[PATCH] Add option to control checking of inner frames when doing a backtrace

Joshua Watt jpewdev@gmail.com
Tue Oct 2 17:58:00 GMT 2012


Please note: this is the first patch I have ever submitted for GDB, so
please let
me know if there are any problems. -- Joshua Watt


This patch allows the user to turn off the checking for inner frames
when performing
a backtrace using the command:

set backtrace check-inner off

This is useful if a thread is switching execution to run on another
stack, as this will
often cause the inner frame condition to fail.

diff -U 5 -Nar gdb-7.5.50.20121002-orig/gdb/frame.c
gdb-7.5.50.20121002/gdb/frame.c
--- gdb-7.5.50.20121002-orig/gdb/frame.c 2012-09-17 02:15:48 -0500
+++ gdb-7.5.50.20121002/gdb/frame.c 2012-10-02 12:25:47 -0500
@@ -205,10 +205,20 @@
     _("An upper bound on the number "
       "of backtrace levels is %s.\n"),
     value);
 }

+static unsigned int backtrace_check_inner = TRUE;
+static void
+show_backtrace_check_inner (struct ui_file *file, int from_tty,
+   struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Whether backtraces should check for inner "
+    "frames is %s.\n"),
+    value);
+}
+

 static void
 fprint_field (struct ui_file *file, const char *name, int p, CORE_ADDR addr)
 {
   if (p)
@@ -1670,11 +1680,12 @@

   /* Check that this frame's ID isn't inner to (younger, below, next)
      the next frame.  This happens when a frame unwind goes backwards.
      This check is valid only if this frame and the next frame are NORMAL.
      See the comment at frame_id_inner for details.  */
-  if (get_frame_type (this_frame) == NORMAL_FRAME
+  if (backtrace_check_inner
+      && get_frame_type (this_frame) == NORMAL_FRAME
       && this_frame->next->unwind->type == NORMAL_FRAME
       && frame_id_inner (get_frame_arch (this_frame->next), this_id,
  get_frame_id (this_frame->next)))
     {
       CORE_ADDR this_pc_in_block;
@@ -2504,10 +2515,25 @@
     NULL,
     show_backtrace_limit,
     &set_backtrace_cmdlist,
     &show_backtrace_cmdlist);

+  add_setshow_boolean_cmd ("check-inner", class_obscure,
+   &backtrace_check_inner, _("\
+Sets whether backtraces will check if a frame is inner to the previous frame"),
+   _("\
+Shows whether backtraces will check if a frame is inner to the
previous frame"),
+   _("\
+Normally frames are laid out in a specific order on the stack.  This
controls\n\
+whether GDB will validate that the frames are in the correct order.  Frames\n\
+can commonly be out of order if a thread switches to a different
stack during\n\
+execution"),
+   NULL,
+   show_backtrace_check_inner,
+   &set_backtrace_cmdlist,
+   &show_backtrace_cmdlist);
+
   /* Debug this files internals.  */
   add_setshow_zuinteger_cmd ("frame", class_maintenance, &frame_debug,  _("\
 Set frame debugging."), _("\
 Show frame debugging."), _("\
 When non-zero, frame specific internal debugging is enabled."),



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