linux-kernel - [patch v3] perf tools: perf list broken on ARM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.10.1312141516120.15216@vincent-weaver-1.um.maine.edu>
Date:	Sat, 14 Dec 2013 15:25:18 -0500 (EST)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Namhyung Kim <namhyung@...nel.org>
cc:	linux-kernel@...r.kernel.org,
	Chad Paradis <chad.paradis@...t.maine.edu>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>
Subject: [patch v3] perf tools: perf list broken on ARM


OK, here's an updated version that reuses evsel and hopefully doesn't leak 
memory like the previous patch I posted.


"perf list" listing of hardware events doesn't work on older ARM devices.
The change enabling event detection:

 commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b
 Author: Namhyung Kim <namhyung.kim@....com>
 Date:   Tue Aug 27 11:41:53 2013 +0900

     perf list: Skip unsupported events


uses the following code in tools/perf/util/parse-events.c:

        struct perf_event_attr attr = {
                .type = type,
                .config = config,
                .disabled = 1,
                .exclude_kernel = 1,
        };

On ARM machines pre-dating the Cortex-A15 this doesn't work, as
these machines don't support .exclude_kernel.  So starting with 3.12
"perf list" does not report any hardware events at all on older
machines (seen on Rasp-Pi, Pandaboard, Beagleboard, etc).

This version of the patch makes changes suggested by Namhyung Kim
to check for EACCESS and retry (instead of just dropping
the exclude_kernel) so we can properly handle machines where 
/proc/sys/kernel/perf_event_paranoid is set to 2.

Reported-by: Chad Paradis <chad.paradis@...t.maine.edu>
Signed-off-by: Vince Weaver <vincent.weaver@...ne.edu>

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 6de6f89..1fa98b9 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1082,12 +1082,12 @@ int is_valid_tracepoint(const char *event_string)
 static bool is_event_supported(u8 type, unsigned config)
 {
 	bool ret = true;
+	int open_return;
 	struct perf_evsel *evsel;
 	struct perf_event_attr attr = {
 		.type = type,
 		.config = config,
 		.disabled = 1,
-		.exclude_kernel = 1,
 	};
 	struct {
 		struct thread_map map;
@@ -1099,7 +1099,20 @@ static bool is_event_supported(u8 type, unsigned config)
 
 	evsel = perf_evsel__new(&attr);
 	if (evsel) {
-		ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0;
+		open_return = perf_evsel__open(evsel, NULL, &tmap.map);
+		ret = open_return >= 0;
+
+		if (open_return == -EACCES) {
+			/*
+			 * This happens if the paranoid value
+			 * /proc/sys/kernel/perf_event_paranoid is set to 2
+			 * Re-run with exclude_kernel set; we don't do that
+			 * by default as some ARM machines do not support it.
+			 *
+			 */
+			evsel->attr.exclude_kernel = 1;
+			ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0;
+		}
 		perf_evsel__delete(evsel);
 	}
 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/