rdos/main.asm

; assumptions about the starting envionment
cpu 8086
org 0x0000 ;	if we are not at CS:0000, CS adjustment will fix it for us
; dl		probable drive number
; ds:si		probable pointer to partition structure
; es:bx		probable pxeenv+ structure
; ss:sp		functional stack

_startup:
; during PXE, CS=0000 and IP=7C00
; adjust CS so our offsets match org setting above
mov ax, _exit
push ax ; store exit addr on stack so main will return to it
push bx ; backup bx
call near .push_ip
.push_ip:
pop bx
sub bx, .push_ip ; subtract expected value ...
shr bx,1 ; shift it to 4 bits to the right
shr bx,1
shr bx,1
shr bx,1
mov ax,cs
add ax,bx ; so we can add it to cs
pop bx ; restore bx
push ax ; cs
mov ax, main
push ax ; ip
sti
retf ; jump

_exit:
  mov si, .message
  call kprintf
  int 0x20
.loop:
  hlt
  jmp .loop
.message:
  db "Halted: Waiting for poweroff...", 0

main:
  call dumpreg
  mov ax,cs
  mov ds,ax
  mov si, string_halt
  call kprintf
.loop:
  hlt
  jmp .loop

%include "dumpreg.asm"
%include "kprintf.asm"