boot_sect.asm

[org 0x7c00]
KERNEL_OFFSET equ 0x1000

	mov [BOOT_DRIVE], dl

	mov bp, 0x9000
	mov sp, bp

	mov bx, MSG_REAL_MODE
	call print_string
pusha
mov ah, 0x00
mov al, 0x13
int 0x10
popa

	call load_kernel

	call switch_to_pm

	jmp $

%include "print_string.asm"
%include "disk_load.asm"
%include "gdt.asm"
%include "print_string_pm.asm"
%include "switch_to_pm.asm"

[bits 16]

load_kernel:
	mov bx, MSG_LOAD_KERNEL
	call print_string
    mov bx, KERNEL_OFFSET
	mov dh, 15
	mov dl, [BOOT_DRIVE]
	call disk_load

	ret

[bits 32]

BEGIN_PM:
	mov ebx, MSG_PROT_MODE
	call print_string_pm

	call KERNEL_OFFSET

	jmp $

BOOT_DRIVE db 0
MSG_REAL_MODE db "Started in 16-bit Real Mode", 0
MSG_PROT_MODE db "Successfully landed in 32-bit Protected Mode", 0
MSG_LOAD_KERNEL db "Loading kernel into memory", 0

times 510-($-$$) db 0
dw 0xaa55