gdb/gdbserver/thread-db.c

/* Thread management interface, for the remote server for GDB.
   Copyright (C) 2002, 2004, 2005, 2006, 2007, 2008
   Free Software Foundation, Inc.

   Contributed by MontaVista Software.

   This file is part of GDB.

   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 "server.h"

#include "linux-low.h"

extern int debug_threads;

static int thread_db_use_events;

#ifdef HAVE_THREAD_DB_H
#include <thread_db.h>
#endif

#include "gdb_proc_service.h"

#include <stdint.h>

/* Structure that identifies the child process for the
   <proc_service.h> interface.  */
static struct ps_prochandle proc_handle;

/* Connection to the libthread_db library.  */
static td_thragent_t *thread_agent;

static int find_one_thread (int);
static int find_new_threads_callback (const td_thrhandle_t *th_p, void *data);

static char *
thread_db_err_str (td_err_e err)
{
  static char buf[64];

  switch (err)
    {
    case TD_OK:
      return "generic 'call succeeded'";
    case TD_ERR:
      return "generic error";
    case TD_NOTHR:
      return "no thread to satisfy query";
    case TD_NOSV:
      return "no sync handle to satisfy query";
    case TD_NOLWP:
      return "no LWP to satisfy query";
    case TD_BADPH:
      return "invalid process handle";
    case TD_BADTH:
      return "invalid thread handle";
    case TD_BADSH:
      return "invalid synchronization handle";
    case TD_BADTA:
      return "invalid thread agent";
    case TD_BADKEY:
      return "invalid key";
    case TD_NOMSG:
      return "no event message for getmsg";
    case TD_NOFPREGS:
      return "FPU register set not available";
    case TD_NOLIBTHREAD:
      return "application not linked with libthread";
    case TD_NOEVENT:
      return "requested event is not supported";
    case TD_NOCAPAB:
      return "capability not available";
    case TD_DBERR:
      return "debugger service failed";
    case TD_NOAPLIC:
      return "operation not applicable to";
    case TD_NOTSD:
      return "no thread-specific data for this thread";
    case TD_MALLOC:
      return "malloc failed";
    case TD_PARTIALREG:
      return "only part of register set was written/read";
    case TD_NOXREGS:
      return "X register set not available for this thread";
#ifdef HAVE_TD_VERSION
    case TD_VERSION:
      return "version mismatch between libthread_db and libpthread";
#endif
    default:
      snprintf (buf, sizeof (buf), "unknown thread_db error '%d'", err);
      return buf;
    }
}

#if 0
static char *
thread_db_state_str (td_thr_state_e state)
{
  static char buf[64];

  switch (state)
    {
    case TD_THR_STOPPED:
      return "stopped by debugger";
    case TD_THR_RUN:
      return "runnable";
    case TD_THR_ACTIVE:
      return "active";
    case TD_THR_ZOMBIE:
      return "zombie";
    case TD_THR_SLEEP:
      return "sleeping";
    case TD_THR_STOPPED_ASLEEP:
      return "stopped by debugger AND blocked";
    default:
      snprintf (buf, sizeof (buf), "unknown thread_db state %d", state);
      return buf;
    }
}
#endif

static int
thread_db_create_event (CORE_ADDR where)
{
  td_event_msg_t msg;
  td_err_e err;
  struct process_info *process;

  if (debug_threads)
    fprintf (stderr, "Thread creation event.\n");

  /* FIXME: This assumes we don't get another event.
     In the LinuxThreads implementation, this is safe,
     because all events come from the manager thread
     (except for its own creation, of course).  */
  err = td_ta_event_getmsg (thread_agent, &msg);
  if (err != TD_OK)
    fprintf (stderr, "thread getmsg err: %s\n",
	     thread_db_err_str (err));

  /* If we do not know about the main thread yet, this would be a good time to
     find it.  We need to do this to pick up the main thread before any newly
     created threads.  */
  process = get_thread_process (current_inferior);
  if (process->thread_known == 0)
    find_one_thread (process->lwpid);

