Commit bf1976dd authored by Ian Rogers's avatar Ian Rogers Committed by Namhyung Kim
Browse files

perf trace: Switch user option to use BPF filter 



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: default avatarIan Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250604174545.2853620-8-irogers@google.com


Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
parent 38f83cc9

tools/perf/builtin-trace.c

+17 −9
Original line number Diff line number Diff line
@@ -236,6 +236,7 @@ struct trace { 
		struct ordered_events	data;

		u64			last;

	} oe;

	const char		*uid_str;

};



static void trace__load_vmlinux_btf(struct trace *trace __maybe_unused)
@@ -4412,8 +4413,8 @@ static int trace__run(struct trace *trace, int argc, const char **argv) 
		evlist__add(evlist, pgfault_min);

	}



	/* Enable ignoring missing threads when -u/-p option is defined. */

	trace->opts.ignore_missing_thread = trace->opts.target.uid != UINT_MAX || trace->opts.target.pid;

	/* Enable ignoring missing threads when -p option is defined. */

	trace->opts.ignore_missing_thread = trace->opts.target.pid;



	if (trace->sched &&

	    evlist__add_newtp(evlist, "sched", "sched_stat_runtime", trace__sched_stat_runtime))
@@ -5445,8 +5446,7 @@ int cmd_trace(int argc, const char **argv) 
		    "child tasks do not inherit counters"),

	OPT_CALLBACK('m', "mmap-pages", &trace.opts.mmap_pages, "pages",

		     "number of mmap data pages", evlist__parse_mmap_pages),

	OPT_STRING('u', "uid", &trace.opts.target.uid_str, "user",

		   "user to profile"),

	OPT_STRING('u', "uid", &trace.uid_str, "user", "user to profile"),

	OPT_CALLBACK(0, "duration", &trace, "float",

		     "show only events with duration > N.M ms",

		     trace__set_duration),
@@ -5804,12 +5804,20 @@ int cmd_trace(int argc, const char **argv) 
		goto out_close;

	}



	err = target__parse_uid(&trace.opts.target);

	if (err) {

		target__strerror(&trace.opts.target, err, bf, sizeof(bf));

		fprintf(trace.output, "%s", bf);

	if (trace.uid_str) {

		uid_t uid = parse_uid(trace.uid_str);



		if (uid == UINT_MAX) {

			ui__error("Invalid User: %s", trace.uid_str);

			err = -EINVAL;

			goto out_close;

		}

		err = parse_uid_filter(trace.evlist, uid);

		if (err)

			goto out_close;



		trace.opts.target.system_wide = true;

	}



	if (!argc && target__none(&trace.opts.target))

		trace.opts.target.system_wide = true;