http://sourceware.org/ml/gdb-patches/2009-10/msg00142.html
Subject: [patch] Fix GNU/Linux core open: Can't read pathname for load map:  Input/output error.

[ New patch variant.  ]

Index: gdb-7.4.50.20120703/gdb/solib-svr4.c
===================================================================
--- gdb-7.4.50.20120703.orig/gdb/solib-svr4.c	2012-07-06 15:39:57.000000000 +0200
+++ gdb-7.4.50.20120703/gdb/solib-svr4.c	2012-07-06 15:40:01.124816148 +0200
@@ -1221,8 +1221,17 @@ svr4_read_so_list (CORE_ADDR lm, struct
 			  SO_NAME_MAX_PATH_SIZE - 1, &errcode);
       if (errcode != 0)
 	{
-	  warning (_("Can't read pathname for load map: %s."),
-		   safe_strerror (errcode));
+	  /* During the first ever DSO list reading some strings may be
+	     unreadable as residing in the ld.so readonly memory not being
+	     present in a dumped core file.  Delay the error check after
+	     the first pass of DSO list scanning when ld.so should be
+	     already mapped in and all the DSO list l_name memory gets
+	     readable.  */
+
+	  if (master_so_list () != NULL)
+	    warning (_("Can't read pathname for load map: %s."),
+		     safe_strerror (errcode));
+
 	  do_cleanups (old_chain);
 	  continue;
 	}
Index: gdb-7.4.50.20120703/gdb/solib.c
===================================================================
--- gdb-7.4.50.20120703.orig/gdb/solib.c	2012-07-06 15:38:39.000000000 +0200
+++ gdb-7.4.50.20120703/gdb/solib.c	2012-07-06 15:40:01.125816147 +0200
@@ -672,7 +672,7 @@ solib_used (const struct so_list *const
    processes we've just attached to, so that's okay.  */
 
 static void
-update_solib_list (int from_tty, struct target_ops *target)
+update_solib_list_1 (int from_tty, struct target_ops *target)
 {
   struct target_so_ops *ops = solib_ops (target_gdbarch);
   struct so_list *inferior = ops->current_sos();
@@ -843,6 +843,21 @@ Do you need \"set solib-search-path\" or
     }
 }
 
+/* Wrapper for Fedora: gdb-core-open-vdso-warning.patch  */
+
+static void
+update_solib_list (int from_tty, struct target_ops *target)
+{
+  struct so_list *saved_so_list_head = so_list_head;
+
+  update_solib_list_1 (from_tty, target);
+
+  /* If this was the very first DSO list scan and we possibly read in ld.so
+     recheck all the formerly unreadable DSO names strings.  */
+
+  if (saved_so_list_head == NULL && so_list_head != NULL)
+    update_solib_list_1 (from_tty, target);
+}
 
 /* Return non-zero if NAME is the libpthread shared library.
 
Index: gdb-7.4.50.20120703/gdb/testsuite/gdb.base/corefile.exp
===================================================================
--- gdb-7.4.50.20120703.orig/gdb/testsuite/gdb.base/corefile.exp	2012-07-06 15:39:41.000000000 +0200
+++ gdb-7.4.50.20120703/gdb/testsuite/gdb.base/corefile.exp	2012-07-06 15:40:10.322805539 +0200
@@ -286,3 +286,19 @@ if {$buildid == ""} {
     gdb_test "info files" "Local exec file:\r\n\[ \t\]*`[string_to_regexp $debugdir/$buildid]', file type .*"
     pass $wholetest
 }
+
+
+# Test Linux specific vDSO warning:
+# warning: Can't read pathname for load map: Input/output error.
+
+clean_restart ${testfile}
+
+set test "core-file vdso warning"
+gdb_test_multiple "core-file $corefile" $test {
+    -re "warning: Can't read pathname for load map: Input/output error\\.\r\n.*\r\n$gdb_prompt $" {
+	fail $test
+    }
+    -re "\r\n$gdb_prompt $" {
+	pass $test
+    }
+}
Index: gdb-7.4.50.20120703/gdb/testsuite/gdb.base/solib-symbol.exp
===================================================================
--- gdb-7.4.50.20120703.orig/gdb/testsuite/gdb.base/solib-symbol.exp	2012-07-06 15:38:39.000000000 +0200
+++ gdb-7.4.50.20120703/gdb/testsuite/gdb.base/solib-symbol.exp	2012-07-06 15:40:01.127816145 +0200
@@ -27,7 +27,8 @@ set lib_flags [list debug ldflags=-Wl,-B
 # Binary file.
 set testfile "solib-symbol-main"
 set srcfile ${srcdir}/${subdir}/${testfile}.c
-set binfile ${objdir}/${subdir}/${testfile}
+set executable ${testfile}
+set binfile ${objdir}/${subdir}/${executable}
 set bin_flags [list debug shlib=${binfile_lib}]
 
 if [get_compiler_info] {
@@ -72,8 +73,26 @@ gdb_test "br foo2" \
 	 "Breakpoint.*: foo2. .2 locations..*" \
 	 "foo2 in mdlib"
 
-gdb_exit
+# Test GDB warns for shared libraris which have not been found.
 
-return 0
+gdb_test "info sharedlibrary" "/${libname}.*"
 
+clean_restart ${executable}
+gdb_breakpoint "main"
+gdb_run_cmd
+set test "no warning for missing libraries"
+gdb_test_multiple "" $test {
+    -re "warning: Could not load shared library symbols for \[0-9\]+ libraries,.*\r\n$gdb_prompt $" {
+	fail $test
+    }
+    -re "Breakpoint \[0-9\]+, main .*\r\n$gdb_prompt $" {
+	pass $test
+    }
+}
 
+clean_restart ${executable}
+gdb_test_no_output "set solib-absolute-prefix /doESnotEXIST"
+gdb_breakpoint "main"
+gdb_run_cmd
+gdb_test "" "warning: Could not load shared library symbols for \[0-9\]+ libraries,.*\r\nBreakpoint \[0-9\]+, main .*" \
+	 "warning for missing libraries"