diff mbox

linux: Add maintenance commands to test libthread_db

Message ID 1511361761-1333-1-git-send-email-gbenson@redhat.com
State New
Headers show

Commit Message

Gary Benson Nov. 22, 2017, 2:42 p.m. UTC
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

Comments

Simon Marchi Nov. 22, 2017, 7:30 p.m. UTC | #1
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
Pedro Alves Nov. 23, 2017, 1:22 p.m. UTC | #2
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
diff mbox

Patch

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