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Tricks of the Windows Gam…ming Gurus (2nd Edition)
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Disc2.iso
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vc98
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crt
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chkstk.asm
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Assembly Source File
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1998-06-17
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4KB
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100 lines
page ,132
title chkstk - C stack checking routine
;***
;chkstk.asm - C stack checking routine
;
; Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.
;
;Purpose:
; Provides support for automatic stack checking in C procedures
; when stack checking is enabled.
;
;*******************************************************************************
.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.
;
;*******************************************************************************
labelP _alloca_probe, PUBLIC
labelP _chkstk, PUBLIC
push ecx ; save ecx
cmp eax,_PAGESIZE_ ; more than one page requested?
lea ecx,[esp] + 8 ; compute new stack pointer in ecx
; correct for return address and
; saved ecx
jb short lastpage ; no
;------------
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
end