185 lines
7.2 KiB
C
185 lines
7.2 KiB
C
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/*++
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Copyright (c) 2001 Microsoft Corporation
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Module Name:
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alloca.h
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Abstract:
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This module implements a safe stack-based allocator with fallback to the heap.
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Author:
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Jonathan Schwartz (JSchwart) 16-Mar-2001
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Revision History:
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--*/
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#ifndef _SAFEALLOCA_H_
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#define _SAFEALLOCA_H_
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#ifdef __cplusplus
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extern "C"
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{
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#endif // __cplusplus
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#include <align.h> // ALIGN_WORST
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//
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// Type definitions
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//
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typedef ULONG SAFEALLOCA_HEADER;
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typedef PVOID (APIENTRY *SAFEALLOC_ALLOC_PROC)(
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SIZE_T Size
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);
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typedef VOID (APIENTRY *SAFEALLOC_FREE_PROC)(
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PVOID BaseAddress
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);
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//
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// Constant definitions
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//
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#define SAFEALLOCA_STACK_HEADER ((SAFEALLOCA_HEADER) 0x6b637453) /* "Stck" */
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#define SAFEALLOCA_HEAP_HEADER ((SAFEALLOCA_HEADER) 0x70616548) /* "Heap" */
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#define SAFEALLOCA_USE_DEFAULT 0xdeadbeef
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//
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// We'll be adding ALIGN_WORST bytes to the allocation size to add room for
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// the SAFEALLOCA_HEADER -- make sure we'll always have enough space.
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//
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C_ASSERT(sizeof(SAFEALLOCA_HEADER) <= ALIGN_WORST);
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//
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// Per-DLL SafeAlloca globals
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//
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extern SIZE_T g_ulMaxStackAllocSize;
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extern SIZE_T g_ulAdditionalProbeSize;
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extern SAFEALLOC_ALLOC_PROC g_pfnAllocate;
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extern SAFEALLOC_FREE_PROC g_pfnFree;
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//
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// Functions defined in alloca.lib
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//
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VOID
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SafeAllocaInitialize(
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IN OPTIONAL SIZE_T ulMaxStackAllocSize,
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IN OPTIONAL SIZE_T ulAdditionalProbeSize,
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IN OPTIONAL SAFEALLOC_ALLOC_PROC pfnAllocate,
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IN OPTIONAL SAFEALLOC_FREE_PROC pfnFree
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);
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BOOL
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VerifyStackAvailable(
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SIZE_T Size
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);
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//
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// Usage:
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//
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// VOID
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// SafeAllocaAllocate(
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// PVOID PtrVar,
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// SIZE_T BlockSize
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// );
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//
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// (PtrVar == NULL) on failure
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//
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#define SafeAllocaAllocate(PtrVar, BlockSize) \
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\
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{ \
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PVOID *ppvAvoidCast = (PVOID *) &(PtrVar); \
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\
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(PtrVar) = NULL; \
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\
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/* Make sure block is below the threshhold and that the probe won't overflow */ \
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\
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if ((BlockSize) <= g_ulMaxStackAllocSize \
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&& \
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((BlockSize) + g_ulAdditionalProbeSize >= (BlockSize))) \
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{ \
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if (VerifyStackAvailable((BlockSize) \
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+ g_ulAdditionalProbeSize \
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+ ALIGN_WORST)) \
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{ \
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/* \
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* Don't need to wrap with try-except since we just probed \
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*/ \
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\
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*ppvAvoidCast = _alloca((BlockSize) + ALIGN_WORST); \
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} \
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\
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if ((PtrVar) != NULL) \
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{ \
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*((SAFEALLOCA_HEADER *) (PtrVar)) = SAFEALLOCA_STACK_HEADER; \
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*ppvAvoidCast = ((LPBYTE) (PtrVar) + ALIGN_WORST); \
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} \
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} \
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\
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/* \
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* Stack allocation failed -- try the heap \
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*/ \
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\
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if ((PtrVar) == NULL) \
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{ \
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*ppvAvoidCast = g_pfnAllocate((BlockSize) + ALIGN_WORST); \
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\
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if ((PtrVar) != NULL) \
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{ \
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*((SAFEALLOCA_HEADER *) (PtrVar)) = SAFEALLOCA_HEAP_HEADER; \
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*ppvAvoidCast = ((LPBYTE) (PtrVar) + ALIGN_WORST); \
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} \
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} \
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}
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//
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// Usage:
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//
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// VOID
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// SafeAllocaFree(
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// PVOID PtrVar,
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// );
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//
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#define SafeAllocaFree(PtrVar) \
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\
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if (PtrVar != NULL) \
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{ \
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SAFEALLOCA_HEADER *Tag = (SAFEALLOCA_HEADER *) ((LPBYTE) (PtrVar) \
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- ALIGN_WORST); \
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\
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if (*(SAFEALLOCA_HEADER *) (Tag) == SAFEALLOCA_HEAP_HEADER) \
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{ \
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g_pfnFree(Tag); \
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} \
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else \
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{ \
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ASSERT(*(SAFEALLOCA_HEADER *) (Tag) == SAFEALLOCA_STACK_HEADER); \
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} \
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}
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#ifdef __cplusplus
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}
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#endif // __cplusplus
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#endif // _SAFEALLOCA_H_
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