linux-kernel - Re: [PATCH v3 01/28] perf auxtrace: Remove dummy tools

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Message-ID: <CAP-5=fX+VG3HsAPb=3DzEp2bUyAUvHk7f1zAhq3r=FKYaJPW6Q@mail.gmail.com>
Date: Thu, 11 Jul 2024 09:08:31 -0700
From: Ian Rogers <irogers@...gle.com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Kan Liang <kan.liang@...ux.intel.com>, John Garry <john.g.garry@...cle.com>, 
	Will Deacon <will@...nel.org>, James Clark <james.clark@....com>, 
	Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...ux.dev>, 
	Suzuki K Poulose <suzuki.poulose@....com>, Yicong Yang <yangyicong@...ilicon.com>, 
	Jonathan Cameron <jonathan.cameron@...wei.com>, Nick Terrell <terrelln@...com>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	Anshuman Khandual <anshuman.khandual@....com>, Song Liu <song@...nel.org>, 
	Ilkka Koskinen <ilkka@...amperecomputing.com>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, 
	Huacai Chen <chenhuacai@...nel.org>, Yanteng Si <siyanteng@...ngson.cn>, 
	Sun Haiyong <sunhaiyong@...ngson.cn>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 01/28] perf auxtrace: Remove dummy tools

On Wed, Jul 10, 2024 at 11:46 PM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> On 11/07/24 09:43, Adrian Hunter wrote:
> > On 29/06/24 07:53, Ian Rogers wrote:
> >> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> >> index 0ec92d47373c..44db5b49128f 100644
> >> --- a/tools/perf/util/session.c
> >> +++ b/tools/perf/util/session.c
> >> @@ -1764,6 +1764,36 @@ int perf_session__deliver_synth_event(struct perf_session *session,
> >>      return machines__deliver_event(&session->machines, evlist, event, sample, tool, 0, NULL);
> >>  }
> >>
> >> +int perf_session__deliver_synth_attr_event(struct perf_session *session,
> >> +                                       const struct perf_event_attr *attr,
> >> +                                       u64 id)
> >> +{
> >> +    union {
> >> +            struct {
> >> +                    struct perf_record_header_attr attr;
> >> +                    u64 ids[1];
> >> +            } attr_id;
> >> +            union perf_event ev;
> >> +    } ev = {
> >> +            .attr_id = {
> >> +                    .attr = {
> >> +                            .header = {
> >> +                                    .type = PERF_RECORD_HEADER_ATTR,
> >> +                                    .size = PERF_ALIGN(sizeof(struct perf_event_attr),
> >> +                                                       sizeof(u64))
> >> +                                        + sizeof(struct perf_event_header)
> >> +                                        + sizeof(u64),
> >> +                            },
> >> +                    },
> >> +                    .ids = { id, }
> >> +            },
> >
> > Nested definitions are not needed.  It can just be:
> >
> >               .attr_id.attr.header.type = PERF_RECORD_HEADER_ATTR,
> >               .attr_id.attr.header.size = sizeof(ev.attr_id),
> >               .attr_id.ids[0] = id,
> >
> >> +    };
> >> +
> >> +    memcpy(&ev.attr_id.attr.attr, attr, min((u32)sizeof(struct perf_event_attr), attr->size));
> >
> > It is not unreasonable to validate attr->size, but neither slicing
> > nor padding will work.  Better to just return an error:
> >
> >       if (attr->size != sizeof(ev.attr_id.attr))
>
> Or rather
>
>         if (attr->size != sizeof(ev.attr_id.attr.attr))

Thanks, I'll change this in v4. The struct perf_event_attr are
internal to the tool, so it shouldn't be possible for the size to
deviate.

Ian

> >               return -EINVAL;
> >
> > Then:
> >
> >       ev.attr_id.attr.attr = *attr;
> >
> >
> >> +    ev.attr_id.attr.attr.size = sizeof(struct perf_event_attr);
> >> +    return perf_session__deliver_synth_event(session, &ev.ev, NULL);
> >> +}
> >> +
>