Kernel debugging, 5.4-RELEASE

[dpk]

On Tue, 2 Aug 2005, dpk wrote:

> On Tue, 2 Aug 2005, Mitch Parks wrote:
>
> > man kgdb
> > http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-gdb.html
>
> Thank you. I'm using kgdb now, and I get the following error:
>
> $ kgdb -r /dev/cuaa0 kernel.debug
> [GDB will not be able to debug user-mode threads:
> /usr/lib/libthread_db.so: Undefined symbol "ps_pglobal_lookup"]
> GNU gdb 6.1.1 [FreeBSD]
> Copyright 2004 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you
> are
> welcome to change it and/or distribute copies of it under certain
> conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for
> details.
> This GDB was configured as "i386-marcel-freebsd".
> Switching to remote protocol
> 0xc035646c in kdb_enter ()
> Segmentation fault
>
> The two servers (the panic one and the one running kgdb) are identical,
> except the one running kgdb is not using PAE. The kernel.debug file is
> identical to the remote server however.

If I run it without arguments, and then enter "file kernel.debug" and
"target remote /dev/cuaa0" it does not crash. However, when the remote
server is set to use the GDB backend, all that comes up is:

0x00000000 in ?? ()

bt and others do nothing to help determine the problem.

If I boot the machine with "boot -d", and attach then, hit "continue" and
let it run until it panics, I get this:

Program received signal SIGTRAP, Trace/breakpoint trap.
[Switching to PID 100127 TID     0]
0x00000000 in ?? ()
(kgdb)

Seems I can't extract anything useful from that prompt, either.

Is there anything else I can try, to get some debugging information? The
steps outlined in the handbook don't seem to be working. I've been at this
for a couple days, so I apologize if I am curt, I'm just trying to get a
useful backtrace to submit as a PR.