Implement the exit system call, w/ E

src/userprog/syscall.c

@@ -99,9 +99,12 @@ halt (void)
 }
 
 static void
-exit (int status UNUSED)
+exit (int status)
 {
-  //TODO
+  /* Sets exit_status of the thread to status. thread_exit () will call
+     process_exit () if user programs are allowed. */
+  thread_current ()->exit_status = status;
+  thread_exit ();
 }
 
 static pid_t