linux: Add maintenance commands to test libthread_db

This commit adds two new commands which may be used to test thread
debugging libraries used by GDB:

  * "maint check libthread-db" tests the thread debugging library GDB
     is using for the current inferior.

  * "maint set/show check-libthread-db" selects whether libthread_db
     tests should be run automatically as libthread_db is auto-loaded.
     The default is to not run tests automatically.

The test itself is a basic integrity check exercising all libthread_db
functions used by GDB on GNU/Linux systems.  By extension this also
exercises the proc_service functions provided by GDB that libthread_db
uses.

This functionality is useful for NPTL developers and libthread_db
developers.  It could also prove useful investigating bugs reported
against GDB where the thread debugging library or GDB's proc_service
layer is suspect.

gdb/ChangeLog:

	* linux-thread-db.c (valprint.h): New include.
	(struct check_thread_db_info): New structure.
	(check_thread_db_on_load, tdb_testinfo): New static globals.
	(check_thread_db, check_thread_db_callback): New functions.
	(try_thread_db_load_1): Run integrity checks if requested.
	(maintenance_check_libthread_db): New function.
	(_initialize_thread_db): Register "maint check libthread-db"
	and "maint set/show check-libthread-db".
	* NEWS: Mention the above new commands.

gdb/doc/ChangeLog:

	* gdb.texinfo (Maintenance Commands): Document "maint check
	libthread-db" and "maint set/show check-libthread-db".

gdb/testsuite/ChangeLog:

	* gdb.threads/check-libthread-db.exp: New file.
	* gdb.threads/check-libthread-db.c: Likewise.

2 files changed, 181 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.threads/check-libthread-db.c b/gdb/testsuite/gdb.threads/check-libthread-db.c
new file mode 100644
index 0000000..85a97a9
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/check-libthread-db.c
@@ -0,0 +1,67 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2017-2018 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <errno.h>
+
+static void
+break_here (void)
+{
+}
+
+static void *
+thread_routine (void *arg)
+{
+  errno = 42;
+
+  break_here ();
+
+  while (1)
+    sleep (1);
+
+  return NULL;
+}
+
+int
+main (int argc, char *argv)
+{
+  pthread_t the_thread;
+  int err;
+
+  err = pthread_create (&the_thread, NULL, thread_routine, NULL);
+  if (err != 0)
+    {
+      fprintf (stderr, "pthread_create: %s (%d)\n", strerror (err), err);
+      exit (EXIT_FAILURE);
+    }
+
+  errno = 23;
+
+  err = pthread_join (the_thread, NULL);
+  if (err != 0)
+    {
+      fprintf (stderr, "pthread_join: %s (%d)\n", strerror (err), err);
+      exit (EXIT_FAILURE);
+    }
+
+  exit (EXIT_SUCCESS);
+}
diff --git a/gdb/testsuite/gdb.threads/check-libthread-db.exp b/gdb/testsuite/gdb.threads/check-libthread-db.exp
new file mode 100644
index 0000000..ddd9c27
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/check-libthread-db.exp
@@ -0,0 +1,114 @@
+# Copyright 2017-2018 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This test only works for native processes on GNU/Linux.
+if {[target_info gdb_protocol] != "" || ![istarget *-linux*]} {
+    continue
+}
+
+standard_testfile
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
+	 executable debug] != "" } {
+    return -1
+}
+
+with_test_prefix "user-initiated check" {
+
+    # User-initiated check with libthread_db not loaded.
+    clean_restart ${binfile}
+
+    gdb_test "maint show check-libthread-db" \
+	"Whether to check libthread_db at load time is off."
+
+    gdb_test_no_output "set stop-on-solib-events 1"
+    gdb_run_cmd
+    gdb_test "" \
+	".*Stopped due to shared library event.*no libraries added or removed.*"
+
+    gdb_test "maint check libthread-db" \
+	"No libthread_db loaded" \
+	"no libpthread.so loaded"
+
+
+    # User-initiated check with NPTL uninitialized.
+    # libthread_db should fake a single thread with th_unique == NULL.
+    gdb_test "continue" \
+	".*Stopped due to shared library event.*Inferior loaded .*libpthread.*"
+
+    gdb_test_sequence "maint check libthread-db" \
+	"libpthread.so not initialized" {
+	    "\[\r\n\]+Running libthread_db integrity checks:"
+	    "\[\r\n\]+\[ \]+Got thread 0x0 => \[0-9\]+ => 0x0 ... OK"
+	    "\[\r\n\]+libthread_db integrity checks passed."
+	}
+
+    # User-initiated check with NPTL fully operational.
+    gdb_test_no_output "set stop-on-solib-events 0"
+    gdb_breakpoint break_here
+    gdb_continue_to_breakpoint break_here
+
+    gdb_test_sequence "maint check libthread-db" \
+	"libpthread.so fully initialized" {
+	    "\[\r\n\]+Running libthread_db integrity checks:"
+	    "\[\r\n\]+\[ \]+Got thread 0x\[1-9a-f\]\[0-9a-f\]+ => \[0-9\]+ => 0x\[1-9a-f\]\[0-9a-f\]+; errno = 23 ... OK"
+	    "\[\r\n\]+\[ \]+Got thread 0x\[1-9a-f\]\[0-9a-f\]+ => \[0-9\]+ => 0x\[1-9a-f\]\[0-9a-f\]+; errno = 42 ... OK"
+	    "\[\r\n\]+libthread_db integrity checks passed."
+	}
+}
+
+with_test_prefix "automated load-time check" {
+
+    # Automated load-time check with NPTL uninitialized.
+    with_test_prefix "libpthread.so not initialized" {
+	clean_restart ${binfile}
+
+	gdb_test_no_output "maint set check-libthread-db 1"
+	gdb_test_no_output "set debug libthread-db 1"
+	gdb_breakpoint break_here
+	gdb_run_cmd
+
+	gdb_test_sequence "" \
+	    "check debug libthread-db output" {
+		"\[\r\n\]+Running libthread_db integrity checks:"
+		"\[\r\n\]+\[ \]+Got thread 0x0 => \[0-9\]+ => 0x0 ... OK"
+		"\[\r\n\]+libthread_db integrity checks passed."
+		"\[\r\n\]+[Thread debugging using libthread_db enabled]"
+	    }
+    }
+
+    # Automated load-time check with NPTL fully operational.
+    with_test_prefix "libpthread.so fully initialized" {
+	clean_restart ${binfile}
+
+	gdb_test_no_output "maint set check-libthread-db 1"
+	gdb_test_no_output "set debug libthread-db 1"
+
+	set test_spawn_id [spawn_wait_for_attach $binfile]
+	set testpid [spawn_id_get_pid $test_spawn_id]
+
+	gdb_test_sequence "attach $testpid" \
+	    "check debug libthread-db output" {
+		"\[\r\n\]+Running libthread_db integrity checks:"
+		"\[\r\n\]+\[ \]+Got thread 0x\[1-9a-f\]\[0-9a-f\]+ => \[0-9\]+ => 0x\[1-9a-f\]\[0-9a-f\]+ ... OK"
+		"\[\r\n\]+\[ \]+Got thread 0x\[1-9a-f\]\[0-9a-f\]+ => \[0-9\]+ => 0x\[1-9a-f\]\[0-9a-f\]+ ... OK"
+		"\[\r\n\]+libthread_db integrity checks passed."
+		"\[\r\n\]+[Thread debugging using libthread_db enabled]"
+	    }
+
+	gdb_exit
+	kill_wait_spawned_process $test_spawn_id
+    }
+}