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8784d56326e72e2e6863e8443b1f97e45a46ba36
binutils-gdb/gdb/gdbserver/thread-db.c
Pedro Alves 8784d56326 Linux: on attach, attach to lwps listed under /proc/$pid/task/ 
... instead of relying on libthread_db.

I wrote a test that attaches to a program that constantly spawns
short-lived threads, which exposed several issues.  This is one of
them.

On Linux, we need to attach to all threads of a process (thread group)
individually.  We currently rely on libthread_db to list the threads,
but that is problematic, because libthread_db relies on reading data
structures out of the inferior (which may well be corrupted).  If
threads are being created or exiting just while we try to attach, we
may trip on inconsistencies in the inferior's thread list.  To work
around that, when we see a seemingly corrupt list, we currently retry
a few times:

 static void
 thread_db_find_new_threads_2 (ptid_t ptid, int until_no_new)
 {
 ...
   if (until_no_new)
     {
       /* Require 4 successive iterations which do not find any new threads.
	  The 4 is a heuristic: there is an inherent race here, and I have
	  seen that 2 iterations in a row are not always sufficient to
	  "capture" all threads.  */
 ...

That heuristic may well fail, and when it does, we end up with threads
in the program that aren't under GDB's control.  That's obviously bad
and results in quite mistifying failures, like e.g., the process dying
for seeminly no reason when a thread that wasn't attached trips on a
breakpoint.

There's really no reason to rely on libthread_db for this nowadays
when we have /proc mounted.  In that case, which is the usual case, we
can list the LWPs from /proc/PID/task/.  In fact, GDBserver is already
doing this.  The patch factors out that code that knows to walk the
task/ directory out of GDBserver, and makes GDB use it too.

Like GDBserver, the patch makes GDB attach to LWPs and _not_ wait for
them to stop immediately.  Instead, we just tag the LWP as having an
expected stop.  Because we can only set the ptrace options when the
thread stops, we need a new flag in the lwp structure to keep track of
whether we've already set the ptrace options, just like in GDBserver.
Note that nothing issues any ptrace command to the threads between the
PTRACE_ATTACH and the stop, so this is safe (unlike one scenario
described in gdbserver's linux-low.c).

When we attach to a program that has threads exiting while we attach,
it's easy to race with a thread just exiting as we try to attach to
it, like:

  #1 - get current list of threads
  #2 - attach to each listed thread
  #3 - ooops, attach failed, thread is already gone

As this is pretty normal, we shouldn't be issuing a scary warning in
step #3.

When #3 happens, PTRACE_ATTACH usually fails with ESRCH, but sometimes
we'll see EPERM as well.  That happens when the kernel still has the
thread in its task list, but the thread is marked as dead.
Unfortunately, EPERM is ambiguous and we'll get it also on other
scenarios where the thread isn't dead, and in those cases, it's useful
to get a warning.  To distiguish the cases, when we get an EPERM
failure, we open /proc/PID/status, and check the thread's state -- if
the /proc file no longer exists, or the state is "Z (Zombie)" or "X
(Dead)", we ignore the EPERM error silently; otherwise, we'll warn.
Unfortunately, there seems to be a kernel race here.  Sometimes I get
EPERM, and then the /proc state still indicates "R (Running)"...  If
we wait a bit and retry, we do end up seeing X or Z state, or get an
ESRCH.  I thought of making GDB retry the attach a few times, but even
with a 500ms wait and 4 retries, I still see the warning sometimes.  I
haven't been able to identify the kernel path that causes this yet,
but in any case, it looks like a kernel bug to me.  As this just
results failure to suppress a warning that we've been printing since
about forever anyway, I'm just making the test cope with it, and issue
an XFAIL.

gdb/gdbserver/
2015-01-09  Pedro Alves  <palves@redhat.com>

	* linux-low.c (linux_attach_fail_reason_string): Move to
	nat/linux-ptrace.c, and rename.
	(linux_attach_lwp): Update comment.
	(attach_proc_task_lwp_callback): New function.
	(linux_attach): Adjust to rename and use
	linux_proc_attach_tgid_threads.
	(linux_attach_fail_reason_string): Delete declaration.

gdb/
2015-01-09  Pedro Alves  <palves@redhat.com>

	* linux-nat.c (attach_proc_task_lwp_callback): New function.
	(linux_nat_attach): Use linux_proc_attach_tgid_threads.
	(wait_lwp, linux_nat_filter_event): If not set yet, set the lwp's
	ptrace option flags.
	* linux-nat.h (struct lwp_info) <must_set_ptrace_flags>: New
	field.
	* nat/linux-procfs.c: Include <dirent.h>.
	(linux_proc_get_int): New parameter "warn".  Handle it.
	(linux_proc_get_tgid): Adjust.
	(linux_proc_get_tracerpid): Rename to ...
	(linux_proc_get_tracerpid_nowarn): ... this.
	(linux_proc_pid_get_state): New function, factored out from
	(linux_proc_pid_has_state): ... this.  Add new parameter "warn"
	and handle it.
	(linux_proc_pid_is_gone): New function.
	(linux_proc_pid_is_stopped): Adjust.
	(linux_proc_pid_is_zombie_maybe_warn)
	(linux_proc_pid_is_zombie_nowarn): New functions.
	(linux_proc_pid_is_zombie): Use
	linux_proc_pid_is_zombie_maybe_warn.
	(linux_proc_attach_tgid_threads): New function.
	* nat/linux-procfs.h (linux_proc_get_tgid): Update comment.
	(linux_proc_get_tracerpid): Rename to ...
	(linux_proc_get_tracerpid_nowarn): ... this, and update comment.
	(linux_proc_pid_is_gone): New declaration.
	(linux_proc_pid_is_zombie): Update comment.
	(linux_proc_pid_is_zombie_nowarn): New declaration.
	(linux_proc_attach_lwp_func): New typedef.
	(linux_proc_attach_tgid_threads): New declaration.
	* nat/linux-ptrace.c (linux_ptrace_attach_fail_reason): Adjust to
	use nowarn functions.
	(linux_ptrace_attach_fail_reason_string): Move here from
	gdbserver/linux-low.c and rename.
	(ptrace_supports_feature): If the current ptrace options are not
	known yet, check them now, instead of asserting.
	* nat/linux-ptrace.h (linux_ptrace_attach_fail_reason_string):
	Declare.
2015-01-09 11:39:49 +00:00

1004 lines
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/* Thread management interface, for the remote server for GDB.
Copyright (C) 2002-2015 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;
#include "gdb_proc_service.h"
#include "nat/gdb_thread_db.h"
#include "gdb_vecs.h"
#ifndef USE_LIBTHREAD_DB_DIRECTLY
#include <dlfcn.h>
#endif
#include <stdint.h>
#include <limits.h>
#include <ctype.h>
struct thread_db
{
/* Structure that identifies the child process for the
<proc_service.h> interface. */
struct ps_prochandle proc_handle;
/* Connection to the libthread_db library. */
td_thragent_t *thread_agent;
/* If this flag has been set, we've already asked GDB for all
symbols we might need; assume symbol cache misses are
failures. */
int all_symbols_looked_up;
#ifndef USE_LIBTHREAD_DB_DIRECTLY
/* Handle of the libthread_db from dlopen. */
void *handle;
#endif
/* Thread creation event breakpoint. The code at this location in
the child process will be called by the pthread library whenever
a new thread is created. By setting a special breakpoint at this
location, GDB can detect when a new thread is created. We obtain
this location via the td_ta_event_addr call. Note that if the
running kernel supports tracing clones, then we don't need to use
(and in fact don't use) this magic thread event breakpoint to
learn about threads. */
struct breakpoint *td_create_bp;
/* Addresses of libthread_db functions. */
td_err_e (*td_ta_new_p) (struct ps_prochandle * ps, td_thragent_t **ta);
td_err_e (*td_ta_event_getmsg_p) (const td_thragent_t *ta,
td_event_msg_t *msg);
td_err_e (*td_ta_set_event_p) (const td_thragent_t *ta,
td_thr_events_t *event);
td_err_e (*td_ta_event_addr_p) (const td_thragent_t *ta,
td_event_e event, td_notify_t *ptr);
td_err_e (*td_ta_map_lwp2thr_p) (const td_thragent_t *ta, lwpid_t lwpid,
td_thrhandle_t *th);
td_err_e (*td_thr_get_info_p) (const td_thrhandle_t *th,
td_thrinfo_t *infop);
td_err_e (*td_thr_event_enable_p) (const td_thrhandle_t *th, int event);
td_err_e (*td_ta_thr_iter_p) (const td_thragent_t *ta,
td_thr_iter_f *callback, void *cbdata_p,
td_thr_state_e state, int ti_pri,
sigset_t *ti_sigmask_p,
unsigned int ti_user_flags);
td_err_e (*td_thr_tls_get_addr_p) (const td_thrhandle_t *th,
psaddr_t map_address,
size_t offset, psaddr_t *address);
td_err_e (*td_thr_tlsbase_p) (const td_thrhandle_t *th,
unsigned long int modid,
psaddr_t *base);
const char ** (*td_symbol_list_p) (void);
};
static char *libthread_db_search_path;
static int find_one_thread (ptid_t);
static int find_new_threads_callback (const td_thrhandle_t *th_p, void *data);
static const 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:
xsnprintf (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:
xsnprintf (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 lwp_info *lwp;
struct thread_db *thread_db = current_process ()->private->thread_db;
gdb_assert (thread_db->td_ta_event_getmsg_p != NULL);
if (debug_threads)
debug_printf ("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 = thread_db->td_ta_event_getmsg_p (thread_db->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. */
lwp = get_thread_lwp (current_thread);
if (lwp->thread_known == 0)
find_one_thread (current_thread->entry.id);
/* msg.event == TD_EVENT_CREATE */
find_new_threads_callback (msg.th_p, NULL);
return 0;
}
static int
thread_db_enable_reporting (void)
{
td_thr_events_t events;
td_notify_t notify;
td_err_e err;
struct thread_db *thread_db = current_process ()->private->thread_db;
if (thread_db->td_ta_set_event_p == NULL
|| thread_db->td_ta_event_addr_p == NULL
|| thread_db->td_ta_event_getmsg_p == NULL)
/* This libthread_db is missing required support. */
return 0;
/* Set the process wide mask saying which events we're interested in. */
td_event_emptyset (&events);
td_event_addset (&events, TD_CREATE);
err = thread_db->td_ta_set_event_p (thread_db->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 = thread_db->td_ta_event_addr_p (thread_db->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;
}
