linux-kernel - Re: [PATCH 01/52] perf tools: Fix jump label always changing during tracing

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Message-ID: <53CF6121.3050500@intel.com>
Date:	Wed, 23 Jul 2014 10:15:45 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 01/52] perf tools: Fix jump label always changing during
 tracing

On 07/23/2014 09:58 AM, Peter Zijlstra wrote:
> On Wed, Jul 23, 2014 at 09:07:32AM +0300, Adrian Hunter wrote:
>> On 07/22/2014 05:11 PM, Peter Zijlstra wrote:
>>> On Tue, Jul 22, 2014 at 11:00:34AM -0300, Arnaldo Carvalho de Melo wrote:
>>>> Em Tue, Jul 22, 2014 at 04:17:10PM +0300, Adrian Hunter escreveu:
>>>>> Intel PT decoding walks the object code to reconstruct
>>>>> the trace.  A jump label change during tracing causes
>>>>> decoding errors.
>>>
>>> You'd better fix that, jump_labels can change any time and they're all
>>> over the frigging place.
>>>
>>
>> Perhaps a general method is needed to be able to deal with kernel
>> self-modifying code.
> 
> I know people are looking at doing the same to userspace, is that also a
> problem?

Yes, most significantly JIT-compiled code.

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