mulx.asm

use16

org 0x7c00

cli
jmp far 0x0000:_start

gdtd:
dw gdt_end - gdt - 1
dd gdt

gdt:
dq 0

dq 0x00cf9a000000ffff
dq 0x00cf92000000ffff
dq 0x00af9a000000ffff

gdt_end:

_start:
push cs
pop  ds

lgdt [ds:gdtd]

mov eax,cr0
inc eax
mov cr0,eax

jmp 0x08:pm

use32

pm:

mov ax,0x10
mov ds,ax
mov es,ax
mov ss,ax
mov esp,0xa0000

mov eax,cr4
or eax,0x20
mov cr4,eax

mov edi,0x300000

mov eax,0x30100f
stosd
mov ecx,0x03ff
xor eax,eax
rep stosd

mov eax,0x30200f
stosd
mov ecx,0x03ff
xor eax,eax
rep stosd

mov ecx, 0x0200
mov esi, 0x008b

map.loop:
mov eax, esi
stosd
xor eax, eax
stosd
add esi, 0x200000
sub ecx, 1
jnz map.loop

mov eax, 0x300000
mov cr3, eax

mov ecx, 0xC0000080
rdmsr
or eax, 0x00000100
wrmsr

mov eax, cr0
or eax, 0x80000000
mov cr0, eax

jmp 0x18:lm

use64

lm:

; mulx rsp,rsp,rdx
db 0xC4, 0xE2, 0xDB, 0xF6, 0xE2

hlt


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