Luna/kernel/src/arch/x86_64/CPU.asm

global enable_sse
enable_sse:
    mov rax, cr0
    and ax, 0xFFFB		;clear coprocessor emulation CR0.EM
    or ax, 0x2			;set coprocessor monitoring  CR0.MP
    mov cr0, rax
    mov rax, cr4
    or ax, 3 << 9		;set CR4.OSFXSR and CR4.OSXMMEXCPT at the same time
    mov cr4, rax
    ret

global enable_write_protect
enable_write_protect:
    mov rax, cr0
    or eax, 0x80000 ;set write-protect CR0.WP
    mov cr0, rax
    ret

global enable_nx
enable_nx:
    mov rcx, 0xC0000080 ; IA32_EFER
    rdmsr
    or eax, 1 << 11 ; no-execute enable (NXE)
    wrmsr
    ret

global load_gdt
load_gdt:
    cli
    lgdt [rdi]
    mov   ax, 0x10
    mov   ds, ax
    mov   es, ax
    mov   fs, ax
    mov   gs, ax
    mov   ss, ax
    push 0x08                 
    lea rax, [rel .reload_CS]
    push rax
    retfq
.reload_CS:
    ret

global load_tr
load_tr:
    mov rax, rdi
    ltr ax
    ret