[Memory] Add SetRandomMmapSeed function to v8::internal.

- Adds SetRandomMmapSeed method.
- Removes random seed from OS::Initialize signature.

Bug: chromium:756050
Change-Id: I46ef6a92efb8b97541b90383d08776dd73a35a0c
Reviewed-on: https://chromium-review.googlesource.com/836907Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50280}

src/allocation.cc

@@ -123,8 +123,13 @@ STATIC_ASSERT_ENUM(MemoryPermission::kReadExecute,
 class DefaultMemoryManager {
  public:
   static size_t AllocatePageSize() { return base::OS::AllocatePageSize(); }
+
   static size_t CommitPageSize() { return base::OS::CommitPageSize(); }
 
+  static void SetRandomMmapSeed(int64_t seed) {
+    base::OS::SetRandomMmapSeed(seed);
+  }
+
   static void* GetRandomMmapAddr() { return base::OS::GetRandomMmapAddr(); }
 
   static void* AllocatePages(void* address, size_t size, size_t alignment,
@@ -174,7 +179,10 @@ size_t AllocatePageSize() { return DefaultMemoryManager::AllocatePageSize(); }
 
 size_t CommitPageSize() { return DefaultMemoryManager::CommitPageSize(); }
 
-// Generate a random address to be used for hinting allocation calls.
+void SetRandomMmapSeed(int64_t seed) {
+  DefaultMemoryManager::SetRandomMmapSeed(seed);
+}
+
 void* GetRandomMmapAddr() { return DefaultMemoryManager::GetRandomMmapAddr(); }
 
 void* AllocatePages(void* address, size_t size, size_t alignment,

src/allocation.h

@@ -92,6 +92,9 @@ V8_EXPORT_PRIVATE size_t AllocatePageSize();
 // Gets the granularity at which the permissions and release calls can be made.
 V8_EXPORT_PRIVATE size_t CommitPageSize();
 
+// Sets the random seed for repeatable sequences of random mmap addresses.
+V8_EXPORT_PRIVATE void SetRandomMmapSeed(int64_t seed);
+
 // Generate a random address to be used for hinting allocation calls.
 V8_EXPORT_PRIVATE void* GetRandomMmapAddr();
 

src/base/platform/platform-posix.cc

@@ -166,11 +166,7 @@ int ReclaimInaccessibleMemory(void* address, size_t size) {
 
 }  // namespace
 
-void OS::Initialize(int64_t random_seed, bool hard_abort,
-                    const char* const gc_fake_mmap) {
-  if (random_seed) {
-    platform_random_number_generator.Pointer()->SetSeed(random_seed);
-  }
+void OS::Initialize(bool hard_abort, const char* const gc_fake_mmap) {
   g_hard_abort = hard_abort;
   g_gc_fake_mmap = gc_fake_mmap;
 }
@@ -205,6 +201,14 @@ size_t OS::CommitPageSize() {
   return page_size;
 }
 
+// static
+void OS::SetRandomMmapSeed(int64_t seed) {
+  if (seed) {
+    LockGuard<Mutex> guard(rng_mutex.Pointer());
+    platform_random_number_generator.Pointer()->SetSeed(seed);
+  }
+}
+
 // static
 void* OS::GetRandomMmapAddr() {
   uintptr_t raw_addr;

src/base/platform/platform-win32.cc

@@ -674,8 +674,15 @@ void OS::StrNCpy(char* dest, int length, const char* src, size_t n) {
 #undef _TRUNCATE
 #undef STRUNCATE
 
-// The allocation alignment is the guaranteed alignment for
-// VirtualAlloc'ed blocks of memory.
+static LazyInstance<RandomNumberGenerator>::type
+    platform_random_number_generator = LAZY_INSTANCE_INITIALIZER;
+static LazyMutex rng_mutex = LAZY_MUTEX_INITIALIZER;
+
+void OS::Initialize(bool hard_abort, const char* const gc_fake_mmap) {
+  g_hard_abort = hard_abort;
+}
+
+// static
 size_t OS::AllocatePageSize() {
   static size_t allocate_alignment = 0;
   if (allocate_alignment == 0) {
@@ -686,6 +693,7 @@ size_t OS::AllocatePageSize() {
   return allocate_alignment;
 }
 
+// static
 size_t OS::CommitPageSize() {
   static size_t page_size = 0;
   if (page_size == 0) {
@@ -697,18 +705,15 @@ size_t OS::CommitPageSize() {
   return page_size;
 }
 
-static LazyInstance<RandomNumberGenerator>::type
-    platform_random_number_generator = LAZY_INSTANCE_INITIALIZER;
-static LazyMutex rng_mutex = LAZY_MUTEX_INITIALIZER;
-
-void OS::Initialize(int64_t random_seed, bool hard_abort,
-                    const char* const gc_fake_mmap) {
-  if (random_seed) {
-    platform_random_number_generator.Pointer()->SetSeed(random_seed);
+// static
+void OS::SetRandomMmapSeed(int64_t seed) {
+  if (seed) {
+    LockGuard<Mutex> guard(rng_mutex.Pointer());
+    platform_random_number_generator.Pointer()->SetSeed(seed);
   }
-  g_hard_abort = hard_abort;
 }
 
+// static
 void* OS::GetRandomMmapAddr() {
 // The address range used to randomize RWX allocations in OS::Allocate
 // Try not to map pages into the default range that windows loads DLLs

src/base/platform/platform.h

@@ -113,11 +113,9 @@ class TimezoneCache;
 class V8_BASE_EXPORT OS {
  public:
   // Initialize the OS class.
-  // - random_seed: Used for the GetRandomMmapAddress() if non-zero.
   // - hard_abort: If true, OS::Abort() will crash instead of aborting.
   // - gc_fake_mmap: Name of the file for fake gc mmap used in ll_prof.
-  static void Initialize(int64_t random_seed, bool hard_abort,
-                         const char* const gc_fake_mmap);
+  static void Initialize(bool hard_abort, const char* const gc_fake_mmap);
 
   // Returns the accumulated user time for thread. This routine
   // can be used for profiling. The implementation should
@@ -264,6 +262,8 @@ class V8_BASE_EXPORT OS {
 
   static size_t CommitPageSize();
 
+  static void SetRandomMmapSeed(int64_t seed);
+
   static void* GetRandomMmapAddr();
 
   V8_WARN_UNUSED_RESULT static void* Allocate(void* address, size_t size,

src/v8.cc

@@ -69,7 +69,9 @@ void V8::InitializeOncePerProcessImpl() {
     FLAG_max_semi_space_size = 1;
   }
 
-  base::OS::Initialize(FLAG_random_seed, FLAG_hard_abort, FLAG_gc_fake_mmap);
+  base::OS::Initialize(FLAG_hard_abort, FLAG_gc_fake_mmap);
+
+  if (FLAG_random_seed) SetRandomMmapSeed(FLAG_random_seed);
 
   Isolate::InitializeOncePerProcess();