extern PML4;
extern PDPT;
extern PD;
extern PT;

[BITS 32]

global mb2_entry;

section .text
align 4

GDT64:
    .Null: equ $ - GDT64
    dw 0
    dw 0
    db 0
    db 0
    db 0
    db 0
    .Code: equ $ - GDT64
    dw 0
    dw 0
    db 0
    db 10011000b
    db 00100000b
    db 0
    .Data: equ $ - GDT64
    dw 0
    dw 0
    db 0
    db 10010000b
    db 00000000b
    db 0
    .Pointer:
    dw $ - GDT64 - 1
    dq GDT64

STACKSIZE   equ 0x1000

mb2_entry:
    mov esp, stack + STACKSIZE
    push eax
    push ebx

    ; set up page table
    mov edi, PML4
    mov cr3, edi
    xor eax, eax
    mov ecx, 4096
    rep stosd

    mov edi, cr3

    mov DWORD [edi], PDPT + 3
    mov edi, PDPT
    mov DWORD [edi], PD + 3
    mov edi, PD
    mov DWORD [edi], PT + 3
    mov edi, PT

    mov ebx, 0x00000003
    mov ecx, 512

.SetEntry:
    mov DWORD [edi], ebx
    add ebx, 0x1000
    add edi, 8
    loop .SetEntry

    mov eax, cr4
    or eax, 1 << 5
    mov cr4, eax

    mov ecx, 0xC0000080
    rdmsr
    or eax, 1 << 8
    wrmsr

    mov eax, cr0
    or eax, 1 << 31
    mov cr0, eax

    pop ebx
    pop eax

    lgdt [GDT64.Pointer]
    jmp GDT64.Code:Realm64
hang:
    hlt
    jmp hang

section .text

[BITS 64]

extern mb2_entry64;

Realm64:
    cli
    mov rdx, rax
    mov rcx, rbx
    mov ax, GDT64.Data
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax

    call mb2_entry64

section .bss
align 4
stack: resb STACKSIZE