linux-kernel - [PATCH v1 06/10] perf top: Switch user option to use BPF filter

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Message-Id: <20250111190143.1029906-7-irogers@google.com>
Date: Sat, 11 Jan 2025 11:01:39 -0800
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>, Hao Ge <gehao@...inos.cn>, 
	James Clark <james.clark@...aro.org>, Howard Chu <howardchu95@...il.com>, 
	Dominique Martinet <asmadeus@...ewreck.org>, Levi Yun <yeoreum.yun@....com>, 
	Xu Yang <xu.yang_2@....com>, Tengda Wu <wutengda@...weicloud.com>, 
	Yang Jihong <yangjihong1@...wei.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 06/10] perf top: 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.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/builtin-top.c | 22 ++++++++++++----------
 tools/perf/util/top.c    |  4 ++--
 tools/perf/util/top.h    |  1 +
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index ca3e8eca6610..f6d837be185b 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -642,7 +642,7 @@ static void *display_thread_tui(void *arg)
 	 */
 	evlist__for_each_entry(top->evlist, pos) {
 		struct hists *hists = evsel__hists(pos);
-		hists->uid_filter_str = top->record_opts.target.uid_str;
+		hists->uid_filter_str = top->uid_str;
 	}
 
 	ret = evlist__tui_browse_hists(top->evlist, help, &hbt, top->min_percent,
@@ -1562,7 +1562,7 @@ int cmd_top(int argc, const char **argv)
 		    "Add prefix to source file path names in programs (with --prefix-strip)"),
 	OPT_STRING(0, "prefix-strip", &annotate_opts.prefix_strip, "N",
 		    "Strip first N entries of source file path name in programs (with --prefix)"),
-	OPT_STRING('u', "uid", &target->uid_str, "user", "user to profile"),
+	OPT_STRING('u', "uid", &top.uid_str, "user", "user to profile"),
 	OPT_CALLBACK(0, "percent-limit", &top, "percent",
 		     "Don't show entries under that percent", parse_percent_limit),
 	OPT_CALLBACK(0, "percentage", NULL, "relative|absolute",
@@ -1753,15 +1753,17 @@ int cmd_top(int argc, const char **argv)
 		ui__warning("%s\n", errbuf);
 	}
 
-	status = target__parse_uid(target);
-	if (status) {
-		int saved_errno = errno;
-
-		target__strerror(target, status, errbuf, BUFSIZ);
-		ui__error("%s\n", errbuf);
+	if (top.uid_str) {
+		uid_t uid = parse_uid(top.uid_str);
 
-		status = -saved_errno;
-		goto out_delete_evlist;
+		if (uid == UINT_MAX) {
+			ui__error("Invalid User: %s", top.uid_str);
+			status = -EINVAL;
+			goto out_delete_evlist;
+		}
+		status = parse_uid_filter(top.evlist, uid);
+		if (status)
+			goto out_delete_evlist;
 	}
 
 	if (target__none(target))
diff --git a/tools/perf/util/top.c b/tools/perf/util/top.c
index 4db3d1bd686c..b06e10a116bb 100644
--- a/tools/perf/util/top.c
+++ b/tools/perf/util/top.c
@@ -88,9 +88,9 @@ size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)
 	else if (target->tid)
 		ret += SNPRINTF(bf + ret, size - ret, " (target_tid: %s",
 				target->tid);
-	else if (target->uid_str != NULL)
+	else if (top->uid_str != NULL)
 		ret += SNPRINTF(bf + ret, size - ret, " (uid: %s",
-				target->uid_str);
+				top->uid_str);
 	else
 		ret += SNPRINTF(bf + ret, size - ret, " (all");
 
diff --git a/tools/perf/util/top.h b/tools/perf/util/top.h
index 4c5588dbb131..04ff926846be 100644
--- a/tools/perf/util/top.h
+++ b/tools/perf/util/top.h
@@ -48,6 +48,7 @@ struct perf_top {
 	const char	   *sym_filter;
 	float		   min_percent;
 	unsigned int	   nr_threads_synthesize;
+	const char	   *uid_str;
 
 	struct {
 		struct ordered_events	*in;
-- 
2.47.1.613.gc27f4b7a9f-goog