Question

Why do I get a segmentation fault from the following code?

.text
        .globl  start
start:
        pushq   %rbp
        movq    %rsp, %rbp
        movq    $0xBEEFF00DBEEFF00D, %rax
        pushq   %rax
        movq    $0xF00DBEEFF00DBEEF, %rax
        pushq   %rax
        movq    %rbp, %rsp
        popq    %rbp
        ret

Error:

Segmentation fault: 11

Answer 1

If start is your program’s entry point, you can’t ret to OS; you should _exit.

On Linux (x86-64) which you’re probably using, do this instead of ret:

    movq $60, %rax # %rax = _exit() system call
    xorq %rdi, %rdi # %rdi = 0 normal program return code
    syscall