[PATCH] linux: Add maintenance commands to test libthread_db

[PATCH] linux: Add maintenance commands to test libthread_db

[Gary Benson]

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.

Built and regtested on RHEL 7.4 x86_64.

Ok to commit?

Thanks,
Gary

--
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".

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.
---
 gdb/ChangeLog                                    |  11 +
 gdb/doc/ChangeLog                                |   5 +
 gdb/doc/gdb.texinfo                              |  13 ++
 gdb/linux-thread-db.c                            | 257 +++++++++++++++++++++++
 gdb/testsuite/ChangeLog                          |   5 +
 gdb/testsuite/gdb.threads/check-libthread-db.c   |  66 ++++++
 gdb/testsuite/gdb.threads/check-libthread-db.exp | 114 ++++++++++
 7 files changed, 471 insertions(+)
 create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.c
 create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.exp

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 29d4789..4d7a7b1 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -34981,6 +34981,11 @@ modify XML target descriptions.
 Check that the target descriptions dynamically created by @value{GDBN}
 equal the descriptions created from XML files found in @var{dir}.
 
+@kindex maint check libthread-db
+@item maint check libthread-db
+Run integrity checks on the current inferior's thread debugging
+library.
+
 @kindex maint print dummy-frames
 @item maint print dummy-frames
 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
@@ -35288,6 +35293,14 @@ number of blocks in the blockvector
 @end enumerate
 @end table
 
+@kindex maint set check-libthread-db
+@kindex maint show check-libthread-db
+@item maint set check-libthread-db [on|off]
+@itemx maint show check-libthread-db
+Control whether @value{GDBN} should run integrity checks on inferior
+specific thread debugging libraries as they are loaded.  The default
+is not to perform such checks.
+
 @kindex maint space
 @cindex memory used by commands
 @item maint space @var{value}
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index ea032fc..d1fdb33 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -46,6 +46,7 @@
 #include <ctype.h>
 #include "nat/linux-namespaces.h"
 #include <algorithm>
+#include "valprint.h"
 
 /* GNU/Linux libthread_db support.
 
@@ -80,6 +81,10 @@ static char *libthread_db_search_path;
    by the "set auto-load libthread-db" command.  */
 static int auto_load_thread_db = 1;
 
+/* Set to non-zero if load-time libthread_db tests have been enabled
+   by the "maintenence set check-libthread-db" command.  */
+static int check_thread_db_on_load = 0;
+
 /* "show" command for the auto_load_thread_db configuration variable.  */
 
 static void
@@ -493,6 +498,216 @@ dladdr_to_soname (const void *addr)
   return NULL;
 }
 
+/* State for check_thread_db_callback.  */
+
+struct check_thread_db_info
+{
+  /* The libthread_db under test.  */
+  struct thread_db_info *info;
+
+  /* True if progress should be logged.  */
+  bool log_progress;
+
+  /* True if the callback was called.  */
+  bool threads_seen;
+};
+
+static struct check_thread_db_info *tdb_testinfo;
+
+/* Callback for check_thread_db.  */
+
+static int
+check_thread_db_callback (const td_thrhandle_t *th, void *arg)
+{
+  gdb_assert (tdb_testinfo != NULL);
+  tdb_testinfo->threads_seen = true;
+
+#define LOG(fmt, args...)						\
+  do									\
+    {									\
+      if (tdb_testinfo->log_progress)					\
+	{								\
+	  debug_printf (fmt, ## args);					\
+	  gdb_flush (gdb_stdlog);					\
+	}								\
+    }									\
+  while (0)
+
+#define __CHECK(expr, args...)						\
+  do									\
+    {									\
+      if (!(expr))							\
+	{								\
+	  LOG (" ... FAIL!\n");						\
+	  error (args);							\
+	}								\
+    }									\
+  while (0)
+
+#define CHECK(expr)							\
+  __CHECK (expr, "(%s) == false", #expr)
+
+#define CHECK_CALL(func, args...)					\
+  do									\
+    {									\
+      td_err_e __err = tdb_testinfo->info->func ## _p (args);		\
+									\
+      __CHECK (__err == TD_OK, _("%s failed: %s"), #func,		\
+	       thread_db_err_str (__err));				\
+    }									\
+  while (0)
+
+  LOG ("  Got thread");
+
+  /* Check td_ta_thr_iter passed consistent arguments.  */
+  CHECK (th != NULL);
+  CHECK (arg == (void *) tdb_testinfo);
+  CHECK (th->th_ta_p == tdb_testinfo->info->thread_agent);
+
+  LOG (" %s", core_addr_to_string_nz ((CORE_ADDR) th->th_unique));
+
+  /* Check td_thr_get_info.  */
+  td_thrinfo_t ti;
+  CHECK_CALL (td_thr_get_info, th, &ti);
+
+  LOG (" => %d", ti.ti_lid);
+
+  CHECK (ti.ti_ta_p == th->th_ta_p);
+  CHECK (ti.ti_tid == (thread_t) th->th_unique);
+
+  /* Check td_ta_map_lwp2thr.  */
+  td_thrhandle_t th2;
+  memset (&th2, 23, sizeof (td_thrhandle_t));
+  CHECK_CALL (td_ta_map_lwp2thr, th->th_ta_p, ti.ti_lid, &th2);
+
+  LOG (" => %s", core_addr_to_string_nz ((CORE_ADDR) th2.th_unique));
+
+  CHECK (memcmp (th, &th2, sizeof (td_thrhandle_t)) == 0);
+
+  /* Attempt TLS access.  Assuming errno is TLS, this calls
+     thread_db_get_thread_local_address, which in turn calls
+     td_thr_tls_get_addr for live inferiors or td_thr_tlsbase
+     for core files.  This test is skipped if the thread has
+     not been recorded; proceeding in that case would result
+     in the test having the side-effect of noticing threads
+     which seems wrong.
+
+     Note that in glibc's libthread_db td_thr_tls_get_addr is
+     a thin wrapper around td_thr_tlsbase; this check always
+     hits the bulk of the code.
+
+     Note also that we don't actually check any libthread_db
+     calls are made, we just assume they were; future changes
+     to how GDB accesses TLS could result in this passing
+     without exercising the calls it's supposed to.  */
+  ptid_t ptid = ptid_build (tdb_testinfo->info->pid, ti.ti_lid, 0);
+  struct thread_info *thread_info = find_thread_ptid (ptid);
+  if (thread_info != NULL && thread_info->priv != NULL)
+    {
+      LOG ("; errno");
+
+      scoped_restore_current_thread restore_current_thread;
+      switch_to_thread (ptid);
+
+      expression_up expr = parse_expression ("errno");
+      struct value *val = evaluate_expression (expr.get ());
+
+      if (tdb_testinfo->log_progress)
+	{
+	  struct value_print_options opts;
+
+	  get_user_print_options (&opts);
+	  LOG (" = ");
+	  value_print (val, gdb_stdlog, &opts);
+	}
+    }
+
+  LOG (" ... OK\n");
+
+#undef LOG
+#undef __CHECK
+#undef CHECK
+#undef CHECK_CALL
+
+  return 0;
+}
+
+/* Run integrity checks on the dlopen()ed libthread_db described by
+   INFO.  Returns true on success, displays a warning and returns
+   false on failure.  Logs progress messages to gdb_stdlog during
+   the test if LOG_PROGRESS is true.  */
+
+static bool
+check_thread_db (struct thread_db_info *info, bool log_progress)
+{
+  bool test_passed = true;
+
+  if (log_progress)
+    debug_printf (_("Running libthread_db integrity checks:\n"));
+
+  /* GDB avoids using td_ta_thr_iter wherever possible (see comment
+     in try_thread_db_load_1 below) so in order to test it we may
+     have to locate it ourselves.  */
+  td_ta_thr_iter_ftype *td_ta_thr_iter_p = info->td_ta_thr_iter_p;
+  if (td_ta_thr_iter_p == NULL)
+    {
+      void *thr_iter = verbose_dlsym (info->handle, "td_ta_thr_iter");
+      if (thr_iter == NULL)
+	return 0;
+
+      td_ta_thr_iter_p = (td_ta_thr_iter_ftype *) thr_iter;
+    }
+
+  /* Set up the test state we share with the callback.  */
+  gdb_assert (tdb_testinfo == NULL);
+  struct check_thread_db_info tdb_testinfo_buf;
+  tdb_testinfo = &tdb_testinfo_buf;
+
+  memset (tdb_testinfo, 0, sizeof (struct check_thread_db_info));
+  tdb_testinfo->info = info;
+  tdb_testinfo->log_progress = log_progress;
+
+  /* td_ta_thr_iter shouldn't be used on running processes.  */
+  linux_stop_and_wait_all_lwps ();
+
+  TRY
+    {
+      td_err_e err = td_ta_thr_iter_p (info->thread_agent,
+				       check_thread_db_callback,
+				       tdb_testinfo,
+				       TD_THR_ANY_STATE,
+				       TD_THR_LOWEST_PRIORITY,
+				       TD_SIGNO_MASK,
+				       TD_THR_ANY_USER_FLAGS);
+
+      if (err != TD_OK)
+	error (_("td_ta_thr_iter failed: %s"), thread_db_err_str (err));
+
+      if (!tdb_testinfo->threads_seen)
+	error (_("no threads seen"));
+    }
+  CATCH (except, RETURN_MASK_ERROR)
+    {
+      if (warning_pre_print)
+	fputs_unfiltered (warning_pre_print, gdb_stderr);
+
+      exception_fprintf (gdb_stderr, except,
+			 _("libthread_db integrity checks failed: "));
+
+      test_passed = false;
+    }
+  END_CATCH
+
+  if (test_passed && log_progress)
+    debug_printf (_("libthread_db integrity checks passed.\n"));
+
+  tdb_testinfo = NULL;
+
+  linux_unstop_all_lwps ();
+
+  return test_passed;
+}
+
 /* Attempt to initialize dlopen()ed libthread_db, described by INFO.
    Return 1 on success.
    Failure could happen if libthread_db does not have symbols we expect,
@@ -586,6 +801,13 @@ try_thread_db_load_1 (struct thread_db_info *info)
 #undef TDB_DLSYM
 #undef CHK
 
+  /* Run integrity checks if requested.  */
+  if (check_thread_db_on_load)
+    {
+      if (!check_thread_db (info, libthread_db_debug != 0))
+	return 0;
+    }
+
   if (info->td_ta_thr_iter_p == NULL)
     {
       struct lwp_info *lp;
@@ -1704,6 +1926,24 @@ info_auto_load_libthread_db (const char *args, int from_tty)
     uiout->message (_("No auto-loaded libthread-db.\n"));
 }
 
+/* Implement 'maintenance check libthread-db'.  */
+
+static void
+maintenance_check_libthread_db (const char *args, int from_tty)
+{
+  int inferior_pid = ptid_get_pid (inferior_ptid);
+  struct thread_db_info *info;
+
+  if (inferior_pid == 0)
+    error (_("No inferior running"));
+
+  info = get_thread_db_info (inferior_pid);
+  if (info == NULL)
+    error (_("No libthread_db loaded"));
+
+  check_thread_db (info, true);
+}
+
 static void
 init_thread_db_ops (void)
 {
@@ -1780,6 +2020,23 @@ This options has security implications for untrusted inferiors."),
 Usage: info auto-load libthread-db"),
 	   auto_load_info_cmdlist_get ());
 
+  add_cmd ("libthread-db", class_maintenance,
+	   maintenance_check_libthread_db, _("\
+Run integrity checks on the current inferior's libthread_db."),
+	   &maintenancechecklist);
+
+  add_setshow_boolean_cmd ("check-libthread-db",
+			   class_maintenance,
+			   &check_thread_db_on_load, _("\
+Set whether to check libthread_db at load time."), _("\
+Show whether to check libthread_db at load time."), _("\
+If enabled GDB will run integrity checks on inferior specific libthread_db\n\
+as they are loaded."),
+			   NULL,
+			   NULL,
+			   &maintenance_set_cmdlist,
+			   &maintenance_show_cmdlist);
+
   /* Add ourselves to objfile event chain.  */
   observer_attach_new_objfile (thread_db_new_objfile);
 
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..22be229
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/check-libthread-db.c
@@ -0,0 +1,66 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2017 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 <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..3990cf3
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/check-libthread-db.exp
@@ -0,0 +1,114 @@
+# Copyright 2017 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 Linux.
+if { ![isnative] || [is_remote host] || [target_info exists use_gdb_stub]
+     || ![istarget *-linux*] } {
+    continue
+}
+
+standard_testfile
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
+	 executable debug] != "" } {
+    return -1
+}
+
+# TEST 1: Manual 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" \
+    "libpthread.so not loaded"
+
+
+# TEST 2: Manual 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 (manual)" {
+	"\[\r\n\]+Running libthread_db integrity checks:"
+	"\[\r\n\]+\[ \]+Got thread 0x0 => \[0-9\]+ => 0x0 ... OK"
+	"\[\r\n\]+libthread_db integrity checks passed."
+    }
+
+
+# TEST 3: Manual 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 (manual)" {
+	"\[\r\n\]+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."
+    }
+
+
+# TEST 4: Automated check with NPTL uninitialized.
+
+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 "" \
+    "libpthread.so not initialized (automated)" {
+	"\[\r\n\]+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]"
+    }
+
+
+# TEST 5: Automated check with NPTL fully operational.
+
+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" \
+    "libpthread.so fully initialized (automated)" {
+	"\[\r\n\]+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
-- 
1.8.3.1

Re: [PATCH] linux: Add maintenance commands to test libthread_db

[Simon Marchi]

On 2017-11-22 09:42 AM, Gary Benson wrote:
> 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.
> 
> Built and regtested on RHEL 7.4 x86_64.
> 
> Ok to commit?
> 
> Thanks,
> Gary

Hi Gary,

You have much more experience than I do in this domain, so I'll trust
you if you say it's useful :).  I noted a few comments below, nothing
major.

I would be fine with the patch being committed with those fixed, but
maybe give the others a week or so if they want to add comment (including
Eli for the doc).  If you don't hear anything more after a week, please
go ahead and push.

> 
> --
> 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".
> 
> 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.
> ---
>  gdb/ChangeLog                                    |  11 +
>  gdb/doc/ChangeLog                                |   5 +
>  gdb/doc/gdb.texinfo                              |  13 ++
>  gdb/linux-thread-db.c                            | 257 +++++++++++++++++++++++
>  gdb/testsuite/ChangeLog                          |   5 +
>  gdb/testsuite/gdb.threads/check-libthread-db.c   |  66 ++++++
>  gdb/testsuite/gdb.threads/check-libthread-db.exp | 114 ++++++++++
>  7 files changed, 471 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.c
>  create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.exp
> 
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 29d4789..4d7a7b1 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -34981,6 +34981,11 @@ modify XML target descriptions.
>  Check that the target descriptions dynamically created by @value{GDBN}
>  equal the descriptions created from XML files found in @var{dir}.
>  
> +@kindex maint check libthread-db
> +@item maint check libthread-db
> +Run integrity checks on the current inferior's thread debugging
> +library.
> +
>  @kindex maint print dummy-frames
>  @item maint print dummy-frames
>  Prints the contents of @value{GDBN}'s internal dummy-frame stack.
> @@ -35288,6 +35293,14 @@ number of blocks in the blockvector
>  @end enumerate
>  @end table
>  
> +@kindex maint set check-libthread-db
> +@kindex maint show check-libthread-db
> +@item maint set check-libthread-db [on|off]
> +@itemx maint show check-libthread-db
> +Control whether @value{GDBN} should run integrity checks on inferior
> +specific thread debugging libraries as they are loaded.  The default
> +is not to perform such checks.
> +
>  @kindex maint space
>  @cindex memory used by commands
>  @item maint space @var{value}
> diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
> index ea032fc..d1fdb33 100644
> --- a/gdb/linux-thread-db.c
> +++ b/gdb/linux-thread-db.c
> @@ -46,6 +46,7 @@
>  #include <ctype.h>
>  #include "nat/linux-namespaces.h"
>  #include <algorithm>
> +#include "valprint.h"
>  
>  /* GNU/Linux libthread_db support.
>  
> @@ -80,6 +81,10 @@ static char *libthread_db_search_path;
>     by the "set auto-load libthread-db" command.  */
>  static int auto_load_thread_db = 1;
>  
> +/* Set to non-zero if load-time libthread_db tests have been enabled
> +   by the "maintenence set check-libthread-db" command.  */

"maintenence".

> +static int check_thread_db_on_load = 0;
> +
>  /* "show" command for the auto_load_thread_db configuration variable.  */
>  
>  static void
> @@ -493,6 +498,216 @@ dladdr_to_soname (const void *addr)
>    return NULL;
>  }
>  
> +/* State for check_thread_db_callback.  */
> +
> +struct check_thread_db_info
> +{
> +  /* The libthread_db under test.  */
> +  struct thread_db_info *info;
> +
> +  /* True if progress should be logged.  */
> +  bool log_progress;
> +
> +  /* True if the callback was called.  */
> +  bool threads_seen;
> +};
> +
> +static struct check_thread_db_info *tdb_testinfo;
>
> +
> +/* Callback for check_thread_db.  */
> +
> +static int
> +check_thread_db_callback (const td_thrhandle_t *th, void *arg)
> +{
> +  gdb_assert (tdb_testinfo != NULL);
> +  tdb_testinfo->threads_seen = true;
> +
> +#define LOG(fmt, args...)						\
> +  do									\
> +    {									\
> +      if (tdb_testinfo->log_progress)					\
> +	{								\
> +	  debug_printf (fmt, ## args);					\
> +	  gdb_flush (gdb_stdlog);					\
> +	}								\
> +    }									\
> +  while (0)
> +
> +#define __CHECK(expr, args...)						\
> +  do									\
> +    {									\
> +      if (!(expr))							\
> +	{								\
> +	  LOG (" ... FAIL!\n");						\
> +	  error (args);							\
> +	}								\
> +    }									\
> +  while (0)
> +
> +#define CHECK(expr)							\
> +  __CHECK (expr, "(%s) == false", #expr)
> +
> +#define CHECK_CALL(func, args...)					\
> +  do									\
> +    {									\
> +      td_err_e __err = tdb_testinfo->info->func ## _p (args);		\
> +									\
> +      __CHECK (__err == TD_OK, _("%s failed: %s"), #func,		\
> +	       thread_db_err_str (__err));				\
> +    }									\
> +  while (0)
> +
> +  LOG ("  Got thread");
> +
> +  /* Check td_ta_thr_iter passed consistent arguments.  */
> +  CHECK (th != NULL);
> +  CHECK (arg == (void *) tdb_testinfo);
> +  CHECK (th->th_ta_p == tdb_testinfo->info->thread_agent);
> +
> +  LOG (" %s", core_addr_to_string_nz ((CORE_ADDR) th->th_unique));
> +
> +  /* Check td_thr_get_info.  */
> +  td_thrinfo_t ti;
> +  CHECK_CALL (td_thr_get_info, th, &ti);
> +
> +  LOG (" => %d", ti.ti_lid);
> +
> +  CHECK (ti.ti_ta_p == th->th_ta_p);
> +  CHECK (ti.ti_tid == (thread_t) th->th_unique);
> +
> +  /* Check td_ta_map_lwp2thr.  */
> +  td_thrhandle_t th2;
> +  memset (&th2, 23, sizeof (td_thrhandle_t));
> +  CHECK_CALL (td_ta_map_lwp2thr, th->th_ta_p, ti.ti_lid, &th2);
> +
> +  LOG (" => %s", core_addr_to_string_nz ((CORE_ADDR) th2.th_unique));
> +
> +  CHECK (memcmp (th, &th2, sizeof (td_thrhandle_t)) == 0);
> +
> +  /* Attempt TLS access.  Assuming errno is TLS, this calls
> +     thread_db_get_thread_local_address, which in turn calls
> +     td_thr_tls_get_addr for live inferiors or td_thr_tlsbase
> +     for core files.  This test is skipped if the thread has
> +     not been recorded; proceeding in that case would result
> +     in the test having the side-effect of noticing threads
> +     which seems wrong.
> +
> +     Note that in glibc's libthread_db td_thr_tls_get_addr is
> +     a thin wrapper around td_thr_tlsbase; this check always
> +     hits the bulk of the code.
> +
> +     Note also that we don't actually check any libthread_db
> +     calls are made, we just assume they were; future changes
> +     to how GDB accesses TLS could result in this passing
> +     without exercising the calls it's supposed to.  */
> +  ptid_t ptid = ptid_build (tdb_testinfo->info->pid, ti.ti_lid, 0);
> +  struct thread_info *thread_info = find_thread_ptid (ptid);
> +  if (thread_info != NULL && thread_info->priv != NULL)
> +    {
> +      LOG ("; errno");
> +
> +      scoped_restore_current_thread restore_current_thread;
> +      switch_to_thread (ptid);
> +
> +      expression_up expr = parse_expression ("errno");

Without debug symbols for libc, I get this

(gdb) maintenance check libthread-db
Running libthread_db integrity checks:
  Got thread 0x7ffff7fc0700 => 7975 => 0x7ffff7fc0700; errnowarning: libthread_db integrity checks failed: 'errno' has unknown type; cast it to its declared type

thanks to Pedro's no-debuginfo changes :).  I think it could easily be
worked around with

- expression_up expr = parse_expression ("errno");
+ expression_up expr = parse_expression ("(int) errno");

so that the test works even without libc debug info.  With that change, I
get this, which looks good:

(gdb) maintenance check libthread-db
Running libthread_db integrity checks:
  Got thread 0x7ffff7fc0700 => 8928 => 0x7ffff7fc0700; errno = 0 ... OK
libthread_db integrity checks passed.



> +      struct value *val = evaluate_expression (expr.get ());
> +
> +      if (tdb_testinfo->log_progress)
> +	{
> +	  struct value_print_options opts;
> +
> +	  get_user_print_options (&opts);
> +	  LOG (" = ");
> +	  value_print (val, gdb_stdlog, &opts);
> +	}
> +    }
> +
> +  LOG (" ... OK\n");
> +
> +#undef LOG
> +#undef __CHECK
> +#undef CHECK
> +#undef CHECK_CALL
> +
> +  return 0;
> +}
> +
> +/* Run integrity checks on the dlopen()ed libthread_db described by
> +   INFO.  Returns true on success, displays a warning and returns
> +   false on failure.  Logs progress messages to gdb_stdlog during
> +   the test if LOG_PROGRESS is true.  */
> +
> +static bool
> +check_thread_db (struct thread_db_info *info, bool log_progress)
> +{
> +  bool test_passed = true;
> +
> +  if (log_progress)
> +    debug_printf (_("Running libthread_db integrity checks:\n"));
> +
> +  /* GDB avoids using td_ta_thr_iter wherever possible (see comment
> +     in try_thread_db_load_1 below) so in order to test it we may
> +     have to locate it ourselves.  */
> +  td_ta_thr_iter_ftype *td_ta_thr_iter_p = info->td_ta_thr_iter_p;
> +  if (td_ta_thr_iter_p == NULL)
> +    {
> +      void *thr_iter = verbose_dlsym (info->handle, "td_ta_thr_iter");
> +      if (thr_iter == NULL)
> +	return 0;
> +
> +      td_ta_thr_iter_p = (td_ta_thr_iter_ftype *) thr_iter;
> +    }
> +
> +  /* Set up the test state we share with the callback.  */
> +  gdb_assert (tdb_testinfo == NULL);
> +  struct check_thread_db_info tdb_testinfo_buf;
> +  tdb_testinfo = &tdb_testinfo_buf;
> +
> +  memset (tdb_testinfo, 0, sizeof (struct check_thread_db_info));
> +  tdb_testinfo->info = info;
> +  tdb_testinfo->log_progress = log_progress;

Just a nit, but check_thread_db_info could use a constructor that receives
these as parameters.

> +
> +  /* td_ta_thr_iter shouldn't be used on running processes.  */
> +  linux_stop_and_wait_all_lwps ();
> +
> +  TRY
> +    {
> +      td_err_e err = td_ta_thr_iter_p (info->thread_agent,
> +				       check_thread_db_callback,
> +				       tdb_testinfo,
> +				       TD_THR_ANY_STATE,
> +				       TD_THR_LOWEST_PRIORITY,
> +				       TD_SIGNO_MASK,
> +				       TD_THR_ANY_USER_FLAGS);
> +
> +      if (err != TD_OK)
> +	error (_("td_ta_thr_iter failed: %s"), thread_db_err_str (err));
> +
> +      if (!tdb_testinfo->threads_seen)
> +	error (_("no threads seen"));
> +    }
> +  CATCH (except, RETURN_MASK_ERROR)
> +    {
> +      if (warning_pre_print)
> +	fputs_unfiltered (warning_pre_print, gdb_stderr);
> +
> +      exception_fprintf (gdb_stderr, except,
> +			 _("libthread_db integrity checks failed: "));
> +
> +      test_passed = false;
> +    }
> +  END_CATCH
> +
> +  if (test_passed && log_progress)
> +    debug_printf (_("libthread_db integrity checks passed.\n"));
> +
> +  tdb_testinfo = NULL;
> +
> +  linux_unstop_all_lwps ();
> +
> +  return test_passed;
> +}
> +
>  /* Attempt to initialize dlopen()ed libthread_db, described by INFO.
>     Return 1 on success.
>     Failure could happen if libthread_db does not have symbols we expect,
> @@ -586,6 +801,13 @@ try_thread_db_load_1 (struct thread_db_info *info)
>  #undef TDB_DLSYM
>  #undef CHK
>  
> +  /* Run integrity checks if requested.  */
> +  if (check_thread_db_on_load)
> +    {
> +      if (!check_thread_db (info, libthread_db_debug != 0))

You can use simply "libthread_db_debug" instead of "libthread_db_debug != 0",
since it's semantically a bool.

> +	return 0;
> +    }
> +
>    if (info->td_ta_thr_iter_p == NULL)
>      {
>        struct lwp_info *lp;
> @@ -1704,6 +1926,24 @@ info_auto_load_libthread_db (const char *args, int from_tty)
>      uiout->message (_("No auto-loaded libthread-db.\n"));
>  }
>  
> +/* Implement 'maintenance check libthread-db'.  */
> +
> +static void
> +maintenance_check_libthread_db (const char *args, int from_tty)
> +{
> +  int inferior_pid = ptid_get_pid (inferior_ptid);
> +  struct thread_db_info *info;
> +
> +  if (inferior_pid == 0)
> +    error (_("No inferior running"));
> +
> +  info = get_thread_db_info (inferior_pid);
> +  if (info == NULL)
> +    error (_("No libthread_db loaded"));
> +
> +  check_thread_db (info, true);
> +}
> +
>  static void
>  init_thread_db_ops (void)
>  {
> @@ -1780,6 +2020,23 @@ This options has security implications for untrusted inferiors."),
>  Usage: info auto-load libthread-db"),
>  	   auto_load_info_cmdlist_get ());
>  
> +  add_cmd ("libthread-db", class_maintenance,
> +	   maintenance_check_libthread_db, _("\
> +Run integrity checks on the current inferior's libthread_db."),
> +	   &maintenancechecklist);
> +
> +  add_setshow_boolean_cmd ("check-libthread-db",
> +			   class_maintenance,
> +			   &check_thread_db_on_load, _("\
> +Set whether to check libthread_db at load time."), _("\
> +Show whether to check libthread_db at load time."), _("\
> +If enabled GDB will run integrity checks on inferior specific libthread_db\n\
> +as they are loaded."),
> +			   NULL,
> +			   NULL,
> +			   &maintenance_set_cmdlist,
> +			   &maintenance_show_cmdlist);
> +
>    /* Add ourselves to objfile event chain.  */
>    observer_attach_new_objfile (thread_db_new_objfile);
>  
> 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..22be229
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/check-libthread-db.c
> @@ -0,0 +1,66 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2017 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 <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..3990cf3
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/check-libthread-db.exp
> @@ -0,0 +1,114 @@
> +# Copyright 2017 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 Linux.
> +if { ![isnative] || [is_remote host] || [target_info exists use_gdb_stub]
> +     || ![istarget *-linux*] } {
> +    continue
> +}
> +
> +standard_testfile
> +
> +if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
> +	 executable debug] != "" } {
> +    return -1
> +}
> +
> +# TEST 1: Manual 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" \
> +    "libpthread.so not loaded"
> +
> +
> +# TEST 2: Manual 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 (manual)" {

