[PATCH 09/10] perf bpf filter: Show warning for missing sample flags

[Namhyung Kim]

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@xxxxxxxxxx>
---
 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 6df8b823859d..7b7e74a56346 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