asynch.asm

开放源码的编译器open watcom 1.6.0版的源代码

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                NAME    myhook
                EXTRN   _OldHook :BYTE
                EXTRN   _AsynchStop : BYTE
DGROUP          GROUP   CONST

CONST           SEGMENT WORD PUBLIC  'DATA'
                ORG     00000000H
ds_seg          LABEL   BYTE
CONST           ENDS


myhook_TEXT     SEGMENT BYTE PUBLIC  'CODE'
                ASSUME  CS:myhook_TEXT ,DS:DGROUP,SS:NOTHING

                PUBLIC  AsynchHook_
AsynchHook_:    push    ds                          ; save the regs
                push    dx
                push    es
                mov     dx,seg ds_seg               ; load ds
                mov     ds,dx
                cmp     ax,0063H                    ; is it asyc-stop
                je      short handle_asyc
                mov     dx,word ptr _OldHook        ; is someone else hooked
                test    dx,dx                       ; i.e. OldHook != NULL
                je      short return
                mov     dx,word ptr _OldHook+2H
                test    dx,dx
                je      short return
                pop     es                          ; restore all but ds
                pop     dx
                call    dword ptr _OldHook          ; call OldHook
                pop     ds                          ; restore ds and return
                retf
handle_asyc:    mov     _AsynchStop,1               ; enter debugger
return:         pop     es
                pop     dx
                pop     ds
                retf

myhook_TEXT     ENDS

                END