Linux: Add the tgkill function

The tgkill function is sometimes used in crash handlers.

<bits/signal_ext.h> follows the same approach as <bits/unistd_ext.h>
(which was added for the gettid system call wrapper).

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 132 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/tst-tgkill.c b/sysdeps/unix/sysv/linux/tst-tgkill.c
new file mode 100644
index 0000000..818e2f5
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-tgkill.c
@@ -0,0 +1,132 @@
+/* Smoke test for the tgkill system call.
+   Copyright (C) 2019 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <signal.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/xthread.h>
+#include <unistd.h>
+
+/* Number of times sigusr1_handler has been invoked.  */
+static volatile sig_atomic_t signals_delivered;
+
+/* Expected TID of the thread receiving the signal.  */
+static pid_t expected_signal_tid;
+
+static void
+sigusr1_handler (int signo)
+{
+  TEST_COMPARE (expected_signal_tid, gettid ());
+  ++signals_delivered;
+}
+
+struct pid_and_tid
+{
+  pid_t pid;
+  pid_t tid;
+};
+
+/* Send signals from the subprocess which are not expected to be
+   delivered.  There is no handler for SIGUSR2, so delivery will
+   result in a test failure.  CLOSURE must point to a valid PID/TID
+   combination that is still running.  */
+static void
+subprocess_no_tid_match (void *closure)
+{
+  struct pid_and_tid *ids = closure;
+  TEST_COMPARE (tgkill (ids->pid, gettid (), SIGUSR2), -1);
+  TEST_COMPARE (errno, ESRCH);
+
+  TEST_COMPARE (tgkill (getpid (), ids->tid, SIGUSR2), -1);
+  TEST_COMPARE (errno, ESRCH);
+
+  TEST_COMPARE (tgkill (getppid (), gettid (), SIGUSR2), -1);
+  TEST_COMPARE (errno, ESRCH);
+}
+
+/* Called from threadfunc below.  */
+static void
+subprocess (void *closure)
+{
+  int original_tid = expected_signal_tid;
+
+  /* Do not expect that the folloing signals are delivered to the
+     subprocess.  The parent process retains the original
+     expected_signal_tid value.  */
+  expected_signal_tid = 0;
+  TEST_COMPARE (tgkill (getpid (), original_tid, SIGUSR1), -1);
+  TEST_COMPARE (errno, ESRCH);
+  TEST_COMPARE (tgkill (getppid (), gettid (), SIGUSR1), -1);
+  TEST_COMPARE (errno, ESRCH);
+  TEST_COMPARE (expected_signal_tid, 0);
+
+  /* This call has the correct PID/TID combination and is therefore
+     expected to suceed.  */
+  TEST_COMPARE (tgkill (getppid (), original_tid, SIGUSR1), 0);
+}
+
+static void *
+threadfunc (void *closure)
+{
+  TEST_VERIFY (gettid () != getpid ());
+  expected_signal_tid = gettid ();
+  TEST_COMPARE (tgkill (getpid (), gettid (), SIGUSR1), 0);
+  TEST_COMPARE (signals_delivered, 1);
+  signals_delivered = 0;
+
+  support_isolate_in_subprocess (subprocess, NULL);
+
+  /* Check that exactly one signal arrived from the subprocess.  */
+  TEST_COMPARE (signals_delivered, 1);
+
+  support_isolate_in_subprocess (subprocess_no_tid_match,
+                                 &(struct pid_and_tid)
+                                 {
+                                   .pid = getpid (),
+                                   .tid = gettid (),
+                                 });
+
+  support_isolate_in_subprocess (subprocess_no_tid_match,
+                                 &(struct pid_and_tid)
+                                 {
+                                   .pid = getpid (),
+                                   .tid = getpid (),
+                                 });
+
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  TEST_VERIFY_EXIT (signal (SIGUSR1, sigusr1_handler) != SIG_ERR);
+
+  expected_signal_tid = gettid ();
+  TEST_COMPARE (gettid (), getpid ());
+  TEST_COMPARE (tgkill (getpid (), gettid (), SIGUSR1), 0);
+  TEST_COMPARE (signals_delivered, 1);
+  signals_delivered = 0;
+
+  xpthread_join (xpthread_create (NULL, threadfunc, NULL));
+
+  TEST_VERIFY (signal (SIGUSR1, SIG_DFL) == sigusr1_handler);
+  return 0;
+}
+
+#include <support/test-driver.c>