diff --git a/include/linux/signal.h b/include/linux/signal.h
index 5969522..0a89ffc 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -386,5 +386,6 @@
 void signals_init(void);
 
 int restore_altstack(const stack_t __user *);
+int __save_altstack(stack_t __user *, unsigned long);
 
 #endif /* _LINUX_SIGNAL_H */