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Make getint and setint reuse cs segment

This commit is contained in:
Nero 2020-04-18 23:44:16 +02:00
parent 4a92c4bc1e
commit c1c012c5fc
1 changed files with 13 additions and 26 deletions
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39
boot/kernel.asm
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@ -94,44 +94,31 @@ sftab: dw sferr, sferr, sferr, sferr
dw sferr, sferr, sferr, sferr
dw sferr, sferr, sferr, sferr
; IN al number
; OUT bx al * 4
times4: push ax
xor ah, ah
add al, al
add al, al
mov bx, ax
pop ax
ret
; DOS 2+ - GET INTERRUPT VECTOR
; IN al interrupt number
; OUT es:bx current interrupt handler
getint: push ds
; DS=0
xor bx, bx
mov ds, bx
getint: xor bx, bx
; BX=AL*4
call times4
les bx, [bx]
pop ds
mov bl, al
add bl, bl
add bl, bl
; load vector into ES:BX
les bx, [cs:bx]
ret
; DOS 25h: Set interrupt vector
; IN al interrupt number
; ds:dx entry point
setint: push es
push bx
; ES=0
setint: push bx
xor bx, bx
mov es, bx
; BX=AL*4
call times4
mov [es:bx], dx
mov ax, ds
mov [es:bx+2], ds
mov bl, al
add bl, bl
add bl, bl
; save DS:DX into vector
mov [cs:bx], dx
mov [cs:bx+2], ds
pop bx
pop es
ret
bpb: times bpb_len db 0