[Crash-utility] [PATCH] output regs if sp is in user stack

[Dave Anderson]

----- Original Message -----
> We have sadump, and it can work when the OS is out of controll(
> for example: dead loop, dead lock). When we use sadump, some
> user application may be running, and the sp/ip is in user stack.
> 
> We should deal with it like kvm dump.

The patch appears reasonable, with two minor exceptions.

This stanza is incorrect, because it restricts both "bt -t" and "bt -T":

@@ -2761,6 +2846,8 @@ x86_64_low_budget_back_trace_cmd(struct bt_info *bt_in)
                ofp = fp;

         if (bt->flags & BT_TEXT_SYMBOLS) {
+               if (bt->flags & BT_USER_SPACE)
+                       return;
                if (!(bt->flags & BT_TEXT_SYMBOLS_ALL))
                        fprintf(ofp, "%sSTART: %s%s at %lx\n",
                            space(VADDR_PRLEN > 8 ? 14 : 6),

There's no reason to restrict "bt -T", because it's certainly possible
that a user may want to examine the kernel stack contents as they were
during the most recent entry into kernel-space:

       -T  display all text symbols found from just above the task_struct or
           thread_info to the top of the stack. (helpful if the back trace
           fails or the -t option starts too high in the process stack).

So I'll change it like this:

@@ -2761,6 +2846,9 @@
                ofp = fp;
 
         if (bt->flags & BT_TEXT_SYMBOLS) {
+               if ((bt->flags & BT_USER_SPACE) &&
+                   !(bt->flags & BT_TEXT_SYMBOLS_ALL))
+                       return;
                if (!(bt->flags & BT_TEXT_SYMBOLS_ALL))
                        fprintf(ofp, "%sSTART: %s%s at %lx\n",
                            space(VADDR_PRLEN > 8 ? 14 : 6),

Also, you forgot to update dump_offset_table() in symbols.c
with all of the new user_regs_struct_xxx values for use
by "help -o".

I'll update dump_offset_table(), so you can consider the remainder
of the patch queued for the next release.

Thanks,
  Dave