linux-kernel - Re: [RFC] Unify KVM kernel-space and user-space code into a single project

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100324182705.GF3625@ghostprotocols.net>
Date:	Wed, 24 Mar 2010 15:27:05 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Joerg Roedel <joro@...tes.org>,
	Anthony Liguori <anthony@...emonkey.ws>,
	Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sheng Yang <sheng@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Jes Sorensen <Jes.Sorensen@...hat.com>,
	Gleb Natapov <gleb@...hat.com>, ziteng.huang@...el.com,
	Fr?d?ric Weisbecker <fweisbec@...il.com>,
	Gregory Haskins <ghaskins@...ell.com>
Subject: Re: [RFC] Unify KVM kernel-space and user-space code into a single
	project

Em Wed, Mar 24, 2010 at 08:20:10PM +0200, Avi Kivity escreveu:
> On 03/24/2010 07:47 PM, Arnaldo Carvalho de Melo wrote:
>> Em Wed, Mar 24, 2010 at 06:09:30PM +0200, Avi Kivity escreveu:
>>    
>>> Doesn't perf already has a dependency on naming conventions for finding
>>> debug information?
>>>      
>> It looks at several places, from most symbol rich (/usr/lib/debug/, aka
>> -debuginfo packages, where we have full symtabs) to poorest (the
>> packaged binary, where we may just have a .dynsym).
>>
>> In an ideal world, it would just get the build-id (a SHA1 cookie that is
>> in an ELF session inserted in every binary (aka DSOs), kernel module,
>> kallsyms or vmlinux file) and use that to look first in a local cache
>> (implemented in perf for a long time already) or in some symbol server.
>>
>> For instance, for a random perf.data file I collected here in my machine
>> I have:
>>
>> [acme@...pio linux-2.6-tip]$ perf buildid-list | grep libpthread
>> 5c68f7afeb33309c78037e374b0deee84dd441f6 /lib64/libpthread-2.10.2.so
>> [acme@...pio linux-2.6-tip]$
>>
>> So I don't have to access /lib64/libpthread-2.10.2.so directly, nor some
>> convention to get a debuginfo in a local file like:
>>
>> /usr/lib/debug/lib64/libpthread-2.10.2.so.debug
>>
>> Instead the tools look at:
>>
>> [acme@...pio linux-2.6-tip]$ l ~/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6
>> lrwxrwxrwx 1 acme acme 73 2010-01-06 18:53 /home/acme/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6 ->  ../../lib64/libpthread-2.10.2.so/5c68f7afeb33309c78037e374b0deee84dd441f6*
>>
>> To find the file for that specific build-id, not the one installed in my
>> machine (or on the different machine, of a different architecture) that
>> may be completely unrelated, a new one, or one for a different arch.

> Thanks.  I believe qemu could easily act as a symbol server for this use  
> case.

Agreed, but it doesn't even have to :-)

We just need to get the build-id in the PERF_RECORD_MMAP event somehow
and then get this symbol from elsewhere, say the same DVD/RHN
channel/Debian Repository/embedded developer toolkit image not
stripped/whatever.

Or it may already be in the local cache from last week's perf report
session :-)

- Arnaldo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/