Correct code

bits 32

%include "gdt.inc"
%include "idt.inc"

global start
extern kernelmain

start:
    mov esp, _sys_stack
    jmp stublet

SECTION .multiboot
ALIGN 4
mboot:
    MULTIBOOT_PAGE_ALIGN   equ 1<<0
    MULTIBOOT_MEMORY_INFO   equ 1<<1
    MULTIBOOT_AOUT_KLUDGE   equ 1<<16
    MULTIBOOT_HEADER_MAGIC   equ 0x1BADB002
    MULTIBOOT_HEADER_FLAGS   equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE
    MULTIBOOT_CHECKSUM   equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
    EXTERN code, bss, end

    dd MULTIBOOT_HEADER_MAGIC
    dd MULTIBOOT_HEADER_FLAGS
    dd MULTIBOOT_CHECKSUM

    call InstallGDT

    call kernelmain
stublet:
    jmp $

SECTION .bss
    resb 8192
_sys_stack: