--- a/libprocessgroup/task_profiles.h
+++ b/libprocessgroup/task_profiles.h
@@ -32,9 +32,11 @@
 class IProfileAttribute {
   public:
     virtual ~IProfileAttribute() = 0;
-    virtual void Reset(const CgroupController& controller, const std::string& file_name) = 0;
+    virtual void Reset(const CgroupController& controller, const std::string& file_name,
+                       const std::string& file_v2_name) = 0;
     virtual const CgroupController* controller() const = 0;
     virtual const std::string& file_name() const = 0;
+    virtual bool GetPathForProcess(uid_t uid, pid_t pid, std::string* path) const = 0;
     virtual bool GetPathForTask(int tid, std::string* path) const = 0;
     virtual bool GetPathForUID(uid_t uid, std::string* path) const = 0;
 };
@@ -50,9 +52,11 @@
     ~ProfileAttribute() = default;
 
     const CgroupController* controller() const override { return &controller_; }
-    const std::string& file_name() const override { return file_name_; }
-    void Reset(const CgroupController& controller, const std::string& file_name) override;
+    const std::string& file_name() const override;
+    void Reset(const CgroupController& controller, const std::string& file_name,
+               const std::string& file_v2_name) override;
 
+    bool GetPathForProcess(uid_t uid, pid_t pid, std::string* path) const override;
     bool GetPathForTask(int tid, std::string* path) const override;
     bool GetPathForUID(uid_t uid, std::string* path) const override;
 
@@ -131,6 +135,8 @@
     const IProfileAttribute* attribute_;
     std::string value_;
     bool optional_;
+
+    bool WriteValueToFile(const std::string& path) const;
 };
 
 // Set cgroup profile element
diff --git a/libprocessgroup/task_profiles_test.cpp b/libprocessgroup/task_profiles_test.cpp
index eadbe76..99d819a 100644
--- a/libprocessgroup/task_profiles_test.cpp
+++ b/libprocessgroup/task_profiles_test.cpp
@@ -102,7 +102,8 @@
   public:
     ProfileAttributeMock(const std::string& file_name) : file_name_(file_name) {}
     ~ProfileAttributeMock() override = default;
-    void Reset(const CgroupController& controller, const std::string& file_name) override {
+    void Reset(const CgroupController& controller, const std::string& file_name,
+               const std::string& file_v2_name) override {
         CHECK(false);
     }
     const CgroupController* controller() const override {
@@ -110,6 +111,9 @@
         return {};
     }
     const std::string& file_name() const override { return file_name_; }
+    bool GetPathForProcess(uid_t uid, pid_t pid, std::string* path) const override {
+        return GetPathForTask(pid, path);
+    }
     bool GetPathForTask(int tid, std::string* path) const override {
 #ifdef __ANDROID__
         CHECK(CgroupGetControllerPath(CGROUPV2_CONTROLLER_NAME, path));
@@ -125,9 +129,7 @@
         return true;
     };
 
-    bool GetPathForUID(uid_t, std::string*) const override {
-        return false;
-    }
+    bool GetPathForUID(uid_t, std::string*) const override { return false; }
 
   private:
     const std::string file_name_;
diff --git a/libstats/pull_rust/stats_pull.rs b/libstats/pull_rust/stats_pull.rs
index 09b2623..d188b5f 100644
--- a/libstats/pull_rust/stats_pull.rs
+++ b/libstats/pull_rust/stats_pull.rs
@@ -111,7 +111,9 @@
     static ref COOKIES: Mutex<HashMap<i32, fn() -> StatsPullResult>> = Mutex::new(HashMap::new());
 }
 
-// Safety: We store our callbacks in the global so they are valid.
+/// # Safety
+///
+/// `data` must be a valid pointer with no aliases.
 unsafe extern "C" fn callback_wrapper(
     atom_tag: i32,
     data: *mut AStatsEventList,
@@ -126,7 +128,8 @@
                 let stats = cb();
                 let result = stats
                     .iter()
-                    .map(|stat| stat.add_astats_event(&mut *data))
+                    // Safety: The caller promises that `data` is valid and unaliased.
+                    .map(|stat| stat.add_astats_event(unsafe { &mut *data }))
                     .collect::<Result<Vec<()>, StatsError>>();
                 match result {
                     Ok(_) => {
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index 82f5cb6..8d312b5 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -393,6 +393,11 @@
 }
 
 bool String8::removeAll(const char* other) {
+    ALOG_ASSERT(other, "String8::removeAll() requires a non-NULL string");
+
+    if (*other == '\0')
+        return true;
+
     ssize_t index = find(other);
     if (index < 0) return false;
 
diff --git a/libutils/String8_fuzz.cpp b/libutils/String8_fuzz.cpp
index faf49b6..e5dcd31 100644
--- a/libutils/String8_fuzz.cpp
+++ b/libutils/String8_fuzz.cpp
@@ -45,6 +45,8 @@
                     str1->toLower();
                 },
                 [](FuzzedDataProvider*, android::String8* str1, android::String8* str2) -> void {
+                    if (str2->size() == 0) return;
+
                     str1->removeAll(str2->c_str());
                 },
                 [](FuzzedDataProvider*, android::String8* str1, android::String8* str2) -> void {
diff --git a/libutils/String8_test.cpp b/libutils/String8_test.cpp
index 1356cd0..35fd512 100644
--- a/libutils/String8_test.cpp
+++ b/libutils/String8_test.cpp
@@ -114,3 +114,21 @@
     EXPECT_EQ(NO_MEMORY, s.append("baz", SIZE_MAX));
     EXPECT_STREQ("foobar", s);
 }
+
+TEST_F(String8Test, removeAll) {
+    String8 s("Hello, world!");
+
+    // NULL input should cause an assertion failure and error message in logcat
+    EXPECT_DEATH(s.removeAll(NULL), "");
+
+    // expect to return true and string content should remain unchanged
+    EXPECT_TRUE(s.removeAll(""));
+    EXPECT_STREQ("Hello, world!", s);
+
+    // expect to return false
+    EXPECT_FALSE(s.removeAll("x"));
+    EXPECT_STREQ("Hello, world!", s);
+
+    EXPECT_TRUE(s.removeAll("o"));
+    EXPECT_STREQ("Hell, wrld!", s);
+}
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 907f46e..8f01d93 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -997,7 +997,7 @@
     perform_apex_config
 
     # Create directories for boot animation.
-    mkdir /data/bootanim 0755 system system encryption=DeleteIfNecessary
+    mkdir /data/misc/bootanim 0755 system system encryption=DeleteIfNecessary
 
     exec_start derive_sdk
 
@@ -1021,13 +1021,9 @@
     # Must start after 'derive_classpath' to have *CLASSPATH variables set.
     start odsign
 
-    # Before we can lock keys and proceed to the next boot stage, wait for
-    # odsign to be done with the key
+    # Wait for odsign to be done with the key.
     wait_for_prop odsign.key.done 1
 
-    # Lock the fs-verity keyring, so no more keys can be added
-    exec -- /system/bin/fsverity_init --lock
-
     # Bump the boot level to 1000000000; this prevents further on-device signing.
     # This is a special value that shuts down the thread which listens for
     # further updates.
diff --git a/rootdir/ueventd.rc b/rootdir/ueventd.rc
index 0b7ffb8..60dcc2a 100644
--- a/rootdir/ueventd.rc
+++ b/rootdir/ueventd.rc
@@ -23,6 +23,11 @@
 subsystem dma_heap
    devname uevent_devpath
    dirname /dev/dma_heap
+
+subsystem vfio
+    devname uevent_devpath
+    dirname /dev/vfio
+
 # ueventd can only set permissions on device nodes and their associated
 # sysfs attributes, not on arbitrary paths.
 #
@@ -43,6 +48,7 @@
 /dev/binder               0666   root       root
 /dev/hwbinder             0666   root       root
 /dev/vndbinder            0666   root       root
+/dev/vfio/*               0666   root       root
 
 /dev/pmsg0                0222   root       log
 /dev/dma_heap/system      0444   system     system
diff --git a/trusty/keymint/Android.bp b/trusty/keymint/Android.bp
index c19ebbd..19dcc98 100644
--- a/trusty/keymint/Android.bp
+++ b/trusty/keymint/Android.bp
@@ -35,6 +35,7 @@
         "liblibc",
         "liblog_rust",
     ],
+    prefer_rlib: true,
     required: [
         "android.hardware.hardware_keystore.xml",
     ],
diff --git a/trusty/libtrusty-rs/src/lib.rs b/trusty/libtrusty-rs/src/lib.rs
index 28ea075..22b894a 100644
--- a/trusty/libtrusty-rs/src/lib.rs
+++ b/trusty/libtrusty-rs/src/lib.rs
@@ -102,6 +102,8 @@
         let file = File::options().read(true).write(true).open(device)?;
 
         let srv_name = CString::new(service).expect("Service name contained null bytes");
+        // SAFETY: The file descriptor is valid because it came from a `File`, and the name is a
+        // valid C string because it came from a `CString`.
         unsafe {
             tipc_connect(file.as_raw_fd(), srv_name.as_ptr())?;
         }
diff --git a/trusty/line-coverage/Android.bp b/trusty/line-coverage/Android.bp
new file mode 100644
index 0000000..36a73aa
--- /dev/null
+++ b/trusty/line-coverage/Android.bp
@@ -0,0 +1,36 @@
+// Copyright (C) 2023 The Android Open-Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_library {
+    name: "libtrusty_line_coverage",
+    vendor_available: true,
+    srcs: [
+        "coverage.cpp",
+    ],
+    export_include_dirs: [
+        "include",
+    ],
+    shared_libs: [
+        "libbase",
+        "libext2_uuid",
+        "liblog",
+        "libdmabufheap",
+        "libtrusty",
+    ],
+}
+
diff --git a/trusty/line-coverage/coverage.cpp b/trusty/line-coverage/coverage.cpp
new file mode 100644
index 0000000..57b7025
--- /dev/null
+++ b/trusty/line-coverage/coverage.cpp
@@ -0,0 +1,191 @@
+/*
+ * Copyright (C) 2023 The Android Open Sourete Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "line-coverage"
+
+#include <BufferAllocator/BufferAllocator.h>
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/unique_fd.h>
+#include <assert.h>
+#include <log/log.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/uio.h>
+#include <trusty/line-coverage/coverage.h>
+#include <trusty/line-coverage/tipc.h>
+#include <trusty/tipc.h>
+#include <iostream>
+
+#define LINE_COVERAGE_CLIENT_PORT "com.android.trusty.linecoverage.client"
+
+struct control {
+    /* Written by controller, read by instrumented TA */
+    uint64_t        cntrl_flags;
+
+    /* Written by instrumented TA, read by controller */
+    uint64_t        oper_flags;
+    uint64_t        write_buffer_start_count;
+    uint64_t        write_buffer_complete_count;
+};
+
+namespace android {
+namespace trusty {
+namespace line_coverage {
+
+using ::android::base::ErrnoError;
+using ::android::base::Error;
+using ::std::string;
+
+static inline uintptr_t RoundPageUp(uintptr_t val) {
+    return (val + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
+}
+
+CoverageRecord::CoverageRecord(string tipc_dev, struct uuid* uuid)
+    : tipc_dev_(std::move(tipc_dev)),
+      coverage_srv_fd_(-1),
+      uuid_(*uuid),
+      record_len_(0),
+      shm_(NULL),
+      shm_len_(0) {}
+
+CoverageRecord::~CoverageRecord() {
+    if (shm_) {
+        munmap((void*)shm_, shm_len_);
+    }
+}
+
+volatile void *CoverageRecord::getShm() {
+    if(!IsOpen()) {
+        fprintf(stderr, "Warning! SHM is NULL!\n");
+    }
+    return shm_;
+}
+
+Result<void> CoverageRecord::Rpc(struct line_coverage_client_req* req, \
+                                  int req_fd, \
+                                  struct line_coverage_client_resp* resp) {
+    int rc;
+
+    if (req_fd < 0) {
+        rc = write(coverage_srv_fd_, req, sizeof(*req));
+    } else {
+        iovec iov = {
+                .iov_base = req,
+                .iov_len = sizeof(*req),
+        };
+
+        trusty_shm shm = {
+                .fd = req_fd,
+                .transfer = TRUSTY_SHARE,
+        };
+
+        rc = tipc_send(coverage_srv_fd_, &iov, 1, &shm, 1);
+    }
+
+    if (rc != (int)sizeof(*req)) {
+        return ErrnoError() << "failed to send request to coverage server: ";
+    }
+
+    rc = read(coverage_srv_fd_, resp, sizeof(*resp));
+    if (rc != (int)sizeof(*resp)) {
+        return ErrnoError() << "failed to read reply from coverage server: ";
+    }
+
+    if (resp->hdr.cmd != (req->hdr.cmd | LINE_COVERAGE_CLIENT_CMD_RESP_BIT)) {
+        return ErrnoError() << "unknown response cmd: " << resp->hdr.cmd;
+    }
+
+    return {};
+}
+
+Result<void> CoverageRecord::Open(int fd) {
+    struct line_coverage_client_req req;
+    struct line_coverage_client_resp resp;
+
+    if (shm_) {
+        return {}; /* already initialized */
+    }
+
+    coverage_srv_fd_= fd;
+
+    req.hdr.cmd = LINE_COVERAGE_CLIENT_CMD_OPEN;
+    req.open_args.uuid = uuid_;
+    auto ret = Rpc(&req, -1, &resp);
+    if (!ret.ok()) {
+        return Error() << "failed to open coverage client: " << ret.error();
+    }
+    record_len_ = resp.open_args.record_len;
+    shm_len_ = RoundPageUp(record_len_);
+
+    BufferAllocator allocator;
+
+    fd = allocator.Alloc("system", shm_len_);
+    if (fd < 0) {
+        return ErrnoError() << "failed to create dmabuf of size " << shm_len_
+                            << " err code: " << fd;
+    }
+    unique_fd dma_buf(fd);
+
+    void* shm = mmap(0, shm_len_, PROT_READ | PROT_WRITE, MAP_SHARED, dma_buf, 0);
+    if (shm == MAP_FAILED) {
+        return ErrnoError() << "failed to map memfd: ";
+    }
+
+    req.hdr.cmd = LINE_COVERAGE_CLIENT_CMD_SHARE_RECORD;
+    req.share_record_args.shm_len = shm_len_;
+    ret = Rpc(&req, dma_buf, &resp);
+    if (!ret.ok()) {
+        return Error() << "failed to send shared memory: " << ret.error();
+    }
+
+    shm_ = shm;
+
+    req.hdr.cmd = LINE_COVERAGE_CLIENT_CMD_OPEN;
+    req.open_args.uuid = uuid_;
+    ret = Rpc(&req, -1, &resp);
+    if (!ret.ok()) {
+        return Error() << "failed to open coverage client: " << ret.error();
+    }
+
+    return {};
+}
+
+bool CoverageRecord::IsOpen() {
+    return shm_;
+}
+
+Result<void> CoverageRecord::SaveFile(const std::string& filename) {
+    if(!IsOpen()) {
+        return ErrnoError() << "Warning! SHM is NULL!";
+    }
+    android::base::unique_fd output_fd(TEMP_FAILURE_RETRY(creat(filename.c_str(), 00644)));
+    if (!output_fd.ok()) {
+        return ErrnoError() << "Could not open output file";
+    }
+
+    uintptr_t* begin = (uintptr_t*)((char *)shm_ + sizeof(struct control));
+    bool ret = WriteFully(output_fd, begin, record_len_);
+    if(!ret) {
+        fprintf(stderr, "Coverage write to file failed\n");
+    }
+
+    return {};
+}
+
+}  // namespace line_coverage
+}  // namespace trusty
+}  // namespace android
diff --git a/trusty/line-coverage/include/trusty/line-coverage/coverage.h b/trusty/line-coverage/include/trusty/line-coverage/coverage.h
new file mode 100644
index 0000000..53901be
--- /dev/null
+++ b/trusty/line-coverage/include/trusty/line-coverage/coverage.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <optional>
+#include <string>
+
+#include <android-base/result.h>
+#include <android-base/unique_fd.h>
+#include <stdint.h>
+#include <trusty/line-coverage/tipc.h>
+
+namespace android {
+namespace trusty {
+namespace line_coverage {
+
+using android::base::Result;
+using android::base::unique_fd;
+
+class CoverageRecord {
+  public:
+    CoverageRecord(std::string tipc_dev, struct uuid* uuid);
+
+    ~CoverageRecord();
+    Result<void> Open(int fd);
+    bool IsOpen();
+    Result<void> SaveFile(const std::string& filename);
+    volatile void* getShm();
+
+  private:
+    Result<void> Rpc(struct line_coverage_client_req* req, \
+                      int req_fd, \
+                      struct line_coverage_client_resp* resp);
+
+    Result<std::pair<size_t, size_t>> GetRegionBounds(uint32_t region_type);
+
+    std::string tipc_dev_;
+    int coverage_srv_fd_;
+    struct uuid uuid_;
+    size_t record_len_;
+    volatile void* shm_;
+    size_t shm_len_;
+};
+
+}  // namespace line_coverage
+}  // namespace trusty
+}  // namespace android
diff --git a/trusty/line-coverage/include/trusty/line-coverage/tipc.h b/trusty/line-coverage/include/trusty/line-coverage/tipc.h
new file mode 100644
index 0000000..20e855c
--- /dev/null
+++ b/trusty/line-coverage/include/trusty/line-coverage/tipc.h
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* This file needs to be kept in-sync with its counterpart on Trusty side */
+
+#pragma once
+
+#include <stdint.h>
+#include <trusty/line-coverage/uuid.h>
+
+
+#define LINE_COVERAGE_CLIENT_PORT "com.android.trusty.linecoverage.client"
+
+/**
+ * enum line_coverage_client_cmd - command identifiers for coverage client interface
+ * @LINE_COVERAGE_CLIENT_CMD_RESP_BIT:     response bit set as part of response
+ * @LINE_COVERAGE_CLIENT_CMD_SHIFT:        number of bits used by response bit
+ * @LINE_COVERAGE_CLIENT_CMD_OPEN:         command to open coverage record
+ * @LINE_COVERAGE_CLIENT_CMD_SHARE_RECORD: command to register a shared memory region
+ *                                    where coverage record will be written to
+ */
+enum line_coverage_client_cmd {
