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

Leo Yan
2020-08-31T00:07:13Z

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@arm.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@arm.com>
> > Reviewed-by: Andrea Brunato <andrea.brunato@arm.com>
> > Signed-off-by: Leo Yan <leo.yan@linaro.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