[patch][rfc] Allow GDB to search for the right libthread_db.so.1
Paul Pluzhnikov
ppluzhnikov@google.com
Mon Apr 20 17:37:00 GMT 2009
On Mon, Apr 20, 2009 at 9:47 AM, Paul Pluzhnikov <ppluzhnikov@google.com> wrote:
> Attached is a revised patch that fixes all the comments so far.
Sorry, missed the NEWS update.
Thanks,
--
Paul Pluzhnikov
2009-04-20 Paul Pluzhnikov <ppluzhnikov@google.com>
* NEWS: Mention set/show libthread-db-search-path.
* gdb_thread_db.h (LIBTHREAD_DB_SEARCH_PATH): New define.
(LIBTHREAD_DB_SO): Moved from linux-thread-db.c
* linux-thread-db.c (libthread_db_search_path): New setting.
(thread_db_handle): New variable (replaces using_thread_db).
(try_thread_db_load_1): New function.
(try_thread_db_load, thread_db_load_search): Likewise.
(dladdr_to_soname): Likewise.
(thread_db_load): Iterate over possibly multiple libthread_db's.
(check_for_thread_db): Attempt to load new libthread_db.
(thread_db_detach, thread_db_wait): Unload libthread_db.
(thread_db_mourn_inferior): Likewise.
(_initialize_thread_db): Add new libthread-db-search-path option.
Defer loading of libthread_db to check_for_thread_db.
doc/ChangeLog
2009-04-20 Paul Pluzhnikov <ppluzhnikov@google.com>
* gdb.texinfo (Threads): Document libthread-db-search-path.
-------------- next part --------------
Index: NEWS
===================================================================
RCS file: /cvs/src/src/gdb/NEWS,v
retrieving revision 1.307
diff -u -p -u -r1.307 NEWS
--- NEWS 19 Apr 2009 20:05:23 -0000 1.307
+++ NEWS 20 Apr 2009 17:35:40 -0000
@@ -284,6 +284,11 @@ show tcp connect-timeout
with a specified timeout period; this is useful if the stub is launched
in parallel with GDB but may not be ready to accept connections immediately.
+set libthread-db-search-path
+show libthread-db-search-path
+ Control list of directories which GDB will search for appropriate
+ libthread_db.
+
* New native configurations
x86/x86_64 Darwin i[34567]86-*-darwin*
Index: gdb_thread_db.h
===================================================================
RCS file: /cvs/src/src/gdb/gdb_thread_db.h,v
retrieving revision 1.12
diff -u -p -u -r1.12 gdb_thread_db.h
--- gdb_thread_db.h 18 Mar 2009 08:51:11 -0000 1.12
+++ gdb_thread_db.h 20 Apr 2009 17:35:40 -0000
@@ -1,5 +1,14 @@
#ifdef HAVE_THREAD_DB_H
#include <thread_db.h>
+
+#ifndef LIBTHREAD_DB_SO
+#define LIBTHREAD_DB_SO "libthread_db.so.1"
+#endif
+
+#ifndef LIBTHREAD_DB_SEARCH_PATH
+#define LIBTHREAD_DB_SEARCH_PATH ""
+#endif
+
#else
/* Copyright (C) 1999, 2000, 2007, 2008, 2009 Free Software Foundation, Inc.
Index: linux-thread-db.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-thread-db.c,v
retrieving revision 1.54
diff -u -p -u -r1.54 linux-thread-db.c
--- linux-thread-db.c 27 Feb 2009 20:34:41 -0000 1.54
+++ linux-thread-db.c 20 Apr 2009 17:35:40 -0000
@@ -26,13 +26,16 @@
#include "gdb_thread_db.h"
#include "bfd.h"
+#include "command.h"
#include "exceptions.h"
+#include "gdbcmd.h"
#include "gdbthread.h"
#include "inferior.h"
#include "symfile.h"
#include "objfiles.h"
#include "target.h"
#include "regcache.h"
+#include "solib.h"
#include "solib-svr4.h"
#include "gdbcore.h"
#include "observer.h"
@@ -44,10 +47,6 @@
#include <gnu/libc-version.h>
#endif
-#ifndef LIBTHREAD_DB_SO
-#define LIBTHREAD_DB_SO "libthread_db.so.1"
-#endif
-
/* GNU/Linux libthread_db support.
libthread_db is a library, provided along with libpthread.so, which
@@ -74,14 +73,17 @@
of the ptid_t prevents thread IDs changing when libpthread is
loaded or unloaded. */
+static char *libthread_db_search_path;
+
/* If we're running on GNU/Linux, we must explicitly attach to any new
threads. */
/* This module's target vector. */
static struct target_ops thread_db_ops;
-/* Non-zero if we're using this module's target vector. */
-static int using_thread_db;
+/* Handle from dlopen for libthread_db.so. Not NULL if we're using this
+ module's target vector. */
+static void *thread_db_handle;
/* Non-zero if we have determined the signals used by the threads
library. */
@@ -344,7 +346,7 @@ thread_db_attach_lwp (ptid_t ptid)
td_thrinfo_t ti;
td_err_e err;
- if (!using_thread_db)
+ if (thread_db_handle == NULL)
return 0;
/* This ptid comes from linux-nat.c, which should always fill in the
@@ -385,71 +387,6 @@ verbose_dlsym (void *handle, const char
return sym;
}
-static int
-thread_db_load (void)
-{
- void *handle;
- td_err_e err;
-
- handle = dlopen (LIBTHREAD_DB_SO, RTLD_NOW);
- if (handle == NULL)
- {
- fprintf_filtered (gdb_stderr, "\n\ndlopen failed on '%s' - %s\n",
- LIBTHREAD_DB_SO, dlerror ());
- fprintf_filtered (gdb_stderr,
- "GDB will not be able to debug pthreads.\n\n");
- return 0;
- }
-
- /* Initialize pointers to the dynamic library functions we will use.
- Essential functions first. */
-
- td_init_p = verbose_dlsym (handle, "td_init");
- if (td_init_p == NULL)
- return 0;
-
- td_ta_new_p = verbose_dlsym (handle, "td_ta_new");
- if (td_ta_new_p == NULL)
- return 0;
-
- td_ta_map_id2thr_p = verbose_dlsym (handle, "td_ta_map_id2thr");
- if (td_ta_map_id2thr_p == NULL)
- return 0;
-
- td_ta_map_lwp2thr_p = verbose_dlsym (handle, "td_ta_map_lwp2thr");
- if (td_ta_map_lwp2thr_p == NULL)
- return 0;
-
- td_ta_thr_iter_p = verbose_dlsym (handle, "td_ta_thr_iter");
- if (td_ta_thr_iter_p == NULL)
- return 0;
-
- td_thr_validate_p = verbose_dlsym (handle, "td_thr_validate");
- if (td_thr_validate_p == NULL)
- return 0;
-
- td_thr_get_info_p = verbose_dlsym (handle, "td_thr_get_info");
- if (td_thr_get_info_p == NULL)
- return 0;
-
- /* Initialize the library. */
- err = td_init_p ();
- if (err != TD_OK)
- {
- warning (_("Cannot initialize libthread_db: %s"), thread_db_err_str (err));
- return 0;
- }
-
- /* These are not essential. */
- td_ta_event_addr_p = dlsym (handle, "td_ta_event_addr");
- td_ta_set_event_p = dlsym (handle, "td_ta_set_event");
- td_ta_event_getmsg_p = dlsym (handle, "td_ta_event_getmsg");
- td_thr_event_enable_p = dlsym (handle, "td_thr_event_enable");
- td_thr_tls_get_addr_p = dlsym (handle, "td_thr_tls_get_addr");
-
- return 1;
-}
-
static td_err_e
enable_thread_event (td_thragent_t *thread_agent, int event, CORE_ADDR *bp)
{
@@ -541,6 +478,275 @@ enable_thread_event_reporting (void)
}
}
+/* Attempt to initialize dlopen()ed libthread_db, described by HANDLE.
+ Return 1 on success.
+ Failure could happen if libthread_db does not have symbols we expect,
+ or when it refuses to work with the current inferior (e.g. due to
+ version mismatch between libthread_db and libpthread). */
+
+static int
+try_thread_db_load_1 (void *handle)
+{
+ td_err_e err;
+
+ /* Initialize pointers to the dynamic library functions we will use.