Don't use test names that end with something in parentheses, see:

https://sourceware.org/gdb/wiki/GDBTestcaseCookbook#Do_not_use_.22tail_parentheses.22_on_test_messages

To keep names unique, you can either just change the format of the message,
or wrap the code with

with_test_prefix "manual" {
  ...
}

with_test_prefix "automated" {
  ...
}

> +	"\[\r\n\]+Running libthread_db integrity checks:"
> +	"\[\r\n\]+\[ \]+Got thread 0x0 => \[0-9\]+ => 0x0 ... OK"
> +	"\[\r\n\]+libthread_db integrity checks passed."
> +    }
> +
> +
> +# TEST 3: Manual 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 (manual)" {
> +	"\[\r\n\]+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."
> +    }
> +
> +
> +# TEST 4: Automated check with NPTL uninitialized.
> +
> +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 "" \
> +    "libpthread.so not initialized (automated)" {
> +	"\[\r\n\]+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]"
> +    }
> +
> +
> +# TEST 5: Automated check with NPTL fully operational.
> +
> +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" \
> +    "libpthread.so fully initialized (automated)" {
> +	"\[\r\n\]+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
> 

Thanks,

Simon

Re: [PATCH] linux: Add maintenance commands to test libthread_db

[Pedro Alves]

On 11/22/2017 02:42 PM, Gary Benson wrote:

> 
> Built and regtested on RHEL 7.4 x86_64.
> 
> Ok to commit?

I noticed you're missing a NEWS entry.

Some more comments below.

> +static int
> +check_thread_db_callback (const td_thrhandle_t *th, void *arg)
> +{
> +  gdb_assert (tdb_testinfo != NULL);
> +  tdb_testinfo->threads_seen = true;
> +
> +#define LOG(fmt, args...)						\
> +  do									\
> +    {									\
> +      if (tdb_testinfo->log_progress)					\
> +	{								\
> +	  debug_printf (fmt, ## args);					\
> +	  gdb_flush (gdb_stdlog);					\
> +	}								\
> +    }									\
> +  while (0)
> +
> +#define __CHECK(expr, args...)						\

Symbols that start with __ are reserved for the C/C++ implementation.

(E.g., glibc would be in the right to define it in some header
for its own purposes).

You can rename it to CHECK_1 or something like that.

> +  do									\
> +    {									\
> +      if (!(expr))							\
> +	{								\
> +	  LOG (" ... FAIL!\n");						\
> +	  error (args);							\
> +	}								\
> +    }									\
> +  while (0)
> +
> +#define CHECK(expr)							\
> +  __CHECK (expr, "(%s) == false", #expr)
> +
> +#define CHECK_CALL(func, args...)					\
> +  do									\
> +    {									\
> +      td_err_e __err = tdb_testinfo->info->func ## _p (args);		\
> +									\
> +      __CHECK (__err == TD_OK, _("%s failed: %s"), #func,		\
> +	       thread_db_err_str (__err));				\

Likewise __err.

> +# 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 Linux.

GNU/Linux, because glibc.

> +if { ![isnative] || [is_remote host] || [target_info exists use_gdb_stub]
> +     || ![istarget *-linux*] } {
> +    continue

I think this fails to filter out --target_board=native-extended-gdbserver ?

This would be more to the point, and would work, I think (haven't tested):

# 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
> +}
> +
> +# TEST 1: Manual check with libthread_db not loaded.

Please remove the numbering in "TEST 1", etc.  We have a few old
testcases that have comments like that, and over the years as tests
are added/removed to the file, the numbering gets annoyingly in the
way / odd, when inevitably in the future we want to insert a
test in the middle, remove or reorder tests, etc.

> +
> +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" \
> +    "libpthread.so not loaded"
> +
> +
> +# TEST 2: Manual 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 (manual)" {
> +	"\[\r\n\]+Running libthread_db integrity checks:"
> +	"\[\r\n\]+\[ \]+Got thread 0x0 => \[0-9\]+ => 0x0 ... OK"
> +	"\[\r\n\]+libthread_db integrity checks passed."
> +    }
> +
> +
> +# TEST 3: Manual 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 (manual)" {
> +	"\[\r\n\]+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."
> +    }
> +
> +
> +# TEST 4: Automated check with NPTL uninitialized.
> +
> +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 "" \
> +    "libpthread.so not initialized (automated)" {
> +	"\[\r\n\]+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]"
> +    }
> +
> +
> +# TEST 5: Automated check with NPTL fully operational.
> +
> +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" \
> +    "libpthread.so fully initialized (automated)" {
> +	"\[\r\n\]+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
> 

I'm surprised to not see any validation when debugging
a core dump.  Would it work?

Thanks,
Pedro Alves

[PATCH v2] linux: Add maintenance commands to test libthread_db

[Gary Benson]

Hi all,

This is an updated version of a patch I submitted for review back in
November.  It 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 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 changes since version 1:
 - The check no longer requires debuginfo for glibc.  [Simon]
 - Parts of the check are skipped when working with core files.
   (I hadn't checked this until Pedro asked about them).
   Previously the check would fail because one of the tested
   operations does not work with core files on some platforms.
 - Macros starting with double underscores have been renamed.  [Pedro]
   (The macros have been somewhat reorganized too, to implement
   the core files change I mentioned above).
 - libthread_db_debug now is treated as a boolean in the place
   where previously it wasn't.  [Simon]
 - There is a NEWS entry. [Pedro]

Testcase changes since version 1:
 - Test names no longer contain parentheses.  [Simon]
 - The criteria for skipping the test have been replaced with
   Pedro's suggestion.  [Pedro]
 - Numbers in testcase comments have been removed.  [Pedro]

Built and regtested on RHEL 7.5 x86_64.

Ok to commit?

Thanks,
Gary

--
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.
---
 gdb/ChangeLog                                    |  12 +
 gdb/NEWS                                         |  10 +
 gdb/doc/ChangeLog                                |   5 +
 gdb/doc/gdb.texinfo                              |  13 +
 gdb/linux-thread-db.c                            | 291 +++++++++++++++++++++++
 gdb/testsuite/ChangeLog                          |   5 +
 gdb/testsuite/gdb.threads/check-libthread-db.c   |  67 ++++++
 gdb/testsuite/gdb.threads/check-libthread-db.exp | 113 +++++++++
 8 files changed, 516 insertions(+)
 create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.c
 create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.exp

diff --git a/gdb/NEWS b/gdb/NEWS
index cef5580..2e6cb74 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -27,6 +27,16 @@ set|show record btrace cpu
   Controls the processor to be used for enabling errata workarounds for
   branch trace decode.
 
+maint check libthread-db
+  Run integrity checks on the current inferior's thread debugging
+  library
+
+maint set check-libthread-db (on|off)
+maint show check-libthread-db
+  Control whether to run integrity checks on inferior specific thread
+  debugging libraries as they are loaded.  The default is not to
+  perform such checks.
+
 * Python API
 
   ** Type alignment is now exposed via the "align" attribute of a gdb.Type.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 28f083f..6faaabe 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35533,6 +35533,11 @@ modify XML target descriptions.
 Check that the target descriptions dynamically created by @value{GDBN}
 equal the descriptions created from XML files found in @var{dir}.
 
+@kindex maint check libthread-db
+@item maint check libthread-db
+Run integrity checks on the current inferior's thread debugging
+library.
+
 @kindex maint print dummy-frames
 @item maint print dummy-frames
 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
@@ -35840,6 +35845,14 @@ number of blocks in the blockvector
 @end enumerate
 @end table
 
+@kindex maint set check-libthread-db
+@kindex maint show check-libthread-db
+@item maint set check-libthread-db [on|off]
+@itemx maint show check-libthread-db
+Control whether @value{GDBN} should run integrity checks on inferior
+specific thread debugging libraries as they are loaded.  The default
+is not to perform such checks.
+
 @kindex maint space
 @cindex memory used by commands
 @item maint space @var{value}
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index 8feab6f..ea4967b 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -47,6 +47,7 @@
 #include "nat/linux-namespaces.h"
 #include <algorithm>
 #include "common/pathstuff.h"
+#include "valprint.h"
 
 /* GNU/Linux libthread_db support.
 
