Convert discardable shared memory to the new shared memory API

Bug: 826213
Change-Id: Ifa1d7e3fd3625ef0161073d594f3f48aada7b7c8
Reviewed-on: https://chromium-review.googlesource.com/1019448Reviewed-by: David Reveman <reveman@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Alexandr Ilin <alexilin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553472}

base/memory/discardable_shared_memory.cc

@@ -97,8 +97,9 @@ struct SharedState {
 };
 
 // Shared state is stored at offset 0 in shared memory segments.
-SharedState* SharedStateFromSharedMemory(const SharedMemory& shared_memory) {
-  DCHECK(shared_memory.memory());
+SharedState* SharedStateFromSharedMemory(
+    const WritableSharedMemoryMapping& shared_memory) {
+  DCHECK(shared_memory.IsValid());
   return static_cast<SharedState*>(shared_memory.memory());
 }
 
@@ -107,39 +108,6 @@ size_t AlignToPageSize(size_t size) {
   return bits::Align(size, base::GetPageSize());
 }
 
-// LockPages/UnlockPages are platform-native discardable page management
-// helper functions. Both expect |offset| to be specified relative to the
-// base address at which |memory| is mapped, and that |offset| and |length|
-// are page-aligned by the caller.
-
-#if defined(OS_ANDROID)
-// Returns SUCCESS on platforms which do not support discardable pages.
-DiscardableSharedMemory::LockResult LockPages(const SharedMemory& memory,
-                                              size_t offset,
-                                              size_t length) {
-  SharedMemoryHandle handle = memory.handle();
-  if (handle.IsValid()) {
-    int pin_result = ashmem_pin_region(handle.GetHandle(), offset, length);
-    if (pin_result == ASHMEM_WAS_PURGED)
-      return DiscardableSharedMemory::PURGED;
-    if (pin_result < 0)
-      return DiscardableSharedMemory::FAILED;
-  }
-  return DiscardableSharedMemory::SUCCESS;
-}
-#endif
-
-// UnlockPages() is a no-op on platforms not supporting discardable pages.
-void UnlockPages(const SharedMemory& memory, size_t offset, size_t length) {
-#if defined(OS_ANDROID)
-  SharedMemoryHandle handle = memory.handle();
-  if (handle.IsValid()) {
-    int unpin_result = ashmem_unpin_region(handle.GetHandle(), offset, length);
-    DCHECK_EQ(0, unpin_result);
-  }
-#endif
-}
-
 }  // namespace
 
 DiscardableSharedMemory::DiscardableSharedMemory()
@@ -147,11 +115,10 @@ DiscardableSharedMemory::DiscardableSharedMemory()
 }
 
 DiscardableSharedMemory::DiscardableSharedMemory(
-    SharedMemoryHandle shared_memory_handle)
-    : shared_memory_(shared_memory_handle, false),
+    UnsafeSharedMemoryRegion shared_memory_region)
+    : shared_memory_region_(std::move(shared_memory_region)),
       mapped_size_(0),
-      locked_page_count_(0) {
-}
+      locked_page_count_(0) {}
 
 DiscardableSharedMemory::~DiscardableSharedMemory() = default;
 
@@ -161,11 +128,18 @@ bool DiscardableSharedMemory::CreateAndMap(size_t size) {
   if (!checked_size.IsValid())
     return false;
 
-  if (!shared_memory_.CreateAndMapAnonymous(checked_size.ValueOrDie()))
+  shared_memory_region_ =
+      UnsafeSharedMemoryRegion::Create(checked_size.ValueOrDie());
+
+  if (!shared_memory_region_.IsValid())
     return false;
 
-  mapped_size_ =
-      shared_memory_.mapped_size() - AlignToPageSize(sizeof(SharedState));
+  shared_memory_mapping_ = shared_memory_region_.Map();
+  if (!shared_memory_mapping_.IsValid())
+    return false;
+
+  mapped_size_ = shared_memory_mapping_.mapped_size() -
+                 AlignToPageSize(sizeof(SharedState));
 
   locked_page_count_ = AlignToPageSize(mapped_size_) / base::GetPageSize();
 #if DCHECK_IS_ON()
@@ -175,17 +149,24 @@ bool DiscardableSharedMemory::CreateAndMap(size_t size) {
 
   DCHECK(last_known_usage_.is_null());
   SharedState new_state(SharedState::LOCKED, Time());
-  subtle::Release_Store(&SharedStateFromSharedMemory(shared_memory_)->value.i,
+  subtle::Release_Store(
+      &SharedStateFromSharedMemory(shared_memory_mapping_)->value.i,
       new_state.value.i);
   return true;
 }
 
 bool DiscardableSharedMemory::Map(size_t size) {
-  if (!shared_memory_.Map(AlignToPageSize(sizeof(SharedState)) + size))
+  DCHECK(!shared_memory_mapping_.IsValid());
+  if (shared_memory_mapping_.IsValid())
     return false;
 
-  mapped_size_ =
-      shared_memory_.mapped_size() - AlignToPageSize(sizeof(SharedState));
+  shared_memory_mapping_ = shared_memory_region_.MapAt(
+      0, AlignToPageSize(sizeof(SharedState)) + size);
+  if (!shared_memory_mapping_.IsValid())
+    return false;
+
+  mapped_size_ = shared_memory_mapping_.mapped_size() -
+                 AlignToPageSize(sizeof(SharedState));
 
   locked_page_count_ = AlignToPageSize(mapped_size_) / base::GetPageSize();
 #if DCHECK_IS_ON()
@@ -197,9 +178,10 @@ bool DiscardableSharedMemory::Map(size_t size) {
 }
 
 bool DiscardableSharedMemory::Unmap() {
-  if (!shared_memory_.Unmap())
+  if (!shared_memory_mapping_.IsValid())
     return false;
 
