extern crate libc;
use libc::c_void;
use std::mem;

fn main() {
    unsafe {
        let program: *mut u8;
        let page: *mut c_void = libc::mmap(
            ::std::ptr::null_mut(),
            4096,
            libc::PROT_EXEC | libc::PROT_READ | libc::PROT_WRITE,
            libc::MAP_ANONYMOUS | libc::MAP_PRIVATE,
            0,
            0,
        );
        program = mem::transmute(page);

        // mov rax, 14
        // ret
        let p = [0x48, 0xc7, 0xc0, 0x0e, 0x00, 0x00, 0x00, 0xc3].as_ptr();
        program.copy_from_nonoverlapping(p, 8);
        let f: fn() -> i64 = mem::transmute(page);
        let ret = f();
        println!("{}", ret); // => 14
    }
}