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Assembly Source File | 1980-04-10 | 44.4 KB | 1,494 lines

;============================================================================== ; TSRDEMO2.ASM ; Thomas Brandenborg ; 87.02.11 ; ; Sample demonstration of a safe approach for writing TSR programmes. ; ;------------------------------------------------------------------------------ ; Copyright 1987 by Thomas Brandenborg. All Rights Reserved ; Written for uploading to Compuserve Forums by ; ; Thomas Brandenborg ; Lundbyesgade 11 ; DK-8000 Aarhus C ; DENMARK ; ; This code is intended as a reference to users on Compuserve Forums ; on how to write Terminate-And-Stay resident programmes for Personal ; Cumputers running under DOS versions 2.00 and newer. ; ; The code is not part of any proprietary product, but is rather a ; demonstration of such techniques that may be used to write safe TSR ; programmes. ; ; All or part of it may, however, be used in other software products ; or otherwise distributed assuming the copyright holders Name & Address ; as listed above are included clearly and visibly in the documentation ; for such product. ; ; The copyright holder offers no warranty with this code whatsoever, ; including its fitness for any particular purpose. Neither shall he ; be liable for damages of any kind that may arise from its use. ; ; ; IF YOU THINK THIS CODE IS USEFUL: ; ; If you think this code has had some value to you, and in particular ; if you consider using all or parts of it in your own product, you ; may want to consider a smaller or larger donation to the author ; (Name & Address above) who spend his late night hours putting ; it together. ; ; As to the size of a such donation this is entirely up to your own ; judgement. It is suggested that you simply consider the value this ; code has had to you, the time you saved not having to write it your ; self... that should help you determine the right amount. ; ; Please notice that such donations are an entirely voluntary contribution. ; This holds true whatever your purpose is for using this code, and whatever ; the type of product and distribution you work with. The author has nothing ; against commercial software distribution and does not have any reason ; to restrict developers of commercial products in their use of this code. ;------------------------------------------------------------------------------ ; COMPILING: masm tsrdemo2; ; LINKING: link tsrdemo2; ; exe2bin tsrdemo2 tsrdemo2.com ;------------------------------------------------------------------------------ ; Revisions ; Brandenborg 87.02.14 Added copyright notice & checked comments ; Brandenborg 87.02.17 Added full AX value in Set Ext Err call ; Brandenborg 87.02.25 Went through to optimize things ; Brandenborg 87.02.28 Added auto INT28 invocation in INT16 handler ; Brandenborg 87.03.01 Added INT21 filter for recursion onto console stack ; Brandenborg 87.03.02 Final cleanup of comments etc. ;============================================================================== ;============================================================================== ; DEFINE BIOS DATA SEGMENT OFFSETS ;============================================================================== BiosData segment at 40h org 17h KbFlag label byte ;current shift status bits org 18h KbFlag1 label byte ;current key status of toggle keys BiosData ends ;============================================================================== ; DEFINE OFFSETS WITHIN BIOS EXTRA DATA SEGMENT ;============================================================================== BiosXX segment at 50h org 0 StatusByte label byte ;PrtSc status BiosXX ends ErrPrtSc equ -1 ;err during last PrtSc InPrtSc equ 1 ;PrtSc in progress ;============================================================================== ; DEFINE OFFSETS WITHIN OUR PSP ;============================================================================== Cseg segment byte public org 2 TopSeg label word ;last seg in alloc block org 2ch EnvSeg label word ;seg of our environment copy Cseg ends ;============================================================================== ; DOS COM-FILE ENTRY POINT ;============================================================================== Cseg segment public byte assume cs:Cseg, ds:nothing, es:nothing, ss:nothing org 100h ComEntry: jmp Init ;JMP to init at bottom of seg ;============================================================================== ; IDENTIFICATION CODES FOR THIS TSR (MUST BE UNIQUE FOR EACH CO-EXISTING TSR) ; HIGH BYTE OF GetId MUST NOT MATCH ANY AH REQUEST CODES FOR INT16H. ;============================================================================== GetId equ 'tc' ;INT16h AX val to get MyId MyId equ 'TC' ;ID of this TSR ;============================================================================== ; FLAGS AND PTRS FOR RESIDENT HANDLING ;============================================================================== TsrMode db 0 ;bits for various modes InInt08 equ 1 SHL 0 ;timer0 tick handler InInt09 equ 1 SHL 1 ;keyboard handler InInt13 equ 1 SHL 2 ;BIOS disk I/O InInt28 equ 1 SHL 3 ;INT28 handler In28Call equ 1 SHL 4 ;we have issued