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page ,132 title chkstk - C stack checking routine;***;chkstk.asm - C stack checking routine;; Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.;;Purpose:; Provides support for automatic stack checking in C procedures; when stack checking is enabled.;;Revision History:; 04-21-87 SKS Added conditional assembly switch for STKHQQ = 0; 07-23-87 MAG [1] Added run-time CS:IP error processing for QC; 08-17-87 JLS [2] Remove all references to DGROUP; 08-25-87 JLS [3] Shift include files; 11-13-87 SKS OS/2 Reentrant version, add thread ID check; 11-18-87 SKS Make STKHQQ an array (oops!); 12-14-87 SKS add .286p to allow PUSH immediate value; 02-19-88 SKS Change minimum bottom limit to STACKSLOP, not 0; 06-01-88 PHG Merge DLL and normal versions; 09-21-88 WAJ initial 386 version; 10-18-88 JCR Chkstk was trashing bx... not good on 386; 06-06-89 JCR 386 mthread support; 06-20-89 JCR 386: Removed _LOAD_DGROUP code; 04-06-90 GJF Fixed the copyright.; 06-21-90 GJF Rewritten to probe pages; 10-15-90 GJF Restored _end and STKHQQ.; 03-19-91 GJF Revised to preserve all registers except eax. Note; this is _rchkstk functionality so there is no longer; a separate _rchkstk routine.; 08-01-91 GJF Got rid of _end and STKHQQ, except for Cruiser; (probably not needed for Cruiser either) [_WIN32_].; 09-27-91 JCR Merged Stevewo' changes from NT tree; 09-06-94 CFW Nuke Cruiser.; 12-03-94 SKS Remove include of obsolete file msdos.inc; 12-13-94 GJF Better version from Intel (old jmp eax method of; returning is too expensive on P6).; 09-11-98 GJF Fixed handling of very small frames.; 12-10-99 GB Changed both _chkstk and _alloca_probe to procedure;;*******************************************************************************
.xlist include cruntime.inc.list
; size of a page of memory
_PAGESIZE_ equ 1000h
CODESEG
page;***;_chkstk - check stack upon procedure entry;;Purpose:; Provide stack checking on procedure entry. Method is to simply probe; each page of memory required for the stack in descending order. This; causes the necessary pages of memory to be allocated via the guard; page scheme, if possible. In the event of failure, the OS raises the; _XCPT_UNABLE_TO_GROW_STACK exception.;; NOTE: Currently, the (EAX < _PAGESIZE_) code path falls through; to the "lastpage" label of the (EAX >= _PAGESIZE_) code path. This; is small; a minor speed optimization would be to special case; this up top. This would avoid the painful save/restore of; ecx and would shorten the code path by 4-6 instructions.;;Entry:; EAX = size of local frame;;Exit:; ESP = new stackframe, if successful;;Uses:; EAX;;Exceptions:; _XCPT_GUARD_PAGE_VIOLATION - May be raised on a page probe. NEVER TRAP; THIS!!!! It is used by the OS to grow the; stack on demand.; _XCPT_UNABLE_TO_GROW_STACK - The stack cannot be grown. More precisely,; the attempt by the OS memory manager to; allocate another guard page in response; to a _XCPT_GUARD_PAGE_VIOLATION has; failed.;;*******************************************************************************
public _alloca_probe
_chkstk proc
_alloca_probe = _chkstk
cmp eax, _PAGESIZE_ ; more than one page? jae short probesetup ; yes, go setup probe loop ; no neg eax ; compute new stack pointer in eax add eax,esp add eax,4 test dword ptr [eax],eax ; probe it xchg eax,esp mov eax,dword ptr [eax] push eax ret
probesetup: push ecx ; save ecx lea ecx,[esp] + 8 ; compute new stack pointer in ecx ; correct for return address and ; saved ecx
probepages: sub ecx,_PAGESIZE_ ; yes, move down a page sub eax,_PAGESIZE_ ; adjust request and...
test dword ptr [ecx],eax ; ...probe it
cmp eax,_PAGESIZE_ ; more than one page requested? jae short probepages ; no
lastpage: sub ecx,eax ; move stack down by eax mov eax,esp ; save current tos and do a... test dword ptr [ecx],eax ; ...probe in case a page was crossed
mov esp,ecx ; set the new stack pointer mov ecx,dword ptr [eax] ; recover ecx mov eax,dword ptr [eax + 4] ; recover return address push eax ; prepare return address ; ...probe in case a page was crossed ret_chkstk endp
end
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