问题
How do you properly set, and then reset, the keyboard ISR in DOS? (x86 assembly, real mode, 16 bit, with TASM)
I have the following assembly code which sets up my ISR for the keyboard. All it is supposed to do is print out a sentence each time a key is pressed, up to five times. Then it is supposed to exit.
It seems like the ISR is being installed correctly. It will print out a sentence each time a key is pressed (once for down, once for up). However, it appears as though I am uninstalling the ISR incorrectly as I'm unable to enter text into the DOS command line after running the program.
(I have updated the code below to store/restore DS in the ISR, read from port 60h, and handle EOI calls thanks to feedback received so far.)
.model small
.data
our_text db "Interrupt intercepted", 0dh, 0ah, "$"
old_int_seg dw 0
old_int_off dw 0
keyCount dw 0
.code
.startup
cli
mov ah, 035 ; get current keyboard int vector
mov al, 09h ; and save it, so we can restore it later
int 21h
mov [old_int_off], bx
mov bx, es
mov [old_int_seg], bx
mov ax, cs
mov ds, ax ; load data segment with code segment
;(the one we are in now)
mov ah, 25h ; Set Interrupt Vector Command
mov al, 9 ; Interrupt to replace
lea dx, ISR ;load dx with our interrupt address
int 21h
sti
mov ax,@data
mov ds,ax
infinite:
mov ax,keyCount[0]
cmp ax,5
jl infinite ;check for 5 presses
cli ;restore old interrupt
mov ax, [old_int_seg]
mov ds, ax
mov dx, [old_int_off]
mov ah, 25h
mov al, 09h
int 21h
sti
mov ah,4Ch ; quit
mov al,00h
int 21h
ISR proc far
; save old registers
push ax
push cx
push dx
push bx
push sp
push bp
push si
push di
push ds
mov ax,@data ;print text
mov ds,ax
xor ah,ah
mov ah, 9
lea dx, our_text
int 21h
mov ax,keyCount
inc ax
mov [keyCount],ax
in al, 60h
; send EOI to keyboard
in al, 61h
mov ah, al
or al, 80h
out 61h, al
mov al, ah
out 61h, al
; send EOI to master PIC
mov al, 20h
out 20h, al
pop ds
pop di
pop si
pop bp
pop sp
pop bx
pop dx
pop cx
pop ax
iret
ISR endp
What's wrong with how I'm restoring the original keyboard ISR? Why am I unable to type anything into the command prompt in DOS after running the program?
回答1:
If it helps here is my ancient keyboard handler for MS-DOS coded in NASM
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;Keyboard int 09 driver ver: 1.4
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;keywait wait for change from keyboard scancode >> ax
;keyadr si<=adr of NAME of keycode in ax
;int09i install int 09
;int09u uninstall int 09
;int09 update tab press/pop status (0=pop,255=pressed) and key...
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;key.ascii ASCII key code byte
;key.scan tab key code word
;key.name adr of key name in tab word
;key.tab0/1/2 scan(Byte) ,pressed/poped,ASCII,ASCIIZ
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Subroutines: ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
keywait:mov ax,[cs:key.scan];wait for change from keyboard scancode >> ax
.l0: cmp ax,[cs:key.scan]
jz .l0
ret
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
keyadr: push ax ;si<=adr of NAME of keycode ax
cmp ax,197+512 ;not if Pause or Break
jz .q0
cmp ax,198+512
jz .q0
and al,127
.q0: lea si,[cs:key.tab0]
cmp ah,0
jz .r0
lea si,[cs:key.tab1]
cmp ah,1
jz .r0
lea si,[cs:key.tab2]
cmp ah,2
jz .r0
jmp .err
.r0: xchg al,ah
.l0: mov al,[cs:si]
add si,3
cmp al,ah
jz .esc
cmp al,255
jz .err
.l1: mov al,[cs:si]
inc si
or al,al
jnz .l1
jmp .l0
.err: lea si,[cs:.errkey]
.esc: pop ax
ret
db 1,0,'?'
.errkey:db 'Unknown key',0
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
int09i: pusha ;install int 09
push es
mov al,9h
mov ah,35h
int 21h
mov [cs:int09.vect],bx
mov [cs:int09.vect+2],es
mov al,9h
mov ah,25h
lea dx,[cs:int09]
int 21h
pop es
popa
ret
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
int09u: push ds ;uninstall int 09
pusha
mov dx,[cs:int09.vect]
mov ax,[cs:int09.vect+2]
mov ds,ax
mov al,9h
mov ah,25h
int 21h
popa
pop ds
ret
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Prerusenia: ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
int09: cli ;keyboard
pusha
in al,60h
mov bx,[cs:key.stat]
cmp bl,1
jz .r1
cmp bl,2
jz .r2
.r0: inc bl ;level0 ... first byte of scan code
cmp al,0E0h
jz .esc
inc bl
mov bh,5
cmp al,0E1h
jz .esc
sub ah,ah ;normal code
mov [cs:key.scan],ax
sub bx,bx
jmp .esc
.r1: mov bx,2+256*2 ;level1 ... second byte of scan code
cmp al,2Ah
jz .esc
cmp al,46h
jz .esc
cmp al,0AAh
jz .esc
mov ah,1 ;extended1 code
mov [cs:key.scan],ax
sub bx,bx
jmp .esc
.r2: dec bh
jnz .esc
mov ah,2 ;extended2 code
mov [cs:key.scan],ax
sub bx,bx
.esc: mov [cs:key.stat],bx
mov ax,[cs:key.scan]
call keyadr
mov ah,[cs:si-1] ;ASCII
mov [cs:key],ah
mov [cs:key.name],si;NAME ADR
and al,128
jz .keyp1
.keyp0: sub ax,ax
mov [cs:si-2],al
mov [cs:key],al
mov [cs:key.scan],ax
mov [cs:key.name],word key.tab0+3
jmp .esc0
.keyp1: mov [cs:si-2],byte 255
.esc0: in al,61h ;end of interrupt ...this is a must
mov ah,al
or al,80h
out 61h,al
xchg al,ah
out 61h,al
mov al,20h
out 20h,al
popa
sti
iret
.vect: dw 0,0
key:
.ascii db 0 ;ASCII
.scan dw 0 ;low=key code ,hi=tab 0,1,2
.name dw 0 ;adr of key NAME
.stat: db 0,0 ;byte count of code,number of readed byte
;tables: scancode low(hi is tab 0,1,2),pressed/poped,ASCII,name,0
.tab0: db 0,0,' ',' ',0 ;basic scan codes
db 1,0,'?','Esc',0
db 2,0,'1','1',0
db 3,0,'2','2',0
db 4,0,'3','3',0
db 5,0,'4','4',0
db 6,0,'5','5',0
db 7,0,'6','6',0
db 8,0,'7','7',0
db 9,0,'8','8',0
db 10,0,'9','9',0
db 11,0,'0','0',0
db 12,0,'-','-',0
db 13,0,'=','=',0
db 14,0, 8 ,'Backspace',0
db 15,0, 9 ,'Tab',0
db 16,0,'Q','Q',0
db 17,0,'W','W',0
db 18,0,'E','E',0
db 19,0,'R','R',0
db 20,0,'T','T',0
db 21,0,'Y','Y',0
db 22,0,'U','U',0
db 23,0,'I','I',0
db 24,0,'O','O',0
db 25,0,'P','P',0
db 26,0,'[','[',0
db 27,0,']',']',0
db 28,0, 13,'Enter',0
db 29,0,'?','L-Ctrl',0
db 30,0,'A','A',0
db 31,0,'S','S',0
db 32,0,'D','D',0
db 33,0,'F','F',0
db 34,0,'G','G',0
db 35,0,'H','H',0
db 36,0,'J','J',0
db 37,0,'K','K',0
db 38,0,'L','L',0
db 39,0,';',';',0
db 40,0,'"','"',0
db 41,0,'~','~',0
db 42,0,'?','L-Shift',0
db 43,0,'\','\',0
db 44,0,'Z','Z',0
db 45,0,'X','X',0
db 46,0,'C','C',0
db 47,0,'V','V',0
db 48,0,'B','B',0
db 49,0,'N','N',0
db 50,0,'M','M',0
db 51,0,',',',',0
db 52,0,'.','.',0
db 53,0,'/','/',0
