bin/48915: Kernels saved by savecore are not usable with gdb

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         48915
>Category:       bin
>Synopsis:       Kernels saved by savecore are not usable with gdb
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 16 12:40:00 +0000 2014
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date 2014.06.16.09.55.49
>Organization:

>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

The kernel files saved in /var/crash by savecore are not usable with
gdb.  Attempting to get a stack trace from a kernel core dump using
the saved kernel only results in:

  (gdb) where
  #0  <unavailable> in ?? ()
  Backtrace stopped: not enough registers or memory available to unwind further

If gdb is run against /netbsd rather than /var/crash/netbsd.N,
you do get a stack trace.

>How-To-Repeat:

  (drop into ddb)
  db{0}> reboot 0x100
  (wait for reboot, log in as root)
  # cd /var/crash
  # gunzip *.gz
  (assuming netbsd.0.core is the newest one, adjust as needed)
  # gdb netbsd.0
  # target kvm netbsd.0.core
  # where

>Fix: