1 /* libthread_db assisted debugging support, generic parts.
3 Copyright (C) 1999, 2000, 2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 2010, 2011 Free Software Foundation, Inc.
6 This file is part of GDB.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program. If not, see <http://www.gnu.org/licenses/>. */
23 #include "gdb_assert.h"
25 #include "gdb_proc_service.h"
26 #include "gdb_thread_db.h"
30 #include "exceptions.h"
32 #include "gdbthread.h"
39 #include "solib-svr4.h"
42 #include "linux-nat.h"
46 #ifdef HAVE_GNU_LIBC_VERSION_H
47 #include <gnu/libc-version.h>
50 /* GNU/Linux libthread_db support.
52 libthread_db is a library, provided along with libpthread.so, which
53 exposes the internals of the thread library to a debugger. It
54 allows GDB to find existing threads, new threads as they are
55 created, thread IDs (usually, the result of pthread_self), and
56 thread-local variables.
58 The libthread_db interface originates on Solaris, where it is
59 both more powerful and more complicated. This implementation
60 only works for LinuxThreads and NPTL, the two glibc threading
61 libraries. It assumes that each thread is permanently assigned
62 to a single light-weight process (LWP).
64 libthread_db-specific information is stored in the "private" field
65 of struct thread_info. When the field is NULL we do not yet have
66 information about the new thread; this could be temporary (created,
67 but the thread library's data structures do not reflect it yet)
68 or permanent (created using clone instead of pthread_create).
70 Process IDs managed by linux-thread-db.c match those used by
71 linux-nat.c: a common PID for all processes, an LWP ID for each
72 thread, and no TID. We save the TID in private. Keeping it out
73 of the ptid_t prevents thread IDs changing when libpthread is
74 loaded or unloaded. */
76 static char *libthread_db_search_path;
79 set_libthread_db_search_path (char *ignored, int from_tty,
80 struct cmd_list_element *c)
82 if (*libthread_db_search_path == '\0')
84 xfree (libthread_db_search_path);
85 libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
89 /* If non-zero, print details of libthread_db processing. */
91 static int libthread_db_debug;
94 show_libthread_db_debug (struct ui_file *file, int from_tty,
95 struct cmd_list_element *c, const char *value)
97 fprintf_filtered (file, _("libthread-db debugging is %s.\n"), value);
100 /* If we're running on GNU/Linux, we must explicitly attach to any new
103 /* This module's target vector. */
104 static struct target_ops thread_db_ops;
106 /* Non-zero if we have determined the signals used by the threads
108 static int thread_signals;
109 static sigset_t thread_stop_set;
110 static sigset_t thread_print_set;
112 struct thread_db_info
114 struct thread_db_info *next;
116 /* Process id this object refers to. */
119 /* Handle from dlopen for libthread_db.so. */
122 /* Structure that identifies the child process for the
123 <proc_service.h> interface. */
124 struct ps_prochandle proc_handle;
126 /* Connection to the libthread_db library. */
127 td_thragent_t *thread_agent;
129 /* True if we need to apply the workaround for glibc/BZ5983. When
130 we catch a PTRACE_O_TRACEFORK, and go query the child's thread
131 list, nptl_db returns the parent's threads in addition to the new
132 (single) child thread. If this flag is set, we do extra work to
133 be able to ignore such stale entries. */
134 int need_stale_parent_threads_check;
136 /* Location of the thread creation event breakpoint. The code at
137 this location in the child process will be called by the pthread
138 library whenever a new thread is created. By setting a special
139 breakpoint at this location, GDB can detect when a new thread is
140 created. We obtain this location via the td_ta_event_addr
142 CORE_ADDR td_create_bp_addr;
144 /* Location of the thread death event breakpoint. */
145 CORE_ADDR td_death_bp_addr;
147 /* Pointers to the libthread_db functions. */
149 td_err_e (*td_init_p) (void);
151 td_err_e (*td_ta_new_p) (struct ps_prochandle * ps,
153 td_err_e (*td_ta_map_id2thr_p) (const td_thragent_t *ta, thread_t pt,
154 td_thrhandle_t *__th);
155 td_err_e (*td_ta_map_lwp2thr_p) (const td_thragent_t *ta,
156 lwpid_t lwpid, td_thrhandle_t *th);
157 td_err_e (*td_ta_thr_iter_p) (const td_thragent_t *ta,
158 td_thr_iter_f *callback, void *cbdata_p,
159 td_thr_state_e state, int ti_pri,
160 sigset_t *ti_sigmask_p,
161 unsigned int ti_user_flags);
162 td_err_e (*td_ta_event_addr_p) (const td_thragent_t *ta,
163 td_event_e event, td_notify_t *ptr);
164 td_err_e (*td_ta_set_event_p) (const td_thragent_t *ta,
165 td_thr_events_t *event);
166 td_err_e (*td_ta_clear_event_p) (const td_thragent_t *ta,
167 td_thr_events_t *event);
168 td_err_e (*td_ta_event_getmsg_p) (const td_thragent_t *ta,
169 td_event_msg_t *msg);
171 td_err_e (*td_thr_validate_p) (const td_thrhandle_t *th);
172 td_err_e (*td_thr_get_info_p) (const td_thrhandle_t *th,
173 td_thrinfo_t *infop);
174 td_err_e (*td_thr_event_enable_p) (const td_thrhandle_t *th,
177 td_err_e (*td_thr_tls_get_addr_p) (const td_thrhandle_t *th,
178 psaddr_t map_address,
179 size_t offset, psaddr_t *address);
182 /* List of known processes using thread_db, and the required
184 struct thread_db_info *thread_db_list;
186 static void thread_db_find_new_threads_1 (ptid_t ptid);
187 static void thread_db_find_new_threads_2 (ptid_t ptid, int until_no_new);
189 /* Add the current inferior to the list of processes using libpthread.
190 Return a pointer to the newly allocated object that was added to
191 THREAD_DB_LIST. HANDLE is the handle returned by dlopen'ing
194 static struct thread_db_info *
195 add_thread_db_info (void *handle)
197 struct thread_db_info *info;
199 info = xcalloc (1, sizeof (*info));
200 info->pid = ptid_get_pid (inferior_ptid);
201 info->handle = handle;
203 /* The workaround works by reading from /proc/pid/status, so it is
204 disabled for core files. */
205 if (target_has_execution)
206 info->need_stale_parent_threads_check = 1;
208 info->next = thread_db_list;
209 thread_db_list = info;
214 /* Return the thread_db_info object representing the bookkeeping
215 related to process PID, if any; NULL otherwise. */
217 static struct thread_db_info *
218 get_thread_db_info (int pid)
220 struct thread_db_info *info;
222 for (info = thread_db_list; info; info = info->next)
223 if (pid == info->pid)
229 /* When PID has exited or has been detached, we no longer want to keep
230 track of it as using libpthread. Call this function to discard
231 thread_db related info related to PID. Note that this closes
232 LIBTHREAD_DB_SO's dlopen'ed handle. */
235 delete_thread_db_info (int pid)
237 struct thread_db_info *info, *info_prev;
241 for (info = thread_db_list; info; info_prev = info, info = info->next)
242 if (pid == info->pid)
248 if (info->handle != NULL)
249 dlclose (info->handle);
252 info_prev->next = info->next;
254 thread_db_list = info->next;
259 /* Prototypes for local functions. */
260 static int attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
261 const td_thrinfo_t *ti_p);
262 static void detach_thread (ptid_t ptid);
265 /* Use "struct private_thread_info" to cache thread state. This is
266 a substantial optimization. */
268 struct private_thread_info
270 /* Flag set when we see a TD_DEATH event for this thread. */
271 unsigned int dying:1;
273 /* Cached thread state. */
280 thread_db_err_str (td_err_e err)
287 return "generic 'call succeeded'";
289 return "generic error";
291 return "no thread to satisfy query";
293 return "no sync handle to satisfy query";
295 return "no LWP to satisfy query";
297 return "invalid process handle";
299 return "invalid thread handle";
301 return "invalid synchronization handle";
303 return "invalid thread agent";
305 return "invalid key";
307 return "no event message for getmsg";
309 return "FPU register set not available";
311 return "application not linked with libthread";
313 return "requested event is not supported";
315 return "capability not available";
317 return "debugger service failed";
319 return "operation not applicable to";
321 return "no thread-specific data for this thread";
323 return "malloc failed";
325 return "only part of register set was written/read";
327 return "X register set not available for this thread";
328 #ifdef THREAD_DB_HAS_TD_NOTALLOC
330 return "thread has not yet allocated TLS for given module";
332 #ifdef THREAD_DB_HAS_TD_VERSION
334 return "versions of libpthread and libthread_db do not match";
336 #ifdef THREAD_DB_HAS_TD_NOTLS
338 return "there is no TLS segment in the given module";
341 snprintf (buf, sizeof (buf), "unknown thread_db error '%d'", err);
346 /* Return 1 if any threads have been registered. There may be none if
347 the threading library is not fully initialized yet. */
350 have_threads_callback (struct thread_info *thread, void *args)
352 int pid = * (int *) args;
354 if (ptid_get_pid (thread->ptid) != pid)
357 return thread->private != NULL;
361 have_threads (ptid_t ptid)
363 int pid = ptid_get_pid (ptid);
365 return iterate_over_threads (have_threads_callback, &pid) != NULL;
368 struct thread_get_info_inout
370 struct thread_info *thread_info;
371 struct thread_db_info *thread_db_info;
374 /* A callback function for td_ta_thr_iter, which we use to map all
377 THP is a handle to the current thread; if INFOP is not NULL, the
378 struct thread_info associated with this thread is returned in
381 If the thread is a zombie, TD_THR_ZOMBIE is returned. Otherwise,
382 zero is returned to indicate success. */
385 thread_get_info_callback (const td_thrhandle_t *thp, void *argp)
390 struct thread_get_info_inout *inout;
391 struct thread_db_info *info;
394 info = inout->thread_db_info;
396 err = info->td_thr_get_info_p (thp, &ti);
398 error (_("thread_get_info_callback: cannot get thread info: %s"),
399 thread_db_err_str (err));
401 /* Fill the cache. */
402 thread_ptid = ptid_build (info->pid, ti.ti_lid, 0);
403 inout->thread_info = find_thread_ptid (thread_ptid);
405 /* In the case of a zombie thread, don't continue. We don't want to
406 attach to it thinking it is a new thread. */
407 if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE)
408 return TD_THR_ZOMBIE;
410 if (inout->thread_info == NULL)
412 /* New thread. Attach to it now (why wait?). */
413 if (!have_threads (thread_ptid))
414 thread_db_find_new_threads_1 (thread_ptid);
416 attach_thread (thread_ptid, thp, &ti);
417 inout->thread_info = find_thread_ptid (thread_ptid);
418 gdb_assert (inout->thread_info != NULL);
424 /* Convert between user-level thread ids and LWP ids. */
427 thread_from_lwp (ptid_t ptid)
431 struct thread_db_info *info;
432 struct thread_get_info_inout io = {0};
434 /* This ptid comes from linux-nat.c, which should always fill in the
436 gdb_assert (GET_LWP (ptid) != 0);
438 info = get_thread_db_info (GET_PID (ptid));
440 /* Access an lwp we know is stopped. */
441 info->proc_handle.ptid = ptid;
442 err = info->td_ta_map_lwp2thr_p (info->thread_agent, GET_LWP (ptid), &th);
444 error (_("Cannot find user-level thread for LWP %ld: %s"),
445 GET_LWP (ptid), thread_db_err_str (err));
447 /* Fetch the thread info. If we get back TD_THR_ZOMBIE, then the
448 event thread has already died. If another gdb interface has called
449 thread_alive() previously, the thread won't be found on the thread list
450 anymore. In that case, we don't want to process this ptid anymore
451 to avoid the possibility of later treating it as a newly
452 discovered thread id that we should add to the list. Thus,
453 we return a -1 ptid which is also how the thread list marks a
455 io.thread_db_info = info;
456 io.thread_info = NULL;
457 if (thread_get_info_callback (&th, &io) == TD_THR_ZOMBIE
458 && io.thread_info == NULL)
459 return minus_one_ptid;
461 gdb_assert (ptid_get_tid (ptid) == 0);
466 /* Attach to lwp PTID, doing whatever else is required to have this
467 LWP under the debugger's control --- e.g., enabling event
468 reporting. Returns true on success. */
470 thread_db_attach_lwp (ptid_t ptid)
475 struct thread_db_info *info;
477 info = get_thread_db_info (GET_PID (ptid));
482 /* This ptid comes from linux-nat.c, which should always fill in the
484 gdb_assert (GET_LWP (ptid) != 0);
486 /* Access an lwp we know is stopped. */
487 info->proc_handle.ptid = ptid;
489 /* If we have only looked at the first thread before libpthread was
490 initialized, we may not know its thread ID yet. Make sure we do
491 before we add another thread to the list. */
492 if (!have_threads (ptid))
493 thread_db_find_new_threads_1 (ptid);
495 err = info->td_ta_map_lwp2thr_p (info->thread_agent, GET_LWP (ptid), &th);
497 /* Cannot find user-level thread. */
500 err = info->td_thr_get_info_p (&th, &ti);
503 warning (_("Cannot get thread info: %s"), thread_db_err_str (err));
507 attach_thread (ptid, &th, &ti);
512 verbose_dlsym (void *handle, const char *name)
514 void *sym = dlsym (handle, name);
516 warning (_("Symbol \"%s\" not found in libthread_db: %s"),
522 enable_thread_event (int event, CORE_ADDR *bp)
526 struct thread_db_info *info;
528 info = get_thread_db_info (GET_PID (inferior_ptid));
530 /* Access an lwp we know is stopped. */
531 info->proc_handle.ptid = inferior_ptid;
533 /* Get the breakpoint address for thread EVENT. */
534 err = info->td_ta_event_addr_p (info->thread_agent, event, ¬ify);
538 /* Set up the breakpoint. */
539 gdb_assert (exec_bfd);
540 (*bp) = (gdbarch_convert_from_func_ptr_addr
542 /* Do proper sign extension for the target. */
543 (bfd_get_sign_extend_vma (exec_bfd) > 0
544 ? (CORE_ADDR) (intptr_t) notify.u.bptaddr
545 : (CORE_ADDR) (uintptr_t) notify.u.bptaddr),
547 create_thread_event_breakpoint (target_gdbarch, *bp);
553 enable_thread_event_reporting (void)
555 td_thr_events_t events;
557 #ifdef HAVE_GNU_LIBC_VERSION_H
558 const char *libc_version;
559 int libc_major, libc_minor;
561 struct thread_db_info *info;
563 info = get_thread_db_info (GET_PID (inferior_ptid));
565 /* We cannot use the thread event reporting facility if these
566 functions aren't available. */
567 if (info->td_ta_event_addr_p == NULL
568 || info->td_ta_set_event_p == NULL
569 || info->td_ta_event_getmsg_p == NULL
570 || info->td_thr_event_enable_p == NULL)
573 /* Set the process wide mask saying which events we're interested in. */
574 td_event_emptyset (&events);
575 td_event_addset (&events, TD_CREATE);
577 #ifdef HAVE_GNU_LIBC_VERSION_H
578 /* The event reporting facility is broken for TD_DEATH events in
579 glibc 2.1.3, so don't enable it if we have glibc but a lower
581 libc_version = gnu_get_libc_version ();
582 if (sscanf (libc_version, "%d.%d", &libc_major, &libc_minor) == 2
583 && (libc_major > 2 || (libc_major == 2 && libc_minor > 1)))
585 td_event_addset (&events, TD_DEATH);
587 err = info->td_ta_set_event_p (info->thread_agent, &events);
590 warning (_("Unable to set global thread event mask: %s"),
591 thread_db_err_str (err));
595 /* Delete previous thread event breakpoints, if any. */
596 remove_thread_event_breakpoints ();
597 info->td_create_bp_addr = 0;
598 info->td_death_bp_addr = 0;
600 /* Set up the thread creation event. */
601 err = enable_thread_event (TD_CREATE, &info->td_create_bp_addr);
604 warning (_("Unable to get location for thread creation breakpoint: %s"),
605 thread_db_err_str (err));
609 /* Set up the thread death event. */
610 err = enable_thread_event (TD_DEATH, &info->td_death_bp_addr);
613 warning (_("Unable to get location for thread death breakpoint: %s"),
614 thread_db_err_str (err));
619 /* Same as thread_db_find_new_threads_1, but silently ignore errors. */
622 thread_db_find_new_threads_silently (ptid_t ptid)
624 volatile struct gdb_exception except;
626 TRY_CATCH (except, RETURN_MASK_ERROR)
628 thread_db_find_new_threads_2 (ptid, 1);
631 if (except.reason < 0 && libthread_db_debug)
633 exception_fprintf (gdb_stderr, except,
634 "Warning: thread_db_find_new_threads_silently: ");
638 /* Lookup a library in which given symbol resides.
639 Note: this is looking in GDB process, not in the inferior.
640 Returns library name, or NULL. */
643 dladdr_to_soname (const void *addr)
647 if (dladdr (addr, &info) != 0)
648 return info.dli_fname;
652 /* Attempt to initialize dlopen()ed libthread_db, described by INFO.
654 Failure could happen if libthread_db does not have symbols we expect,
655 or when it refuses to work with the current inferior (e.g. due to
656 version mismatch between libthread_db and libpthread). */
659 try_thread_db_load_1 (struct thread_db_info *info)
663 /* Initialize pointers to the dynamic library functions we will use.
664 Essential functions first. */
666 info->td_init_p = verbose_dlsym (info->handle, "td_init");
667 if (info->td_init_p == NULL)
670 err = info->td_init_p ();
673 warning (_("Cannot initialize libthread_db: %s"),
674 thread_db_err_str (err));
678 info->td_ta_new_p = verbose_dlsym (info->handle, "td_ta_new");
679 if (info->td_ta_new_p == NULL)
682 /* Initialize the structure that identifies the child process. */
683 info->proc_handle.ptid = inferior_ptid;
685 /* Now attempt to open a connection to the thread library. */
686 err = info->td_ta_new_p (&info->proc_handle, &info->thread_agent);
689 if (libthread_db_debug)
690 printf_unfiltered (_("td_ta_new failed: %s\n"),
691 thread_db_err_str (err));
696 #ifdef THREAD_DB_HAS_TD_VERSION
699 /* The errors above are not unexpected and silently ignored:
700 they just mean we haven't found correct version of
704 warning (_("td_ta_new failed: %s"), thread_db_err_str (err));
709 info->td_ta_map_id2thr_p = verbose_dlsym (info->handle, "td_ta_map_id2thr");
710 if (info->td_ta_map_id2thr_p == NULL)
713 info->td_ta_map_lwp2thr_p = verbose_dlsym (info->handle,
714 "td_ta_map_lwp2thr");
715 if (info->td_ta_map_lwp2thr_p == NULL)
718 info->td_ta_thr_iter_p = verbose_dlsym (info->handle, "td_ta_thr_iter");
719 if (info->td_ta_thr_iter_p == NULL)
722 info->td_thr_validate_p = verbose_dlsym (info->handle, "td_thr_validate");
723 if (info->td_thr_validate_p == NULL)
726 info->td_thr_get_info_p = verbose_dlsym (info->handle, "td_thr_get_info");
727 if (info->td_thr_get_info_p == NULL)
730 /* These are not essential. */
731 info->td_ta_event_addr_p = dlsym (info->handle, "td_ta_event_addr");
732 info->td_ta_set_event_p = dlsym (info->handle, "td_ta_set_event");
733 info->td_ta_clear_event_p = dlsym (info->handle, "td_ta_clear_event");
734 info->td_ta_event_getmsg_p = dlsym (info->handle, "td_ta_event_getmsg");
735 info->td_thr_event_enable_p = dlsym (info->handle, "td_thr_event_enable");
736 info->td_thr_tls_get_addr_p = dlsym (info->handle, "td_thr_tls_get_addr");
738 printf_unfiltered (_("[Thread debugging using libthread_db enabled]\n"));
740 if (libthread_db_debug || *libthread_db_search_path)
744 library = dladdr_to_soname (*info->td_ta_new_p);
746 library = LIBTHREAD_DB_SO;
748 printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
752 /* The thread library was detected. Activate the thread_db target
753 if this is the first process using it. */
754 if (thread_db_list->next == NULL)
755 push_target (&thread_db_ops);
757 /* Enable event reporting, but not when debugging a core file. */
758 if (target_has_execution)
759 enable_thread_event_reporting ();
761 /* There appears to be a bug in glibc-2.3.6: calls to td_thr_get_info fail
762 with TD_ERR for statically linked executables if td_thr_get_info is
763 called before glibc has initialized itself. Silently ignore such
764 errors, and let gdb enumerate threads again later. */
765 thread_db_find_new_threads_silently (inferior_ptid);
770 /* Attempt to use LIBRARY as libthread_db. LIBRARY could be absolute,
771 relative, or just LIBTHREAD_DB. */
774 try_thread_db_load (const char *library)
777 struct thread_db_info *info;
779 if (libthread_db_debug)
780 printf_unfiltered (_("Trying host libthread_db library: %s.\n"),
782 handle = dlopen (library, RTLD_NOW);
785 if (libthread_db_debug)
786 printf_unfiltered (_("dlopen failed: %s.\n"), dlerror ());
790 if (libthread_db_debug && strchr (library, '/') == NULL)
794 td_init = dlsym (handle, "td_init");
797 const char *const libpath = dladdr_to_soname (td_init);
800 printf_unfiltered (_("Host %s resolved to: %s.\n"),
805 info = add_thread_db_info (handle);
807 if (try_thread_db_load_1 (info))
810 /* This library "refused" to work on current inferior. */
811 delete_thread_db_info (GET_PID (inferior_ptid));
815 /* Search libthread_db_search_path for libthread_db which "agrees"
816 to work on current inferior. */
819 thread_db_load_search (void)
822 const char *search_path = libthread_db_search_path;
827 const char *end = strchr (search_path, ':');
831 size_t len = end - search_path;
833 if (len + 1 + strlen (LIBTHREAD_DB_SO) + 1 > sizeof (path))
835 char *cp = xmalloc (len + 1);
837 memcpy (cp, search_path, len);
839 warning (_("libthread_db_search_path component too long,"
840 " ignored: %s."), cp);
842 search_path += len + 1;
845 memcpy (path, search_path, len);
847 search_path += len + 1;
851 size_t len = strlen (search_path);
853 if (len + 1 + strlen (LIBTHREAD_DB_SO) + 1 > sizeof (path))
855 warning (_("libthread_db_search_path component too long,"
856 " ignored: %s."), search_path);
859 memcpy (path, search_path, len + 1);
863 strcat (path, LIBTHREAD_DB_SO);
864 if (try_thread_db_load (path))
871 rc = try_thread_db_load (LIBTHREAD_DB_SO);
875 /* Attempt to load and initialize libthread_db.
