perf tools: Warn that perf_event_paranoid can restrict kernel symbols

Warn that /proc/sys/kernel/perf_event_paranoid can also restrict kernel
symbols.
Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
Tested-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1566869956-7154-6-git-send-email-ilubashe@akamai.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -2372,7 +2372,7 @@ int cmd_record(int argc, const char **argv)
 	if (symbol_conf.kptr_restrict && !perf_evlist__exclude_kernel(rec->evlist))
 		pr_warning(
 "WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,\n"
-"check /proc/sys/kernel/kptr_restrict.\n\n"
+"check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.\n\n"
 "Samples in kernel functions may not be resolved if a suitable vmlinux\n"
 "file is not found in the buildid cache or in the vmlinux path.\n\n"
 "Samples in kernel modules won't be resolved at all.\n\n"

tools/perf/builtin-top.c

@@ -770,7 +770,7 @@ static void perf_event__process_sample(struct perf_tool *tool,
 		if (!perf_evlist__exclude_kernel(top->session->evlist)) {
 			ui__warning(
 "Kernel address maps (/proc/{kallsyms,modules}) are restricted.\n\n"
-"Check /proc/sys/kernel/kptr_restrict.\n\n"
+"Check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.\n\n"
 "Kernel%s samples will not be resolved.\n",
 			  al.map && map__has_symbols(al.map) ?
 			  " modules" : "");

tools/perf/builtin-trace.c

@@ -1382,7 +1382,7 @@ static char *trace__machine__resolve_kernel_addr(void *vmachine, unsigned long l
 
 	if (symbol_conf.kptr_restrict) {
 		pr_warning("Kernel address maps (/proc/{kallsyms,modules}) are restricted.\n\n"
-			   "Check /proc/sys/kernel/kptr_restrict.\n\n"
+			   "Check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.\n\n"
 			   "Kernel samples will not be resolved.\n");
 		machine->kptr_restrict_warned = true;
 		return NULL;