+    LINE_COVERAGE_CLIENT_CMD_RESP_BIT = 1U,
+    LINE_COVERAGE_CLIENT_CMD_SHIFT = 1U,
+    LINE_COVERAGE_CLIENT_CMD_OPEN = (1U << LINE_COVERAGE_CLIENT_CMD_SHIFT),
+    LINE_COVERAGE_CLIENT_CMD_SHARE_RECORD = (2U << LINE_COVERAGE_CLIENT_CMD_SHIFT),
+    LINE_COVERAGE_CLIENT_CMD_SEND_LIST = (3U << LINE_COVERAGE_CLIENT_CMD_SHIFT),
+};
+
+/**
+ * struct line_coverage_client_hdr - header for coverage client messages
+ * @cmd: command identifier
+ *
+ * Note that no messages return a status code. Any error on the server side
+ * results in the connection being closed. So, operations can be assumed to be
+ * successful if they return a response.
+ */
+struct line_coverage_client_hdr {
+    uint32_t cmd;
+};
+
+/**
+ * struct line_coverage_client_open_req - arguments for request to open coverage
+ *                                   record
+ * @uuid: UUID of target TA
+ *
+ * There is one coverage record per TA. @uuid is used to identify both the TA
+ * and corresponding coverage record.
+ */
+struct line_coverage_client_open_req {
+    struct uuid uuid;
+};
+
+/**
+ * struct line_coverage_client_open_resp - arguments for response to open coverage
+ *                                    record
+ * @record_len: length of coverage record that will be emitted by target TA
+ *
+ * Shared memory allocated for this coverage record must larger than
+ * @record_len.
+ */
+struct line_coverage_client_open_resp {
+    uint32_t record_len;
+};
+
+/**
+ * struct line_coverage_client_send_list_resp - arguments for response to send list
+ *                                   record
+ * @uuid: UUID of TA that connected to aggregator
+ */
+struct line_coverage_client_send_list_resp {
+    struct uuid uuid;
+};
+
+/**
+ * struct line_coverage_client_send_list_resp - arguments for response to send list
+ *                                   record
+ * @index: index of the list being requested
+ */
+struct line_coverage_client_send_list_req {
+    uint32_t index;
+};
+
+/**
+ * struct line_coverage_client_share_record_req - arguments for request to share
+ *                                           memory for coverage record
+ * @shm_len: length of memory region being shared
+ *
+ * A handle to a memory region must be sent along with this message. This memory
+ * is used to store coverage record.
+ *
+ * Upon success, this memory region can be assumed to be shared between the
+ * client and target TA.
+ */
+struct line_coverage_client_share_record_req {
+    uint32_t shm_len;
+};
+
+/**
+ * struct line_coverage_client_req - structure for a coverage client request
+ * @hdr:               message header
+ * @open_args:         arguments for %COVERAGE_CLIENT_CMD_OPEN request
+ * @share_record_args: arguments for %COVERAGE_CLIENT_CMD_SHARE_RECORD request
+ * @index: arguments for %COVERAGE_CLIENT_CMD_SHARE_RECORD request
+ */
+struct line_coverage_client_req {
+    struct line_coverage_client_hdr hdr;
+    union {
+        struct line_coverage_client_open_req open_args;
+        struct line_coverage_client_share_record_req share_record_args;
+        struct line_coverage_client_send_list_req send_list_args;
+    };
+};
+
+/**
+ * struct line_coverage_client_resp - structure for a coverage client response
+ * @hdr:       message header
+ * @open_args: arguments for %COVERAGE_CLIENT_CMD_OPEN response
+ * @send_list_args: arguments for %COVERAGE_CLIENT_CMD_SHARE_RECORD response
+ */
+struct line_coverage_client_resp {
+    struct line_coverage_client_hdr hdr;
+    union {
+        struct line_coverage_client_open_resp open_args;
+        struct line_coverage_client_send_list_resp send_list_args;
+    };
+};
diff --git a/trusty/line-coverage/include/trusty/line-coverage/uuid.h b/trusty/line-coverage/include/trusty/line-coverage/uuid.h
new file mode 100644
index 0000000..1873980
--- /dev/null
+++ b/trusty/line-coverage/include/trusty/line-coverage/uuid.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <string.h>
+
+#define UUCMP(u1, u2) if (u1 != u2) return u1 < u2
+
+struct uuid {
+    uint32_t time_low;
+    uint16_t time_mid;
+    uint16_t time_hi_and_version;
+    uint8_t clock_seq_and_node[8];
+
+    bool operator<(const struct uuid& rhs) const
+    {
+        UUCMP(time_low, rhs.time_low);
+        UUCMP(time_mid, rhs.time_mid);
+        UUCMP(time_hi_and_version, rhs.time_hi_and_version);
+        return memcmp(clock_seq_and_node, rhs.clock_seq_and_node, 8);
+    }
+};
diff --git a/trusty/storage/proxy/Android.bp b/trusty/storage/proxy/Android.bp
index 2e97ee0..e362b8b 100644
--- a/trusty/storage/proxy/Android.bp
+++ b/trusty/storage/proxy/Android.bp
@@ -33,6 +33,7 @@
 
