Inline intel style assembly and syscalls in mojo.

README.md

Inline assembly and system calls in Mojo

See examples below (May 2026).

main0.mojo

from std.sys._assembly import inlined_assembly
from std.sys import exit

# inline assembly write call

fn main():
  var message = String("Hello World!\n").as_bytes().unsafe_ptr()

  _ = inlined_assembly[
    ".intel_syntax noprefix\n\t"
    "mov rax, 1\n\t"
    "mov rdi, 1\n\t"
    "mov rsi, r8\n\t"
    "mov rdx, 13\n\t"
    "syscall\n\t"
    ".att_syntax prefix",
    Int64,
    constraints="=r,{r8},~{rax},~{rdi},~{rsi},~{rdx},~{rcx},~{r11},~{memory}",
    has_side_effect=True,
  ](message)

  exit(0)

main1.mojo

from std.sys import exit
from std.ffi import external_call

# ffi write call

fn main():
  var message = String("Hello World!\n").as_bytes().unsafe_ptr()

  _ = external_call["write", Int64](Int32(1), message, 13)

  exit(0)