Analyzing a Xen core dump

Question

After a Xen guest domain hang, I took a dump using xm core-dump . Following the sparse documentation I found, I tried using the crash utility to analyze the dump.

Unfortunately, the kernel image (Debian lenny) is stripped, so I am forced to make use of the map file.

However,

crash /boot/System.map-2.6.26-2-xen-amd64 vmlinux-2.6.26-2-xen-amd64 /mnt/my-core-file

(with vmlinux-2.6.26-2-xen-amd64 being the gunzip'ed vmlinuz image) fails:

crash: vmlinux-2.6.26-2-xen-amd64: no debugging data available

Then I read that current Xen versions produce ELF-compatible dumps for guest domains. Indeed, this seems to be the case:

~$ sudo file my-core-dump

my-core-dump: ELF 64-bit LSB core file x86-64, version 1

However, gdb vmlinux-2.6.26-2-xen-amd64 my-core-dump fails, too:

...is not a core dump: File format not recognized

Any hints?

Answer 1

Have you tried attaching to the domU console ?

xm create domU.conf -c

On the subject of the core-dump file, I found this:

http://lists.xensource.com/archives/html/xen-devel/2006-12/msg00456.html

I just want to check that you aren't under the impression that 'xm dump-core' emits an Elf core file. It doesn't -- the format is custom and as far as I know is only interpreted by a set of gdbserver patches that we ship in our repository. Does the crash utility really support this special format?

Edit: This might help to debug the core-dump: http://os-drive.com/files/docbook/xen-faq.html#setup%5Fgdb