linux-kernel - [PATCH 9/9] perf bpf filter: Show warning for missing sample flags

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Message-Id: <20230307233309.3546160-10-namhyung@kernel.org>
Date:   Tue,  7 Mar 2023 15:33:09 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Song Liu <song@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Leo Yan <leo.yan@...aro.org>,
        James Clark <james.clark@....com>, Hao Luo <haoluo@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH 9/9] perf bpf filter: Show warning for missing sample flags

For a BPF filter to work properly, users need to provide appropriate
options to enable the sample types.  Otherwise the BPF program would
see an invalid value (i.e. always 0) and filter won't work well.

Show a warning message if sample types are missing like below.

  $ sudo ./perf record -e cycles --filter 'addr < 100' true
  Error: cycles event does not have PERF_SAMPLE_ADDR
   Hint: please add -d option to perf record.
  failed to set filter "BPF" on event cycles with 22 (Invalid argument)

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/builtin-record.c  |  2 +-
 tools/perf/util/bpf-filter.c | 62 ++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 197e802a150b..3e9de6ad64fd 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1353,7 +1353,7 @@ static int record__open(struct record *rec)
 
 	if (evlist__apply_filters(evlist, &pos)) {
 		pr_err("failed to set filter \"%s\" on event %s with %d (%s)\n",
-			pos->filter, evsel__name(pos), errno,
+			pos->filter ?: "BPF", evsel__name(pos), errno,
 			str_error_r(errno, msg, sizeof(msg)));
 		rc = -1;
 		goto out;
diff --git a/tools/perf/util/bpf-filter.c b/tools/perf/util/bpf-filter.c
index bd638737e12f..0b30688d78a7 100644
--- a/tools/perf/util/bpf-filter.c
+++ b/tools/perf/util/bpf-filter.c
@@ -17,6 +17,64 @@
 
 #define FD(e, x, y) (*(int *)xyarray__entry(e->core.fd, x, y))
 
+#define __PERF_SAMPLE_TYPE(st, opt)	{ st, #st, opt }
+#define PERF_SAMPLE_TYPE(_st, opt)	__PERF_SAMPLE_TYPE(PERF_SAMPLE_##_st, opt)
+
+static const struct perf_sample_info {
+	u64 type;
+	const char *name;
+	const char *option;
+} sample_table[] = {
+	/* default sample flags */
+	PERF_SAMPLE_TYPE(IP, NULL),
+	PERF_SAMPLE_TYPE(TID, NULL),
+	PERF_SAMPLE_TYPE(PERIOD, NULL),
+	/* flags mostly set by default, but still have options */
+	PERF_SAMPLE_TYPE(ID, "--sample-identifier"),
+	PERF_SAMPLE_TYPE(CPU, "--sample-cpu"),
+	PERF_SAMPLE_TYPE(TIME, "-T"),
+	/* optional sample flags */
+	PERF_SAMPLE_TYPE(ADDR, "-d"),
+	PERF_SAMPLE_TYPE(DATA_SRC, "-d"),
+	PERF_SAMPLE_TYPE(PHYS_ADDR, "--phys-data"),
+	PERF_SAMPLE_TYPE(WEIGHT, "-W"),
+	PERF_SAMPLE_TYPE(WEIGHT_STRUCT, "-W"),
+	PERF_SAMPLE_TYPE(TRANSACTION, "--transaction"),
+	PERF_SAMPLE_TYPE(CODE_PAGE_SIZE, "--code-page-size"),
+	PERF_SAMPLE_TYPE(DATA_PAGE_SIZE, "--data-page-size"),
+};
+
+static const struct perf_sample_info *get_sample_info(u64 flags)
+{
+	size_t i;
+
+	for (i = 0; i < ARRAY_SIZE(sample_table); i++) {
+		if (sample_table[i].type == flags)
+			return &sample_table[i];
+	}
+	return NULL;
+}
+
+static int check_sample_flags(struct evsel *evsel, struct perf_bpf_filter_expr *expr)
+{
+	const struct perf_sample_info *info;
+
+	if (evsel->core.attr.sample_type & expr->sample_flags)
+		return 0;
+
+	info = get_sample_info(expr->sample_flags);
+	if (info == NULL) {
+		pr_err("Error: %s event does not have sample flags %lx\n",
+		       evsel__name(evsel), expr->sample_flags);
+		return -1;
+	}
+
+	pr_err("Error: %s event does not have %s\n", evsel__name(evsel), info->name);
+	if (info->option)
+		pr_err(" Hint: please add %s option to perf record\n", info->option);
+	return -1;
+}
+
 int perf_bpf_filter__prepare(struct evsel *evsel)
 {
 	int i, x, y, fd;
@@ -40,6 +98,10 @@ int perf_bpf_filter__prepare(struct evsel *evsel)
 			.flags = expr->sample_flags,
 			.value = expr->val,
 		};
+
+		if (check_sample_flags(evsel, expr) < 0)
+			return -1;
+
 		bpf_map_update_elem(fd, &i, &entry, BPF_ANY);
 		i++;
 
-- 
2.40.0.rc1.284.g88254d51c5-goog