diff --git a/NOTICE b/NOTICE
deleted file mode 100644
index 8e8a91c..0000000
--- a/NOTICE
+++ /dev/null
@@ -1,16 +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.
-
--------------------------------------------------------------------
-
diff --git a/debuggerd/crash_dump.cpp b/debuggerd/crash_dump.cpp
index c8612bf..04e1e4e 100644
--- a/debuggerd/crash_dump.cpp
+++ b/debuggerd/crash_dump.cpp
@@ -153,14 +153,14 @@
   }
 
   struct timeval tv = {
-      .tv_sec = 1 * android::base::TimeoutMultiplier(),
+      .tv_sec = 1 * android::base::HwTimeoutMultiplier(),
       .tv_usec = 0,
   };
   if (setsockopt(amfd.get(), SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv)) == -1) {
     PLOG(ERROR) << "failed to set send timeout on activity manager socket";
     return false;
   }
-  tv.tv_sec = 3 * android::base::TimeoutMultiplier();  // 3 seconds on handshake read
+  tv.tv_sec = 3 * android::base::HwTimeoutMultiplier();  // 3 seconds on handshake read
   if (setsockopt(amfd.get(), SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) == -1) {
     PLOG(ERROR) << "failed to set receive timeout on activity manager socket";
     return false;
@@ -391,7 +391,7 @@
 
   // There appears to be a bug in the kernel where our death causes SIGHUP to
   // be sent to our process group if we exit while it has stopped jobs (e.g.
-  // because of wait_for_gdb). Use setsid to create a new process group to
+  // because of wait_for_debugger). Use setsid to create a new process group to
   // avoid hitting this.
   setsid();
 
@@ -448,7 +448,7 @@
   //
   // Note: processes with many threads and minidebug-info can take a bit to
   //       unwind, do not make this too small. b/62828735
-  alarm(30 * android::base::TimeoutMultiplier());
+  alarm(30 * android::base::HwTimeoutMultiplier());
 
   // Get the process name (aka cmdline).
   std::string process_name = get_process_name(g_target_thread);
@@ -548,15 +548,17 @@
   fork_exit_write.reset();
 
   // Defer the message until later, for readability.
-  bool wait_for_gdb = android::base::GetBoolProperty("debug.debuggerd.wait_for_gdb", false);
+  bool wait_for_debugger = android::base::GetBoolProperty(
+      "debug.debuggerd.wait_for_debugger",
+      android::base::GetBoolProperty("debug.debuggerd.wait_for_gdb", false));
   if (siginfo.si_signo == BIONIC_SIGNAL_DEBUGGER) {
-    wait_for_gdb = false;
+    wait_for_debugger = false;
   }
 
   // Detach from all of our attached threads before resuming.
   for (const auto& [tid, thread] : thread_info) {
     int resume_signal = thread.signo == BIONIC_SIGNAL_DEBUGGER ? 0 : thread.signo;
-    if (wait_for_gdb) {
+    if (wait_for_debugger) {
       resume_signal = 0;
       if (tgkill(target_process, tid, SIGSTOP) != 0) {
         PLOG(WARNING) << "failed to send SIGSTOP to " << tid;
@@ -641,12 +643,12 @@
     }
   }
 
-  if (wait_for_gdb) {
+  if (wait_for_debugger) {
     // Use ALOGI to line up with output from engrave_tombstone.
     ALOGI(
         "***********************************************************\n"
         "* Process %d has been suspended while crashing.\n"
-        "* To attach gdbserver and start gdb, run this on the host:\n"
+        "* To attach the debugger, run this on the host:\n"
         "*\n"
         "*     gdbclient.py -p %d\n"
         "*\n"
diff --git a/debuggerd/crasher/Android.bp b/debuggerd/crasher/Android.bp
index 7975a3a..23b106e 100644
--- a/debuggerd/crasher/Android.bp
+++ b/debuggerd/crasher/Android.bp
@@ -13,7 +13,6 @@
         "-Werror",
         "-O0",
         "-fstack-protector-all",
-        "-Wno-free-nonheap-object",
         "-Wno-date-time",
     ],
     srcs: ["crasher.cpp"],
diff --git a/debuggerd/crasher/crasher.cpp b/debuggerd/crasher/crasher.cpp
index a2b13a3..db30b8f 100644
--- a/debuggerd/crasher/crasher.cpp
+++ b/debuggerd/crasher/crasher.cpp
@@ -134,10 +134,14 @@
     return a*2;
 }
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wfree-nonheap-object"
+
 noinline void abuse_heap() {
     char buf[16];
     free(buf); // GCC is smart enough to warn about this, but we're doing it deliberately.
 }
+#pragma clang diagnostic pop
 
 noinline void leak() {
     while (true) {
diff --git a/debuggerd/debuggerd_test.cpp b/debuggerd/debuggerd_test.cpp
index ab95768..de37a5b 100644
--- a/debuggerd/debuggerd_test.cpp
+++ b/debuggerd/debuggerd_test.cpp
@@ -69,7 +69,7 @@
 #define ARCH_SUFFIX ""
 #endif
 
-constexpr char kWaitForGdbKey[] = "debug.debuggerd.wait_for_gdb";
+constexpr char kWaitForDebuggerKey[] = "debug.debuggerd.wait_for_debugger";
 
 #define TIMEOUT(seconds, expr)                                     \
   [&]() {                                                          \
@@ -157,7 +157,7 @@
 class CrasherTest : public ::testing::Test {
  public:
   pid_t crasher_pid = -1;
-  bool previous_wait_for_gdb;
+  bool previous_wait_for_debugger;
   unique_fd crasher_pipe;
   unique_fd intercept_fd;
 
@@ -178,8 +178,13 @@
 };
 
 CrasherTest::CrasherTest() {
-  previous_wait_for_gdb = android::base::GetBoolProperty(kWaitForGdbKey, false);
-  android::base::SetProperty(kWaitForGdbKey, "0");
+  previous_wait_for_debugger = android::base::GetBoolProperty(kWaitForDebuggerKey, false);
+  android::base::SetProperty(kWaitForDebuggerKey, "0");
+
+  // Clear the old property too, just in case someone's been using it
+  // on this device. (We only document the new name, but we still support
+  // the old name so we don't break anyone's existing setups.)
+  android::base::SetProperty("debug.debuggerd.wait_for_gdb", "0");
 }
 
 CrasherTest::~CrasherTest() {
@@ -189,7 +194,7 @@
     TEMP_FAILURE_RETRY(waitpid(crasher_pid, &status, WUNTRACED));
   }
 
-  android::base::SetProperty(kWaitForGdbKey, previous_wait_for_gdb ? "1" : "0");
+  android::base::SetProperty(kWaitForDebuggerKey, previous_wait_for_debugger ? "1" : "0");
 }
 
 void CrasherTest::StartIntercept(unique_fd* output_fd, DebuggerdDumpType intercept_type) {
@@ -734,9 +739,9 @@
   AssertDeath(SIGABRT);
 }
 
-TEST_F(CrasherTest, wait_for_gdb) {
-  if (!android::base::SetProperty(kWaitForGdbKey, "1")) {
-    FAIL() << "failed to enable wait_for_gdb";
+TEST_F(CrasherTest, wait_for_debugger) {
+  if (!android::base::SetProperty(kWaitForDebuggerKey, "1")) {
+    FAIL() << "failed to enable wait_for_debugger";
   }
   sleep(1);
 
diff --git a/debuggerd/handler/debuggerd_handler.cpp b/debuggerd/handler/debuggerd_handler.cpp
index ca809e4..b607397 100644
--- a/debuggerd/handler/debuggerd_handler.cpp
+++ b/debuggerd/handler/debuggerd_handler.cpp
@@ -274,7 +274,7 @@
 
     // There appears to be a bug in the kernel where our death causes SIGHUP to
     // be sent to our process group if we exit while it has stopped jobs (e.g.
-    // because of wait_for_gdb). Use setsid to create a new process group to
+    // because of wait_for_debugger). Use setsid to create a new process group to
     // avoid hitting this.
     setsid();
 
@@ -600,7 +600,7 @@
     // starting to dump right before our death.
     pthread_mutex_unlock(&crash_mutex);
   } else {
-    // Resend the signal, so that either gdb or the parent's waitpid sees it.
+    // Resend the signal, so that either the debugger or the parent's waitpid sees it.
     resend_signal(info);
   }
 }
diff --git a/debuggerd/libdebuggerd/test/sys/system_properties.h b/debuggerd/libdebuggerd/test/sys/system_properties.h
deleted file mode 100644
index 1f4f58a..0000000
--- a/debuggerd/libdebuggerd/test/sys/system_properties.h
+++ /dev/null
@@ -1,37 +0,0 @@
-/*
- * Copyright (C) 2015 The Android Open Source Project
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *  * Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- *  * Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in
- *    the documentation and/or other materials provided with the
- *    distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#ifndef _DEBUGGERD_TEST_SYS_SYSTEM_PROPERTIES_H
-#define _DEBUGGERD_TEST_SYS_SYSTEM_PROPERTIES_H
-
-// This is just enough to get the property code to compile on
-// the host.
-
-#define PROP_VALUE_MAX  92
-
-#endif // _DEBUGGERD_TEST_SYS_SYSTEM_PROPERTIES_H
diff --git a/debuggerd/tombstoned/intercept_manager.cpp b/debuggerd/tombstoned/intercept_manager.cpp
index 4d4646a..613e6f5 100644
--- a/debuggerd/tombstoned/intercept_manager.cpp
+++ b/debuggerd/tombstoned/intercept_manager.cpp
@@ -163,7 +163,7 @@
     event_assign(intercept->intercept_event, intercept_manager->base, sockfd, EV_READ | EV_TIMEOUT,
                  intercept_close_cb, arg);
 
-    struct timeval timeout = {.tv_sec = 10 * android::base::TimeoutMultiplier(), .tv_usec = 0};
+    struct timeval timeout = {.tv_sec = 10 * android::base::HwTimeoutMultiplier(), .tv_usec = 0};
     event_add(intercept->intercept_event, &timeout);
   }
 
@@ -179,7 +179,7 @@
   intercept->intercept_manager = static_cast<InterceptManager*>(arg);
   intercept->sockfd.reset(sockfd);
 
-  struct timeval timeout = {1 * android::base::TimeoutMultiplier(), 0};
+  struct timeval timeout = {1 * android::base::HwTimeoutMultiplier(), 0};
   event_base* base = evconnlistener_get_base(listener);
   event* intercept_event =
     event_new(base, sockfd, EV_TIMEOUT | EV_READ, intercept_request_cb, intercept);
diff --git a/debuggerd/tombstoned/tombstoned.cpp b/debuggerd/tombstoned/tombstoned.cpp
index bc2d33d..0b87b7a 100644
--- a/debuggerd/tombstoned/tombstoned.cpp
+++ b/debuggerd/tombstoned/tombstoned.cpp
@@ -320,7 +320,7 @@
   }
 
   // TODO: Make this configurable by the interceptor?
-  struct timeval timeout = {10 * android::base::TimeoutMultiplier(), 0};
+  struct timeval timeout = {10 * android::base::HwTimeoutMultiplier(), 0};
 
   event_base* base = event_get_base(crash->crash_event);
 
@@ -340,7 +340,7 @@
 
   // TODO: Make sure that only java crashes come in on the java socket
   // and only native crashes on the native socket.
-  struct timeval timeout = {1 * android::base::TimeoutMultiplier(), 0};
+  struct timeval timeout = {1 * android::base::HwTimeoutMultiplier(), 0};
   event* crash_event = event_new(base, sockfd, EV_TIMEOUT | EV_READ, crash_request_cb, crash);
   crash->crash_socket_fd.reset(sockfd);
   crash->crash_event = crash_event;
diff --git a/fastboot/Android.bp b/fastboot/Android.bp
index a1f1c17..3c4269b 100644
--- a/fastboot/Android.bp
+++ b/fastboot/Android.bp
@@ -55,6 +55,7 @@
         "tcp.cpp",
         "udp.cpp",
         "util.cpp",
+        "vendor_boot_img_utils.cpp",
         "fastboot_driver.cpp",
     ],
 
@@ -75,7 +76,9 @@
     ],
 
     header_libs: [
+        "avb_headers",
         "bootimg_headers",
+        "libstorage_literals_headers",
     ],
 
     export_header_lib_headers: [
@@ -138,6 +141,12 @@
 
     recovery: true,
 
+    product_variables: {
+        debuggable: {
+            cppflags: ["-DFB_ENABLE_FETCH"],
+        },
+    },
+
     srcs: [
         "device/commands.cpp",
         "device/fastboot_device.cpp",
@@ -183,7 +192,8 @@
     header_libs: [
         "avb_headers",
         "libsnapshot_headers",
-    ]
+        "libstorage_literals_headers",
+    ],
 }
 
 cc_defaults {
@@ -262,12 +272,17 @@
         "tcp.cpp",
         "udp.cpp",
         "util.cpp",
+        "vendor_boot_img_utils.cpp",
         "fastboot_driver.cpp",
     ],
 
     // Only version the final binaries
     use_version_lib: false,
     static_libs: ["libbuildversion"],
+    header_libs: [
+        "avb_headers",
+        "libstorage_literals_headers",
+    ],
 
     generated_headers: ["platform_tools_version"],
 
@@ -359,3 +374,33 @@
         },
     },
 }
+
+cc_test_host {
+    name: "fastboot_vendor_boot_img_utils_test",
+    srcs: ["vendor_boot_img_utils_test.cpp"],
+    static_libs: [
+        "libbase",
+        "libc++fs",
+        "libfastboot",
+        "libgmock",
+        "liblog",
+    ],
+    header_libs: [
+        "avb_headers",
+        "bootimg_headers",
+    ],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    data: [
+        ":fastboot_test_dtb",
+        ":fastboot_test_bootconfig",
+        ":fastboot_test_vendor_ramdisk_none",
+        ":fastboot_test_vendor_ramdisk_platform",
+        ":fastboot_test_vendor_ramdisk_replace",
+        ":fastboot_test_vendor_boot_v3",
+        ":fastboot_test_vendor_boot_v4_without_frag",
+        ":fastboot_test_vendor_boot_v4_with_frag"
+    ],
+}
diff --git a/fastboot/constants.h b/fastboot/constants.h
index ba43ca5..4ea68da 100644
--- a/fastboot/constants.h
+++ b/fastboot/constants.h
@@ -35,6 +35,7 @@
 #define FB_CMD_OEM "oem"
 #define FB_CMD_GSI "gsi"
 #define FB_CMD_SNAPSHOT_UPDATE "snapshot-update"
+#define FB_CMD_FETCH "fetch"
 
 #define RESPONSE_OKAY "OKAY"
 #define RESPONSE_FAIL "FAIL"
@@ -77,3 +78,4 @@
 #define FB_VAR_FIRST_API_LEVEL "first-api-level"
 #define FB_VAR_SECURITY_PATCH_LEVEL "security-patch-level"
 #define FB_VAR_TREBLE_ENABLED "treble-enabled"
+#define FB_VAR_MAX_FETCH_SIZE "max-fetch-size"
diff --git a/fastboot/device/commands.cpp b/fastboot/device/commands.cpp
index b2b6a9e..b72f3fe 100644
--- a/fastboot/device/commands.cpp
+++ b/fastboot/device/commands.cpp
@@ -16,6 +16,7 @@
 
 #include "commands.h"
 
+#include <inttypes.h>
 #include <sys/socket.h>
 #include <sys/un.h>
 
@@ -36,6 +37,7 @@
 #include <liblp/builder.h>
 #include <liblp/liblp.h>
 #include <libsnapshot/snapshot.h>
+#include <storage_literals/storage_literals.h>
 #include <uuid/uuid.h>
 
 #include "constants.h"
@@ -43,6 +45,12 @@
 #include "flashing.h"
 #include "utility.h"
 
+#ifdef FB_ENABLE_FETCH
+static constexpr bool kEnableFetch = true;
+#else
+static constexpr bool kEnableFetch = false;
+#endif
+
 using android::fs_mgr::MetadataBuilder;
 using ::android::hardware::hidl_string;
 using ::android::hardware::boot::V1_0::BoolResult;
@@ -54,6 +62,8 @@
 using android::snapshot::SnapshotManager;
 using IBootControl1_1 = ::android::hardware::boot::V1_1::IBootControl;
 
+using namespace android::storage_literals;
+
 struct VariableHandlers {
     // Callback to retrieve the value of a single variable.
     std::function<bool(FastbootDevice*, const std::vector<std::string>&, std::string*)> get;
@@ -136,7 +146,9 @@
             {FB_VAR_DYNAMIC_PARTITION, {GetDynamicPartition, nullptr}},
             {FB_VAR_FIRST_API_LEVEL, {GetFirstApiLevel, nullptr}},
             {FB_VAR_SECURITY_PATCH_LEVEL, {GetSecurityPatchLevel, nullptr}},
-            {FB_VAR_TREBLE_ENABLED, {GetTrebleEnabled, nullptr}}};
+            {FB_VAR_TREBLE_ENABLED, {GetTrebleEnabled, nullptr}},
+            {FB_VAR_MAX_FETCH_SIZE, {GetMaxFetchSize, nullptr}},
+    };
 
