[memory] Make sure parameters are properly aligned in AllocatePages.

- Adds a DCHECK to AllocatePages to enforce hint address alignment.
- Adds a DCHECK to AllocatePages to make length a multiple of allocation
  granularity.
- Properly aligns the hint address in MemoryAllocator::AllocateChunk
  to MemoryChunk::kAlignment.

This is to conform more closely to Chromium's page allocator API.

Bug:chromium:756050

Change-Id: Ib991fa80609834107829a9559f4b5b6b0996fc72
Reviewed-on: https://chromium-review.googlesource.com/898095
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51065}

src/allocation.cc

@@ -143,6 +143,8 @@ void* GetRandomMmapAddr() { return GetPageAllocator()->GetRandomMmapAddr(); }
 
 void* AllocatePages(void* address, size_t size, size_t alignment,
                     PageAllocator::Permission access) {
+  DCHECK_EQ(address, AlignedAddress(address, alignment));
+  DCHECK_EQ(0UL, size & (GetPageAllocator()->AllocatePageSize() - 1));
   void* result = nullptr;
   for (int i = 0; i < kAllocationTries; ++i) {
     result =

src/heap/spaces.cc

@@ -710,7 +710,8 @@ MemoryChunk* MemoryAllocator::AllocateChunk(size_t reserve_area_size,
   VirtualMemory reservation;
   Address area_start = nullptr;
   Address area_end = nullptr;
-  void* address_hint = heap->GetRandomMmapAddr();
+  void* address_hint =
+      AlignedAddress(heap->GetRandomMmapAddr(), MemoryChunk::kAlignment);
 
   //
   // MemoryChunk layout:

test/unittests/allocation-unittest.cc

@@ -134,8 +134,8 @@ TEST(AllocationTest, AllocateAndFree) {
   // A large allocation, aligned significantly beyond native granularity.
   const size_t kBigAlignment = 64 * v8::internal::MB;
   void* aligned_mem_addr = v8::internal::AllocatePages(
-      v8::internal::GetRandomMmapAddr(), kAllocationSize, kBigAlignment,
-      PageAllocator::Permission::kReadWrite);
+      AlignedAddress(v8::internal::GetRandomMmapAddr(), kBigAlignment),
+      kAllocationSize, kBigAlignment, PageAllocator::Permission::kReadWrite);
   CHECK_NOT_NULL(aligned_mem_addr);
   CHECK_EQ(aligned_mem_addr, AlignedAddress(aligned_mem_addr, kBigAlignment));
   CHECK(v8::internal::FreePages(aligned_mem_addr, kAllocationSize));