1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/mfbt/Poison.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,62 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set ts=8 sts=2 et sw=2 tw=80: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +/*
1.11 + * A poison value that can be used to fill a memory space with
1.12 + * an address that leads to a safe crash when dereferenced.
1.13 + */
1.14 +
1.15 +#ifndef mozilla_Poison_h
1.16 +#define mozilla_Poison_h
1.17 +
1.18 +#include "mozilla/Assertions.h"
1.19 +#include "mozilla/Types.h"
1.20 +
1.21 +#include <stdint.h>
1.22 +
1.23 +MOZ_BEGIN_EXTERN_C
1.24 +
1.25 +extern MFBT_DATA uintptr_t gMozillaPoisonValue;
1.26 +
1.27 +/**
1.28 + * @return the poison value.
1.29 + */
1.30 +inline uintptr_t mozPoisonValue()
1.31 +{
1.32 + return gMozillaPoisonValue;
1.33 +}
1.34 +
1.35 +/**
1.36 + * Overwrite the memory block of aSize bytes at aPtr with the poison value.
1.37 + * aPtr MUST be aligned at a sizeof(uintptr_t) boundary.
1.38 + * Only an even number of sizeof(uintptr_t) bytes are overwritten, the last
1.39 + * few bytes (if any) is not overwritten.
1.40 + */
1.41 +inline void mozWritePoison(void* aPtr, size_t aSize)
1.42 +{
1.43 + const uintptr_t POISON = mozPoisonValue();
1.44 + char* p = (char*)aPtr;
1.45 + char* limit = p + aSize;
1.46 + MOZ_ASSERT((uintptr_t)aPtr % sizeof(uintptr_t) == 0, "bad alignment");
1.47 + MOZ_ASSERT(aSize >= sizeof(uintptr_t), "poisoning this object has no effect");
1.48 + for (; p < limit; p += sizeof(uintptr_t)) {
1.49 + *((uintptr_t*)p) = POISON;
1.50 + }
1.51 +}
1.52 +
1.53 +/**
1.54 + * Initialize the poison value.
1.55 + * This should only be called once.
1.56 + */
1.57 +extern MFBT_API void mozPoisonValueInit();
1.58 +
1.59 +/* Values annotated by CrashReporter */
1.60 +extern MFBT_DATA uintptr_t gMozillaPoisonBase;
1.61 +extern MFBT_DATA uintptr_t gMozillaPoisonSize;
1.62 +
1.63 +MOZ_END_EXTERN_C
1.64 +
1.65 +#endif /* mozilla_Poison_h */