+  shared_memory_mapping_ = WritableSharedMemoryMapping();
   locked_page_count_ = 0;
 #if DCHECK_IS_ON()
   locked_pages_.clear();
@@ -216,7 +198,7 @@ DiscardableSharedMemory::LockResult DiscardableSharedMemory::Lock(
   // Calls to this function must be synchronized properly.
   DFAKE_SCOPED_LOCK(thread_collision_warner_);
 
-  DCHECK(shared_memory_.memory());
+  DCHECK(shared_memory_mapping_.IsValid());
 
   // We need to successfully acquire the platform independent lock before
   // individual pages can be locked.
@@ -229,9 +211,8 @@ DiscardableSharedMemory::LockResult DiscardableSharedMemory::Lock(
     SharedState old_state(SharedState::UNLOCKED, last_known_usage_);
     SharedState new_state(SharedState::LOCKED, Time());
     SharedState result(subtle::Acquire_CompareAndSwap(
-        &SharedStateFromSharedMemory(shared_memory_)->value.i,
-        old_state.value.i,
-        new_state.value.i));
+        &SharedStateFromSharedMemory(shared_memory_mapping_)->value.i,
+        old_state.value.i, new_state.value.i));
     if (result.value.u != old_state.value.u) {
       // Update |last_known_usage_| in case the above CAS failed because of
       // an incorrect timestamp.
@@ -267,7 +248,7 @@ DiscardableSharedMemory::LockResult DiscardableSharedMemory::Lock(
 
 #if defined(OS_ANDROID)
   // Ensure that the platform won't discard the required pages.
-  return LockPages(shared_memory_,
+  return LockPages(shared_memory_region_,
                    AlignToPageSize(sizeof(SharedState)) + offset, length);
 #elif defined(OS_MACOSX)
   // On macOS, there is no mechanism to lock pages. However, we do need to call
@@ -283,7 +264,7 @@ DiscardableSharedMemory::LockResult DiscardableSharedMemory::Lock(
   //
   // For more information, see
   // https://bugs.chromium.org/p/chromium/issues/detail?id=823915.
-  if (madvise(reinterpret_cast<char*>(shared_memory_.memory()) +
+  if (madvise(reinterpret_cast<char*>(shared_memory_mapping_.memory()) +
                   AlignToPageSize(sizeof(SharedState)),
               AlignToPageSize(mapped_size_), MADV_FREE_REUSE))
     ;
@@ -305,11 +286,11 @@ void DiscardableSharedMemory::Unlock(size_t offset, size_t length) {
   if (!length)
     length = AlignToPageSize(mapped_size_) - offset;
 
-  DCHECK(shared_memory_.memory());
+  DCHECK(shared_memory_mapping_.IsValid());
 
   // Allow the pages to be discarded by the platform, if supported.
-  UnlockPages(shared_memory_, AlignToPageSize(sizeof(SharedState)) + offset,
-              length);
+  UnlockPages(shared_memory_region_,
+              AlignToPageSize(sizeof(SharedState)) + offset, length);
 
   size_t start = offset / base::GetPageSize();
   size_t end = start + length / base::GetPageSize();
@@ -346,9 +327,8 @@ void DiscardableSharedMemory::Unlock(size_t offset, size_t length) {
   DCHECK_EQ((new_state.GetTimestamp() - Time::UnixEpoch()).InSeconds(),
             (current_time - Time::UnixEpoch()).InSeconds());
   SharedState result(subtle::Release_CompareAndSwap(
-      &SharedStateFromSharedMemory(shared_memory_)->value.i,
-      old_state.value.i,
-      new_state.value.i));
+      &SharedStateFromSharedMemory(shared_memory_mapping_)->value.i,
+      old_state.value.i, new_state.value.i));
 
   DCHECK_EQ(old_state.value.u, result.value.u);
 
@@ -356,21 +336,20 @@ void DiscardableSharedMemory::Unlock(size_t offset, size_t length) {
 }
 
 void* DiscardableSharedMemory::memory() const {
-  return reinterpret_cast<uint8_t*>(shared_memory_.memory()) +
+  return reinterpret_cast<uint8_t*>(shared_memory_mapping_.memory()) +
          AlignToPageSize(sizeof(SharedState));
 }
 
 bool DiscardableSharedMemory::Purge(Time current_time) {
   // Calls to this function must be synchronized properly.
   DFAKE_SCOPED_LOCK(thread_collision_warner_);
-  DCHECK(shared_memory_.memory());
+  DCHECK(shared_memory_mapping_.IsValid());
 
   SharedState old_state(SharedState::UNLOCKED, last_known_usage_);
   SharedState new_state(SharedState::UNLOCKED, Time());
   SharedState result(subtle::Acquire_CompareAndSwap(
-      &SharedStateFromSharedMemory(shared_memory_)->value.i,
-      old_state.value.i,
-      new_state.value.i));
+      &SharedStateFromSharedMemory(shared_memory_mapping_)->value.i,
+      old_state.value.i, new_state.value.i));
 
   // Update |last_known_usage_| to |current_time| if the memory is locked. This
   // allows the caller to determine if purging failed because last known usage
@@ -407,7 +386,7 @@ bool DiscardableSharedMemory::Purge(Time current_time) {
   // Advise the kernel to remove resources associated with purged pages.
   // Subsequent accesses of memory pages will succeed, but might result in
   // zero-fill-on-demand pages.
-  if (madvise(reinterpret_cast<char*>(shared_memory_.memory()) +
+  if (madvise(reinterpret_cast<char*>(shared_memory_mapping_.memory()) +
                   AlignToPageSize(sizeof(SharedState)),
               AlignToPageSize(mapped_size_), MADV_PURGE_ARGUMENT)) {
     DPLOG(ERROR) << "madvise() failed";
@@ -423,7 +402,7 @@ bool DiscardableSharedMemory::Purge(Time current_time) {
             GetModuleHandle(L"kernel32.dll"), "DiscardVirtualMemory"));
     if (discard_virtual_memory) {
       DWORD discard_result = discard_virtual_memory(
-          reinterpret_cast<char*>(shared_memory_.memory()) +
+          reinterpret_cast<char*>(shared_memory_mapping_.memory()) +
               AlignToPageSize(sizeof(SharedState)),
           AlignToPageSize(mapped_size_));
       if (discard_result != ERROR_SUCCESS) {
@@ -439,34 +418,34 @@ bool DiscardableSharedMemory::Purge(Time current_time) {
 }
 
 bool DiscardableSharedMemory::IsMemoryResident() const {
-  DCHECK(shared_memory_.memory());
+  DCHECK(shared_memory_mapping_.IsValid());
 