INT28 InPopup equ 1 SHL 5 ;popup routine activated NewDos equ 1 SHL 6 ;DOS 2.x in use InDosClr equ 1 SHL 7 ;InDos=0 at popup time KeyMode db 0 ;bits for hotkey status HotIsShift equ 1 SHL 0 ;hotkey is shift state InHotMatch equ 1 SHL 1 ;so far keys match hotkey seq HotKeyOn equ 1 SHL 2 ;full hotkey pressed InDosPtr label dword ;seg:off of InDos flag InDosOff dw 0 InDosSeg dw 0 CritErrPtr label dword ;seg:off of CritErr flag CritErrOff dw 0 CritErrSeg dw 0 ;============================================================================== ; DATA FOR INT09H HANDLER TO CHECK FOR HOTKEY COMBINATION ;============================================================================== ; ------------ EQU'S FOR BIT SHIFTS WITHIN KEYBOARD FLAGS InsState equ 80h CapsState equ 40h NumState equ 20h ScrollState equ 10h AltShift equ 08h CtlShift equ 04h LeftShift equ 02h RightShift equ 01h InsShift equ 80h CapsShift equ 40h NumShift equ 20h ScrollShift equ 10h HoldState equ 08h ; ------------ SCAN CODES FOR VARIOUS SHIFT KEYS LeftDown equ 42 ;scan code of left shift key LeftUp equ LeftDown OR 80h RightDown equ 54 ;scan code of right shift key RightUp equ RightDown OR 80h AltDown equ 56 ;scan code of alt key AltUp equ AltDown OR 80h CtlDown equ 29 ;scan code of ctrl key CtlUp equ CtlDown OR 80h ; ------------ MISC KEYBOARD DATA KbData equ 60h ;keyboard data input ;============================================================================== ; TO USE A SHIFT KEY COMBINATION AS HOT KEY: ; - SET THE FLAG HotIsShift IN KeyMode ; - DEFINE THE SHIFT STATUS BITS IN THE VARIABLE HotKeyShift ; ; TO USE A SERIES OF SCAN CODES AS HOT KEY: ; CLEAR THE FLAG HotIsShift IN KeyMode ; - INSERT THE MAKE AND BREAK SCAN CODES IN THE HotKeySeq STRING ; NOTE: WITH THIS DEMO IMPLEMENTATION YOU SHOULD NOT USE A HOT KEY ; SEQUENCE WHICH PRODUCES A KEY IN THE BIOS KEYBOARD QUEUE, ; SINCE THE KEY IS NOT REMOVED BEFORE CALLING THE POPUP ROUTINE. ; ; NOTE: HOTKEY TYPE AND CONTENTS OF HOTKEY VARIABLES MAY BE CHANGED AT RUN TIME ;============================================================================== HotKeyShift db LeftShift OR RightShift ;shift state IF HotIsShift=FF HotKeySeq db LeftDown,LeftUp,LeftDown,LeftUp HotKeyLen equ $-HotKeySeq HotIndex db 0 ;# key in seq to compare next BetweenKeys db 0 ;timeout count between keys KeyTimeOut equ 10 ;more ticks means not a hotkey ;============================================================================== ; DATA FOR INT08H HANDLER TO CHECK FOR POPUP ;============================================================================== SafeWait db 0 ;count-down for safe popup MaxWait equ 8 ;wait no more 8/18 sec ;============================================================================== ; PROCESS & SYSTEM DATA ;============================================================================== OurSS dw 0 ;stack for popup routine OurSP dw 0 StackSize equ 512 ;bytes to reserve for stack OldSS dw 0 ;old stack seg OldSP dw 0 ;old stack off OurPSP dw 0 ;our PSP seg OldPSP dw 0 ;old PSP seg OldDTA label dword ;seg:off of old DTA area OldDTAOff dw 0 OldDTASeg dw 0 OurDTA label dword ;seg:off of our DTA OurDTAOff dw 0 OurDTASeg dw 0 OldBreak db 0 ;old ctrl-break state OldExtErr dw 3 dup (0) ;AX,BX,CX of ext err ;============================================================================== ; LOCATIONS FOR SAVED INTERRUPT VECTORS ;============================================================================== OldInt08 label dword ;Timer0 loaded before this OldInt08Off dw 0 OldInt08Seg dw 0 OldInt09 label dword ;Kb handler loadde before this OldInt09Off dw 0 OldInt09Seg dw 0 OldInt13 label dword ;BIOS diskette I/O OldInt13Off dw 0 OldInt13Seg dw 0 OldInt16 label dword ;BIOS kb Q-handler OldInt16Off dw 0 OldInt16Seg dw 0 OldInt1B label dword ;^break of process we steal OldInt1BOff dw 0 OldInt1BSeg dw 0 OldInt1C label dword ;timer tick of process we steal OldInt1COff dw 0 OldInt1CSeg dw 0 OldInt21 label dword ;DOS function dispatcher OldInt21Off dw 0 OldInt21Seg dw 0 OldInt23 label dword ;^C of process we steal OldInt23Off dw 0 OldInt23Seg dw 0 OldInt24 label dword ;crit err of process we steal OldInt24Off dw 0 OldInt24Seg dw 0 OldInt28 label dword ;DOS idles loaded before this OldInt28Off dw 0 OldInt28Seg dw 0 ;============================================================================== ; SPEAKER/TONE GENERATION DATA ;============================================================================== PB0port equ 61h ;port for speaker bit ErrLen1 equ 10 ;# outer err beep cycles ErrLen2 equ 80 ;# inner err beep cycles ErrLow equ 100 ;low tone wait in err beep ErrHi equ 40 ;hi tone wait in err beep ;============================================================================== ; ErrBeep - PRODUCE ERROR-INDICATING SOUND ON SPEAKER ;============================================================================== ErrBeep proc near assume ds:nothing, es:nothing, ss:nothing push ax ;save regs used push bx push cx push dx mov cx,ErrLen1 ;# mix-cycles for beep ErrBeep1: mov dx,ErrLow ;wait time for half-cycle mov bx,ErrLen2 ;len of one tone call DoTone ;output low err tone mov dx,ErrHi ;wait time for half-cycle mov bx,ErrLen2 ;len of one tone call DoTone ;output low err tone loop ErrBeep1 ;loop for some time pop dx pop cx ;restore regs pop bx pop ax ret ErrBeep endp ;============================================================================== ; DoTone - OUTPUT ONE TONE ON THE SPEAKER ; ; INPUT: DX: LOOP WAIT TIME FOR HALF CYCLE IN TONE ; BX: NUMBER OF CYCLES FOR TONE DURATION ; OUTPUT: NONE ; REGS: ALL PRESERVED ;============================================================================== DoTone proc near assume ds:nothing, es:nothing, ss:nothing push ax ;save regs used push bx push cx in al,PB0port ;get PB0 reg pattern mov ah,al ;save it DoTone1: and al,0fch ;mask off speaker bit out PB0port,al ;pull! mov cx,dx ;half cycle in counter DoTone2: loop DoTone2 ;leave there for half a cycle or al,2 ;turn on speaker bit out PB0port,al ;push! mov cx,dx ;half cycle in counter DoTone3: loop DoTone3 ;leave there for half a cycle dec bx ;count down tone duration jnz DoTone1 ;go through full tone mov al,ah ;AL=original PB0 reg value out PB0port,al ;restore pop cx ;restore regs pop bx pop ax ret DoTone endp ;============================================================================== ; TestSafe - CHECK IF THIS IS A SAFE TIME TO DO A POP UP ; ; RETURN CLC IF SAFE TO POP UP, CY IF NOT SAFE. ; ; CHECK IF ANY INTs ARE IN CRITICAL AREAS (InInt09 & InInt13) ; CHECK IF WE ARE IN AN OUR OWN INT28 CALL (In28Call) ; CHECK 8259A PIC ISR REGISTER FOR MISSING EOIs ; CHECK IF DOS IS STABLE FOR POP UP ; CHECK IF A PRINT SCREEN IS IN PROGRESS ;============================================================================== TestSafe proc near assume ds:nothing, es:nothing push ax ;save regs used push bx push ds ; ------------ CHECK INTs TO SEE IF THEY WERE INTERRUPTED AT BAD TIMES test TsrMode,InInt09 OR InInt13 OR In28Call jnz NotSafe ;jump if any INTs are chopped ; ------------ CHECK THE 8259A PIC ISR REGISTER FOR NON-EOIed HW INTs mov al,00001011b ;tell 8259A we want the ISR out 20h,al ;8259A command reg nop nop nop ;now, ISR should be ready in al,20h ;AL=mask of active INTs or al,al ;test all (IRQ0 *did* EOI) jnz NotSafe ;jump if active INTs ; ------------ NOW, ENSURE THAT DOS WAS NOT INTERRUPTED assume ds:nothing lds bx,InDosPtr ;now, DS:BX=InDos mov al,byte ptr [bx] ;get InDos to AL lds bx,CritErrPtr ;now, DS:BX=CritErr or al,byte ptr [bx] ;both flags zero? jz DosSafe ;YES - DOS is really idle test TsrMode,InInt28 ;is this an INT28h jz NotSafe ;NO - not safe, should be idle cmp al,1 ;YES - one InDos entry only? ja NotSafe ;NO - jump if more than one DosSafe: ; ------------ CHECK TO SEE IF A PRINT SCREEN IS IN PROGRESS mov ax,BiosXX mov ds,ax ;move DS to BIOS extra data seg assume ds:BiosXX cmp StatusByte,InPrtSc ;print screen in progress? je NotSafe ;YES - jump if prtsc ; ------------ SEEMS TO BE A SAFE TIME FOR POPUP IsSafe: clc ;CLC=safe to popup jmp short ExitSafe ;end this then ; ------------ APPARENTLY THIS IS JUST NOT THE TIME TO DO A POPUP NotSafe: stc ;CY=don't popup now ; ------------ RETURN TO CALLER WITH CARRY SET/CLEAR ExitSafe: pop ds ;restore regs pop bx pop ax ret TestSafe endp ;============================================================================== ; OurInt08 - TSR INT08H HANDLER TO WATCH FOR HOTKEY AND SAFE POPUP TIMES ; ; CALL OldInt08 ; CHECK FOR RE-ENTRANCE INTO CRITICAL INT08 CODE ; SET InInt08 FLAG ; CHECK FOR TIMEOUT BETWEEN KEYS IN HOTKEY SEQUENCE ; CHECK IF HOTKEY WAS PRESSED ; CHECK IF ALREADY InPopup OR InInt28 ; CHECK IF SAFE TIME FOR SYSTEM TO POPUP ; UPDATE FLAGS AND CALL POPUP IF SAFE ; GIVE ERROR BEEP IF POPUP WAS UNSAFE FOR A LONG TIME ; RESET InInt08 FLAG ; DO IRET ;============================================================================== ; ------------ NEAR JUMP DESTINATION FOR FAST IRET'S Exit08: iret ;IRET (!) ; ------------ ACTUAL INT08 ENTRY POINT OurInt08 proc far assume ds:nothing, es:nothing, ss:nothing pushf ;simulate INT08 cli ;in case others forgot it call OldInt08 ;call TSRs loaded before us ; ------------ ENSURE NO RECURSION INTO CRITICAL INT08 CODE sti ;we'll manage INTs test TsrMode,InInt08 ;already in here somewhere? jnz Exit08 ;YES - don't re-enter or TsrMode,InInt08 ;tell people we are here push ax ;need a few regs in this code ; ------------ COUNT DOWN TIME-OUT BETWEEN KEYS IN HOTKEY SEQUENCE test KeyMode,InHotMatch ;are we in a key match? jz TestHot08 ;NO - don't care then dec BetweenKeys ;count down timeout val jnz TestHot08 ;jump if no timeout yet mov HotIndex,0 ;start match from beginning and KeyMode,not InHotMatch ;just so we know it next time ; ------------ CHECK FOR POSSIBLE POPUP ACTIONS TestHot08: test KeyMode,HotKeyOn ;has hotkey been pressed? jz ExitInt08 ;NO - jump if no fun here test TsrMode,InInt28 OR InPopup jnz ExitInt08 ;jmp if not alr in business ; ------------ HOTKEY PRESSED, CHECK TO SEE IF IT IS SAFE TO POPUP cmp SafeWait,0 ;first time we find hotkey? ja TestSafe08 ;NO - wait has alr been set mov SafeWait,MaxWait ;# ticks to wait at most TestSafe08: call TestSafe ;now, CY clear if popup is safe jc NotSafe08 ;jump if popup is bad idea ; ------------ SEEMS SAFE TO POPUP AT THIS TIME, SO DO! xor al,al ;fast zero mov SafeWait,al ;don't count any more and KeyMode,not HotKeyOn ;clear hotkey status or TsrMode,InPopup ;tell'em we enter popup routine and TsrMode,not InInt08 ;OK to enter critical INT08 call InitPopup ;do actual popup or TsrMode,InInt08 ;back in INT08 code here and TsrMode,not InPopup ;not in popup code any more mov SafeWait,al ;in case of hotkey during popup and KeyMode,not HotKeyOn ;clear hotkey status jmp short ExitInt08 ;finally done ; ------------ UNSAFE POPUP TIME, COUNT DOWN SafeWait NotSafe08: dec SafeWait ;count down waiter jnz ExitInt08 ;jump if still no timeout ; ------------ NO SAFE TIMES FOUND FOR QUITE SOME TIME, ERROR and KeyMode,not HotKeyOn ;might as well clear hotkey call ErrBeep ;do an error beep ; ------------ NORMAL INT08H EXIT, RESET InInt08 ExitInt08: pop ax ;restore regs used and TsrMode,not InInt08 ;clear that flag iret ;straight back OurInt08 endp ;============================================================================== ; OurInt09 - TSR INT09H HANDLER TO WATCH FOR HOTKEY ; ; SAVE SCAN CODE ; CALL OldInt09 ; CHECK FOR RECURSION INTO CRITICAL INT09 CODE ; SET InInt09 FLAG ; CHECK IF HOTKEY ALREADY SET ; DETERMINE HOTKEY TYPE (SHIFT STATE OR KEY SEQENCE) ; CHECK SHIFT STATE IF HotIsShift ; COMPARE FOR KEY MATCH IF (NOT HotIsShift) ; SET HotKeyOn IF HOTKEY PRESSED ; RESET InInt09 FLAG ; DO IRET ;============================================================================== ; ------------ NEAR JUMP DESTINATION FOR EARLY EXITS Exit09: pop bx ;restore regs pop ax iret ;flags restored from stack ; ------------ ACTUAL INT09 ENTRY POINT OurInt09 proc far assume ds:nothing, es:nothing, ss:nothing push ax ;save regs used push bx ; ------------ READ SCAN CODE, IN CASE SEQUENCE MATCHING SELECTED in al,KbData ;Al=key, preserved by BIOS ; ------------ CALL BIOS TO PERFORM IT'S DUTIES pushf ;simulate INT (CLI alr set) cli ;in case others forgot it call OldInt09 ;call BIOS/earlier TSRs ; ------------ ENSURE NO RECURSION INTO CRITICAL INT09 CODE sti ;we'll manage INTs test TsrMode,InInt09 ;alr in business? jnz Exit09 ;YES - skip test till clear or TsrMode,InInt09 ;tell them we arrived here ; ------------ DETERMINE HOT KEY TYPE SELECTED test KeyMode,HotKeyOn ;already hotkey there? jnz ExitInt09 ;YES - no double hotkeys here test KeyMode,HotIsShift ;shift state type hotkey? jz CompSeq09 ;NO - go compare sequence ; ------------ COMPARE CURRENT SHIFT STATUS AGAINST HOTKEY push ds ;save current ds mov ax,BiosData ;move DS to BIOS data seg mov ds,ax ;DS can now access keyb vars assume ds:BiosData ;tell MASM about our DS mov al,KbFlag ;get BIOS shift state bits pop ds ;restore assume ds:nothing ;last thing we know about him and al,HotKeyShift ;isolate relevant bits cmp al,HotKeyShift ;our shift state in effect? jne ExitInt09 ;NO - not that shift state or KeyMode,HotKeyOn ;YES - flag hotkey jmp short ExitInt09 ;now we can be proud to leave ; ------------ MATCH KEY IN SCAN CODE SEQUENCE CompSeq09: mov bl,HotIndex ;next scan code to match xor bh,bh ;must be word cmp al,HotKeySeq[bx] ;does key match? je HotMatch09 ;YES - jump if match mov HotIndex,bh ;search from start next time and KeyMode,not InHotMatch ;current no match jmp short ExitInt09 ;now end this ; ------------ KEY MACTHED NEXT SCAN CODE IN HotKeySeq HotMatch09: inc bl ;new code at next pass cmp bl,HotKeyLen ;did we match whole sequence? jae HotHit09 ;YES - jump if full sequence mov HotIndex,bl ;NO - save new count mov BetweenKeys,KeyTimeOut ;reset counter between keys or KeyMode,InHotMatch ;we are in a match now jmp short ExitInt09 ;time to end this ; ------------ KEY MATCHED ALL SCAN CODES IN HOTKEY SEQUENCE HotHit09: or KeyMode,HotKeyOn ;say hotkey was pressed mov HotIndex,bh ;match 1st code next time and KeyMode,not InHotMatch ;that's the end of a match ; ------------ EXIT FROM INT09H, RESET InInt09 FLAG ExitInt09: and TsrMode,not InInt09 ;tell'em we left this code pop bx ;restore regs pop ax iret ;flags restored from stack OurInt09 endp ;============================================================================== ; OurInt13 - SET InInt13 FLAG TO SAY THAT WE ARE IN AN INT13H ;============================================================================== OurInt13 proc far assume ds:nothing, es:nothing, ss:nothing pushf ;save flags we use or TsrMode,InInt13 ;remember we are in BIOS now popf ;restore flags pushf ;simulate INT13 cli ;just in case others forgot call OldInt13 ;let BIOS handle it all pushf ;BIOS uses flag return and TsrMode, not InInt13 ;tell people we left INT13h popf ret 2 ;throw flags off stack OurInt13 endp ;============================================================================== ; OurInt16 - TSR INT16H HANDLER, INT28 CHAIN INTERFACE ; ; INPUT: AX = GetId ; OUTPUT: AX = MyId ; REGS: AX LOST, ALL OTHERS PRESERVED ; DESCRIPTION: DETERMINE IF TSR WITH THIS ID IS ALREADY IN MEMORY ; ; INPUT: AH = 00 ; OUTPUT: AX = NEXT KEY FROM BUFFER ; REGS; AX LOST, ALL OTHERS PRESERVED ; DESCRIPTION: RETURN A KEY FROM KEYBOARD BUFFER, WAIT TILL KEY IS PRESSED ; ; INPUT: AH = 02 ; OUTPUT: AX = KEY FROM BUFFER IN ANY ; ZF = NO KEYS IN BUFFER (AX PRESERVED) ; NZ = KEY IN BUFFER (RETURNED IN AX, KEY STILL IN BUFFER) ; DESCRIPTION: CHECK BUFFER FOR ANY PENDING KEYS, RETURN KEY IF ANY ; ; NOTE: ALL OTHER AX REQUEST