     shared_libs: [
         "libbase",
+        "libbinder_ndk",
         "libcutils",
         "liblog",
         "libhardware_legacy",
diff --git a/trusty/storage/proxy/proxy.c b/trusty/storage/proxy/proxy.c
index c89c5b6..67e935e 100644
--- a/trusty/storage/proxy/proxy.c
+++ b/trusty/storage/proxy/proxy.c
@@ -24,6 +24,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include <android/binder_process.h>
 #include <cutils/android_filesystem_config.h>
 
 #include "checkpoint_handling.h"
@@ -238,6 +239,18 @@
     /* parse arguments */
     parse_args(argc, argv);
 
+    /*
+     * Start binder threadpool. At least one extra binder thread is needed to
+     * connect to the wakelock service without relying on polling. If we poll on
+     * the main thread we end up pausing for at least 1s even if the service
+     * starts faster. We set the max thread count to 0 because startThreadPool
+     * "Starts one thread, PLUS those requested in setThreadPoolMaxThreadCount,
+     * PLUS those manually requested in joinThreadPool." We only need a single
+     * binder thread to receive notifications on.
+     */
+    ABinderProcess_setThreadPoolMaxThreadCount(0);
+    ABinderProcess_startThreadPool();
+
     /* initialize secure storage directory */
     rc = storage_init(ss_data_root);
     if (rc < 0) return EXIT_FAILURE;
diff --git a/trusty/storage/proxy/rpmb.c b/trusty/storage/proxy/rpmb.c
index 22a85a7..1f5d107 100644
--- a/trusty/storage/proxy/rpmb.c
+++ b/trusty/storage/proxy/rpmb.c
@@ -399,6 +399,14 @@
 
     bool is_request_write = req->reliable_write_size > 0;
 