+ Essential functions first. */
+
+ td_init_p = verbose_dlsym (handle, "td_init");
+ if (td_init_p == NULL)
+ return 0;
+
+ err = td_init_p ();
+ if (err != TD_OK)
+ {
+ warning (_("Cannot initialize libthread_db: %s"), thread_db_err_str (err));
+ return 0;
+ }
+
+ td_ta_new_p = verbose_dlsym (handle, "td_ta_new");
+ if (td_ta_new_p == NULL)
+ return 0;
+
+ /* Initialize the structure that identifies the child process. */
+ proc_handle.ptid = inferior_ptid;
+
+ /* Now attempt to open a connection to the thread library. */
+ err = td_ta_new_p (&proc_handle, &thread_agent);
+ if (err != TD_OK)
+ {
+ td_ta_new_p = NULL;
+ if (info_verbose)
+ printf_unfiltered (_("td_ta_new failed: %s\n"),
+ thread_db_err_str (err));
+ else
+ switch (err)
+ {
+ case TD_NOLIBTHREAD:
+#ifdef THREAD_DB_HAS_TD_VERSION
+ case TD_VERSION:
+#endif
+ /* The errors above are not unexpected and silently ignored:
+ they just mean we haven't found correct version of
+ libthread_db yet. */
+ break;
+ default:
+ warning (_("td_ta_new failed: %s"), thread_db_err_str (err));
+ }
+ return 0;
+ }
+
+ td_ta_map_id2thr_p = verbose_dlsym (handle, "td_ta_map_id2thr");
+ if (td_ta_map_id2thr_p == NULL)
+ return 0;
+
+ td_ta_map_lwp2thr_p = verbose_dlsym (handle, "td_ta_map_lwp2thr");
+ if (td_ta_map_lwp2thr_p == NULL)
+ return 0;
+
+ td_ta_thr_iter_p = verbose_dlsym (handle, "td_ta_thr_iter");
+ if (td_ta_thr_iter_p == NULL)
+ return 0;
+
+ td_thr_validate_p = verbose_dlsym (handle, "td_thr_validate");
+ if (td_thr_validate_p == NULL)
+ return 0;
+
+ td_thr_get_info_p = verbose_dlsym (handle, "td_thr_get_info");
+ if (td_thr_get_info_p == NULL)
+ return 0;
+
+ /* These are not essential. */
+ td_ta_event_addr_p = dlsym (handle, "td_ta_event_addr");
+ td_ta_set_event_p = dlsym (handle, "td_ta_set_event");
+ td_ta_event_getmsg_p = dlsym (handle, "td_ta_event_getmsg");
+ td_thr_event_enable_p = dlsym (handle, "td_thr_event_enable");
+ td_thr_tls_get_addr_p = dlsym (handle, "td_thr_tls_get_addr");
+
+ printf_unfiltered (_("[Thread debugging using libthread_db enabled]\n"));
+
+ /* The thread library was detected. Activate the thread_db target. */
+ push_target (&thread_db_ops);
+ thread_db_handle = handle;
+
+ enable_thread_event_reporting ();
+ thread_db_find_new_threads_1 ();
+ return 1;
+}
+
+/* Lookup a library in which given symbol resides.
+ Note: this is looking in GDB 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;
+}
+
+/* Attempt to use LIBRARY as libthread_db. LIBRARY could be absolute,
+ relative, or just LIBTHREAD_DB. */
+
+static int
+try_thread_db_load (const char *library)
+{
+ void *handle;
+
+ if (info_verbose)
+ printf_unfiltered (_("Trying host libthread_db library: %s.\n"),
+ library);
+ handle = dlopen (library, RTLD_NOW);
+ if (handle == NULL)
+ {
+ if (info_verbose)
+ printf_unfiltered (_("dlopen failed: %s.\n"), dlerror ());
+ return 0;
+ }
+
+ if (info_verbose && 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)
+ printf_unfiltered (_("Host %s resolved to: %s.\n"),
+ library, libpath);
+ }
+ }
+
+ if (try_thread_db_load_1 (handle))
+ return 1;
+
+ /* This library "refused" to work on current inferior. */
+ dlclose (handle);
+ return 0;
+}
+
+
+/* Search libthread_db_search_path for libthread_db which "agrees"
+ to work on current inferior. */
+
+static int
+thread_db_load_search ()
+{
+ char path[PATH_MAX];
+ const char *search_path = libthread_db_search_path;
+ int rc = 0;
+
+ while (*search_path)
+ {
+ const char *end = strchr (search_path, ':');
+ if (end)
+ {
+ size_t len = end - search_path;
+ if (len + 1 + strlen (LIBTHREAD_DB_SO) + 1 > sizeof (path))
+ {
+ char *cp = xmalloc (len + 1);
+ memcpy (cp, search_path, len);
+ cp[len] = '\0';
+ warning (_("libthread_db_search_path component too long,"
+ " ignored: %s."), cp);
+ xfree (cp);
+ search_path += len + 1;
+ continue;
+ }
+ memcpy (path, search_path, len);
+ path[len] = '\0';
+ search_path += len + 1;
+ }
+ else
+ {
+ size_t len = strlen (search_path);
+
+ if (len + 1 + strlen (LIBTHREAD_DB_SO) + 1 > sizeof (path))
+ {
+ warning (_("libthread_db_search_path component too long,"
+ " ignored: %s."), search_path);
+ break;
+ }
+ memcpy (path, search_path, len + 1);
+ search_path += len;
+ }
+ strcat (path, "/");
+ strcat (path, LIBTHREAD_DB_SO);
+ if (try_thread_db_load (path))
+ {
+ rc = 1;
+ break;
+ }
+ }
+ if (rc == 0)
+ rc = try_thread_db_load (LIBTHREAD_DB_SO);
+ if (rc == 0)
+ warning (_("Unable to find libthread_db matching inferior's thread"
+ " library, thread debugging will not be available."));
+ return rc;
+}
+
+/* Attempt to load and initialize libthread_db.
