Capturing dmesg upon system crash on 6.3
fbsd.questions at rachie.is-a-geek.net
Mon Feb 25 13:37:03 UTC 2008
On Monday 25 February 2008 13:32:01 Yehonatan Yossef wrote:
> > > I'm facing a system reboot upon loading of the driver, and
> > I could use
> > > a tool for capturing dmesg upon system crash (such as netconsole on
> > > Linux).
> > Your kernel isn't setup for driver development:
> > http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-ha
> > ndbook/kerneldebug.html
> > http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kern
> > elconfig.html
> > Basically, your system is rebooting cause the kernel panics
> > and you're not setup for crash dumps, or anything that could
> > help you diagnose the panic.
> > --
> > Mel
> I've setup the dumpdev/dumpdir and I get a vmcore image upon a crash.
> I don't really understand how to use kgdb in order to read it but more
> than that - I don't need that much of data. I only want the dmesg report
> at the moment, see at what point my driver went crazy. Is it possible?
Uhm, no. Fundamental logic flaw: when a kernel is stopped, you can't issue
userland commands. All you have when you use ddb, is the contents of the
registers, ram and backtrace.
You really want ddb in the kernel: when a kernel panics, it'll drop to ddb and
you can examine registers and do a backtrace, instead of dumping core and
rebooting. It should point exactly to where your driver went crazy.
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