GNU assembler
AT&T syntax
.globl _start
.text
_start:
#
# Load RAX register with syscall number
#
mov $60, %rax # 60 is syscall number for exit()
# mov $231, %rax # 231 is syscall number for exit_group()
#
# Load RDI (first argument), for exit(),
# this is the status code.
#
mov $42, %rdi # exit status code
syscall
Compile this source with
gcc -nostdlib -o prog prog.s
Intel syntax
In order to write an assembler source for the GNU assembler in intel syntax, the
.intel_syntax noprefix directive is required:
.intel_syntax noprefix
.globl _start
.text
_start:
mov rax, 60
mov rdi, 42
syscall
This source is compiled with the exactly same command as the AT&T source.
nasm
section .text
global _start
_start:
mov rax, 60
mov rdi, 42
syscall
Compile and link with the following two commands:
nasm -felf64 prog.nasm -o prog.o
ld prog.o -o prog
The same source can also be compiled with yasm -felf64 ….