     if (args.size() < 2) {
         return device->WriteFail("Missing argument");
@@ -671,3 +683,175 @@
     }
     return device->WriteStatus(FastbootResult::OKAY, "Success");
 }
+
+namespace {
+// Helper of FetchHandler.
+class PartitionFetcher {
+  public:
+    static bool Fetch(FastbootDevice* device, const std::vector<std::string>& args) {
+        if constexpr (!kEnableFetch) {
+            return device->WriteFail("Fetch is not allowed on user build");
+        }
+
+        if (GetDeviceLockStatus()) {
+            return device->WriteFail("Fetch is not allowed on locked devices");
+        }
+
+        PartitionFetcher fetcher(device, args);
+        if (fetcher.Open()) {
+            fetcher.Fetch();
+        }
+        CHECK(fetcher.ret_.has_value());
+        return *fetcher.ret_;
+    }
+
+  private:
+    PartitionFetcher(FastbootDevice* device, const std::vector<std::string>& args)
+        : device_(device), args_(&args) {}
+    // Return whether the partition is successfully opened.
+    // If successfully opened, ret_ is left untouched. Otherwise, ret_ is set to the value
+    // that FetchHandler should return.
+    bool Open() {
+        if (args_->size() < 2) {
+            ret_ = device_->WriteFail("Missing partition arg");
+            return false;
+        }
+
+        partition_name_ = args_->at(1);
+        if (std::find(kAllowedPartitions.begin(), kAllowedPartitions.end(), partition_name_) ==
+            kAllowedPartitions.end()) {
+            ret_ = device_->WriteFail("Fetch is only allowed on [" +
+                                      android::base::Join(kAllowedPartitions, ", ") + "]");
+            return false;
+        }
+
+        if (!OpenPartition(device_, partition_name_, &handle_, true /* read */)) {
+            ret_ = device_->WriteFail(
+                    android::base::StringPrintf("Cannot open %s", partition_name_.c_str()));
+            return false;
+        }
+
+        partition_size_ = get_block_device_size(handle_.fd());
+        if (partition_size_ == 0) {
+            ret_ = device_->WriteOkay(android::base::StringPrintf("Partition %s has size 0",
+                                                                  partition_name_.c_str()));
+            return false;
+        }
+
+        start_offset_ = 0;
+        if (args_->size() >= 3) {
+            if (!android::base::ParseUint(args_->at(2), &start_offset_)) {
+                ret_ = device_->WriteFail("Invalid offset, must be integer");
+                return false;
+            }
+            if (start_offset_ > std::numeric_limits<off64_t>::max()) {
+                ret_ = device_->WriteFail(
+                        android::base::StringPrintf("Offset overflows: %" PRIx64, start_offset_));
+                return false;
+            }
+        }
+        if (start_offset_ > partition_size_) {
+            ret_ = device_->WriteFail(android::base::StringPrintf(
+                    "Invalid offset 0x%" PRIx64 ", partition %s has size 0x%" PRIx64, start_offset_,
+                    partition_name_.c_str(), partition_size_));
+            return false;
+        }
+        uint64_t maximum_total_size_to_read = partition_size_ - start_offset_;
+        total_size_to_read_ = maximum_total_size_to_read;
+        if (args_->size() >= 4) {
+            if (!android::base::ParseUint(args_->at(3), &total_size_to_read_)) {
+                ret_ = device_->WriteStatus(FastbootResult::FAIL, "Invalid size, must be integer");
+                return false;
+            }
+        }
+        if (total_size_to_read_ == 0) {
+            ret_ = device_->WriteOkay("Read 0 bytes");
+            return false;
+        }
+        if (total_size_to_read_ > maximum_total_size_to_read) {
+            ret_ = device_->WriteFail(android::base::StringPrintf(
+                    "Invalid size to read 0x%" PRIx64 ", partition %s has size 0x%" PRIx64
+                    " and fetching from offset 0x%" PRIx64,
+                    total_size_to_read_, partition_name_.c_str(), partition_size_, start_offset_));
+            return false;
+        }
+
+        if (total_size_to_read_ > kMaxFetchSizeDefault) {
+            ret_ = device_->WriteFail(android::base::StringPrintf(
+                    "Cannot fetch 0x%" PRIx64
+                    " bytes because it exceeds maximum transport size 0x%x",
+                    partition_size_, kMaxDownloadSizeDefault));
+            return false;
+        }
+
+        return true;
+    }
+
+    // Assume Open() returns true.
+    // After execution, ret_ is set to the value that FetchHandler should return.
+    void Fetch() {
+        CHECK(start_offset_ <= std::numeric_limits<off64_t>::max());
+        if (lseek64(handle_.fd(), start_offset_, SEEK_SET) != static_cast<off64_t>(start_offset_)) {
+            ret_ = device_->WriteFail(android::base::StringPrintf(
+                    "On partition %s, unable to lseek(0x%" PRIx64 ": %s", partition_name_.c_str(),
+                    start_offset_, strerror(errno)));
+            return;
+        }
+
+        if (!device_->WriteStatus(FastbootResult::DATA,
+                                  android::base::StringPrintf(
+                                          "%08x", static_cast<uint32_t>(total_size_to_read_)))) {
+            ret_ = false;
+            return;
+        }
+        uint64_t end_offset = start_offset_ + total_size_to_read_;
+        std::vector<char> buf(1_MiB);
+        uint64_t current_offset = start_offset_;
+        while (current_offset < end_offset) {
+            // On any error, exit. We can't return a status message to the driver because
+            // we are in the middle of writing data, so just let the driver guess what's wrong
+            // by ending the data stream prematurely.
+            uint64_t remaining = end_offset - current_offset;
+            uint64_t chunk_size = std::min<uint64_t>(buf.size(), remaining);
+            if (!android::base::ReadFully(handle_.fd(), buf.data(), chunk_size)) {
+                PLOG(ERROR) << std::hex << "Unable to read 0x" << chunk_size << " bytes from "
+                            << partition_name_ << " @ offset 0x" << current_offset;
+                ret_ = false;
+                return;
+            }
+            if (!device_->HandleData(false /* is read */, buf.data(), chunk_size)) {
+                PLOG(ERROR) << std::hex << "Unable to send 0x" << chunk_size << " bytes of "
+                            << partition_name_ << " @ offset 0x" << current_offset;
+                ret_ = false;
+                return;
+            }
+            current_offset += chunk_size;
+        }
+
+        ret_ = device_->WriteOkay(android::base::StringPrintf(
+                "Fetched %s (offset=0x%" PRIx64 ", size=0x%" PRIx64, partition_name_.c_str(),
+                start_offset_, total_size_to_read_));
+    }
+
+    static constexpr std::array<const char*, 3> kAllowedPartitions{
+            "vendor_boot",
+            "vendor_boot_a",
+            "vendor_boot_b",
+    };
+
+    FastbootDevice* device_;
+    const std::vector<std::string>* args_ = nullptr;
+    std::string partition_name_;
+    PartitionHandle handle_;
+    uint64_t partition_size_ = 0;
+    uint64_t start_offset_ = 0;
+    uint64_t total_size_to_read_ = 0;
+
+    // What FetchHandler should return.
+    std::optional<bool> ret_ = std::nullopt;
+};
+}  // namespace
+
+bool FetchHandler(FastbootDevice* device, const std::vector<std::string>& args) {
+    return PartitionFetcher::Fetch(device, args);
+}
diff --git a/fastboot/device/commands.h b/fastboot/device/commands.h
index c1324bc..345ae1a 100644
--- a/fastboot/device/commands.h
+++ b/fastboot/device/commands.h
@@ -20,6 +20,7 @@
 #include <vector>
 
 constexpr unsigned int kMaxDownloadSizeDefault = 0x10000000;
+constexpr unsigned int kMaxFetchSizeDefault = 0x10000000;
 
 class FastbootDevice;
 
@@ -50,3 +51,4 @@
 bool OemCmdHandler(FastbootDevice* device, const std::vector<std::string>& args);
 bool GsiHandler(FastbootDevice* device, const std::vector<std::string>& args);
 bool SnapshotUpdateHandler(FastbootDevice* device, const std::vector<std::string>& args);
+bool FetchHandler(FastbootDevice* device, const std::vector<std::string>& args);
diff --git a/fastboot/device/fastboot_device.cpp b/fastboot/device/fastboot_device.cpp
index 35f3de0..64a934d 100644
--- a/fastboot/device/fastboot_device.cpp
+++ b/fastboot/device/fastboot_device.cpp
@@ -61,6 +61,7 @@
               {FB_CMD_OEM, OemCmdHandler},
               {FB_CMD_GSI, GsiHandler},
               {FB_CMD_SNAPSHOT_UPDATE, SnapshotUpdateHandler},
+              {FB_CMD_FETCH, FetchHandler},
       }),
       boot_control_hal_(IBootControl::getService()),
       health_hal_(get_health_service()),
@@ -137,14 +138,18 @@
 }
 
 bool FastbootDevice::HandleData(bool read, std::vector<char>* data) {
-    auto read_write_data_size = read ? this->get_transport()->Read(data->data(), data->size())
-                                     : this->get_transport()->Write(data->data(), data->size());
+    return HandleData(read, data->data(), data->size());
+}
+
+bool FastbootDevice::HandleData(bool read, char* data, uint64_t size) {
+    auto read_write_data_size = read ? this->get_transport()->Read(data, size)
+                                     : this->get_transport()->Write(data, size);
     if (read_write_data_size == -1) {
         LOG(ERROR) << (read ? "read from" : "write to") << " transport failed";
         return false;
     }
-    if (static_cast<size_t>(read_write_data_size) != data->size()) {
-        LOG(ERROR) << (read ? "read" : "write") << " expected " << data->size() << " bytes, got "
+    if (static_cast<size_t>(read_write_data_size) != size) {
+        LOG(ERROR) << (read ? "read" : "write") << " expected " << size << " bytes, got "
                    << read_write_data_size;
         return false;
     }
diff --git a/fastboot/device/fastboot_device.h b/fastboot/device/fastboot_device.h
index 23be721..3536136 100644
--- a/fastboot/device/fastboot_device.h
+++ b/fastboot/device/fastboot_device.h
@@ -40,6 +40,7 @@
     void ExecuteCommands();
     bool WriteStatus(FastbootResult result, const std::string& message);
     bool HandleData(bool read, std::vector<char>* data);
+    bool HandleData(bool read, char* data, uint64_t size);
     std::string GetCurrentSlot();
 
     // Shortcuts for writing status results.
diff --git a/fastboot/device/utility.cpp b/fastboot/device/utility.cpp
index 7c6ac89..f9267e0 100644
--- a/fastboot/device/utility.cpp
+++ b/fastboot/device/utility.cpp
@@ -77,7 +77,8 @@
 
 }  // namespace
 
-bool OpenPartition(FastbootDevice* device, const std::string& name, PartitionHandle* handle) {
+bool OpenPartition(FastbootDevice* device, const std::string& name, PartitionHandle* handle,
+                   bool read) {
     // We prioritize logical partitions over physical ones, and do this
     // consistently for other partition operations (like getvar:partition-size).
     if (LogicalPartitionExists(device, name)) {
@@ -89,7 +90,9 @@
         return false;
     }
 
-    unique_fd fd(TEMP_FAILURE_RETRY(open(handle->path().c_str(), O_WRONLY | O_EXCL)));
+    int flags = (read ? O_RDONLY : O_WRONLY);
+    flags |= (O_EXCL | O_CLOEXEC | O_BINARY);
+    unique_fd fd(TEMP_FAILURE_RETRY(open(handle->path().c_str(), flags)));
     if (fd < 0) {
         PLOG(ERROR) << "Failed to open block device: " << handle->path();
         return false;
diff --git a/fastboot/device/utility.h b/fastboot/device/utility.h
index 3b71ef0..c2646d7 100644
--- a/fastboot/device/utility.h
+++ b/fastboot/device/utility.h
@@ -75,7 +75,11 @@
 std::optional<std::string> FindPhysicalPartition(const std::string& name);
 bool LogicalPartitionExists(FastbootDevice* device, const std::string& name,
                             bool* is_zero_length = nullptr);
-bool OpenPartition(FastbootDevice* device, const std::string& name, PartitionHandle* handle);
+
+// If read, partition is readonly. Else it is write only.
+bool OpenPartition(FastbootDevice* device, const std::string& name, PartitionHandle* handle,
+                   bool read = false);
+
 bool GetSlotNumber(const std::string& slot, android::hardware::boot::V1_0::Slot* number);
 std::vector<std::string> ListPartitions(FastbootDevice* device);
 bool GetDeviceLockStatus();
diff --git a/fastboot/device/variables.cpp b/fastboot/device/variables.cpp
index e7d8bc3..ee1eed8 100644
--- a/fastboot/device/variables.cpp
+++ b/fastboot/device/variables.cpp
@@ -33,6 +33,12 @@
 #include "flashing.h"
 #include "utility.h"
 
+#ifdef FB_ENABLE_FETCH
+static constexpr bool kEnableFetch = true;
+#else
+static constexpr bool kEnableFetch = false;
+#endif
+
 using ::android::hardware::boot::V1_0::BoolResult;
 using ::android::hardware::boot::V1_0::Slot;
 using ::android::hardware::boot::V1_1::MergeStatus;
@@ -509,3 +515,13 @@
     *message = android::base::GetProperty("ro.treble.enabled", "");
     return true;
 }
+
+bool GetMaxFetchSize(FastbootDevice* /* device */, const std::vector<std::string>& /* args */,
+                     std::string* message) {
+    if (!kEnableFetch) {
+        *message = "fetch not supported on user builds";
+        return false;
+    }
+    *message = android::base::StringPrintf("0x%X", kMaxFetchSizeDefault);
+    return true;
+}
diff --git a/fastboot/device/variables.h b/fastboot/device/variables.h
index c11e472..f40a025 100644
--- a/fastboot/device/variables.h
+++ b/fastboot/device/variables.h
@@ -80,6 +80,8 @@
                            std::string* message);
 bool GetTrebleEnabled(FastbootDevice* device, const std::vector<std::string>& args,
                       std::string* message);
+bool GetMaxFetchSize(FastbootDevice* /* device */, const std::vector<std::string>& /* args */,
+                     std::string* message);
 
 // Helpers for getvar all.
 std::vector<std::vector<std::string>> GetAllPartitionArgsWithSlot(FastbootDevice* device);
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 38be934..94efeea 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -76,12 +76,15 @@
 #include "udp.h"
 #include "usb.h"
 #include "util.h"
+#include "vendor_boot_img_utils.h"
 
+using android::base::borrowed_fd;
 using android::base::ReadFully;
 using android::base::Split;
 using android::base::Trim;
 using android::base::unique_fd;
 using namespace std::string_literals;
+using namespace std::placeholders;
 
 static const char* serial = nullptr;
 
@@ -114,7 +117,7 @@
     enum fb_buffer_type type;
     void* data;
     int64_t sz;
-    int fd;
+    unique_fd fd;
     int64_t image_size;
 };
 
@@ -414,6 +417,7 @@
             " snapshot-update merge      On devices that support snapshot-based updates, finish\n"
             "                            an in-progress update if it is in the \"merging\"\n"
             "                            phase.\n"
+            " fetch PARTITION            Fetch a partition image from the device."
             "\n"
             "boot image:\n"
             " boot KERNEL [RAMDISK [SECOND]]\n"
@@ -466,7 +470,7 @@
             " --version                  Display version.\n"
             " --help, -h                 Show this message.\n"
         );
-    // clang-format off
+    // clang-format on
     return 0;
 }
 
@@ -640,14 +644,14 @@
     }
 }
 
-static int unzip_to_file(ZipArchiveHandle zip, const char* entry_name) {
+static unique_fd unzip_to_file(ZipArchiveHandle zip, const char* entry_name) {
     unique_fd fd(make_temporary_fd(entry_name));
 
     ZipEntry64 zip_entry;
     if (FindEntry(zip, entry_name, &zip_entry) != 0) {
         fprintf(stderr, "archive does not contain '%s'\n", entry_name);
         errno = ENOENT;
-        return -1;
+        return unique_fd();
     }
 
     fprintf(stderr, "extracting %s (%" PRIu64 " MB) to disk...", entry_name,
@@ -664,7 +668,7 @@
 
     fprintf(stderr, " took %.3fs\n", now() - start);
 
-    return fd.release();
+    return fd;
 }
 
 static void CheckRequirement(const std::string& cur_product, const std::string& var,
@@ -851,24 +855,23 @@
     return out_s;
 }
 
-static int64_t get_target_sparse_limit() {
-    std::string max_download_size;
-    if (fb->GetVar("max-download-size", &max_download_size) != fastboot::SUCCESS ||
-        max_download_size.empty()) {
-        verbose("target didn't report max-download-size");
+static uint64_t get_uint_var(const char* var_name) {
+    std::string value_str;
+    if (fb->GetVar(var_name, &value_str) != fastboot::SUCCESS || value_str.empty()) {
+        verbose("target didn't report %s", var_name);
         return 0;
     }
 
     // Some bootloaders (angler, for example) send spurious whitespace too.
-    max_download_size = android::base::Trim(max_download_size);
+    value_str = android::base::Trim(value_str);
 
-    uint64_t limit;
-    if (!android::base::ParseUint(max_download_size, &limit)) {
-        fprintf(stderr, "couldn't parse max-download-size '%s'\n", max_download_size.c_str());
+    uint64_t value;
+    if (!android::base::ParseUint(value_str, &value)) {
+        fprintf(stderr, "couldn't parse %s '%s'\n", var_name, value_str.c_str());
         return 0;
     }
-    if (limit > 0) verbose("target reported max download size of %" PRId64 " bytes", limit);
-    return limit;
+    if (value > 0) verbose("target reported %s of %" PRId64 " bytes", var_name, value);
+    return value;
 }
 
 static int64_t get_sparse_limit(int64_t size) {
@@ -877,7 +880,7 @@
         // Unlimited, so see what the target device's limit is.
         // TODO: shouldn't we apply this limit even if you've used -S?
         if (target_sparse_limit == -1) {
-            target_sparse_limit = get_target_sparse_limit();
+            target_sparse_limit = static_cast<int64_t>(get_uint_var("max-download-size"));
         }
         if (target_sparse_limit > 0) {
             limit = target_sparse_limit;
@@ -893,7 +896,7 @@
     return 0;
 }
 
-static bool load_buf_fd(int fd, struct fastboot_buffer* buf) {
+static bool load_buf_fd(unique_fd fd, struct fastboot_buffer* buf) {
     int64_t sz = get_file_size(fd);
     if (sz == -1) {
         return false;
@@ -918,7 +921,7 @@
     } else {
         buf->type = FB_BUFFER_FD;
         buf->data = nullptr;
-        buf->fd = fd;
+        buf->fd = std::move(fd);
         buf->sz = sz;
     }
 
@@ -941,7 +944,7 @@
         return false;
     }
 
-    return load_buf_fd(fd.release(), buf);
+    return load_buf_fd(std::move(fd), buf);
 }
 
 static void rewrite_vbmeta_buffer(struct fastboot_buffer* buf, bool vbmeta_in_boot) {
@@ -987,12 +990,11 @@
         data[flags_offset] |= 0x02;
     }
 
-    int fd = make_temporary_fd("vbmeta rewriting");
+    unique_fd fd(make_temporary_fd("vbmeta rewriting"));
     if (!android::base::WriteStringToFd(data, fd)) {
         die("Failed writing to modified vbmeta");
     }
-    close(buf->fd);
-    buf->fd = fd;
+    buf->fd = std::move(fd);
     lseek(fd, 0, SEEK_SET);
 }
 
@@ -1012,21 +1014,28 @@
     return var;
 }
 
+static uint64_t get_partition_size(const std::string& partition) {
+    std::string partition_size_str;
+    if (fb->GetVar("partition-size:" + partition, &partition_size_str) != fastboot::SUCCESS) {
+        die("cannot get partition size for %s", partition.c_str());
+    }
+
+    partition_size_str = fb_fix_numeric_var(partition_size_str);
+    uint64_t partition_size;
+    if (!android::base::ParseUint(partition_size_str, &partition_size)) {
+        die("Couldn't parse partition size '%s'.", partition_size_str.c_str());
+    }
+    return partition_size;
+}
+
 static void copy_boot_avb_footer(const std::string& partition, struct fastboot_buffer* buf) {
     if (buf->sz < AVB_FOOTER_SIZE) {
         return;
     }
 
-    std::string partition_size_str;
-    if (fb->GetVar("partition-size:" + partition, &partition_size_str) != fastboot::SUCCESS) {
-        die("cannot get boot partition size");
-    }
+    // If overflows and negative, it should be < buf->sz.
+    int64_t partition_size = static_cast<int64_t>(get_partition_size(partition));
 
-    partition_size_str = fb_fix_numeric_var(partition_size_str);
-    int64_t partition_size;
-    if (!android::base::ParseInt(partition_size_str, &partition_size)) {
-        die("Couldn't parse partition size '%s'.", partition_size_str.c_str());
-    }
     if (partition_size == buf->sz) {
         return;
     }
@@ -1044,7 +1053,7 @@
         return;
     }
 
-    int fd = make_temporary_fd("boot rewriting");
+    unique_fd fd(make_temporary_fd("boot rewriting"));
     if (!android::base::WriteStringToFd(data, fd)) {
         die("Failed writing to modified boot");
     }
@@ -1052,8 +1061,7 @@
     if (!android::base::WriteStringToFd(data.substr(footer_offset), fd)) {
         die("Failed copying AVB footer in boot");
     }
-    close(buf->fd);
-    buf->fd = fd;
+    buf->fd = std::move(fd);
     buf->sz = partition_size;
     lseek(fd, 0, SEEK_SET);
 }
@@ -1185,8 +1193,10 @@
                              const std::function<void(const std::string&)>& func, bool force_slot) {
     std::string has_slot;
     std::string current_slot;
+    // |part| can be vendor_boot:default. Append slot to the first token.
+    auto part_tokens = android::base::Split(part, ":");
 
-    if (fb->GetVar("has-slot:" + part, &has_slot) != fastboot::SUCCESS) {
+    if (fb->GetVar("has-slot:" + part_tokens[0], &has_slot) != fastboot::SUCCESS) {
         /* If has-slot is not supported, the answer is no. */
         has_slot = "no";
     }
@@ -1196,14 +1206,15 @@
             if (current_slot == "") {
                 die("Failed to identify current slot");
             }
-            func(part + "_" + current_slot);
+            part_tokens[0] += "_" + current_slot;
         } else {
-            func(part + '_' + slot);
+            part_tokens[0] += "_" + slot;
         }
+        func(android::base::Join(part_tokens, ":"));
     } else {
         if (force_slot && slot != "") {
-             fprintf(stderr, "Warning: %s does not support slots, and slot %s was requested.\n",
-                     part.c_str(), slot.c_str());
+            fprintf(stderr, "Warning: %s does not support slots, and slot %s was requested.\n",
+                    part_tokens[0].c_str(), slot.c_str());
         }
         func(part);
     }
@@ -1217,10 +1228,13 @@
 static void do_for_partitions(const std::string& part, const std::string& slot,
                               const std::function<void(const std::string&)>& func, bool force_slot) {
     std::string has_slot;
+    // |part| can be vendor_boot:default. Query has-slot on the first token only.
+    auto part_tokens = android::base::Split(part, ":");
 
     if (slot == "all") {
-        if (fb->GetVar("has-slot:" + part, &has_slot) != fastboot::SUCCESS) {
-            die("Could not check if partition %s has slot %s", part.c_str(), slot.c_str());
+        if (fb->GetVar("has-slot:" + part_tokens[0], &has_slot) != fastboot::SUCCESS) {
+            die("Could not check if partition %s has slot %s", part_tokens[0].c_str(),
+                slot.c_str());
         }
         if (has_slot == "yes") {
             for (int i=0; i < get_slot_count(); i++) {
@@ -1247,7 +1261,74 @@
     return android::base::StartsWith(value, "system_");
 }
 
+// Fetch a partition from the device to a given fd. This is a wrapper over FetchToFd to fetch
+// the full image.
+static uint64_t fetch_partition(const std::string& partition, borrowed_fd fd) {
+    uint64_t fetch_size = get_uint_var(FB_VAR_MAX_FETCH_SIZE);
+    if (fetch_size == 0) {
+        die("Unable to get %s. Device does not support fetch command.", FB_VAR_MAX_FETCH_SIZE);
+    }
+    uint64_t partition_size = get_partition_size(partition);
+    if (partition_size <= 0) {
+        die("Invalid partition size for partition %s: %" PRId64, partition.c_str(), partition_size);
+    }
+
+    uint64_t offset = 0;
+    while (offset < partition_size) {
+        uint64_t chunk_size = std::min(fetch_size, partition_size - offset);
+        if (fb->FetchToFd(partition, fd, offset, chunk_size) != fastboot::RetCode::SUCCESS) {
+            die("Unable to fetch %s (offset=%" PRIx64 ", size=%" PRIx64 ")", partition.c_str(),
+                offset, chunk_size);
+        }
+        offset += chunk_size;
+    }
+    return partition_size;
+}
+
+static void do_fetch(const std::string& partition, const std::string& slot_override,
+                     const std::string& outfile) {
+    unique_fd fd(TEMP_FAILURE_RETRY(
+            open(outfile.c_str(), O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_BINARY, 0644)));
+    auto fetch = std::bind(fetch_partition, _1, borrowed_fd(fd));
+    do_for_partitions(partition, slot_override, fetch, false /* force slot */);
+}
+
+// Return immediately if not flashing a vendor boot image. If flashing a vendor boot image,
+// repack vendor_boot image with an updated ramdisk. After execution, buf is set
+// to the new image to flash, and return value is the real partition name to flash.
+static std::string repack_ramdisk(const char* pname, struct fastboot_buffer* buf) {
+    std::string_view pname_sv{pname};
+
+    if (!android::base::StartsWith(pname_sv, "vendor_boot:") &&
+        !android::base::StartsWith(pname_sv, "vendor_boot_a:") &&
+        !android::base::StartsWith(pname_sv, "vendor_boot_b:")) {
+        return std::string(pname_sv);
+    }
+    if (buf->type != FB_BUFFER_FD) {
+        die("Flashing sparse vendor ramdisk image is not supported.");
+    }
+    if (buf->sz <= 0) {
+        die("repack_ramdisk() sees negative size: %" PRId64, buf->sz);
+    }
+    std::string partition(pname_sv.substr(0, pname_sv.find(':')));
+    std::string ramdisk(pname_sv.substr(pname_sv.find(':') + 1));
+
+    unique_fd vendor_boot(make_temporary_fd("vendor boot repack"));
+    uint64_t vendor_boot_size = fetch_partition(partition, vendor_boot);
+    auto repack_res = replace_vendor_ramdisk(vendor_boot, vendor_boot_size, ramdisk, buf->fd,
+                                             static_cast<uint64_t>(buf->sz));
+    if (!repack_res.ok()) {
+        die("%s", repack_res.error().message().c_str());
+    }
+
+    buf->fd = std::move(vendor_boot);
+    buf->sz = vendor_boot_size;
+    buf->image_size = vendor_boot_size;
+    return partition;
+}
+
 static void do_flash(const char* pname, const char* fname) {
+    verbose("Do flash %s %s", pname, fname);
     struct fastboot_buffer buf;
 
     if (!load_buf(fname, &buf)) {
@@ -1256,7 +1337,8 @@
     if (is_logical(pname)) {
         fb->ResizePartition(pname, std::to_string(buf.image_size));
     }
-    flash_buf(pname, &buf);
+    std::string flash_pname = repack_ramdisk(pname, &buf);
+    flash_buf(flash_pname, &buf);
 }
 
 // Sets slot_override as the active slot. If slot_override is blank,
@@ -1310,7 +1392,7 @@
 class ImageSource {
   public:
     virtual bool ReadFile(const std::string& name, std::vector<char>* out) const = 0;
-    virtual int OpenFile(const std::string& name) const = 0;
+    virtual unique_fd OpenFile(const std::string& name) const = 0;
 };
 
 class FlashAllTool {
@@ -1428,8 +1510,8 @@
 void FlashAllTool::FlashImages(const std::vector<std::pair<const Image*, std::string>>& images) {
     for (const auto& [image, slot] : images) {
         fastboot_buffer buf;
-        int fd = source_.OpenFile(image->img_name);
-        if (fd < 0 || !load_buf_fd(fd, &buf)) {
+        unique_fd fd = source_.OpenFile(image->img_name);
+        if (fd < 0 || !load_buf_fd(std::move(fd), &buf)) {
             if (image->optional_if_no_image) {
                 continue;
             }
@@ -1494,7 +1576,7 @@
   public:
     explicit ZipImageSource(ZipArchiveHandle zip) : zip_(zip) {}
     bool ReadFile(const std::string& name, std::vector<char>* out) const override;
-    int OpenFile(const std::string& name) const override;
+    unique_fd OpenFile(const std::string& name) const override;
 
   private:
     ZipArchiveHandle zip_;
@@ -1504,7 +1586,7 @@
     return UnzipToMemory(zip_, name, out);
 }
 
-int ZipImageSource::OpenFile(const std::string& name) const {
+unique_fd ZipImageSource::OpenFile(const std::string& name) const {
     return unzip_to_file(zip_, name.c_str());
 }
 
@@ -1524,7 +1606,7 @@
 class LocalImageSource final : public ImageSource {
   public:
     bool ReadFile(const std::string& name, std::vector<char>* out) const override;
-    int OpenFile(const std::string& name) const override;
+    unique_fd OpenFile(const std::string& name) const override;
 };
 
 bool LocalImageSource::ReadFile(const std::string& name, std::vector<char>* out) const {
@@ -1535,9 +1617,9 @@
     return ReadFileToVector(path, out);
 }
 
-int LocalImageSource::OpenFile(const std::string& name) const {
+unique_fd LocalImageSource::OpenFile(const std::string& name) const {
     auto path = find_item_given_name(name);
-    return open(path.c_str(), O_RDONLY | O_BINARY);
+    return unique_fd(TEMP_FAILURE_RETRY(open(path.c_str(), O_RDONLY | O_BINARY)));
 }
 
 static void do_flashall(const std::string& slot_override, bool skip_secondary, bool wipe) {
@@ -1656,7 +1738,7 @@
     if (fd == -1) {
         die("Cannot open generated image: %s", strerror(errno));
     }
-    if (!load_buf_fd(fd.release(), &buf)) {
+    if (!load_buf_fd(std::move(fd), &buf)) {
         die("Cannot read image: %s", strerror(errno));
     }
     flash_buf(partition, &buf);
@@ -2169,6 +2251,10 @@
                 syntax_error("expected: snapshot-update [cancel|merge]");
             }
             fb->SnapshotUpdateCommand(arg);
+        } else if (command == FB_CMD_FETCH) {
+            std::string partition = next_arg(&args);
+            std::string outfile = next_arg(&args);
+            do_fetch(partition, slot_override, outfile);
         } else {
             syntax_error("unknown command %s", command.c_str());
         }
diff --git a/fastboot/fastboot_driver.cpp b/fastboot/fastboot_driver.cpp
index 8d534ea..14ee785 100644
--- a/fastboot/fastboot_driver.cpp
+++ b/fastboot/fastboot_driver.cpp
@@ -30,6 +30,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -42,14 +43,17 @@
 
 #include <android-base/file.h>
 #include <android-base/mapped_file.h>
+#include <android-base/parseint.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
+#include <storage_literals/storage_literals.h>
 
 #include "constants.h"
 #include "transport.h"
 
 using android::base::StringPrintf;
+using namespace android::storage_literals;
 
 namespace fastboot {
 
@@ -297,41 +301,85 @@
     return result;
 }
 
-RetCode FastBootDriver::UploadInner(const std::string& outfile, std::string* response,
-                                    std::vector<std::string>* info) {
+// This function executes cmd, then expect a "DATA" response with a number N, followed
+// by N bytes, and another response.
+// This is the common way for the device to send data to the driver used by upload and fetch.
+RetCode FastBootDriver::RunAndReadBuffer(
+        const std::string& cmd, std::string* response, std::vector<std::string>* info,
+        const std::function<RetCode(const char* data, uint64_t size)>& write_fn) {
     RetCode ret;
     int dsize = 0;
-    if ((ret = RawCommand(FB_CMD_UPLOAD, response, info, &dsize))) {
-        error_ = "Upload request failed: " + error_;
+    if ((ret = RawCommand(cmd, response, info, &dsize))) {
+        error_ = android::base::StringPrintf("%s request failed: %s", cmd.c_str(), error_.c_str());
         return ret;
     }
 
-    if (!dsize) {
-        error_ = "Upload request failed, device reports 0 bytes available";
+    if (dsize <= 0) {
+        error_ = android::base::StringPrintf("%s request failed, device reports %d bytes available",
+                                             cmd.c_str(), dsize);
         return BAD_DEV_RESP;
     }
 
-    std::vector<char> data;
-    data.resize(dsize);
-
-    if ((ret = ReadBuffer(data))) {
-        return ret;
+    const uint64_t total_size = dsize;
+    const uint64_t buf_size = std::min<uint64_t>(total_size, 1_MiB);
+    std::vector<char> data(buf_size);
+    uint64_t current_offset = 0;
+    while (current_offset < total_size) {
+        uint64_t remaining = total_size - current_offset;
+        uint64_t chunk_size = std::min(buf_size, remaining);
+        if ((ret = ReadBuffer(data.data(), chunk_size)) != SUCCESS) {
+            return ret;
+        }
+        if ((ret = write_fn(data.data(), chunk_size)) != SUCCESS) {
+            return ret;
+        }
+        current_offset += chunk_size;
     }
+    return HandleResponse(response, info);
+}
 
+RetCode FastBootDriver::UploadInner(const std::string& outfile, std::string* response,
+                                    std::vector<std::string>* info) {
     std::ofstream ofs;
     ofs.open(outfile, std::ofstream::out | std::ofstream::binary);
     if (ofs.fail()) {
         error_ = android::base::StringPrintf("Failed to open '%s'", outfile.c_str());
         return IO_ERROR;
     }
-    ofs.write(data.data(), data.size());
-    if (ofs.fail() || ofs.bad()) {
-        error_ = android::base::StringPrintf("Writing to '%s' failed", outfile.c_str());
-        return IO_ERROR;
-    }
+    auto write_fn = [&](const char* data, uint64_t size) {
+        ofs.write(data, size);
+        if (ofs.fail() || ofs.bad()) {
+            error_ = android::base::StringPrintf("Writing to '%s' failed", outfile.c_str());
+            return IO_ERROR;
+        }
+        return SUCCESS;
+    };
+    RetCode ret = RunAndReadBuffer(FB_CMD_UPLOAD, response, info, write_fn);
     ofs.close();
+    return ret;
+}
 
-    return HandleResponse(response, info);
+RetCode FastBootDriver::FetchToFd(const std::string& partition, android::base::borrowed_fd fd,
+                                  int64_t offset, int64_t size, std::string* response,
+                                  std::vector<std::string>* info) {
+    prolog_(android::base::StringPrintf("Fetching %s (offset=%" PRIx64 ", size=%" PRIx64 ")",
+                                        partition.c_str(), offset, size));
+    std::string cmd = FB_CMD_FETCH ":" + partition;
+    if (offset >= 0) {
+        cmd += android::base::StringPrintf(":0x%08" PRIx64, offset);
+        if (size >= 0) {
+            cmd += android::base::StringPrintf(":0x%08" PRIx64, size);
+        }
+    }
+    RetCode ret = RunAndReadBuffer(cmd, response, info, [&](const char* data, uint64_t size) {
+        if (!android::base::WriteFully(fd, data, size)) {
+            error_ = android::base::StringPrintf("Cannot write: %s", strerror(errno));
+            return IO_ERROR;
+        }
+        return SUCCESS;
+    });
+    epilog_(ret);
+    return ret;
 }
 
 // Helpers
@@ -524,11 +572,6 @@
     return SUCCESS;
 }
 
-RetCode FastBootDriver::ReadBuffer(std::vector<char>& buf) {
-    // Read the buffer
-    return ReadBuffer(buf.data(), buf.size());
-}
-
 RetCode FastBootDriver::ReadBuffer(void* buf, size_t size) {
     // Read the buffer
     ssize_t tmp = transport_->Read(buf, size);
diff --git a/fastboot/fastboot_driver.h b/fastboot/fastboot_driver.h
index 7265632..f1c094f 100644
--- a/fastboot/fastboot_driver.h
+++ b/fastboot/fastboot_driver.h
@@ -34,6 +34,7 @@
 
 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
+#include <android-base/unique_fd.h>
 #include <bootimg.h>
 #include <inttypes.h>
 #include <sparse/sparse.h>
@@ -106,6 +107,9 @@
                    std::vector<std::string>* info = nullptr);
     RetCode SnapshotUpdateCommand(const std::string& command, std::string* response = nullptr,
                                   std::vector<std::string>* info = nullptr);
+    RetCode FetchToFd(const std::string& partition, android::base::borrowed_fd fd,
+                      int64_t offset = -1, int64_t size = -1, std::string* response = nullptr,
+                      std::vector<std::string>* info = nullptr);
 
     /* HIGHER LEVEL COMMANDS -- Composed of the commands above */
     RetCode FlashPartition(const std::string& partition, const std::vector<char>& data);
@@ -149,11 +153,13 @@
     RetCode SendBuffer(const std::vector<char>& buf);
     RetCode SendBuffer(const void* buf, size_t size);
 
-    RetCode ReadBuffer(std::vector<char>& buf);
     RetCode ReadBuffer(void* buf, size_t size);
 
     RetCode UploadInner(const std::string& outfile, std::string* response = nullptr,
                         std::vector<std::string>* info = nullptr);
+    RetCode RunAndReadBuffer(const std::string& cmd, std::string* response,
+                             std::vector<std::string>* info,
+                             const std::function<RetCode(const char*, uint64_t)>& write_fn);
 
     int SparseWriteCallback(std::vector<char>& tpbuf, const char* data, size_t len);
 
diff --git a/fastboot/fuzzy_fastboot/main.cpp b/fastboot/fuzzy_fastboot/main.cpp
index 34ab32c..b6beaf9 100644
--- a/fastboot/fuzzy_fastboot/main.cpp
+++ b/fastboot/fuzzy_fastboot/main.cpp
@@ -43,8 +43,10 @@
 #include <thread>
 #include <vector>
 
+#include <android-base/file.h>
 #include <android-base/parseint.h>
 #include <android-base/stringprintf.h>
+#include <android-base/strings.h>
 #include <gtest/gtest.h>
 #include <sparse/sparse.h>
 
@@ -349,22 +351,35 @@
     EXPECT_TRUE(var == "yes" || var == "no") << "getvar:battery-soc-ok must be 'yes' or 'no'";
 }
 
+void AssertHexUint32(const std::string& name, const std::string& var) {
+    ASSERT_NE(var, "") << "getvar:" << name << " responded with empty string";
+    // This must start with 0x
+    ASSERT_FALSE(isspace(var.front()))
+            << "getvar:" << name << " responded with a string with leading whitespace";
+    ASSERT_FALSE(var.compare(0, 2, "0x"))
+            << "getvar:" << name << " responded with a string that does not start with 0x...";
+    int64_t size = strtoll(var.c_str(), nullptr, 16);
+    ASSERT_GT(size, 0) << "'" + var + "' is not a valid response from getvar:" << name;
+    // At most 32-bits
+    ASSERT_LE(size, std::numeric_limits<uint32_t>::max())
+            << "getvar:" << name << " must fit in a uint32_t";
+    ASSERT_LE(var.size(), FB_RESPONSE_SZ - 4)
+            << "getvar:" << name << " responded with too large of string: " + var;
+}
+
 TEST_F(Conformance, GetVarDownloadSize) {
     std::string var;
     EXPECT_EQ(fb->GetVar("max-download-size", &var), SUCCESS) << "getvar:max-download-size failed";
-    EXPECT_NE(var, "") << "getvar:max-download-size responded with empty string";
-    // This must start with 0x
-    EXPECT_FALSE(isspace(var.front()))
-            << "getvar:max-download-size responded with a string with leading whitespace";
-    EXPECT_FALSE(var.compare(0, 2, "0x"))
-            << "getvar:max-download-size responded with a string that does not start with 0x...";
-    int64_t size = strtoll(var.c_str(), nullptr, 16);
-    EXPECT_GT(size, 0) << "'" + var + "' is not a valid response from getvar:max-download-size";
-    // At most 32-bits
-    EXPECT_LE(size, std::numeric_limits<uint32_t>::max())
-            << "getvar:max-download-size must fit in a uint32_t";
-    EXPECT_LE(var.size(), FB_RESPONSE_SZ - 4)
-            << "getvar:max-download-size responded with too large of string: " + var;
+    AssertHexUint32("max-download-size", var);
+}
+
+// If fetch is supported, getvar:max-fetch-size must return a hex string.
+TEST_F(Conformance, GetVarFetchSize) {
+    std::string var;
+    if (SUCCESS != fb->GetVar("max-fetch-size", &var)) {
+        GTEST_SKIP() << "getvar:max-fetch-size failed";
+    }
+    AssertHexUint32("max-fetch-size", var);
 }
 
 TEST_F(Conformance, GetVarAll) {
@@ -656,6 +671,33 @@
     EXPECT_EQ(fb->Partitions(&parts), SUCCESS) << "getvar:all failed in unlocked mode";
 }
 