+ Return 1 on success.
+ */
+
+static int
+thread_db_load (void)
+{
+ const char *soname;
+ struct minimal_symbol *msym;
+
+ if (thread_db_handle != NULL)
+ return 1;
+
+ /* 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 0;
+
+ /* Don't attempt to use thread_db for remote targets. */
+ if (!target_can_run (¤t_target))
+ return 0;
+
+ msym = lookup_minimal_symbol ("nptl_version", NULL, NULL);
+ if (!msym)
+ msym = lookup_minimal_symbol ("__linuxthreads_version", NULL, NULL);
+
+ /* Some really old libpthread versions do not have either of the above. */
+ if (!msym)
+ msym = lookup_minimal_symbol ("__pthread_threads_events", NULL, NULL);
+
+ if (!msym)
+ /* No threads yet */
+ return 0;
+
+ soname = solib_name_from_address (SYMBOL_VALUE_ADDRESS (msym));
+ if (soname)
+ {
+ /* Attempt to load libthread_db from the same directory. */
+ char path[PATH_MAX], *cp;
+ strcpy (path, soname);
+ cp = strrchr (path, '/');
+ if (cp == NULL)
+ {
+ /* Expected to get fully resolved pathname for libpthread,
+ but got something else. Search for matching libthread_db and
+ hope there is one that matches current libpthread. */
+ warning (_("Cannot obtain absolute path of thread library: %s."),
+ soname);
+ return thread_db_load_search ();
+ }
+ strcpy (cp + 1, LIBTHREAD_DB_SO);
+ if (try_thread_db_load (path))
+ return 1;
+ }
+ return thread_db_load_search ();
+}
+
static void
disable_thread_event_reporting (void)
{
@@ -593,75 +799,34 @@ void
check_for_thread_db (void)
{
td_err_e err;
- static int already_loaded;
+ static void *last_loaded;
/* Do nothing if we couldn't load libthread_db.so.1. */
- if (td_ta_new_p == NULL)
+ if (!thread_db_load ())
return;
/* 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 interpreter and it's console haven't started.
+ We track td_ta_new_p because the user may switch executables,
+ and as a result we may decide to use a different version of
+ libthread_db. */
- if (!already_loaded)
+ if (last_loaded != td_ta_new_p)
{
- Dl_info info;
- const char *library = NULL;
- if (dladdr ((*td_ta_new_p), &info) != 0)
- library = info.dli_fname;
+ last_loaded = td_ta_new_p;
- /* Try dlinfo? */
-
- if (library == NULL)
- /* Paranoid - don't let a NULL path slip through. */
- library = LIBTHREAD_DB_SO;
-
- if (info_verbose)
- 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. */
- return;
-
- /* 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;
-
- /* Don't attempt to use thread_db for remote targets. */
- if (!target_can_run (¤t_target))
- return;
-
- /* Initialize the structure that identifies the child process. */
- proc_handle.ptid = inferior_ptid;
-
- /* Now attempt to open a connection to the thread library. */
- err = td_ta_new_p (&proc_handle, &thread_agent);
- switch (err)
- {
- case TD_NOLIBTHREAD:
- /* No thread library was detected. */
- break;
-
- case TD_OK:
- printf_unfiltered (_("[Thread debugging using libthread_db enabled]\n"));
-
- /* The thread library was detected. Activate the thread_db target. */
- push_target (&thread_db_ops);
- using_thread_db = 1;
-
- enable_thread_event_reporting ();
- thread_db_find_new_threads_1 ();
- break;
-
- default:
- warning (_("Cannot initialize thread debugging library: %s"),
- thread_db_err_str (err));
- break;
+ if (info_verbose || *libthread_db_search_path)
+ {
+ const char *library;
+
+ library = dladdr_to_soname (*td_ta_new_p);
+ if (library == NULL)
+ library = LIBTHREAD_DB_SO;
+
+ printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
+ library);
+ }
}
}
@@ -783,7 +948,9 @@ thread_db_detach (struct target_ops *ops
/* Detach thread_db target ops. */
unpush_target (&thread_db_ops);
- using_thread_db = 0;
+ if (thread_db_handle)
+ dlclose (thread_db_handle);
+ thread_db_handle = NULL;
target_beneath->to_detach (target_beneath, args, from_tty);
}
@@ -896,7 +1063,9 @@ thread_db_wait (struct target_ops *ops,
{
remove_thread_event_breakpoints ();
unpush_target (&thread_db_ops);
- using_thread_db = 0;
+ if (thread_db_handle)