+    /*
+     * Internally this call connects to the suspend service, which will cause
+     * this service to start if not already running. If the binder thread pool
+     * has not been started at this point, this call will block and poll for the
+     * service every 1s. We need to make sure the thread pool is started to
+     * receive an async notification that the service is started to avoid
+     * blocking (see main).
+     */
     wl_rc = acquire_wake_lock(PARTIAL_WAKE_LOCK, UFS_WAKE_LOCK_NAME);
     if (wl_rc < 0) {
         ALOGE("%s: failed to acquire wakelock: %d, %s\n", __func__, wl_rc, strerror(errno));
diff --git a/trusty/utils/coverage-controller/Android.bp b/trusty/utils/coverage-controller/Android.bp
new file mode 100644
index 0000000..1aa88cc
--- /dev/null
+++ b/trusty/utils/coverage-controller/Android.bp
@@ -0,0 +1,34 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_binary {
+    name: "coverage-controller",
+    vendor: true,
+
+    srcs: ["controller.cpp"],
+    shared_libs: [
+        "libc",
+        "liblog",
+        "libbase",
+        "libdmabufheap",
+    ],
+    static_libs: [
+        "libtrusty",
+        "libtrusty_line_coverage",
+    ],
+}
diff --git a/trusty/utils/coverage-controller/controller.cpp b/trusty/utils/coverage-controller/controller.cpp
new file mode 100644
index 0000000..730c010
--- /dev/null
+++ b/trusty/utils/coverage-controller/controller.cpp
@@ -0,0 +1,164 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <getopt.h>
+#include <trusty/line-coverage/coverage.h>
+#include <trusty/tipc.h>
+#include <array>
+#include <memory>
+#include <vector>
+
+#include "controller.h"
+
+#define READ_ONCE(x) (*((volatile __typeof__(x) *) &(x)))
+#define WRITE_ONCE(x, val) (*((volatile __typeof__(val) *) &(x)) = (val))
+
+namespace android {
+namespace trusty {
+namespace controller {
+
+using ::android::trusty::line_coverage::CoverageRecord;
+
+void Controller::run(std::string output_dir) {
+    connectCoverageServer();
+    struct control *control;
+    uint64_t complete_cnt = 0, start_cnt = 0, flags;
+
+    while(1) {
+        setUpShm();
+
+        for (int index = 0; index < record_list_.size(); index++) {
+            control = (struct control *)record_list_[index]->getShm();
+            start_cnt = READ_ONCE((control->write_buffer_start_count));
+            complete_cnt = READ_ONCE(control->write_buffer_complete_count);
+            flags = READ_ONCE(control->cntrl_flags);
+
+            if (complete_cnt != counters[index] && start_cnt == complete_cnt) {
+                WRITE_ONCE(control->cntrl_flags, FLAG_NONE);
+                std::string fmt = "/%d.%lu.profraw";
+                int sz = std::snprintf(nullptr, 0, fmt.c_str(), index, counters[index]);
+                std::string filename(sz+1, '.');
+                std::sprintf(filename.data(), fmt.c_str(), index, counters[index]);
+                filename.insert(0, output_dir);
+                android::base::Result<void> res = record_list_[index]->SaveFile(filename);
+                counters[index]++;
+            }
+            if(complete_cnt == counters[index] &&
+                !(flags & FLAG_RUN)) {
+                flags |= FLAG_RUN;
+                WRITE_ONCE(control->cntrl_flags, flags);
+            }
+        }
+    }
+}
+
+void Controller::connectCoverageServer() {
+    coverage_srv_fd = tipc_connect(TIPC_DEV, LINE_COVERAGE_CLIENT_PORT);
+    if (coverage_srv_fd < 0) {
+        fprintf(stderr, \
+                "Error: Failed to connect to Trusty coverage server: %d\n", coverage_srv_fd);
+        return;
+    }
+}
+
+void Controller::setUpShm() {
+    struct line_coverage_client_req req;
+    struct line_coverage_client_resp resp;
+    uint32_t cur_index = record_list_.size();
+    struct uuid zero_uuid = {0, 0, 0, { 0 }};
+    req.hdr.cmd = LINE_COVERAGE_CLIENT_CMD_SEND_LIST;
