| /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
| /* vim: set ts=8 sts=2 et sw=2 tw=80: */ |
| /* This Source Code Form is subject to the terms of the Mozilla Public |
| * License, v. 2.0. If a copy of the MPL was not distributed with this |
| * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| |
| /* |
| * A poison value that can be used to fill a memory space with |
| * an address that leads to a safe crash when dereferenced. |
| */ |
| |
| #ifndef mozilla_Poison_h |
| #define mozilla_Poison_h |
| |
| #include "mozilla/Assertions.h" |
| #include "mozilla/Types.h" |
| |
| #include <stdint.h> |
| |
| MOZ_BEGIN_EXTERN_C |
| |
| extern MFBT_DATA uintptr_t gMozillaPoisonValue; |
| |
| /** |
| * @return the poison value. |
| */ |
| inline uintptr_t mozPoisonValue() |
| { |
| return gMozillaPoisonValue; |
| } |
| |
| /** |
| * Overwrite the memory block of aSize bytes at aPtr with the poison value. |
| * aPtr MUST be aligned at a sizeof(uintptr_t) boundary. |
| * Only an even number of sizeof(uintptr_t) bytes are overwritten, the last |
| * few bytes (if any) is not overwritten. |
| */ |
| inline void mozWritePoison(void* aPtr, size_t aSize) |
| { |
| const uintptr_t POISON = mozPoisonValue(); |
| char* p = (char*)aPtr; |
| char* limit = p + aSize; |
| MOZ_ASSERT((uintptr_t)aPtr % sizeof(uintptr_t) == 0, "bad alignment"); |
| MOZ_ASSERT(aSize >= sizeof(uintptr_t), "poisoning this object has no effect"); |
| for (; p < limit; p += sizeof(uintptr_t)) { |
| *((uintptr_t*)p) = POISON; |
| } |
| } |
| |
| /** |
| * Initialize the poison value. |
| * This should only be called once. |
| */ |
| extern MFBT_API void mozPoisonValueInit(); |
| |
| /* Values annotated by CrashReporter */ |
| extern MFBT_DATA uintptr_t gMozillaPoisonBase; |
| extern MFBT_DATA uintptr_t gMozillaPoisonSize; |
| |
| MOZ_END_EXTERN_C |
| |
| #endif /* mozilla_Poison_h */ |