   SharedState result(subtle::NoBarrier_Load(
-      &SharedStateFromSharedMemory(shared_memory_)->value.i));
+      &SharedStateFromSharedMemory(shared_memory_mapping_)->value.i));
 
   return result.GetLockState() == SharedState::LOCKED ||
          !result.GetTimestamp().is_null();
 }
 
 bool DiscardableSharedMemory::IsMemoryLocked() const {
-  DCHECK(shared_memory_.memory());
+  DCHECK(shared_memory_mapping_.IsValid());
 
   SharedState result(subtle::NoBarrier_Load(
-      &SharedStateFromSharedMemory(shared_memory_)->value.i));
+      &SharedStateFromSharedMemory(shared_memory_mapping_)->value.i));
 
   return result.GetLockState() == SharedState::LOCKED;
 }
 
 void DiscardableSharedMemory::Close() {
-  shared_memory_.Close();
+  shared_memory_region_ = UnsafeSharedMemoryRegion();
 }
 
 void DiscardableSharedMemory::CreateSharedMemoryOwnershipEdge(
     trace_event::MemoryAllocatorDump* local_segment_dump,
     trace_event::ProcessMemoryDump* pmd,
     bool is_owned) const {
-  auto* shared_memory_dump =
-      SharedMemoryTracker::GetOrCreateSharedMemoryDump(&shared_memory_, pmd);
+  auto* shared_memory_dump = SharedMemoryTracker::GetOrCreateSharedMemoryDump(
+      shared_memory_mapping_, pmd);
   // TODO(ssid): Clean this by a new api to inherit size of parent dump once the
   // we send the full PMD and calculate sizes inside chrome, crbug.com/704203.
   size_t resident_size = shared_memory_dump->GetSizeInternal();
@@ -480,7 +459,7 @@ void DiscardableSharedMemory::CreateSharedMemoryOwnershipEdge(
   // TODO(ssid): Define better constants in MemoryAllocatorDump for importance
   // values, crbug.com/754793.
   const int kImportance = is_owned ? 2 : 0;
-  auto shared_memory_guid = shared_memory_.mapped_id();
+  auto shared_memory_guid = shared_memory_mapping_.guid();
   local_segment_dump->AddString("id", "hash", shared_memory_guid.ToString());
 
   // Owned discardable segments which are allocated by client process, could
@@ -496,6 +475,38 @@ void DiscardableSharedMemory::CreateSharedMemoryOwnershipEdge(
   }
 }
 
+// static
+DiscardableSharedMemory::LockResult DiscardableSharedMemory::LockPages(
+    const UnsafeSharedMemoryRegion& region,
+    size_t offset,
+    size_t length) {
+#if defined(OS_ANDROID)
+  if (region.IsValid()) {
+    int pin_result =
+        ashmem_pin_region(region.GetPlatformHandle(), offset, length);
+    if (pin_result == ASHMEM_WAS_PURGED)
+      return PURGED;
+    if (pin_result < 0)
+      return FAILED;
+  }
+#endif
+  return SUCCESS;
+}
+
+// static
+void DiscardableSharedMemory::UnlockPages(
+    const UnsafeSharedMemoryRegion& region,
+    size_t offset,
+    size_t length) {
+#if defined(OS_ANDROID)
+  if (region.IsValid()) {
+    int unpin_result =
+        ashmem_unpin_region(region.GetPlatformHandle(), offset, length);
+    DCHECK_EQ(0, unpin_result);
+  }
+#endif
+}
+
 Time DiscardableSharedMemory::Now() const {
   return Time::Now();
 }

base/memory/discardable_shared_memory.h

@@ -10,7 +10,8 @@
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "base/macros.h"
-#include "base/memory/shared_memory.h"
+#include "base/memory/shared_memory_mapping.h"
+#include "base/memory/unsafe_shared_memory_region.h"
 #include "base/threading/thread_collision_warner.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
@@ -49,7 +50,7 @@ class BASE_EXPORT DiscardableSharedMemory {
 
   // Create a new DiscardableSharedMemory object from an existing, open shared
   // memory file. Memory must be locked.
-  explicit DiscardableSharedMemory(SharedMemoryHandle handle);
+  explicit DiscardableSharedMemory(UnsafeSharedMemoryRegion region);
 
   // Closes any open files.
   virtual ~DiscardableSharedMemory();
@@ -71,14 +72,17 @@ class BASE_EXPORT DiscardableSharedMemory {
   // The actual size of the mapped memory (may be larger than requested).
   size_t mapped_size() const { return mapped_size_; }
 
-  // Returns a shared memory handle for this DiscardableSharedMemory object.
-  SharedMemoryHandle handle() const { return shared_memory_.handle(); }
+  // Returns a duplicated shared memory region for this DiscardableSharedMemory
+  // object.
+  UnsafeSharedMemoryRegion DuplicateRegion() const {
+    return shared_memory_region_.Duplicate();
+  }
 
   // Returns an ID for the shared memory region. This is ID of the mapped region
   // consistent across all processes and is valid as long as the region is not
   // unmapped.
   const UnguessableToken& mapped_id() const {
-    return shared_memory_.mapped_id();
+    return shared_memory_mapping_.guid();
   }
 
