linux-kernel - Re: perf: fuzzer leads to trace_kprobe: Could not insert message flood

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Message-ID: <A3B3905F-3364-462A-BE02-B01D52482791@fb.com>
Date:   Tue, 10 Apr 2018 19:57:50 +0000
From:   Song Liu <songliubraving@...com>
To:     Vince Weaver <vincent.weaver@...ne.edu>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "mingo@...nel.org" <mingo@...nel.org>
Subject: Re: perf: fuzzer leads to trace_kprobe: Could not insert message
 flood



> On Apr 10, 2018, at 7:48 AM, Vince Weaver <vincent.weaver@...ne.edu> wrote:
> 
> Author: Song Liu <songliubraving@...com>
> Date:   Wed Dec 6 14:45:15 2017 -0800
> 
> When running the perf_fuzzer on a current git checkout my logs are flooded 
> with messages such as this:
> [71487.869077] trace_kprobe: Could not insert probe at unknown+0: -22
> [71488.174479] trace_kprobe: Could not insert probe at unknown+0: -22
> 
> Presumably this is due to the introduction of the perf_kprobe PMU in
> 	commit e12f03d7031a977356e3d7b75a68c2185ff8d155
> 	Author: Song Liu <songliubraving@...com>
> 	Date:   Wed Dec 6 14:45:15 2017 -0800
> 
> Is there a way to get this error disabled, or else rate-limited?
> 
> Vince

Hi Vince, 

Thanks for the report. 

This is a new API that creates probe together with perf_event_open(). Based on 
my limited understanding of perf_fuzzer, it doesn't understand this API, and uses 
it in an abnormal way. I would recommend perf_fuzzer to understand this new
API and test it. For more information about using this API, please refer to the 
man-page diff available at:

      https://patchwork.kernel.org/patch/10097283/

Thanks again for the test and report. Please let me know if you have further 
questions. 

Best, 
Song