linux-kernel - [PATCH 2/2] perf/probe: Report permission error for tracefs error

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Date:   Sat,  5 Jun 2021 00:31:08 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
        aneesh.kumar@...ux.ibm.com, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 2/2] perf/probe: Report permission error for tracefs error

Report permission error for the tracefs access error.
This can happen when non-superuser runs perf probe.
With this patch, perf probe shows the following message.

  $ perf probe -l
  No permission to access tracefs. Please run this command again with sudo.
    Error: Failed to show event list.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 tools/perf/util/probe-file.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index 52273542e6ef..52d878f5a44d 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -48,6 +48,8 @@ static void print_open_warning(int err, bool uprobe)
 			   uprobe ? 'u' : 'k', config);
 	} else if (err == -ENOTSUP)
 		pr_warning("Tracefs or debugfs is not mounted.\n");
+	else if (err == -EACCES)
+		pr_warning("No permission to access tracefs. Please run this command again with sudo.\n");
 	else
 		pr_warning("Failed to open %cprobe_events: %s\n",
 			   uprobe ? 'u' : 'k',
@@ -62,6 +64,8 @@ static void print_both_open_warning(int kerr, int uerr)
 	else if (kerr == -ENOENT && uerr == -ENOENT)
 		pr_warning("Please rebuild kernel with CONFIG_KPROBE_EVENTS "
 			   "or/and CONFIG_UPROBE_EVENTS.\n");
+	else if (kerr == -EACCES && uerr == -EACCES)
+		pr_warning("No permission to access tracefs. Please run this command again with sudo.\n");
 	else {
 		char sbuf[STRERR_BUFSIZE];
 		pr_warning("Failed to open kprobe events: %s.\n",