+ dlclose (thread_db_handle);
+ thread_db_handle = NULL;
return ptid;
}
@@ -944,7 +1113,9 @@ thread_db_mourn_inferior (struct target_
/* Detach thread_db target ops. */
unpush_target (ops);
- using_thread_db = 0;
+ if (thread_db_handle)
+ dlclose (thread_db_handle);
+ thread_db_handle = NULL;
}
static int
@@ -1187,13 +1358,28 @@ extern initialize_file_ftype _initialize
void
_initialize_thread_db (void)
{
- /* Only initialize the module if we can load libthread_db. */
- if (thread_db_load ())
- {
- init_thread_db_ops ();
- add_target (&thread_db_ops);
+ init_thread_db_ops ();
+ add_target (&thread_db_ops);
- /* Add ourselves to objfile event chain. */
- observer_attach_new_objfile (thread_db_new_objfile);
- }
+ /* Defer loading of libthread_db.so until inferior is running.
+ This allows gdb to load correct libthread_db for a given
+ executable -- there could be mutiple versions of glibc,
+ compiled with LinuxThreads or NPTL, and until there is
+ a running inferior, we can't tell which libthread_db is
+ the correct one to load. */
+
+ libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
+
+ add_setshow_optional_filename_cmd ("libthread-db-search-path",
+ class_support,
+ &libthread_db_search_path, _("\
+Set search path for libthread_db."), _("\
+Show the current search path or libthread_db."), _("\
+This path is used to search for libthread_db to be loaded into \
+gdb itself."),
+ NULL,
+ NULL,
+ &setlist, &showlist);
+ /* Add ourselves to objfile event chain. */
+ observer_attach_new_objfile (thread_db_new_objfile);
}
Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.580
diff -u -p -u -r1.580 gdb.texinfo
--- doc/gdb.texinfo 15 Apr 2009 22:20:32 -0000 1.580
+++ doc/gdb.texinfo 20 Apr 2009 17:35:40 -0000
@@ -2429,6 +2429,9 @@ a command to apply a command to a list o
@item thread-specific breakpoints
@item @samp{set print thread-events}, which controls printing of
messages on thread start and exit.
+@item @samp{set libthread-db-search-path @var{path}}, which lets
+the user specify which @code{libthread_db} to use if the default choice
+isn't compatible with the program.
@end itemize
@quotation
@@ -2647,6 +2650,40 @@ programs with multiple threads.
@xref{Set Watchpoints,,Setting Watchpoints}, for information about
watchpoints in programs with multiple threads.
+@table @code
+@kindex set libthread-db-search-path
+@cindex search path for @code{libthread_db}
+@item set libthread-db-search-path @r{[}@var{path}@r{]}
+If this variable is set, @var{path} is a colon-separated list of
+directories @value{GDBN} will use to search for @code{libthread_db}.
+If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
+an empty list.
+
+On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
+@code{libthread_db} library to obtain information about threads in the
+inferior process. @value{GDBN} first attempts to use
+@code{libthread_db} located in the directory from which
+@code{libpthread} was loaded in the inferior process. If that fails,
+@value{GDBN} will use @samp{libthread-db-search-path},
+and then default system shared library directories, to find
+@code{libthread_db}.
+
+For any @code{libthread_db} library @value{GDBN} finds in above directories,
+@value{GDBN} attempts to initialize it with the current inferior process.
+If this initialization fails (which could happen because of a version
+mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
+will unload @code{libthread_db}, and continue with the next directory.
+If none of @code{libthread_db} libraries initialize successfully,
+@value{GDBN} will issue a warning and thread debugging will be disabled.
+
+Setting @code{libthread-db-search-path} is currently implemented
+only on some platforms.
+
+@kindex show libthread-db-search-path
+@item show libthread-db-search-path
+Display current libthread_db search path.
+@end table
+
@node Processes
@section Debugging Programs with Multiple Processes
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