signal: Only handle on NSIG signals on signal functions (BZ #25657)

The upper bits of the sigset_t s not fully initialized in the signal
mask calls that return information from kernel (sigprocmask,
sigpending, and pthread_sigmask), since the exported sigset_t size
(1024 bits) is larger than Linux support one (64 or 128 bits).
It might make sigisemptyset/sigorset/sigandset fail if the mask
is filled prior the call.

This patch changes the internal signal function to handle up to
supported Linux signal number (_NSIG), the remaining bits are
untouched.

Checked on x86_64-linux-gnu and i686-linux-gnu.

3 files changed, 102 insertions, 6 deletions

diff --git a/signal/Makefile b/signal/Makefile
index 37de438bba..f3c19e2992 100644
--- a/signal/Makefile
+++ b/signal/Makefile
@@ -49,6 +49,7 @@ tests		:= tst-signal tst-sigset tst-sigsimple tst-raise tst-sigset2 \
 		   tst-sigwait-eintr tst-sigaction \
 		   tst-minsigstksz-1 tst-minsigstksz-2 tst-minsigstksz-3 \
 		   tst-minsigstksz-3a tst-minsigstksz-4 \
+		   tst-sigisemptyset
 
 include ../Rules
 
diff --git a/signal/sigsetops.c b/signal/sigsetops.c
index eb89e6780e..1165377876 100644
--- a/signal/sigsetops.c
+++ b/signal/sigsetops.c
@@ -26,28 +26,28 @@
 
 int
 attribute_compat_text_section
-(__sigismember) (const __sigset_t *set, int sig)
+__sigismember_compat (const __sigset_t *set, int sig)
 {
   return __sigismember (set, sig);
 }
-compat_symbol (libc, __sigismember, __sigismember, GLIBC_2_0);
+compat_symbol (libc, __sigismember_compat, __sigismember, GLIBC_2_0);
 
 int
 attribute_compat_text_section
-(__sigaddset) (__sigset_t *set, int sig)
+__sigaddset_compat (__sigset_t *set, int sig)
 {
   __sigaddset (set, sig);
   return 0;
 }
-compat_symbol (libc, __sigaddset, __sigaddset, GLIBC_2_0);
+compat_symbol (libc, __sigaddset_compat, __sigaddset, GLIBC_2_0);
 
 int
 attribute_compat_text_section
-(__sigdelset) (__sigset_t *set, int sig)
+__sigdelset_compat (__sigset_t *set, int sig)
 {
   __sigdelset (set, sig);
   return 0;
 }
-compat_symbol (libc, __sigdelset, __sigdelset, GLIBC_2_0);
+compat_symbol (libc, __sigdelset_compat, __sigdelset, GLIBC_2_0);
 
 #endif
diff --git a/signal/tst-sigisemptyset.c b/signal/tst-sigisemptyset.c
new file mode 100644
index 0000000000..9ed95496f2
--- /dev/null
+++ b/signal/tst-sigisemptyset.c
@@ -0,0 +1,95 @@
+/* Tests for sigisemptyset/sigorset/sigandset.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <signal.h>
+
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  {
+    sigset_t set;
+    sigemptyset (&set);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  {
+    sigset_t set;
+    sigfillset (&set);
+    TEST_COMPARE (sigisemptyset (&set), 0);
+  }
+
+  {
+    sigset_t setfill, setempty, set;
+    sigfillset (&setfill);
+    sigemptyset (&setempty);
+
+    sigorset (&set, &setfill, &setempty);
+    TEST_COMPARE (sigisemptyset (&set), 0);
+
+    sigandset (&set, &setfill, &setempty);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  /* Ensure current SIG_BLOCK mask empty.  */
+  {
+    sigset_t set;
+    sigemptyset (&set);
+    TEST_COMPARE (sigprocmask (SIG_BLOCK, &set, 0), 0);
+  }
+
+  {
+    sigset_t set;
+    sigemptyset (&set);
+    TEST_COMPARE (sigprocmask (SIG_BLOCK, 0, &set), 0);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  {
+    sigset_t set;
+    sigfillset (&set);
+    TEST_COMPARE (sigprocmask (SIG_BLOCK, 0, &set), 0);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  /* Block all signals.  */
+  {
+    sigset_t set;
+    sigfillset (&set);
+    TEST_COMPARE (sigprocmask (SIG_BLOCK, &set, 0), 0);
+  }
+
+  {
+    sigset_t set;
+    sigemptyset (&set);
+    TEST_COMPARE (sigpending (&set), 0);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  {
+    sigset_t set;
+    sigfillset (&set);
+    TEST_COMPARE (sigpending (&set), 0);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  return 0;
+}
+
+#include <support/test-driver.c>