RFC: Initialize libthread_db at the right time
Daniel Jacobowitz
drow@false.org
Mon Feb 27 19:59:00 GMT 2006
We've had some recurring problems debugging statically linked executables
using libthread_db; this patch is the first of several fixes for that.
This doesn't do much; it just splits the check out from the new_objfile
hook, and calls it from target_post_attach and target_post_startup_inferior
in the Linux native target.
Earlier versions of this patch used an observer instead, which was silly
of me; we only want to do this when we're sitting on top of the Linux
native target, not when we're on top of e.g. the remote target. This
mostly fixes the not-enabling-libthread_db-when-we-should-be class of
problems; there's still one gross hack in remote.c which avoids
calling the new objfile hook for remote targets, but that's a mess
for another day.
Any comments? Otherwise, I'll commit this in a few days. It handles
LinuxThreads, but NPTL needs a little push (coming up next).
--
Daniel Jacobowitz
CodeSourcery
2006-02-27 Daniel Jacobowitz <dan@codesourcery.com>
* linux-thread-db.c: Include "linux-nat.h".
(check_for_thread_db): New function, split out from
thread_db_new_objfile. Remove dead check for active
thread_db on inapplicable targets.
(thread_db_new_objfile): Call check_for_thread_db.
* Makefile.in (linux-thread-db.o): Update.
* linux-nat.c (child_post_attach): Call check_for_thread_db.
(linux_child_post_startup_inferior): Likewise.
(lin_lwp_attach_lwp): Call target_post_attach instead of
child_post_attach.
* linux-nat.h (check_for_thread_db): New prototype.
Index: src/gdb/linux-thread-db.c
===================================================================
--- src.orig/gdb/linux-thread-db.c 2006-02-27 12:44:41.000000000 -0500
+++ src/gdb/linux-thread-db.c 2006-02-27 14:36:30.000000000 -0500
@@ -37,6 +37,7 @@
#include "regcache.h"
#include "solib-svr4.h"
#include "gdbcore.h"
+#include "linux-nat.h"
#ifdef HAVE_GNU_LIBC_VERSION_H
#include <gnu/libc-version.h>
@@ -626,59 +627,49 @@ check_thread_signals (void)
#endif
}
-static void
-thread_db_new_objfile (struct objfile *objfile)
+/* Check whether thread_db is usable. This function is called when
+ an inferior is created (or otherwise acquired, e.g. attached to)
+ and when new shared libraries are loaded into a running process. */
+
+void
+check_for_thread_db (void)
{
td_err_e err;
+ static int already_loaded;
/* First time through, report that libthread_db was successfuly
loaded. Can't print this in in thread_db_load as, at that stage,
- the interpreter and it's console haven't started. The real
- problem here is that libthread_db is loaded too early - it should
- only be loaded when there is a program to debug. */
- {
- static int dejavu;
- if (!dejavu)
- {
- Dl_info info;
- const char *library = NULL;
- /* Try dladdr. */
- if (dladdr ((*td_ta_new_p), &info) != 0)
- library = info.dli_fname;
- /* Try dlinfo? */
- if (library == NULL)
- /* Paranoid - don't let a NULL path slip through. */
- library = LIBTHREAD_DB_SO;
- printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
- library);
- dejavu = 1;
- }
- }
+ the interpreter and it's console haven't started. */
- /* Don't attempt to use thread_db on targets which can not run
- (core files). */
- if (objfile == NULL || !target_has_execution)
+ if (!already_loaded)
{
- /* All symbols have been discarded. If the thread_db target is
- active, deactivate it now. */
- if (using_thread_db)
