Re: Troubles analyzing crash dumps from xl dump-core

[Jürgen Groß <jgross@xxxxxxxx>]

On 10.03.21 20:37, Igor Druzhinin wrote:
> > On 30.01.21 19:53, Roman Shaposhnik wrote:
> > > On Fri, Jan 29, 2021 at 11:28 PM Jürgen Groß <jgross@xxxxxxxx> wrote:
> > > > On 29.01.21 21:12, Roman Shaposhnik wrote:
> > > > > Hi!
> > > > >
> > > > > I'm trying to see how much mileage I can get out of
> > > > > crash(1) 7.2.8 (based on gdb 7.6) when it comes to analyzing crash
> > > > > dumps taken via xl dump-core (this is all on x86_64 with stock Xen
> > > > > v. 4.14).
> > > > >
> > > > > The good news is that the image actually does load up but it throws
> > > > > the following WARNINGs in the process:
> > > > >
> > > > > WARNING: cannot access vmalloc'd module memory
> > > > > crash: read error: kernel virtual address: ffffffff93613480  type:
> > > > > "fill_task_struct"
> > > > > WARNING: active task ffffffff93613480 on cpu 0 not found in PID hash
> > > > > crash: read error: kernel virtual address: ffffffff93613480  type:
> > > > > "fill_task_struct"
> > > > > WARNING: cannot read log_buf contents
> > > > >
> > > > > And then the info that it gives me around basic things like ps, mod,
> > > > > log, etc. is really super limited (and I am now suspecting may even
> > > > > be wrong).
> > > > >
> > > > > Since I was primarily after dmesg/log initially, I tried:
> > > > > crash> log
> > > > > log: WARNING: cannot read log_buf contents
> > > > >
> > > > > Then I tried taking an xl dump-core from the domU that was still
> > > > > very much alive and happy and got similar results -- so it clearly
> > > > > doesn't seem to be related to the state domU is in.
> > > > >
> > > > > As matter of fact, I actually got to the desired dmesg output by
> > > > > simply running strings(1) on the core file -- so the info is
> > > > > definitely there -- but I guess some kind of index/reference maybe
> > > > > broken.
> > > > >
> > > > > With all that in mind, if there's anyone on this ML who has recently
> > > > > done Xen DomU crash dump analysis -- I would definitely appreciate
> > > > > the pointers!
> > > > For me it just works (openSUSE).
> > > Can you please run:
> > >
> > > crash --version and readelf -a XXXX (on the xl dump-core output) and
> > > post the results?
> > # crash --version
> >
> > crash 7.2.1
> I tried to build this version but I still get the following while trying to 
> open a dump file
> produced by "xl dump-core":
>
> [root@lcy2-dt92 crash]# ./crash ../vmlinux-5.8.0-44-generic ../xxx.dmp
>
> crash 7.2.1
> Copyright (C) 2002-2017  Red Hat, Inc.
> Copyright (C) 2004, 2005, 2006, 2010  IBM Corporation
> Copyright (C) 1999-2006  Hewlett-Packard Co
> Copyright (C) 2005, 2006, 2011, 2012  Fujitsu Limited
> Copyright (C) 2006, 2007  VA Linux Systems Japan K.K.
> Copyright (C) 2005, 2011  NEC Corporation
> Copyright (C) 1999, 2002, 2007  Silicon Graphics, Inc.
> Copyright (C) 1999, 2000, 2001, 2002  Mission Critical Linux, Inc.
> This program is free software, covered by the GNU General Public License,
> and you are welcome to change it and/or distribute copies of it under
> certain conditions.  Enter "help copying" to see the conditions.
> This program has absolutely no warranty.  Enter "help warranty" for details.
>
> GNU gdb (GDB) 7.6
> Copyright (C) 2013 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-unknown-linux-gnu"...
>
> crash: cannot determine base kernel version
> crash: ../vmlinux-5.8.0-44-generic and ../xxx.dmp do not match!
>
>
> Am I doing something wrong? How do I need to use crash for it to work?
Could you try the attached patch?


Juergen

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