gistfile1.asm

org 0x0			; offset to 0, we will set segments later

bits 16

jmp main		; Jump to main
main:
	
	;Dont know whats in the segment registers so lets just reload them anyway :)
	xor ax, ax
	mov ds, ax
	mov es, ax
	mov fs, ax
	mov gs, ax
	mov ss, ax
	
	mov ax, 0x9000
	mov ss, ax
	mov sp, 0xFFFF
	
	jmp switch_to_prot

switch_to_prot:

	cli
	;call enableA20
    lgdt[gdtr]
    mov eax, cr0
    or al, 1
    mov cr0, eax
	jmp codeSel:protectedMode

enableA20:
    in al, 0x92
    or al, 2
    out 0x92, al
    ret
	
bits 32
protectedMode:

	cli
	hlt

[bits 16]
gdt dw 0
    dd 0
gdtr:
    dw gdtEnd-gdt-1
    dd gdt
nullSel equ $-gdt
codeSel equ $-gdt
codeGdt
    dw 0x0ffff
    dw 0x0000
    db 0x00
    db 0x09a
    db 0x0cf
    db 0x00
dataSel equ $-gdt
dataGdt
    dw 0x0ffff
    dw 0x0000
    db 0x00
    db 0x092
    db 0x0cf
    db 0x00
videoSel equ $-gdt
    dw 3999
    dw 0x8000
    db 0x0b
    db 0x92
    db 0x00
    db 0x00
gdtEnd
bootingSystem db "Booting process started..", 0dh, 0ah, 0
switching db "Switching to protected mode..", 0dh, 0ah, 0
times 510 - ($ - $$) db 0
dw 0xaa55