- {
- gdb_assert (proc_handle.pid == 0);
- unpush_target (&thread_db_ops);
- using_thread_db = 0;
- }
+ Dl_info info;
+ const char *library = NULL;
+ if (dladdr ((*td_ta_new_p), &info) != 0)
+ library = info.dli_fname;
+
+ /* Try dlinfo? */
+
+ if (library == NULL)
+ /* Paranoid - don't let a NULL path slip through. */
+ library = LIBTHREAD_DB_SO;
- goto quit;
+ printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
+ library);
+ already_loaded = 1;
}
if (using_thread_db)
/* Nothing to do. The thread library was already detected and the
target vector was already activated. */
- goto quit;
+ return;
- /* Initialize the structure that identifies the child process. Note
- that at this point there is no guarantee that we actually have a
- child process. */
+ /* Don't attempt to use thread_db on targets which can not run
+ (executables not running yet, core files) for now. */
+ if (!target_has_execution)
+ return;
+
+ /* Initialize the structure that identifies the child process. */
proc_handle.pid = GET_PID (inferior_ptid);
/* Now attempt to open a connection to the thread library. */
@@ -705,8 +696,14 @@ thread_db_new_objfile (struct objfile *o
thread_db_err_str (err));
break;
}
+}
+
+static void
+thread_db_new_objfile (struct objfile *objfile)
+{
+ if (objfile != NULL)
+ check_for_thread_db ();
-quit:
if (target_new_objfile_chain)
target_new_objfile_chain (objfile);
}
Index: src/gdb/Makefile.in
===================================================================
--- src.orig/gdb/Makefile.in 2006-02-27 14:16:21.000000000 -0500
+++ src/gdb/Makefile.in 2006-02-27 14:36:30.000000000 -0500
@@ -2198,7 +2198,7 @@ linux-nat.o: linux-nat.c $(defs_h) $(inf
linux-thread-db.o: linux-thread-db.c $(defs_h) $(gdb_assert_h) \
$(gdb_proc_service_h) $(gdb_thread_db_h) $(bfd_h) $(exceptions_h) \
$(gdbthread_h) $(inferior_h) $(symfile_h) $(objfiles_h) $(target_h) \
- $(regcache_h) $(solib_svr4_h) $(gdbcore_h)
+ $(regcache_h) $(solib_svr4_h) $(gdbcore_h) $(linux_nat_h)
lynx-nat.o: lynx-nat.c $(defs_h) $(frame_h) $(inferior_h) $(target_h) \
$(gdbcore_h) $(regcache_h)
m2-exp.o: m2-exp.c $(defs_h) $(gdb_string_h) $(expression_h) $(language_h) \
Index: src/gdb/linux-nat.c
===================================================================
--- src.orig/gdb/linux-nat.c 2006-02-27 12:47:52.000000000 -0500
+++ src/gdb/linux-nat.c 2006-02-27 14:36:30.000000000 -0500
@@ -334,12 +334,14 @@ void
child_post_attach (int pid)
{
linux_enable_event_reporting (pid_to_ptid (pid));
+ check_for_thread_db ();
}
static void
linux_child_post_startup_inferior (ptid_t ptid)
{
linux_enable_event_reporting (ptid);
+ check_for_thread_db ();
}
int
@@ -963,7 +965,7 @@ lin_lwp_attach_lwp (ptid_t ptid, int ver
gdb_assert (pid == GET_LWP (ptid)
&& WIFSTOPPED (status) && WSTOPSIG (status));
- child_post_attach (pid);
+ target_post_attach (pid);
lp->stopped = 1;
Index: src/gdb/linux-nat.h
===================================================================
--- src.orig/gdb/linux-nat.h 2006-02-27 12:56:19.000000000 -0500
+++ src/gdb/linux-nat.h 2006-02-27 14:36:30.000000000 -0500
@@ -65,6 +65,8 @@ struct lwp_info
struct lwp_info *next;
};
+/* Attempt to initialize libthread_db. */
+void check_for_thread_db (void);
/* Find process PID's pending signal set from /proc/pid/status. */
void linux_proc_pending_signals (int pid, sigset_t *pending, sigset_t *blocked, sigset_t *ignored);
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