876 Return 1 on success. */
879 thread_db_load (void)
882 struct thread_db_info *info;
884 info = get_thread_db_info (GET_PID (inferior_ptid));
889 /* Don't attempt to use thread_db on executables not running
891 if (!target_has_registers)
894 /* Don't attempt to use thread_db for remote targets. */
895 if (!(target_can_run (¤t_target) || core_bfd))
898 if (thread_db_load_search ())
901 /* None of the libthread_db's on our search path, not the system default
902 ones worked. If the executable is dynamically linked against
903 libpthread, try loading libthread_db from the same directory. */
906 if (libpthread_name_p (obj->name))
908 char path[PATH_MAX], *cp;
910 gdb_assert (strlen (obj->name) < sizeof (path));
911 strcpy (path, obj->name);
912 cp = strrchr (path, '/');
916 warning (_("Expected absolute pathname for libpthread in the"
917 " inferior, but got %s."), path);
919 else if (cp + 1 + strlen (LIBTHREAD_DB_SO) + 1 > path + sizeof (path))
921 warning (_("Unexpected: path to libpthread in the inferior is"
922 " too long: %s"), path);
926 strcpy (cp + 1, LIBTHREAD_DB_SO);
927 if (try_thread_db_load (path))
930 warning (_("Unable to find libthread_db matching inferior's thread"
931 " library, thread debugging will not be available."));
934 /* Either this executable isn't using libpthread at all, or it is
935 statically linked. Since we can't easily distinguish these two cases,
936 no warning is issued. */
941 disable_thread_event_reporting (struct thread_db_info *info)
943 if (info->td_ta_clear_event_p != NULL)
945 td_thr_events_t events;
947 /* Set the process wide mask saying we aren't interested in any
949 td_event_fillset (&events);
950 info->td_ta_clear_event_p (info->thread_agent, &events);
953 info->td_create_bp_addr = 0;
954 info->td_death_bp_addr = 0;
958 check_thread_signals (void)
965 lin_thread_get_thread_signals (&mask);
966 sigemptyset (&thread_stop_set);
967 sigemptyset (&thread_print_set);
969 for (i = 1; i < NSIG; i++)
971 if (sigismember (&mask, i))
973 if (signal_stop_update (target_signal_from_host (i), 0))
974 sigaddset (&thread_stop_set, i);
975 if (signal_print_update (target_signal_from_host (i), 0))
976 sigaddset (&thread_print_set, i);
983 /* Check whether thread_db is usable. This function is called when
984 an inferior is created (or otherwise acquired, e.g. attached to)
985 and when new shared libraries are loaded into a running process. */
988 check_for_thread_db (void)
990 /* Do nothing if we couldn't load libthread_db.so.1. */
991 if (!thread_db_load ())
996 thread_db_new_objfile (struct objfile *objfile)
998 /* This observer must always be called with inferior_ptid set
1001 if (objfile != NULL)
1002 check_for_thread_db ();
1005 /* Attach to a new thread. This function is called when we receive a
1006 TD_CREATE event or when we iterate over all threads and find one
1007 that wasn't already in our list. Returns true on success. */
1010 attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
1011 const td_thrinfo_t *ti_p)
1013 struct private_thread_info *private;
1014 struct thread_info *tp = NULL;
1016 struct thread_db_info *info;
1018 /* If we're being called after a TD_CREATE event, we may already
1019 know about this thread. There are two ways this can happen. We
1020 may have iterated over all threads between the thread creation
1021 and the TD_CREATE event, for instance when the user has issued
1022 the `info threads' command before the SIGTRAP for hitting the
1023 thread creation breakpoint was reported. Alternatively, the
1024 thread may have exited and a new one been created with the same
1025 thread ID. In the first case we don't need to do anything; in
1026 the second case we should discard information about the dead
1027 thread and attach to the new one. */
1028 if (in_thread_list (ptid))
1030 tp = find_thread_ptid (ptid);
1031 gdb_assert (tp != NULL);
1033 /* If tp->private is NULL, then GDB is already attached to this
1034 thread, but we do not know anything about it. We can learn
1035 about it here. This can only happen if we have some other
1036 way besides libthread_db to notice new threads (i.e.
1037 PTRACE_EVENT_CLONE); assume the same mechanism notices thread
1038 exit, so this can not be a stale thread recreated with the
1040 if (tp->private != NULL)
1042 if (!tp->private->dying)
1045 delete_thread (ptid);
1050 if (target_has_execution)
1051 check_thread_signals ();
1053 if (ti_p->ti_state == TD_THR_UNKNOWN || ti_p->ti_state == TD_THR_ZOMBIE)
1054 return 0; /* A zombie thread -- do not attach. */
1056 /* Under GNU/Linux, we have to attach to each and every thread. */
1057 if (target_has_execution
1059 && lin_lwp_attach_lwp (BUILD_LWP (ti_p->ti_lid, GET_PID (ptid))) < 0)
1062 /* Construct the thread's private data. */
1063 private = xmalloc (sizeof (struct private_thread_info));
1064 memset (private, 0, sizeof (struct private_thread_info));
1066 /* A thread ID of zero may mean the thread library has not initialized
1067 yet. But we shouldn't even get here if that's the case. FIXME:
1068 if we change GDB to always have at least one thread in the thread
1069 list this will have to go somewhere else; maybe private == NULL
1070 until the thread_db target claims it. */
1071 gdb_assert (ti_p->ti_tid != 0);
1072 private->th = *th_p;
1073 private->tid = ti_p->ti_tid;
1075 /* Add the thread to GDB's thread list. */
1077 add_thread_with_info (ptid, private);
1079 tp->private = private;
1081 info = get_thread_db_info (GET_PID (ptid));
1083 /* Enable thread event reporting for this thread, except when
1084 debugging a core file. */
1085 if (target_has_execution)
1087 err = info->td_thr_event_enable_p (th_p, 1);
1089 error (_("Cannot enable thread event reporting for %s: %s"),
1090 target_pid_to_str (ptid), thread_db_err_str (err));
1097 detach_thread (ptid_t ptid)
1099 struct thread_info *thread_info;
1101 /* Don't delete the thread now, because it still reports as active
1102 until it has executed a few instructions after the event
1103 breakpoint - if we deleted it now, "info threads" would cause us
1104 to re-attach to it. Just mark it as having had a TD_DEATH
1105 event. This means that we won't delete it from our thread list
1106 until we notice that it's dead (via prune_threads), or until
1107 something re-uses its thread ID. We'll report the thread exit
1108 when the underlying LWP dies. */
1109 thread_info = find_thread_ptid (ptid);
1110 gdb_assert (thread_info != NULL && thread_info->private != NULL);
1111 thread_info->private->dying = 1;
1115 thread_db_detach (struct target_ops *ops, char *args, int from_tty)
1117 struct target_ops *target_beneath = find_target_beneath (ops);
1118 struct thread_db_info *info;
1120 info = get_thread_db_info (GET_PID (inferior_ptid));
1124 if (target_has_execution)
1126 disable_thread_event_reporting (info);
1128 /* Delete the old thread event breakpoints. Note that
1129 unlike when mourning, we can remove them here because
1130 there's still a live inferior to poke at. In any case,
1131 GDB will not try to insert anything in the inferior when
1132 removing a breakpoint. */
1133 remove_thread_event_breakpoints ();
1136 delete_thread_db_info (GET_PID (inferior_ptid));
1139 target_beneath->to_detach (target_beneath, args, from_tty);
1141 /* NOTE: From this point on, inferior_ptid is null_ptid. */
1143 /* If there are no more processes using libpthread, detach the
1144 thread_db target ops. */
1145 if (!thread_db_list)
1146 unpush_target (&thread_db_ops);
1149 /* Check if PID is currently stopped at the location of a thread event
1150 breakpoint location. If it is, read the event message and act upon
1154 check_event (ptid_t ptid)
1156 struct regcache *regcache = get_thread_regcache (ptid);
1157 struct gdbarch *gdbarch = get_regcache_arch (regcache);
1163 struct thread_db_info *info;
1165 info = get_thread_db_info (GET_PID (ptid));
1167 /* Bail out early if we're not at a thread event breakpoint. */
1168 stop_pc = regcache_read_pc (regcache)
1169 - gdbarch_decr_pc_after_break (gdbarch);
1170 if (stop_pc != info->td_create_bp_addr
1171 && stop_pc != info->td_death_bp_addr)
1174 /* Access an lwp we know is stopped. */
1175 info->proc_handle.ptid = ptid;
1177 /* If we have only looked at the first thread before libpthread was
1178 initialized, we may not know its thread ID yet. Make sure we do
1179 before we add another thread to the list. */
1180 if (!have_threads (ptid))
1181 thread_db_find_new_threads_1 (ptid);
1183 /* If we are at a create breakpoint, we do not know what new lwp
1184 was created and cannot specifically locate the event message for it.
1185 We have to call td_ta_event_getmsg() to get
1186 the latest message. Since we have no way of correlating whether
1187 the event message we get back corresponds to our breakpoint, we must
1188 loop and read all event messages, processing them appropriately.
1189 This guarantees we will process the correct message before continuing
1190 from the breakpoint.
1192 Currently, death events are not enabled. If they are enabled,
1193 the death event can use the td_thr_event_getmsg() interface to
1194 get the message specifically for that lwp and avoid looping
1201 err = info->td_ta_event_getmsg_p (info->thread_agent, &msg);
1204 if (err == TD_NOMSG)
1207 error (_("Cannot get thread event message: %s"),
1208 thread_db_err_str (err));
1211 err = info->td_thr_get_info_p (msg.th_p, &ti);
1213 error (_("Cannot get thread info: %s"), thread_db_err_str (err));
1215 ptid = ptid_build (GET_PID (ptid), ti.ti_lid, 0);
1220 /* Call attach_thread whether or not we already know about a
1221 thread with this thread ID. */
1222 attach_thread (ptid, msg.th_p, &ti);
1228 if (!in_thread_list (ptid))
1229 error (_("Spurious thread death event."));
1231 detach_thread (ptid);
1236 error (_("Spurious thread event."));
1243 thread_db_wait (struct target_ops *ops,
1244 ptid_t ptid, struct target_waitstatus *ourstatus,
1247 struct thread_db_info *info;
1248 struct target_ops *beneath = find_target_beneath (ops);
1250 ptid = beneath->to_wait (beneath, ptid, ourstatus, options);
1252 if (ourstatus->kind == TARGET_WAITKIND_IGNORE)
1255 if (ourstatus->kind == TARGET_WAITKIND_EXITED
1256 || ourstatus->kind == TARGET_WAITKIND_SIGNALLED)
1259 info = get_thread_db_info (GET_PID (ptid));
1261 /* If this process isn't using thread_db, we're done. */
1265 if (ourstatus->kind == TARGET_WAITKIND_EXECD)
1267 /* New image, it may or may not end up using thread_db. Assume
1268 not unless we find otherwise. */
1269 delete_thread_db_info (GET_PID (ptid));
1270 if (!thread_db_list)
1271 unpush_target (&thread_db_ops);
1273 /* Thread event breakpoints are deleted by
1274 update_breakpoints_after_exec. */
1279 /* If we do not know about the main thread yet, this would be a good time to
1281 if (ourstatus->kind == TARGET_WAITKIND_STOPPED && !have_threads (ptid))
1282 thread_db_find_new_threads_1 (ptid);
1284 if (ourstatus->kind == TARGET_WAITKIND_STOPPED
1285 && ourstatus->value.sig == TARGET_SIGNAL_TRAP)
1286 /* Check for a thread event. */
1289 if (have_threads (ptid))
1291 /* Change ptids back into the higher level PID + TID format. If
1292 the thread is dead and no longer on the thread list, we will
1293 get back a dead ptid. This can occur if the thread death
1294 event gets postponed by other simultaneous events. In such a
1295 case, we want to just ignore the event and continue on. */
1297 ptid = thread_from_lwp (ptid);
1298 if (GET_PID (ptid) == -1)
1299 ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
1306 thread_db_mourn_inferior (struct target_ops *ops)
1308 struct target_ops *target_beneath = find_target_beneath (ops);
1310 delete_thread_db_info (GET_PID (inferior_ptid));
1312 target_beneath->to_mourn_inferior (target_beneath);
1314 /* Delete the old thread event breakpoints. Do this after mourning
1315 the inferior, so that we don't try to uninsert them. */
1316 remove_thread_event_breakpoints ();
1318 /* Detach thread_db target ops. */
1319 if (!thread_db_list)
1320 unpush_target (ops);
1323 struct callback_data
1325 struct thread_db_info *info;
1330 find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
1335 struct thread_info *tp;
1336 struct callback_data *cb_data = data;
1337 struct thread_db_info *info = cb_data->info;
1339 err = info->td_thr_get_info_p (th_p, &ti);
1341 error (_("find_new_threads_callback: cannot get thread info: %s"),
1342 thread_db_err_str (err));
1344 if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE)
1345 return 0; /* A zombie -- ignore. */
1349 /* A thread ID of zero means that this is the main thread, but
1350 glibc has not yet initialized thread-local storage and the
1351 pthread library. We do not know what the thread's TID will
1352 be yet. Just enable event reporting and otherwise ignore
1355 /* In that case, we're not stopped in a fork syscall and don't
1356 need this glibc bug workaround. */
1357 info->need_stale_parent_threads_check = 0;
1359 if (target_has_execution)
1361 err = info->td_thr_event_enable_p (th_p, 1);
1363 error (_("Cannot enable thread event reporting for LWP %d: %s"),
1364 (int) ti.ti_lid, thread_db_err_str (err));
1370 /* Ignore stale parent threads, caused by glibc/BZ5983. This is a
1371 bit expensive, as it needs to open /proc/pid/status, so try to
1372 avoid doing the work if we know we don't have to. */
1373 if (info->need_stale_parent_threads_check)
1375 int tgid = linux_proc_get_tgid (ti.ti_lid);
1377 if (tgid != -1 && tgid != info->pid)
1381 ptid = ptid_build (info->pid, ti.ti_lid, 0);
1382 tp = find_thread_ptid (ptid);
1383 if (tp == NULL || tp->private == NULL)
1385 if (attach_thread (ptid, th_p, &ti))
1386 cb_data->new_threads += 1;
1388 /* Problem attaching this thread; perhaps it exited before we
1390 This could mean that the thread list inside glibc itself is in
1391 inconsistent state, and libthread_db could go on looping forever
1392 (observed with glibc-2.3.6). To prevent that, terminate
1393 iteration: thread_db_find_new_threads_2 will retry. */
1400 /* Helper for thread_db_find_new_threads_2.
