[ArrayBuffer] Give each SecurityOrigin a Partition for ArrayBuffers.

- Goes through SecurityOrigin's ArrayBuffer Partition for ArrayBuffers
  allocated from the V8 side.
- Reworks ArrayBufferContents to support multiple partitions for
  ArrayBuffers. Adds overload of AllocateMemoryOrNull to handle these
  allocations. Associates a PartitionRootGeneric with each allocation,
  storing a pointer just before the ArrayBuffer data.

Bug:chromium:799573

Change-Id: I712176c715d1fb2511d87892052ba9d2d8084336
Reviewed-on: https://chromium-review.googlesource.com/853120Reviewed-by: Chris Palmer <palmer@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533921}

third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp

@@ -541,18 +541,33 @@ static void InitializeV8Common(v8::Isolate* isolate) {
 
 namespace {
 
+// We try to give each SecurityOrigin its own array buffer partition. Use a
+// SecurityOrigin pointer as an opaque key to tell ArrayBufferContents which
+// partition to use.
+void* GetPartitionKey() {
+  // TODO(bbudge): Pass in the isolate parameter from V8.
+  v8::Isolate* isolate = v8::Isolate::GetCurrent();
+  blink::ExecutionContext* context = CurrentExecutionContext(isolate);
+  // In some tests, there is no execution context.
+  if (!context)
+    return reinterpret_cast<void*>(isolate);
+
+  return reinterpret_cast<void*>(
+      const_cast<SecurityOrigin*>(context->GetSecurityOrigin()));
+}
+
 class ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
   // Allocate() methods return null to signal allocation failure to V8, which
   // should respond by throwing a RangeError, per
   // http://www.ecma-international.org/ecma-262/6.0/#sec-createbytedatablock.
   void* Allocate(size_t size) override {
     return WTF::ArrayBufferContents::AllocateMemoryOrNull(
-        size, WTF::ArrayBufferContents::kZeroInitialize);
+        GetPartitionKey(), size, WTF::ArrayBufferContents::kZeroInitialize);
   }
 
   void* AllocateUninitialized(size_t size) override {
     return WTF::ArrayBufferContents::AllocateMemoryOrNull(
-        size, WTF::ArrayBufferContents::kDontInitialize);
+        GetPartitionKey(), size, WTF::ArrayBufferContents::kDontInitialize);
   }
 
   void Free(void* data, size_t size) override {

third_party/WebKit/Source/platform/wtf/typed_arrays/ArrayBufferContents.cpp

@@ -33,10 +33,43 @@
 #endif
 #include "base/allocator/partition_allocator/partition_alloc.h"
 #include "platform/wtf/Assertions.h"
+#include "platform/wtf/CheckedNumeric.h"
+#include "platform/wtf/Vector.h"
 #include "platform/wtf/allocator/Partitions.h"
-
 namespace WTF {
 
+namespace {
+
+// Partitions are expensive; limit them so we don't run out of memory.
+constexpr size_t kMaxPartitions = 4;
+
+typedef std::unique_ptr<base::PartitionAllocatorGeneric> PartitionPtr;
+// Use a vector of key/value pairs as a small map.
+typedef std::pair<void*, PartitionPtr> PartitionEntry;
+typedef WTF::Vector<PartitionEntry, kMaxPartitions> PartitionVector;
+
+base::PartitionRootGeneric* FindOrCreatePartition(void* partition_key) {
+  DEFINE_THREAD_SAFE_STATIC_LOCAL(PartitionVector, partitions, ());
+  for (auto& entry : partitions) {
+    if (entry.first == partition_key) {
+      return entry.second->root();
+    }
+  }
+  if (partitions.size() < kMaxPartitions) {
+    partitions.emplace_back(std::make_pair(
+        partition_key, PartitionPtr(new base::PartitionAllocatorGeneric)));
+    auto& partition = partitions.back().second;
+    partition->init();
+    return partition->root();
+  }
+  // Use the global partition if we're at the limit.
+  // TODO(crbug.com/799573) Make sure the main frame doesn't use the global
+  // partition.
+  return Partitions::ArrayBufferPartition();
+}
+
+}  // namespace
+
 void ArrayBufferContents::DefaultAdjustAmountOfExternalAllocatedMemoryFunction(
     int64_t diff) {
   // Do nothing by default.
@@ -108,20 +141,37 @@ void ArrayBufferContents::CopyTo(ArrayBufferContents& other) {
   other.holder_->CopyMemoryFrom(*holder_);
 }
 