CODES ARE PASSED ON TO BIOS INT16H HANDLER. ; ; NOTE: DURING INT28 POPUP (InPopup AND NOT InDosClr) FUNCTIONS AH=0 AND ; AH=1 WILL ISSUE INT28, UNLESS InDos HAS FROM VALUE AT POPUP OR ; CritErr HAS BEEN SET. ;============================================================================== OurInt16 proc far assume ds:nothing, es:nothing, ss:nothing sti ;we'll manage INTs pushf ;save callers flags cmp ax,GetId ;return ID request? jne NotId16 ;NO - jump if not ; ------------ TSR DIAGNOSTIC REQUEST, RETURN SPECIAL VALUE TO SAY WE ARE HERE mov ax,MyId ;ID val returned in AX popf ;restore flags iret ;return to caller ; ------------ PASS CONTROL TO BIOS, FLAGS ON STACK GoBios16: popf ;restore flags at INT time jmp OldInt16 ;continue in the woods ; ------------ REGULAR BIOS INT16 REQUEST, CHECK FOR ANY FANCY ACTIONS NotId16: test TsrMode,InPopup ;are we in a popup? jz GoBios16 ;NO - leave rest with BIOS test TsrMode,InDosClr ;InDos clear at popup? jnz GoBios16 ;YES - no need to signal INT28 popf ;restore original flags push bx ;we need a few regs here push cx push si push ds pushf ;original flags back on stack ; ------------ GET REQUEST CODE TO BH ENHANCED BIT TO BL mov bh,ah ;BH=function request code and bh,not 10h ;zap enhanced kybd bit cmp bh,1 ;any function above 1? ja ExitBios16 ;YES - leave rest with BIOS mov bl,ah ;BL used for enhanced bit and bl,10h ;BL=value of enhanced bit ; ------------ GET InDos To CL, CritErr to CH, SETUP REGS assume ds:nothing lds si,InDosPtr ;DS:[SI]=InDos mov cl,byte ptr [si] ;CL=InDos value lds si,CritErrPtr ;ES:[SI]=CritErr mov ch,byte ptr [si] ;CH=CritErr value mov si,ax ;save AX call value mov ax,cs ;move DS here, now we got it mov ds,ax assume ds:Cseg ;everybody should know ; ------------ CHECK KEYBOARD BUFFER, ORIGINAL FLAGS ON STACK Wait16: mov ah,1 ;AH=1=test buffer status or ah,bl ;maintain enhanced bit value popf ;restore original flags pushf ;simulate INT cli ;in case others forgot call OldInt16 ;now, ZF set if no keys pushf ;save result flags jnz TestSkip16 ;jump if a key was found ; ------------ NO KEY FOUND, CALL INT28 IF DOS InDos ALLOWS cmp cx,0001h ;CritErr=0, InDos=1 ? jne NextKey16 ;NO - wait for next key or TsrMode,In28Call ;tell people we called this INT int 28h ;now take your chance and TsrMode,not In28Call ;end of that call ; ------------ TEST BUFFER AGAIN IF INT16.00, IRET IF INT16.01 NextKey16: or bh,bh ;is this a wait for key? jz Wait16 ;YES - then go wait for it! mov ax,si ;restore original AX contents jmp short Exit16 ;NO - exit with status we got ; ------------ KEY IN BUFFER, IF CTRL-C WE MAY HAVE TO SKIP IT, FLAGS ON STACK TestSkip16: cmp al,3 ;is this Ctrl-C? jne TestExit16 ;NO - determine exit method test cx,not 0001h ;anything but InDos=1? jz TestExit16 ;NO - determine exit method ; ------------ SKIP CTRL-C IN KEYBOARD BUFFER mov ah,bl ;AH=0 + enhanced bit popf ;restore original INTs pushf ;save again pushf ;simulate INT cli ;simulate properly! call OldInt16 ;now, key should be gone jmp short Wait16 ;do as if nothing had happened ; ------------ KEY IN AX, IRET IF INT16.01, LEAVE WITH BIOS IF INT16.00 TestExit16: or bh,bh ;is this a wait for key? jnz Exit16 ;NO - do fast return mov ax,si ;YES - restore AX code ; ------------ PASS CONTROL TO BIOS, FLAGS & REGS ON STACK assume ds:nothing ExitBios16: popf ;restore work flags pop ds ;restore regs pop si pop cx pop bx cli ;should look like an INT jmp OldInt16 ;leave rest with BIOS ; ------------ RETURN FROM INT16, FLAGS & REGS ON STACK assume ds:nothing Exit16: popf ;restore proper flags pop ds ;restore regs pop si pop cx pop bx ret 2 ;IRET, without flags restore OurInt16 endp ;============================================================================== ; OurInt21 - INT21 FILTER TO THROW DANGEROUS DOS CALLS ON CRITICAL STACK ; ; CHECK IF InPopup AND InDosClr ; CHECK FUNCTION USES CONSOLE STACK ; SET CritErr IN DOS IF CONSOLE STACK USED ; CALL OldInt21 ; RESTORE CritErr IF CRITICAL STACK USED ;============================================================================== OurInt21 proc far assume ds:nothing, es:nothing pushf ;save calling flags sti test TsrMode,InPopup ;are we in a popup? jz GoDos21 ;NO - don't worry then test TsrMode,InDosClr ;console stack idle? jnz GoDos21 ;YES - nothing fancy then ; ------------ THIS IS 2ND CALL INTO DOS, SEE IF USING CONSOLE STACK cmp ah,0ch ;any function 00-0C? jbe UseCrit21 ;YES - use critical stack test TsrMode,NewDos ;NO - is this DOS 3.x? jnz GoDos21 ;YES - no other to worry about cmp ah,50h ;set PSP function? je UseCrit21 ;YES - use critical stack cmp ah,51h ;get PSP function? jne GoDos21 ;NO - leave it with DOS ; ------------ FORCE USE OF CRITICAL STACK FOR THIS CALL UseCrit21: assume ds:nothing ;nothing to say about DS push si ;save regs push ds lds si,CritErrPtr ;now, DS:[SI]=InDos mov byte ptr [si],-1 ;FF=use crit stack now pop ds ;restore regs pop si popf ;retsore flags setting pushf ;simulate INT cli ;in case others forgot call OldInt21 ;flags already on stack push si ;save regs push ds lds si,CritErrPtr ;now, DS:[SI]=InDos mov byte ptr [si],0 ;0=back to default stack pop ds ;restore regs pop si ret 2 ;IRET throw old flags ; ------------ PASS CONTROL TO DOS, FLAGS ON STACK GoDos21: popf ;restore original flags cli ;just in case someone forgot jmp OldInt21 ;let DOS handle the rest OurInt21 endp ;============================================================================== ; OurInt24 - SAFE DOS CRITICAL ERROR HANDLER ; ; IF DOS 3.X, FAIL THE SYSTEM CALL ; IF NOT DOS 3.X, IGNORE ERROR ;============================================================================== OurInt24 proc far assume ds:nothing, es:nothing, ss:nothing mov al,3 ;AL=3=fail system call test TsrMode,NewDos ;are we using DOS 3.x? jnz Exit24 ;YES - OK to use AL=3 xor al,al ;NO - have to ignore err then Exit24: iret ;return to DOS OurInt24 endp ;============================================================================== ; OurInt28 - TSR INT28H HANDLER, ALLOWS POPUP DURING DOS IDLE CALLS ; ; CALL OldInt28 ; CHECK FOR RECURSION INTO CRITICAL INT28 CODE (& OTHER INTs AS WELL) ; SET InInt28 FLAG ; CHECK FOR HOTKEY ; CHECK IF SAFE TO POPUP ; DO POPUP IF SAFE AT THIS TIME ; RESET InInt28 FLAG ; DO IRET ;============================================================================== ; ------------ NEAR JUMP DESTINATION FOR FAST IRET'S Exit28: iret ;IRET (!) ; ------------ ACTUAL INT28 ENTRY POINT OurInt28 proc far assume ds:nothing, es:nothing, ss:nothing pushf cli ;in case others forgot it call OldInt28 ;call TSRs loaded before this ; ------------ ENSURE NO RECURSION ON CRITICAL INT28 CODE sti ;we'll manage INT's after this test TsrMode,InInt08 OR InInt28 OR In28Call OR InPopup jnz Exit28 ;exit fast if already going or TsrMode,InInt28 ;tell'em we are here ; ------------ CHECK FOR POSSIBLE POPUP ACTIONS test KeyMode,HotKeyOn ;any hotkeys pressed? jz ExitInt28 ;NO - don't check any more then ; ------------ HOTKEY WAS PRESSED, ENSURE IT'S SAFE TO DO POPUP call TestSafe ;now, CY clear if popup is OK jc ExitInt28 ;jump if not to popup ; ------------ SEEMS OK TO DO POPUP, SO DO! and KeyMode,not HotKeyOn ;clear hotkey status or TsrMode,InPopup ;tell'em we enter popup routine and TsrMode,not InInt28 ;OK to enter critical INT28 call InitPopup ;then do popup or TsrMode,InInt28 ;back in INT28 code here and TsrMode,not InPopup ;not in popup code any more and KeyMode,not HotKeyOn ;clear hotkeys during popup ; ------------ NORMAL INT28H EXIT, RESET InInt28 FLAG ExitInt28: and TsrMode,not InInt28 ;tell'em we left this code iret ;we have nothing more to say OurInt28 endp ;============================================================================== ; NopInt - DUMMY IRET INSTRUCTION USED BY EMPTY INT HANDLERS ;============================================================================== NopInt: iret ;immediate return ;============================================================================== ; InitPopup - PREPARES SYSTEM FOR POPUP, THEN CALLS Popup, THEN RESTORES ; ; ESTABLISH INTERNAL WORK STACK ; SAVE CPU REGS ; UPDATE InDosClr FLAG WITH CURRENT VALUE OF InDos ; SAVE PROCESS RELATED SYSTEM INFO ; SAVE USER INTERRUPT VECTORS ; INSERT SAFE USER INTERRUPT VECTORS ; CALL POPUP ROUTINE ; RESTORE USER INTERRUPT VECTORS ; RESTORE PROCESS AND SYSTEM INFO ; CLEAR InDosClr FLAG TO PREVENT UNSAFE INT28 CALLs ; RESTORE CPU REGS ;============================================================================== InitPopup proc near assume ds:nothing, es:nothing, ss:nothing ; ------------ SWITCH TO PSP INTERNAL STACK mov OldSS,ss ;save current stack frame mov OldSP,sp cli ;always CLI for the old chips mov ss,OurSS ;move SS here mov sp,OurSP ;move SP into position sti ;OK guys ; ------------ SAVE ALL REGS push ax push bx push cx push dx push bp push si push di push ds push es mov ax,cs mov ds,ax ;mov DS here assume ds:Cseg ;tell MASM that ; ------------ TAG VALUE OF InDos FLAG AT TIME OF POPUP or TsrMode,InDosClr ;assume InDos=0 les si,InDosPtr ;now, ES:[SI]=InDos cmp byte ptr es:[si],1 ;InDos set? (>2 impossible) jb InDosSaved ;NO - jump if all clear DOS and TsrMode,not InDosClr ;clear flag for popup InDos InDosSaved: ; ------------ SAVE DOS 3.X EXTENDED ERROR INFO test TsrMode,NewDos ;really DOS 3.x? jz Dos3Saved ;NO - jump if not 3.x mov ah,59h ;to get err info from DOS xor bx,bx ;BX must be zero push ds ;save DS (killed by DOS) int 21h ;ext err info in AX,BX,CX pop ds ;restore mov OldExtErr[0],ax ;save mov OldExtErr[2],bx mov OldExtErr[4],cx Dos3Saved: ; ------------ SAVE CURRENT BREAK STATE, RELAX BREAK CHECKING mov ax,3302h ;to swap DL with BREAK value xor dl,dl ;DL=0=relax checking int 21h ;current level in DL mov OldBreak,dl ;save current level ; ------------ SAVE CURRENT USER INT VECTORS mov ax,351bh ;BIOS ctrl-break int int 21h ;ES:BX=vector mov OldInt1BOff,bx ;save it mov OldInt1BSeg,es mov ax,351ch ;BIOS timer tick int 21h ;ES:BX=vector mov OldInt1COff,bx ;save it mov OldInt1CSeg,es mov ax,3523h ;DOS ctrl-C int 21h ;ES:BX=vector mov OldInt23Off,bx ;save it mov OldInt23Seg,es mov ax,3524h ;DOS crit err handler int 21h ;ES:BX=vector mov OldInt24Off,bx ;save it mov OldInt24Seg,es ; ------------ INSERT DUMMY IRET INTO DANGEROUS VECTORS mov dx,offset NopInt ;now, DS:DX=dunny iret mov ax,251bh ;BIOS ctrlk-break handler int 21h ;set to IRET mov ax,251ch ;BIOS timer tick int 21h ;set to IRET mov ax,2523h ;DOS ctrl-C handler int 21h ;set to IRET ; ------------ ESTABLISH SAFE CRITICAL ERROR HANDLER mov dx,offset OurInt24 ;now, DS:DX=safe crit err mov ax,2524h ;to set crit err handler int 21h ; ------------ SAVE CURRENT DTA AREA, SET OUR DEFAULT DTA mov ah,2fh ;to obtain current DTA from DOS int 21h ;DTA addr now in ES:BX mov OldDTAOff,bx ;save it mov OldDTASeg,es push ds ;save DS for a while lds dx,OurDTA ;DS:DX=our DTA addr mov ah,1ah ;to set DTA via DOS int 21h ;set that addr pop ds ;restore DS ; ------------ SAVE CURRENT PSP, ESTABLISH OURS INSTEAD mov ax,5100h ;to get PSP from DOS int 21h ;current PSP now in BX mov OldPSP,bx ;save it mov bx,OurPSP ;het our PSP instead mov ax,5000h ;to set our PSP int 21h ; ------------ CALL USER POPUP ROUTINE call Popup ;finally! ; ------------ RESTORE TO SAVED CURRENT PROCESS mov bx,OldPSP ;new current process in BX mov ax,5000h ;to set PSP via DOS int 21h ;restore original PSP ; ------------ RESTORE SAVED DTA push ds ;save DS for a while lds dx,OldDTA ;DS:DX=our DTA addr mov ah,1ah ;to set DTA via DOS int 21h ;set that addr pop ds ;restore DS ; ------------ RESTORE SAVED INTERRUPT VECTORS push ds ;save for a while assume ds:nothing ;be careful about MASM lds dx,OldInt1B ;BIOS ctrl-break handler mov ax,251bh int 21h lds dx,OldInt1C ;BIOS timer tick mov ax,251ch int 21h lds dx,OldInt23 ;DOS ctrl-C mov ax,2523h int 21h lds dx,OldInt24 ;DOS crit err handler mov ax,2524h int 21h pop ds ;restore data seg DS assume ds:Cseg ; ------------ RESTORE SAVED BREAK CHECKING LEVEL mov ax,3301h ;to set break check level mov dl,OldBreak ;get saved break state int 21h ; ------------ RESTORE DOS 3.X SPECIFIC SYSTEM INFO test TsrMode,NewDos ;using DOS 3.x jz Dos3Restored ;NO - jump if old DOS 2 mov dx,offset OldExtErr ;DS:DX=3 words of ext err mov ax,5d0ah ;to set ext err info int 21h Dos3Restored: ; ------------ RESET InDosSet FLAG VALUE TO PREVENT UNSAFE INT28 or TsrMode,InDosClr ;now we only care that InDos=0 ; ------------ RESTORE USER REGS pop es pop ds pop di pop si pop bp pop dx pop cx pop bx pop ax assume ds:nothing ; ------------ RETURN TO USER STACK cli ;always CLI for the old chips mov ss,OldSS ;restore SS mov sp,OldSP ;restore SP sti ;OK guys ret InitPopup endp ;============================================================================== ; DATA FOR POPUP ROUTINE ;============================================================================== DosReadMsg db 13,10,'Reading DOS CON (press <Enter> to terminate)',13,10 DosReadLen equ $-DosReadMsg BiosReadMsg db 'Reading BIOS keyboard (press any key... )',8,8 BiosReadLen equ $-BiosReadMsg DoneMsg db ' key pressed, exit from TSR DEMO)',13,10 DoneLen equ $-DoneMsg Scratch db 80 dup (?) ;============================================================================== ; Popup - POPUP USER ROUTINE ; ; ALL REGISTERS EXCEPT SS:SP AND DS MAY BE CHANGED. ; DS IS PRESET TO THE TSR DATA SEGMENT. ; ; NOTE: UPON ENTRY TO THIS ROUTINE ALL DOS FUNCTIONS MAY BE CALLED. ; IF POPUP WAS DONE ON INT28, WITH CritErr==1, ALL DOS FUNCTIONS ; THAT WOULD NORMALLY USE THE CONSOLE STACK, WILL GO TO THE CRITICAL ; STACK, HENCE PREVENTING FURTHER POPUP DURING THE DOS CALL. ; (HOWEVER, MOST TSRs WOULD NOT POPUP ANYWAY, SINCE InDos==2). ; ; ADDRESSES OF THE InDos AND CritErr ARE STORED IN THE DOUBLE WORDS ; InDosPtr AND CritErrPtr. ; ; AT ENTRY CritErr FLAG IS 0 (ZERO), InDos NO GREATER THAN 1 (ONE). ;============================================================================== Popup proc near assume ds:Cseg, es:nothing, ss:nothing mov ah,40h ;DOS write handle mov bx,1 ;standard output handle mov dx,offset DosReadMsg ;DS:DX=str to write mov cx,DosReadLen ;CX=# chars to write int 21h ;output that string mov ah,3fh ;DOS read handle xor bx,bx ;standard input handle mov dx,offset Scratch ;scratch buf for key mov cx,80 ;read till CR hit int 21h mov ah,40h ;read from BIOS msg mov bx,1 mov dx,offset BiosReadMsg mov cx,BiosReadLen int 21h xor ah,ah ;to let BIOS wait for key int 16h ;now, key was pressed mov ah,40h ;write confirm msg mov bx,1 mov dx,offset DoneMsg mov cx,DoneLen int 21h ret Popup endp ;============================================================================== ; TSR IRON CURTAIN - HE WHO CROSSES THIS CURTAIN WILL BE GONE AFTER TSR! ;============================================================================== TsrCurtain: ;TSR memory break ;============================================================================== ; NON-RESIDENT MESSAGES FOR INIT ;============================================================================== BannerMsg label byte db 13,10 db '<<<<<< TSR DEMO >>>>>>',13,10 db ' Thomas Brandenborg',13,10 db ' Version 2.00',13,10,10 db '$' FirstMsg label byte db 'Pop up routine installed resident.',13,10 db '$' SecondMsg label byte db 'TSR DEMO already loaded.',13,10 db '$' HotKeyMsg label byte db 'Hit <Left Shift> twice to pop up!',13,10,10 db '$' Dos1Msg label byte db 'OOPS!',7,13,10 db 'Must use DOS release 2.00 or later!',13,10,10 db '$' BadDosMsg label byte db 'OOPS!',7,13,10 db 'Did not recognize DOS version!',13,10,10 db '$' ; ------------ DOS ERROR LEVEL EXIT CODES xOk equ 0 ;normal, OK exit xSecond equ 1 ;TSR already loaded xBadDos equ 2 ;CritErr flag