gdb: try to load libthread_db only after reading all shared libraries when attaching...

author Simon Marchi <simon.marchi@polymtl.ca>

Tue, 8 Jun 2021 20:50:53 +0000 (16:50 -0400)

committer Simon Marchi <simon.marchi@polymtl.ca>

Tue, 8 Jun 2021 20:51:00 +0000 (16:51 -0400)
author Simon Marchi <simon.marchi@polymtl.ca>
Tue, 8 Jun 2021 20:50:53 +0000 (16:50 -0400)
committer Simon Marchi <simon.marchi@polymtl.ca>
Tue, 8 Jun 2021 20:51:00 +0000 (16:51 -0400)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog

index 53d77aab62a70f2e8f8339dd454666b7de7bdc05..05c307bd303882fa7b8390d66a8db1d728c330b7 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,15 @@
+2021-06-08  Simon Marchi  <simon.marchi@polymtl.ca>
+
+       * inferior.h (class inferior) <in_initial_library_scan>: New.
+       * infcmd.c (post_create_inferior): Set in_initial_library_scan.
+       * infrun.c (follow_fork_inferior): Likewise.
+       * linux-thread-db.c (try_thread_db_load): Catch exception thrown
+       by try_thread_db_load_1
+       (thread_db_load): Return early if in_initial_library_scan is
+       set.
+       * remote.c (remote_new_objfile): Return early if
+       in_initial_library_scan is set.
+
  2021-06-07  Pedro Alves  <pedro@palves.net>
  
         * dwarf2/read.c (struct partial_die_info): Add defaulted copy
diff --git a/gdb/infcmd.c b/gdb/infcmd.c

index 38947ca265e84a4a4333c31a1ca2ee57c22fff31..8190ba36565eca56c1942a074af1c05ac30dba21 100644 (file)
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -315,6 +315,10 @@ post_create_inferior (int from_tty)
        const unsigned solib_add_generation
         = current_program_space->solib_add_generation;
  
+      scoped_restore restore_in_initial_library_scan
+       = make_scoped_restore (&current_inferior ()->in_initial_library_scan,
+                              true);
+
        /* Create the hooks to handle shared library load and unload
          events.  */
        solib_create_inferior_hook (from_tty);
diff --git a/gdb/inferior.h b/gdb/inferior.h

index f4b8b025e35362d6c6aae9fcaff0b3243402d2f8..f61b5889e858f69e9c4f3f140f929e1a2ae7dfa1 100644 (file)
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -522,6 +522,10 @@ public:
       architecture/description.  */
    bool needs_setup = false;
  
+  /* True when we are reading the library list of the inferior during an
+     attach or handling a fork child.  */
+  bool in_initial_library_scan = false;
+
    /* Private data used by the target vector implementation.  */
    std::unique_ptr<private_inferior> priv;
  
diff --git a/gdb/infrun.c b/gdb/infrun.c

index 488bcc1e10bcf3e9fd3e27e098561097766b592f..4bd21fde590790d8b442db5d387870ae26733022 100644 (file)
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -521,6 +521,9 @@ holding the child stopped.  Try \"set detach-on-fork\" or \
                  breakpoint.  If a "cloned-VM" event was propagated
                  better throughout the core, this wouldn't be
                  required.  */
+             scoped_restore restore_in_initial_library_scan
+               = make_scoped_restore (&child_inf->in_initial_library_scan,
+                                      true);
               solib_create_inferior_hook (0);
             }
         }
@@ -656,6 +659,8 @@ holding the child stopped.  Try \"set detach-on-fork\" or \
              shared libraries, and install the solib event breakpoint.
              If a "cloned-VM" event was propagated better throughout
              the core, this wouldn't be required.  */
+         scoped_restore restore_in_initial_library_scan
+           = make_scoped_restore (&child_inf->in_initial_library_scan, true);
           solib_create_inferior_hook (0);
         }
  
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c

index 9925b02e7780258c611a2ee9e8a9a90bb73ae947..d1e8c22ac96233f9171ce88cb8aa19f44d97ab02 100644 (file)
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -1012,8 +1012,17 @@ try_thread_db_load (const char *library, bool check_auto_load_safe)
    if (strchr (library, '/') != NULL)
      info->filename = gdb_realpath (library).release ();
  
-  if (try_thread_db_load_1 (info))
-    return true;
+  try
+    {
+      if (try_thread_db_load_1 (info))
+       return true;
+    }
+  catch (const gdb_exception_error &except)
+    {
+      if (libthread_db_debug)
+       exception_fprintf (gdb_stdlog, except,
+                          "Warning: While trying to load libthread_db: ");
+    }
  
    /* This library "refused" to work on current inferior.  */
    delete_thread_db_info (current_inferior ()->process_target (),
@@ -1184,10 +1193,15 @@ has_libpthread (void)
  static bool
  thread_db_load (void)
  {
-  struct thread_db_info *info;
+  inferior *inf = current_inferior ();
  
-  info = get_thread_db_info (current_inferior ()->process_target (),
-                            inferior_ptid.pid ());
+  /* When attaching / handling fork child, don't try loading libthread_db
+     until we know about all shared libraries.  */
+  if (inf->in_initial_library_scan)
+    return false;
+
+  thread_db_info *info = get_thread_db_info (inf->process_target (),
+                                            inferior_ptid.pid ());
  
    if (info != NULL)
      return true;
diff --git a/gdb/remote.c b/gdb/remote.c

index de04aab43dc9e5fac71bf53fe316f7ca6321d526..39bdd2e4ab08246b9c8fde9198f4c87ebb27c0a0 100644 (file)
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -14522,8 +14522,26 @@ remote_new_objfile (struct objfile *objfile)
  {
    remote_target *remote = get_current_remote_target ();
  
-  if (remote != NULL)                  /* Have a remote connection.  */
-    remote->remote_check_symbols ();
+  /* First, check whether the current inferior's process target is a remote
+     target.  */
+  if (remote == nullptr)
+    return;
+
+  /* When we are attaching or handling a fork child and the shared library
+     subsystem reads the list of loaded libraries, we receive new objfile
+     events in between each found library.  The libraries are read in an
+     undefined order, so if we gave the remote side a chance to look up
+     symbols between each objfile, we might give it an inconsistent picture
+     of the inferior.  It could appear that a library A appears loaded but
+     a library B does not, even though library A requires library B.  That
+     would present a state that couldn't normally exist in the inferior.
+
+     So, skip these events, we'll give the remote a chance to look up symbols
+     once all the loaded libraries and their symbols are known to GDB.  */
+    if (current_inferior ()->in_initial_library_scan)
+      return;
+
+  remote->remote_check_symbols ();
  }
  
  /* Pull all the tracepoints defined on the target and create local
author	Simon Marchi <simon.marchi@polymtl.ca>
	Tue, 8 Jun 2021 20:50:53 +0000 (16:50 -0400)
committer	Simon Marchi <simon.marchi@polymtl.ca>
	Tue, 8 Jun 2021 20:51:00 +0000 (16:51 -0400)
gdb/ChangeLog		patch \| blob \| history
gdb/infcmd.c		patch \| blob \| history
gdb/inferior.h		patch \| blob \| history
gdb/infrun.c		patch \| blob \| history
gdb/linux-thread-db.c		patch \| blob \| history
gdb/remote.c		patch \| blob \| history