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/. */
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.
12 #ifndef mozilla_Poison_h
13 #define mozilla_Poison_h
15 #include "mozilla/Assertions.h"
16 #include "mozilla/Types.h"
22 extern MFBT_DATA
uintptr_t gMozillaPoisonValue
;
25 * @return the poison value.
27 inline uintptr_t mozPoisonValue()
29 return gMozillaPoisonValue
;
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.
38 inline void mozWritePoison(void* aPtr
, size_t aSize
)
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
;
51 * Initialize the poison value.
52 * This should only be called once.
54 extern MFBT_API
void mozPoisonValueInit();
56 /* Values annotated by CrashReporter */
57 extern MFBT_DATA
uintptr_t gMozillaPoisonBase
;
58 extern MFBT_DATA
uintptr_t gMozillaPoisonSize
;
62 #endif /* mozilla_Poison_h */