[v2,10/12] perf bench evlist-open-close: Switch user option to use BPF filter

Commit Message

Ian Rogers April 10, 2025, 5:36 p.m. UTC

Finding user processes by scanning /proc is inherently racy and
results in perf_event_open failures. Use a BPF filter to drop samples
where the uid doesn't match.

Signed-off-by: Ian Rogers <[e-mail]>
---
 tools/perf/bench/evlist-open-close.c | 36 ++++++++++++++++------------
 1 file changed, 21 insertions(+), 15 deletions(-)

Patch

diff --git a/tools/perf/bench/evlist-open-close.c b/tools/perf/bench/evlist-open-close.c
index 79cedcf94a39..bfaf50e4e519 100644
--- a/tools/perf/bench/evlist-open-close.c
+++ b/tools/perf/bench/evlist-open-close.c
@@ -57,7 +57,7 @@  static int evlist__count_evsel_fds(struct evlist *evlist)
 	return cnt;
 }
 
-static struct evlist *bench__create_evlist(char *evstr)
+static struct evlist *bench__create_evlist(char *evstr, const char *uid_str)
 {
 	struct parse_events_error err;
 	struct evlist *evlist = evlist__new();
@@ -78,6 +78,18 @@  static struct evlist *bench__create_evlist(char *evstr)
 		goto out_delete_evlist;
 	}
 	parse_events_error__exit(&err);
+	if (uid_str) {
+		uid_t uid = parse_uid(uid_str);
+
+		if (uid == UINT_MAX) {
+			pr_err("Invalid User: %s", uid_str);
+			ret = -EINVAL;
+			goto out_delete_evlist;
+		}
+		ret = parse_uid_filter(evlist, uid);
+		if (ret)
+			goto out_delete_evlist;
+	}
 	ret = evlist__create_maps(evlist, &opts.target);
 	if (ret < 0) {
 		pr_err("Not enough memory to create thread/cpu maps\n");
@@ -117,10 +129,10 @@  static int bench__do_evlist_open_close(struct evlist *evlist)
 	return 0;
 }
 
-static int bench_evlist_open_close__run(char *evstr)
+static int bench_evlist_open_close__run(char *evstr, const char *uid_str)
 {
 	// used to print statistics only
-	struct evlist *evlist = bench__create_evlist(evstr);
+	struct evlist *evlist = bench__create_evlist(evstr, uid_str);
 	double time_average, time_stddev;
 	struct timeval start, end, diff;
 	struct stats time_stats;
@@ -142,7 +154,7 @@  static int bench_evlist_open_close__run(char *evstr)
 
 	for (i = 0; i < iterations; i++) {
 		pr_debug("Started iteration %d\n", i);
-		evlist = bench__create_evlist(evstr);
+		evlist = bench__create_evlist(evstr, uid_str);
 		if (!evlist)
 			return -ENOMEM;
 
@@ -206,6 +218,7 @@  static char *bench__repeat_event_string(const char *evstr, int n)
 
 int bench_evlist_open_close(int argc, const char **argv)
 {
+	const char *uid_str = NULL;
 	const struct option options[] = {
 		OPT_STRING('e', "event", &event_string, "event",
 			   "event selector. use 'perf list' to list available events"),
@@ -221,7 +234,7 @@  int bench_evlist_open_close(int argc, const char **argv)
 			   "record events on existing process id"),
 		OPT_STRING('t', "tid", &opts.target.tid, "tid",
 			   "record events on existing thread id"),
-		OPT_STRING('u', "uid", &opts.target.uid_str, "user", "user to profile"),
+		OPT_STRING('u', "uid", &uid_str, "user", "user to profile"),
 		OPT_BOOLEAN(0, "per-thread", &opts.target.per_thread, "use per-thread mmaps"),
 		OPT_END()
 	};
@@ -245,15 +258,8 @@  int bench_evlist_open_close(int argc, const char **argv)
 		goto out;
 	}
 
-	err = target__parse_uid(&opts.target);
-	if (err) {
-		target__strerror(&opts.target, err, errbuf, sizeof(errbuf));
-		pr_err("%s", errbuf);
-		goto out;
-	}
-
-	/* Enable ignoring missing threads when -u/-p option is defined. */
-	opts.ignore_missing_thread = opts.target.uid != UINT_MAX || opts.target.pid;
+	/* Enable ignoring missing threads when -p option is defined. */
+	opts.ignore_missing_thread = opts.target.pid;
 
 	evstr = bench__repeat_event_string(event_string, nr_events);
 	if (!evstr) {
@@ -261,7 +267,7 @@  int bench_evlist_open_close(int argc, const char **argv)
 		goto out;
 	}
 
-	err = bench_evlist_open_close__run(evstr);
+	err = bench_evlist_open_close__run(evstr, uid_str);
 
 	free(evstr);
 out: