Add guard pages in front of platform allocations

src/platform-win32.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 895 matching lines @@
 
   // For exectutable pages try and randomize the allocation address
   if (prot == PAGE_EXECUTE_READWRITE &&
       msize >= static_cast<size_t>(Page::kPageSize)) {
     address = (V8::RandomPrivate(Isolate::Current()) << kPageSizeBits)
       | kAllocationRandomAddressMin;
     address &= kAllocationRandomAddressMax;
   }
 
   LPVOID mbase = VirtualAlloc(reinterpret_cast<void *>(address),
-                              msize,
+                              msize + Page::kPageSize,

[Vyacheslav Egorov (Chromium), 2011/07/12 23:23:29]

This looks slightly suspicious to me.

MemoryAllocator knows about 64k allocation granularity on Windows and allocates
space for 8 8k Pages per call to OS::Allocate.

Here you basically ask for 8*8k + 8k which will waste 7*8k of VAS which
MemoryAllocator tried to avoid.

[Cris Neckar, 2011/07/14 17:32:28]

Done.

                               MEM_COMMIT | MEM_RESERVE,
                               prot);
   if (mbase == NULL && address != 0)
-    mbase = VirtualAlloc(NULL, msize, MEM_COMMIT | MEM_RESERVE, prot);
+    mbase = VirtualAlloc(NULL,
+                         msize + Page::kPageSize,
+                         MEM_COMMIT | MEM_RESERVE,
+                         prot);
 
   if (mbase == NULL) {
     LOG(ISOLATE, StringEvent("OS::Allocate", "VirtualAlloc failed"));
     return NULL;
   }
 
   ASSERT(IsAligned(reinterpret_cast<size_t>(mbase), OS::AllocateAlignment()));
+  *allocated = msize;
 
-  *allocated = msize;
+  DWORD old_protect;
+  VirtualProtect(mbase, Page::kPageSize, PAGE_READONLY | PAGE_GUARD, &old_protect);
+  mbase = static_cast<BYTE*>(mbase) + Page::kPageSize;
+
   UpdateAllocatedSpaceLimits(mbase, static_cast<int>(msize));
   return mbase;
 }
 
 
 void OS::Free(void* address, const size_t size) {
   // TODO(1240712): VirtualFree has a return value which is ignored here.
-  VirtualFree(address, 0, MEM_RELEASE);
+  VirtualFree(static_cast<BYTE*>(address) - Page::kPageSize, 0, MEM_RELEASE);
   USE(size);
 }
 
 
 #ifdef ENABLE_HEAP_PROTECTION
 
 void OS::Protect(void* address, size_t size) {
   // TODO(1240712): VirtualProtect has a return value which is ignored here.
   DWORD old_protect;
   VirtualProtect(address, size, PAGE_READONLY, &old_protect);
@@ skipping 1082 matching lines @@
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SamplerThread::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal