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Re: [Xen-devel] [PATCH] Add xentrace/xen_crash.
On 10/15/13 11:47, Ian Campbell wrote:
On Tue, 2013-10-15 at 11:25 -0400, Don Slutz wrote:
Is this some protocol defined by crash? Can you include a reference to
their specification somewhere please. Is it intended for consumption
externally to the crash tools -- i.e. is it a stable protocol? (it
smells a bit ad-hoc is why I'm asking).
So far I have not found a specification. Will keep looking. I had
assumed it was, will work with the crash tools person to see.
Thanks.
If it's not intended to be consumed like this perhaps the tool would be
better off living in the crash source base?
Maybe. Since this has code that needs the XEN headers and crash is
currently one program with extension modules, it does not fit as well there.
I had it in my mind that crash already had some level of Xen support and
therefore already dependended on the headers. I don't know why I think
that so it may be a fantasy.
Crash does have support for XEN crash dumps. I do not think it
supports live access to the hypervisor (crash live on dom0 allows
you to look at dom0, not the hypervisor). Most of the data
structures are fetched out of the debug info in ELF files. So to
build crash, xen does not need to be installed.
For example:
dcs-xen-50:~/dump2>crash vmcore
xenrpm/boot/xen-syms-4.2.2
crash 6.1.4
Copyright (C) 2002-2013Â Red Hat, Inc.
Copyright (C) 2004, 2005, 2006, 2010Â IBM Corporation
Copyright (C) 1999-2006Â Hewlett-Packard Co
Copyright (C) 2005, 2006, 2011, 2012Â Fujitsu Limited
Copyright (C) 2006, 2007Â VA Linux Systems Japan K.K.
Copyright (C) 2005, 2011Â NEC Corporation
Copyright (C) 1999, 2002, 2007Â Silicon Graphics, Inc.
Copyright (C) 1999, 2000, 2001, 2002Â 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.
Â
GNU gdb (GDB) 7.3.1
Copyright (C) 2011 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.Â
Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu"...
ÂÂ KERNEL: xenrpm/boot/xen-syms-4.2.2
ÂDUMPFILE: vmcore
ÂÂÂÂ CPUS: 8
 DOMAINS: 5
ÂÂ UPTIME: --:--:--
 MACHINE: Intel(R) Xeon(R) CPU E31265L @ 2.40GHz (2400
Mhz)
ÂÂ MEMORY: 32 GB
 PCPU-ID: 0
ÂÂÂÂ PCPU: ffff82c4802bff18
 VCPU-ID: 0
ÂÂÂÂ VCPU: ffff8300bf2fa000Â (VCPU_RUNNING)
DOMAIN-ID: 0
ÂÂ DOMAIN: ffff830823fb6000Â (DOMAIN_RUNNING)
ÂÂÂ STATE: CRASH
crash> quit
Don't these extension modules have all sorts of random dependencies? In
which case adding the Xen ones doesn't seem too horrible, assuming they
are smart enough to only enable the ones whose dependencies are
available.
I think that they do, but not sure. The ones I have looked at are
ways to process the data in a dump in a more easy way for a user to
use.
Since this is changing the way that crash gets to the data, I know
of no way to do it as an extension module.
Ian.
 -Don Slutz
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