[PATCH] perf tools: check perf_event_paranoid and kptr_restrict on 'perf top'

[Jackie Liu]

Perf top will segfault, we should give prompt information like perf
record instead of crashing directly.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx>
---
 tools/perf/builtin-top.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 3673c04d16b6..b257fadba3bd 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1239,6 +1239,14 @@ static int __cmd_top(struct perf_top *top)
 			return ret;
 	}
 
+	if (symbol_conf.kptr_restrict && !evlist__exclude_kernel(top->evlist)) {
+		pr_warning(
+"Kernel address maps (/proc/{kallsyms,modules}) are restricted.\n\n"
+"Check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.\n\n"
+"Kernel samples will not be resolved.\n");
+		return -1;
+	}
+
 	ret = callchain_param__setup_sample_type(&callchain_param);
 	if (ret)
 		return ret;
-- 
2.25.1