diff --git a/adb/Android.mk b/adb/Android.mk
index ae03593..e195bec 100644
--- a/adb/Android.mk
+++ b/adb/Android.mk
@@ -108,7 +108,6 @@
     sysdeps_win32_test.cpp \
 
 include $(CLEAR_VARS)
-LOCAL_CLANG := true
 LOCAL_MODULE := libadbd_usb
 LOCAL_CFLAGS := $(LIBADB_CFLAGS) -DADB_HOST=0
 LOCAL_SRC_FILES := daemon/usb.cpp
@@ -122,7 +121,6 @@
 include $(BUILD_STATIC_LIBRARY)
 
 include $(CLEAR_VARS)
-LOCAL_CLANG := true
 LOCAL_MODULE := libadbd
 LOCAL_CFLAGS := $(LIBADB_CFLAGS) -DADB_HOST=0
 LOCAL_SRC_FILES := \
@@ -171,7 +169,6 @@
 include $(BUILD_HOST_STATIC_LIBRARY)
 
 include $(CLEAR_VARS)
-LOCAL_CLANG := true
 LOCAL_MODULE := adbd_test
 LOCAL_CFLAGS := -DADB_HOST=0 $(LIBADB_CFLAGS)
 LOCAL_SRC_FILES := \
@@ -330,8 +327,6 @@
 
 include $(CLEAR_VARS)
 
-LOCAL_CLANG := true
-
 LOCAL_SRC_FILES := \
     daemon/main.cpp \
     daemon/mdns.cpp \
diff --git a/base/Android.bp b/base/Android.bp
index b636dc3..1395756 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -39,7 +39,6 @@
 cc_library {
     name: "libbase",
     vendor_available: true,
-    clang: true,
     host_supported: true,
     srcs: [
         "file.cpp",
@@ -109,7 +108,6 @@
 cc_test {
     name: "libbase_test",
     host_supported: true,
-    clang: true,
     srcs: [
         "endian_test.cpp",
         "errors_test.cpp",
diff --git a/base/file.cpp b/base/file.cpp
index a2f2887..2f697a1 100644
--- a/base/file.cpp
+++ b/base/file.cpp
@@ -153,6 +153,37 @@
   return true;
 }
 
+#if defined(_WIN32)
+// Windows implementation of pread. Note that this DOES move the file descriptors read position,
+// but it does so atomically.
+static ssize_t pread(int fd, void* data, size_t byte_count, off64_t offset) {
+  DWORD bytes_read;
+  OVERLAPPED overlapped;
+  memset(&overlapped, 0, sizeof(OVERLAPPED));
+  overlapped.Offset = static_cast<DWORD>(offset);
+  overlapped.OffsetHigh = static_cast<DWORD>(offset >> 32);
+  if (!ReadFile(reinterpret_cast<HANDLE>(_get_osfhandle(fd)), data, static_cast<DWORD>(byte_count),
+                &bytes_read, &overlapped)) {
+    // In case someone tries to read errno (since this is masquerading as a POSIX call)
+    errno = EIO;
+    return -1;
+  }
+  return static_cast<ssize_t>(bytes_read);
+}
+#endif
+
+bool ReadFullyAtOffset(int fd, void* data, size_t byte_count, off64_t offset) {
+  uint8_t* p = reinterpret_cast<uint8_t*>(data);
+  while (byte_count > 0) {
+    ssize_t n = TEMP_FAILURE_RETRY(pread(fd, p, byte_count, offset));
+    if (n <= 0) return false;
+    p += n;
+    byte_count -= n;
+    offset += n;
+  }
+  return true;
+}
+
 bool WriteFully(int fd, const void* data, size_t byte_count) {
   const uint8_t* p = reinterpret_cast<const uint8_t*>(data);
   size_t remaining = byte_count;
diff --git a/base/include/android-base/file.h b/base/include/android-base/file.h
index 651f529..667d6fb 100644
--- a/base/include/android-base/file.h
+++ b/base/include/android-base/file.h
@@ -18,12 +18,18 @@
 #define ANDROID_BASE_FILE_H
 
 #include <sys/stat.h>
+#include <sys/types.h>
 #include <string>
 
 #if !defined(_WIN32) && !defined(O_BINARY)
 #define O_BINARY 0
 #endif
 
+#if defined(__APPLE__)
+/* Mac OS has always had a 64-bit off_t, so it doesn't have off64_t. */
+typedef off_t off64_t;
+#endif
+
 namespace android {
 namespace base {
 
@@ -42,6 +48,17 @@
 #endif
 
 bool ReadFully(int fd, void* data, size_t byte_count);
+
+// Reads `byte_count` bytes from the file descriptor at the specified offset.
+// Returns false if there was an IO error or EOF was reached before reading `byte_count` bytes.
+//
+// NOTE: On Linux/Mac, this function wraps pread, which provides atomic read support without
+// modifying the read pointer of the file descriptor. On Windows, however, the read pointer does
+// get modified. This means that ReadFullyAtOffset can be used concurrently with other calls to the
+// same function, but concurrently seeking or reading incrementally can lead to unexpected
+// behavior.
+bool ReadFullyAtOffset(int fd, void* data, size_t byte_count, off64_t offset);
+
 bool WriteFully(int fd, const void* data, size_t byte_count);
 
 bool RemoveFileIfExists(const std::string& path, std::string* err = nullptr);
diff --git a/bootstat/Android.bp b/bootstat/Android.bp
index bc90a6e..dd357ed 100644
--- a/bootstat/Android.bp
+++ b/bootstat/Android.bp
@@ -32,9 +32,6 @@
         "liblog",
         "libmetricslogger",
     ],
-    whole_static_libs: ["libgtest_prod"],
-    // Clang is required because of C++14
-    clang: true,
 }
 
 // bootstat static library
diff --git a/fs_mgr/Android.mk b/fs_mgr/Android.mk
index f3ca724..18ccc43 100644
--- a/fs_mgr/Android.mk
+++ b/fs_mgr/Android.mk
@@ -15,7 +15,6 @@
     libavb
 
 include $(CLEAR_VARS)
-LOCAL_CLANG := true
 LOCAL_SANITIZE := integer
 LOCAL_SRC_FILES:= fs_mgr_main.cpp
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
diff --git a/init/Android.mk b/init/Android.mk
index 670edc0..ad17f79 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -77,6 +77,7 @@
     libcutils \
     libbase \
     libc \
+    libseccomp_policy \
     libselinux \
     liblog \
     libcrypto_utils \
@@ -99,5 +100,4 @@
     ln -sf ../init $(TARGET_ROOT_OUT)/sbin/watchdogd
 
 LOCAL_SANITIZE := integer
-LOCAL_CLANG := true
 include $(BUILD_EXECUTABLE)
diff --git a/init/init.cpp b/init/init.cpp
index f937777..7fbc3b7 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -23,6 +23,7 @@
 #include <inttypes.h>
 #include <libgen.h>
 #include <paths.h>
+#include <seccomp_policy.h>
 #include <signal.h>
 #include <stdarg.h>
 #include <stdio.h>
@@ -554,6 +555,15 @@
     return 0;
 }
 
+static void global_seccomp() {
+    import_kernel_cmdline(false, [](const std::string& key, const std::string& value, bool in_qemu) {
+        if (key == "androidboot.seccomp" && value == "global" && !set_global_seccomp_filter()) {
+            LOG(ERROR) << "Failed to globally enable seccomp!";
+            panic();
+        }
+    });
+}
+
 static void selinux_init_all_handles(void)
 {
     sehandle = selinux_android_file_context_handle();
@@ -1004,6 +1014,9 @@
 
         SetInitAvbVersionInRecovery();
 
+        // Enable seccomp if global boot option was passed (otherwise it is enabled in zygote).
+        global_seccomp();
+
         // Set up SELinux, loading the SELinux policy.
         selinux_initialize(true);
 
diff --git a/init/reboot.cpp b/init/reboot.cpp
index e4779c7..17e3576 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -237,7 +237,8 @@
             std::string mount_dir(mentry->mnt_dir);
             // These are R/O partitions changed to R/W after adb remount.
             // Do not umount them as shutdown critical services may rely on them.
-            if (mount_dir != "/system" && mount_dir != "/vendor" && mount_dir != "/oem") {
+            if (mount_dir != "/" && mount_dir != "/system" && mount_dir != "/vendor" &&
+                mount_dir != "/oem") {
                 blockDevPartitions->emplace(blockDevPartitions->begin(), *mentry);
             }
         } else if (MountEntry::IsEmulatedDevice(*mentry)) {
diff --git a/libappfuse/Android.bp b/libappfuse/Android.bp
index e659f79..bfe5aaf 100644
--- a/libappfuse/Android.bp
+++ b/libappfuse/Android.bp
@@ -8,7 +8,6 @@
         "-Wall",
         "-Werror",
     ],
-    clang: true
 }
 
 cc_library_shared {
diff --git a/libcutils/Android.bp b/libcutils/Android.bp
index 245deb1..85258cd 100644
--- a/libcutils/Android.bp
+++ b/libcutils/Android.bp
@@ -156,8 +156,6 @@
         "-Wall",
         "-Wextra",
     ],
-
-    clang: true,
 }
 
 subdirs = ["tests"]
diff --git a/libion/tests/Android.bp b/libion/tests/Android.bp
index 4428848..b3fcb3b 100644
--- a/libion/tests/Android.bp
+++ b/libion/tests/Android.bp
@@ -16,7 +16,6 @@
 
 cc_test {
     name: "ion-unit-tests",
-    clang: true,
     cflags: [
         "-g",
         "-Wall",
diff --git a/libmemunreachable/Android.bp b/libmemunreachable/Android.bp
index 826a576..8b76a65 100644
--- a/libmemunreachable/Android.bp
+++ b/libmemunreachable/Android.bp
@@ -6,7 +6,6 @@
         "-Wextra",
         "-Werror",
     ],
-    clang: true,
     shared_libs: [
         "libbase",
     ],
diff --git a/libmetricslogger/Android.bp b/libmetricslogger/Android.bp
index 26a041a..c692d1f 100644
--- a/libmetricslogger/Android.bp
+++ b/libmetricslogger/Android.bp
@@ -7,7 +7,6 @@
 cc_defaults {
     name: "metricslogger_defaults",
 
-    clang: true,
     host_supported: true,
 
     export_include_dirs: ["include"],
diff --git a/libnativebridge/Android.bp b/libnativebridge/Android.bp
index 1cea4cd..8b48a87 100644
--- a/libnativebridge/Android.bp
+++ b/libnativebridge/Android.bp
@@ -12,7 +12,6 @@
     host_supported: true,
     srcs: ["native_bridge.cc"],
     shared_libs: ["liblog"],
-    clang: true,
 
     export_include_dirs=["include"],
 
diff --git a/libnativebridge/tests/Android.mk b/libnativebridge/tests/Android.mk
index 70b3fcc..c1e65ff 100644
--- a/libnativebridge/tests/Android.mk
+++ b/libnativebridge/tests/Android.mk
@@ -34,7 +34,6 @@
 
 $(foreach file,$(test_src_files), \
     $(eval include $(CLEAR_VARS)) \
-    $(eval LOCAL_CLANG := true) \
     $(eval LOCAL_SHARED_LIBRARIES := $(shared_libraries)) \
     $(eval LOCAL_SRC_FILES := $(file)) \
     $(eval LOCAL_MODULE := $(notdir $(file:%.cpp=%))) \
@@ -43,7 +42,6 @@
 
 $(foreach file,$(test_src_files), \
     $(eval include $(CLEAR_VARS)) \
-    $(eval LOCAL_CLANG := true) \
     $(eval LOCAL_SHARED_LIBRARIES := $(shared_libraries)) \
     $(eval LOCAL_SRC_FILES := $(file)) \
     $(eval LOCAL_MODULE := $(notdir $(file:%.cpp=%))) \
diff --git a/libnativeloader/Android.bp b/libnativeloader/Android.bp
index c1133fb..13f9744 100644
--- a/libnativeloader/Android.bp
+++ b/libnativeloader/Android.bp
@@ -19,7 +19,6 @@
             host_ldlibs: ["-ldl"],
         },
     },
-    clang: true,
     cflags: [
         "-Werror",
         "-Wall",
diff --git a/libpackagelistparser/Android.bp b/libpackagelistparser/Android.bp
index 70ff528..a9fec7d 100644
--- a/libpackagelistparser/Android.bp
+++ b/libpackagelistparser/Android.bp
@@ -6,7 +6,6 @@
     local_include_dirs: ["include"],
     export_include_dirs: ["include"],
 
