feat(users): per-user sealed folders users/<id>/{home,apps,data,permissions}; storage SET_USER/LOCK/PURGE; init sign-in/sign-out loop (purge fresh/removed/guest, seed from factory, session start/stop); shell logout; pm user+system app shelves; terminal SIGNED_OUT; per-program stack (gatekeeper 12p); 128K load scratch

crates/apps/shell/src/main.rs

@@ -19,11 +19,12 @@ use types::address::VirtualAddress;
 use types::apps::reply;
 use types::bounded::CapSlot;
 
-/// Where init's manifest put them: `uses`, then storage.
+/// Where init's manifest put them: `uses`, then storage, then signing out.
 const TERMINAL: CapSlot = CapSlot::const_new(0);
 const PERMISSION: CapSlot = CapSlot::const_new(1);
-/// The owner's files, `/home`: the shell's `/`.
+/// The user's files, their `home`: the shell's `/`.
 const HOME: CapSlot = CapSlot::const_new(2);
+const SESSION: CapSlot = CapSlot::const_new(3);
 
 /// Bits on the shell's notification: the program died (its death watch is
 /// unbadged), or Ctrl+C was typed (the terminal's copy).
@@ -227,7 +228,7 @@ fn run(sh: &mut Shell, line: &str) {
     match args.first().copied() {
         None => {}
         Some("help") => {
-            println!("built-ins: help, echo <text>, clear, cd <dir>, pwd");
+            println!("built-ins: help, echo <text>, clear, cd <dir>, pwd, logout");
             println!("apps: apps, install <folder>, allow|revoke <app id> <capability>");
             println!("anything else runs an app: try ls, cat readme.txt, snake");
             println!("apps see the current directory, read-only, and only what you allowed");
@@ -244,6 +245,19 @@ fn run(sh: &mut Shell, line: &str) {
         Some("pwd") => println!("{}", sh.cwd),
         Some("echo") => println!("{}", Joined(&args[1..])),
         Some("clear") => libkos::terminal::clear(TERMINAL),
+        // Init stops this shell and everything it ran, and the lock
+        // screen comes back.
+        Some("logout") => {
+            libkos::terminal::clear(TERMINAL);
+            if syscall::send_msg(SESSION, [types::spawn::SIGN_OUT, 0, 0, 0], None).is_err() {
+                println!("logout: cannot sign out");
+                return;
+            }
+            // No prompt over the lock screen: wait to be stopped.
+            loop {
+                let _ = syscall::wait(sh.done);
+            }
+        }
         Some(_) => run_program(sh, args),
     }
 }