BITS 16
org 0x7C00

start:
    cli
    xor ax, ax
    mov ds, ax

    ; Enable A20
    in al, 0x92
    or al, 2
    out 0x92, al

    ; Load GDT
    lgdt [gdt_descriptor]

    ; Enter protected mode
    mov eax, cr0
    or eax, 1
    mov cr0, eax

    jmp 0x08

protected_mode:
    mov ax, 0x10
    mov ds, ax
    mov ss, ax
    mov esp, 0x90000

    ; Jump to kernel at 0x100000
    jmp 0x100000

hang:
    jmp hang

gdt_start:
    dq 0
    dq 0x00CF9A000000FFFF
    dq 0x00CF92000000FFFF
gdt_end:

gdt_descriptor:
    dw gdt_end - gdt_start - 1
    dd gdt_start

times 510-($-$$) db 0
dw 0xAA55