linux-kernel - Re: [PATCH 1/2] perf cs-etm: Fix corrupt data after perf inject from

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Message-ID: <20200831000432.GA4715@leoy-ThinkPad-X240s>
Date:   Mon, 31 Aug 2020 08:04:32 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Al Grant <al.grant@....com>
Subject: Re: [PATCH 1/2] perf cs-etm: Fix corrupt data after perf inject from

Hi Mathieu,

On Thu, Aug 27, 2020 at 02:53:54PM -0600, Mathieu Poirier wrote:
> Hi Leo and Al,
> 
> On Wed, Aug 19, 2020 at 04:47:50PM +0800, Leo Yan wrote:
> > From: Al Grant <al.grant@....com>
> > 
> > Commit 42bbabed09ce ("perf tools: Add hw_idx in struct branch_stack")
> > changed the format of branch stacks in perf samples. When samples use
> > this new format, a flag must be set in the corresponding event.
> > Synthesized branch stacks generated from CoreSight ETM trace were using
> > the new format, but not setting the event attribute, leading to
> > consumers seeing corrupt data. This patch fixes the issue by setting the
> > event attribute to indicate use of the new format.
> > 
> > Fixes: 42bbabed09ce ("perf tools: Add hw_idx in struct branch_stack")
> > Signed-off-by: Al Grant <al.grant@....com>
> > Reviewed-by: Andrea Brunato <andrea.brunato@....com>
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > ---
> >  tools/perf/util/cs-etm.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> > index c283223fb31f..a2a369e2fbb6 100644
> > --- a/tools/perf/util/cs-etm.c
> > +++ b/tools/perf/util/cs-etm.c
> > @@ -1344,8 +1344,15 @@ static int cs_etm__synth_events(struct cs_etm_auxtrace *etm,
> >  		attr.sample_type &= ~(u64)PERF_SAMPLE_ADDR;
> >  	}
> >  
> > -	if (etm->synth_opts.last_branch)
> > +	if (etm->synth_opts.last_branch) {
> >  		attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
> > +		/*
> > +		 * We don't use the hardware index, but the sample generation
> > +		 * code uses the new format branch_stack with this field,
> > +		 * so the event attributes must indicate that it's present.
> > +		 */
> > +		attr.branch_sample_type |= PERF_SAMPLE_BRANCH_HW_INDEX;
> > +	}
> 
> I've see this patch before...  I thought it had been merged - what happened?

This patch before has been sent by Al to CoreSight mailing list but has
not sent to LKML, this is why I resent it to LKML in case it's missed.

Thanks,
Leo