+// If the implementation supports getvar:max-fetch-size, it must also support fetch:vendor_boot*.
+TEST_F(UnlockPermissions, FetchVendorBoot) {
+    std::string var;
+    uint64_t fetch_size;
+    if (fb->GetVar("max-fetch-size", &var) != SUCCESS) {
+        GTEST_SKIP() << "This test is skipped because fetch is not supported.";
+    }
+    ASSERT_FALSE(var.empty());
+    ASSERT_TRUE(android::base::ParseUint(var, &fetch_size)) << var << " is not an integer";
+    std::vector<std::tuple<std::string, uint64_t>> parts;
+    EXPECT_EQ(fb->Partitions(&parts), SUCCESS) << "getvar:all failed";
+    for (const auto& [partition, partition_size] : parts) {
+        if (!android::base::StartsWith(partition, "vendor_boot")) continue;
+        TemporaryFile fetched;
+
+        uint64_t offset = 0;
+        while (offset < partition_size) {
+            uint64_t chunk_size = std::min(fetch_size, partition_size - offset);
+            auto ret = fb->FetchToFd(partition, fetched.fd, offset, chunk_size);
+            ASSERT_EQ(fastboot::RetCode::SUCCESS, ret)
+                    << "Unable to fetch " << partition << " (offset=" << offset
+                    << ", size=" << chunk_size << ")";
+            offset += chunk_size;
+        }
+    }
+}
+
 TEST_F(LockPermissions, DownloadFlash) {
     std::vector<char> buf{'a', 'o', 's', 'p'};
     EXPECT_EQ(fb->Download(buf), SUCCESS) << "Download failed in locked mode";
@@ -717,6 +759,16 @@
     EXPECT_GT(resp.size(), 0) << "No error message was returned by device after FAIL";
 }
 
+TEST_F(LockPermissions, FetchVendorBoot) {
+    std::vector<std::tuple<std::string, uint64_t>> parts;
+    EXPECT_EQ(fb->Partitions(&parts), SUCCESS) << "getvar:all failed";
+    for (const auto& [partition, _] : parts) {
+        TemporaryFile fetched;
+        ASSERT_EQ(fb->FetchToFd(partition, fetched.fd, 0, 0), DEVICE_FAIL)
+                << "fetch:" << partition << ":0:0 did not fail in locked mode";
+    }
+}
+
 TEST_F(Fuzz, DownloadSize) {
     std::string var;
     EXPECT_EQ(fb->GetVar("max-download-size", &var), SUCCESS) << "getvar:max-download-size failed";
diff --git a/fastboot/testdata/Android.bp b/fastboot/testdata/Android.bp
new file mode 100644
index 0000000..5debf5e
--- /dev/null
+++ b/fastboot/testdata/Android.bp
@@ -0,0 +1,136 @@
+// Copyright (C) 2021 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.
+
+python_binary_host {
+    name: "fastboot_gen_rand",
+    visibility: [":__subpackages__"],
+    srcs: ["fastboot_gen_rand.py"],
+}
+
+genrule_defaults {
+    name: "fastboot_test_data_gen_defaults",
+    visibility: ["//system/core/fastboot"],
+    tools: [
+        "fastboot_gen_rand",
+    ],
+}
+
+// Genrules for components of test vendor boot image.
+
+// Fake dtb image.
+genrule {
+    name: "fastboot_test_dtb",
+    defaults: ["fastboot_test_data_gen_defaults"],
+    out: ["test_dtb.img"],
+    cmd: "$(location fastboot_gen_rand) --seed dtb --length 1024 > $(out)",
+}
+
+// Fake bootconfig image.
+genrule {
+    name: "fastboot_test_bootconfig",
+    defaults: ["fastboot_test_data_gen_defaults"],
+    out: ["test_bootconfig.img"],
+    cmd: "$(location fastboot_gen_rand) --seed bootconfig --length 1024 > $(out)",
+}
+
+// Fake vendor ramdisk with type "none".
+genrule {
+    name: "fastboot_test_vendor_ramdisk_none",
+    defaults: ["fastboot_test_data_gen_defaults"],
+    out: ["test_vendor_ramdisk_none.img"],
+    cmd: "$(location fastboot_gen_rand) --seed vendor_ramdisk_none --length 1024 > $(out)",
+}
+
+// Fake vendor ramdisk with type "platform".
+genrule {
+    name: "fastboot_test_vendor_ramdisk_platform",
+    defaults: ["fastboot_test_data_gen_defaults"],
+    out: ["test_vendor_ramdisk_platform.img"],
+    cmd: "$(location fastboot_gen_rand) --seed vendor_ramdisk_platform --length 1024 > $(out)",
+}
+
+// Fake replacement ramdisk.
+genrule {
+    name: "fastboot_test_vendor_ramdisk_replace",
+    defaults: ["fastboot_test_data_gen_defaults"],
+    out: ["test_vendor_ramdisk_replace.img"],
+    cmd: "$(location fastboot_gen_rand) --seed replace --length 3072 > $(out)",
+}
+
+// Genrules for test vendor boot images.
+
+fastboot_sign_test_image = "$(location avbtool) add_hash_footer --salt 00 --image $(out) " +
+    "--partition_name vendor_boot --partition_size $$(( 1 * 1024 * 1024 ))"
+
+genrule_defaults {
+    name: "fastboot_test_vendor_boot_gen_defaults",
+    defaults: ["fastboot_test_data_gen_defaults"],
+    tools: [
+        "avbtool",
+        "mkbootimg",
+    ],
+}
+
+genrule {
+    name: "fastboot_test_vendor_boot_v3",
+    defaults: ["fastboot_test_vendor_boot_gen_defaults"],
+    out: ["vendor_boot_v3.img"],
+    srcs: [
+        ":fastboot_test_dtb",
+        ":fastboot_test_vendor_ramdisk_none",
+    ],
+    cmd: "$(location mkbootimg) --header_version 3 " +
+        "--vendor_ramdisk $(location :fastboot_test_vendor_ramdisk_none) " +
+        "--dtb $(location :fastboot_test_dtb) " +
+        "--vendor_boot $(out) && " +
+        fastboot_sign_test_image,
+}
+
+genrule {
+    name: "fastboot_test_vendor_boot_v4_without_frag",
+    defaults: ["fastboot_test_vendor_boot_gen_defaults"],
+    out: ["vendor_boot_v4_without_frag.img"],
+    srcs: [
+        ":fastboot_test_dtb",
+        ":fastboot_test_vendor_ramdisk_none",
+        ":fastboot_test_bootconfig",
+    ],
+    cmd: "$(location mkbootimg) --header_version 4 " +
+        "--vendor_ramdisk $(location :fastboot_test_vendor_ramdisk_none) " +
+        "--dtb $(location :fastboot_test_dtb) " +
+        "--vendor_bootconfig $(location :fastboot_test_bootconfig) " +
+        "--vendor_boot $(out) && " +
+        fastboot_sign_test_image,
+}
+
+genrule {
+    name: "fastboot_test_vendor_boot_v4_with_frag",
+    defaults: ["fastboot_test_vendor_boot_gen_defaults"],
+    out: ["vendor_boot_v4_with_frag.img"],
+    srcs: [
+        ":fastboot_test_dtb",
+        ":fastboot_test_vendor_ramdisk_none",
+        ":fastboot_test_vendor_ramdisk_platform",
+        ":fastboot_test_bootconfig",
+    ],
+    cmd: "$(location mkbootimg) --header_version 4 " +
+        "--dtb $(location :fastboot_test_dtb) " +
+        "--vendor_bootconfig $(location :fastboot_test_bootconfig) " +
+        "--ramdisk_type none --ramdisk_name none_ramdisk " +
+        "--vendor_ramdisk_fragment $(location :fastboot_test_vendor_ramdisk_none) " +
+        "--ramdisk_type platform --ramdisk_name platform_ramdisk " +
+        "--vendor_ramdisk_fragment $(location :fastboot_test_vendor_ramdisk_platform) " +
+        "--vendor_boot $(out) && " +
+        fastboot_sign_test_image,
+}
diff --git a/fastboot/testdata/fastboot_gen_rand.py b/fastboot/testdata/fastboot_gen_rand.py
new file mode 100644
index 0000000..a87467b
--- /dev/null
+++ b/fastboot/testdata/fastboot_gen_rand.py
@@ -0,0 +1,32 @@
+#!/usr/bin/env python3
+
+# Copyright (C) 2021 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.
+
+"""
+Write given number of random bytes, generated with optional seed.
+"""
+
+import random, argparse
+
+if __name__ == '__main__':
+  parser = argparse.ArgumentParser(description=__doc__)
+  parser.add_argument('--seed', help='Seed to random generator')
+  parser.add_argument('--length', type=int, required=True, help='Length of output')
+  args = parser.parse_args()
+
+  if args.seed:
+    random.seed(args.seed)
+
+  print(''.join(chr(random.randrange(0,0xff)) for _ in range(args.length)))
diff --git a/fastboot/vendor_boot_img_utils.cpp b/fastboot/vendor_boot_img_utils.cpp
new file mode 100644
index 0000000..2db20cd
--- /dev/null
+++ b/fastboot/vendor_boot_img_utils.cpp
@@ -0,0 +1,422 @@
+/*
+ * Copyright (C) 2021 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 "vendor_boot_img_utils.h"
+
+#include <string.h>
+
+#include <android-base/file.h>
+#include <android-base/result.h>
+#include <bootimg.h>
+#include <libavb/libavb.h>
+
+namespace {
+
+using android::base::Result;
+
+// Updates a given buffer by creating a new one.
+class DataUpdater {
+  public:
+    DataUpdater(const std::string& old_data) : old_data_(&old_data) {
+        old_data_ptr_ = old_data_->data();
+        new_data_.resize(old_data_->size(), '\0');
+        new_data_ptr_ = new_data_.data();
+    }
+    // Copy |num_bytes| from src to dst.
+    [[nodiscard]] Result<void> Copy(uint32_t num_bytes) {
+        if (num_bytes == 0) return {};
+        if (auto res = CheckAdvance(old_data_ptr_, old_end(), num_bytes, __FUNCTION__); !res.ok())
+            return res;
+        if (auto res = CheckAdvance(new_data_ptr_, new_end(), num_bytes, __FUNCTION__); !res.ok())
+            return res;
+        memcpy(new_data_ptr_, old_data_ptr_, num_bytes);
+        old_data_ptr_ += num_bytes;
+        new_data_ptr_ += num_bytes;
+        return {};
+    }
+    // Replace |old_num_bytes| from src with new data.
+    [[nodiscard]] Result<void> Replace(uint32_t old_num_bytes, const std::string& new_data) {
+        return Replace(old_num_bytes, new_data.data(), new_data.size());
+    }
+    [[nodiscard]] Result<void> Replace(uint32_t old_num_bytes, const void* new_data,
+                                       uint32_t new_data_size) {
+        if (auto res = CheckAdvance(old_data_ptr_, old_end(), old_num_bytes, __FUNCTION__);
+            !res.ok())
+            return res;
+        old_data_ptr_ += old_num_bytes;
+
+        if (new_data_size == 0) return {};
+        if (auto res = CheckAdvance(new_data_ptr_, new_end(), new_data_size, __FUNCTION__);
+            !res.ok())
+            return res;
+        memcpy(new_data_ptr_, new_data, new_data_size);
+        new_data_ptr_ += new_data_size;
+        return {};
+    }
+    // Skip |old_skip| from src and |new_skip| from dst, respectively.
+    [[nodiscard]] Result<void> Skip(uint32_t old_skip, uint32_t new_skip) {
+        if (auto res = CheckAdvance(old_data_ptr_, old_end(), old_skip, __FUNCTION__); !res.ok())
+            return res;
+        old_data_ptr_ += old_skip;
+        if (auto res = CheckAdvance(new_data_ptr_, new_end(), new_skip, __FUNCTION__); !res.ok())
+            return res;
+        new_data_ptr_ += new_skip;
+        return {};
+    }
+
+    [[nodiscard]] Result<void> Seek(uint32_t offset) {
+        if (offset > size()) return Errorf("Cannot seek 0x{:x}, size is 0x{:x}", offset, size());
+        old_data_ptr_ = old_begin() + offset;
+        new_data_ptr_ = new_begin() + offset;
+        return {};
+    }
+
+    std::string Finish() {
+        new_data_ptr_ = nullptr;
+        return std::move(new_data_);
+    }
+
+    [[nodiscard]] Result<void> CheckOffset(uint32_t old_offset, uint32_t new_offset) {
+        if (old_begin() + old_offset != old_cur())
+            return Errorf("Old offset mismatch: expected: 0x{:x}, actual: 0x{:x}", old_offset,
+                          old_cur() - old_begin());
+        if (new_begin() + new_offset != new_cur())
+            return Errorf("New offset mismatch: expected: 0x{:x}, actual: 0x{:x}", new_offset,
+                          new_cur() - new_begin());
+        return {};
+    }
+
+    uint64_t size() const { return old_data_->size(); }
+    const char* old_begin() const { return old_data_->data(); }
+    const char* old_cur() { return old_data_ptr_; }
+    const char* old_end() const { return old_data_->data() + old_data_->size(); }
+    char* new_begin() { return new_data_.data(); }
+    char* new_cur() { return new_data_ptr_; }
+    char* new_end() { return new_data_.data() + new_data_.size(); }
+
+  private:
+    // Check if it is okay to advance |num_bytes| from |current|.
+    [[nodiscard]] Result<void> CheckAdvance(const char* current, const char* end,
+                                            uint32_t num_bytes, const char* op) {
+        auto new_end = current + num_bytes;
+        if (new_end < current /* add overflow */)
+            return Errorf("{}: Addition overflow: 0x{} + 0x{:x} < 0x{}", op, fmt::ptr(current),
+                          num_bytes, fmt::ptr(current));
+        if (new_end > end)
+            return Errorf("{}: Boundary overflow: 0x{} + 0x{:x} > 0x{}", op, fmt::ptr(current),
+                          num_bytes, fmt::ptr(end));
+        return {};
+    }
+    const std::string* old_data_;
+    std::string new_data_;
+    const char* old_data_ptr_;
+    char* new_data_ptr_;
+};
+
+// Get the size of vendor boot header.
+[[nodiscard]] Result<uint32_t> get_vendor_boot_header_size(const vendor_boot_img_hdr_v3* hdr) {
+    if (hdr->header_version == 3) return sizeof(vendor_boot_img_hdr_v3);
+    if (hdr->header_version == 4) return sizeof(vendor_boot_img_hdr_v4);
+    return Errorf("Unrecognized vendor boot header version {}", hdr->header_version);
+}
+
+// Check that content contains a valid vendor boot image header with a version at least |version|.
+[[nodiscard]] Result<void> check_vendor_boot_hdr(const std::string& content, uint32_t version) {
+    // get_vendor_boot_header_size reads header_version, so make sure reading it does not
+    // go out of bounds by ensuring that the content has at least the size of V3 header.
+    if (content.size() < sizeof(vendor_boot_img_hdr_v3)) {
+        return Errorf("Size of vendor boot is 0x{:x}, less than size of V3 header: 0x{:x}",
+                      content.size(), sizeof(vendor_boot_img_hdr_v3));
+    }
+    // Now read hdr->header_version and assert the size.
+    auto hdr = reinterpret_cast<const vendor_boot_img_hdr_v3*>(content.data());
+    auto expect_header_size = get_vendor_boot_header_size(hdr);
+    if (!expect_header_size.ok()) return expect_header_size.error();
+    if (content.size() < *expect_header_size) {
+        return Errorf("Size of vendor boot is 0x{:x}, less than size of V{} header: 0x{:x}",
+                      content.size(), version, *expect_header_size);
+    }
+    if (memcmp(hdr->magic, VENDOR_BOOT_MAGIC, VENDOR_BOOT_MAGIC_SIZE) != 0) {
+        return Errorf("Vendor boot image magic mismatch");
+    }
+    if (hdr->header_version < version) {
+        return Errorf("Require vendor boot header V{} but is V{}", version, hdr->header_version);
+    }
+    return {};
+}
+
+// Wrapper of ReadFdToString. Seek to the beginning and read the whole file to string.
+[[nodiscard]] Result<std::string> load_file(android::base::borrowed_fd fd, uint64_t expected_size,
+                                            const char* what) {
+    if (lseek(fd.get(), 0, SEEK_SET) != 0) {
+        return ErrnoErrorf("Can't seek to the beginning of {} image", what);
+    }
+    std::string content;
+    if (!android::base::ReadFdToString(fd, &content)) {
+        return ErrnoErrorf("Cannot read {} to string", what);
+    }
+    if (content.size() != expected_size) {
+        return Errorf("Size of {} does not match, expected 0x{:x}, read 0x{:x}", what,
+                      expected_size, content.size());
+    }
+    return content;
+}
+
+// Wrapper of WriteStringToFd. Seek to the beginning and write the whole file to string.
+[[nodiscard]] Result<void> store_file(android::base::borrowed_fd fd, const std::string& data,
+                                      const char* what) {
+    if (lseek(fd.get(), 0, SEEK_SET) != 0) {
+        return ErrnoErrorf("Cannot seek to beginning of {} before writing", what);
+    }
+    if (!android::base::WriteStringToFd(data, fd)) {
+        return ErrnoErrorf("Cannot write new content to {}", what);
+    }
+    if (TEMP_FAILURE_RETRY(ftruncate64(fd.get(), data.size())) == -1) {
+        return ErrnoErrorf("Truncating new vendor boot image to 0x{:x} fails", data.size());
+    }
+    return {};
+}
+
+// Copy AVB footer if it exists in the old buffer.
+[[nodiscard]] Result<void> copy_avb_footer(DataUpdater* updater) {
+    if (updater->size() < AVB_FOOTER_SIZE) return {};
+    if (auto res = updater->Seek(updater->size() - AVB_FOOTER_SIZE); !res.ok()) return res;
+    if (memcmp(updater->old_cur(), AVB_FOOTER_MAGIC, AVB_FOOTER_MAGIC_LEN) != 0) return {};
+    return updater->Copy(AVB_FOOTER_SIZE);
+}
+
+// round |value| up to a multiple of |page_size|.
+inline uint32_t round_up(uint32_t value, uint32_t page_size) {
+    return (value + page_size - 1) / page_size * page_size;
+}
+
+// Replace the vendor ramdisk as a whole.
+[[nodiscard]] Result<std::string> replace_default_vendor_ramdisk(const std::string& vendor_boot,
+                                                                 const std::string& new_ramdisk) {
+    if (auto res = check_vendor_boot_hdr(vendor_boot, 3); !res.ok()) return res.error();
+    auto hdr = reinterpret_cast<const vendor_boot_img_hdr_v3*>(vendor_boot.data());
+    auto hdr_size = get_vendor_boot_header_size(hdr);
+    if (!hdr_size.ok()) return hdr_size.error();
+    // Refer to bootimg.h for details. Numbers are in bytes.
+    const uint32_t o = round_up(*hdr_size, hdr->page_size);
+    const uint32_t p = round_up(hdr->vendor_ramdisk_size, hdr->page_size);
+    const uint32_t q = round_up(hdr->dtb_size, hdr->page_size);
+
+    DataUpdater updater(vendor_boot);
+
+    // Copy header (O bytes), then update fields in header.
+    if (auto res = updater.Copy(o); !res.ok()) return res.error();
+    auto new_hdr = reinterpret_cast<vendor_boot_img_hdr_v3*>(updater.new_begin());
+    new_hdr->vendor_ramdisk_size = new_ramdisk.size();
+    // Because it is unknown how the new ramdisk is fragmented, the whole table is replaced
+    // with a single entry representing the full ramdisk.
+    if (new_hdr->header_version >= 4) {
+        auto new_hdr_v4 = static_cast<vendor_boot_img_hdr_v4*>(new_hdr);
+        new_hdr_v4->vendor_ramdisk_table_entry_size = sizeof(vendor_ramdisk_table_entry_v4);
+        new_hdr_v4->vendor_ramdisk_table_entry_num = 1;
+        new_hdr_v4->vendor_ramdisk_table_size = new_hdr_v4->vendor_ramdisk_table_entry_num *
+                                                new_hdr_v4->vendor_ramdisk_table_entry_size;
+    }
+
+    // Copy the new ramdisk.
+    if (auto res = updater.Replace(hdr->vendor_ramdisk_size, new_ramdisk); !res.ok())
+        return res.error();
+    const uint32_t new_p = round_up(new_hdr->vendor_ramdisk_size, new_hdr->page_size);
+    if (auto res = updater.Skip(p - hdr->vendor_ramdisk_size, new_p - new_hdr->vendor_ramdisk_size);
+        !res.ok())
+        return res.error();
+    if (auto res = updater.CheckOffset(o + p, o + new_p); !res.ok()) return res.error();
+
+    // Copy DTB (Q bytes).
+    if (auto res = updater.Copy(q); !res.ok()) return res.error();
+
+    if (new_hdr->header_version >= 4) {
+        auto hdr_v4 = static_cast<const vendor_boot_img_hdr_v4*>(hdr);
+        const uint32_t r = round_up(hdr_v4->vendor_ramdisk_table_size, hdr_v4->page_size);
+        const uint32_t s = round_up(hdr_v4->bootconfig_size, hdr_v4->page_size);
+
+        auto new_entry = reinterpret_cast<vendor_ramdisk_table_entry_v4*>(updater.new_cur());
+        auto new_hdr_v4 = static_cast<const vendor_boot_img_hdr_v4*>(new_hdr);
+        auto new_r = round_up(new_hdr_v4->vendor_ramdisk_table_size, new_hdr->page_size);
+        if (auto res = updater.Skip(r, new_r); !res.ok()) return res.error();
+        if (auto res = updater.CheckOffset(o + p + q + r, o + new_p + q + new_r); !res.ok())
+            return res.error();
+
+        // Replace table with single entry representing the full ramdisk.
+        new_entry->ramdisk_size = new_hdr->vendor_ramdisk_size;
+        new_entry->ramdisk_offset = 0;
+        new_entry->ramdisk_type = VENDOR_RAMDISK_TYPE_NONE;
+        memset(new_entry->ramdisk_name, '\0', VENDOR_RAMDISK_NAME_SIZE);
+        memset(new_entry->board_id, '\0', VENDOR_RAMDISK_TABLE_ENTRY_BOARD_ID_SIZE);
+
+        // Copy bootconfig (S bytes).
+        if (auto res = updater.Copy(s); !res.ok()) return res.error();
+    }
+
+    if (auto res = copy_avb_footer(&updater); !res.ok()) return res.error();
+    return updater.Finish();
+}
+
+// Find a ramdisk fragment with a unique name. Abort if none or multiple fragments are found.
+[[nodiscard]] Result<const vendor_ramdisk_table_entry_v4*> find_unique_ramdisk(
+        const std::string& ramdisk_name, const vendor_ramdisk_table_entry_v4* table,
+        uint32_t size) {
+    const vendor_ramdisk_table_entry_v4* ret = nullptr;
+    uint32_t idx = 0;
+    const vendor_ramdisk_table_entry_v4* entry = table;
+    for (; idx < size; idx++, entry++) {
+        auto entry_name_c_str = reinterpret_cast<const char*>(entry->ramdisk_name);
+        auto entry_name_len = strnlen(entry_name_c_str, VENDOR_RAMDISK_NAME_SIZE);
+        std::string_view entry_name(entry_name_c_str, entry_name_len);
+        if (entry_name == ramdisk_name) {
+            if (ret != nullptr) {
+                return Errorf("Multiple vendor ramdisk '{}' found, name should be unique",
+                              ramdisk_name.c_str());
+            }
+            ret = entry;
+        }
+    }
+    if (ret == nullptr) {
+        return Errorf("Vendor ramdisk '{}' not found", ramdisk_name.c_str());
+    }
+    return ret;
+}
+
+// Find the vendor ramdisk fragment with |ramdisk_name| within the content of |vendor_boot|, and
+// replace it with the content of |new_ramdisk|.
+[[nodiscard]] Result<std::string> replace_vendor_ramdisk_fragment(const std::string& ramdisk_name,
+                                                                  const std::string& vendor_boot,
+                                                                  const std::string& new_ramdisk) {
+    if (auto res = check_vendor_boot_hdr(vendor_boot, 4); !res.ok()) return res.error();
+    auto hdr = reinterpret_cast<const vendor_boot_img_hdr_v4*>(vendor_boot.data());
+    auto hdr_size = get_vendor_boot_header_size(hdr);
+    if (!hdr_size.ok()) return hdr_size.error();
+    // Refer to bootimg.h for details. Numbers are in bytes.
+    const uint32_t o = round_up(*hdr_size, hdr->page_size);
+    const uint32_t p = round_up(hdr->vendor_ramdisk_size, hdr->page_size);
+    const uint32_t q = round_up(hdr->dtb_size, hdr->page_size);
+    const uint32_t r = round_up(hdr->vendor_ramdisk_table_size, hdr->page_size);
+    const uint32_t s = round_up(hdr->bootconfig_size, hdr->page_size);
+
+    if (hdr->vendor_ramdisk_table_entry_num == std::numeric_limits<uint32_t>::max()) {
+        return Errorf("Too many vendor ramdisk entries in table, overflow");
+    }
+
+    // Find entry with name |ramdisk_name|.
+    auto old_table_start =
+            reinterpret_cast<const vendor_ramdisk_table_entry_v4*>(vendor_boot.data() + o + p + q);
+    auto find_res =
+            find_unique_ramdisk(ramdisk_name, old_table_start, hdr->vendor_ramdisk_table_entry_num);
+    if (!find_res.ok()) return find_res.error();
+    const vendor_ramdisk_table_entry_v4* replace_entry = *find_res;
+    uint32_t replace_idx = replace_entry - old_table_start;
+
+    // Now reconstruct.
+    DataUpdater updater(vendor_boot);
+
+    // Copy header (O bytes), then update fields in header.
+    if (auto res = updater.Copy(o); !res.ok()) return res.error();
+    auto new_hdr = reinterpret_cast<vendor_boot_img_hdr_v4*>(updater.new_begin());
+
+    // Copy ramdisk fragments, replace for the matching index.
+    {
+        auto old_ramdisk_entry = reinterpret_cast<const vendor_ramdisk_table_entry_v4*>(
+                vendor_boot.data() + o + p + q);
+        uint32_t new_total_ramdisk_size = 0;
+        for (uint32_t new_ramdisk_idx = 0; new_ramdisk_idx < hdr->vendor_ramdisk_table_entry_num;
+             new_ramdisk_idx++, old_ramdisk_entry++) {
+            if (new_ramdisk_idx == replace_idx) {
+                if (auto res = updater.Replace(replace_entry->ramdisk_size, new_ramdisk); !res.ok())
+                    return res.error();
+                new_total_ramdisk_size += new_ramdisk.size();
+            } else {
+                if (auto res = updater.Copy(old_ramdisk_entry->ramdisk_size); !res.ok())
+                    return res.error();
+                new_total_ramdisk_size += old_ramdisk_entry->ramdisk_size;
+            }
+        }
+        new_hdr->vendor_ramdisk_size = new_total_ramdisk_size;
+    }
+
+    // Pad ramdisk to page boundary.
+    const uint32_t new_p = round_up(new_hdr->vendor_ramdisk_size, new_hdr->page_size);
+    if (auto res = updater.Skip(p - hdr->vendor_ramdisk_size, new_p - new_hdr->vendor_ramdisk_size);
+        !res.ok())
+        return res.error();
+    if (auto res = updater.CheckOffset(o + p, o + new_p); !res.ok()) return res.error();
+
+    // Copy DTB (Q bytes).
+    if (auto res = updater.Copy(q); !res.ok()) return res.error();
+
+    // Copy table, but with corresponding entries modified, including:
+    // - ramdisk_size of the entry replaced
+    // - ramdisk_offset of subsequent entries.
+    for (uint32_t new_total_ramdisk_size = 0, new_entry_idx = 0;
+         new_entry_idx < hdr->vendor_ramdisk_table_entry_num; new_entry_idx++) {
+        auto new_entry = reinterpret_cast<vendor_ramdisk_table_entry_v4*>(updater.new_cur());
+        if (auto res = updater.Copy(hdr->vendor_ramdisk_table_entry_size); !res.ok())
+            return res.error();
+        new_entry->ramdisk_offset = new_total_ramdisk_size;
+
+        if (new_entry_idx == replace_idx) {
+            new_entry->ramdisk_size = new_ramdisk.size();
+        }
+        new_total_ramdisk_size += new_entry->ramdisk_size;
+    }
+
+    // Copy padding of R pages; this is okay because table size is not changed.
+    if (auto res = updater.Copy(r - hdr->vendor_ramdisk_table_entry_num *
+                                            hdr->vendor_ramdisk_table_entry_size);
+        !res.ok())
+        return res.error();
+    if (auto res = updater.CheckOffset(o + p + q + r, o + new_p + q + r); !res.ok())
+        return res.error();
+
+    // Copy bootconfig (S bytes).
+    if (auto res = updater.Copy(s); !res.ok()) return res.error();
+
+    if (auto res = copy_avb_footer(&updater); !res.ok()) return res.error();
+    return updater.Finish();
+}
+
+}  // namespace
+
+[[nodiscard]] Result<void> replace_vendor_ramdisk(android::base::borrowed_fd vendor_boot_fd,
+                                                  uint64_t vendor_boot_size,
+                                                  const std::string& ramdisk_name,
+                                                  android::base::borrowed_fd new_ramdisk_fd,
+                                                  uint64_t new_ramdisk_size) {
+    if (new_ramdisk_size > std::numeric_limits<uint32_t>::max()) {
+        return Errorf("New vendor ramdisk is too big");
+    }
+
+    auto vendor_boot = load_file(vendor_boot_fd, vendor_boot_size, "vendor boot");
+    if (!vendor_boot.ok()) return vendor_boot.error();
+    auto new_ramdisk = load_file(new_ramdisk_fd, new_ramdisk_size, "new vendor ramdisk");
+    if (!new_ramdisk.ok()) return new_ramdisk.error();
+
+    Result<std::string> new_vendor_boot;
+    if (ramdisk_name == "default") {
+        new_vendor_boot = replace_default_vendor_ramdisk(*vendor_boot, *new_ramdisk);
+    } else {
+        new_vendor_boot = replace_vendor_ramdisk_fragment(ramdisk_name, *vendor_boot, *new_ramdisk);
+    }
+    if (!new_vendor_boot.ok()) return new_vendor_boot.error();
+    if (auto res = store_file(vendor_boot_fd, *new_vendor_boot, "new vendor boot image"); !res.ok())
+        return res.error();
+
+    return {};
+}
diff --git a/fastboot/vendor_boot_img_utils.h b/fastboot/vendor_boot_img_utils.h
new file mode 100644
index 0000000..0b702bc
--- /dev/null
+++ b/fastboot/vendor_boot_img_utils.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2021 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 <inttypes.h>
+
+#include <string>
+
+#include <android-base/result.h>
+#include <android-base/unique_fd.h>
+
+// Replace the vendor ramdisk named |ramdisk_name| within the vendor boot image,
+// specified by |vendor_boot_fd|, with the ramdisk specified by |new_ramdisk_fd|. Checks
+// that the size of the files are |vendor_boot_size| and |new_ramdisk_size|, respectively.
+// If |ramdisk_name| is "default", replace the vendor ramdisk as a whole. Otherwise, replace
+// a vendor ramdisk fragment with the given unique name.
+[[nodiscard]] android::base::Result<void> replace_vendor_ramdisk(
+        android::base::borrowed_fd vendor_boot_fd, uint64_t vendor_boot_size,
+        const std::string& ramdisk_name, android::base::borrowed_fd new_ramdisk_fd,
+        uint64_t new_ramdisk_size);
diff --git a/fastboot/vendor_boot_img_utils_test.cpp b/fastboot/vendor_boot_img_utils_test.cpp
new file mode 100644
index 0000000..1563b89
--- /dev/null
+++ b/fastboot/vendor_boot_img_utils_test.cpp
@@ -0,0 +1,429 @@
+/*
+ * Copyright (C) 2021 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 <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <filesystem>
+#include <optional>
+#include <string_view>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/result.h>
+#include <android-base/strings.h>
+#include <bootimg.h>
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <libavb/libavb.h>
+
+#include "vendor_boot_img_utils.h"
+
+using android::base::borrowed_fd;
+using android::base::ErrnoError;
+using android::base::GetExecutableDirectory;
+using android::base::ReadFdToString;
+using android::base::Result;
+using testing::AllOf;
+using testing::Each;
+using testing::Eq;
+using testing::HasSubstr;
+using testing::Not;
+using testing::Property;
+using std::string_literals::operator""s;
+
+// Expect that the Result<T> returned by |expr| is successful, and value matches |result_matcher|.
+#define EXPECT_RESULT(expr, result_matcher)                          \
+    EXPECT_THAT(expr, AllOf(Property(&decltype(expr)::ok, Eq(true)), \
+                            Property(&decltype(expr)::value, result_matcher)))
+
+// Expect that the Result<T> returned by |expr| fails, and error message matches |error_matcher|.
+#define EXPECT_ERROR(expr, error_matcher)                                                        \
+    do {                                                                                         \
+        EXPECT_THAT(                                                                             \
+                expr,                                                                            \
+                AllOf(Property(&decltype(expr)::ok, Eq(false)),                                  \
+                      Property(&decltype(expr)::error,                                           \
+                               Property(&decltype(expr)::error_type::message, error_matcher)))); \
+    } while (0)
+
+namespace {
+
+// Wrapper of fstat.
+Result<uint64_t> FileSize(borrowed_fd fd, std::filesystem::path path) {
+    struct stat sb;
+    if (fstat(fd.get(), &sb) == -1) return ErrnoError() << "fstat(" << path << ")";
+    return sb.st_size;
+}
+
+// Seek to beginning then read the whole file.
+Result<std::string> ReadStartOfFdToString(borrowed_fd fd, std::filesystem::path path) {
+    if (lseek64(fd.get(), 0, SEEK_SET) != 0)
+        return ErrnoError() << "lseek64(" << path << ", 0, SEEK_SET)";
+    std::string content;
+    if (!android::base::ReadFdToString(fd, &content)) return ErrnoError() << "read(" << path << ")";
+    return content;
+}
+
+// Round |value| up to page boundary.
+inline uint32_t round_up(uint32_t value, uint32_t page_size) {
+    return (value + page_size - 1) / page_size * page_size;
+}
+
+// Match is successful if |arg| is a zero-padded version of |expected|.
+MATCHER_P(IsPadded, expected, (negation ? "is" : "isn't") + " zero-padded of expected value"s) {
+    if (arg.size() < expected.size()) return false;
+    if (0 != memcmp(arg.data(), expected.data(), expected.size())) return false;
+    auto remainder = std::string_view(arg).substr(expected.size());
+    for (char e : remainder)
+        if (e != '\0') return false;
+    return true;
+}
+
+// Same as Eq, but don't print the content to avoid spam.
+MATCHER_P(MemEq, expected, (negation ? "is" : "isn't") + " expected value"s) {
+    if (arg.size() != expected.size()) return false;
+    return 0 == memcmp(arg.data(), expected.data(), expected.size());
+}
+
+// Expect that |arg| and |expected| has the same AVB footer.
+MATCHER_P(HasSameAvbFooter, expected,
+          (negation ? "has" : "does not have") + "expected AVB footer"s) {
+    if (expected.size() < AVB_FOOTER_SIZE || arg.size() < AVB_FOOTER_SIZE) return false;
+    return std::string_view(expected).substr(expected.size() - AVB_FOOTER_SIZE) ==
+           std::string_view(arg).substr(arg.size() - AVB_FOOTER_SIZE);
+}
+
+// A lazy handle of a file.
+struct TestFileHandle {
+    virtual ~TestFileHandle() = default;
+    // Lazily call OpenImpl(), cache result in open_result_.
+    android::base::Result<void> Open() {
+        if (!open_result_.has_value()) open_result_ = OpenImpl();
+        return open_result_.value();
+    }
+    // The original size at the time when the file is opened. If the file has been modified,
+    // this field is NOT updated.
+    uint64_t size() {
+        CHECK(open_result_.has_value());
+        return size_;
+    }
+    // The current size of the file. If the file has been modified since opened,
+    // this is updated.
+    Result<uint64_t> fsize() {
+        CHECK(open_result_.has_value());
+        return FileSize(fd_, abs_path_);
+    }
+    borrowed_fd fd() {
+        CHECK(open_result_.has_value());
+        return fd_;
+    }
+    Result<std::string> Read() {
+        CHECK(open_result_.has_value());
+        return ReadStartOfFdToString(fd_, abs_path_);
+    }
+
+  private:
+    std::filesystem::path abs_path_;
+    uint64_t size_;
+    std::optional<android::base::Result<void>> open_result_;
+    borrowed_fd fd_{-1};
+    // Opens |rel_path_| as a readonly fd, pass it to Transform, and store result to
+    // |borrowed_fd_|.
+    android::base::Result<void> OpenImpl() {
+        android::base::unique_fd read_fd(TEMP_FAILURE_RETRY(
+                open(abs_path_.c_str(), O_RDONLY | O_CLOEXEC | O_NOFOLLOW | O_BINARY)));
+        if (!read_fd.ok()) return ErrnoError() << "open(" << abs_path_ << ")";
+        auto size = FileSize(read_fd, abs_path_);
+        if (!size.ok()) return size.error();
+        size_ = *size;
+
+        auto borrowed_fd = Transform(abs_path_, std::move(read_fd));
+        if (!borrowed_fd.ok()) return borrowed_fd.error();
+        fd_ = borrowed_fd.value();
+
+        return {};
+    }
+
+  protected:
+    // |rel_path| is the relative path under test data directory.
+    TestFileHandle(const std::filesystem::path& rel_path)
+        : abs_path_(std::move(std::filesystem::path(GetExecutableDirectory()) / rel_path)) {}
+    // Given |read_fd|, the readonly fd on the test file, return an fd that's suitable for client
+    // to use. Implementation is responsible for managing the lifetime of the returned fd.
+    virtual android::base::Result<borrowed_fd> Transform(const std::filesystem::path& abs_path,
+                                                         android::base::unique_fd read_fd) = 0;
+};
+
+// A TestFileHandle where the file is readonly.
+struct ReadOnlyTestFileHandle : TestFileHandle {
+    ReadOnlyTestFileHandle(const std::filesystem::path& rel_path) : TestFileHandle(rel_path) {}
+
+  private:
+    android::base::unique_fd owned_fd_;
+    android::base::Result<borrowed_fd> Transform(const std::filesystem::path&,
+                                                 android::base::unique_fd read_fd) override {
+        owned_fd_ = std::move(read_fd);
+        return owned_fd_;
+    }
+};
+
+// A TestFileHandle where the test file is copies, hence read-writable.
+struct ReadWriteTestFileHandle : TestFileHandle {
+    ReadWriteTestFileHandle(const std::filesystem::path& rel_path) : TestFileHandle(rel_path) {}
+
+  private:
+    std::unique_ptr<TemporaryFile> temp_file_;
+
+    android::base::Result<borrowed_fd> Transform(const std::filesystem::path& abs_path,
+                                                 android::base::unique_fd read_fd) override {
+        // Make a copy to avoid writing to test data. Test files are small, so it is okay
+        // to read the whole file.
+        auto content = ReadStartOfFdToString(read_fd, abs_path);
+        if (!content.ok()) return content.error();
+        temp_file_ = std::make_unique<TemporaryFile>();
+        if (temp_file_->fd == -1)
+            return ErrnoError() << "copy " << abs_path << ": open temp file failed";
+        if (!android::base::WriteStringToFd(*content, temp_file_->fd))
+            return ErrnoError() << "copy " << abs_path << ": write temp file failed";
+
+        return temp_file_->fd;
+    }
+};
+
+class RepackVendorBootImgTestEnv : public ::testing::Environment {
+  public:
+    virtual void SetUp() {
+        OpenTestFile("test_dtb.img", &dtb, &dtb_content);
+        OpenTestFile("test_bootconfig.img", &bootconfig, &bootconfig_content);
+        OpenTestFile("test_vendor_ramdisk_none.img", &none, &none_content);
+        OpenTestFile("test_vendor_ramdisk_platform.img", &platform, &platform_content);
+        OpenTestFile("test_vendor_ramdisk_replace.img", &replace, &replace_content);
+    }
+
+    std::unique_ptr<TestFileHandle> dtb;
+    std::string dtb_content;
+    std::unique_ptr<TestFileHandle> bootconfig;
+    std::string bootconfig_content;
+    std::unique_ptr<TestFileHandle> none;
+    std::string none_content;
+    std::unique_ptr<TestFileHandle> platform;
+    std::string platform_content;
+    std::unique_ptr<TestFileHandle> replace;
+    std::string replace_content;
+
+  private:
+    void OpenTestFile(const char* rel_path, std::unique_ptr<TestFileHandle>* handle,
+                      std::string* content) {
+        *handle = std::make_unique<ReadOnlyTestFileHandle>(rel_path);
+        ASSERT_RESULT_OK((*handle)->Open());
+        auto content_res = (*handle)->Read();
+        ASSERT_RESULT_OK(content_res);
+        *content = *content_res;
+    }
+};
+RepackVendorBootImgTestEnv* env = nullptr;
+
+struct RepackVendorBootImgTestParam {
+    std::string vendor_boot_file_name;
+    uint32_t expected_header_version;
+    friend std::ostream& operator<<(std::ostream& os, const RepackVendorBootImgTestParam& param) {
+        return os << param.vendor_boot_file_name;
+    }
+};
+
+class RepackVendorBootImgTest : public ::testing::TestWithParam<RepackVendorBootImgTestParam> {
+  public:
+    virtual void SetUp() {
+        vboot = std::make_unique<ReadWriteTestFileHandle>(GetParam().vendor_boot_file_name);
+        ASSERT_RESULT_OK(vboot->Open());
+    }
+    std::unique_ptr<TestFileHandle> vboot;
+};
+
+TEST_P(RepackVendorBootImgTest, InvalidSize) {
+    EXPECT_ERROR(replace_vendor_ramdisk(vboot->fd(), vboot->size() + 1, "default",
+                                        env->replace->fd(), env->replace->size()),
+                 HasSubstr("Size of vendor boot does not match"));
+    EXPECT_ERROR(replace_vendor_ramdisk(vboot->fd(), vboot->size(), "default", env->replace->fd(),
+                                        env->replace->size() + 1),
+                 HasSubstr("Size of new vendor ramdisk does not match"));
+}
+
+TEST_P(RepackVendorBootImgTest, ReplaceUnknown) {
+    auto res = replace_vendor_ramdisk(vboot->fd(), vboot->size(), "unknown", env->replace->fd(),
+                                      env->replace->size());
+    if (GetParam().expected_header_version == 3) {
+        EXPECT_ERROR(res, Eq("Require vendor boot header V4 but is V3"));
+    } else if (GetParam().expected_header_version == 4) {
+        EXPECT_ERROR(res, Eq("Vendor ramdisk 'unknown' not found"));
+    }
+}
+
+TEST_P(RepackVendorBootImgTest, ReplaceDefault) {
+    auto old_content = vboot->Read();
+    ASSERT_RESULT_OK(old_content);
+
+    ASSERT_RESULT_OK(replace_vendor_ramdisk(vboot->fd(), vboot->size(), "default",
+                                            env->replace->fd(), env->replace->size()));
+    EXPECT_RESULT(vboot->fsize(), vboot->size()) << "File size should not change after repack";
+
+    auto new_content_res = vboot->Read();
+    ASSERT_RESULT_OK(new_content_res);
+    std::string_view new_content(*new_content_res);
+
+    auto hdr = reinterpret_cast<const vendor_boot_img_hdr_v3*>(new_content.data());
+    ASSERT_EQ(0, memcmp(VENDOR_BOOT_MAGIC, hdr->magic, VENDOR_BOOT_MAGIC_SIZE));
+    ASSERT_EQ(GetParam().expected_header_version, hdr->header_version);
+    EXPECT_EQ(hdr->vendor_ramdisk_size, env->replace->size());
+    EXPECT_EQ(hdr->dtb_size, env->dtb->size());
+
+    auto o = round_up(sizeof(vendor_boot_img_hdr_v3), hdr->page_size);
+    auto p = round_up(hdr->vendor_ramdisk_size, hdr->page_size);
+    auto q = round_up(hdr->dtb_size, hdr->page_size);
+
+    EXPECT_THAT(new_content.substr(o, p), IsPadded(env->replace_content));
+    EXPECT_THAT(new_content.substr(o + p, q), IsPadded(env->dtb_content));
+
+    if (hdr->header_version < 4) return;
+
+    auto hdr_v4 = static_cast<const vendor_boot_img_hdr_v4*>(hdr);
+    EXPECT_EQ(hdr_v4->vendor_ramdisk_table_entry_num, 1);
+    EXPECT_EQ(hdr_v4->vendor_ramdisk_table_size, 1 * hdr_v4->vendor_ramdisk_table_entry_size);
+    EXPECT_GE(hdr_v4->vendor_ramdisk_table_entry_size, sizeof(vendor_ramdisk_table_entry_v4));
+    auto entry = reinterpret_cast<const vendor_ramdisk_table_entry_v4*>(&new_content[o + p + q]);
+    EXPECT_EQ(entry->ramdisk_offset, 0);
+    EXPECT_EQ(entry->ramdisk_size, hdr_v4->vendor_ramdisk_size);
+    EXPECT_EQ(entry->ramdisk_type, VENDOR_RAMDISK_TYPE_NONE);
+
+    EXPECT_EQ(hdr_v4->bootconfig_size, env->bootconfig->size());
+    auto r = round_up(hdr_v4->vendor_ramdisk_table_size, hdr_v4->page_size);
+    auto s = round_up(hdr_v4->bootconfig_size, hdr_v4->page_size);
+    EXPECT_THAT(new_content.substr(o + p + q + r, s), IsPadded(env->bootconfig_content));
+
+    EXPECT_THAT(new_content, HasSameAvbFooter(*old_content));
+}
+
+INSTANTIATE_TEST_SUITE_P(
+        RepackVendorBootImgTest, RepackVendorBootImgTest,
+        ::testing::Values(RepackVendorBootImgTestParam{"vendor_boot_v3.img", 3},
+                          RepackVendorBootImgTestParam{"vendor_boot_v4_with_frag.img", 4},
+                          RepackVendorBootImgTestParam{"vendor_boot_v4_without_frag.img", 4}),
+        [](const auto& info) {
+            return android::base::StringReplace(info.param.vendor_boot_file_name, ".", "_", false);
+        });
+
+std::string_view GetRamdiskName(const vendor_ramdisk_table_entry_v4* entry) {
+    auto ramdisk_name = reinterpret_cast<const char*>(entry->ramdisk_name);
+    return std::string_view(ramdisk_name, strnlen(ramdisk_name, VENDOR_RAMDISK_NAME_SIZE));
+}
+
+class RepackVendorBootImgTestV4 : public ::testing::TestWithParam<uint32_t /* ramdisk type */> {
+  public:
+    virtual void SetUp() {
+        vboot = std::make_unique<ReadWriteTestFileHandle>("vendor_boot_v4_with_frag.img");
+        ASSERT_RESULT_OK(vboot->Open());
+    }
+    std::unique_ptr<TestFileHandle> vboot;
+};
+
+TEST_P(RepackVendorBootImgTestV4, Replace) {
+    uint32_t replace_ramdisk_type = GetParam();
+    std::string replace_ramdisk_name;
+    std::string expect_new_ramdisk_content;
+    uint32_t expect_none_size = env->none->size();
+    uint32_t expect_platform_size = env->platform->size();
+    switch (replace_ramdisk_type) {
+        case VENDOR_RAMDISK_TYPE_NONE:
+            replace_ramdisk_name = "none_ramdisk";
+            expect_new_ramdisk_content = env->replace_content + env->platform_content;
+            expect_none_size = env->replace->size();
+            break;
+        case VENDOR_RAMDISK_TYPE_PLATFORM:
+            replace_ramdisk_name = "platform_ramdisk";
+            expect_new_ramdisk_content = env->none_content + env->replace_content;
+            expect_platform_size = env->replace->size();
+            break;
+        default:
+            LOG(FATAL) << "Ramdisk type " << replace_ramdisk_type
+                       << " is not supported by this test.";
+    }
+
+    auto old_content = vboot->Read();
+    ASSERT_RESULT_OK(old_content);
+
+    ASSERT_RESULT_OK(replace_vendor_ramdisk(vboot->fd(), vboot->size(), replace_ramdisk_name,
+                                            env->replace->fd(), env->replace->size()));
+    EXPECT_RESULT(vboot->fsize(), vboot->size()) << "File size should not change after repack";
+
+    auto new_content_res = vboot->Read();
+    ASSERT_RESULT_OK(new_content_res);
+    std::string_view new_content(*new_content_res);
+
+    auto hdr = reinterpret_cast<const vendor_boot_img_hdr_v4*>(new_content.data());
+    ASSERT_EQ(0, memcmp(VENDOR_BOOT_MAGIC, hdr->magic, VENDOR_BOOT_MAGIC_SIZE));
+    ASSERT_EQ(4, hdr->header_version);
+    EXPECT_EQ(hdr->vendor_ramdisk_size, expect_none_size + expect_platform_size);
+    EXPECT_EQ(hdr->dtb_size, env->dtb->size());
+    EXPECT_EQ(hdr->bootconfig_size, env->bootconfig->size());
+
+    auto o = round_up(sizeof(vendor_boot_img_hdr_v3), hdr->page_size);
+    auto p = round_up(hdr->vendor_ramdisk_size, hdr->page_size);
+    auto q = round_up(hdr->dtb_size, hdr->page_size);
+    auto r = round_up(hdr->vendor_ramdisk_table_size, hdr->page_size);
+    auto s = round_up(hdr->bootconfig_size, hdr->page_size);
+
+    EXPECT_THAT(new_content.substr(o, p), IsPadded(expect_new_ramdisk_content));
+    EXPECT_THAT(new_content.substr(o + p, q), IsPadded(env->dtb_content));
+
+    // Check changes in table.
+    EXPECT_EQ(hdr->vendor_ramdisk_table_entry_num, 2);
+    EXPECT_EQ(hdr->vendor_ramdisk_table_size, 2 * hdr->vendor_ramdisk_table_entry_size);
+    EXPECT_GE(hdr->vendor_ramdisk_table_entry_size, sizeof(vendor_ramdisk_table_entry_v4));
+    auto entry_none =
+            reinterpret_cast<const vendor_ramdisk_table_entry_v4*>(&new_content[o + p + q]);
+    EXPECT_EQ(entry_none->ramdisk_offset, 0);
+    EXPECT_EQ(entry_none->ramdisk_size, expect_none_size);
+    EXPECT_EQ(entry_none->ramdisk_type, VENDOR_RAMDISK_TYPE_NONE);
+    EXPECT_EQ(GetRamdiskName(entry_none), "none_ramdisk");
+
+    auto entry_platform = reinterpret_cast<const vendor_ramdisk_table_entry_v4*>(
+            &new_content[o + p + q + hdr->vendor_ramdisk_table_entry_size]);
+    EXPECT_EQ(entry_platform->ramdisk_offset, expect_none_size);
+    EXPECT_EQ(entry_platform->ramdisk_size, expect_platform_size);
+    EXPECT_EQ(entry_platform->ramdisk_type, VENDOR_RAMDISK_TYPE_PLATFORM);
+    EXPECT_EQ(GetRamdiskName(entry_platform), "platform_ramdisk");
+
+    EXPECT_THAT(new_content.substr(o + p + q + r, s), IsPadded(env->bootconfig_content));
+
+    EXPECT_THAT(new_content, HasSameAvbFooter(*old_content));
+}
+INSTANTIATE_TEST_SUITE_P(RepackVendorBootImgTest, RepackVendorBootImgTestV4,
+                         ::testing::Values(VENDOR_RAMDISK_TYPE_NONE, VENDOR_RAMDISK_TYPE_PLATFORM),
+                         [](const auto& info) {
+                             return info.param == VENDOR_RAMDISK_TYPE_NONE ? "none" : "platform";
+                         });
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+    ::testing::InitGoogleTest(&argc, argv);
+    env = static_cast<RepackVendorBootImgTestEnv*>(
+            testing::AddGlobalTestEnvironment(new RepackVendorBootImgTestEnv));
+    return RUN_ALL_TESTS();
+}
diff --git a/fs_mgr/libstorage_literals/Android.bp b/fs_mgr/libstorage_literals/Android.bp
index 635ca49..5b07168 100644
--- a/fs_mgr/libstorage_literals/Android.bp
+++ b/fs_mgr/libstorage_literals/Android.bp
@@ -8,4 +8,9 @@
     host_supported: true,
     recovery_available: true,
     export_include_dirs: ["."],
+    target: {
+        windows: {
+            enabled: true,
+        },
+    },
 }
diff --git a/init/first_stage_init.cpp b/init/first_stage_init.cpp
index b2ab550..5cde167 100644
--- a/init/first_stage_init.cpp
+++ b/init/first_stage_init.cpp
@@ -337,12 +337,21 @@
         SwitchRoot("/first_stage_ramdisk");
     }
 
