[BITS 32] global start start: mov esp, _sys_stack ; This points the stack to our new stack area jmp stublet ; This part MUST be 4byte aligned, so we solve that issue using 'ALIGN 4' ALIGN 4 mboot: ; Multiboot macros to make a few lines later more readable 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 ; This is the GRUB Multiboot header. A boot signature dd MULTIBOOT_HEADER_MAGIC dd MULTIBOOT_HEADER_FLAGS dd MULTIBOOT_CHECKSUM ; AOUT kludge - must be physical addresses. Make a note of these: ; The linker script fills in the data for these ones! dd mboot dd code dd bss dd end dd start