; assumptions about the starting envionment
cpu 8086
org 0x0000
; es:bx		pxeenv+ structure
; ss:sp		functional stack

_startup:
  xor ax, ax
  mov ax, cs
  cmp ax, 0x0000 ; MBR or NBP, CS=0000 IP=7C00
  je .mbr
  cmp ax, 0x07C0 ;  MBR on weird BIOS, CS=07C0 IP=0000
  je .mbr
.dos:
  mov ax, cs
  push ax ; return CS
  mov ax, .dosret
  add ax, 0x0100
  push ax ; return IP

  mov ax, cs
  add ax, 0x0010
  push ax ; main CS
  mov ax, main
  push ax ; main IP
  retf
.dosret:
  int 0x20
  int 0x18
.mbr:
  mov ax, 0x0050
  mov ds, ax
  mov [0xFFFE], ss ; save current stack configuration onto new stack
  mov [0xFFFC], sp
  mov ss, ax
  mov sp, 0xFFFC

  push dx
  push bx ; possible far ptr to pxeenv+ struct
  push es

  mov es, ax ; 0x0050
  mov di, 0x0000

  xor ax, ax
  mov ds, ax
  mov si, 0x7C00

  mov cx, _reloc_end
  rep movsb

  call 0x0050:main
.halt:
  hlt
  jmp .halt

%include "kernel/main.asm"

_reloc_end: