linux-kernel - [PATCH v2 09/12] perf trace: Switch user option to use BPF filter

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Message-ID: <20250410173631.1713627-10-irogers@google.com>
Date: Thu, 10 Apr 2025 10:36:28 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>, Thomas Richter <tmricht@...ux.ibm.com>, 
	Veronika Molnarova <vmolnaro@...hat.com>, Hao Ge <gehao@...inos.cn>, 
	Howard Chu <howardchu95@...il.com>, Weilin Wang <weilin.wang@...el.com>, 
	Levi Yun <yeoreum.yun@....com>, "Dr. David Alan Gilbert" <linux@...blig.org>, 
	Dominique Martinet <asmadeus@...ewreck.org>, Xu Yang <xu.yang_2@....com>, 
	Tengda Wu <wutengda@...weicloud.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH v2 09/12] 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: Ian Rogers <irogers@...gle.com>
---
 tools/perf/builtin-trace.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 6ac51925ea42..1f7d2b3d8b3d 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -240,6 +240,7 @@ struct trace {
 		struct ordered_events	data;
 		u64			last;
 	} oe;
+	const char		*uid_str;
 };
 
 static void trace__load_vmlinux_btf(struct trace *trace __maybe_unused)
@@ -4401,8 +4402,8 @@ 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))
@@ -5420,8 +5421,7 @@ 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),
@@ -5762,11 +5762,19 @@ 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);
-		goto out_close;
+	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))
-- 
2.49.0.604.gff1f9ca942-goog