Bug#622570: linux-image-2.6.38-2-s390x: Unable to handle kernel pointer dereference at virtual kernel address (null).

[Jonathan Nieder <jrnieder@gmail.com>]

Hi Stephen,

Stephen Powell wrote:

> I installed linux-image-2.6.38-2-s390x version 2.6.38-3 on my up-to-date Wheezy
> system today.  It runs in a virtual machine under z/VM 5.4.0 running in an LPAR
> on an IBM z/890.  It IPLed just fine.  After the IPL, the system fell idle for a while.
> Then a CRON job kicked off, which caused a page fault, which caused a kernel oops.
> Here is the log:

Thanks.  If you find time, could you try the latest (or close to the
latest) upstream version, following the instructions from here?

 http://kernel-handbook.alioth.debian.org/ch-common-tasks.html#s-kernel-org-package

(Short version:

 $ (umask 077 && mkdir workspace)
 $ cd workspace
 $ wget http://www.kernel.org/pub/linux/kernel/v2.6/testing/linux-2.6.39-rc3.tar.bz2
 $ tar -xf linux-2.6.39-rc3.tar.bz2
 $ cd linux-*
 $ make localmodconfig
 $ make deb-pkg
 $ cd ..
 # dpkg -i *.deb

)

If that version fails, too, the best thing would be to bisect.  It
works like so:

 # apt-get install git
 $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
 $ cd linux-2.6
 $ git bisect start -- arch/s390 mm
 $ git bisect bad v2.6.39-rc3
 $ git bisect good v2.6.32
 $ make localmodconfig
 $ make deb-pkg
 ... try it out, and ...
 $ git bisect good;	# if it has the null pointer dereference
 $ git bisect bad;	# if it doesn't
 $ git bisect skip;	# if some other problem makes it hard to test
 $ make deb-pkg
 ... repeat as many times as wanted ...

This can help quite a lot, to figure out what change or family of
changes introduced a bug.

Thanks again and hope that helps.
Jonathan