linux-kernel - [PATCH 2/6] perf offcpu: Accept allowed sample types only

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Date:   Fri, 24 Jun 2022 16:13:09 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        linux-perf-users@...r.kernel.org, Song Liu <songliubraving@...com>,
        Hao Luo <haoluo@...gle.com>,
        Milian Wolff <milian.wolff@...b.com>, bpf@...r.kernel.org,
        Blake Jones <blakejones@...gle.com>
Subject: [PATCH 2/6] perf offcpu: Accept allowed sample types only

As offcpu-time event is synthesized at the end, it could not get the
all the sample info.  Define OFFCPU_SAMPLE_TYPES for allowed ones and
mask out others in evsel__config() to prevent parse errors.

Because perf sample parsing assumes a specific ordering with the
sample types, setting unsupported one would make it fail to read
data like perf record -d/--data.

Fixes: edc41a1099c2 ("perf record: Enable off-cpu analysis with BPF")
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/bpf_off_cpu.c | 7 ++++++-
 tools/perf/util/evsel.c       | 9 +++++++++
 tools/perf/util/off_cpu.h     | 9 +++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c
index b73e84a02264..f289b7713598 100644
--- a/tools/perf/util/bpf_off_cpu.c
+++ b/tools/perf/util/bpf_off_cpu.c
@@ -265,6 +265,12 @@ int off_cpu_write(struct perf_session *session)
 
 	sample_type = evsel->core.attr.sample_type;
 
+	if (sample_type & ~OFFCPU_SAMPLE_TYPES) {
+		pr_err("not supported sample type: %llx\n",
+		       (unsigned long long)sample_type);
+		return -1;
+	}
+
 	if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER)) {
 		if (evsel->core.id)
 			sid = evsel->core.id[0];
@@ -319,7 +325,6 @@ int off_cpu_write(struct perf_session *session)
 		}
 		if (sample_type & PERF_SAMPLE_CGROUP)
 			data.array[n++] = key.cgroup_id;
-		/* TODO: handle more sample types */
 
 		size = n * sizeof(u64);
 		data.hdr.size = size;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index ce499c5da8d7..094b0a9c0bc0 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -48,6 +48,7 @@
 #include "util.h"
 #include "hashmap.h"
 #include "pmu-hybrid.h"
+#include "off_cpu.h"
 #include "../perf-sys.h"
 #include "util/parse-branch-options.h"
 #include <internal/xyarray.h>
@@ -1102,6 +1103,11 @@ static void evsel__set_default_freq_period(struct record_opts *opts,
 	}
 }
 
+static bool evsel__is_offcpu_event(struct evsel *evsel)
+{
+	return evsel__is_bpf_output(evsel) && !strcmp(evsel->name, OFFCPU_EVENT);
+}
+
 /*
  * The enable_on_exec/disabled value strategy:
  *
@@ -1366,6 +1372,9 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
 	 */
 	if (evsel__is_dummy_event(evsel))
 		evsel__reset_sample_bit(evsel, BRANCH_STACK);
+
+	if (evsel__is_offcpu_event(evsel))
+		evsel->core.attr.sample_type &= OFFCPU_SAMPLE_TYPES;
 }
 
 int evsel__set_filter(struct evsel *evsel, const char *filter)
diff --git a/tools/perf/util/off_cpu.h b/tools/perf/util/off_cpu.h
index 548008f74d42..2dd67c60f211 100644
--- a/tools/perf/util/off_cpu.h
+++ b/tools/perf/util/off_cpu.h
@@ -1,6 +1,8 @@
 #ifndef PERF_UTIL_OFF_CPU_H
 #define PERF_UTIL_OFF_CPU_H
 
+#include <linux/perf_event.h>
+
 struct evlist;
 struct target;
 struct perf_session;
@@ -8,6 +10,13 @@ struct record_opts;
 
 #define OFFCPU_EVENT  "offcpu-time"
 
+#define OFFCPU_SAMPLE_TYPES  (PERF_SAMPLE_IDENTIFIER | PERF_SAMPLE_IP | \
+			      PERF_SAMPLE_TID | PERF_SAMPLE_TIME | \
+			      PERF_SAMPLE_ID | PERF_SAMPLE_CPU | \
+			      PERF_SAMPLE_PERIOD | PERF_SAMPLE_CALLCHAIN | \
+			      PERF_SAMPLE_CGROUP)
+
+
 #ifdef HAVE_BPF_SKEL
 int off_cpu_prepare(struct evlist *evlist, struct target *target,
 		    struct record_opts *opts);
-- 
2.37.0.rc0.161.g10f37bed90-goog