+    std::string force_debuggable("/force_debuggable");
+    std::string adb_debug_prop("/adb_debug.prop");
+    std::string userdebug_sepolicy("/userdebug_plat_sepolicy.cil");
+    if (IsRecoveryMode()) {
+        // Update these file paths since we didn't switch root
+        force_debuggable.insert(0, "/first_stage_ramdisk");
+        adb_debug_prop.insert(0, "/first_stage_ramdisk");
+        userdebug_sepolicy.insert(0, "/first_stage_ramdisk");
+    }
     // If this file is present, the second-stage init will use a userdebug sepolicy
     // and load adb_debug.prop to allow adb root, if the device is unlocked.
-    if (access("/force_debuggable", F_OK) == 0) {
+    if (access(force_debuggable.c_str(), F_OK) == 0) {
         std::error_code ec;  // to invoke the overloaded copy_file() that won't throw.
-        if (!fs::copy_file("/adb_debug.prop", kDebugRamdiskProp, ec) ||
-            !fs::copy_file("/userdebug_plat_sepolicy.cil", kDebugRamdiskSEPolicy, ec)) {
+        if (!fs::copy_file(adb_debug_prop, kDebugRamdiskProp, ec) ||
+            !fs::copy_file(userdebug_sepolicy, kDebugRamdiskSEPolicy, ec)) {
             LOG(ERROR) << "Failed to setup debug ramdisk";
         } else {
             // setenv for second-stage init to read above kDebugRamdisk* files.
diff --git a/libkeyutils/Android.bp b/libkeyutils/Android.bp
index 9848cd8..86f68fb 100644
--- a/libkeyutils/Android.bp
+++ b/libkeyutils/Android.bp
@@ -2,25 +2,10 @@
     default_applicable_licenses: ["system_core_libkeyutils_license"],
 }
 
-// Added automatically by a large-scale-change that took the approach of
-// 'apply every license found to every target'. While this makes sure we respect
-// every license restriction, it may not be entirely correct.
-//
-// e.g. GPL in an MIT project might only apply to the contrib/ directory.
-//
-// Please consider splitting the single license below into multiple licenses,
-// taking care not to lose any license_kind information, and overriding the
-// default license using the 'licenses: [...]' property on targets as needed.
-//
-// For unused files, consider creating a 'fileGroup' with "//visibility:private"
-// to attach the license to, and including a comment whether the files may be
-// used in the current project.
-// See: http://go/android-license-faq
 license {
     name: "system_core_libkeyutils_license",
     visibility: [":__subpackages__"],
     license_kinds: [
-        "SPDX-license-identifier-Apache-2.0",
         "SPDX-license-identifier-BSD",
     ],
     // large-scale-change unable to identify any license_text files
diff --git a/libstats/OWNERS b/libstats/OWNERS
index 7855774..d391679 100644
--- a/libstats/OWNERS
+++ b/libstats/OWNERS
@@ -1,6 +1,7 @@
-joeo@google.com
+jeffreyhuang@google.com
+jtnguyen@google.com
 muhammadq@google.com
-ruchirr@google.com
+sharaienko@google.com
 singhtejinder@google.com
 tsaichristine@google.com
 yaochen@google.com
diff --git a/libstats/pull_lazy/Android.bp b/libstats/pull_lazy/Android.bp
new file mode 100644
index 0000000..65dce26
--- /dev/null
+++ b/libstats/pull_lazy/Android.bp
@@ -0,0 +1,48 @@
+// Lazy loading version of libstatspull that can be used by code
+// that is running before the statsd APEX is mounted and
+// libstatspull.so is available.
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_library_static {
+    name: "libstatspull_lazy",
+    header_libs: [
+        "libstatspull_headers",
+        "libstatssocket_headers",
+    ],
+    export_header_lib_headers: [
+        "libstatspull_headers",
+    ],
+    apex_available: ["//apex_available:platform"],
+    srcs: ["libstatspull_lazy.cpp"],
+}
+
+cc_test {
+    name: "libstatspull_lazy_test",
+    srcs: [
+        "tests/libstatspull_lazy_test.cpp",
+    ],
+    static_libs: [
+        "libstatspull_lazy",
+        "libstatssocket_lazy",
+    ],
+    shared_libs: ["liblog"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    test_suites: ["device-tests", "mts-statsd"],
+    test_config: "libstatspull_lazy_test.xml",
+    // TODO(b/153588990): Remove when the build system properly separates.
+    // 32bit and 64bit architectures.
+    compile_multilib: "both",
+    multilib: {
+        lib64: {
+            suffix: "64",
+        },
+        lib32: {
+            suffix: "32",
+        },
+    },
+}
diff --git a/libstats/pull_lazy/TEST_MAPPING b/libstats/pull_lazy/TEST_MAPPING
new file mode 100644
index 0000000..89b8c2a
--- /dev/null
+++ b/libstats/pull_lazy/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit" : [
+    {
+      "name" : "libstatspull_lazy_test"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/libstats/pull_lazy/libstatspull_lazy.cpp b/libstats/pull_lazy/libstatspull_lazy.cpp
new file mode 100644
index 0000000..b11fcee
--- /dev/null
+++ b/libstats/pull_lazy/libstatspull_lazy.cpp
@@ -0,0 +1,190 @@
+/*
+ * Copyright (C) 2021 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 "libstatspull_lazy.h"
+
+#include <mutex>
+
+#include <dlfcn.h>
+#include <stdatomic.h>
+
+#include "log/log.h"
+
+#include "stats_pull_atom_callback.h"
+
+// This file provides a lazy interface to libstatspull.so to address early boot dependencies.
+// Specifically bootanimation, surfaceflinger, and lmkd run before the statsd APEX is loaded and
+// libstatspull.so is in the statsd APEX.
+
+// Method pointers to libstatspull methods are held in an array which simplifies checking
+// all pointers are initialized.
+enum MethodIndex {
+    // PullAtomMetadata APIs in stats_pull_atom_callback.h.
+    k_AStatsManager_PullAtomMetadata_obtain,
+    k_AStatsManager_PullAtomMetadata_release,
+    k_AStatsManager_PullAtomMetadata_setCoolDownMillis,
+    k_AStatsManager_PullAtomMetadata_getCoolDownMillis,
+    k_AStatsManager_PullAtomMetadata_setTimeoutMillis,
+    k_AStatsManager_PullAtomMetadata_getTimeoutMillis,
+    k_AStatsManager_PullAtomMetadata_setAdditiveFields,
+    k_AStatsManager_PullAtomMetadata_getNumAdditiveFields,
+    k_AStatsManager_PullAtomMetadata_getAdditiveFields,
+
+    // AStatsEventList APIs in stats_pull_atom_callback.h
+    k_AStatsEventList_addStatsEvent,
+
+    // PullAtomCallback APIs in stats_pull_atom_callback.h
+    k_AStatsManager_setPullAtomCallback,
+    k_AStatsManager_clearPullAtomCallback,
+
+    // Marker for count of methods
+    k_MethodCount
+};
+
+// Table of methods pointers in libstatspull APIs.
+static void* g_Methods[k_MethodCount];
+
+//
+// Libstatspull lazy loading.
+//
+
+static atomic_bool gPreventLibstatspullLoading = false;  // Allows tests to block loading.
+
+void PreventLibstatspullLazyLoadingForTests() {
+    gPreventLibstatspullLoading.store(true);
+}
+
+static void* LoadLibstatspull(int dlopen_flags) {
+    if (gPreventLibstatspullLoading.load()) {
+        return nullptr;
+    }
+    return dlopen("libstatspull.so", dlopen_flags);
+}
+
+//
+// Initialization and symbol binding.
+
+static void BindSymbol(void* handle, const char* name, enum MethodIndex index) {
+    void* symbol = dlsym(handle, name);
+    LOG_ALWAYS_FATAL_IF(symbol == nullptr, "Failed to find symbol '%s' in libstatspull.so: %s",
+                        name, dlerror());
+    g_Methods[index] = symbol;
+}
+
+static void InitializeOnce() {
+    void* handle = LoadLibstatspull(RTLD_NOW);
+    LOG_ALWAYS_FATAL_IF(handle == nullptr, "Failed to load libstatspull.so: %s", dlerror());
+
+#undef BIND_SYMBOL
+#define BIND_SYMBOL(name) BindSymbol(handle, #name, k_##name);
+    // PullAtomMetadata APIs in stats_pull_atom_callback.h.
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_obtain);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_release);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_setCoolDownMillis);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_getCoolDownMillis);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_setTimeoutMillis);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_getTimeoutMillis);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_setAdditiveFields);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_getNumAdditiveFields);
+    BIND_SYMBOL(AStatsManager_PullAtomMetadata_getAdditiveFields);
+
+    // AStatsEventList APIs in stats_pull_atom_callback.h
+    BIND_SYMBOL(AStatsEventList_addStatsEvent);
+
+    // PullAtomCallback APIs in stats_pull_atom_callback.h
+    BIND_SYMBOL(AStatsManager_setPullAtomCallback);
+    BIND_SYMBOL(AStatsManager_clearPullAtomCallback);
+
+#undef BIND_SYMBOL
+
+    // Check every symbol is bound.
+    for (int i = 0; i < k_MethodCount; ++i) {
+        LOG_ALWAYS_FATAL_IF(g_Methods[i] == nullptr,
+                            "Uninitialized method in libstatspull_lazy at index: %d", i);
+    }
+}
+
+static void EnsureInitialized() {
+    static std::once_flag initialize_flag;
+    std::call_once(initialize_flag, InitializeOnce);
+}
+
+#define INVOKE_METHOD(name, args...)                            \
+    do {                                                        \
+        EnsureInitialized();                                    \
+        void* method = g_Methods[k_##name];                     \
+        return reinterpret_cast<decltype(&name)>(method)(args); \
+    } while (0)
+
+//
+// Forwarding for methods in stats_pull_atom_callback.h.
+//
+
+AStatsManager_PullAtomMetadata* AStatsManager_PullAtomMetadata_obtain() {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_obtain);
+}
+
+void AStatsManager_PullAtomMetadata_release(AStatsManager_PullAtomMetadata* metadata) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_release, metadata);
+}
+
+void AStatsManager_PullAtomMetadata_setCoolDownMillis(AStatsManager_PullAtomMetadata* metadata,
+                                                      int64_t cool_down_millis) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_setCoolDownMillis, metadata, cool_down_millis);
+}
+
+int64_t AStatsManager_PullAtomMetadata_getCoolDownMillis(AStatsManager_PullAtomMetadata* metadata) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_getCoolDownMillis, metadata);
+}
+
+void AStatsManager_PullAtomMetadata_setTimeoutMillis(AStatsManager_PullAtomMetadata* metadata,
+                                                     int64_t timeout_millis) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_setTimeoutMillis, metadata, timeout_millis);
+}
+
+int64_t AStatsManager_PullAtomMetadata_getTimeoutMillis(AStatsManager_PullAtomMetadata* metadata) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_getTimeoutMillis, metadata);
+}
+
+void AStatsManager_PullAtomMetadata_setAdditiveFields(AStatsManager_PullAtomMetadata* metadata,
+                                                      int32_t* additive_fields,
+                                                      int32_t num_fields) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_setAdditiveFields, metadata, additive_fields,
+                  num_fields);
+}
+
+int32_t AStatsManager_PullAtomMetadata_getNumAdditiveFields(
+        AStatsManager_PullAtomMetadata* metadata) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_getNumAdditiveFields, metadata);
+}
+
+void AStatsManager_PullAtomMetadata_getAdditiveFields(AStatsManager_PullAtomMetadata* metadata,
+                                                      int32_t* fields) {
+    INVOKE_METHOD(AStatsManager_PullAtomMetadata_getAdditiveFields, metadata, fields);
+}
+
+AStatsEvent* AStatsEventList_addStatsEvent(AStatsEventList* pull_data) {
+    INVOKE_METHOD(AStatsEventList_addStatsEvent, pull_data);
+}
+
+void AStatsManager_setPullAtomCallback(int32_t atom_tag, AStatsManager_PullAtomMetadata* metadata,
+                                       AStatsManager_PullAtomCallback callback, void* cookie) {
+    INVOKE_METHOD(AStatsManager_setPullAtomCallback, atom_tag, metadata, callback, cookie);
+}
+
+void AStatsManager_clearPullAtomCallback(int32_t atom_tag) {
+    INVOKE_METHOD(AStatsManager_clearPullAtomCallback, atom_tag);
+}
diff --git a/libstats/pull_lazy/libstatspull_lazy.h b/libstats/pull_lazy/libstatspull_lazy.h
new file mode 100644
index 0000000..2edddc7
--- /dev/null
+++ b/libstats/pull_lazy/libstatspull_lazy.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2021 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
+
+extern "C" void PreventLibstatspullLazyLoadingForTests();
\ No newline at end of file
diff --git a/libstats/pull_lazy/libstatspull_lazy_test.xml b/libstats/pull_lazy/libstatspull_lazy_test.xml
new file mode 100644
index 0000000..1b619af
--- /dev/null
+++ b/libstats/pull_lazy/libstatspull_lazy_test.xml
@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2021 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.
+-->
+<configuration description="Runs libstatspull_lazy_test.">
+    <option name="test-suite-tag" value="apct" />
+    <option name="test-suite-tag" value="apct-native" />
+    <option name="test-suite-tag" value="mts" />
+
+    <target_preparer class="com.android.tradefed.targetprep.RootTargetPreparer"/>
+
+    <target_preparer class="com.android.compatibility.common.tradefed.targetprep.FilePusher">
+        <option name="cleanup" value="true" />
+        <option name="push" value="libstatspull_lazy_test->/data/local/tmp/libstatspull_lazy_test" />
+        <option name="append-bitness" value="true" />
+    </target_preparer>
+
+    <test class="com.android.tradefed.testtype.GTest" >
+        <option name="native-test-device-path" value="/data/local/tmp" />
+        <option name="module-name" value="libstatspull_lazy_test" />
+    </test>
+
+    <object type="module_controller" class="com.android.tradefed.testtype.suite.module.MainlineTestModuleController">
+        <option name="mainline-module-package-name" value="com.google.android.os.statsd" />
+    </object>
+</configuration>
\ No newline at end of file
diff --git a/libstats/pull_lazy/tests/libstatspull_lazy_test.cpp b/libstats/pull_lazy/tests/libstatspull_lazy_test.cpp
new file mode 100644
index 0000000..41f82d0
--- /dev/null
+++ b/libstats/pull_lazy/tests/libstatspull_lazy_test.cpp
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2021 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 "../libstatspull_lazy.h"
+
+#include <gtest/gtest.h>
+
+#include "stats_pull_atom_callback.h"
+//#include "stats_event.h"
+
+// The tests here are just for the case when libstatspull.so cannot be loaded by
+// libstatspull_lazy.
+class LibstatspullLazyTest : public ::testing::Test {
+  protected:
+    virtual void SetUp() {
+        ::testing::Test::SetUp();
+        PreventLibstatspullLazyLoadingForTests();
+    }
+};
+
+static const char* kLoadFailed = "Failed to load libstatspull.so";
+
+TEST_F(LibstatspullLazyTest, NoLibstatspullForPullAtomMetadata) {
+    AStatsManager_PullAtomMetadata* metadata = NULL;
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_obtain(), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_release(metadata), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_setCoolDownMillis(metadata, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_getCoolDownMillis(metadata), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_setTimeoutMillis(metadata, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_getTimeoutMillis(metadata), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_setAdditiveFields(metadata, NULL, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_getNumAdditiveFields(metadata), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_PullAtomMetadata_getAdditiveFields(metadata, NULL), kLoadFailed);
+}
+
+TEST_F(LibstatspullLazyTest, NoLibstatspullForAStatsEventList) {
+    AStatsEventList* event_list = NULL;
+    EXPECT_DEATH(AStatsEventList_addStatsEvent(event_list), kLoadFailed);
+}
+
+TEST_F(LibstatspullLazyTest, NoLibstatspullForPullAtomCallback) {
+    AStatsManager_PullAtomCallback callback = NULL;
+    EXPECT_DEATH(AStatsManager_setPullAtomCallback(0, NULL, callback, NULL), kLoadFailed);
+    EXPECT_DEATH(AStatsManager_clearPullAtomCallback(0), kLoadFailed);
+}
\ No newline at end of file
diff --git a/libstats/socket_lazy/Android.bp b/libstats/socket_lazy/Android.bp
new file mode 100644
index 0000000..b2cd7b2
--- /dev/null
+++ b/libstats/socket_lazy/Android.bp
@@ -0,0 +1,44 @@
+// Lazy loading version of libstatssocket that can be used by code
+// that is running before the statsd APEX is mounted and
+// libstatssocket.so is available.
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_library_static {
+    name: "libstatssocket_lazy",
+    header_libs: [
+        "libstatssocket_headers",
+    ],
+    export_header_lib_headers: [
+        "libstatssocket_headers",
+    ],
+    apex_available: ["//apex_available:platform"],
+    srcs: ["libstatssocket_lazy.cpp"],
+}
+
+cc_test {
+    name: "libstatssocket_lazy_test",
+    srcs: [
+        "tests/libstatssocket_lazy_test.cpp",
+    ],
+    static_libs: ["libstatssocket_lazy"],
+    shared_libs: ["liblog"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    test_suites: ["device-tests", "mts-statsd"],
+    test_config: "libstatssocket_lazy_test.xml",
+    // TODO(b/153588990): Remove when the build system properly separates.
+    // 32bit and 64bit architectures.
+    compile_multilib: "both",
+    multilib: {
+        lib64: {
+            suffix: "64",
+        },
+        lib32: {
+            suffix: "32",
+        },
+    },
+}
diff --git a/libstats/socket_lazy/TEST_MAPPING b/libstats/socket_lazy/TEST_MAPPING
new file mode 100644
index 0000000..13afc00
--- /dev/null
+++ b/libstats/socket_lazy/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit" : [
+    {
+      "name" : "libstatssocket_lazy_test"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/libstats/socket_lazy/libstatssocket_lazy.cpp b/libstats/socket_lazy/libstatssocket_lazy.cpp
new file mode 100644
index 0000000..dd93eeb
--- /dev/null
+++ b/libstats/socket_lazy/libstatssocket_lazy.cpp
@@ -0,0 +1,201 @@
+/*
+ * Copyright (C) 2021 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 "libstatssocket_lazy.h"
+
+#include <mutex>
+
+#include <dlfcn.h>
+#include <stdatomic.h>
+
+#include "log/log.h"
+
+#include "stats_event.h"
+#include "stats_socket.h"
+
+// This file provides a lazy interface to libstatssocket.so to address early boot dependencies.
+// Specifically bootanimation, surfaceflinger, and lmkd run before the statsd APEX is loaded and
+// libstatssocket.so is in the statsd APEX.
+
+// Method pointers to libstatssocket methods are held in an array which simplifies checking
+// all pointers are initialized.
+enum MethodIndex {
+    // Stats Event APIs in stats_event.h.
+    k_AStatsEvent_obtain,
+    k_AStatsEvent_build,
+    k_AStatsEvent_write,
+    k_AStatsEvent_release,
+    k_AStatsEvent_setAtomId,
+    k_AStatsEvent_writeInt32,
+    k_AStatsEvent_writeInt64,
+    k_AStatsEvent_writeFloat,
+    k_AStatsEvent_writeBool,
+    k_AStatsEvent_writeByteArray,
+    k_AStatsEvent_writeString,
+    k_AStatsEvent_writeAttributionChain,
+    k_AStatsEvent_addBoolAnnotation,
+    k_AStatsEvent_addInt32Annotation,
+
+    // Stats Socket APIs in stats_socket.h.
+    k_AStatsSocket_close,
+
+    // Marker for count of methods
+    k_MethodCount
+};
+
+// Table of methods pointers in libstatssocket APIs.
+static void* g_Methods[k_MethodCount];
+
+//
+// Libstatssocket lazy loading.
+//
+
+static atomic_bool gPreventLibstatssocketLoading = false;  // Allows tests to block loading.
+
+void PreventLibstatssocketLazyLoadingForTests() {
+    gPreventLibstatssocketLoading.store(true);
+}
+
+static void* LoadLibstatssocket(int dlopen_flags) {
+    if (gPreventLibstatssocketLoading.load()) {
+        return nullptr;
+    }
+    return dlopen("libstatssocket.so", dlopen_flags);
+}
+
+//
+// Initialization and symbol binding.
+
+static void BindSymbol(void* handle, const char* name, enum MethodIndex index) {
+    void* symbol = dlsym(handle, name);
+    LOG_ALWAYS_FATAL_IF(symbol == nullptr, "Failed to find symbol '%s' in libstatssocket.so: %s",
+                        name, dlerror());
+    g_Methods[index] = symbol;
+}
+
+static void InitializeOnce() {
+    void* handle = LoadLibstatssocket(RTLD_NOW);
+    LOG_ALWAYS_FATAL_IF(handle == nullptr, "Failed to load libstatssocket.so: %s", dlerror());
+
+#undef BIND_SYMBOL
+#define BIND_SYMBOL(name) BindSymbol(handle, #name, k_##name);
+    // Methods in stats_event.h.
+    BIND_SYMBOL(AStatsEvent_obtain);
+    BIND_SYMBOL(AStatsEvent_build);
+    BIND_SYMBOL(AStatsEvent_write);
+    BIND_SYMBOL(AStatsEvent_release);
+    BIND_SYMBOL(AStatsEvent_setAtomId);
+    BIND_SYMBOL(AStatsEvent_writeInt32);
+    BIND_SYMBOL(AStatsEvent_writeInt64);
+    BIND_SYMBOL(AStatsEvent_writeFloat);
+    BIND_SYMBOL(AStatsEvent_writeBool);
+    BIND_SYMBOL(AStatsEvent_writeByteArray);
+    BIND_SYMBOL(AStatsEvent_writeString);
+    BIND_SYMBOL(AStatsEvent_writeAttributionChain);
+    BIND_SYMBOL(AStatsEvent_addBoolAnnotation);
+    BIND_SYMBOL(AStatsEvent_addInt32Annotation);
+
+    // Methods in stats_socket.h.
+    BIND_SYMBOL(AStatsSocket_close);
+#undef BIND_SYMBOL
+
+    // Check every symbol is bound.
+    for (int i = 0; i < k_MethodCount; ++i) {
+        LOG_ALWAYS_FATAL_IF(g_Methods[i] == nullptr,
+                            "Uninitialized method in libstatssocket_lazy at index: %d", i);
+    }
+}
+
+static void EnsureInitialized() {
+    static std::once_flag initialize_flag;
+    std::call_once(initialize_flag, InitializeOnce);
+}
+
+#define INVOKE_METHOD(name, args...)                            \
+    do {                                                        \
+        EnsureInitialized();                                    \
+        void* method = g_Methods[k_##name];                     \
+        return reinterpret_cast<decltype(&name)>(method)(args); \
+    } while (0)
+
+//
+// Forwarding for methods in stats_event.h.
+//
+
+AStatsEvent* AStatsEvent_obtain() {
+    INVOKE_METHOD(AStatsEvent_obtain);
+}
+
+void AStatsEvent_build(AStatsEvent* event) {
+    INVOKE_METHOD(AStatsEvent_build, event);
+}
+
+int AStatsEvent_write(AStatsEvent* event) {
+    INVOKE_METHOD(AStatsEvent_write, event);
+}
+
+void AStatsEvent_release(AStatsEvent* event) {
+    INVOKE_METHOD(AStatsEvent_release, event);
+}
+
+void AStatsEvent_setAtomId(AStatsEvent* event, uint32_t atomId) {
+    INVOKE_METHOD(AStatsEvent_setAtomId, event, atomId);
+}
+
+void AStatsEvent_writeInt32(AStatsEvent* event, int32_t value) {
+    INVOKE_METHOD(AStatsEvent_writeInt32, event, value);
+}
+
+void AStatsEvent_writeInt64(AStatsEvent* event, int64_t value) {
+    INVOKE_METHOD(AStatsEvent_writeInt64, event, value);
+}
+
+void AStatsEvent_writeFloat(AStatsEvent* event, float value) {
+    INVOKE_METHOD(AStatsEvent_writeFloat, event, value);
+}
+
+void AStatsEvent_writeBool(AStatsEvent* event, bool value) {
+    INVOKE_METHOD(AStatsEvent_writeBool, event, value);
+}
+
+void AStatsEvent_writeByteArray(AStatsEvent* event, const uint8_t* buf, size_t numBytes) {
+    INVOKE_METHOD(AStatsEvent_writeByteArray, event, buf, numBytes);
+}
+
+void AStatsEvent_writeString(AStatsEvent* event, const char* value) {
+    INVOKE_METHOD(AStatsEvent_writeString, event, value);
+}
+
+void AStatsEvent_writeAttributionChain(AStatsEvent* event, const uint32_t* uids,
+                                       const char* const* tags, uint8_t numNodes) {
+    INVOKE_METHOD(AStatsEvent_writeAttributionChain, event, uids, tags, numNodes);
+}
+
+void AStatsEvent_addBoolAnnotation(AStatsEvent* event, uint8_t annotationId, bool value) {
+    INVOKE_METHOD(AStatsEvent_addBoolAnnotation, event, annotationId, value);
+}
+
+void AStatsEvent_addInt32Annotation(AStatsEvent* event, uint8_t annotationId, int32_t value) {
+    INVOKE_METHOD(AStatsEvent_addInt32Annotation, event, annotationId, value);
+}
+
+//
+// Forwarding for methods in stats_socket.h.
+//
+
+void AStatsSocket_close() {
+    INVOKE_METHOD(AStatsSocket_close);
+}
\ No newline at end of file
diff --git a/libstats/socket_lazy/libstatssocket_lazy.h b/libstats/socket_lazy/libstatssocket_lazy.h
new file mode 100644
index 0000000..3ff87cb
--- /dev/null
+++ b/libstats/socket_lazy/libstatssocket_lazy.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2021 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
+
+extern "C" void PreventLibstatssocketLazyLoadingForTests();
\ No newline at end of file
diff --git a/libstats/socket_lazy/libstatssocket_lazy_test.xml b/libstats/socket_lazy/libstatssocket_lazy_test.xml
new file mode 100644
index 0000000..ca6339b
--- /dev/null
+++ b/libstats/socket_lazy/libstatssocket_lazy_test.xml
@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2021 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.
+-->
+<configuration description="Runs libstatssocket_lazy_test.">
+    <option name="test-suite-tag" value="apct" />
+    <option name="test-suite-tag" value="apct-native" />
+    <option name="test-suite-tag" value="mts" />
+
+    <target_preparer class="com.android.tradefed.targetprep.RootTargetPreparer"/>
+
+    <target_preparer class="com.android.compatibility.common.tradefed.targetprep.FilePusher">
+        <option name="cleanup" value="true" />
+        <option name="push" value="libstatssocket_lazy_test->/data/local/tmp/libstatssocket_lazy_test" />
+        <option name="append-bitness" value="true" />
+    </target_preparer>
+
+    <test class="com.android.tradefed.testtype.GTest" >
+        <option name="native-test-device-path" value="/data/local/tmp" />
+        <option name="module-name" value="libstatssocket_lazy_test" />
+    </test>
+
+    <object type="module_controller" class="com.android.tradefed.testtype.suite.module.MainlineTestModuleController">
+        <option name="mainline-module-package-name" value="com.google.android.os.statsd" />
+    </object>
+</configuration>
\ No newline at end of file
diff --git a/libstats/socket_lazy/tests/libstatssocket_lazy_test.cpp b/libstats/socket_lazy/tests/libstatssocket_lazy_test.cpp
new file mode 100644
index 0000000..fe13598
--- /dev/null
+++ b/libstats/socket_lazy/tests/libstatssocket_lazy_test.cpp
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2021 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 "../libstatssocket_lazy.h"
+
+#include <gtest/gtest.h>
+
+#include "stats_event.h"
+#include "stats_socket.h"
+
+// The tests here are just for the case when libstatssocket.so cannot be loaded by
+// libstatssocket_lazy.
+class LibstatssocketLazyTest : public ::testing::Test {
+  protected:
+    virtual void SetUp() {
+        ::testing::Test::SetUp();
+        PreventLibstatssocketLazyLoadingForTests();
+    }
+};
+
+static const char* kLoadFailed = "Failed to load libstatssocket.so";
+
+TEST_F(LibstatssocketLazyTest, NoLibstatssocketForStatsEvent) {
+    AStatsEvent* event = NULL;
+    EXPECT_DEATH(AStatsEvent_obtain(), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_build(event), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_write(event), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_release(event), kLoadFailed);
+
+    EXPECT_DEATH(AStatsEvent_setAtomId(event, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_writeInt32(event, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_writeInt64(event, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_writeFloat(event, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_writeBool(event, false), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_writeByteArray(event, NULL, 0), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_writeString(event, NULL), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_writeAttributionChain(event, NULL, NULL, 0), kLoadFailed);
+
+    EXPECT_DEATH(AStatsEvent_addBoolAnnotation(event, 0, false), kLoadFailed);
+    EXPECT_DEATH(AStatsEvent_addInt32Annotation(event, 0, 0), kLoadFailed);
+}
+
+TEST_F(LibstatssocketLazyTest, NoLibstatssocketForStatsSocket) {
+    EXPECT_DEATH(AStatsSocket_close(), kLoadFailed);
+}
\ No newline at end of file
diff --git a/llkd/README.md b/llkd/README.md
index 6f92f14..9bcf806 100644
--- a/llkd/README.md
+++ b/llkd/README.md
@@ -207,7 +207,7 @@
 
