getty: harden the console<->PTY bridge against transient read/write/event errors (log-and-continue instead of panic; a panic here killed the live shell's I/O)

src/bin/getty.rs

@@ -58,6 +58,10 @@ pub fn handle(
     // master_fd => PTY
 
     let handle_event = |event_id: usize| {
+        // The console<->PTY bridge must never panic on a transient read/write
+        // error: getty runs this while the login shell is alive, so a panic here
+        // kills the shell's I/O forwarding (input stops, output stops). Log and
+        // stop the current forwarding cycle instead; the event loop keeps going.
         if event_id as RawFd == tty_fd {
             let mut packet = [0; 4096];
             loop {
@@ -65,10 +69,15 @@ pub fn handle(
                     Ok(0) => return,
                     Ok(count) => count,
                     Err(ref err) if err.errno() == EAGAIN => break,
-                    Err(_) => panic!("getty: failed to read from TTY"),
+                    Err(err) => {
+                        eprintln!("getty: failed to read from TTY: {err}");
+                        return;
+                    }
                 };
-                redox::write(master_fd as usize, &packet[..count])
-                    .expect("getty: failed to write master PTY");
+                if let Err(err) = redox::write(master_fd as usize, &packet[..count]) {
+                    eprintln!("getty: failed to write master PTY: {err}");
+                    break;
+                }
             }
         } else if event_id as RawFd == master_fd {
             let mut packet = [0; 4096];
@@ -77,10 +86,15 @@ pub fn handle(
                     Ok(0) => return,
                     Ok(count) => count,
                     Err(ref err) if err.errno() == EAGAIN => break,
-                    Err(_) => panic!("getty: failed to read from master TTY"),
+                    Err(err) => {
+                        eprintln!("getty: failed to read from master PTY: {err}");
+                        return;
+                    }
                 };
-                redox::write(tty_fd as usize, &packet[1..count])
-                    .expect("getty: failed to write to TTY");
+                if let Err(err) = redox::write(tty_fd as usize, &packet[1..count]) {
+                    eprintln!("getty: failed to write to TTY: {err}");
+                    break;
+                }
                 if packet[0] & 1 == 1 {
                     let _ = redox::fsync(tty_fd as usize);
                 }
@@ -92,26 +106,36 @@ pub fn handle(
     handle_event(master_fd as usize);
 
     'events: loop {
-        let sys_event = event_queue
-            .next()
-            .expect("getty: event queue stopped")
-            .expect("getty: failed to read event file");
+        let sys_event = match event_queue.next() {
+            Some(Ok(event)) => event,
+            Some(Err(err)) => {
+                eprintln!("getty: failed to read event file: {err}; exiting bridge");
+                break 'events;
+            }
+            None => {
+                eprintln!("getty: event queue stopped; exiting bridge");
+                break 'events;
+            }
+        };
         handle_event(sys_event.fd);
 
         match process.try_wait() {
-            Ok(status) => match status {
-                Some(_code) => break 'events,
-                None => (),
-            },
+            Ok(Some(_code)) => break 'events,
+            Ok(None) => (),
             Err(err) => match err.kind() {
                 ErrorKind::WouldBlock => (),
-                _ => panic!("getty: failed to wait on child: {:?}", err),
+                _ => {
+                    eprintln!("getty: failed to wait on child: {err:?}; exiting bridge");
+                    break 'events;
+                }
             },
         }
     }
 
     let _ = process.kill();
-    process.wait().expect("getty: failed to wait on login");
+    if let Err(err) = process.wait() {
+        eprintln!("getty: failed to wait on login: {err}");
+    }
 }
 
 pub fn getpty(columns: u16, lines: u16) -> (RawFd, String) {