[v2,06/12] perf record: 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. Ensure adding the BPF filter forces
system-wide.

Signed-off-by: Ian Rogers <[e-mail]>
---
 tools/perf/builtin-record.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

Patch

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ba20bf7c011d..202c917fd122 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -173,6 +173,7 @@  struct record {
 	bool			timestamp_boundary;
 	bool			off_cpu;
 	const char		*filter_action;
+	const char		*uid_str;
 	struct switch_output	switch_output;
 	unsigned long long	samples;
 	unsigned long		output_max_size;	/* = 0: unlimited */
@@ -3460,8 +3461,7 @@  static struct option __record_options[] = {
 		     "or ranges of time to enable events e.g. '-D 10-20,30-40'",
 		     record__parse_event_enable_time),
 	OPT_BOOLEAN(0, "kcore", &record.opts.kcore, "copy /proc/kcore"),
-	OPT_STRING('u', "uid", &record.opts.target.uid_str, "user",
-		   "user to profile"),
+	OPT_STRING('u', "uid", &record.uid_str, "user", "user to profile"),
 
 	OPT_CALLBACK_NOOPT('b', "branch-any", &record.opts.branch_stack,
 		     "branch any", "sample any taken branches",
@@ -4196,19 +4196,24 @@  int cmd_record(int argc, const char **argv)
 		ui__warning("%s\n", errbuf);
 	}
 
-	err = target__parse_uid(&rec->opts.target);
-	if (err) {
-		int saved_errno = errno;
+	if (rec->uid_str) {
+		uid_t uid = parse_uid(rec->uid_str);
 
-		target__strerror(&rec->opts.target, err, errbuf, BUFSIZ);
-		ui__error("%s", errbuf);
+		if (uid == UINT_MAX) {
+			ui__error("Invalid User: %s", rec->uid_str);
+			err = -EINVAL;
+			goto out;
+		}
+		err = parse_uid_filter(rec->evlist, uid);
+		if (err)
+			goto out;
 
-		err = -saved_errno;
-		goto out;
+		/* User ID filtering implies system wide. */
+		rec->opts.target.system_wide = true;
 	}
 
-	/* Enable ignoring missing threads when -u/-p option is defined. */
-	rec->opts.ignore_missing_thread = rec->opts.target.uid != UINT_MAX || rec->opts.target.pid;
+	/* Enable ignoring missing threads when -p option is defined. */
+	rec->opts.ignore_missing_thread = rec->opts.target.pid;
 
 	evlist__warn_user_requested_cpus(rec->evlist, rec->opts.target.cpu_list);