@@ -117,6 +118,10 @@ static char *libthread_db_search_path;
    by the "set auto-load libthread-db" command.  */
 static int auto_load_thread_db = 1;
 
+/* Set to non-zero if load-time libthread_db tests have been enabled
+   by the "maintenence set check-libthread-db" command.  */
+static int check_thread_db_on_load = 0;
+
 /* "show" command for the auto_load_thread_db configuration variable.  */
 
 static void
@@ -534,6 +539,250 @@ dladdr_to_soname (const void *addr)
   return NULL;
 }
 
+/* State for check_thread_db_callback.  */
+
+struct check_thread_db_info
+{
+  /* The libthread_db under test.  */
+  struct thread_db_info *info;
+
+  /* True if progress should be logged.  */
+  bool log_progress;
+
+  /* True if the callback was called.  */
+  bool threads_seen;
+
+  /* Name of last libthread_db function called.  */
+  const char *last_call;
+
+  /* Value returned by last libthread_db call.  */
+  td_err_e last_result;
+};
+
+static struct check_thread_db_info *tdb_testinfo;
+
+/* Callback for check_thread_db.  */
+
+static int
+check_thread_db_callback (const td_thrhandle_t *th, void *arg)
+{
+  gdb_assert (tdb_testinfo != NULL);
+  tdb_testinfo->threads_seen = true;
+
+#define LOG(fmt, args...)						\
+  do									\
+    {									\
+      if (tdb_testinfo->log_progress)					\
+	{								\
+	  debug_printf (fmt, ## args);					\
+	  gdb_flush (gdb_stdlog);					\
+	}								\
+    }									\
+  while (0)
+
+#define CHECK_1(expr, args...)						\
+  do									\
+    {									\
+      if (!(expr))							\
+	{								\
+	  LOG (" ... FAIL!\n");						\
+	  error (args);							\
+	}								\
+    }									\
+  while (0)
+
+#define CHECK(expr)							\
+  CHECK_1 (expr, "(%s) == false", #expr)
+
+#define CALL_UNCHECKED(func, args...)					\
+  do									\
+    {									\
+      tdb_testinfo->last_call = #func;					\
+      tdb_testinfo->last_result						\
+	= tdb_testinfo->info->func ## _p (args);			\
+    }									\
+  while (0)
+
+#define CHECK_CALL()							\
+  CHECK_1 (tdb_testinfo->last_result == TD_OK,				\
+	   _("%s failed: %s"),						\
+	   tdb_testinfo->last_call,					\
+	   thread_db_err_str (tdb_testinfo->last_result))		\
+
+#define CALL(func, args...)						\
+  do									\
+    {									\
+      CALL_UNCHECKED (func, args);					\
+      CHECK_CALL ();							\
+    }									\
+  while (0)
+
+  LOG ("  Got thread");
+
+  /* Check td_ta_thr_iter passed consistent arguments.  */
+  CHECK (th != NULL);
+  CHECK (arg == (void *) tdb_testinfo);
+  CHECK (th->th_ta_p == tdb_testinfo->info->thread_agent);
+
+  LOG (" %s", core_addr_to_string_nz ((CORE_ADDR) th->th_unique));
+
+  /* Check td_thr_get_info.  */
+  td_thrinfo_t ti;
+  CALL (td_thr_get_info, th, &ti);
+
+  LOG (" => %d", ti.ti_lid);
+
+  CHECK (ti.ti_ta_p == th->th_ta_p);
+  CHECK (ti.ti_tid == (thread_t) th->th_unique);
+
+  /* Check td_ta_map_lwp2thr.  */
+  td_thrhandle_t th2;
+  memset (&th2, 23, sizeof (td_thrhandle_t));
+  CALL_UNCHECKED (td_ta_map_lwp2thr, th->th_ta_p, ti.ti_lid, &th2);
+
+  if (tdb_testinfo->last_result == TD_ERR && !target_has_execution)
+    {
+      /* Some platforms require execution for td_ta_map_lwp2thr.  */
+      LOG (_("; can't map_lwp2thr"));
+    }
+  else
+    {
+      CHECK_CALL ();
+
+      LOG (" => %s", core_addr_to_string_nz ((CORE_ADDR) th2.th_unique));
+
+      CHECK (memcmp (th, &th2, sizeof (td_thrhandle_t)) == 0);
+    }
+
+  /* Attempt TLS access.  Assuming errno is TLS, this calls
+     thread_db_get_thread_local_address, which in turn calls
+     td_thr_tls_get_addr for live inferiors or td_thr_tlsbase
+     for core files.  This test is skipped if the thread has
+     not been recorded; proceeding in that case would result
+     in the test having the side-effect of noticing threads
+     which seems wrong.
+
+     Note that in glibc's libthread_db td_thr_tls_get_addr is
+     a thin wrapper around td_thr_tlsbase; this check always
+     hits the bulk of the code.
+
+     Note also that we don't actually check any libthread_db
+     calls are made, we just assume they were; future changes
+     to how GDB accesses TLS could result in this passing
+     without exercising the calls it's supposed to.  */
+  ptid_t ptid = ptid_build (tdb_testinfo->info->pid, ti.ti_lid, 0);
+  struct thread_info *thread_info = find_thread_ptid (ptid);
+  if (thread_info != NULL && thread_info->priv != NULL)
+    {
+      LOG ("; errno");
+
+      scoped_restore_current_thread restore_current_thread;
+      switch_to_thread (ptid);
+
+      expression_up expr = parse_expression ("(int) errno");
+      struct value *val = evaluate_expression (expr.get ());
+
+      if (tdb_testinfo->log_progress)
+	{
+	  struct value_print_options opts;
+
+	  get_user_print_options (&opts);
+	  LOG (" = ");
+	  value_print (val, gdb_stdlog, &opts);
+	}
+    }
+
+  LOG (" ... OK\n");
+
+#undef LOG
+#undef CHECK_1
+#undef CHECK
+#undef CALL_UNCHECKED
+#undef CHECK_CALL
+#undef CALL
+
+  return 0;
+}
+
+/* Run integrity checks on the dlopen()ed libthread_db described by
+   INFO.  Returns true on success, displays a warning and returns
+   false on failure.  Logs progress messages to gdb_stdlog during
+   the test if LOG_PROGRESS is true.  */
+
+static bool
+check_thread_db (struct thread_db_info *info, bool log_progress)
+{
+  bool test_passed = true;
+
+  if (log_progress)
+    debug_printf (_("Running libthread_db integrity checks:\n"));
+
+  /* GDB avoids using td_ta_thr_iter wherever possible (see comment
+     in try_thread_db_load_1 below) so in order to test it we may
+     have to locate it ourselves.  */
+  td_ta_thr_iter_ftype *td_ta_thr_iter_p = info->td_ta_thr_iter_p;
+  if (td_ta_thr_iter_p == NULL)
+    {
+      void *thr_iter = verbose_dlsym (info->handle, "td_ta_thr_iter");
+      if (thr_iter == NULL)
+	return 0;
+
+      td_ta_thr_iter_p = (td_ta_thr_iter_ftype *) thr_iter;
+    }
+
+  /* Set up the test state we share with the callback.  */
+  gdb_assert (tdb_testinfo == NULL);
+  struct check_thread_db_info tdb_testinfo_buf;
+  tdb_testinfo = &tdb_testinfo_buf;
+
+  memset (tdb_testinfo, 0, sizeof (struct check_thread_db_info));
+  tdb_testinfo->info = info;
+  tdb_testinfo->log_progress = log_progress;
+
+  /* td_ta_thr_iter shouldn't be used on running processes.  Note that
+     it's possible the inferior will stop midway through modifying one
+     of its thread lists, in which case the check will spuriously
+     fail.  */
+  linux_stop_and_wait_all_lwps ();
+
+  TRY
+    {
+      td_err_e err = td_ta_thr_iter_p (info->thread_agent,
+				       check_thread_db_callback,
+				       tdb_testinfo,
+				       TD_THR_ANY_STATE,
+				       TD_THR_LOWEST_PRIORITY,
+				       TD_SIGNO_MASK,
+				       TD_THR_ANY_USER_FLAGS);
+
+      if (err != TD_OK)
+	error (_("td_ta_thr_iter failed: %s"), thread_db_err_str (err));
+
+      if (!tdb_testinfo->threads_seen)
+	error (_("no threads seen"));
+    }
+  CATCH (except, RETURN_MASK_ERROR)
+    {
+      if (warning_pre_print)
+	fputs_unfiltered (warning_pre_print, gdb_stderr);
+
+      exception_fprintf (gdb_stderr, except,
+			 _("libthread_db integrity checks failed: "));
+
+      test_passed = false;
+    }
+  END_CATCH
+
+  if (test_passed && log_progress)
+    debug_printf (_("libthread_db integrity checks passed.\n"));
+
+  tdb_testinfo = NULL;
+
+  linux_unstop_all_lwps ();
+
+  return test_passed;
+}
+
 /* Attempt to initialize dlopen()ed libthread_db, described by INFO.
    Return 1 on success.
    Failure could happen if libthread_db does not have symbols we expect,
@@ -627,6 +876,13 @@ try_thread_db_load_1 (struct thread_db_info *info)
 #undef TDB_DLSYM
 #undef CHK
 
