64 lines
1.1 KiB
NASM
64 lines
1.1 KiB
NASM
; assumptions about the starting envionment
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cpu 8086
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org 0x0000 ; if we are not at CS:0000, CS adjustment will fix it for us
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; dl probable drive number
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; ds:si probable pointer to partition structure
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; es:bx probable pxeenv+ structure
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; ss:sp functional stack
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_startup:
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; during PXE, CS=0000 and IP=7C00
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; adjust CS so our offsets match org setting above
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mov ax, _exit
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push ax ; store exit addr on stack so main will return to it
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push bx ; backup bx
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call near .push_ip
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.push_ip:
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pop bx
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sub bx, .push_ip ; subtract expected value ...
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shr bx,1 ; shift it to 4 bits to the right
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shr bx,1
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shr bx,1
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shr bx,1
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mov ax,cs
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add ax,bx ; so we can add it to cs
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pop bx ; restore bx
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push ax ; cs
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mov ax, main
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push ax ; ip
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sti
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retf ; jump
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_exit:
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mov si, .message
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call kprintf
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int 0x20
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.loop:
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hlt
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jmp .loop
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.message:
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db "Halted: Waiting for poweroff...", 0
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main:
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mov ax,cs
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mov ds,ax
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sub sp, 0x30
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xor ax,ax
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mov es,ax
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mov ax,_int_2F
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xchg ax,[es:0x2F*4]
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mov ax,cs
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xchg ax,[es:0x2F*4+2]
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int 0x2F
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test ax, 0xFF
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int 0x2F
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add sp, 0x30
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ret
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%include "dumpreg.asm"
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%include "kprintf.asm"
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