Linux: rseq registration tests

These tests validate that rseq is registered from various execution
contexts (main thread, destructor, other threads, other threads created
from destructor, forked process (without exec), pthread_atfork handlers,
pthread setspecific destructors, signal handlers, atexit handlers).

tst-rseq.c only links against libc.so, testing registration of rseq in
a non-multithreaded environment.

tst-rseq-nptl.c also links against libpthread.so, testing registration
of rseq in a multithreaded environment.

See the Linux kernel selftests for extensive rseq stress-tests.

sysdeps/unix/sysv/linux/Makefile

@@ -100,7 +100,11 @@ tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
 	 test-errno-linux tst-memfd_create tst-mlock2 tst-pkey \
 	 tst-rlimit-infinity tst-ofdlocks tst-gettid tst-gettid-kill \
 	 tst-tgkill
-tests-internal += tst-ofdlocks-compat tst-sigcontext-get_pc
+
+# tst-rseq is an internal test because it requires a definition of __NR_rseq
+# from the internal system call list.
+tests-internal += tst-ofdlocks-compat tst-sigcontext-get_pc \
+		  tst-rseq
 
 CFLAGS-tst-sigcontext-get_pc.c = -fasynchronous-unwind-tables
 
@@ -301,4 +305,8 @@ endif
 
 ifeq ($(subdir),nptl)
 tests += tst-align-clone tst-getpid1
+
+# tst-rseq-nptl is an internal test because it requires a definition of
+# __NR_rseq from the internal system call list.
+tests-internal += tst-rseq-nptl
 endif

sysdeps/unix/sysv/linux/tst-rseq-nptl.c

@@ -0,0 +1,256 @@
+/* Restartable Sequences NPTL test.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   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/>.  */
+
+/* These tests validate that rseq is registered from various execution
+   contexts (main thread, destructor, other threads, other threads created
+   from destructor, forked process (without exec), pthread_atfork handlers,
+   pthread setspecific destructors, signal handlers, atexit handlers).
+
+   See the Linux kernel selftests for extensive rseq stress-tests.  */
+
+#include <stdio.h>
+#include <support/check.h>
+#include <support/xthread.h>
+#include <sys/rseq.h>
+#include <unistd.h>
+
+#ifdef RSEQ_SIG
+# include <array_length.h>
+# include <errno.h>
+# include <error.h>
+# include <pthread.h>
+# include <signal.h>
+# include <stdlib.h>
+# include <string.h>
+# include <support/namespace.h>
+# include <support/xsignal.h>
+# include <syscall.h>
+# include <sys/types.h>
+# include <sys/wait.h>
+# include "tst-rseq.h"
+
+static pthread_key_t rseq_test_key;
+
+static void
+atfork_prepare (void)
+{
+  if (!rseq_thread_registered ())
+    {
+      printf ("error: rseq not registered in pthread atfork prepare\n");
+      support_record_failure ();
+    }
+}
+
+static void
+atfork_parent (void)
+{
+  if (!rseq_thread_registered ())
+    {
+      printf ("error: rseq not registered in pthread atfork parent\n");
+      support_record_failure ();
+    }
+}
+
+static void
+atfork_child (void)
+{
+  if (!rseq_thread_registered ())
+    {
+      printf ("error: rseq not registered in pthread atfork child\n");
+      support_record_failure ();
+    }
+}
+
+static void
+rseq_key_destructor (void *arg)
+{
+  /* Cannot use deferred failure reporting after main returns.  */
+  if (!rseq_thread_registered ())
+    FAIL_EXIT1 ("rseq not registered in pthread key destructor");
+}
+
+static void
+atexit_handler (void)
+{
+  /* Cannot use deferred failure reporting after main returns.  */
+  if (!rseq_thread_registered ())
+    FAIL_EXIT1 ("rseq not registered in atexit handler");
+}
+
+static void
+do_rseq_main_test (void)
+{
+  TEST_COMPARE (atexit (atexit_handler), 0);
+  rseq_test_key = xpthread_key_create (rseq_key_destructor);
+  TEST_COMPARE (pthread_atfork (atfork_prepare, atfork_parent, atfork_child), 0);
+  xraise (SIGUSR1);
+  TEST_COMPARE (pthread_setspecific (rseq_test_key, (void *) 1l), 0);
+  TEST_VERIFY_EXIT (rseq_thread_registered ());
+}
+
+static void
+cancel_routine (void *arg)
+{
+  if (!rseq_thread_registered ())
+    {
+      printf ("error: rseq not registered in cancel routine\n");
+      support_record_failure ();
+    }
+}
+
+static pthread_barrier_t cancel_thread_barrier;
+static pthread_cond_t cancel_thread_cond = PTHREAD_COND_INITIALIZER;
+static pthread_mutex_t cancel_thread_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+static void
+test_cancel_thread (void)
+{
+  pthread_cleanup_push (cancel_routine, NULL);
+  (void) xpthread_barrier_wait (&cancel_thread_barrier);
+  /* Wait forever until cancellation.  */
+  xpthread_cond_wait (&cancel_thread_cond, &cancel_thread_mutex);
+  pthread_cleanup_pop (0);
+}
+
+static void *
+thread_function (void * arg)
+{
+  int i = (int) (intptr_t) arg;
+
+  xraise (SIGUSR1);
+  if (i == 0)
+    test_cancel_thread ();
+  TEST_COMPARE (pthread_setspecific (rseq_test_key, (void *) 1l), 0);
+  return rseq_thread_registered () ? NULL : (void *) 1l;
+}
+
+static void
+sighandler (int sig)
+{
+  if (!rseq_thread_registered ())
+    {
+      printf ("error: rseq not registered in signal handler\n");
+      support_record_failure ();
+    }
+}
+
+static void
+setup_signals (void)
+{
+  struct sigaction sa;
+
+  sigemptyset (&sa.sa_mask);
+  sigaddset (&sa.sa_mask, SIGUSR1);
+  sa.sa_flags = 0;
+  sa.sa_handler = sighandler;
+  xsigaction (SIGUSR1, &sa, NULL);
+}
+
+static int
+do_rseq_threads_test (int nr_threads)
+{
+  pthread_t th[nr_threads];
+  int i;
+  int result = 0;
+
+  xpthread_barrier_init (&cancel_thread_barrier, NULL, 2);
+
+  for (i = 0; i < nr_threads; ++i)
+    th[i] = xpthread_create (NULL, thread_function,
+                             (void *) (intptr_t) i);
+
+  (void) xpthread_barrier_wait (&cancel_thread_barrier);
+
+  xpthread_cancel (th[0]);
+
+  for (i = 0; i < nr_threads; ++i)
+    {
+      void *v;
+
+      v = xpthread_join (th[i]);
+      if (i != 0 && v != NULL)
+        {
+          printf ("error: join %d successful, but child failed\n", i);
+          result = 1;
+        }
+      else if (i == 0 && v == NULL)
+        {
+          printf ("error: join %d successful, child did not fail as expected\n", i);
+          result = 1;
+        }
+    }
+
+  xpthread_barrier_destroy (&cancel_thread_barrier);
+
+  return result;
+}
+
+static void
+subprocess_callback (void *closure)
+{
+  do_rseq_main_test ();
+}
+
+static void
+do_rseq_fork_test (void)
+{
+  support_isolate_in_subprocess (subprocess_callback, NULL);
+}
+
+static int
+do_rseq_test (void)
+{
+  int t[] = { 1, 2, 6, 5, 4, 3, 50 };
+  int i, result = 0;
+
+  if (!rseq_available ())
+    FAIL_UNSUPPORTED ("kernel does not support rseq, skipping test");
+  setup_signals ();
+  xraise (SIGUSR1);
+  do_rseq_main_test ();
+  for (i = 0; i < array_length (t); i++)
+    if (do_rseq_threads_test (t[i]))
+      result = 1;
+  do_rseq_fork_test ();
+  return result;
+}
+
+static void __attribute__ ((destructor))
+do_rseq_destructor_test (void)
+{
+  /* Cannot use deferred failure reporting after main returns.  */
+  if (do_rseq_test ())
+    FAIL_EXIT1 ("rseq not registered within destructor");
+  xpthread_key_delete (rseq_test_key);
+}
+
+#else /* RSEQ_SIG */
+static int
+do_rseq_test (void)
+{
+  FAIL_UNSUPPORTED ("glibc does not define RSEQ_SIG, skipping test");
+  return 0;
+}
+#endif /* RSEQ_SIG */
+
+static int
+do_test (void)
+{
+  return do_rseq_test ();
+}
+
+#include <support/test-driver.c>

sysdeps/unix/sysv/linux/tst-rseq.c

@@ -0,0 +1,64 @@
+/* Restartable Sequences single-threaded tests.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   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/>.  */
+
+/* These tests validate that rseq is registered from main in an executable
+   not linked against libpthread.  */
+
+#include <support/check.h>
+#include <stdio.h>
+#include <sys/rseq.h>
+#include <unistd.h>
+
+#ifdef RSEQ_SIG
+# include <errno.h>
+# include <error.h>
+# include <stdlib.h>
+# include <string.h>
+# include <syscall.h>
+# include "tst-rseq.h"
+
+static void
+do_rseq_main_test (void)
+{
+  TEST_VERIFY_EXIT (rseq_thread_registered ());
+}
+
+static void
+do_rseq_test (void)
+{
+  if (!rseq_available ())
+    {
+      FAIL_UNSUPPORTED ("kernel does not support rseq, skipping test");
+    }
+  do_rseq_main_test ();
+}
+#else /* RSEQ_SIG */
+static void
+do_rseq_test (void)
+{
+  FAIL_UNSUPPORTED ("glibc does not define RSEQ_SIG, skipping test");
+}
+#endif /* RSEQ_SIG */
+
+static int
+do_test (void)
+{
+  do_rseq_test ();
+  return 0;
+}
+
+#include <support/test-driver.c>

sysdeps/unix/sysv/linux/tst-rseq.h

@@ -0,0 +1,59 @@
+/* Restartable Sequences tests header.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   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 <errno.h>
+#include <error.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <support/check.h>
+#include <syscall.h>
+#include <sys/rseq.h>
+
+static inline bool
+rseq_thread_registered (void)
+{
+  int32_t v;
+
+  __atomic_load (&__rseq_abi.cpu_id, &v, __ATOMIC_RELAXED);
+  return v >= 0;
+}
+
+static inline int
+sys_rseq (struct rseq *rseq_abi, uint32_t rseq_len, int flags, uint32_t sig)
+{
+  return syscall (__NR_rseq, rseq_abi, rseq_len, flags, sig);
+}
+
+static inline bool
+rseq_available (void)
+{
+  int rc;
+
+  rc = sys_rseq (NULL, 0, 0, 0);
+  if (rc != -1)
+    FAIL_EXIT1 ("Unexpected rseq return value %d", rc);
+  switch (errno)
+    {
+    case ENOSYS:
+      return false;
+    case EINVAL:
+      /* rseq is implemented, but detected an invalid rseq_len parameter.  */
+      return true;
+    default:
+      FAIL_EXIT1 ("Unexpected rseq error %s", strerror (errno));
+    }
+}