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comparison: mfbt/Poison.h
mfbt/Poison.h
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| 1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ | |
| 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ | |
| 3 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 /* | |
| 8 * A poison value that can be used to fill a memory space with | |
| 9 * an address that leads to a safe crash when dereferenced. | |
| 10 */ | |
| 11 | |
| 12 #ifndef mozilla_Poison_h | |
| 13 #define mozilla_Poison_h | |
| 14 | |
| 15 #include "mozilla/Assertions.h" | |
| 16 #include "mozilla/Types.h" | |
| 17 | |
| 18 #include <stdint.h> | |
| 19 | |
| 20 MOZ_BEGIN_EXTERN_C | |
| 21 | |
| 22 extern MFBT_DATA uintptr_t gMozillaPoisonValue; | |
| 23 | |
| 24 /** | |
| 25 * @return the poison value. | |
| 26 */ | |
| 27 inline uintptr_t mozPoisonValue() | |
| 28 { | |
| 29 return gMozillaPoisonValue; | |
| 30 } | |
| 31 | |
| 32 /** | |
| 33 * Overwrite the memory block of aSize bytes at aPtr with the poison value. | |
| 34 * aPtr MUST be aligned at a sizeof(uintptr_t) boundary. | |
| 35 * Only an even number of sizeof(uintptr_t) bytes are overwritten, the last | |
| 36 * few bytes (if any) is not overwritten. | |
| 37 */ | |
| 38 inline void mozWritePoison(void* aPtr, size_t aSize) | |
| 39 { | |
| 40 const uintptr_t POISON = mozPoisonValue(); | |
| 41 char* p = (char*)aPtr; | |
| 42 char* limit = p + aSize; | |
| 43 MOZ_ASSERT((uintptr_t)aPtr % sizeof(uintptr_t) == 0, "bad alignment"); | |
| 44 MOZ_ASSERT(aSize >= sizeof(uintptr_t), "poisoning this object has no effect"); | |
| 45 for (; p < limit; p += sizeof(uintptr_t)) { | |
| 46 *((uintptr_t*)p) = POISON; | |
| 47 } | |
| 48 } | |
| 49 | |
| 50 /** | |
| 51 * Initialize the poison value. | |
| 52 * This should only be called once. | |
| 53 */ | |
| 54 extern MFBT_API void mozPoisonValueInit(); | |
| 55 | |
| 56 /* Values annotated by CrashReporter */ | |
| 57 extern MFBT_DATA uintptr_t gMozillaPoisonBase; | |
| 58 extern MFBT_DATA uintptr_t gMozillaPoisonSize; | |
| 59 | |
| 60 MOZ_END_EXTERN_C | |
| 61 | |
| 62 #endif /* mozilla_Poison_h */ |
