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initial commit with code from http://wiki.osdev.org/Bare_bones
author meillo@marmaro.de
date Sun, 01 Nov 2009 23:50:00 +0100
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global loader           ; making entry point visible to linker
extern kmain             ; main is defined elsewhere

; setting up the Multiboot header - see GRUB docs for details
MODULEALIGN equ  1<<0                   ; align loaded modules on page
; boundaries
MEMINFO     equ  1<<1                   ; provide memory map
FLAGS       equ  MODULEALIGN | MEMINFO  ; this is the Multiboot 'flag' field
MAGIC       equ    0x1BADB002           ; 'magic number' lets bootloader find the header
CHECKSUM    equ  -(MAGIC + FLAGS)       ; checksum required

section .multiboot
align 4
MultiBootHeader:
   dd MAGIC
   dd FLAGS
   dd CHECKSUM

; reserve initial kernel stack space
STACKSIZE equ 0x4000                  ; that's 16k.

loader:
   mov esp, stack+STACKSIZE           ; set up the stack
   push eax                           ; pass Multiboot magic number
   push ebx                           ; pass Multiboot info structure
   call kmain                          ; call kernel proper
   cli
hang:
   hlt                                ; halt machine should kernel return
   jmp   hang

section .bss
align 32
stack:
   resb STACKSIZE                     ; reserve stack on a quadword boundary