-    clang: true,
     sanitize: {
         misc_undefined: ["integer"],
     },
diff --git a/libsync/Android.bp b/libsync/Android.bp
index 4bafb08..4f71b9f 100644
--- a/libsync/Android.bp
+++ b/libsync/Android.bp
@@ -38,5 +38,4 @@
         "-Wno-missing-field-initializers",
         "-Wno-sign-compare",
     ],
-    clang: true,
 }
diff --git a/libutils/Android.bp b/libutils/Android.bp
index fbfb7c2..109ac33 100644
--- a/libutils/Android.bp
+++ b/libutils/Android.bp
@@ -142,8 +142,6 @@
             enabled: true,
         },
     },
-
-    clang: true,
 }
 
 // Include subdirectory makefiles
diff --git a/libutils/include/utils/Mutex.h b/libutils/include/utils/Mutex.h
index d106185..af6076c 100644
--- a/libutils/include/utils/Mutex.h
+++ b/libutils/include/utils/Mutex.h
@@ -28,6 +28,53 @@
 #include <utils/Errors.h>
 #include <utils/Timers.h>
 
+// Enable thread safety attributes only with clang.
+// The attributes can be safely erased when compiling with other compilers.
+#if defined(__clang__) && (!defined(SWIG))
+#define THREAD_ANNOTATION_ATTRIBUTE__(x) __attribute__((x))
+#else
+#define THREAD_ANNOTATION_ATTRIBUTE__(x)  // no-op
+#endif
+
+#define CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(capability(x))
+
+#define SCOPED_CAPABILITY THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
+
+#define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
+
+#define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))
+
+#define ACQUIRED_BEFORE(...) THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(__VA_ARGS__))
+
+#define ACQUIRED_AFTER(...) THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(__VA_ARGS__))
+
+#define REQUIRES(...) THREAD_ANNOTATION_ATTRIBUTE__(requires_capability(__VA_ARGS__))
+
+#define REQUIRES_SHARED(...) THREAD_ANNOTATION_ATTRIBUTE__(requires_shared_capability(__VA_ARGS__))
+
+#define ACQUIRE(...) THREAD_ANNOTATION_ATTRIBUTE__(acquire_capability(__VA_ARGS__))
+
+#define ACQUIRE_SHARED(...) THREAD_ANNOTATION_ATTRIBUTE__(acquire_shared_capability(__VA_ARGS__))
+
+#define RELEASE(...) THREAD_ANNOTATION_ATTRIBUTE__(release_capability(__VA_ARGS__))
+
+#define RELEASE_SHARED(...) THREAD_ANNOTATION_ATTRIBUTE__(release_shared_capability(__VA_ARGS__))
+
+#define TRY_ACQUIRE(...) THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_capability(__VA_ARGS__))
+
+#define TRY_ACQUIRE_SHARED(...) \
+    THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_shared_capability(__VA_ARGS__))
+
+#define EXCLUDES(...) THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(__VA_ARGS__))
+
+#define ASSERT_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(assert_capability(x))
+
+#define ASSERT_SHARED_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_capability(x))
+
+#define RETURN_CAPABILITY(x) THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
+
+#define NO_THREAD_SAFETY_ANALYSIS THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
+
 // ---------------------------------------------------------------------------
 namespace android {
 // ---------------------------------------------------------------------------
@@ -44,24 +91,24 @@
  * The mutex must be unlocked by the thread that locked it.  They are not
  * recursive, i.e. the same thread can't lock it multiple times.
  */
-class Mutex {
-public:
+class CAPABILITY("mutex") Mutex {
+  public:
     enum {
         PRIVATE = 0,
         SHARED = 1
     };
 
-                Mutex();
-    explicit    Mutex(const char* name);
-    explicit    Mutex(int type, const char* name = NULL);
-                ~Mutex();
+    Mutex();
+    explicit Mutex(const char* name);
+    explicit Mutex(int type, const char* name = NULL);
+    ~Mutex();
 
     // lock or unlock the mutex
-    status_t    lock();
-    void        unlock();
+    status_t lock() ACQUIRE();
+    void unlock() RELEASE();
 
     // lock if possible; returns 0 on success, error otherwise
-    status_t    tryLock();
+    status_t tryLock() TRY_ACQUIRE(true);
 
 #if defined(__ANDROID__)
     // Lock the mutex, but don't wait longer than timeoutNs (relative time).
@@ -75,32 +122,36 @@
     // which is subject to NTP adjustments, and includes time during suspend,
     // so a timeout may occur even though no processes could run.
     // Not holding a partial wakelock may lead to a system suspend.
-    status_t    timedLock(nsecs_t timeoutNs);
+    status_t timedLock(nsecs_t timeoutNs) TRY_ACQUIRE(true);
 #endif
 
     // Manages the mutex automatically. It'll be locked when Autolock is
     // constructed and released when Autolock goes out of scope.
-    class Autolock {
-    public:
-        inline explicit Autolock(Mutex& mutex) : mLock(mutex)  { mLock.lock(); }
-        inline explicit Autolock(Mutex* mutex) : mLock(*mutex) { mLock.lock(); }
-        inline ~Autolock() { mLock.unlock(); }
-    private:
+    class SCOPED_CAPABILITY Autolock {
+      public:
+        inline explicit Autolock(Mutex& mutex) ACQUIRE(mutex) : mLock(mutex) { mLock.lock(); }
+        inline explicit Autolock(Mutex* mutex) ACQUIRE(mutex) : mLock(*mutex) { mLock.lock(); }
+        inline ~Autolock() RELEASE() { mLock.unlock(); }
+
+      private:
         Mutex& mLock;
+        // Cannot be copied or moved - declarations only
+        Autolock(const Autolock&);
+        Autolock& operator=(const Autolock&);
     };
 
-private:
+  private:
     friend class Condition;
 
     // A mutex cannot be copied
-                Mutex(const Mutex&);
-    Mutex&      operator = (const Mutex&);
+    Mutex(const Mutex&);
+    Mutex& operator=(const Mutex&);
 
 #if !defined(_WIN32)
     pthread_mutex_t mMutex;
 #else
-    void    _init();
-    void*   mState;
+    void _init();
+    void* mState;
 #endif
 };
 
diff --git a/libutils/tests/Android.bp b/libutils/tests/Android.bp
index ea606a1..7cae133 100644
--- a/libutils/tests/Android.bp
+++ b/libutils/tests/Android.bp
@@ -23,6 +23,7 @@
     srcs: [
         "BitSet_test.cpp",
         "LruCache_test.cpp",
+        "Mutex_test.cpp",
         "Singleton_test.cpp",
         "String8_test.cpp",
         "StrongPointer_test.cpp",
@@ -72,6 +73,7 @@
         "-Wall",
         "-Wextra",
         "-Werror",
+        "-Wthread-safety",
     ],
 }
 
diff --git a/libutils/tests/Mutex_test.cpp b/libutils/tests/Mutex_test.cpp
new file mode 100644
index 0000000..8a1805f
--- /dev/null
+++ b/libutils/tests/Mutex_test.cpp
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2016 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 <utils/Mutex.h>
+
+#include <gtest/gtest.h>
+
+static android::Mutex mLock;
+static int i GUARDED_BY(mLock);
+
+void modifyLockedVariable() REQUIRES(mLock) {
+    i = 1;
+}
+
+TEST(Mutex, compile) {
+    android::Mutex::Autolock _l(mLock);
+    i = 0;
+    modifyLockedVariable();
+}
\ No newline at end of file
diff --git a/libziparchive/include/ziparchive/zip_archive_stream_entry.h b/libziparchive/include/ziparchive/zip_archive_stream_entry.h
index a40b799..b4766f8 100644
--- a/libziparchive/include/ziparchive/zip_archive_stream_entry.h
+++ b/libziparchive/include/ziparchive/zip_archive_stream_entry.h
@@ -40,7 +40,8 @@
 
