How to produce effective backtraces from crashdump?

Dan Nelson dnelson at
Fri Apr 9 07:27:26 PDT 2004

In the last episode (Apr 09), Xin LI said:
> 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.

I can't help you with your symbol problem, but if you add the DDB_TRACE
option to your kernel config, the kernel will print a simple backtrace
(function names and arguments) on panic, which is sometimes enough info
to track down the problem.

	Dan Nelson
	dnelson at

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