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Add proper _exit procedure

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Nero 2019-03-13 21:11:30 +00:00
parent bb675a67a7
commit 4d827ec4e9
1 changed files with 17 additions and 6 deletions
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23
main.asm
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@ -6,26 +6,37 @@ org 0x0000 ; if we are not at CS:0000, CS adjustment will fix it for us
; es:bx probable pxeenv+ structure ; es:bx probable pxeenv+ structure
; ss:sp functional stack ; ss:sp functional stack
_startup:
; during PXE, CS=0000 and IP=7C00 ; during PXE, CS=0000 and IP=7C00
; adjust CS so our offsets match org setting above ; adjust CS so our offsets match org setting above
push bx ; offset register for calculations mov ax, _exit
call near __startup_push_ip ; push ip push ax ; store exit addr on stack so main will return to it
__startup_push_ip: push bx ; backup bx
call near .push_ip
.push_ip:
pop bx pop bx
sub bx, __startup_push_ip ; subtract expected value ... sub bx, .push_ip ; subtract expected value ...
shr bx,1 ; shift it to 4 bits to the right shr bx,1 ; shift it to 4 bits to the right
shr bx,1 shr bx,1
shr bx,1 shr bx,1
shr bx,1 shr bx,1
mov ax,cs mov ax,cs
add ax,bx ; so we can add it to cs add ax,bx ; so we can add it to cs
pop bx pop bx ; restore bx
push ax ; cs push ax ; cs
mov ax, main mov ax, main
push ax ; ip push ax ; ip
sti
retf ; jump retf ; jump
string_halt: _exit:
mov si, .message
call kprintf
int 0x20
.loop:
hlt
jmp .loop
.message:
db "Halted: Waiting for poweroff...", 0 db "Halted: Waiting for poweroff...", 0
main: main: