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; Cheers to wiki.osdev.org for this quick starter. It really helped me
; get a prototype off the ground quickly without pissing around
; Declare constants used for creating a multiboot header.
MBALIGN equ 1<<0 ; align loaded modules on page boundaries
MEMINFO equ 1<<1 ; provide memory map
FLAGS equ MBALIGN | MEMINFO ; this is the Multiboot 'flag' field
MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header
CHECKSUM equ -(MAGIC + FLAGS) ; checksum of above, to prove we are multiboot
; Declare a header as in the Multiboot Standard. We put this into a special
; section so we can force the header to be in the start of the final program.
; You don't need to understand all these details as it is just magic values that
; is documented in the multiboot standard. The bootloader will search for this
; magic sequence and recognize us as a multiboot kernel.
section .multiboot
align 4
dd MAGIC
dd FLAGS
dd CHECKSUM
; Currently the stack pointer register (esp) points at anything and using it may
; cause massive harm. Instead, we'll provide our own stack. We will allocate
; room for a small temporary stack by creating a symbol at the bottom of it,
; then allocating 16384 bytes for it, and finally creating a symbol at the top.
section .bootstrap_stack
align 4
stack_bottom:
times 16384 db 0
stack_top:
; The linker script specifies _start as the entry point to the kernel and the
; bootloader will jump to this position once the kernel has been loaded. It
; doesn't make sense to return from this function as the bootloader is gone.
section .text
global _start
_start:
extern kernel_main
extern console_print
extern console_set_colors
mov esp, stack_top
call kernel_main
; Let the user know that kernel_main() exited
push word 0x0007
call console_set_colors
push mainexit
call console_print
cli
.hang:
hlt
jmp .hang
mainexit db 10,"asm: kernel_main() exited",0
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