linux-kernel - [PATCH v2] perf tools: perf_event_paranoid and kptr

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Date:   Thu, 25 Feb 2021 14:25:30 +0800
From:   Jackie Liu <jackieliu2113@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Jackie Liu <liuyun01@...inos.cn>, Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH v2] perf tools: perf_event_paranoid and kptr_restrict may crash on 'perf top'

After install the libelf-dev package and compiling perf, kptr_restrict=2
and perf_event_paranoid=3 will cause perf top to crash, because the
value of /proc/kallsyms cannot be obtained, which leads to
info->jited_ksyms == NULL. In order to solve this problem, Add a
judgment before use.

Suggested-by: Jiri Olsa <jolsa@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Jackie Liu <liuyun01@...inos.cn>
---
 tools/perf/util/bpf-event.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
index 57d58c81a5f8..b1ce2d189d37 100644
--- a/tools/perf/util/bpf-event.c
+++ b/tools/perf/util/bpf-event.c
@@ -225,6 +225,11 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_session *session,
 		perf_env__fetch_btf(env, info->btf_id, btf);
 	}
 
+	if (!info->jited_ksyms) {
+		err = -1;
+		goto out;
+	}
+
 	/* Synthesize PERF_RECORD_KSYMBOL */
 	for (i = 0; i < sub_prog_cnt; i++) {
 		__u32 *prog_lens = (__u32 *)(uintptr_t)(info->jited_func_lens);
-- 
2.25.1