Linux kernel panics and core dumps.

[Wright, David]

I looked at the SGI project, but it wasn't suitable for our
platform, as we didn't have the right sort of disk setup.

I ported the MCLX code to a 405-based platform.  The code as
originally distributed had a few bugs in it, but I don't think
they ever fixed the bugs -- I fed changes back to them, and those
changes may have made it to IBM.  Or at least they told me IBM
was interested in the project.

If you do use their code, ignore the program that uncompresses
the crash dumps -- as implemented, it's incredibly slow, and
although that can be fixed, it's pointless, since crash can read
the compressed dumps just fine (and can't read the uncompressed
ones, just as a final irony).

I don't have a complete list of the changes I needed to make, but
here are a few:

Makefile didn't specify compiling crash.c
crash.c (machine-specific) specified "regs" instead of "gprs"; also
  specified tss.ksp instead of thread.ksp; also must #define
  PFN_PHYS() itself.
The code in do_init_bootmem() is trying to work in bytes, not in
  frames.

Anyway, once I got these various problems ironed out, plus a few
in crash(1), the facility worked fine.  The main problem you're
apt to run into is having enough physical memory to run your
system, hold the dump, and copy the dump from RAM into some file.
NFS can be very useful here.

The dump facility did prove to be quite useful and we did use it
on live systems to track down problems.  One thing to watch out
for is diags that scrub memory, since they'll scrub out your dump,
too.

  -- David Wright, InfiniSwitch Corp.


> -----Original Message-----
> From: Arun Dharankar [mailto:ADharankar at attbi.com]
> Sent: Tuesday, April 08, 2003 11:58 AM
> To: linuxppc-embedded at lists.linuxppc.org
> Subject: Linux kernel panics and core dumps.
>
>
>
> Greetings.
>
> On x86 architectures there seem to be at least two ways of
> producing  Linux kernel panic dumps. These projects are
> hosted at
>
>     "http://lkcd.sourceforge.net/" (originated in SGI), and
>
>     "http://oss.missioncriticallinux.com/projects/mcore/"
>         (originated in MCLX).
>
>
> Of the two, the second one seems to work quite well on x86
> PCs. I dont know how much of it is actively supported on
> PowerPCs. So, the first question is:
>
>     Has anyone tried this on PowerPC, specifically Linux
>     kernel versions 2.4.x? The code for PowerPC seems to
>     be there, but the Makefiles dont seem to be up-to-date,
>     and could be broken.
>
> Further more, this same project has some documentation
> which has a good discussion on different approaches to Linux
> kernel memory dumps. One item in this discussion is about
> the BIOS/bootloader support.
>
>
> Essentially, if PPCBoot/U-Boot was to recognize the Linux
> kernel memory layout, a much more reliable scheme could
> be implemented. For example, under all panic or hang
> conditions (watchdog), the system could just be rebooted.
> During the startup, PPCBoot/U-Boot along with Linux, could
> save the Linux kernel dump reliably. MCLX scheme seems
> to follow this approach, but does not rely on the bootloader.
>
>   Has anyone investigated this? Or anything already done,
>   and cares to share it? Any thoughts on this?
>
>
> Best regards,
> -Arun.
>


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