   // Locks a range of memory so that it will not be purged by the system.
@@ -147,10 +151,24 @@ class BASE_EXPORT DiscardableSharedMemory {
       bool is_owned) const;
 
  private:
+  // LockPages/UnlockPages are platform-native discardable page management
+  // helper functions. Both expect |offset| to be specified relative to the
+  // base address at which |memory| is mapped, and that |offset| and |length|
+  // are page-aligned by the caller.
+  // Returns SUCCESS on platforms which do not support discardable pages.
+  static LockResult LockPages(const UnsafeSharedMemoryRegion& region,
+                              size_t offset,
+                              size_t length);
+  // UnlockPages() is a no-op on platforms not supporting discardable pages.
+  static void UnlockPages(const UnsafeSharedMemoryRegion& region,
+                          size_t offset,
+                          size_t length);
+
   // Virtual for tests.
   virtual Time Now() const;
 
-  SharedMemory shared_memory_;
+  UnsafeSharedMemoryRegion shared_memory_region_;
+  WritableSharedMemoryMapping shared_memory_mapping_;
   size_t mapped_size_;
   size_t locked_page_count_;
 #if DCHECK_IS_ON()

base/memory/discardable_shared_memory_unittest.cc

@@ -15,14 +15,13 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
-namespace {
 
 class TestDiscardableSharedMemory : public DiscardableSharedMemory {
  public:
   TestDiscardableSharedMemory() = default;
 
-  explicit TestDiscardableSharedMemory(SharedMemoryHandle handle)
-      : DiscardableSharedMemory(handle) {}
+  explicit TestDiscardableSharedMemory(UnsafeSharedMemoryRegion region)
+      : DiscardableSharedMemory(std::move(region)) {}
 
   void SetNow(Time now) { now_ = now; }
 
@@ -50,10 +49,10 @@ TEST(DiscardableSharedMemoryTest, CreateFromHandle) {
   bool rv = memory1.CreateAndMap(kDataSize);
   ASSERT_TRUE(rv);
 
-  SharedMemoryHandle shared_handle = memory1.handle().Duplicate();
-  ASSERT_TRUE(shared_handle.IsValid());
+  UnsafeSharedMemoryRegion shared_region = memory1.DuplicateRegion();
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle);
+  TestDiscardableSharedMemory memory2(std::move(shared_region));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
   EXPECT_TRUE(memory2.IsMemoryLocked());
@@ -82,10 +81,10 @@ TEST(DiscardableSharedMemoryTest, LockAndUnlock) {
   EXPECT_EQ(DiscardableSharedMemory::SUCCESS, lock_rv);
   EXPECT_TRUE(memory1.IsMemoryLocked());
 
-  SharedMemoryHandle shared_handle = memory1.handle().Duplicate();
-  ASSERT_TRUE(shared_handle.IsValid());
+  UnsafeSharedMemoryRegion shared_region = memory1.DuplicateRegion();
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle);
+  TestDiscardableSharedMemory memory2(std::move(shared_region));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -118,10 +117,10 @@ TEST(DiscardableSharedMemoryTest, Purge) {
   bool rv = memory1.CreateAndMap(kDataSize);
   ASSERT_TRUE(rv);
 
-  SharedMemoryHandle shared_handle = memory1.handle().Duplicate();
-  ASSERT_TRUE(shared_handle.IsValid());
+  UnsafeSharedMemoryRegion shared_region = memory1.DuplicateRegion();
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle);
+  TestDiscardableSharedMemory memory2(std::move(shared_region));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -158,10 +157,10 @@ TEST(DiscardableSharedMemoryTest, LastUsed) {
   bool rv = memory1.CreateAndMap(kDataSize);
   ASSERT_TRUE(rv);
 
-  SharedMemoryHandle shared_handle = memory1.handle().Duplicate();
-  ASSERT_TRUE(shared_handle.IsValid());
+  UnsafeSharedMemoryRegion shared_region = memory1.DuplicateRegion();
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle);
+  TestDiscardableSharedMemory memory2(std::move(shared_region));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -224,10 +223,10 @@ TEST(DiscardableSharedMemoryTest, LockShouldAlwaysFailAfterSuccessfulPurge) {
   bool rv = memory1.CreateAndMap(kDataSize);
   ASSERT_TRUE(rv);
 
-  SharedMemoryHandle shared_handle = memory1.handle().Duplicate();
-  ASSERT_TRUE(shared_handle.IsValid());
+  UnsafeSharedMemoryRegion shared_region = memory1.DuplicateRegion();
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle);
+  TestDiscardableSharedMemory memory2(std::move(shared_region));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -242,16 +241,22 @@ TEST(DiscardableSharedMemoryTest, LockShouldAlwaysFailAfterSuccessfulPurge) {
   EXPECT_EQ(DiscardableSharedMemory::FAILED, lock_rv);
 }
 
+#if defined(OS_ANDROID)
 TEST(DiscardableSharedMemoryTest, LockShouldFailIfPlatformLockPagesFails) {
   const uint32_t kDataSize = 1024;
 
-  DiscardableSharedMemory memory;
-  bool rv = memory.CreateAndMap(kDataSize);
-  ASSERT_TRUE(rv);
+  DiscardableSharedMemory memory1;
+  bool rv1 = memory1.CreateAndMap(kDataSize);
+  ASSERT_TRUE(rv1);
+
+  base::UnsafeSharedMemoryRegion region = memory1.DuplicateRegion();
+  int fd = region.GetPlatformHandle();
+  DiscardableSharedMemory memory2(std::move(region));
+  bool rv2 = memory2.Map(kDataSize);
+  ASSERT_TRUE(rv2);
 
   // Unlock() the first page of memory, so we can test Lock()ing it.
-  memory.Unlock(0, base::GetPageSize());
-#if defined(OS_ANDROID)
+  memory2.Unlock(0, base::GetPageSize());
   // To cause ashmem_pin_region() to fail, we arrange for it to be called with
   // an invalid file-descriptor, which requires a valid-looking fd (i.e. we
   // can't just Close() |memory|), but one on which the operation is invalid.
@@ -260,15 +265,14 @@ TEST(DiscardableSharedMemoryTest, LockShouldFailIfPlatformLockPagesFails) {
   // that it can close, etc without errors, but on which ashmem_pin_region()
   // will fail.
   base::ScopedFD null(open("/dev/null", O_RDONLY));
-  ASSERT_EQ(memory.handle().GetHandle(),
-            dup2(null.get(), memory.handle().GetHandle()));
+  ASSERT_EQ(fd, dup2(null.get(), fd));
 
   // Now re-Lock()ing the first page should fail.
   DiscardableSharedMemory::LockResult lock_rv =
-      memory.Lock(0, base::GetPageSize());
+      memory2.Lock(0, base::GetPageSize());
   EXPECT_EQ(DiscardableSharedMemory::FAILED, lock_rv);
-#endif  // defined(OS_ANDROID)
 }
+#endif  // defined(OS_ANDROID)
 
 TEST(DiscardableSharedMemoryTest, LockAndUnlockRange) {
   const uint32_t kDataSize = 32;
@@ -279,10 +283,10 @@ TEST(DiscardableSharedMemoryTest, LockAndUnlockRange) {
   bool rv = memory1.CreateAndMap(data_size_in_bytes);
   ASSERT_TRUE(rv);
 
-  SharedMemoryHandle shared_handle = memory1.handle().Duplicate();
-  ASSERT_TRUE(shared_handle.IsValid());
+  UnsafeSharedMemoryRegion shared_region = memory1.DuplicateRegion();
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle);
+  TestDiscardableSharedMemory memory2(std::move(shared_region));
   rv = memory2.Map(data_size_in_bytes);
   ASSERT_TRUE(rv);
 
@@ -396,10 +400,10 @@ TEST(DiscardableSharedMemoryTest, ZeroFilledPagesAfterPurge) {
   bool rv = memory1.CreateAndMap(kDataSize);
   ASSERT_TRUE(rv);
 
-  SharedMemoryHandle shared_handle = memory1.handle().Duplicate();
-  ASSERT_TRUE(shared_handle.IsValid());
+  UnsafeSharedMemoryRegion shared_region = memory1.DuplicateRegion();
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle);
+  TestDiscardableSharedMemory memory2(std::move(shared_region));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -449,5 +453,4 @@ TEST(DiscardableSharedMemoryTest, TracingOwnershipEdges) {
   // CreateWeakSharedMemoryOwnershipEdge() is fixed, crbug.com/661257.
 }
 
-}  // namespace
 }  // namespace base

base/memory/shared_memory_tracker.cc

@@ -44,6 +44,15 @@ SharedMemoryTracker::GetOrCreateSharedMemoryDump(
                                              shared_memory->mapped_id(), pmd);
 }
 
+const trace_event::MemoryAllocatorDump*
+SharedMemoryTracker::GetOrCreateSharedMemoryDump(
+    const SharedMemoryMapping& shared_memory,
+    trace_event::ProcessMemoryDump* pmd) {
+  return GetOrCreateSharedMemoryDumpInternal(shared_memory.raw_memory_ptr(),
+                                             shared_memory.mapped_size(),
+                                             shared_memory.guid(), pmd);
+}
+
 void SharedMemoryTracker::IncrementMemoryUsage(
     const SharedMemory& shared_memory) {
   AutoLock hold(usages_lock_);

base/memory/shared_memory_tracker.h

@@ -38,11 +38,14 @@ class BASE_EXPORT SharedMemoryTracker : public trace_event::MemoryDumpProvider {
   static const trace_event::MemoryAllocatorDump* GetOrCreateSharedMemoryDump(
       const SharedMemory* shared_memory,
       trace_event::ProcessMemoryDump* pmd);
+  // We're in the middle of a refactor https://crbug.com/795291. Eventually, the
+  // first call will go away.
+  static const trace_event::MemoryAllocatorDump* GetOrCreateSharedMemoryDump(
+      const SharedMemoryMapping& shared_memory,
+      trace_event::ProcessMemoryDump* pmd);
 
   // Records shared memory usage on valid mapping.
   void IncrementMemoryUsage(const SharedMemory& shared_memory);
-  // We're in the middle of a refactor https://crbug.com/795291. Eventually, the
-  // first call will go away.
   void IncrementMemoryUsage(const SharedMemoryMapping& mapping);
 
   // Records shared memory usage on unmapping.

base/memory/unsafe_shared_memory_region.h

@@ -5,6 +5,7 @@
 #ifndef BASE_MEMORY_UNSAFE_SHARED_MEMORY_REGION_H_
 #define BASE_MEMORY_UNSAFE_SHARED_MEMORY_REGION_H_
 
+#include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/platform_shared_memory_region.h"
 #include "base/memory/shared_memory_mapping.h"
@@ -88,8 +89,19 @@ class BASE_EXPORT UnsafeSharedMemoryRegion {
   }
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(DiscardableSharedMemoryTest,
+                           LockShouldFailIfPlatformLockPagesFails);
+  friend class DiscardableSharedMemory;
+
   explicit UnsafeSharedMemoryRegion(subtle::PlatformSharedMemoryRegion handle);
 
+  // Returns a platform shared memory handle. |this| remains the owner of the
+  // handle.
+  subtle::PlatformSharedMemoryRegion::PlatformHandle GetPlatformHandle() const {
+    DCHECK(IsValid());
+    return handle_.GetPlatformHandle();
+  }
+
   subtle::PlatformSharedMemoryRegion handle_;
 
   DISALLOW_COPY_AND_ASSIGN(UnsafeSharedMemoryRegion);

components/discardable_memory/client/client_discardable_shared_memory_manager.cc

@@ -25,7 +25,6 @@
 #include "base/trace_event/memory_dump_manager.h"
 #include "base/trace_event/trace_event.h"
 #include "components/crash/core/common/crash_key.h"
-#include "mojo/public/cpp/system/platform_handle.h"
 
 namespace discardable_memory {
 namespace {
@@ -357,7 +356,7 @@ ClientDiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
                "ClientDiscardableSharedMemoryManager::"
                "AllocateLockedDiscardableSharedMemory",
                "size", size, "id", id);
-  base::SharedMemoryHandle handle;
+  base::UnsafeSharedMemoryRegion region;
   base::WaitableEvent event(base::WaitableEvent::ResetPolicy::MANUAL,
                             base::WaitableEvent::InitialState::NOT_SIGNALED);
   base::ScopedClosureRunner event_signal_runner(
@@ -365,11 +364,12 @@ ClientDiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
   io_task_runner_->PostTask(
       FROM_HERE,
       base::BindOnce(&ClientDiscardableSharedMemoryManager::AllocateOnIO,
-                     base::Unretained(this), size, id, &handle,
+                     base::Unretained(this), size, id, &region,
                      std::move(event_signal_runner)));
   // Waiting until IPC has finished on the IO thread.
   event.Wait();
-  auto memory = std::make_unique<base::DiscardableSharedMemory>(handle);
+  auto memory =
+      std::make_unique<base::DiscardableSharedMemory>(std::move(region));
   if (!memory->Map(size))
     base::TerminateBecauseOutOfMemory(size);
   return memory;
@@ -378,25 +378,21 @@ ClientDiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
 void ClientDiscardableSharedMemoryManager::AllocateOnIO(
     size_t size,
     int32_t id,
-    base::SharedMemoryHandle* handle,
+    base::UnsafeSharedMemoryRegion* region,
     base::ScopedClosureRunner closure_runner) {
   (*manager_mojo_)
       ->AllocateLockedDiscardableSharedMemory(
           static_cast<uint32_t>(size), id,
           base::BindOnce(
               &ClientDiscardableSharedMemoryManager::AllocateCompletedOnIO,
-              base::Unretained(this), handle, std::move(closure_runner)));
+              base::Unretained(this), region, std::move(closure_runner)));
 }
 
 void ClientDiscardableSharedMemoryManager::AllocateCompletedOnIO(
-    base::SharedMemoryHandle* handle,
+    base::UnsafeSharedMemoryRegion* region,
     base::ScopedClosureRunner closure_runner,
-    mojo::ScopedSharedBufferHandle mojo_handle) {
-  if (!mojo_handle.is_valid())
-    return;
-  auto result = mojo::UnwrapSharedMemoryHandle(std::move(mojo_handle), handle,
-                                               nullptr, nullptr);
-  DCHECK_EQ(result, MOJO_RESULT_OK);
+    base::UnsafeSharedMemoryRegion ret_region) {
+  *region = std::move(ret_region);
 }
 
 void ClientDiscardableSharedMemoryManager::DeletedDiscardableSharedMemory(

components/discardable_memory/client/client_discardable_shared_memory_manager.h

@@ -11,7 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/discardable_memory_allocator.h"
 #include "base/memory/ref_counted.h"
-#include "base/memory/shared_memory_handle.h"
+#include "base/memory/unsafe_shared_memory_region.h"
 #include "base/synchronization/lock.h"
 #include "base/trace_event/memory_dump_provider.h"
 #include "components/discardable_memory/common/discardable_memory_export.h"
@@ -67,11 +67,11 @@ class DISCARDABLE_MEMORY_EXPORT ClientDiscardableSharedMemoryManager
   AllocateLockedDiscardableSharedMemory(size_t size, int32_t id);
   void AllocateOnIO(size_t size,
                     int32_t id,
-                    base::SharedMemoryHandle* handle,
+                    base::UnsafeSharedMemoryRegion* region,
                     base::ScopedClosureRunner closure_runner);
-  void AllocateCompletedOnIO(base::SharedMemoryHandle* handle,
+  void AllocateCompletedOnIO(base::UnsafeSharedMemoryRegion* region,
                              base::ScopedClosureRunner closure_runner,
-                             mojo::ScopedSharedBufferHandle mojo_handle);
+                             base::UnsafeSharedMemoryRegion ret_region);
 
   void DeletedDiscardableSharedMemory(int32_t id);
   void MemoryUsageChanged(size_t new_bytes_allocated,

components/discardable_memory/public/interfaces/BUILD.gn

@@ -14,4 +14,8 @@ mojom("interfaces") {
     get_path_info("../../../..", "abspath"),
     "//mojo/services",
   ]
+
+  public_deps = [
+    "//mojo/public/mojom/base",
+  ]
 }

components/discardable_memory/public/interfaces/discardable_shared_memory_manager.mojom

@@ -4,13 +4,15 @@
 
 module discardable_memory.mojom;
 
+import "mojo/public/mojom/base/shared_memory.mojom";
+
 // This interface is used for allocating discardable shared memory from browser
 // process. For mus+ash, this service will live in mus process.
 interface DiscardableSharedMemoryManager {
   // Allocate a locked discardable shared memory segment.
   AllocateLockedDiscardableSharedMemory(
       uint32 size,
-      int32 id) => (handle<shared_buffer>? memory);
+      int32 id) => (mojo_base.mojom.UnsafeSharedMemoryRegion region);
   // Notify manager that a memory segment has been deleted.
   DeletedDiscardableSharedMemory(int32 id);
 };

components/discardable_memory/service/discardable_shared_memory_manager.cc

@@ -31,7 +31,6 @@
 #include "components/crash/core/common/crash_key.h"
 #include "components/discardable_memory/common/discardable_shared_memory_heap.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
-#include "mojo/public/cpp/system/platform_handle.h"
 
 #if defined(OS_LINUX)
 #include "base/files/file_path.h"
@@ -69,16 +68,12 @@ class MojoDiscardableSharedMemoryManagerImpl
       uint32_t size,
       int32_t id,
       AllocateLockedDiscardableSharedMemoryCallback callback) override {
-    base::SharedMemoryHandle handle;
-    mojo::ScopedSharedBufferHandle memory;
+    base::UnsafeSharedMemoryRegion region;
     if (manager_) {
       manager_->AllocateLockedDiscardableSharedMemoryForClient(client_id_, size,
-                                                               id, &handle);
-      memory = mojo::WrapSharedMemoryHandle(
-          handle, size,
-          mojo::UnwrappedSharedMemoryHandleProtection::kReadWrite);
+                                                               id, &region);
     }
-    std::move(callback).Run(std::move(memory));
+    std::move(callback).Run(std::move(region));
   }
 
   void DeletedDiscardableSharedMemory(int32_t id) override {
@@ -288,11 +283,11 @@ DiscardableSharedMemoryManager::AllocateLockedDiscardableMemory(size_t size) {
 
   // Note: Use DiscardableSharedMemoryHeap for in-process allocation
   // of discardable memory if the cost of each allocation is too high.
-  base::SharedMemoryHandle handle;
+  base::UnsafeSharedMemoryRegion region;
   AllocateLockedDiscardableSharedMemory(kInvalidUniqueClientID, size, new_id,
-                                        &handle);
+                                        &region);
   std::unique_ptr<base::DiscardableSharedMemory> memory(
-      new base::DiscardableSharedMemory(handle));
+      new base::DiscardableSharedMemory(std::move(region)));
   if (!memory->Map(size))
     base::TerminateBecauseOutOfMemory(size);
   // Close file descriptor to avoid running out.
@@ -354,9 +349,9 @@ void DiscardableSharedMemoryManager::
         int client_id,
         size_t size,
         int32_t id,
-        base::SharedMemoryHandle* shared_memory_handle) {
+        base::UnsafeSharedMemoryRegion* shared_memory_region) {
   AllocateLockedDiscardableSharedMemory(client_id, size, id,
-                                        shared_memory_handle);
+                                        shared_memory_region);
 }
 
 void DiscardableSharedMemoryManager::ClientDeletedDiscardableSharedMemory(
@@ -443,14 +438,14 @@ void DiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
     int client_id,
     size_t size,
     int32_t id,
-    base::SharedMemoryHandle* shared_memory_handle) {
+    base::UnsafeSharedMemoryRegion* shared_memory_region) {
   base::AutoLock lock(lock_);
 
   // Make sure |id| is not already in use.
   MemorySegmentMap& client_segments = clients_[client_id];
   if (client_segments.find(id) != client_segments.end()) {
     LOG(ERROR) << "Invalid discardable shared memory ID";
-    *shared_memory_handle = base::SharedMemoryHandle();
+    *shared_memory_region = base::UnsafeSharedMemoryRegion();
     return;
   }
 
@@ -471,21 +466,21 @@ void DiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
   std::unique_ptr<base::DiscardableSharedMemory> memory(
       new base::DiscardableSharedMemory);
   if (!memory->CreateAndMap(size)) {
-    *shared_memory_handle = base::SharedMemoryHandle();
+    *shared_memory_region = base::UnsafeSharedMemoryRegion();
     return;
   }
 
   base::CheckedNumeric<size_t> checked_bytes_allocated = bytes_allocated_;
   checked_bytes_allocated += memory->mapped_size();
   if (!checked_bytes_allocated.IsValid()) {
-    *shared_memory_handle = base::SharedMemoryHandle();
+    *shared_memory_region = base::UnsafeSharedMemoryRegion();
     return;
   }
 
   bytes_allocated_ = checked_bytes_allocated.ValueOrDie();
   BytesAllocatedChanged(bytes_allocated_);
 
-  *shared_memory_handle = base::SharedMemory::DuplicateHandle(memory->handle());
+  *shared_memory_region = memory->DuplicateRegion();
   // Close file descriptor to avoid running out.
   memory->Close();
 

components/discardable_memory/service/discardable_shared_memory_manager.h

@@ -20,7 +20,7 @@
 #include "base/memory/memory_coordinator_client.h"
 #include "base/memory/memory_pressure_listener.h"
 #include "base/memory/ref_counted.h"
-#include "base/memory/shared_memory.h"
+#include "base/memory/unsafe_shared_memory_region.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_loop_current.h"
@@ -68,12 +68,12 @@ class DISCARDABLE_MEMORY_EXPORT DiscardableSharedMemoryManager
                     base::trace_event::ProcessMemoryDump* pmd) override;
 
   // This allocates a discardable memory segment for |process_handle|.
-  // A valid shared memory handle is returned on success.
+  // A valid shared memory region is returned on success.
   void AllocateLockedDiscardableSharedMemoryForClient(
       int client_id,
       size_t size,
       int32_t id,
-      base::SharedMemoryHandle* shared_memory_handle);
+      base::UnsafeSharedMemoryRegion* shared_memory_region);
 
   // Call this to notify the manager that client process associated with
   // |client_id| has deleted discardable memory segment with |id|.
@@ -128,7 +128,7 @@ class DISCARDABLE_MEMORY_EXPORT DiscardableSharedMemoryManager
       int client_id,
       size_t size,
       int32_t id,
-      base::SharedMemoryHandle* shared_memory_handle);
+      base::UnsafeSharedMemoryRegion* shared_memory_region);
   void DeletedDiscardableSharedMemory(int32_t id, int client_id);
   void OnMemoryPressure(
       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);

components/discardable_memory/service/discardable_shared_memory_manager_unittest.cc

@@ -20,8 +20,8 @@ class TestDiscardableSharedMemory : public base::DiscardableSharedMemory {
  public:
   TestDiscardableSharedMemory() {}
 
