Add exit status to status enum

kernel/context/context.rs

@@ -11,7 +11,7 @@ use super::memory::{Memory, SharedMemory};
 pub enum Status {
     Runnable,
     Blocked,
-    Exited
+    Exited(usize)
 }
 
 /// A context, which identifies either a process or a thread

kernel/context/mod.rs

@@ -57,3 +57,7 @@ pub fn contexts() -> RwLockReadGuard<'static, ContextList> {
 pub fn contexts_mut() -> RwLockWriteGuard<'static, ContextList> {
     CONTEXTS.call_once(init_contexts).write()
 }
+
+pub fn context_id() -> usize {
+    CONTEXT_ID.load(Ordering::SeqCst)
+}