Re: [PATCH v2] Skip vDSO when reading SO list (PR 8882)

[Andreas Arnez <arnez@linux.vnet.ibm.com>]

Jan Kratochvil <jan.kratochvil@redhat.com> writes:

> Nested negations were not accepted for GDB before, therefore:
> 	  if (first == NULL
> 	      || new->lm_info->l_name != first->lm_info->l_name)
>
> (I agree it had some logic but this was a general GDB list consensus.)

Sure.  This is one of the few cases where I wish C had an "unless"
conditional :-)

--
Andreas


ChangeLog:
2013-09-25  Andreas Arnez  <arnez@linux.vnet.ibm.com>

	PR shlibs/8882
	* solib-svr4.c (svr4_read_so_list): Skip the vDSO when reading
	link map entries.

testsuite/ChangeLog:
2013-09-25  Andreas Arnez  <arnez@linux.vnet.ibm.com>

	PR shlibs/8882
	* gdb.base/corefile.exp: Add a check to assure warning-free
	core-file load.

Index: gdb/gdb/solib-svr4.c
===================================================================
--- gdb.orig/gdb/solib-svr4.c
+++ gdb/gdb/solib-svr4.c
@@ -1310,6 +1310,7 @@ static int
 svr4_read_so_list (CORE_ADDR lm, CORE_ADDR prev_lm,
 		   struct so_list ***link_ptr_ptr, int ignore_first)
 {
+  struct so_list *first = NULL;
   CORE_ADDR next_lm;
 
   for (; lm != 0; prev_lm = lm, lm = next_lm)
@@ -1349,6 +1350,7 @@ svr4_read_so_list (CORE_ADDR lm, CORE_AD
 	{
 	  struct svr4_info *info = get_svr4_info ();
 
+	  first = new;
 	  info->main_lm_addr = new->lm_info->lm_addr;
 	  do_cleanups (old_chain);
 	  continue;
@@ -1359,8 +1361,14 @@ svr4_read_so_list (CORE_ADDR lm, CORE_AD
 			  SO_NAME_MAX_PATH_SIZE - 1, &errcode);
       if (errcode != 0)
 	{
-	  warning (_("Can't read pathname for load map: %s."),
-		   safe_strerror (errcode));
+	  /* If this entry's l_name address matches that of the
+	     inferior executable, then this is not a normal shared
+	     object, but (most likely) a vDSO.  In this case, silently
+	     skip it; otherwise emit a warning. */
+	  if (first == NULL
+	      || new->lm_info->l_name != first->lm_info->l_name)
+	    warning (_("Can't read pathname for load map: %s."),
+		     safe_strerror (errcode));
 	  do_cleanups (old_chain);
 	  continue;
 	}
Index: gdb/gdb/testsuite/gdb.base/corefile.exp
===================================================================
--- gdb.orig/gdb/testsuite/gdb.base/corefile.exp
+++ gdb/gdb/testsuite/gdb.base/corefile.exp
@@ -255,3 +255,19 @@ if ![is_remote target] {
 
     gdb_exit
 }
+
+# Test warning-free core file load.  E.g., a Linux vDSO used to
+# trigger this warning:
+#     warning: Can't read pathname for load map: Input/output error.
+
+clean_restart ${testfile}
+
+set test "core-file warning-free"
+gdb_test_multiple "core-file $corefile" $test {
+    -re "warning: .*\r\n.*\r\n$gdb_prompt $" {
+	fail $test
+    }
+    -re "\r\n$gdb_prompt $" {
+	pass $test
+    }
+}