new helpers: __save_altstack/__compat_save_altstack, switch x86 and um to those
note that they are relying on access_ok() already checked by caller.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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 */