   ZipArchiveHandle handle_;
 
-  uint32_t crc32_;
+  off64_t offset_ = 0;
+  uint32_t crc32_ = 0u;
 };
 
 #endif  // LIBZIPARCHIVE_ZIPARCHIVESTREAMENTRY_H_
diff --git a/libziparchive/zip_archive.cc b/libziparchive/zip_archive.cc
index 17c268b..ad40d42 100644
--- a/libziparchive/zip_archive.cc
+++ b/libziparchive/zip_archive.cc
@@ -435,13 +435,20 @@
 
 static int32_t ValidateDataDescriptor(MappedZipFile& mapped_zip, ZipEntry* entry) {
   uint8_t ddBuf[sizeof(DataDescriptor) + sizeof(DataDescriptor::kOptSignature)];
-  if (!mapped_zip.ReadData(ddBuf, sizeof(ddBuf))) {
+  off64_t offset = entry->offset;
+  if (entry->method != kCompressStored) {
+    offset += entry->compressed_length;
+  } else {
+    offset += entry->uncompressed_length;
+  }
+
+  if (!mapped_zip.ReadAtOffset(ddBuf, sizeof(ddBuf), offset)) {
     return kIoError;
   }
 
   const uint32_t ddSignature = *(reinterpret_cast<const uint32_t*>(ddBuf));
-  const uint16_t offset = (ddSignature == DataDescriptor::kOptSignature) ? 4 : 0;
-  const DataDescriptor* descriptor = reinterpret_cast<const DataDescriptor*>(ddBuf + offset);
+  const uint16_t ddOffset = (ddSignature == DataDescriptor::kOptSignature) ? 4 : 0;
+  const DataDescriptor* descriptor = reinterpret_cast<const DataDescriptor*>(ddBuf + ddOffset);
 
   // Validate that the values in the data descriptor match those in the central
   // directory.
@@ -899,7 +906,9 @@
     /* read as much as we can */
     if (zstream.avail_in == 0) {
       const size_t getSize = (compressed_length > kBufSize) ? kBufSize : compressed_length;
-      if (!mapped_zip.ReadData(read_buf.data(), getSize)) {
+      off64_t offset = entry->offset + (entry->compressed_length - compressed_length);
+      // Make sure to read at offset to ensure concurrent access to the fd.
+      if (!mapped_zip.ReadAtOffset(read_buf.data(), getSize, offset)) {
         ALOGW("Zip: inflate read failed, getSize = %zu: %s", getSize, strerror(errno));
         return kIoError;
       }
@@ -962,12 +971,15 @@
   uint64_t crc = 0;
   while (count < length) {
     uint32_t remaining = length - count;
+    off64_t offset = entry->offset + count;
 
-    // Safe conversion because kBufSize is narrow enough for a 32 bit signed
-    // value.
+    // Safe conversion because kBufSize is narrow enough for a 32 bit signed value.
     const size_t block_size = (remaining > kBufSize) ? kBufSize : remaining;
-    if (!mapped_zip.ReadData(buf.data(), block_size)) {
-      ALOGW("CopyFileToFile: copy read failed, block_size = %zu: %s", block_size, strerror(errno));
+
+    // Make sure to read at offset to ensure concurrent access to the fd.
+    if (!mapped_zip.ReadAtOffset(buf.data(), block_size, offset)) {
+      ALOGW("CopyFileToFile: copy read failed, block_size = %zu, offset = %" PRId64 ": %s",
+            block_size, static_cast<int64_t>(offset), strerror(errno));
       return kIoError;
     }
 
