format binary
use16
org 0x7c00

        jmp near EntryBoot
GDT:
            db 0x0000000000000000 ; null descriptor
    CODE_D  db 0xff,0xff,0x00,0x00,0x00,10011010b,00001111b,0x00 ; code descriptor
    Data_D  db 0xff,0xff,0x00,0x00,0x00,10010010b,00001111b,0x00 ; data descriptor
    VIDEO_D db 0xff,0xff,0x00,0x80,0x0b,10010010b,01000000b,0x00 ; video 0xb8000 descriptor

    len_GDT equ $ - GDT

GDTR:
    dw len_GDT - 1
    dd 0x00000000

EntryBoot:

.clear_screen:

        mov ah,0x02
        xor bh,bh
        xor dx,dx
        int 0x10

        mov ah,0x0a
        mov al,' '
        xor bh,bh
        mov cx,0xffff
        int 0x10

        cli

        in al,0x92
        bts ax,1
        jc .continue_boot
        out 0x92,al
.continue_boot:

        mov dx,cs
        shl edx,4
        add edx,GDT
        mov [GDTR+2],edx

.set_PM:

        lgdt fword [GDTR]

        mov edx,cr0
        or dl,0x01
        mov cr0,edx
        jmp far 0x0008:EntryProtected

use32

EntryProtected:
        hlt
        mov dx,0x0010
        mov ds,dx
        mov ss,dx
        mov es,dx
        mov dx,0x0018
        mov fs,dx
        mov esp,0xffff0000
        mov ebp,esp

.print_status:

        lea esi,[string] ; arg1
        mov ecx,42 ; arg2

        call PrintStatus

        hlt

PrintStatus:

        cld
        xor edi,edi
.lp:
        lodsb
        shl ax,8
        mov al,0x0f
        stosw
        loop .lp

        ret

string db '[+] MBR IN PROTECTED MODE',0x0a,0x0d,'[*] SYSTEM HALT'

times 510 - ($ - $$) db 0x00
dw 0xaa55