-void* ArrayBufferContents::AllocateMemoryWithFlags(size_t size,
-                                                   InitializationPolicy policy,
-                                                   int flags) {
-  void* data = PartitionAllocGenericFlags(
-      Partitions::ArrayBufferPartition(), flags, size,
+void* ArrayBufferContents::AllocateMemoryWithFlags(
+    base::PartitionRootGeneric* partition_root,
+    size_t size,
+    InitializationPolicy policy,
+    int flags) {
+  // Allocate extra space for a partition pointer at the beginning.
+  size_t alloc_size = CheckAdd(size, sizeof(void*)).ValueOrDie();
+  void* base_ptr = PartitionAllocGenericFlags(
+      partition_root, flags, alloc_size,
       WTF_HEAP_PROFILER_TYPE_NAME(ArrayBufferContents));
-  if (policy == kZeroInitialize && data)
+  if (!base_ptr)
+    return nullptr;
+  void** partition_root_ptr = reinterpret_cast<void**>(base_ptr);
+  *partition_root_ptr = partition_root;
+  void* data = reinterpret_cast<void*>(partition_root_ptr + 1);
+  if (policy == kZeroInitialize)
     memset(data, '\0', size);
   return data;
 }
 
 void* ArrayBufferContents::AllocateMemoryOrNull(size_t size,
                                                 InitializationPolicy policy) {
-  return AllocateMemoryWithFlags(size, policy, base::PartitionAllocReturnNull);
+  return AllocateMemoryWithFlags(Partitions::ArrayBufferPartition(), size,
+                                 policy, base::PartitionAllocReturnNull);
+}
+
+void* ArrayBufferContents::AllocateMemoryOrNull(void* partition_key,
+                                                size_t size,
+                                                InitializationPolicy policy) {
+  return AllocateMemoryWithFlags(FindOrCreatePartition(partition_key), size,
+                                 policy, base::PartitionAllocReturnNull);
 }
 
 // This method is used by V8's WebAssembly implementation to reserve a large
@@ -152,7 +202,11 @@ void* ArrayBufferContents::ReserveMemory(size_t size) {
 }
 
 void ArrayBufferContents::FreeMemory(void* data) {
-  Partitions::ArrayBufferPartition()->Free(data);
+  // The partition pointer is just before |data|. See |AllocateMemoryWithFlags|.
+  base::PartitionRootGeneric** partition_root_ptr =
+      reinterpret_cast<base::PartitionRootGeneric**>(data) - 1;
+  void* base_ptr = reinterpret_cast<void*>(partition_root_ptr);
+  (*partition_root_ptr)->Free(base_ptr);
 }
 
 void ArrayBufferContents::ReleaseReservedMemory(void* data, size_t size) {

third_party/WebKit/Source/platform/wtf/typed_arrays/ArrayBufferContents.h

@@ -35,6 +35,10 @@
 #include "platform/wtf/WTF.h"
 #include "platform/wtf/WTFExport.h"
 
+namespace base {
+struct PartitionRootGeneric;
+}  // namespace base
+
 namespace WTF {
 
 class WTF_EXPORT ArrayBufferContents {
@@ -177,8 +181,9 @@ class WTF_EXPORT ArrayBufferContents {
   void CopyTo(ArrayBufferContents& other);
 
   static void* AllocateMemoryOrNull(size_t, InitializationPolicy);
-  static void* ReserveMemory(size_t);
+  static void* AllocateMemoryOrNull(void*, size_t, InitializationPolicy);
   static void FreeMemory(void*);
+  static void* ReserveMemory(size_t);
   static void ReleaseReservedMemory(void*, size_t);
   static DataHandle CreateDataHandle(size_t, InitializationPolicy);
   static void Initialize(
@@ -200,7 +205,10 @@ class WTF_EXPORT ArrayBufferContents {
   }
 
  private:
-  static void* AllocateMemoryWithFlags(size_t, InitializationPolicy, int);
+  static void* AllocateMemoryWithFlags(base::PartitionRootGeneric*,
+                                       size_t,
+                                       InitializationPolicy,
+                                       int);
 
   static void DefaultAdjustAmountOfExternalAllocatedMemoryFunction(
       int64_t diff);