@@ -986,12 +998,6 @@
 int32_t ExtractToWriter(ZipArchiveHandle handle, ZipEntry* entry, Writer* writer) {
   ZipArchive* archive = reinterpret_cast<ZipArchive*>(handle);
   const uint16_t method = entry->method;
-  off64_t data_offset = entry->offset;
-
-  if (!archive->mapped_zip.SeekToOffset(data_offset)) {
-    ALOGW("Zip: lseek to data at %" PRId64 " failed", static_cast<int64_t>(data_offset));
-    return kIoError;
-  }
 
   // this should default to kUnknownCompressionMethod.
   int32_t return_value = -1;
@@ -1111,52 +1117,21 @@
   }
 }
 
-bool MappedZipFile::SeekToOffset(off64_t offset) {
-  if (has_fd_) {
-    if (lseek64(fd_, offset, SEEK_SET) != offset) {
-      ALOGE("Zip: lseek to %" PRId64 " failed: %s\n", offset, strerror(errno));
-      return false;
-    }
-    return true;
-  } else {
-    if (offset < 0 || offset > static_cast<off64_t>(data_length_)) {
-      ALOGE("Zip: invalid offset: %" PRId64 ", data length: %" PRId64 "\n", offset, data_length_);
-      return false;
-    }
-
-    read_pos_ = offset;
-    return true;
-  }
-}
-
-bool MappedZipFile::ReadData(uint8_t* buffer, size_t read_amount) {
-  if (has_fd_) {
-    if (!android::base::ReadFully(fd_, buffer, read_amount)) {
-      ALOGE("Zip: read from %d failed\n", fd_);
-      return false;
-    }
-  } else {
-    memcpy(buffer, static_cast<uint8_t*>(base_ptr_) + read_pos_, read_amount);
-    read_pos_ += read_amount;
-  }
-  return true;
-}
-
 // Attempts to read |len| bytes into |buf| at offset |off|.
 bool MappedZipFile::ReadAtOffset(uint8_t* buf, size_t len, off64_t off) {
-#if !defined(_WIN32)
   if (has_fd_) {
-    if (static_cast<size_t>(TEMP_FAILURE_RETRY(pread64(fd_, buf, len, off))) != len) {
+    if (!android::base::ReadFullyAtOffset(fd_, buf, len, off)) {
       ALOGE("Zip: failed to read at offset %" PRId64 "\n", off);
       return false;
     }
-    return true;
+  } else {
+    if (off < 0 || off > static_cast<off64_t>(data_length_)) {
+      ALOGE("Zip: invalid offset: %" PRId64 ", data length: %" PRId64 "\n", off, data_length_);
+      return false;
+    }
+    memcpy(buf, static_cast<uint8_t*>(base_ptr_) + off, len);
   }
-#endif
-  if (!SeekToOffset(off)) {
-    return false;
-  }
-  return ReadData(buf, len);
+  return true;
 }
 
 void CentralDirectory::Initialize(void* map_base_ptr, off64_t cd_start_offset, size_t cd_size) {
diff --git a/libziparchive/zip_archive_private.h b/libziparchive/zip_archive_private.h
index 840f1af..174aa3f 100644
--- a/libziparchive/zip_archive_private.h
+++ b/libziparchive/zip_archive_private.h
@@ -93,14 +93,10 @@
 class MappedZipFile {
  public:
   explicit MappedZipFile(const int fd)
-      : has_fd_(true), fd_(fd), base_ptr_(nullptr), data_length_(0), read_pos_(0) {}
+      : has_fd_(true), fd_(fd), base_ptr_(nullptr), data_length_(0) {}
 
   explicit MappedZipFile(void* address, size_t length)
-      : has_fd_(false),
-        fd_(-1),
-        base_ptr_(address),
-        data_length_(static_cast<off64_t>(length)),
-        read_pos_(0) {}
+      : has_fd_(false), fd_(-1), base_ptr_(address), data_length_(static_cast<off64_t>(length)) {}
 
   bool HasFd() const { return has_fd_; }
 
@@ -110,10 +106,6 @@
 
   off64_t GetFileLength() const;
 