db 54,0,'?','R-Shift',0
db 55,0,'*','Num *',0
db 56,0,'?','L-Alt',0
db 57,0,' ','Space',0
db 58,0,'?','Caps Lock',0
db 59,0,'?','F1',0
db 60,0,'?','F2',0
db 61,0,'?','F3',0
db 62,0,'?','F4',0
db 63,0,'?','F5',0
db 64,0,'?','F6',0
db 65,0,'?','F7',0
db 66,0,'?','F8',0
db 67,0,'?','F9',0
db 68,0,'?','F10',0
db 69,0,'?','Num Lock',0
db 70,0,'?','Scroll Lock',0
db 71,0,'7','Num 7',0
db 72,0,'8','Num 8',0
db 73,0,'9','Num 9',0
db 74,0,'-','Num -',0
db 75,0,'4','Num 4',0
db 76,0,'5','Num 5',0
db 77,0,'6','Num 6',0
db 78,0,'+','Num +',0
db 79,0,'1','Num 1',0
db 80,0,'2','Num 2',0
db 81,0,'3','Num 3',0
db 82,0,'0','Num 0',0
db 83,0,'.','Num .',0
db 84,0,'?','Alt-Prnscr',0
db 87,0,'?','F11',0
db 88,0,'?','F12',0
db 255
.tab1: db 28,0,'?','Num Enter',0 ;scan codes after E0h
db 29,0,'?','R-Ctrl',0
db 53,0,'/','Num /',0
db 55,0,'?','System Request',0
db 56,0,'?','R-Alt',0
db 71,0,'?','Home',0
db 72,0,'?','Up',0
db 73,0,'?','Page Up',0
db 75,0,'?','Left',0
db 77,0,'?','Right',0
db 79,0,'?','End',0
db 80,0,'?','Down',0
db 81,0,'?','Page Down',0
db 82,0,'?','Ins',0
db 83,0,'?','Del',0
db 93,0,'?','Win F2',0
db 255
.tab2: db 55,0,'?','Print Screen',0 ;scan codes after E0h AAh E0h
db 53,0,'?','Shift-Num /',0
db 71,0,'?','Shift-Home',0
db 72,0,'?','Shift-Up',0
db 73,0,'?','Shift-Page Up',0
db 75,0,'?','Shift-Left',0
db 77,0,'?','Shift-Right',0
db 79,0,'?','Shift-End',0
db 80,0,'?','Shift-Down',0
db 81,0,'?','Shift-Page Down',0
db 82,0,'?','Shift-Insert',0
db 83,0,'?','Shift-Delete',0
db 197,0,'?','Pause',0
db 198,0,'?','Break',0
db 255
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Scan codes constants: ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
.esc equ 1
.n1 equ 2
.n2 equ 3
.n3 equ 4
.n4 equ 5
.n5 equ 6
.n6 equ 7
.n7 equ 8
.n8 equ 9
.n9 equ 10
.n0 equ 11
.minus equ 12
.equal equ 13
.bckspc equ 14
.tab equ 15
.q equ 16
.w equ 17
.e equ 18
.r equ 19
.t equ 20
.y equ 21
.u equ 22
.i equ 23
.o equ 24
.p equ 25
.enter equ 28
.lctrl equ 29
.a equ 30
.s equ 31
.d equ 32
.f equ 33
.g equ 34
.h equ 35
.j equ 36
.k equ 37
.l equ 38
.lshift equ 42
.z equ 44
.x equ 45
.c equ 46
.v equ 47
.b equ 48
.n equ 49
.m equ 50
.rshift equ 54
.lalt equ 56
.space equ 57
.caps equ 58
.f1 equ 59
.f2 equ 60
.f3 equ 61
.f4 equ 62
.f5 equ 63
.f6 equ 64
.f7 equ 65
.f8 equ 66
.f9 equ 67
.f10 equ 68
.f11 equ 87
.f12 equ 88
.rctrl equ 256+29
.ralt equ 256+56
.home equ 256+71
.up equ 256+72
.pgup equ 256+73
.left equ 256+75
.right equ 256+77
.end equ 256+79
.down equ 256+80
.pgdown equ 256+81
.insert equ 256+82
.delete equ 256+83
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; End. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
来源：https://stackoverflow.com/questions/45537933/set-and-reset-keyboard-interrupt-service-routines-in-x86-real-mode-within-dos-wi