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Message-ID: <53CF6121.3050500@intel.com>
Date: Wed, 23 Jul 2014 10:15:45 +0300
From: Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
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To: Peter Zijlstra <peterz@infradead.org>
CC: Arnaldo Carvalho de Melo <acme@kernel.org>, linux-kernel@vger.kernel.org,
        David Ahern <dsahern@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@gmail.com>, Paul Mackerras <paulus@samba.org>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 01/52] perf tools: Fix jump label always changing during
 tracing
References: <1406035081-14301-1-git-send-email-adrian.hunter@intel.com> <1406035081-14301-2-git-send-email-adrian.hunter@intel.com> <20140722140034.GE20303@kernel.org> <20140722141135.GF3935@laptop> <53CF5124.2090901@intel.com> <20140723065822.GN3935@laptop>
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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.