Better failure detection in getty

src/bin/getty.rs

@@ -3,7 +3,40 @@
 extern crate syscall;
 
 use std::process::Command;
-use std::{env, str};
+use std::{env, process, str};
+use std::io::{self, Write};
+
+fn set_tty(tty: &str) -> syscall::Result<()> {
+    let stdin = syscall::open(tty, syscall::flag::O_RDONLY)?;
+    let stdout = syscall::open(tty, syscall::flag::O_WRONLY)?;
+    let stderr = syscall::open(tty, syscall::flag::O_WRONLY)?;
+
+    syscall::dup2(stdin, 0, &[])?;
+    syscall::dup2(stdout, 1, &[])?;
+    syscall::dup2(stderr, 2, &[])?;
+
+    let _ = syscall::close(stdin);
+    let _ = syscall::close(stdout);
+    let _ = syscall::close(stderr);
+
+    Ok(())
+}
+
+fn daemon() {
+    loop {
+        if clear {
+            syscall::write(1, b"\x1Bc").unwrap();
+        }
+        syscall::fsync(1).unwrap();
+        match Command::new("login").spawn() {
+            Ok(mut child) => match child.wait() {
+                Ok(_status) => (), //println!("getty: waited for login: {:?}", status.code()),
+                Err(err) => panic!("getty: failed to wait for login: {}", err)
+            },
+            Err(err) => panic!("getty: failed to execute login: {}", err)
+        }
+    }
+}
 
 pub fn main() {
     let mut tty_option = None;
@@ -20,13 +53,10 @@ pub fn main() {
     }
 
     if let Some(tty) = tty_option {
-        let _ = syscall::close(2);
-        let _ = syscall::close(1);
-        let _ = syscall::close(0);
-
-        let _ = syscall::open(&tty, syscall::flag::O_RDWR);
-        let _ = syscall::open(&tty, syscall::flag::O_RDWR);
-        let _ = syscall::open(&tty, syscall::flag::O_RDWR);
+        if let Err(err) = set_tty(&tty) {
+            writeln!(io::stderr(), "getty: failed to open TTY {}: {}", tty, err).unwrap();
+            process::exit(1);
+        }
 
         env::set_var("TTY", &tty);
         {
@@ -44,19 +74,7 @@ pub fn main() {
         }
 
         if unsafe { syscall::clone(0).unwrap() } == 0 {
-            loop {
-                if clear {
-                    syscall::write(1, b"\x1Bc").unwrap();
-                }
-                syscall::fsync(1).unwrap();
-                match Command::new("login").spawn() {
-                    Ok(mut child) => match child.wait() {
-                        Ok(_status) => (), //println!("getty: waited for login: {:?}", status.code()),
-                        Err(err) => panic!("getty: failed to wait for login: {}", err)
-                    },
-                    Err(err) => panic!("getty: failed to execute login: {}", err)
-                }
-            }
+            daemon();
         }
     } else {
         panic!("getty: no tty provided");