title BREAK - handle ctrl-break ;***************************************************************************** ; Change Log ; Date | Change ;-----------+----------------------------------------------------------------- ; 11-Aug-85 | Created ; 1-Sep-85 | Rearranged so _clrctl precedes its call (needed in P model) ; 31-Dec-85 | Made special copy for Adagio support. Stripped out most stuff ; | and handle DOS ctrl-break exit ; 1-Jan-86 | Use 1 for control-break and 2 for control-C ; 1-Jan-86 | Cause return to skip over sub instruction (forcing ignore code ; | acceptance) on PC/AT ; 2-Jan-86 | take out m: from include m:dos.mac ;****************************************************************************/ include dos.mac debug=0 subttl Documentation ;***************************************************************************** ; This code uses the standard Lattice interface. The logical device 'm:' ; represents the memory model being used. Supply your own path to dos.mac ; ; This code is intended to allow me to break out of various perverse ; loops in my application code. ; ; * * * W A R N I N G * * * ; ; This code is an extreme *HACK*. It solves my problem. It may not solve ; yours. I make no guarantees. Use at your own risk! ; ; Restrictions ; ; Failure to clear the handler before exiting the program will lead to ; various bizarre behavior. Calling the initialization more than once ; will confuse the world beyond practical recovery. ; ; Abstract ; ; A procedure is called to establish the existence of the control-break ; handler (interrupt 1BH). If a control-break is taken during program ; the flag _CBREAK is set to true ; ; This code is to be linked into the user's application. ; ; This code also sets up a handler for the DOS ctrl-brk exit; this is called ; if DOS sees a C-C character come by. ; ; * * * B E W A R E * * * ; ; This code is delicate and high-risk. It works well enough for my one ; application. I may have missed all sorts of bizarre DOS or BIOS hacks. ; ; It is not guaranteed to be bug-free. The user assumes all risk in using ; it. This is code that should be used only if you understand enough of ; DOS/BIOS hacking to be sure it will work for you. ; ; subttl Interface specifications ;----------------------------------------------------------------------------- ; extern void _setctl(); ; ; Effects: ; Establishes a Ctrl-brk abort handler ; ; Limitations: ; May only be called once; subsequent calls may damage universe ; ;----------------------------------------------------------------------------- ; extern void _clrctl(); ; ; Effects: ; Resets the Ctrl-brk abort handler ; ; Limitations: ; Should be called only if _setctl() has been called. However, if ; _setctl has not already been called, nothing will happen. ; ;***************************************************************************** subttl Working storage extrn _CBREAK:word ; This storage is in the data segment ; public _CBREAK DSEG even ;_CBREAK dw 0 OLD_BIOS label DWORD ; we store former 1BH vector here OLD_BIP DW 0 ; 0, not ? OLD_BCS DW 0 ; 0, not ? OLD_DOS label DWORD ; we store former 23H vector here OLD_DIP DW 0 OLD_DCS dw 0 ENDDS subttl Vector locations VECTORS SEGMENT AT 0H ORG 1BH*4 ; BIOS ctrl-brk interrupt vector CTLBRK LABEL DWORD CTLBRK_IP DW ? ; IP of BIOS control-break vector CTLBRK_CS DW ? ; CS of BIOS control-break vector ORG 23H*4 ; DOS ctrl-brk interrupt vector DOSCBRK LABEL DWORD DOSC_IP DW ? DOSC_CS DW ? VECTORS ENDS subttl Code segment storage ; ; This is in the code segment because I don't know how to make it addressible ; in the data segment ; PSEG subttl CTLSEEN - CTRL-BREAK handler ;----------------------------------------------------------------------------- ; ctlseen ; Inputs: ; None; called as interrupt routine via