generic sys_sigaction() and compat_sys_sigaction()

conditional on OLD_SIGACTION/COMPAT_OLD_SIGACTION

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 0d53ab4..e20b8b4 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -299,6 +299,15 @@
 	compat_uptr_t			list_op_pending;
 };
 
+#ifdef CONFIG_COMPAT_OLD_SIGACTION
+struct compat_old_sigaction {
+	compat_uptr_t			sa_handler;
+	compat_old_sigset_t		sa_mask;
+	compat_ulong_t			sa_flags;
+	compat_uptr_t			sa_restorer;
+};
+#endif
+
 struct compat_statfs;
 struct compat_statfs64;
 struct compat_old_linux_dirent;
@@ -383,6 +392,11 @@
 		const struct compat_sigevent __user *u_event);
 long compat_sys_rt_tgsigqueueinfo(compat_pid_t tgid, compat_pid_t pid, int sig,
 				  struct compat_siginfo __user *uinfo);
+#ifdef CONFIG_COMPAT_OLD_SIGACTION
+asmlinkage long compat_sys_sigaction(int sig,
+                                   const struct compat_old_sigaction __user *act,
+                                   struct compat_old_sigaction __user *oact);
+#endif
 
 static inline int compat_timeval_compare(struct compat_timeval *lhs,
 					struct compat_timeval *rhs)