rdos/kernel/main.asm

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cpu 8086
org 0x0100
jmp init
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isr_dos_main:
cmp ah, 0x01
je isr_getc_echo
cmp ah, 0x02
je isr_putc
cmp ah, 0x25
je isr_intr_register
jmp isr_invalid
%include "intr.asm"
%include "chario.asm"
; ISR for invalid subfunctions or unimplemented
isr_invalid:
mov bp, 0xFEFE
int3
.hlt:
hlt
jmp .hlt
; ISR tail to set carry flag to signal error
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isr_error:
push bp
mov bp, sp
; set carry flag
or WORD [SS:BP+6], 1
pop bp
isr_return:
iret
init:
mov ax, cs
mov ds, ax
mov es, ax
mov dx, isr_dos_main
mov ax, 0x2521
pushf
push cs
call isr_dos_main
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mov cx, WORD [0x80]
xor ch, ch
mov si, 0x81
.loop:
lodsb
call putc
loop .loop
cli
.halt:
hlt
jmp .halt
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kernel_end: