BMOSP/kernel/arch/load_gdt.s

.global load_gdt
load_gdt:
        cli
        lgdt (%rdi)
        movw $0x30, %ax
        mov %ax, %ds
        mov %ax, %es
        mov %ax, %fs
        mov %ax, %gs
        mov %ax, %ss
        pop %rdi
        mov $0x28, %rax
        push %rax
        push %rdi
        retfq