interrupt 1BH ; ; Result: ; AL=0FFH ; ; Effects: ; sets _CBREAK to true. ;----------------------------------------------------------------------------- CTLSEEN PROC FAR if debug int 3 endif push ax push ds mov ax,seg _CBREAK mov ds,ax mov ds:_CBREAK,1 pop ds pop ax push es mov AX,0F000H ; from the ROM, mov ES,AX ; we want pc ID mov AH,ES:0FFFEH ; The Peter Norton Programmer's Guide to the ; IBM PC, page 60 cmp AH,0FCH ; PC/AT? jnz no if debug int 3 ; WARNING! If you have this debug trap ; enabled, and continue from it, the ; ctrl-key-up transition is lost (because ; the key went up to talk to the debugger) ; this confuses the world; you will have to ; hit the control-key once to get the ; world resynchronized. endif ; We increment the return address by 2 ; ; +-------------------+ ; SS | (ES) | ES:0[BP] ; +-------------------+ ; | (BP) | ES:2[BP] ; +-------------------+ ; | IP | ES:4[BP] ; +-------------------+ ; | CS | ES:6[BP] ; +-------------------+ mov AX,SS mov ES,AX push BP mov BP,SP inc WORD PTR ES:4[BP] inc WORD PTR ES:4[BP] pop BP no: mov AX,-1 ; "ignore" character ; PC/XT ref page A-31 lines 2090-2091, page A-33 ; lines 2217-2219 ; PC/AT ref page 5-118 loc 2AE..285 indicates this ; has no effect for the /AT, which is why we did ; the above hack pop ES iret ;return CTLSEEN ENDP CTLC PROC FAR ; Control-C handler push ax push ds mov ax,seg _CBREAK mov ds,ax mov ds:_CBREAK,2 pop ds pop ax iret ;return CTLC ENDP subttl _clrctl - Clear CTL-BRK vector ;----------------------------------------------------------------------------- ; extern void _clrctl(); ; ; Resets the ctrl-break interrupt vector ;----------------------------------------------------------------------------- PUBLIC _clrctl IF LPROG _clrctl PROC FAR ELSE _clrctl PROC NEAR ENDIF ; OldES := ES; push ES ; save old ES push AX ; save old AX push BX if debug int 3 mov AH,62H int 21H ; get program segment prefix mov PSP,BX ; save it endif ; ES := Segment(&Vectors); mov AX,VECTORS mov ES,AX ASSUME ES:VECTORS ; Disable_Interrupts(); CLI ; turn off interrupts ; if(OLD_BIOS == 0) goto NoVectorStored mov AX,WORD PTR OLD_BIOS cmp AX,0 ; is it zero? je NoBIOSStored ; CTLBRK.IP := OLD_BIOS.IP mov WORD PTR CTLBRK,AX ; CTLBRK.CS := OLD_BIOS.CS mov AX,WORD PTR OLD_BIOS[2] mov WORD PTR CTLBRK[2],AX NoBIOSStored: mov AX,WORD PTR OLD_DOS cmp AX,0 ; initialized? je NoDOSStored ; no, no dos vector ; DOSCBRK.IP = OLD_DOS.IP mov WORD PTR DOSCBRK,AX ; DOSCBRK.CS := OLD_DOS.CS mov AX,WORD PTR OLD_DOS[2] mov WORD PTR DOSCBRK[2],AX NoDOSStored: ; Enable_interrupts(); STI ; allow interrupts ; ES := OldES; pop BX pop AX pop ES ret ; return to caller PSP: DW ? _clrctl ENDP subttl _setctl - Set CTL-BRK vector ;----------------------------------------------------------------------------- ; extern void _setctl() ;----------------------------------------------------------------------------- PUBLIC _setctl IF LPROG _setctl PROC FAR ELSE _setctl PROC NEAR ; set CTL-BRK interrupt ENDIF push BP ; C prolog mov BP,SP ; ... if debug int 3 endif ASSUME ES:VECTORS ; OldES := ES; push ES ; save old ES push AX ; save old AX ; ES := Segment(&Vectors); mov AX,VECTORS mov ES,AX ; Disable_Interrupts(); CLI ; turn off interrupts ; OLD_BIOS.IP := CTLBRK.IP mov AX,WORD PTR CTLBRK mov WORD PTR OLD_BIOS,AX ; OLD_BIOS.CS := CTLBRK.CS mov AX,WORD PTR CTLBRK[2] mov WORD PTR OLD_BIOS[2],AX ; CTLBRK := &CTLSEEN mov CTLBRK_IP,OFFSET CTLSEEN mov CTLBRK_CS,CS ; OLD_DOS.IP := DOSCBRK.IP mov AX,WORD PTR DOSCBRK mov WORD PTR OLD_DOS,AX ; OLD_DOS.CS := DOSCBRK.CS mov AX,WORD PTR DOSCBRK[2] mov WORD PTR OLD_DOS[2],AX ; DOSCBRK := &CTLC mov DOSC_IP,OFFSET CTLC mov DOSC_CS,CS ; Enable_interrupts(); STI ; allow interrupts ; ES := OldES; pop AX pop ES ; return; pop BP ; C epilog ret ; return to caller _setctl ENDP ENDPS END