+extern void protect_control_stack_guard_page(int protect_p);
+extern void protect_control_stack_return_guard_page(int protect_p);
+extern void protect_control_stack_guard_page_thread(int protect_p, struct thread *th);
+extern void protect_control_stack_return_guard_page_thread(int protect_p, struct thread* th);
+extern os_vm_address_t undefined_alien_address;