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/kernel/signal.c b/kernel/signal.c
index f3665f3..79998f5 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3409,6 +3409,84 @@
 #endif
 #endif /* !CONFIG_ODD_RT_SIGACTION */
 
+#ifdef CONFIG_OLD_SIGACTION
+SYSCALL_DEFINE3(sigaction, int, sig,
+		const struct old_sigaction __user *, act,
+	        struct old_sigaction __user *, oact)
+{
+	struct k_sigaction new_ka, old_ka;
+	int ret;
+
+	if (act) {
+		old_sigset_t mask;
+		if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
+		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
+		    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
+		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
+		    __get_user(mask, &act->sa_mask))
+			return -EFAULT;
+#ifdef __ARCH_HAS_KA_RESTORER
+		new_ka.ka_restorer = NULL;
+#endif
+		siginitset(&new_ka.sa.sa_mask, mask);
+	}
+
+	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
+
+	if (!ret && oact) {
+		if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
+		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
+		    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
+		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
+		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
+			return -EFAULT;
+	}
+
+	return ret;
+}
+#endif
+#ifdef CONFIG_COMPAT_OLD_SIGACTION
+COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
+		const struct compat_old_sigaction __user *, act,
+	        struct compat_old_sigaction __user *, oact)
+{
+	struct k_sigaction new_ka, old_ka;
+	int ret;
+	compat_old_sigset_t mask;
+	compat_uptr_t handler, restorer;
+
+	if (act) {
+		if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
+		    __get_user(handler, &act->sa_handler) ||
+		    __get_user(restorer, &act->sa_restorer) ||
+		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
+		    __get_user(mask, &act->sa_mask))
+			return -EFAULT;
+
+#ifdef __ARCH_HAS_KA_RESTORER
+		new_ka.ka_restorer = NULL;
+#endif
+		new_ka.sa.sa_handler = compat_ptr(handler);
+		new_ka.sa.sa_restorer = compat_ptr(restorer);
+		siginitset(&new_ka.sa.sa_mask, mask);
+	}
+
+	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
+
+	if (!ret && oact) {
+		if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
+		    __put_user(ptr_to_compat(old_ka.sa.sa_handler),
+			       &oact->sa_handler) ||
+		    __put_user(ptr_to_compat(old_ka.sa.sa_restorer),
+			       &oact->sa_restorer) ||
+		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
+		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
+			return -EFAULT;
+	}
+	return ret;
+}
+#endif
+
 #ifdef __ARCH_WANT_SYS_SGETMASK
 
 /*