 The `llkd` does not monitor the specified subset of processes for live lock stack
 signatures. Default is process names
-`init,lmkd.llkd,llkd,keystore,ueventd,apexd,logd`. Prevents the sepolicy
+`init,lmkd.llkd,llkd,keystore,keystore2,ueventd,apexd,logd`. Prevents the sepolicy
 violation associated with processes that block `ptrace` (as these can't be
 checked). **Active only on userdebug and eng builds**. For details on build
 types, refer to [Building Android](/setup/build/building#choose-a-target).
diff --git a/llkd/include/llkd.h b/llkd/include/llkd.h
index 4b20a56..0822a3e 100644
--- a/llkd/include/llkd.h
+++ b/llkd/include/llkd.h
@@ -60,7 +60,7 @@
 #define LLK_IGNORELIST_UID_PROPERTY     "ro.llk.ignorelist.uid"
 #define LLK_IGNORELIST_UID_DEFAULT      ""
 #define LLK_IGNORELIST_STACK_PROPERTY   "ro.llk.ignorelist.process.stack"
-#define LLK_IGNORELIST_STACK_DEFAULT    "init,lmkd.llkd,llkd,keystore,ueventd,apexd"
+#define LLK_IGNORELIST_STACK_DEFAULT    "init,lmkd.llkd,llkd,keystore,keystore2,ueventd,apexd"
 /* clang-format on */
 
 __END_DECLS
diff --git a/llkd/libllkd.cpp b/llkd/libllkd.cpp
index 9f3e218..c4c58ee 100644
--- a/llkd/libllkd.cpp
+++ b/llkd/libllkd.cpp
@@ -115,8 +115,8 @@
 // list of uids, and uid names, to skip, default nothing
 std::unordered_set<std::string> llkIgnorelistUid;
 #ifdef __PTRACE_ENABLED__
-// list of names to skip stack checking. "init", "lmkd", "llkd", "keystore" or
-// "logd" (if not userdebug).
+// list of names to skip stack checking. "init", "lmkd", "llkd", "keystore",
+// "keystore2", or "logd" (if not userdebug).
 std::unordered_set<std::string> llkIgnorelistStack;
 #endif
 
@@ -962,7 +962,8 @@
     //
     // This alarm is effectively the live lock detection of llkd, as
     // we understandably can not monitor ourselves otherwise.
-    ::alarm(duration_cast<seconds>(llkTimeoutMs * 2 * android::base::TimeoutMultiplier()).count());
+    ::alarm(duration_cast<seconds>(llkTimeoutMs * 2 * android::base::HwTimeoutMultiplier())
+                    .count());
 
     // kernel jiffy precision fastest acquisition
     static timespec last;
diff --git a/libkeyutils/mini_keyctl/Android.bp b/mini_keyctl/Android.bp
similarity index 100%
rename from libkeyutils/mini_keyctl/Android.bp
rename to mini_keyctl/Android.bp
diff --git a/libkeyutils/mini_keyctl/mini_keyctl.cpp b/mini_keyctl/mini_keyctl.cpp
similarity index 100%
rename from libkeyutils/mini_keyctl/mini_keyctl.cpp
rename to mini_keyctl/mini_keyctl.cpp
diff --git a/libkeyutils/mini_keyctl/mini_keyctl_utils.cpp b/mini_keyctl/mini_keyctl_utils.cpp
similarity index 100%
rename from libkeyutils/mini_keyctl/mini_keyctl_utils.cpp
rename to mini_keyctl/mini_keyctl_utils.cpp
diff --git a/libkeyutils/mini_keyctl/mini_keyctl_utils.h b/mini_keyctl/mini_keyctl_utils.h
similarity index 100%
rename from libkeyutils/mini_keyctl/mini_keyctl_utils.h
rename to mini_keyctl/mini_keyctl_utils.h
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 58e161d..11b3da7 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -1074,7 +1074,7 @@
     chown root radio /proc/cmdline
 
     # Define default initial receive window size in segments.
-    setprop net.tcp.default_init_rwnd 60
+    setprop net.tcp_def_init_rwnd 60
 
     # Start standard binderized HAL daemons
     class_start hal
diff --git a/trusty/fuzz/tipc_fuzzer.cpp b/trusty/fuzz/tipc_fuzzer.cpp
index 24b0f98..3258944 100644
--- a/trusty/fuzz/tipc_fuzzer.cpp
+++ b/trusty/fuzz/tipc_fuzzer.cpp
@@ -51,13 +51,21 @@
         exit(-1);
     }
 
+    /* Make sure lazy-loaded TAs have started and connected to coverage service. */
+    TrustyApp ta(TIPC_DEV, TRUSTY_APP_PORT);
+    auto ret = ta.Connect();
+    if (!ret.ok()) {
+        std::cerr << ret.error() << std::endl;
+        exit(-1);
+    }
+
     record = std::make_unique<CoverageRecord>(TIPC_DEV, &module_uuid, TRUSTY_APP_FILENAME);
     if (!record) {
         std::cerr << "Failed to allocate coverage record" << std::endl;
         exit(-1);
     }
 
-    auto ret = record->Open();
+    ret = record->Open();
     if (!ret.ok()) {
         std::cerr << ret.error() << std::endl;
         exit(-1);
diff --git a/trusty/utils/acvp/Android.bp b/trusty/utils/acvp/Android.bp
new file mode 100644
index 0000000..b851e39
--- /dev/null
+++ b/trusty/utils/acvp/Android.bp
@@ -0,0 +1,40 @@
+// Copyright (C) 2021 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: "trusty_acvp_modulewrapper",
+    vendor: true,
+
+    srcs: [
+        "trusty_modulewrapper.cpp",
+    ],
+    static_libs: [
+        "libacvp_modulewrapper",
+    ],
+    shared_libs: [
+        "libbase",
+        "libc",
+        "libdmabufheap",
+        "liblog",
+        "libtrusty",
+        "libssl",
+    ],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+}
diff --git a/trusty/utils/acvp/acvp_ipc.h b/trusty/utils/acvp/acvp_ipc.h
new file mode 100644
index 0000000..8b48ae3
--- /dev/null
+++ b/trusty/utils/acvp/acvp_ipc.h
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2021 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>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define ACVP_PORT "com.android.trusty.acvp"
+
+/*
+ * Maximum number of arguments
+ */
+#define ACVP_MAX_NUM_ARGUMENTS 8
+
+/*
+ * Maximum length of an algorithm name
+ */
+#define ACVP_MAX_NAME_LENGTH 30
+
+/*
+ * Maximum length of an ACVP request message
+ */
+#define ACVP_MAX_MESSAGE_LENGTH sizeof(struct acvp_req)
+
+/*
+ * Minimum length of the shared memory buffer
+ *
+ * This must be at least as long as the longest reply from the ACVP service
+ * (currently the reply from getConfig()).
+ */
+#define ACVP_MIN_SHARED_MEMORY 16384
+
+/**
+ * acvp_req - Request for the Trusty ACVP app
+ * @num_args: Number of acvp_arg structures following this struct
+ * @buffer_size: Total size of shared memory buffer
+ * @lengths: Length of each argument in the shared memory buffer
+ *
+ * @num_args copies of the acvp_arg struct follow this structure.
+ */
+struct acvp_req {
+    uint32_t num_args;
+    uint32_t buffer_size;
+    uint32_t lengths[ACVP_MAX_NUM_ARGUMENTS];
+};
+
+/**
+ * acvp_resp - Response to a ACVP request
+ *
+ * @num_spans: Number of response sections
+ * @lengths: Length of each response section
+ */
+struct acvp_resp {
+    uint32_t num_spans;
+    uint32_t lengths[ACVP_MAX_NUM_ARGUMENTS];
+};
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
diff --git a/trusty/utils/acvp/trusty_modulewrapper.cpp b/trusty/utils/acvp/trusty_modulewrapper.cpp
new file mode 100644
index 0000000..70ffb52
--- /dev/null
+++ b/trusty/utils/acvp/trusty_modulewrapper.cpp
@@ -0,0 +1,235 @@
+/*
+ * Copyright 2021, 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.
+ */
+
+#define LOG_TAG "TrustyAcvpModulewrapper"
+
+#include <BufferAllocator/BufferAllocator.h>
+#include <android-base/file.h>
+#include <android-base/result.h>
+#include <android-base/unique_fd.h>
+#include <errno.h>
+#include <log/log.h>
+#include <modulewrapper.h>
+#include <openssl/span.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <trusty/tipc.h>
+#include <unistd.h>
+#include <iostream>
+
+#include "acvp_ipc.h"
+
+constexpr const char kTrustyDeviceName[] = "/dev/trusty-ipc-dev0";
+
+using android::base::ErrnoError;
+using android::base::Error;
+using android::base::Result;
+using android::base::unique_fd;
+using android::base::WriteFully;
+
+static inline size_t AlignUpToPage(size_t size) {
+    return (size + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
+}
+
+namespace {
+
+class ModuleWrapper {
+  private:
+    static const char* kAcvpPort_;
+    static const char* kTrustyDeviceName_;
+
+  public:
+    ModuleWrapper();
+    ~ModuleWrapper();
+
+    Result<void> SendMessage(bssl::Span<const bssl::Span<const uint8_t>>);
+
+    Result<void> ForwardResponse();
+
+  private:
+    // Connection to the Trusty ACVP service
+    int tipc_fd_ = -1;
+
+    // Shared memory DMA buf
+    unique_fd dmabuf_fd_;
+
+    // Size of shared memory mapping
+    size_t shm_size_ = 0;
+
+    // Shared memory mapping
+    uint8_t* shm_buffer_ = nullptr;
+};
+
+}  // namespace
+
+const char* ModuleWrapper::kAcvpPort_ = ACVP_PORT;
+const char* ModuleWrapper::kTrustyDeviceName_ = kTrustyDeviceName;
+
+ModuleWrapper::ModuleWrapper() {
+    tipc_fd_ = tipc_connect(kTrustyDeviceName_, kAcvpPort_);
+    if (tipc_fd_ < 0) {
+        fprintf(stderr, "Failed to connect to Trusty ACVP test app: %s\n", strerror(-tipc_fd_));
+    }
+}
+
+ModuleWrapper::~ModuleWrapper() {
+    if (tipc_fd_ >= 0) {
+        tipc_close(tipc_fd_);
+    }
+
+    if (shm_buffer_) {
+        munmap(shm_buffer_, shm_size_);
+    }
+}
+
+Result<void> ModuleWrapper::SendMessage(bssl::Span<const bssl::Span<const uint8_t>> args) {
+    assert(args.size() < ACVP_MAX_NUM_ARGUMENTS);
+    assert(args[0].size() < ACVP_MAX_NAME_LENGTH);
+
+    struct acvp_req request;
+    request.num_args = args.size();
+
+    size_t total_args_size = 0;
+    for (auto arg : args) {
+        total_args_size += arg.size();
+    }
+
+    shm_size_ = ACVP_MIN_SHARED_MEMORY;
+    if (total_args_size > shm_size_) {
+        shm_size_ = AlignUpToPage(total_args_size);
+    }
+    request.buffer_size = shm_size_;
+
+    struct iovec iov = {
+            .iov_base = &request,
+            .iov_len = sizeof(struct acvp_req),
+    };
+
+    BufferAllocator alloc;
+    dmabuf_fd_.reset(alloc.Alloc(kDmabufSystemHeapName, shm_size_));
+    if (!dmabuf_fd_.ok()) {
+        return ErrnoError() << "Error creating dmabuf";
+    }
+
+    shm_buffer_ = (uint8_t*)mmap(0, shm_size_, PROT_READ | PROT_WRITE, MAP_SHARED, dmabuf_fd_, 0);
+    if (shm_buffer_ == MAP_FAILED) {
+        return ErrnoError() << "Failed to map shared memory dmabuf";
+    }
+
+    size_t cur_offset = 0;
+    for (int i = 0; i < args.size(); ++i) {
+        request.lengths[i] = args[i].size();
+        memcpy(shm_buffer_ + cur_offset, args[i].data(), args[i].size());
+        cur_offset += args[i].size();
+    }
+
+    struct trusty_shm shm = {
+            .fd = dmabuf_fd_.get(),
+            .transfer = TRUSTY_SHARE,
+    };
+
+    int rc = tipc_send(tipc_fd_, &iov, 1, &shm, 1);
+    if (rc != sizeof(struct acvp_req)) {
+        return ErrnoError() << "Failed to send request to Trusty ACVP service";
+    }
+
+    return {};
+}
+
+Result<void> ModuleWrapper::ForwardResponse() {
+    struct acvp_resp resp;
+    int bytes_read = read(tipc_fd_, &resp, sizeof(struct acvp_resp));
+    if (bytes_read < 0) {
+        return ErrnoError() << "Failed to read response from Trusty ACVP service";
+    }
+
+    if (bytes_read != sizeof(struct acvp_resp)) {
+        return Error() << "Trusty ACVP response overflowed expected size";
+    }
+
+    size_t total_args_size = 0;
+    for (size_t i = 0; i < resp.num_spans; i++) {
+        total_args_size += resp.lengths[i];
+    }
+
+    iovec iovs[2];
+    iovs[0].iov_base = &resp;
+    iovs[0].iov_len = sizeof(uint32_t) * (1 + resp.num_spans);
+
+    iovs[1].iov_base = shm_buffer_;
+    iovs[1].iov_len = total_args_size;
+
+    size_t iov_done = 0;
+    while (iov_done < 2) {
+        ssize_t r;
+        do {
+            r = writev(STDOUT_FILENO, &iovs[iov_done], 2 - iov_done);
+        } while (r == -1 && errno == EINTR);
+
+        if (r <= 0) {
+            return Error() << "Failed to write ACVP response to standard out";
+        }
+
+        size_t written = r;
+        for (size_t i = iov_done; i < 2 && written > 0; i++) {
+            iovec& iov = iovs[i];
+
+            size_t done = written;
+            if (done > iov.iov_len) {
+                done = iov.iov_len;
+            }
+
+            iov.iov_base = reinterpret_cast<uint8_t*>(iov.iov_base) + done;
+            iov.iov_len -= done;
+            written -= done;
+
+            if (iov.iov_len == 0) {
+                iov_done++;
+            }
+        }
+
+        assert(written == 0);
+    }
+
+    return {};
+}
+
+int main() {
+    for (;;) {
+        auto buffer = bssl::acvp::RequestBuffer::New();
+        auto args = bssl::acvp::ParseArgsFromFd(STDIN_FILENO, buffer.get());
+        if (args.empty()) {
+            ALOGE("Could not parse arguments\n");
+            return EXIT_FAILURE;
+        }
+
+        ModuleWrapper wrapper;
+        auto res = wrapper.SendMessage(args);
+        if (!res.ok()) {
+            std::cerr << res.error() << std::endl;
+            return EXIT_FAILURE;
+        }
+
+        res = wrapper.ForwardResponse();
+        if (!res.ok()) {
+            std::cerr << res.error() << std::endl;
+            return EXIT_FAILURE;
+        }
+    }
+
+    return EXIT_SUCCESS;
+};