  /* msg.event == TD_EVENT_CREATE */

  find_new_threads_callback (msg.th_p, NULL);

  return 0;
}

#if 0
static int
thread_db_death_event (CORE_ADDR where)
{
  if (debug_threads)
    fprintf (stderr, "Thread death event.\n");

  return 0;
}
#endif

static int
thread_db_enable_reporting ()
{
  td_thr_events_t events;
  td_notify_t notify;
  td_err_e err;

  /* Set the process wide mask saying which events we're interested in.  */
  td_event_emptyset (&events);
  td_event_addset (&events, TD_CREATE);

#if 0
  /* This is reported to be broken in glibc 2.1.3.  A different approach
     will be necessary to support that.  */
  td_event_addset (&events, TD_DEATH);
#endif

  err = td_ta_set_event (thread_agent, &events);
  if (err != TD_OK)
    {
      warning ("Unable to set global thread event mask: %s",
               thread_db_err_str (err));
      return 0;
    }

  /* Get address for thread creation breakpoint.  */
  err = td_ta_event_addr (thread_agent, TD_CREATE, &notify);
  if (err != TD_OK)
    {
      warning ("Unable to get location for thread creation breakpoint: %s",
	       thread_db_err_str (err));
      return 0;
    }
  set_breakpoint_at ((CORE_ADDR) (unsigned long) notify.u.bptaddr,
		     thread_db_create_event);

#if 0
  /* Don't concern ourselves with reported thread deaths, only
     with actual thread deaths (via wait).  */

  /* Get address for thread death breakpoint.  */
  err = td_ta_event_addr (thread_agent, TD_DEATH, &notify);
  if (err != TD_OK)
    {
      warning ("Unable to get location for thread death breakpoint: %s",
	       thread_db_err_str (err));
      return;
    }
  set_breakpoint_at ((CORE_ADDR) (unsigned long) notify.u.bptaddr,
		     thread_db_death_event);
#endif

  return 1;
}

static int
find_one_thread (int lwpid)
{
  td_thrhandle_t th;
  td_thrinfo_t ti;
  td_err_e err;
  struct thread_info *inferior;
  struct process_info *process;

  inferior = (struct thread_info *) find_inferior_id (&all_threads, lwpid);
  process = get_thread_process (inferior);
  if (process->thread_known)
    return 1;

  /* Get information about this thread.  */
  err = td_ta_map_lwp2thr (thread_agent, process->lwpid, &th);
  if (err != TD_OK)
    error ("Cannot get thread handle for LWP %d: %s",
	   lwpid, thread_db_err_str (err));

  err = td_thr_get_info (&th, &ti);
  if (err != TD_OK)
    error ("Cannot get thread info for LWP %d: %s",
	   lwpid, thread_db_err_str (err));

  if (debug_threads)
    fprintf (stderr, "Found thread %ld (LWP %d)\n",
	     ti.ti_tid, ti.ti_lid);

  if (process->lwpid != ti.ti_lid)
    {
      warning ("PID mismatch!  Expected %ld, got %ld",
	       (long) process->lwpid, (long) ti.ti_lid);
      return 0;
    }

  if (thread_db_use_events)
    {
      err = td_thr_event_enable (&th, 1);
      if (err != TD_OK)
	error ("Cannot enable thread event reporting for %d: %s",
	       ti.ti_lid, thread_db_err_str (err));
    }

  /* If the new thread ID is zero, a final thread ID will be available
     later.  Do not enable thread debugging yet.  */
  if (ti.ti_tid == 0)
    return 0;

  process->thread_known = 1;
  process->th = th;

  return 1;
}

static void
maybe_attach_thread (const td_thrhandle_t *th_p, td_thrinfo_t *ti_p)
{
  td_err_e err;
  struct thread_info *inferior;
  struct process_info *process;

  inferior = (struct thread_info *) find_inferior_id (&all_threads,
						      ti_p->ti_lid);
  if (inferior != NULL)
    return;

  if (debug_threads)
    fprintf (stderr, "Attaching to thread %ld (LWP %d)\n",
	     ti_p->ti_tid, ti_p->ti_lid);
  linux_attach_lwp (ti_p->ti_lid);
  inferior = (struct thread_info *) find_inferior_id (&all_threads,
						      ti_p->ti_lid);
  if (inferior == NULL)
    {
      warning ("Could not attach to thread %ld (LWP %d)\n",
	       ti_p->ti_tid, ti_p->ti_lid);
      return;
    }

  process = inferior_target_data (inferior);

  process->thread_known = 1;
  process->th = *th_p;

  if (thread_db_use_events)
    {
      err = td_thr_event_enable (th_p, 1);
      if (err != TD_OK)
	error ("Cannot enable thread event reporting for %d: %s",
	       ti_p->ti_lid, thread_db_err_str (err));
    }
}

static int
find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
{
  td_thrinfo_t ti;
  td_err_e err;

  err = td_thr_get_info (th_p, &ti);
  if (err != TD_OK)
    error ("Cannot get thread info: %s", thread_db_err_str (err));

  /* Check for zombies.  */
  if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE)
    return 0;

  maybe_attach_thread (th_p, &ti);

  return 0;
}

static void
thread_db_find_new_threads (void)
{
  td_err_e err;

  /* This function is only called when we first initialize thread_db.
     First locate the initial thread.  If it is not ready for
     debugging yet, then stop.  */
  if (find_one_thread (all_threads.head->id) == 0)
    return;

  /* Iterate over all user-space threads to discover new threads.  */
  err = td_ta_thr_iter (thread_agent, find_new_threads_callback, NULL,
			TD_THR_ANY_STATE, TD_THR_LOWEST_PRIORITY,
			TD_SIGNO_MASK, TD_THR_ANY_USER_FLAGS);
  if (err != TD_OK)
    error ("Cannot find new threads: %s", thread_db_err_str (err));
}

/* Cache all future symbols that thread_db might request.  We can not
   request symbols at arbitrary states in the remote protocol, only
   when the client tells us that new symbols are available.  So when
   we load the thread library, make sure to check the entire list.  */

static void
thread_db_look_up_symbols (void)
{
  const char **sym_list = td_symbol_list ();
  CORE_ADDR unused;

  for (sym_list = td_symbol_list (); *sym_list; sym_list++)
    look_up_one_symbol (*sym_list, &unused);
}

int
thread_db_get_tls_address (struct thread_info *thread, CORE_ADDR offset,
			   CORE_ADDR load_module, CORE_ADDR *address)
{
#if HAVE_TD_THR_TLS_GET_ADDR
  psaddr_t addr;
  td_err_e err;
  struct process_info *process;

  process = get_thread_process (thread);
  if (!process->thread_known)
    find_one_thread (process->lwpid);
  if (!process->thread_known)
    return TD_NOTHR;

  /* Note the cast through uintptr_t: this interface only works if
     a target address fits in a psaddr_t, which is a host pointer.
     So a 32-bit debugger can not access 64-bit TLS through this.  */
  err = td_thr_tls_get_addr (&process->th, (psaddr_t) (uintptr_t) load_module,
			     offset, &addr);
  if (err == TD_OK)
    {
      *address = (CORE_ADDR) (uintptr_t) addr;
      return 0;
    }
  else
    return err;
#else
  return -1;
#endif
}

int
thread_db_init (int use_events)
{
  int err;

  /* FIXME drow/2004-10-16: This is the "overall process ID", which
     GNU/Linux calls tgid, "thread group ID".  When we support
     attaching to threads, the original thread may not be the correct
     thread.  We would have to get the process ID from /proc for NPTL.
     For LinuxThreads we could do something similar: follow the chain
     of parent processes until we find the highest one we're attached
     to, and use its tgid.

     This isn't the only place in gdbserver that assumes that the first
     process in the list is the thread group leader.  */
  proc_handle.pid = ((struct inferior_list_entry *)current_inferior)->id;

  /* Allow new symbol lookups.  */
  all_symbols_looked_up = 0;

  thread_db_use_events = use_events;

  err = td_ta_new (&proc_handle, &thread_agent);
  switch (err)
    {
    case TD_NOLIBTHREAD:
      /* No thread library was detected.  */
      return 0;

    case TD_OK:
      /* The thread library was detected.  */

      if (use_events && thread_db_enable_reporting () == 0)
	return 0;
      thread_db_find_new_threads ();
      thread_db_look_up_symbols ();
      all_symbols_looked_up = 1;
      return 1;

    default:
      warning ("error initializing thread_db library: %s",
	       thread_db_err_str (err));
    }

  return 0;
}