[win32] Improve random mmap address generation on 64-bit.

src/base/platform/platform-win32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Platform-specific code for Win32.
 
 // Secure API functions are not available using MinGW with msvcrt.dll
 // on Windows XP. Make sure MINGW_HAS_SECURE_API is not defined to
 // disable definition of secure API functions in standard headers that
 // would conflict with our own implementation.
@@ skipping 715 matching lines @@
 }
 
 
 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
   // Use a multiple of 64k to prevent committing unused memory.
   // Note: This does not guarantee RWX regions will be within the
   // range kAllocationRandomAddressMin to kAllocationRandomAddressMax
 #ifdef V8_HOST_ARCH_64_BIT
-  static const intptr_t kAllocationRandomAddressMin = 0x0000000080000000;
-  static const intptr_t kAllocationRandomAddressMax = 0x000003FFFFFF0000;
+  static const uintptr_t kAllocationRandomAddressMin = 0x0000000080000000;
+  static const uintptr_t kAllocationRandomAddressMax = 0x000003FFFFFF0000;
 #else
-  static const intptr_t kAllocationRandomAddressMin = 0x04000000;
-  static const intptr_t kAllocationRandomAddressMax = 0x3FFF0000;
+  static const uintptr_t kAllocationRandomAddressMin = 0x04000000;
+  static const uintptr_t kAllocationRandomAddressMax = 0x3FFF0000;
 #endif
-  uintptr_t address =
-      (platform_random_number_generator.Pointer()->NextInt() << kPageSizeBits) |
-      kAllocationRandomAddressMin;
+  uintptr_t address;
+  platform_random_number_generator.Pointer()->NextBytes(&address,
+                                                        sizeof(address));
+  address <<= kPageSizeBits;
+  address += kAllocationRandomAddressMin;
   address &= kAllocationRandomAddressMax;
   return reinterpret_cast<void *>(address);
 }
 
 
 static void* RandomizedVirtualAlloc(size_t size, int action, int protection) {
   LPVOID base = NULL;
 
   if (protection == PAGE_EXECUTE_READWRITE || protection == PAGE_NOACCESS) {
     // For exectutable pages try and randomize the allocation address
@@ skipping 626 matching lines @@
   DCHECK(result);
 }
 
 
 
 void Thread::YieldCPU() {
   Sleep(0);
 }
 
 } }  // namespace v8::base