Re: Using crash to debug a domU on xen.

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 10/16/13 09:09, Dave Anderson wrote:

----- Original Message -----

I have some code that allows this. See the following mail thread:

http://permalink.gmane.org/gmane.comp.emulators.xen.devel/174807

The questions are:


    1. Does remote access have a specification?

If you're talking about the remote.c file in the crash sources, no,
there's nothing other than the remote.c file itself.  

Ok, looks like I will need to write something up.

    2. Is it supported?

It's been deprecated for almost 10 years now.  I don't understand how
you have been able to even get it to build, never mind work as the mail
thread indicates?

crash is still building remote.c in 7.0.2-0 and still accepts the command line option:

don-760:~/rpmbuild/BUILD/crash-7.0.2>./crash -d99 localhost:5001

crash 7.0.2
Copyright (C) 2002-2013  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.
 
server: [localhost]
  port: [5001]
 file1: [(null)]
 file2: [(null)]
127.0.0.1
don-760.cloudswitch.com: Unknown host

crash: connect [don-760.cloudswitch.com:5001] failed

don-760:~/rpmbuild/BUILD/crash-7.0.2>

  But I don't know anything about xen_crash, xentrace,
or how it even interacts with the crash utility?  It looks like it might
replace the old "crashd" daemon that was built as part of the old remote
access facility?

Yes, that is the case. My guess is that using crashd was more pain the help.  However the big plus in the case is that the guest (domU) is paused while crash is running and so can be seen more like a dump and not a active system.  I have found that crash has some issues between active, remote, and dump modes; but most of them are speed related or start-up like guessing the kernel version.

    3. Should the code be part of xen or crash?

I don't know.  Xen support is no longer something I'm actively involved
with since Red Hat dropped support for it.  Since then, Xen support in 
the crash utility has primarily come from Daniel Kiper from Oracle and 
Petr Tesarik from SUSE.  They are both on the list, and should see this
message, but I'll cc them in this response as well. 

Thanks,
  Dave
 

I think david.vrabel@xxxxxxxxxx is also involved now (adding to CC list).
    -Don Slutz

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