1401 Returns number of new threads found. */
1404 find_new_threads_once (struct thread_db_info *info, int iteration,
1407 volatile struct gdb_exception except;
1408 struct callback_data data;
1409 td_err_e err = TD_ERR;
1412 data.new_threads = 0;
1414 TRY_CATCH (except, RETURN_MASK_ERROR)
1416 /* Iterate over all user-space threads to discover new threads. */
1417 err = info->td_ta_thr_iter_p (info->thread_agent,
1418 find_new_threads_callback,
1421 TD_THR_LOWEST_PRIORITY,
1423 TD_THR_ANY_USER_FLAGS);
1426 if (libthread_db_debug)
1428 if (except.reason < 0)
1429 exception_fprintf (gdb_stderr, except,
1430 "Warning: find_new_threads_once: ");
1432 printf_filtered (_("Found %d new threads in iteration %d.\n"),
1433 data.new_threads, iteration);
1439 return data.new_threads;
1442 /* Search for new threads, accessing memory through stopped thread
1443 PTID. If UNTIL_NO_NEW is true, repeat searching until several
1444 searches in a row do not discover any new threads. */
1447 thread_db_find_new_threads_2 (ptid_t ptid, int until_no_new)
1450 struct thread_db_info *info;
1451 int pid = ptid_get_pid (ptid);
1454 if (target_has_execution)
1456 struct lwp_info *lp;
1458 /* In linux, we can only read memory through a stopped lwp. */
1460 if (lp->stopped && ptid_get_pid (lp->ptid) == pid)
1464 /* There is no stopped thread. Bail out. */
1468 info = get_thread_db_info (GET_PID (ptid));
1470 /* Access an lwp we know is stopped. */
1471 info->proc_handle.ptid = ptid;
1475 /* Require 4 successive iterations which do not find any new threads.
1476 The 4 is a heuristic: there is an inherent race here, and I have
1477 seen that 2 iterations in a row are not always sufficient to
1478 "capture" all threads. */
1479 for (i = 0, loop = 0; loop < 4; ++i, ++loop)
1480 if (find_new_threads_once (info, i, NULL) != 0)
1481 /* Found some new threads. Restart the loop from beginning. */
1486 find_new_threads_once (info, 0, &err);
1488 error (_("Cannot find new threads: %s"), thread_db_err_str (err));
1493 thread_db_find_new_threads_1 (ptid_t ptid)
1495 thread_db_find_new_threads_2 (ptid, 0);
1499 update_thread_core (struct lwp_info *info, void *closure)
1501 info->core = linux_nat_core_of_thread_1 (info->ptid);
1506 thread_db_find_new_threads (struct target_ops *ops)
1508 struct thread_db_info *info;
1510 info = get_thread_db_info (GET_PID (inferior_ptid));
1515 thread_db_find_new_threads_1 (inferior_ptid);
1517 if (target_has_execution)
1518 iterate_over_lwps (minus_one_ptid /* iterate over all */,
1519 update_thread_core, NULL);
1523 thread_db_pid_to_str (struct target_ops *ops, ptid_t ptid)
1525 struct thread_info *thread_info = find_thread_ptid (ptid);
1526 struct target_ops *beneath;
1528 if (thread_info != NULL && thread_info->private != NULL)
1530 static char buf[64];
1533 tid = thread_info->private->tid;
1534 snprintf (buf, sizeof (buf), "Thread 0x%lx (LWP %ld)",
1535 tid, GET_LWP (ptid));
1540 beneath = find_target_beneath (ops);
1541 if (beneath->to_pid_to_str (beneath, ptid))
1542 return beneath->to_pid_to_str (beneath, ptid);
1544 return normal_pid_to_str (ptid);
1547 /* Return a string describing the state of the thread specified by
1551 thread_db_extra_thread_info (struct thread_info *info)
1553 if (info->private == NULL)
1556 if (info->private->dying)
1562 /* Get the address of the thread local variable in load module LM which
1563 is stored at OFFSET within the thread local storage for thread PTID. */
1566 thread_db_get_thread_local_address (struct target_ops *ops,
1571 struct thread_info *thread_info;
1572 struct target_ops *beneath;
1574 /* If we have not discovered any threads yet, check now. */
1575 if (!have_threads (ptid))
1576 thread_db_find_new_threads_1 (ptid);
1578 /* Find the matching thread. */
1579 thread_info = find_thread_ptid (ptid);
1581 if (thread_info != NULL && thread_info->private != NULL)
1585 struct thread_db_info *info;
1587 info = get_thread_db_info (GET_PID (ptid));
1589 /* glibc doesn't provide the needed interface. */
1590 if (!info->td_thr_tls_get_addr_p)
1591 throw_error (TLS_NO_LIBRARY_SUPPORT_ERROR,
1592 _("No TLS library support"));
1594 /* Caller should have verified that lm != 0. */
1595 gdb_assert (lm != 0);
1597 /* Finally, get the address of the variable. */
1598 /* Note the cast through uintptr_t: this interface only works if
1599 a target address fits in a psaddr_t, which is a host pointer.
