Re: [RFC] Detect loops in the solib chain

[Jan Kratochvil <jan.kratochvil@redhat.com>]

On Fri, 23 Apr 2010 22:09:43 +0200, Tom Tromey wrote:
> >>>>> "Jan" == Jan Kratochvil <jan.kratochvil@redhat.com> writes:
> Jan> +	# glibc debug info is not available and it is too difficult to find and
> Jan> +	# parse it from this testcase without the gdb supporting functions.
> Jan> +	xfail "$test (no _r_debug symbol)"
> Jan> +	untested ${testfile}.exp
> Jan> +	return
> Jan> +    }
> Jan> +    -re " = 0x\[0-9a-f\]+\r\n$gdb_prompt $" {
> Jan> +	pass $test
> 
> I think it is preferable to have the test name the same, regardless of
> whether it passes or xfails.  Extra info can be logged with verbose.

Changed.  Although there are precedent cases of this, still they are therefore
probably not considered as the preferred ones.  Such as:
	gdb.base/corefile.exp
	set test "accessing mmapped data in core file"
		pass "$test"
		fail "$test (mapping failed at runtime)"
		fail "$test (mapping address not found in core file)"


> This is ok with that change.

Checked in.


Thanks,
Jan


http://sourceware.org/ml/gdb-cvs/2010-04/msg00240.html

--- src/gdb/ChangeLog	2010/04/23 18:09:16	1.11678
+++ src/gdb/ChangeLog	2010/04/23 21:44:19	1.11679
@@ -1,3 +1,14 @@
+2010-04-23  Daniel Jacobowitz  <dan@codesourcery.com>
+	    Paul Pluzhnikov  <ppluzhnikov@google.com>
+	    Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	Fix deadlock on looped list of loaded shared objects.
+	* solib-svr4.c (LM_PREV): New function.
+	(IGNORE_FIRST_LINK_MAP_ENTRY): Use it.
+	(svr4_current_sos): Check for correct l_prev.  New variables prev_lm
+	and next_lm.  Clear prev_lm for solib_svr4_r_ldsomap.
+	* config/djgpp/fnchange.lst: Add translation for solib-corrupted.exp.
+
 2010-04-23  Doug Evans  <dje@google.com>
 
 	* configure.ac (CONFIG_SRCS): Add py-auto-load.o even if not using
--- src/gdb/solib-svr4.c	2010/03/11 22:07:02	1.130
+++ src/gdb/solib-svr4.c	2010/04/23 21:44:19	1.131
@@ -272,6 +272,16 @@
 }
 
 static CORE_ADDR
+LM_PREV (struct so_list *so)
+{
+  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
+  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
+
+  return extract_typed_address (so->lm_info->lm + lmo->l_prev_offset,
+				ptr_type);
+}
+
+static CORE_ADDR
 LM_NAME (struct so_list *so)
 {
   struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
@@ -284,16 +294,12 @@
 static int
 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
 {
-  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
-  struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
-
   /* Assume that everything is a library if the dynamic loader was loaded
      late by a static executable.  */
   if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
     return 0;
 
-  return extract_typed_address (so->lm_info->lm + lmo->l_prev_offset,
-				ptr_type) == 0;
+  return LM_PREV (so) == 0;
 }
 
 /* Per pspace SVR4 specific data.  */
@@ -1101,7 +1107,7 @@
 static struct so_list *
 svr4_current_sos (void)
 {
-  CORE_ADDR lm;
+  CORE_ADDR lm, prev_lm;
   struct so_list *head = 0;
   struct so_list **link_ptr = &head;
   CORE_ADDR ldsomap = 0;
@@ -1120,6 +1126,7 @@
 
   /* Walk the inferior's link map list, and build our list of
      `struct so_list' nodes.  */
+  prev_lm = 0;
   lm = solib_svr4_r_map (info);
 
   while (lm)
@@ -1127,6 +1134,7 @@
       struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
       struct so_list *new = XZALLOC (struct so_list);
       struct cleanup *old_chain = make_cleanup (xfree, new);
+      CORE_ADDR next_lm;
 
       new->lm_info = xmalloc (sizeof (struct lm_info));
       make_cleanup (xfree, new->lm_info);
@@ -1138,14 +1146,21 @@
 
       read_memory (lm, new->lm_info->lm, lmo->link_map_size);
 
-      lm = LM_NEXT (new);
+      next_lm = LM_NEXT (new);
+
+      if (LM_PREV (new) != prev_lm)
+	{
+	  warning (_("Corrupted shared library list"));
+	  free_so (new);
+	  next_lm = 0;
+	}
 
       /* For SVR4 versions, the first entry in the link map is for the
          inferior executable, so we must ignore it.  For some versions of
          SVR4, it has no name.  For others (Solaris 2.3 for example), it
          does have a name, so we can no longer use a missing name to
          decide when to ignore it. */
-      if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap == 0)
+      else if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap == 0)
 	{
 	  info->main_lm_addr = new->lm_info->lm_addr;
 	  free_so (new);
@@ -1182,12 +1197,18 @@
 	    }
 	}
 
+      prev_lm = lm;
+      lm = next_lm;
+
       /* On Solaris, the dynamic linker is not in the normal list of
 	 shared objects, so make sure we pick it up too.  Having
 	 symbol information for the dynamic linker is quite crucial
 	 for skipping dynamic linker resolver code.  */
       if (lm == 0 && ldsomap == 0)
-	lm = ldsomap = solib_svr4_r_ldsomap (info);
+	{
+	  lm = ldsomap = solib_svr4_r_ldsomap (info);
+	  prev_lm = 0;
+	}
 
       discard_cleanups (old_chain);
     }
--- src/gdb/config/djgpp/fnchange.lst	2010/04/09 15:15:05	1.112
+++ src/gdb/config/djgpp/fnchange.lst	2010/04/23 21:44:19	1.113
@@ -397,6 +397,7 @@
 @V@/gdb/testsuite/gdb.base/siginfo-obj.c @V@/gdb/testsuite/gdb.base/si-obj.c
 @V@/gdb/testsuite/gdb.base/siginfo-addr.exp @V@/gdb/testsuite/gdb.base/si-addr.exp
 @V@/gdb/testsuite/gdb.base/siginfo-obj.exp @V@/gdb/testsuite/gdb.base/si-obj.exp
+@V@/gdb/testsuite/gdb.base/solib-corrupted.exp @V@/gdb/testsuite/gdb.base/so-crptd.exp
 @V@/gdb/testsuite/gdb.base/solib-disc.c @V@/gdb/testsuite/gdb.base/so-disc.c
 @V@/gdb/testsuite/gdb.base/solib-display-lib.c @V@/gdb/testsuite/gdb.base/so-displib.c
 @V@/gdb/testsuite/gdb.base/solib-display-main.c @V@/gdb/testsuite/gdb.base/so-dispmain.c
--- src/gdb/testsuite/ChangeLog	2010/04/23 18:03:31	1.2252
+++ src/gdb/testsuite/ChangeLog	2010/04/23 21:44:20	1.2253
@@ -1,3 +1,8 @@
+2010-04-23  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	Fix deadlock on looped list of loaded shared objects.
+	* gdb.base/solib-corrupted.exp: New.
+
 2010-04-23  Doug Evans  <dje@google.com>
 
 	* gdb.python/py-section-script.c: New file.
--- src/gdb/testsuite/gdb.base/solib-corrupted.exp
+++ src/gdb/testsuite/gdb.base/solib-corrupted.exp	2010-04-23 21:44:35.962406000 +0000
@@ -0,0 +1,46 @@
+# Copyright 2010 Free Software Foundation, Inc.
+
+# 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/>.
+
+set testfile "solib-corrupted"
+set srcfile start.c
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+    untested ${testfile}.exp
+    return -1
+}
+
+if ![runto_main] {
+    fail "Can't run to main"
+    return
+}
+
+gdb_test "info sharedlibrary" "" "normal list"
+
+# GDB checks there for matching L_PREV.
+set test "make solibs looping"
+gdb_test_multiple "p/x _r_debug->r_map->l_next = _r_debug->r_map" $test {
+    -re "(No symbol \"_r_debug\" in current context\\.|Attempt to extract a component of a value that is not a structure pointer\\.)\r\n$gdb_prompt $" {
+	# glibc debug info is not available and it is too difficult to find and
+	# parse it from this testcase without the gdb supporting functions.
+	verbose -log "no _r_debug symbol has been found"
+	xfail $test
+	untested ${testfile}.exp
+	return
+    }
+    -re " = 0x\[0-9a-f\]+\r\n$gdb_prompt $" {
+	pass $test
+    }
+}
+gdb_test "info sharedlibrary" "warning: Corrupted shared library list\r\n.*" "corrupted list"