-  explicit TestDiscardableSharedMemory(base::SharedMemoryHandle handle)
-      : DiscardableSharedMemory(handle) {}
+  explicit TestDiscardableSharedMemory(base::UnsafeSharedMemoryRegion region)
+      : DiscardableSharedMemory(std::move(region)) {}
 
   void SetNow(base::Time now) { now_ = now; }
 
@@ -75,12 +75,12 @@ TEST_F(DiscardableSharedMemoryManagerTest, AllocateForClient) {
   uint8_t data[kDataSize];
   memset(data, 0x80, kDataSize);
 
-  base::SharedMemoryHandle shared_handle;
+  base::UnsafeSharedMemoryRegion shared_region;
   manager_->AllocateLockedDiscardableSharedMemoryForClient(
-      kInvalidUniqueID, kDataSize, 0, &shared_handle);
-  ASSERT_TRUE(base::SharedMemory::IsHandleValid(shared_handle));
+      kInvalidUniqueID, kDataSize, 0, &shared_region);
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory(shared_handle);
+  TestDiscardableSharedMemory memory(std::move(shared_region));
   bool rv = memory.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -96,21 +96,21 @@ TEST_F(DiscardableSharedMemoryManagerTest, AllocateForClient) {
 TEST_F(DiscardableSharedMemoryManagerTest, Purge) {
   const int kDataSize = 1024;
 
-  base::SharedMemoryHandle shared_handle1;
+  base::UnsafeSharedMemoryRegion shared_region1;
   manager_->AllocateLockedDiscardableSharedMemoryForClient(
-      kInvalidUniqueID, kDataSize, 1, &shared_handle1);
-  ASSERT_TRUE(base::SharedMemory::IsHandleValid(shared_handle1));
+      kInvalidUniqueID, kDataSize, 1, &shared_region1);
+  ASSERT_TRUE(shared_region1.IsValid());
 
-  TestDiscardableSharedMemory memory1(shared_handle1);
+  TestDiscardableSharedMemory memory1(std::move(shared_region1));
   bool rv = memory1.Map(kDataSize);
   ASSERT_TRUE(rv);
 
-  base::SharedMemoryHandle shared_handle2;
+  base::UnsafeSharedMemoryRegion shared_region2;
   manager_->AllocateLockedDiscardableSharedMemoryForClient(
-      kInvalidUniqueID, kDataSize, 2, &shared_handle2);
-  ASSERT_TRUE(base::SharedMemory::IsHandleValid(shared_handle2));
+      kInvalidUniqueID, kDataSize, 2, &shared_region2);
+  ASSERT_TRUE(shared_region2.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle2);
+  TestDiscardableSharedMemory memory2(std::move(shared_region2));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -160,12 +160,12 @@ TEST_F(DiscardableSharedMemoryManagerTest, Purge) {
 TEST_F(DiscardableSharedMemoryManagerTest, EnforceMemoryPolicy) {
   const int kDataSize = 1024;
 
-  base::SharedMemoryHandle shared_handle;
+  base::UnsafeSharedMemoryRegion shared_region;
   manager_->AllocateLockedDiscardableSharedMemoryForClient(
-      kInvalidUniqueID, kDataSize, 0, &shared_handle);
-  ASSERT_TRUE(base::SharedMemory::IsHandleValid(shared_handle));
+      kInvalidUniqueID, kDataSize, 0, &shared_region);
+  ASSERT_TRUE(shared_region.IsValid());
 
-  TestDiscardableSharedMemory memory(shared_handle);
+  TestDiscardableSharedMemory memory(std::move(shared_region));
   bool rv = memory.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -198,21 +198,21 @@ TEST_F(DiscardableSharedMemoryManagerTest,
        ReduceMemoryAfterSegmentHasBeenDeleted) {
   const int kDataSize = 1024;
 
-  base::SharedMemoryHandle shared_handle1;
+  base::UnsafeSharedMemoryRegion shared_region1;
   manager_->AllocateLockedDiscardableSharedMemoryForClient(
-      kInvalidUniqueID, kDataSize, 1, &shared_handle1);
-  ASSERT_TRUE(base::SharedMemory::IsHandleValid(shared_handle1));
+      kInvalidUniqueID, kDataSize, 1, &shared_region1);
+  ASSERT_TRUE(shared_region1.IsValid());
 
-  TestDiscardableSharedMemory memory1(shared_handle1);
+  TestDiscardableSharedMemory memory1(std::move(shared_region1));
   bool rv = memory1.Map(kDataSize);
   ASSERT_TRUE(rv);
 
-  base::SharedMemoryHandle shared_handle2;
+  base::UnsafeSharedMemoryRegion shared_region2;
   manager_->AllocateLockedDiscardableSharedMemoryForClient(
-      kInvalidUniqueID, kDataSize, 2, &shared_handle2);
-  ASSERT_TRUE(base::SharedMemory::IsHandleValid(shared_handle2));
+      kInvalidUniqueID, kDataSize, 2, &shared_region2);
+  ASSERT_TRUE(shared_region2.IsValid());
 
-  TestDiscardableSharedMemory memory2(shared_handle2);
+  TestDiscardableSharedMemory memory2(std::move(shared_region2));
   rv = memory2.Map(kDataSize);
   ASSERT_TRUE(rv);
 
@@ -261,10 +261,10 @@ TEST_F(DiscardableSharedMemoryManagerScheduleEnforceMemoryPolicyTest,
        SetMemoryLimitOnSimpleThread) {
   const int kDataSize = 1024;
 
-  base::SharedMemoryHandle shared_handle;
+  base::UnsafeSharedMemoryRegion shared_region;
   manager_->AllocateLockedDiscardableSharedMemoryForClient(
-      kInvalidUniqueID, kDataSize, 0, &shared_handle);
-  ASSERT_TRUE(base::SharedMemory::IsHandleValid(shared_handle));
+      kInvalidUniqueID, kDataSize, 0, &shared_region);
+  ASSERT_TRUE(shared_region.IsValid());
 
   // Set the memory limit to a value that will require EnforceMemoryPolicy()
   // to be schedule on a thread without a message loop.