login: DIAGNOSTIC — spawn login shell without namespace restriction

Getty forwards console input to the pty master correctly (verified), and
login reads the username fine, but after apply_login_schemes() restricts
the namespace the interactive shell's pty-slave read never returns the
forwarded input. Temporarily skip the restriction to confirm it is the
cause. Also removes the getty forward diagnostic.

src/bin/getty.rs

@@ -67,7 +67,6 @@ pub fn handle(
                     Err(ref err) if err.errno() == EAGAIN => break,
                     Err(_) => panic!("getty: failed to read from TTY"),
                 };
-                eprintln!("getty-diag: fwd {count} bytes tty->pty {:?}", &packet[..count.min(24)]);
                 redox::write(master_fd as usize, &packet[..count])
                     .expect("getty: failed to write master PTY");
             }

src/bin/login.rs

@@ -176,19 +176,16 @@ pub fn main() {
                             stdout.flush().r#try(&mut stderr);
                         }
 
-                        let before_ns_fd =
-                            apply_login_schemes(user, &DEFAULT_SCHEMES).unwrap_or_exit(1);
-
-                        let _ = syscall::fcntl(
-                            before_ns_fd.raw(),
-                            syscall::F_SETFD,
-                            syscall::O_CLOEXEC,
-                        );
+                        // DIAGNOSTIC: temporarily skip the login namespace
+                        // restriction (apply_login_schemes). After its setns(),
+                        // the interactive shell's pty-slave stdin stops
+                        // receiving input forwarded to the pty master (getty
+                        // forwards it, but the slave read never returns it), so
+                        // the shell can never read a command. Spawn the shell in
+                        // the inherited namespace to test whether the
+                        // restriction is the cause.
+                        let _ = apply_login_schemes; // keep import used
                         spawn_shell(user).unwrap_or_exit(1);
-                        let _ = syscall::fcntl(before_ns_fd.raw(), syscall::F_SETFD, 0);
-                        let _ = libredox::call::close(
-                            libredox::call::setns(before_ns_fd.into_raw()).unwrap_or_exit(1),
-                        );
                         break;
                     }