linux-kernel - Re: [PATCH -tip perf/probes 00/10] x86 insn decoder bugfixes

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Message-ID: <4AE9F6BF.8000501@redhat.com>
Date:	Thu, 29 Oct 2009 16:10:39 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frédéric Weisbecker 
	<fweisbec@...il.com>, lkml <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jim Keniston <jkenisto@...ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jason Baron <jbaron@...hat.com>,
	"K.Prasad" <prasad@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>
Subject: Re: [PATCH -tip perf/probes 00/10] x86 insn decoder bugfixes

Masami Hiramatsu wrote:
> Ingo Molnar wrote:
>> Another problem i noticed is that a vmlinux without DEBUG_INFO will fail
>> in this way:
>>
>>    aldebaran:~/linux/linux>   perf probe schedule
>>      Fatal: Failed to call dwarf_init(). Maybe, not a dwarf file.
>
> Ah, really? I think I broke need_dwarf logic somehow...

Hmm, I've found that is for searching (implicitly) inlined symbols,
this means "the behavior is by (bad) design" :-(

I think it should be search the symbol in Elf (or kallsyms) first,
and only if it fails, use Dwarf for searching the symbol again.

Or, it may be enough that just trying to setup probe and if it fails
use Dwarf. This way doesn't require any vmlinux access.

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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