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127 lines
3.9 KiB
127 lines
3.9 KiB
#define DOWNLEVEL
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/***
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*resetstk.c - Recover from Stack overflow.
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*
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* Copyright (c) 1989-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* Defines the _resetstkoflw() function.
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*
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*Revision History:
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* 12-10-99 GB Module Created
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* 04-17-01 PML Enable for Win9x, return success code (vs7#239962)
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* 06-04-01 PML Do nothing if guard page not missing, don't shrink
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* committed space (vs7#264306)
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* 04-25-02 PML Don't set guard page below pMinGuard (vs7#530044)
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*
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*******************************************************************************/
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#include <stdlib.h>
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#include <malloc.h>
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#include <windows.h>
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#define MIN_STACK_REQ_WIN9X 17
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#define MIN_STACK_REQ_WINNT 2
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/***
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* void _resetstkoflw(void) - Recovers from Stack Overflow
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*
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* Purpose:
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* Sets the guard page to its position before the stack overflow.
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*
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* Exit:
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* Returns nonzero on success, zero on failure
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*
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*******************************************************************************/
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#ifdef DOWNLEVEL
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#define _resetstkoflw _resetstkoflw_downlevel
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#endif
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int __cdecl _resetstkoflw(void)
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{
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LPBYTE pStack, pGuard, pStackBase, pMaxGuard, pMinGuard;
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MEMORY_BASIC_INFORMATION mbi;
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SYSTEM_INFO si;
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DWORD PageSize;
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DWORD flNewProtect;
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DWORD flOldProtect;
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// Use _alloca() to get the current stack pointer
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pStack = _alloca(1);
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// Find the base of the stack.
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if (VirtualQuery(pStack, &mbi, sizeof mbi) == 0)
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return 0;
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pStackBase = mbi.AllocationBase;
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// Find the page just below where the stack pointer currently points.
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// This is the highest potential guard page.
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GetSystemInfo(&si);
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PageSize = si.dwPageSize;
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pMaxGuard = (LPBYTE) (((DWORD_PTR)pStack & ~(DWORD_PTR)(PageSize - 1))
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- PageSize);
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// If the potential guard page is too close to the start of the stack
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// region, abandon the reset effort for lack of space. Win9x has a
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// larger reserved stack requirement.
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pMinGuard = pStackBase + ((_osplatform == VER_PLATFORM_WIN32_WINDOWS)
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? MIN_STACK_REQ_WIN9X
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: MIN_STACK_REQ_WINNT) * PageSize;
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if (pMaxGuard < pMinGuard)
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return 0;
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// On a non-Win9x system, do nothing if a guard page is already present,
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// else set up the guard page to the bottom of the committed range,
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// allowing for the reserved stack requirement.
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// For Win9x, just set guard page below the current stack page.
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if (_osplatform != VER_PLATFORM_WIN32_WINDOWS) {
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// Find first block of committed memory in the stack region
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pGuard = pStackBase;
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do {
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if (VirtualQuery(pGuard, &mbi, sizeof mbi) == 0)
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return 0;
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pGuard = pGuard + mbi.RegionSize;
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} while ((mbi.State & MEM_COMMIT) == 0);
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pGuard = mbi.BaseAddress;
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// If first committed block is already marked as a guard page,
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// there is nothing that needs to be done, so return success.
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if (mbi.Protect & PAGE_GUARD)
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return 1;
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// Fail if the first committed block is above the highest potential
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// guard page. Should never happen.
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if (pMaxGuard < pGuard)
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return 0;
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// Make sure to leave enough room so the next overflow will have
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// the proper reserved stack requirement available.
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if (pGuard < pMinGuard)
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pGuard = pMinGuard;
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VirtualAlloc(pGuard, PageSize, MEM_COMMIT, PAGE_READWRITE);
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}
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else {
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pGuard = pMaxGuard;
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}
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// Enable the new guard page.
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flNewProtect = _osplatform == VER_PLATFORM_WIN32_WINDOWS
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? PAGE_NOACCESS
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: PAGE_READWRITE | PAGE_GUARD;
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return VirtualProtect(pGuard, PageSize, flNewProtect, &flOldProtect);
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}
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