+  /* Run integrity checks if requested.  */
+  if (check_thread_db_on_load)
+    {
+      if (!check_thread_db (info, libthread_db_debug))
+	return 0;
+    }
+
   if (info->td_ta_thr_iter_p == NULL)
     {
       struct lwp_info *lp;
@@ -1668,6 +1924,24 @@ info_auto_load_libthread_db (const char *args, int from_tty)
     uiout->message (_("No auto-loaded libthread-db.\n"));
 }
 
+/* Implement 'maintenance check libthread-db'.  */
+
+static void
+maintenance_check_libthread_db (const char *args, int from_tty)
+{
+  int inferior_pid = ptid_get_pid (inferior_ptid);
+  struct thread_db_info *info;
+
+  if (inferior_pid == 0)
+    error (_("No inferior running"));
+
+  info = get_thread_db_info (inferior_pid);
+  if (info == NULL)
+    error (_("No libthread_db loaded"));
+
+  check_thread_db (info, true);
+}
+
 void
 _initialize_thread_db (void)
 {
@@ -1718,6 +1992,23 @@ This options has security implications for untrusted inferiors."),
 Usage: info auto-load libthread-db"),
 	   auto_load_info_cmdlist_get ());
 
+  add_cmd ("libthread-db", class_maintenance,
+	   maintenance_check_libthread_db, _("\
+Run integrity checks on the current inferior's libthread_db."),
+	   &maintenancechecklist);
+
+  add_setshow_boolean_cmd ("check-libthread-db",
+			   class_maintenance,
+			   &check_thread_db_on_load, _("\
+Set whether to check libthread_db at load time."), _("\
+Show whether to check libthread_db at load time."), _("\
+If enabled GDB will run integrity checks on inferior specific libthread_db\n\
+as they are loaded."),
+			   NULL,
+			   NULL,
+			   &maintenance_set_cmdlist,
+			   &maintenance_show_cmdlist);
+
   /* Add ourselves to objfile event chain.  */
   gdb::observers::new_objfile.attach (thread_db_new_objfile);
 
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..02d76aa
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/check-libthread-db.exp
@@ -0,0 +1,113 @@
+# 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
+}
+
+# Manual 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" \
+    "user-initiated check with no libpthread.so loaded"
+
+
+# Manual 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" \
+    "user-initiated check with 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."
+    }
+
+
+# Manual 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" \
+    "user-initiated check with 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."
+    }
+
+
+# Automated check with NPTL uninitialized.
+
+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 "" \
+    "automated load-time check with 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."
+	"\[\r\n\]+[Thread debugging using libthread_db enabled]"
+    }
+
+
+# Automated check with NPTL fully operational.
+
+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" \
+    "automated load-time check with 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\[1-9a-f\]\[0-9a-f\]+ ... 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
-- 
1.8.3.1

Re: [PATCH v2] linux: Add maintenance commands to test libthread_db

[Eli Zaretskii]

> From: Gary Benson <gbenson@redhat.com>
> Cc: Simon Marchi <simon.marchi@ericsson.com>,	Pedro Alves <palves@redhat.com>
> Date: Wed, 23 May 2018 18:32:56 +0100
> 
> 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 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.

I think some of this text should be in the manual, otherwise the
description of the command is not very useful.

> diff --git a/gdb/NEWS b/gdb/NEWS
> index cef5580..2e6cb74 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -27,6 +27,16 @@ set|show record btrace cpu
>    Controls the processor to be used for enabling errata workarounds for
>    branch trace decode.
>  
> +maint check libthread-db
> +  Run integrity checks on the current inferior's thread debugging
> +  library
> +
> +maint set check-libthread-db (on|off)
> +maint show check-libthread-db
> +  Control whether to run integrity checks on inferior specific thread
> +  debugging libraries as they are loaded.  The default is not to
> +  perform such checks.
> +
>  * Python API

This part is OK.

> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 28f083f..6faaabe 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -35533,6 +35533,11 @@ modify XML target descriptions.
>  Check that the target descriptions dynamically created by @value{GDBN}
>  equal the descriptions created from XML files found in @var{dir}.
>  
> +@kindex maint check libthread-db
> +@item maint check libthread-db
> +Run integrity checks on the current inferior's thread debugging
> +library.
> +
>  @kindex maint print dummy-frames
>  @item maint print dummy-frames
>  Prints the contents of @value{GDBN}'s internal dummy-frame stack.
> @@ -35840,6 +35845,14 @@ number of blocks in the blockvector
>  @end enumerate
>  @end table
>  
> +@kindex maint set check-libthread-db
> +@kindex maint show check-libthread-db
> +@item maint set check-libthread-db [on|off]
> +@itemx maint show check-libthread-db
> +Control whether @value{GDBN} should run integrity checks on inferior
> +specific thread debugging libraries as they are loaded.  The default
> +is not to perform such checks.
> +

This is also OK, modulo the request to expand the description.

Thanks.

Re: [PATCH v2] linux: Add maintenance commands to test libthread_db

[Simon Marchi]

On 2018-05-23 13:32, Gary Benson wrote:
> Hi all,
> 
> This is an updated version of a patch I submitted for review back in
> November.  It 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 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 changes since version 1:
>  - The check no longer requires debuginfo for glibc.  [Simon]
>  - Parts of the check are skipped when working with core files.
>    (I hadn't checked this until Pedro asked about them).
>    Previously the check would fail because one of the tested
>    operations does not work with core files on some platforms.
>  - Macros starting with double underscores have been renamed.  [Pedro]
>    (The macros have been somewhat reorganized too, to implement
>    the core files change I mentioned above).
>  - libthread_db_debug now is treated as a boolean in the place
>    where previously it wasn't.  [Simon]
>  - There is a NEWS entry. [Pedro]
> 
> Testcase changes since version 1:
>  - Test names no longer contain parentheses.  [Simon]
>  - The criteria for skipping the test have been replaced with
>    Pedro's suggestion.  [Pedro]
>  - Numbers in testcase comments have been removed.  [Pedro]
> 
> Built and regtested on RHEL 7.5 x86_64.
> 
> Ok to commit?
> 
> Thanks,
> Gary

The patch looks good from my side.

Simon

Re: [PATCH v2] linux: Add maintenance commands to test libthread_db

[Gary Benson]

Eli Zaretskii wrote:
> > From: Gary Benson <gbenson@redhat.com>
> > 
> > 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 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.
> 
> I think some of this text should be in the manual, otherwise the
> description of the command is not very useful.

How about this, as the full diff of the manual?  I added the text to
the first section, and updated the second to point at the first and
also to document what happens when automated tests fail.

-- 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 28f083f..faca132 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35533,6 +35533,14 @@ modify XML target descriptions.
 Check that the target descriptions dynamically created by @value{GDBN}
 equal the descriptions created from XML files found in @var{dir}.
 
+@kindex maint check libthread-db
+@item maint check libthread-db
+Run integrity checks on the current inferior's thread debugging
+library.  This exercises all libthread_db functionality used by GDB on
+GNU/Linux systems, and by extension also exercises the proc_service
+functions provided by GDB that libthread_db uses.  Note that parts of
+the test may be skipped on some platforms when debugging core files.
+
 @kindex maint print dummy-frames
 @item maint print dummy-frames
 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
@@ -35840,6 +35848,17 @@ number of blocks in the blockvector
 @end enumerate
 @end table
 
+@kindex maint set check-libthread-db
+@kindex maint show check-libthread-db
+@item maint set check-libthread-db [on|off]
+@itemx maint show check-libthread-db
+Control whether @value{GDBN} should run integrity checks on inferior
+specific thread debugging libraries as they are loaded.  The default
+is not to perform such checks.  If any check fails @value{GDBN} will
+unload the library and continue searching for a suitable candidate as
+described in @ref{set libthread-db-search-path}.  For more information
+about the tests, see @ref{maint check libthread-db}.
+
 @kindex maint space
 @cindex memory used by commands
 @item maint space @var{value}

Re: [PATCH v2] linux: Add maintenance commands to test libthread_db

[Eli Zaretskii]

> Date: Tue, 5 Jun 2018 16:46:13 +0100
> From: Gary Benson <gbenson@redhat.com>
> Cc: gdb-patches@sourceware.org, simon.marchi@ericsson.com,
> 	palves@redhat.com
> 
> > I think some of this text should be in the manual, otherwise the
> > description of the command is not very useful.
> 
> How about this, as the full diff of the manual?  I added the text to
> the first section, and updated the second to point at the first and
> also to document what happens when automated tests fail.

Thanks, this is very good.  I have a couple of minor comments:

> +@kindex maint check libthread-db
> +@item maint check libthread-db
> +Run integrity checks on the current inferior's thread debugging
> +library.  This exercises all libthread_db functionality used by GDB on

"libthread_db" should be in @code or in @file.  And please use
@value{GDBN} instead of a literal "GDB".

> +GNU/Linux systems, and by extension also exercises the proc_service

proc_service should be in @code.