-  bool SeekToOffset(off64_t offset);
-
-  bool ReadData(uint8_t* buffer, size_t read_amount);
-
   bool ReadAtOffset(uint8_t* buf, size_t len, off64_t off);
 
  private:
@@ -127,8 +119,6 @@
 
   void* const base_ptr_;
   const off64_t data_length_;
-  // read_pos_ is the offset to the base_ptr_ where we read data from.
-  size_t read_pos_;
 };
 
 class CentralDirectory {
diff --git a/libziparchive/zip_archive_stream_entry.cc b/libziparchive/zip_archive_stream_entry.cc
index 50352ef..9ec89b1 100644
--- a/libziparchive/zip_archive_stream_entry.cc
+++ b/libziparchive/zip_archive_stream_entry.cc
@@ -38,13 +38,8 @@
 static constexpr size_t kBufSize = 65535;
 
 bool ZipArchiveStreamEntry::Init(const ZipEntry& entry) {
-  ZipArchive* archive = reinterpret_cast<ZipArchive*>(handle_);
-  off64_t data_offset = entry.offset;
-  if (!archive->mapped_zip.SeekToOffset(data_offset)) {
-    ALOGW("lseek to data at %" PRId64 " failed: %s", data_offset, strerror(errno));
-    return false;
-  }
   crc32_ = entry.crc32;
+  offset_ = entry.offset;
   return true;
 }
 
@@ -61,11 +56,11 @@
  protected:
   bool Init(const ZipEntry& entry) override;
 
-  uint32_t length_;
+  uint32_t length_ = 0u;
 
  private:
   std::vector<uint8_t> data_;
-  uint32_t computed_crc32_;
+  uint32_t computed_crc32_ = 0u;
 };
 
 bool ZipArchiveStreamEntryUncompressed::Init(const ZipEntry& entry) {
@@ -89,7 +84,7 @@
   size_t bytes = (length_ > data_.size()) ? data_.size() : length_;
   ZipArchive* archive = reinterpret_cast<ZipArchive*>(handle_);
   errno = 0;
-  if (!archive->mapped_zip.ReadData(data_.data(), bytes)) {
+  if (!archive->mapped_zip.ReadAtOffset(data_.data(), bytes, offset_)) {
     if (errno != 0) {
       ALOGE("Error reading from archive fd: %s", strerror(errno));
     } else {
@@ -104,6 +99,7 @@
   }
   computed_crc32_ = crc32(computed_crc32_, data_.data(), data_.size());
   length_ -= bytes;
+  offset_ += bytes;
   return &data_;
 }
 
@@ -129,9 +125,9 @@
   z_stream z_stream_;
   std::vector<uint8_t> in_;
   std::vector<uint8_t> out_;
-  uint32_t uncompressed_length_;
-  uint32_t compressed_length_;
-  uint32_t computed_crc32_;
+  uint32_t uncompressed_length_ = 0u;
+  uint32_t compressed_length_ = 0u;
+  uint32_t computed_crc32_ = 0u;
 };
 
 // This method is using libz macros with old-style-casts
@@ -210,7 +206,7 @@
       size_t bytes = (compressed_length_ > in_.size()) ? in_.size() : compressed_length_;
       ZipArchive* archive = reinterpret_cast<ZipArchive*>(handle_);
       errno = 0;
-      if (!archive->mapped_zip.ReadData(in_.data(), bytes)) {
+      if (!archive->mapped_zip.ReadAtOffset(in_.data(), bytes, offset_)) {
         if (errno != 0) {
           ALOGE("Error reading from archive fd: %s", strerror(errno));
         } else {
@@ -220,6 +216,7 @@
       }
 
       compressed_length_ -= bytes;
+      offset_ += bytes;
       z_stream_.next_in = in_.data();
       z_stream_.avail_in = bytes;
     }
diff --git a/sdcard/Android.mk b/sdcard/Android.mk
index 0c58574..5b4dc58 100644
--- a/sdcard/Android.mk
+++ b/sdcard/Android.mk
@@ -8,6 +8,5 @@
 LOCAL_SHARED_LIBRARIES := libbase libcutils libminijail libpackagelistparser
 
 LOCAL_SANITIZE := integer
-LOCAL_CLANG := true
 
 include $(BUILD_EXECUTABLE)