not found ;============================================================================== ; Init - INITIALIZE TSR APPLICATION, ENTERED UPON DOS LOAD ; ; DISPLAY BANNER, INITIALIZE SYSTEM DATA, CHECK IF ALREADY LOADED, ; HOOK INTO INTERRUPT CHAIN, TERMINATE, BUT STAY RESIDENT. ;============================================================================== Init proc near assume ds:Cseg, es:nothing, ss:nothing mov dx,offset BannerMsg mov ah,9 int 21h ;display programme banner ; ------------ USE INT16H DIAGNOSTIC TO SEE IF TSR ALREADY INSTALLED mov ax,GetId ;INT16h diagnostic request int 16h ;now, AX=MyId if installed cmp ax,MyId ;TSR already installed? jne CheckDos ;NO - jump if not installed ; ------------ TSR ALREADY INSTALLED, DISPLAY MSG, EXIT mov dx,offset SecondMsg mov ah,9 int 21h ;display alr installed msg mov dx,offset HotKeyMsg mov ah,9 int 21h ;be kind & disp hot key mov ax,4c00h + xSecond ;error level in AL int 21h ;abot now ; ------------ IDIOT IS RUNNING DOS 1, LEAVE THE OLD FASHION WAY! Dos1: mov dx,offset Dos1Msg mov ah,9 int 21h ;display msg about DOS 1 int 20h ;no err level for DOS 1 ; ------------ ENSURE DOS VERSION IS NEWER THAN 2.00 CheckDos: or TsrMode,NewDos ;assume suing DOS 3.x mov ah,30h ;to get DOS version number int 21h ;version is AL.AH cmp al,2 ;release 2 or newer? jb Dos1 ;NO - jump if DOS 1 in use ja DosFlags ;jump if DOS 3.x and TsrMode,not NewDos ;now, say we use DOS 2.x ; ------------ INITIALIZE PTRS TO DOS FLAGS - 1ST InDos DosFlags: mov ax,3400h ;to get InDos ptr int 21h ;ES:BX=seg:off of InDos mov InDosOff,bx ;save ptr mov InDosSeg,es ; ------------ WE NEED CritErr TO USE PSP FUNCTIONS IN DOS 2.X (CHIPs WAY) xor dl,dl ;DL=0=this is 1st scan mov CritErrSeg,es ;DOS seg still in ES CritScan: mov di,bx ;start search at InDos mov cx,2000h ;search max 1000h words mov ax,3e80h ;opcode CMP BYTE PTR [CritErr] cld ;better serach forward CritScan2: repne scasw ;search till found or end jne NoCritFound ;jump if CMP not found ;ES:[DI-2] at: ; CMP BYTE PTR [CritErr] ; JNZ ... ; MOV SP,stack addr cmp byte ptr es:[di][5],0bch ;really CMP SP there? jne CritScan2 ;NO - scan again if not mov ax,word ptr es:[di] ;now, AX=CritErr offset mov CritErrOff,ax ;save it jmp short InitData ;OK to end this now NoCritFound: or dl,dl ;was this1 st scan? jnz BadDos ;NO - CritErr not founbd at all inc dl ;DL=1=this is 2nd scan inc bx ;try scan at odd/even offset jmp CritScan ;scan again ; ------------ COULD NOT LOCATE DOS CritErr FLAG - THAT'S AN ERROR BadDos: mov dx,offset BadDosMsg mov ah,9 int 21h ;display msg about that mov ax,4c00h + xBadDos ;err level in AL int 21h ;OK to use 4C (DOS >= 2) ; ------------ INITIALIZE SYSTEM DATA VARIABLES InitData: ;store position for stack mov OurSP,TsrCurtain - ComEntry + 100h + StackSize mov OurSS,cs ;stack seg is code seg mov ax,5100h ;to get current PSP from DOS int 21h ;PSP now in BX mov OurPSP,bx ;save our PSP mov ah,2fh ;to get current DTA from DOS int 21h ;now, ES:BX=current DTA mov OurDTAOff,bx ;save it mov OurDTASeg,es and KeyMode,not HotIsShift ;hotkey is not shift state or TsrMode,InDosClr ;will prevent unsafe INT28s ; ------------ SAVE VECTORS FOR OUR MONITOR INTERRUPTS mov ax,3508h ;BIOS timer0 tick handler int 21h ;ES:BX=vector mov OldInt08Off,bx mov OldInt08Seg,es mov ax,3509h ;BIOS kb HW handler int 21h ;ES:BX=vector mov OldInt09Off,bx mov OldInt09Seg,es mov ax,3513h ;BIOS disk I/O service int 21h ;ES:BX=vector mov OldInt13Off,bx mov OldInt13Seg,es mov ax,3516h ;BIOS kb read int 21h ;ES:BX=vector mov OldInt16Off,bx mov OldInt16Seg,es mov ax,3521h ;DOS functions dispatcher int 21h ;ES:BX=vector mov OldInt21Off,bx mov OldInt21Seg,es mov ax,3528h ;DOS idle hook int 21h ;ES:BX=vector mov OldInt28Off,bx mov OldInt28Seg,es ; ------------ ESTABLISH IRET INT23 TO PREVENT BREAK DURING VECTOR FIX mov dx,offset NopInt ;DS:DX=dummy vector to set mov ax,2523h ;to set ^C handler through DOS int 21h ;now, no break will occur ; ------------ SAVE VECTORS FOR OUR MONITOR INTERRUPTS mov ax,2508h ;to set our INT08h handler mov dx,offset OurInt08 ;DS:DX=new vector int 21h ;let DOS set vector mov ax,2509h ;to set our INT09h handler mov dx,offset OurInt09 ;DS:DX=new vector int 21h ;let DOS set vector mov ax,2513h ;to set our INT13h handler mov dx,offset OurInt13 ;DS:DX=new vector int 21h ;let DOS set vector mov ax,2516h ;to set our INT16h handler mov dx,offset OurInt16 ;DS:DX=new vector int 21h ;let DOS set vector mov ax,2521h ;to set our INT21h handler mov dx,offset OurInt21 ;DS:DX=new vector int 21h ;let DOS set vector mov ax,2528h ;to set our INT28h handler mov dx,offset OurInt28 ;DS:DX=new vector int 21h ;let DOS set vector ; ------------ DISLAY MSG ABOUT HOW WELL THIS IS ALL RUNNING mov dx,offset FirstMsg mov ah,9 int 21h ; display confirm msg mov dx,offset HotKeyMsg mov ah,9 int 21h ;disp hot key ; ------------ EXIT, SAY GOOD BYE TO FRIENDS BEHIND CURTAIN! mov es,EnvSeg ;ES=our environment copy mov ah,49h ;to let DOS free block int 21h ;environment copy freed mov dx,(TsrCurtain-ComEntry+100h+StackSize+15) SHR 4 mov ax,3100h + xOk ;TSR, AL=err level int 21h Init endp ;============================================================================== Cseg ends end ComEntry