linux-kernel - [PATCH 29/32] perf header: Fix handling of PERF_EVENT_UPDATE_

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Date:   Thu,  9 Feb 2017 22:39:37 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
        Kan Liang <kan.liang@...el.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [PATCH 29/32] perf header: Fix handling of PERF_EVENT_UPDATE__SCALE

From: Arnaldo Carvalho de Melo <acme@...hat.com>

In commit daeecbc0c431 ("perf tools: Add event_update event scale type"), the
handling of PERF_EVENT_UPDATE__SCALE cast struct event_update_event->data to a
pointer to event_update_event_scale, uses some field from this casted struct
and then ends up falling through to the handling of another event type,
PERF_EVENT_UPDATE__CPUS were it casts that ev->data to yet another type, oops,
fix it by inserting the missing break.

Noticed when building perf using gcc 7 on Fedora Rawhide:

  util/header.c: In function 'perf_event__process_event_update':
  util/header.c:3207:16: error: this statement may fall through [-Werror=implicit-fallthrough=]
     evsel->scale = ev_scale->scale;
     ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
  util/header.c:3208:2: note: here
    case PERF_EVENT_UPDATE__CPUS:
    ^~~~

This wasn't noticed because probably PERF_EVENT_UPDATE__CPUS comes after
PERF_EVENT_UPDATE__SCALE, so we would just create a bogus evsel->own_cpus when
processing a PERF_EVENT_UPDATE__SCALE to then leak it and create a new cpu map
with the correct data.

Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Kan Liang <kan.liang@...el.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Fixes: daeecbc0c431 ("perf tools: Add event_update event scale type")
Link: http://lkml.kernel.org/n/tip-lukcf9hdj092ax2914ss95at@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/header.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c567d9f0aa92..3d12c16e5103 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3205,6 +3205,7 @@ int perf_event__process_event_update(struct perf_tool *tool __maybe_unused,
 	case PERF_EVENT_UPDATE__SCALE:
 		ev_scale = (struct event_update_event_scale *) ev->data;
 		evsel->scale = ev_scale->scale;
+		break;
 	case PERF_EVENT_UPDATE__CPUS:
 		ev_cpus = (struct event_update_event_cpus *) ev->data;
 
-- 
2.9.3