kernel.asm

section .data
global Tss

Gdt64:
    dq 0
    dq 0x0020980000000000
    dq 0x0020f80000000000
    dq 0x0000f20000000000
TssDesc:
    dw TssLen-1
    dw 0
    db 0
    db 0x89
    db 0
    db 0
    dq 0

Gdt64Len: equ $-Gdt64

Gdt64Ptr: dw Gdt64Len-1
          dq Gdt64

Tss:
    dd 0
    dq 0xffff800000190000
    times 88 db 0
    dd TssLen

TssLen: equ $-Tss

section .text
extern KMain
global start

start:
    mov rax,Gdt64Ptr
    lgdt [rax]

SetTss:
    mov rax,Tss
    mov rdi,TssDesc
    mov [rdi+2],ax
    shr rax,16
    mov [rdi+4],al
    shr rax,8
    mov [rdi+7],al
    shr rax,8
    mov [rdi+8],eax
    mov ax,0x20
    ltr ax

InitPIT:
    mov al,(1<<2)|(3<<4)
    out 0x43,al

    mov ax,11931
    out 0x40,al
    mov al,ah
    out 0x40,al

InitPIC:
    mov al,0x11
    out 0x20,al
    out 0xa0,al

    mov al,32
    out 0x21,al
    mov al,40
    out 0xa1,al

    mov al,4
    out 0x21,al
    mov al,2
    out 0xa1,al

    mov al,1
    out 0x21,al
    out 0xa1,al

    mov al,11111110b
    out 0x21,al
    mov al,11111111b
    out 0xa1,al

    mov rax,KernelEntry
    push 8
    push rax
    db 0x48
    retf

KernelEntry:
    mov rsp,0xffff800000200000
    call KMain
    
End:
    hlt
    jmp End