Capturing dmesg upon system crash on 6.3

[Yehonatan Yossef]

> 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.
> --
> Mel
> 

I meant making the dmesg log sent over the network/serial console to a
linux machine. I just found out about syslogd, I'm trying to figure out
how to use it.
DDB sounds like a great option for deeper debugging, I'll use it.

Yony