+    int rc = write(coverage_srv_fd, &req, sizeof(req));
+        if (rc != (int)sizeof(req)) {
+            fprintf(stderr, "failed to send request to coverage server: %d\n", rc);
+            return;
+    }
+
+    while(1) {
+        rc = read(coverage_srv_fd, &resp, sizeof(resp));
+        if (rc != (int)sizeof(resp)) {
+            fprintf(stderr, "failed to read reply from coverage server:: %d\n", rc);
+        }
+
+        if (resp.hdr.cmd == (req.hdr.cmd | LINE_COVERAGE_CLIENT_CMD_RESP_BIT)) {
+            if (!memcmp(&resp.send_list_args.uuid, &zero_uuid, sizeof(struct uuid))) {
+                break;
+            }
+            if(uuid_set_.find(resp.send_list_args.uuid) == uuid_set_.end()) {
+                uuid_set_.insert(resp.send_list_args.uuid);
+                record_list_.push_back(std::make_unique<CoverageRecord>(TIPC_DEV,
+                                                                    &resp.send_list_args.uuid));
+                counters.push_back(0);
+            }
+        }
+        else {
+            fprintf(stderr, "Unknown response header\n");
+        }
+        cur_index++;
+        req.hdr.cmd = LINE_COVERAGE_CLIENT_CMD_SEND_LIST;
+        req.send_list_args.index = cur_index;
+        int rc = write(coverage_srv_fd, &req, sizeof(req));
+        if (rc != (int)sizeof(req)) {
+            fprintf(stderr, "failed to send request to coverage server: %d\n", rc);
+        }
+    }
+
+    for(int ind = 0 ; ind < record_list_.size() ; ind++) {
+        record_list_[ind]->Open(coverage_srv_fd);
+    }
+}
+
+
+}  // namespace controller
+}  // namespace trusty
+}  // namespace android
+
+int main(int argc, char* argv[]) {
+
+    std::string optarg = "";
+    do {
+        int c;
+        c = getopt(argc, argv, "o");
+
+        if (c == -1) {
+            break;
+        }
+
+        switch (c) {
+        case 'o':
+            break;
+        default:
+            fprintf(stderr, "usage: %s -o [output_directory]\n", argv[0]);
+            exit(EXIT_FAILURE);
+        }
+    } while (1);
+
+    if (argc > optind + 1) {
+        fprintf(stderr, "%s: too many arguments\n", argv[0]);
+        exit(EXIT_FAILURE);
+    }
+
+    if (argc > optind) {
+        optarg = argv[optind];
+    }
+    if (optarg.size()==0) {
+        optarg = "data/local/tmp";
+    }
+
+    android::trusty::controller::Controller cur;
+    cur.run(optarg);
+
+    return EXIT_SUCCESS;
+}
\ No newline at end of file
diff --git a/trusty/utils/coverage-controller/controller.h b/trusty/utils/coverage-controller/controller.h
new file mode 100644
index 0000000..b771c16
--- /dev/null
+++ b/trusty/utils/coverage-controller/controller.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <trusty/line-coverage/coverage.h>
+#include <array>
+#include <memory>
+#include <vector>
+#include <set>
+
+#define TIPC_DEV "/dev/trusty-ipc-dev0"
+#define TEST_SRV_PORT "com.android.trusty.sancov.test.srv"
+#define TEST_SRV_MODULE "srv.syms.elf"
+
+#define FLAG_NONE               0x0
+#define FLAG_RUN                0x1
+#define FLAG_TOGGLE_CLEAR       0x2
+
+struct control {
+    /* Written by controller, read by instrumented TA */
+    uint64_t        cntrl_flags;
+
+    /* Written by instrumented TA, read by controller */
+    uint64_t        oper_flags;
+    uint64_t        write_buffer_start_count;
+    uint64_t        write_buffer_complete_count;
+};
+
+namespace android {
+namespace trusty {
+namespace controller {
+
+class Controller {
+  public:
+    public:
+        void run(std::string output_dir);
+
+    private:
+        std::vector<std::unique_ptr<line_coverage::CoverageRecord>>record_list_;
+        std::set<struct uuid>uuid_set_;
+        std::vector<uint64_t> counters;
+        int coverage_srv_fd;
+
+        void connectCoverageServer();
+        void setUpShm();
+};
+
+}  // namespace controller
+}  // namespace trusty
+}  // namespace android