SO Question 75614053

init_prot:
    ; Since this moment all data segment registers
    ; point to the same data segment in GDT:0x10
    mov ax, GDT_DS_PROT
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov ds, ax
    mov ss, ax

    ; Get 16 bit return address from real mode stack and zero extend it
    ; to 32-bit and place in EAX
    movzx eax, word [esp]

    ; Set up the protected mode stack
    mov esp, STACK_SEGMENT_PROT_MODE
    mov ebp, esp

    ; Push 32-bit return address in EAX onto stack.
    push eax

    xor eax, eax

    ret