How to produce effective backtraces from crashdump?

Hi, everyone,

I'm encounting a very strange problem when trying to obtain backtraces
from a recently compiled kernel (see attachments for my dmesg.boot,
kernel configuration, and /etc/make.conf).

To make the long story short, here's my rough situation: I have built
a customized kernel with makeoptions DEBUG=-g, and no special options
in /etc/make.conf. When system is restarted after a panic, and when
I open it with:

gdb -k /usr/obj/usr/src/sys/BEASTIE/kernel.debug /var/crash/vmcore.0

then have a "bt full" I got something like this:

(kgdb) bt full
#0  doadump () at /usr/src/sys/kern/kern_shutdown.c:236
No locals.
#1  0xc04f63ae in ?? ()
No symbol table info available.
#2  0xc04f672a in ?? ()
No symbol table info available.
#3  0xc04ec693 in ?? ()
No symbol table info available.
#4  0xc04ec1ee in ?? ()
No symbol table info available.
#5  0xc0544b85 in ?? ()
No symbol table info available.
#6  0xc053fe80 in ?? ()
No symbol table info available.
#7  0xc053faf5 in ?? ()
No symbol table info available.
#8  0xc0541d5b in ?? ()
No symbol table info available.
#9  0xc0549b08 in ?? ()
No symbol table info available.
#10 0xc04c21de in ?? ()
No symbol table info available.
#11 0xc04c1428 in ?? ()
No symbol table info available.
#12 0xc05da95a in ?? ()
No symbol table info available.
#13 0xc0554b5d in ?? ()
No symbol table info available.
#14 0xc04f5ed6 in ?? ()
No symbol table info available.
#15 0xc04f672a in ?? ()
No symbol table info available.
#16 0xc05fbecf in ?? ()
No symbol table info available.
#17 0xc05fb1ad in ?? ()
No symbol table info available.
#18 0xc05f9ddb in ?? ()
No symbol table info available.
#19 0xc05f9fa0 in ?? ()
No symbol table info available.
#20 0xc05f82f3 in ?? ()
No symbol table info available.
#21 0xc05f45e7 in ?? ()
No symbol table info available.
#22 0xc05f4816 in ?? ()
No symbol table info available.
#23 0xc05f488a in ?? ()
No symbol table info available.
#24 0xc04de130 in ?? ()
No symbol table info available.
#25 0xc04cedd0 in ?? ()
No symbol table info available.
#26 0xc04dd0ed in ?? ()
No symbol table info available.
#27 0xc04dcd30 in ?? ()
No symbol table info available.
#28 0xc0637602 in ?? ()
No symbol table info available.
#29 0xc0624d0d in ?? ()
No symbol table info available.
---Can't read userspace from dump, or kernel process---

as we can see, the backtrace won't be valuable for debugging :-(

Full details are in the attachments. Any idea? If you need more
information please feel free to contact me.

Thanks in advance!

Cheers,
-- 
Xin LI <delphij frontfree net>	http://www.delphij.net/
See complete headers for GPG key and other information.