Re: [PATCH v2] linux: Add maintenance commands to test libthread_db

[Pedro Alves]

Hi Gary,

On 05/23/2018 06:32 PM, Gary Benson wrote:

> Ok to commit?

This looks good to me too, except one thing.  I think
you end up with duplicated test messages:

  https://sourceware.org/gdb/wiki/GDBTestcaseCookbook#Make_sure_test_messages_are_unique

I suggestwrapping the several phases of the testcase in with_test_prefix
or proc_with_prefix.  Something like:

# Manual check with NPTL fully operational.

with_test_prefix "manual fully op" {
   ...
}

# Automated check with NPTL uninitialized.

with_test_prefix "automated uninitialized" {
   ...
}

etc.

OK with me with that change.

Thanks,
Pedro Alves

[PATCH v3/pushed] linux: Add maintenance commands to test libthread_db

[Gary Benson]

Eli Zaretskii wrote:
> Gary Benson wrote:
> > +library.  This exercises all libthread_db functionality used by GDB on
> 
> "libthread_db" should be in @code or in @file.  And please use
> @value{GDBN} instead of a literal "GDB".

Done.  FWIW I used @code for "libthread_db", it's what's used in
@ref{set libthread-db-search-path}.

> > +GNU/Linux systems, and by extension also exercises the proc_service
> 
> proc_service should be in @code.

Done.

Pedro Alves wrote:
> This looks good to me too, except one thing.  I think you end up
> with duplicated test messages:
[snip]
> I suggest wrapping the several phases of the testcase in
> with_test_prefix or proc_with_prefix.  Something like:
[snip]

Done.  I'd changed the obvious messages for v2 of the patch, Simon
mentioned something about with_test_prefix but at the time it didn't
seem worth wrapping things just for one or two messages so I did it
manually.  I hadn't realized there were messages emitted by the setup
commands that were also coming out duplicated (because the setup
commands were the same).  So I've used with_test_prefix this time,
and used the recipe you linked to check the output.

> OK with me with that change.

Cool, I pushed the updated patch (included below).

Have a good weekend everyone!

Cheers,
Gary

---
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.
---
 gdb/ChangeLog                                    |  12 +
 gdb/NEWS                                         |  10 +
 gdb/doc/ChangeLog                                |   5 +
 gdb/doc/gdb.texinfo                              |  20 ++
 gdb/linux-thread-db.c                            | 291 +++++++++++++++++++++++
 gdb/testsuite/ChangeLog                          |   5 +
 gdb/testsuite/gdb.threads/check-libthread-db.c   |  67 ++++++
 gdb/testsuite/gdb.threads/check-libthread-db.exp | 114 +++++++++
 8 files changed, 524 insertions(+)
 create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.c
 create mode 100644 gdb/testsuite/gdb.threads/check-libthread-db.exp

diff --git a/gdb/NEWS b/gdb/NEWS
index 8fb6a2a..13da2f1 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -36,6 +36,16 @@ set|show record btrace cpu
   Controls the processor to be used for enabling errata workarounds for
   branch trace decode.
 
+maint check libthread-db
+  Run integrity checks on the current inferior's thread debugging
+  library
+
+maint set check-libthread-db (on|off)
+maint show check-libthread-db
+  Control whether to run integrity checks on inferior specific thread
+  debugging libraries as they are loaded.  The default is not to
+  perform such checks.
+
 * Python API
 
   ** Type alignment is now exposed via the "align" attribute of a gdb.Type.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 4968b37..2c0ac33 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35547,6 +35547,15 @@ modify XML target descriptions.
 Check that the target descriptions dynamically created by @value{GDBN}
 equal the descriptions created from XML files found in @var{dir}.
 
+@kindex maint check libthread-db
+@item maint check libthread-db
+Run integrity checks on the current inferior's thread debugging
+library.  This exercises all @code{libthread_db} functionality used by
+@value{GDBN} on GNU/Linux systems, and by extension also exercises the
+@code{proc_service} functions provided by @value{GDBN} that
+@code{libthread_db} uses.  Note that parts of the test may be skipped
+on some platforms when debugging core files.
+
 @kindex maint print dummy-frames
 @item maint print dummy-frames
 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
@@ -35854,6 +35863,17 @@ number of blocks in the blockvector
 @end enumerate
 @end table
 
+@kindex maint set check-libthread-db
+@kindex maint show check-libthread-db
+@item maint set check-libthread-db [on|off]
+@itemx maint show check-libthread-db
+Control whether @value{GDBN} should run integrity checks on inferior
+specific thread debugging libraries as they are loaded.  The default
+is not to perform such checks.  If any check fails @value{GDBN} will
+unload the library and continue searching for a suitable candidate as
+described in @ref{set libthread-db-search-path}.  For more information
+about the tests, see @ref{maint check libthread-db}.
+
 @kindex maint space
 @cindex memory used by commands
 @item maint space @var{value}
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index ccfd9e4..192e087 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -47,6 +47,7 @@
 #include "nat/linux-namespaces.h"
 #include <algorithm>
 #include "common/pathstuff.h"
+#include "valprint.h"
 
 /* GNU/Linux libthread_db support.
 
@@ -117,6 +118,10 @@ static char *libthread_db_search_path;
    by the "set auto-load libthread-db" command.  */
 static int auto_load_thread_db = 1;
 
+/* Set to non-zero if load-time libthread_db tests have been enabled
+   by the "maintenence set check-libthread-db" command.  */
+static int check_thread_db_on_load = 0;
+
 /* "show" command for the auto_load_thread_db configuration variable.  */
 
 static void
@@ -534,6 +539,250 @@ dladdr_to_soname (const void *addr)
   return NULL;
 }
 
+/* State for check_thread_db_callback.  */
+
+struct check_thread_db_info
+{
+  /* The libthread_db under test.  */
+  struct thread_db_info *info;
+
+  /* True if progress should be logged.  */
+  bool log_progress;
+
+  /* True if the callback was called.  */
+  bool threads_seen;
+
+  /* Name of last libthread_db function called.  */
+  const char *last_call;
+
+  /* Value returned by last libthread_db call.  */
+  td_err_e last_result;
+};
+
+static struct check_thread_db_info *tdb_testinfo;
+
+/* Callback for check_thread_db.  */
+
+static int
+check_thread_db_callback (const td_thrhandle_t *th, void *arg)
+{
+  gdb_assert (tdb_testinfo != NULL);
+  tdb_testinfo->threads_seen = true;
+
+#define LOG(fmt, args...)						\
+  do									\
+    {									\
+      if (tdb_testinfo->log_progress)					\
+	{								\
+	  debug_printf (fmt, ## args);					\
+	  gdb_flush (gdb_stdlog);					\
+	}								\
+    }									\
+  while (0)
+
+#define CHECK_1(expr, args...)						\
+  do									\
+    {									\
+      if (!(expr))							\
+	{								\
+	  LOG (" ... FAIL!\n");						\
+	  error (args);							\
+	}								\
+    }									\
+  while (0)
+
+#define CHECK(expr)							\
+  CHECK_1 (expr, "(%s) == false", #expr)
+
+#define CALL_UNCHECKED(func, args...)					\
+  do									\
+    {									\
+      tdb_testinfo->last_call = #func;					\
+      tdb_testinfo->last_result						\
+	= tdb_testinfo->info->func ## _p (args);			\
+    }									\
+  while (0)
+
+#define CHECK_CALL()							\
+  CHECK_1 (tdb_testinfo->last_result == TD_OK,				\
+	   _("%s failed: %s"),						\
+	   tdb_testinfo->last_call,					\
+	   thread_db_err_str (tdb_testinfo->last_result))		\
+
+#define CALL(func, args...)						\
+  do									\
+    {									\
+      CALL_UNCHECKED (func, args);					\
+      CHECK_CALL ();							\
+    }									\
+  while (0)
+
+  LOG ("  Got thread");
+
+  /* Check td_ta_thr_iter passed consistent arguments.  */
+  CHECK (th != NULL);
+  CHECK (arg == (void *) tdb_testinfo);
+  CHECK (th->th_ta_p == tdb_testinfo->info->thread_agent);
+
+  LOG (" %s", core_addr_to_string_nz ((CORE_ADDR) th->th_unique));
+
+  /* Check td_thr_get_info.  */
+  td_thrinfo_t ti;
+  CALL (td_thr_get_info, th, &ti);
+
+  LOG (" => %d", ti.ti_lid);
+
+  CHECK (ti.ti_ta_p == th->th_ta_p);
+  CHECK (ti.ti_tid == (thread_t) th->th_unique);
+
+  /* Check td_ta_map_lwp2thr.  */
+  td_thrhandle_t th2;
+  memset (&th2, 23, sizeof (td_thrhandle_t));
+  CALL_UNCHECKED (td_ta_map_lwp2thr, th->th_ta_p, ti.ti_lid, &th2);
+
+  if (tdb_testinfo->last_result == TD_ERR && !target_has_execution)
+    {
+      /* Some platforms require execution for td_ta_map_lwp2thr.  */
+      LOG (_("; can't map_lwp2thr"));
+    }
+  else
+    {
+      CHECK_CALL ();
+
+      LOG (" => %s", core_addr_to_string_nz ((CORE_ADDR) th2.th_unique));
+
+      CHECK (memcmp (th, &th2, sizeof (td_thrhandle_t)) == 0);
+    }
+
+  /* Attempt TLS access.  Assuming errno is TLS, this calls
+     thread_db_get_thread_local_address, which in turn calls
+     td_thr_tls_get_addr for live inferiors or td_thr_tlsbase
+     for core files.  This test is skipped if the thread has
+     not been recorded; proceeding in that case would result
+     in the test having the side-effect of noticing threads
+     which seems wrong.
+
+     Note that in glibc's libthread_db td_thr_tls_get_addr is
+     a thin wrapper around td_thr_tlsbase; this check always
+     hits the bulk of the code.
+
+     Note also that we don't actually check any libthread_db
+     calls are made, we just assume they were; future changes
+     to how GDB accesses TLS could result in this passing
+     without exercising the calls it's supposed to.  */
+  ptid_t ptid = ptid_build (tdb_testinfo->info->pid, ti.ti_lid, 0);
+  struct thread_info *thread_info = find_thread_ptid (ptid);
+  if (thread_info != NULL && thread_info->priv != NULL)
+    {
+      LOG ("; errno");
+
+      scoped_restore_current_thread restore_current_thread;
+      switch_to_thread (ptid);
+
+      expression_up expr = parse_expression ("(int) errno");
+      struct value *val = evaluate_expression (expr.get ());
+
+      if (tdb_testinfo->log_progress)
+	{
+	  struct value_print_options opts;
+
+	  get_user_print_options (&opts);
+	  LOG (" = ");
+	  value_print (val, gdb_stdlog, &opts);
+	}
+    }
+
+  LOG (" ... OK\n");
+
+#undef LOG
+#undef CHECK_1
+#undef CHECK
+#undef CALL_UNCHECKED
+#undef CHECK_CALL
+#undef CALL
+
+  return 0;
+}
+
+/* Run integrity checks on the dlopen()ed libthread_db described by
+   INFO.  Returns true on success, displays a warning and returns
+   false on failure.  Logs progress messages to gdb_stdlog during
+   the test if LOG_PROGRESS is true.  */
+
+static bool
+check_thread_db (struct thread_db_info *info, bool log_progress)
+{
+  bool test_passed = true;
+
+  if (log_progress)
+    debug_printf (_("Running libthread_db integrity checks:\n"));
+
+  /* GDB avoids using td_ta_thr_iter wherever possible (see comment
+     in try_thread_db_load_1 below) so in order to test it we may
+     have to locate it ourselves.  */
+  td_ta_thr_iter_ftype *td_ta_thr_iter_p = info->td_ta_thr_iter_p;
+  if (td_ta_thr_iter_p == NULL)
+    {
+      void *thr_iter = verbose_dlsym (info->handle, "td_ta_thr_iter");
+      if (thr_iter == NULL)
+	return 0;
+
+      td_ta_thr_iter_p = (td_ta_thr_iter_ftype *) thr_iter;
+    }
+
+  /* Set up the test state we share with the callback.  */
+  gdb_assert (tdb_testinfo == NULL);
+  struct check_thread_db_info tdb_testinfo_buf;
+  tdb_testinfo = &tdb_testinfo_buf;
+
+  memset (tdb_testinfo, 0, sizeof (struct check_thread_db_info));
+  tdb_testinfo->info = info;
+  tdb_testinfo->log_progress = log_progress;
+
+  /* td_ta_thr_iter shouldn't be used on running processes.  Note that
+     it's possible the inferior will stop midway through modifying one
+     of its thread lists, in which case the check will spuriously
+     fail.  */
+  linux_stop_and_wait_all_lwps ();
+
+  TRY
+    {
+      td_err_e err = td_ta_thr_iter_p (info->thread_agent,
+				       check_thread_db_callback,
+				       tdb_testinfo,
+				       TD_THR_ANY_STATE,
+				       TD_THR_LOWEST_PRIORITY,
+				       TD_SIGNO_MASK,
+				       TD_THR_ANY_USER_FLAGS);
+
+      if (err != TD_OK)
+	error (_("td_ta_thr_iter failed: %s"), thread_db_err_str (err));
+
+      if (!tdb_testinfo->threads_seen)
+	error (_("no threads seen"));
+    }
+  CATCH (except, RETURN_MASK_ERROR)
+    {
+      if (warning_pre_print)
+	fputs_unfiltered (warning_pre_print, gdb_stderr);
+
+      exception_fprintf (gdb_stderr, except,
+			 _("libthread_db integrity checks failed: "));
+
+      test_passed = false;
+    }
+  END_CATCH
+
+  if (test_passed && log_progress)
+    debug_printf (_("libthread_db integrity checks passed.\n"));
+
+  tdb_testinfo = NULL;
+
+  linux_unstop_all_lwps ();
+
+  return test_passed;
+}
+
 /* Attempt to initialize dlopen()ed libthread_db, described by INFO.
    Return 1 on success.
    Failure could happen if libthread_db does not have symbols we expect,
@@ -627,6 +876,13 @@ try_thread_db_load_1 (struct thread_db_info *info)
 #undef TDB_DLSYM
 #undef CHK
 
+  /* Run integrity checks if requested.  */
+  if (check_thread_db_on_load)
+    {
+      if (!check_thread_db (info, libthread_db_debug))
+	return 0;
+    }
+
   if (info->td_ta_thr_iter_p == NULL)
     {
       struct lwp_info *lp;
@@ -1658,6 +1914,24 @@ info_auto_load_libthread_db (const char *args, int from_tty)
     uiout->message (_("No auto-loaded libthread-db.\n"));
 }
 
+/* Implement 'maintenance check libthread-db'.  */
+
+static void
+maintenance_check_libthread_db (const char *args, int from_tty)
+{
+  int inferior_pid = ptid_get_pid (inferior_ptid);
+  struct thread_db_info *info;
+
+  if (inferior_pid == 0)
+    error (_("No inferior running"));
+
+  info = get_thread_db_info (inferior_pid);
+  if (info == NULL)
+    error (_("No libthread_db loaded"));
+
+  check_thread_db (info, true);
+}
+
 void
 _initialize_thread_db (void)
 {
@@ -1708,6 +1982,23 @@ This options has security implications for untrusted inferiors."),
 Usage: info auto-load libthread-db"),
 	   auto_load_info_cmdlist_get ());
 
+  add_cmd ("libthread-db", class_maintenance,
+	   maintenance_check_libthread_db, _("\
+Run integrity checks on the current inferior's libthread_db."),
+	   &maintenancechecklist);
+
+  add_setshow_boolean_cmd ("check-libthread-db",
+			   class_maintenance,
+			   &check_thread_db_on_load, _("\
+Set whether to check libthread_db at load time."), _("\
+Show whether to check libthread_db at load time."), _("\
+If enabled GDB will run integrity checks on inferior specific libthread_db\n\
+as they are loaded."),
+			   NULL,
+			   NULL,
+			   &maintenance_set_cmdlist,
+			   &maintenance_show_cmdlist);
+
   /* Add ourselves to objfile event chain.  */
   gdb::observers::new_objfile.attach (thread_db_new_objfile);
 
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
+    }
+}
-- 
1.8.3.1

[PATCH] Fix ref in gdb.texinfo

[Szabolcs Nagy]

[-- Attachment #1: Type: text/plain, Size: 502 bytes --]

Since

commit 5045b3d78903d1f6faa4cb511fa801e50dfacf48
Commit:     Gary Benson <gbenson@redhat.com>
CommitDate: 2018-06-08 18:06:46 +0100

     linux: Add maintenance commands to test libthread_db

The build fails for me with

../../../gdb/doc/gdb.texinfo:35875: @ref reference to nonexistent node `maint check libthread-db'
Makefile:486: recipe for target 'gdb.info' failed

gdb/doc/ChangeLog:
2018-06-11  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* gdb.texinfo (maint check libthread-db): Add anchor.

[-- Attachment #2: gdbdoc.diff --]
[-- Type: text/x-patch, Size: 506 bytes --]

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 2c0ac33f8b..2b56b5ab21 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35547,6 +35547,7 @@ modify XML target descriptions.
 Check that the target descriptions dynamically created by @value{GDBN}
 equal the descriptions created from XML files found in @var{dir}.
 
+@anchor{maint check libthread-db}
 @kindex maint check libthread-db
 @item maint check libthread-db
 Run integrity checks on the current inferior's thread debugging

Re: [PATCH] Fix ref in gdb.texinfo

[Eli Zaretskii]

> From: Szabolcs Nagy <szabolcs.nagy@arm.com>
> Date: Mon, 11 Jun 2018 18:15:12 +0100
> 
> commit 5045b3d78903d1f6faa4cb511fa801e50dfacf48
> Commit:     Gary Benson <gbenson@redhat.com>
> CommitDate: 2018-06-08 18:06:46 +0100
> 
>      linux: Add maintenance commands to test libthread_db
> 
> The build fails for me with
> 
> ../../../gdb/doc/gdb.texinfo:35875: @ref reference to nonexistent node `maint check libthread-db'
> Makefile:486: recipe for target 'gdb.info' failed

Please try again, I hope I fixed that.