init: try prefix then / for post-switchroot CWD (/usr is not a chdir target)

init/src/main.rs

@@ -54,19 +54,20 @@ impl InitConfig {
 fn switch_root(unit_store: &mut UnitStore, config: &mut InitConfig, prefix: &Path, etcdir: &Path) {
     status_ok(&format!("switchroot to {} {}", prefix.display(), etcdir.display()));
 
-    // Point init's working directory at the new root. There is no real chroot
-    // in Redox, so without this init's CWD stays unset and every daemon spawned
-    // after the switch inherits an invalid CWD (via AT_REDOX_CWD_FD). That made
-    // getcwd() fail in /usr binaries — e.g. the 00_base-env `zsh -c` setup
-    // service printed "zsh: Failed to get current directory: path invalid" and
-    // then HUNG, so init (which waits on that oneshot) never reached the login
-    // stack (ptyd/getty/login). Establishing a valid CWD here fixes both.
-    if let Err(err) = std::env::set_current_dir(prefix) {
-        init_warn(&format!(
-            "failed to chdir to new root {}: {}",
-            prefix.display(),
-            err
-        ));
+    // Point init's working directory at a valid directory in the new root so
+    // daemons spawned afterwards don't inherit an invalid CWD (via
+    // AT_REDOX_CWD_FD). Without this, getcwd() fails in /usr binaries — e.g.
+    // the 00_base-env `zsh -c` setup printed "zsh: Failed to get current
+    // directory: path invalid" and then hung, so init (which waits on that
+    // oneshot) never reached the login stack. The switch is logical (no
+    // chroot) and `prefix` (e.g. "/usr") is not itself a directory, so try the
+    // plausible roots in order and keep the first that works.
+    let cwd_candidates = [prefix.to_path_buf(), std::path::PathBuf::from("/")];
+    if !cwd_candidates
+        .iter()
+        .any(|cand| std::env::set_current_dir(cand).is_ok())
+    {
+        init_warn("failed to establish a valid working directory after switch_root");
     }
 
     config