1600 So a 32-bit debugger can not access 64-bit TLS through this. */
1601 err = info->td_thr_tls_get_addr_p (&thread_info->private->th,
1602 (psaddr_t)(uintptr_t) lm,
1605 #ifdef THREAD_DB_HAS_TD_NOTALLOC
1606 /* The memory hasn't been allocated, yet. */
1607 if (err == TD_NOTALLOC)
1608 /* Now, if libthread_db provided the initialization image's
1609 address, we *could* try to build a non-lvalue value from
1610 the initialization image. */
1611 throw_error (TLS_NOT_ALLOCATED_YET_ERROR,
1612 _("TLS not allocated yet"));
1615 /* Something else went wrong. */
1617 throw_error (TLS_GENERIC_ERROR,
1618 (("%s")), thread_db_err_str (err));
1620 /* Cast assuming host == target. Joy. */
1621 /* Do proper sign extension for the target. */
1622 gdb_assert (exec_bfd);
1623 return (bfd_get_sign_extend_vma (exec_bfd) > 0
1624 ? (CORE_ADDR) (intptr_t) address
1625 : (CORE_ADDR) (uintptr_t) address);
1628 beneath = find_target_beneath (ops);
1629 if (beneath->to_get_thread_local_address)
1630 return beneath->to_get_thread_local_address (beneath, ptid, lm, offset);
1632 throw_error (TLS_GENERIC_ERROR,
1633 _("TLS not supported on this target"));
1636 /* Callback routine used to find a thread based on the TID part of
1640 thread_db_find_thread_from_tid (struct thread_info *thread, void *data)
1642 long *tid = (long *) data;
1644 if (thread->private->tid == *tid)
1650 /* Implement the to_get_ada_task_ptid target method for this target. */
1653 thread_db_get_ada_task_ptid (long lwp, long thread)
1655 struct thread_info *thread_info;
1657 thread_db_find_new_threads_1 (inferior_ptid);
1658 thread_info = iterate_over_threads (thread_db_find_thread_from_tid, &thread);
1660 gdb_assert (thread_info != NULL);
1662 return (thread_info->ptid);
1666 thread_db_resume (struct target_ops *ops,
1667 ptid_t ptid, int step, enum target_signal signo)
1669 struct target_ops *beneath = find_target_beneath (ops);
1670 struct thread_db_info *info;
1672 if (ptid_equal (ptid, minus_one_ptid))
1673 info = get_thread_db_info (GET_PID (inferior_ptid));
1675 info = get_thread_db_info (GET_PID (ptid));
1677 /* This workaround is only needed for child fork lwps stopped in a
1678 PTRACE_O_TRACEFORK event. When the inferior is resumed, the
1679 workaround can be disabled. */
1681 info->need_stale_parent_threads_check = 0;
1683 beneath->to_resume (beneath, ptid, step, signo);
1687 init_thread_db_ops (void)
1689 thread_db_ops.to_shortname = "multi-thread";
1690 thread_db_ops.to_longname = "multi-threaded child process.";
1691 thread_db_ops.to_doc = "Threads and pthreads support.";
1692 thread_db_ops.to_detach = thread_db_detach;
1693 thread_db_ops.to_wait = thread_db_wait;
1694 thread_db_ops.to_resume = thread_db_resume;
1695 thread_db_ops.to_mourn_inferior = thread_db_mourn_inferior;
1696 thread_db_ops.to_find_new_threads = thread_db_find_new_threads;
1697 thread_db_ops.to_pid_to_str = thread_db_pid_to_str;
1698 thread_db_ops.to_stratum = thread_stratum;
1699 thread_db_ops.to_has_thread_control = tc_schedlock;
1700 thread_db_ops.to_get_thread_local_address
1701 = thread_db_get_thread_local_address;
1702 thread_db_ops.to_extra_thread_info = thread_db_extra_thread_info;
1703 thread_db_ops.to_get_ada_task_ptid = thread_db_get_ada_task_ptid;
1704 thread_db_ops.to_magic = OPS_MAGIC;
1707 /* Provide a prototype to silence -Wmissing-prototypes. */
1708 extern initialize_file_ftype _initialize_thread_db;
1711 _initialize_thread_db (void)
1713 init_thread_db_ops ();
1714 add_target (&thread_db_ops);
1716 /* Defer loading of libthread_db.so until inferior is running.
1717 This allows gdb to load correct libthread_db for a given
1718 executable -- there could be mutiple versions of glibc,
1719 compiled with LinuxThreads or NPTL, and until there is
1720 a running inferior, we can't tell which libthread_db is
1721 the correct one to load. */
1723 libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
1725 add_setshow_optional_filename_cmd ("libthread-db-search-path",
1727 &libthread_db_search_path, _("\
1728 Set search path for libthread_db."), _("\
1729 Show the current search path or libthread_db."), _("\
1730 This path is used to search for libthread_db to be loaded into \
1732 Its value is a colon (':') separate list of directories to search.\n\
1733 Setting the search path to an empty list resets it to its default value."),
1734 set_libthread_db_search_path,
1736 &setlist, &showlist);
1738 add_setshow_zinteger_cmd ("libthread-db", class_maintenance,
1739 &libthread_db_debug, _("\
1740 Set libthread-db debugging."), _("\
1741 Show libthread-db debugging."), _("\
1742 When non-zero, libthread-db debugging is enabled."),
1744 show_libthread_db_debug,
1745 &setdebuglist, &showdebuglist);
1747 /* Add ourselves to objfile event chain. */
1748 observer_attach_new_objfile (thread_db_new_objfile);