Call exit() syscall with return code 42.

exit_x86-linux-intel.s

; exit_x86-linux-intel.s

[SECTION .text]
global _start

_start:
  xor eax,eax     ; zero out eax, no null
  xor ebx,ebx     ; zero out ebx, no null
  mov bl,42       ; return code is 42
  mov al,1        ; exit is syscall 1
  int 0x80        ; syscall interrupt