thread_db->td_create_bp
= set_breakpoint_at ((CORE_ADDR) (unsigned long) notify.u.bptaddr,
thread_db_create_event);
return 1;
}
static int
find_one_thread (ptid_t ptid)
{
td_thrhandle_t th;
td_thrinfo_t ti;
td_err_e err;
struct thread_info *inferior;
struct lwp_info *lwp;
struct thread_db *thread_db = current_process ()->private->thread_db;
int lwpid = ptid_get_lwp (ptid);
inferior = (struct thread_info *) find_inferior_id (&all_threads, ptid);
lwp = get_thread_lwp (inferior);
if (lwp->thread_known)
return 1;
/* Get information about this thread. */
err = thread_db->td_ta_map_lwp2thr_p (thread_db->thread_agent, lwpid, &th);
if (err != TD_OK)
error ("Cannot get thread handle for LWP %d: %s",
lwpid, thread_db_err_str (err));
err = thread_db->td_thr_get_info_p (&th, &ti);
if (err != TD_OK)
error ("Cannot get thread info for LWP %d: %s",
lwpid, thread_db_err_str (err));
if (debug_threads)
debug_printf ("Found thread %ld (LWP %d)\n",
ti.ti_tid, ti.ti_lid);
if (lwpid != ti.ti_lid)
{
warning ("PID mismatch! Expected %ld, got %ld",
(long) lwpid, (long) ti.ti_lid);
return 0;
}
if (thread_db_use_events)
{
err = thread_db->td_thr_event_enable_p (&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;
lwp->thread_known = 1;
lwp->th = th;
return 1;
}
/* Attach a thread. Return true on success. */
static int
attach_thread (const td_thrhandle_t *th_p, td_thrinfo_t *ti_p)
{
struct process_info *proc = current_process ();
int pid = pid_of (proc);
ptid_t ptid = ptid_build (pid, ti_p->ti_lid, 0);
struct lwp_info *lwp;
int err;
if (debug_threads)
debug_printf ("Attaching to thread %ld (LWP %d)\n",
ti_p->ti_tid, ti_p->ti_lid);
err = linux_attach_lwp (ptid);
if (err != 0)
{
warning ("Could not attach to thread %ld (LWP %d): %s\n",
ti_p->ti_tid, ti_p->ti_lid,
linux_ptrace_attach_fail_reason_string (ptid, err));
return 0;
}
lwp = find_lwp_pid (ptid);
gdb_assert (lwp != NULL);
lwp->thread_known = 1;
lwp->th = *th_p;
if (thread_db_use_events)
{
td_err_e err;
struct thread_db *thread_db = proc->private->thread_db;
err = thread_db->td_thr_event_enable_p (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));
}
return 1;
}
/* Attach thread if we haven't seen it yet.
Increment *COUNTER if we have attached a new thread.
Return false on failure. */
static int
maybe_attach_thread (const td_thrhandle_t *th_p, td_thrinfo_t *ti_p,
int *counter)
{
struct lwp_info *lwp;
lwp = find_lwp_pid (pid_to_ptid (ti_p->ti_lid));
if (lwp != NULL)
return 1;
if (!attach_thread (th_p, ti_p))
return 0;
if (counter != NULL)
*counter += 1;
return 1;
}
static int
find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
{
td_thrinfo_t ti;
td_err_e err;
struct thread_db *thread_db = current_process ()->private->thread_db;
err = thread_db->td_thr_get_info_p (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;
if (!maybe_attach_thread (th_p, &ti, (int *) data))
{
/* Terminate iteration early: we might be looking at stale data in
the inferior. The thread_db_find_new_threads will retry. */
return 1;
}
return 0;
}
static void
thread_db_find_new_threads (void)
{
td_err_e err;
ptid_t ptid = current_ptid;
struct thread_db *thread_db = current_process ()->private->thread_db;
int loop, iteration;
/* 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 (ptid) == 0)
return;
/* Require 4 successive iterations which do not find any new threads.
The 4 is a heuristic: there is an inherent race here, and I have
seen that 2 iterations in a row are not always sufficient to
"capture" all threads. */
for (loop = 0, iteration = 0; loop < 4; ++loop, ++iteration)
{
int new_thread_count = 0;
/* Iterate over all user-space threads to discover new threads. */
err = thread_db->td_ta_thr_iter_p (thread_db->thread_agent,
find_new_threads_callback,
&new_thread_count,
TD_THR_ANY_STATE,
TD_THR_LOWEST_PRIORITY,
TD_SIGNO_MASK, TD_THR_ANY_USER_FLAGS);
if (debug_threads)
debug_printf ("Found %d threads in iteration %d.\n",
new_thread_count, iteration);
if (new_thread_count != 0)
{
/* Found new threads. Restart iteration from beginning. */
loop = -1;
}
}
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)
{
struct thread_db *thread_db = current_process ()->private->thread_db;
const char **sym_list;
CORE_ADDR unused;
for (sym_list = thread_db->td_symbol_list_p (); *sym_list; sym_list++)
look_up_one_symbol (*sym_list, &unused, 1);
/* We're not interested in any other libraries loaded after this
point, only in symbols in libpthread.so. */
thread_db->all_symbols_looked_up = 1;
}
int
thread_db_look_up_one_symbol (const char *name, CORE_ADDR *addrp)
{
struct thread_db *thread_db = current_process ()->private->thread_db;
int may_ask_gdb = !thread_db->all_symbols_looked_up;
/* If we've passed the call to thread_db_look_up_symbols, then
anything not in the cache must not exist; we're not interested
in any libraries loaded after that point, only in symbols in
libpthread.so. It might not be an appropriate time to look
up a symbol, e.g. while we're trying to fetch registers. */
return look_up_one_symbol (name, addrp, may_ask_gdb);
}
int
thread_db_get_tls_address (struct thread_info *thread, CORE_ADDR offset,
CORE_ADDR load_module, CORE_ADDR *address)
{
psaddr_t addr;
td_err_e err;
struct lwp_info *lwp;
struct thread_info *saved_thread;
struct process_info *proc;
struct thread_db *thread_db;
proc = get_thread_process (thread);
thread_db = proc->private->thread_db;
/* If the thread layer is not (yet) initialized, fail. */
if (thread_db == NULL || !thread_db->all_symbols_looked_up)
return TD_ERR;
/* If td_thr_tls_get_addr is missing rather do not expect td_thr_tlsbase
could work. */
if (thread_db->td_thr_tls_get_addr_p == NULL
|| (load_module == 0 && thread_db->td_thr_tlsbase_p == NULL))
return -1;
lwp = get_thread_lwp (thread);
if (!lwp->thread_known)
find_one_thread (thread->entry.id);
if (!lwp->thread_known)
return TD_NOTHR;
saved_thread = current_thread;
current_thread = thread;
if (load_module != 0)
{
/* 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 = thread_db->td_thr_tls_get_addr_p (&lwp->th,
(psaddr_t) (uintptr_t) load_module,
offset, &addr);
}
else
{
/* This code path handles the case of -static -pthread executables:
https://sourceware.org/ml/libc-help/2014-03/msg00024.html
For older GNU libc r_debug.r_map is NULL. For GNU libc after
PR libc/16831 due to GDB PR threads/16954 LOAD_MODULE is also NULL.
The constant number 1 depends on GNU __libc_setup_tls
initialization of l_tls_modid to 1. */
err = thread_db->td_thr_tlsbase_p (&lwp->th, 1, &addr);
addr = (char *) addr + offset;
}
current_thread = saved_thread;
if (err == TD_OK)
{
*address = (CORE_ADDR) (uintptr_t) addr;
return 0;
}
else
return err;
}
#ifdef USE_LIBTHREAD_DB_DIRECTLY
static int
thread_db_load_search (void)
{
td_err_e err;
struct thread_db *tdb;
struct process_info *proc = current_process ();
gdb_assert (proc->private->thread_db == NULL);
tdb = xcalloc (1, sizeof (*tdb));
proc->private->thread_db = tdb;
tdb->td_ta_new_p = &td_ta_new;
/* Attempt to open a connection to the thread library. */
err = tdb->td_ta_new_p (&tdb->proc_handle, &tdb->thread_agent);
if (err != TD_OK)
{
if (debug_threads)
debug_printf ("td_ta_new(): %s\n", thread_db_err_str (err));
free (tdb);
proc->private->thread_db = NULL;
return 0;
}
tdb->td_ta_map_lwp2thr_p = &td_ta_map_lwp2thr;
tdb->td_thr_get_info_p = &td_thr_get_info;
tdb->td_ta_thr_iter_p = &td_ta_thr_iter;
tdb->td_symbol_list_p = &td_symbol_list;
/* This is required only when thread_db_use_events is on. */
tdb->td_thr_event_enable_p = &td_thr_event_enable;
/* These are not essential. */
tdb->td_ta_event_addr_p = &td_ta_event_addr;
tdb->td_ta_set_event_p = &td_ta_set_event;
tdb->td_ta_event_getmsg_p = &td_ta_event_getmsg;
tdb->td_thr_tls_get_addr_p = &td_thr_tls_get_addr;
tdb->td_thr_tlsbase_p = &td_thr_tlsbase;
return 1;
}
#else
static int
try_thread_db_load_1 (void *handle)
{
td_err_e err;
struct thread_db *tdb;
struct process_info *proc = current_process ();
gdb_assert (proc->private->thread_db == NULL);
tdb = xcalloc (1, sizeof (*tdb));
proc->private->thread_db = tdb;
tdb->handle = handle;
/* Initialize pointers to the dynamic library functions we will use.
