Add guard pages in front of platform allocations

src/platform.h

 // Copyright 2011 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 188 matching lines @@
   static void PrintError(const char* format, ...);
   static void VPrintError(const char* format, va_list args);
 
   // Allocate/Free memory used by JS heap. Pages are readable/writable, but
   // they are not guaranteed to be executable unless 'executable' is true.
   // Returns the address of allocated memory, or NULL if failed.
   static void* Allocate(const size_t requested,
                         size_t* allocated,
                         bool is_executable);
   static void Free(void* address, const size_t size);
+
+  // Assign memory as a guard page so that access will cause an exception.
+  static void Guard(void* address, const size_t size);
+
   // Get the Alignment guaranteed by Allocate().
   static size_t AllocateAlignment();
 
   // Returns an indication of whether a pointer is in a space that
   // has been allocated by Allocate().  This method may conservatively
   // always return false, but giving more accurate information may
   // improve the robustness of the stack dump code in the presence of
   // heap corruption.
   static bool IsOutsideAllocatedSpace(void* pointer);
 
@@ skipping 435 matching lines @@
   Atomic32 active_;
   PlatformData* data_;  // Platform specific data.
   int samples_taken_;  // Counts stack samples taken.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_