rust syscall

syscall_with_rust.rs

#![feature(llvm_asm)]
fn main() {
        let message = String::from("hello world tony!\n");
        syscall(message);
}

#[cfg(target_os = "linux")]
#[inline(never)]
fn syscall(message: String) {
        let msg_ptr = message.as_ptr();
        print!("{:?}\n", msg_ptr);
        let len = message.len();
        print!("len is {:?}\n", len);
        unsafe {
                llvm_asm!("
                mov $$1, %rax # sys call 1 is write on linux
                mov $$1, %rdi # file handle 1 is std out
                mov $0, %rsi # address of string to output
                mov $1, %rdx # number of bytes
                syscall # call the kernel now
                "
                :
                : "r"(msg_ptr), "r"(len)
                : "rax", "rdi", "rsi", "rdx"
                )
        }
}