linux-kernel - Re: [PATCH -tip 10/10] perf probe: Accessing members in data structures

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: <4BA12A23.4030109@redhat.com>
Date:	Wed, 17 Mar 2010 15:14:43 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Mark Wielaard <mjw@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH -tip 10/10] perf probe: Accessing members in data structures

Mark Wielaard wrote:
> On Tue, 2010-03-16 at 18:06 -0400, Masami Hiramatsu wrote:
>> Support accessing members in the data structures. With this,
>> perf-probe accepts data-structure members(IOW, it now accepts
>> dot '.' and arrow '->' operators) as probe arguemnts.
>>
>> e.g.
>>
>>  ./perf probe --add 'schedule:44 rq->curr'
>>
>>  ./perf probe --add 'vfs_read file->f_op->read file->f_path.dentry'
>>
>> Note that '>' can be interpreted as redirection in command-line.
> 
> If you find that a problem then you can do like SystemTap does and allow
> '.' in place of '->'. In the code you already use the
> perf_probe_arg_field ref flag only to check that the DIE gives you the
> same information. So you could just drop that and use any separator.
> Then you decide based on whether you see a DW_TAG_pointer_type. This
> gives the user some extra flexibility by letting them not having to care
> about specifying extra type information already available elsewhere.

Thanks, when designing this feature, I considered it too.

Since perf probe already support displaying source code by --line option,
users will read the probed code itself and try to probe it. In that case,
I think they naturally use '.' and '->' as they read (they might try to
copy & paste it).

So, I think that it would be good to support both of '.' and '->' as
they are used in the code, because it will not confuse users.

Thank you,

-- 
Masami Hiramatsu
e-mail: mhiramat@...hat.com
--
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/