+/* Page directory with kernel mappings only. */
+extern uint32_t *base_page_dir;
+
+/* -o mlfqs:
+ If false (default), use round-robin scheduler.
+ If true, use multi-level feedback queue scheduler. */
+extern bool enable_mlfqs;
+
+#ifdef VM
+/* -o random-paging:
+ If false (default), use LRU page replacement policy.
+ If true, use random page replacement policy. */
+extern bool enable_random_paging;
+#endif
+
+/* -q: Power off when kernel tasks complete? */
+extern bool power_off_when_done;
+
+void power_off (void) NO_RETURN;