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/* -*- 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/StandardInteger.h"
#include "mozilla/Types.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_ */
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