kernel panic, problems getting backtrace from saved core

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

About two weeks ago I had a kernel panic.

Sep 15 00:49:31 yt savecore: warning: /dev/ksyms version mismatch:      NetBSD 
6.99.11 (YT) #23: Tue Sep 11 23:23:01 CEST 2012  
wiz%yt.nih.at@localhost:/archive/cvs/src/sys/arch/amd64/compile/obj/YT  and     
  C 
Sep 15 00:49:31 yt savecore: reboot after panic: .tn_readdir_lastp == NULL || 
tmpfs_dircookie((node)->tn_spAecN.ItNnG_:d iSrP.Lt nN_rOeTa dLdOiWrE_RlEaDs 
OtNp )S Y=S=C A(LnLo de)-1>0t6n _4s pEeXcI.Tt n_d1i8rf.t0n _r6e addir_lastn" 
failed: file "/archive/cvs/src/sys/fs/tmpfs/tmpfs.h", line 357  cpu6: Begin 
traceback... WARNING: SPL NOT LOWERE
Sep 15 00:49:31 yt savecore: system went down at Fri Sep 14 13:26:33 2012 
Sep 15 00:49:32 yt savecore: writing compressed core to 
/var/crash/netbsd.1.core.gz

Today I wanted to look at the backtrace, but couldn't.
# gzcat /var/crash/netbsd.1.core.gz > core
# gzcat /var/crash/netbsd.1.gz > kernel
# ls -l
total 12577920
-rw-rw-r--  1 wiz  wheel  12875588120 Oct  3 22:12 core
-rw-r--r--  1 wiz  wheel       961748 Oct  3 22:12 kernel
# gdb /netbsd.6.99.11b
GNU gdb (GDB) 7.3.1
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64--netbsd".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /netbsd.6.99.11b...(no debugging symbols found)...done.
(gdb) target kvm core
#0  0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x0000000000000000 in ?? ()
(gdb) quit
# gdb  kernel
GNU gdb (GDB) 7.3.1
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64--netbsd".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /path/to/kernel...(no debugging symbols found)...done.
(gdb) target kvm core
#0  <unavailable> in ?? ()
(gdb) bt
#0  <unavailable> in ?? ()
Backtrace stopped: Not enough registers or memory available to unwind further
(gdb) quit

Suggestions?
 Thomas