Essential functions first. */
#define CHK(required, a) \
do \
{ \
if ((a) == NULL) \
{ \
if (debug_threads) \
debug_printf ("dlsym: %s\n", dlerror ()); \
if (required) \
{ \
free (tdb); \
proc->private->thread_db = NULL; \
return 0; \
} \
} \
} \
while (0)
CHK (1, tdb->td_ta_new_p = dlsym (handle, "td_ta_new"));
/* Attempt to open a connection to the thread library. */
err = tdb->td_ta_new_p (&tdb->proc_handle, &tdb->thread_agent);
if (err != TD_OK)
{
if (debug_threads)
debug_printf ("td_ta_new(): %s\n", thread_db_err_str (err));
free (tdb);
proc->private->thread_db = NULL;
return 0;
}
CHK (1, tdb->td_ta_map_lwp2thr_p = dlsym (handle, "td_ta_map_lwp2thr"));
CHK (1, tdb->td_thr_get_info_p = dlsym (handle, "td_thr_get_info"));
CHK (1, tdb->td_ta_thr_iter_p = dlsym (handle, "td_ta_thr_iter"));
CHK (1, tdb->td_symbol_list_p = dlsym (handle, "td_symbol_list"));
/* This is required only when thread_db_use_events is on. */
CHK (thread_db_use_events,
tdb->td_thr_event_enable_p = dlsym (handle, "td_thr_event_enable"));
/* These are not essential. */
CHK (0, tdb->td_ta_event_addr_p = dlsym (handle, "td_ta_event_addr"));
CHK (0, tdb->td_ta_set_event_p = dlsym (handle, "td_ta_set_event"));
CHK (0, tdb->td_ta_event_getmsg_p = dlsym (handle, "td_ta_event_getmsg"));
CHK (0, tdb->td_thr_tls_get_addr_p = dlsym (handle, "td_thr_tls_get_addr"));
CHK (0, tdb->td_thr_tlsbase_p = dlsym (handle, "td_thr_tlsbase"));
#undef CHK
return 1;
}
#ifdef HAVE_DLADDR
/* Lookup a library in which given symbol resides.
Note: this is looking in the GDBSERVER process, not in the inferior.
Returns library name, or NULL. */
static const char *
dladdr_to_soname (const void *addr)
{
Dl_info info;
if (dladdr (addr, &info) != 0)
return info.dli_fname;
return NULL;
}
#endif
static int
try_thread_db_load (const char *library)
{
void *handle;
if (debug_threads)
debug_printf ("Trying host libthread_db library: %s.\n",
library);
handle = dlopen (library, RTLD_NOW);
if (handle == NULL)
{
if (debug_threads)
debug_printf ("dlopen failed: %s.\n", dlerror ());
return 0;
}
#ifdef HAVE_DLADDR
if (debug_threads && strchr (library, '/') == NULL)
{
void *td_init;
td_init = dlsym (handle, "td_init");
if (td_init != NULL)
{
const char *const libpath = dladdr_to_soname (td_init);
if (libpath != NULL)
fprintf (stderr, "Host %s resolved to: %s.\n",
library, libpath);
}
}
#endif
if (try_thread_db_load_1 (handle))
return 1;
/* This library "refused" to work on current inferior. */
dlclose (handle);
return 0;
}
/* Handle $sdir in libthread-db-search-path.
Look for libthread_db in the system dirs, or wherever a plain
dlopen(file_without_path) will look.
The result is true for success. */
static int
try_thread_db_load_from_sdir (void)
{
return try_thread_db_load (LIBTHREAD_DB_SO);
}
/* Try to load libthread_db from directory DIR of length DIR_LEN.
The result is true for success. */
static int
try_thread_db_load_from_dir (const char *dir, size_t dir_len)
{
char path[PATH_MAX];
if (dir_len + 1 + strlen (LIBTHREAD_DB_SO) + 1 > sizeof (path))
{
char *cp = xmalloc (dir_len + 1);
memcpy (cp, dir, dir_len);
cp[dir_len] = '\0';
warning (_("libthread-db-search-path component too long,"
" ignored: %s."), cp);
free (cp);
return 0;
}
memcpy (path, dir, dir_len);
path[dir_len] = '/';
strcpy (path + dir_len + 1, LIBTHREAD_DB_SO);
return try_thread_db_load (path);
}
/* Search libthread_db_search_path for libthread_db which "agrees"
to work on current inferior.
The result is true for success. */
static int
thread_db_load_search (void)
{
VEC (char_ptr) *dir_vec;
char *this_dir;
int i, rc = 0;
if (libthread_db_search_path == NULL)
libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
dir_vec = dirnames_to_char_ptr_vec (libthread_db_search_path);
for (i = 0; VEC_iterate (char_ptr, dir_vec, i, this_dir); ++i)
{
const int pdir_len = sizeof ("$pdir") - 1;
size_t this_dir_len;
this_dir_len = strlen (this_dir);
if (strncmp (this_dir, "$pdir", pdir_len) == 0
&& (this_dir[pdir_len] == '\0'
|| this_dir[pdir_len] == '/'))
{
/* We don't maintain a list of loaded libraries so we don't know
where libpthread lives. We *could* fetch the info, but we don't
do that yet. Ignore it. */
}
else if (strcmp (this_dir, "$sdir") == 0)
{
if (try_thread_db_load_from_sdir ())
{
rc = 1;
break;
}
}
else
{
if (try_thread_db_load_from_dir (this_dir, this_dir_len))
{
rc = 1;
break;
}
}
}
free_char_ptr_vec (dir_vec);
if (debug_threads)
debug_printf ("thread_db_load_search returning %d\n", rc);
return rc;
}
#endif /* USE_LIBTHREAD_DB_DIRECTLY */
int
thread_db_init (int use_events)
{
struct process_info *proc = current_process ();
/* 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. */
thread_db_use_events = use_events;
if (thread_db_load_search ())
{
if (use_events && thread_db_enable_reporting () == 0)
{
/* Keep trying; maybe event reporting will work later. */
thread_db_mourn (proc);
return 0;
}
thread_db_find_new_threads ();
thread_db_look_up_symbols ();
return 1;
}
return 0;
}
static int
any_thread_of (struct inferior_list_entry *entry, void *args)
{
int *pid_p = args;
if (ptid_get_pid (entry->id) == *pid_p)
return 1;
return 0;
}
static void
switch_to_process (struct process_info *proc)
{
int pid = pid_of (proc);
current_thread =
(struct thread_info *) find_inferior (&all_threads,
any_thread_of, &pid);
}
/* Disconnect from libthread_db and free resources. */
static void
disable_thread_event_reporting (struct process_info *proc)
{
struct thread_db *thread_db = proc->private->thread_db;
if (thread_db)
{
td_err_e (*td_ta_clear_event_p) (const td_thragent_t *ta,
td_thr_events_t *event);
#ifndef USE_LIBTHREAD_DB_DIRECTLY
td_ta_clear_event_p = dlsym (thread_db->handle, "td_ta_clear_event");
#else
td_ta_clear_event_p = &td_ta_clear_event;
#endif
if (td_ta_clear_event_p != NULL)
{
struct thread_info *saved_thread = current_thread;
td_thr_events_t events;
switch_to_process (proc);
/* Set the process wide mask saying we aren't interested
in any events anymore. */
td_event_fillset (&events);
(*td_ta_clear_event_p) (thread_db->thread_agent, &events);
current_thread = saved_thread;
}
}
}
static void
remove_thread_event_breakpoints (struct process_info *proc)
{
struct thread_db *thread_db = proc->private->thread_db;
if (thread_db->td_create_bp != NULL)
{
struct thread_info *saved_thread = current_thread;
switch_to_process (proc);
delete_breakpoint (thread_db->td_create_bp);
thread_db->td_create_bp = NULL;
current_thread = saved_thread;
}
}
void
thread_db_detach (struct process_info *proc)
{
struct thread_db *thread_db = proc->private->thread_db;
if (thread_db)
{
disable_thread_event_reporting (proc);
remove_thread_event_breakpoints (proc);
}
}
/* Disconnect from libthread_db and free resources. */
void
thread_db_mourn (struct process_info *proc)
{
struct thread_db *thread_db = proc->private->thread_db;
if (thread_db)
{
td_err_e (*td_ta_delete_p) (td_thragent_t *);
#ifndef USE_LIBTHREAD_DB_DIRECTLY
td_ta_delete_p = dlsym (thread_db->handle, "td_ta_delete");
#else
td_ta_delete_p = &td_ta_delete;
#endif
if (td_ta_delete_p != NULL)
(*td_ta_delete_p) (thread_db->thread_agent);
#ifndef USE_LIBTHREAD_DB_DIRECTLY
dlclose (thread_db->handle);
#endif /* USE_LIBTHREAD_DB_DIRECTLY */
free (thread_db);
proc->private->thread_db = NULL;
}
}
/* Handle "set libthread-db-search-path" monitor command and return 1.
For any other command, return 0. */
int
thread_db_handle_monitor_command (char *mon)
{
const char *cmd = "set libthread-db-search-path";
size_t cmd_len = strlen (cmd);
if (strncmp (mon, cmd, cmd_len) == 0
&& (mon[cmd_len] == '\0'
|| mon[cmd_len] == ' '))
{
const char *cp = mon + cmd_len;
if (libthread_db_search_path != NULL)
free (libthread_db_search_path);
/* Skip leading space (if any). */
while (isspace (*cp))
++cp;
if (*cp == '\0')
cp = LIBTHREAD_DB_SEARCH_PATH;
libthread_db_search_path = xstrdup (cp);
monitor_output ("libthread-db-search-path set to `");
monitor_output (libthread_db_search_path);
monitor_output ("'\n");
return 1;
}
/* Tell server.c to perform default processing. */
return 0;
}
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