From a108a6a4b9e8d81f6be0c0f8b93d3fbd57d2359e Mon Sep 17 00:00:00 2001 From: Leo Yan Date: Wed, 4 Feb 2026 14:26:15 +0000 Subject: [PATCH] perf record: Make logs more readable for event open failures Since commit ee27476fa3004f83 ("perf record: Skip don't fail for events that don't open"), if a user does not have permission to access a PMU event, perf reports: perf record -e cs_etm// -C 3 -- ls Error: Failure to open event 'cs_etm//u' on PMU 'cs_etm' which will be removed. No fallback found for 'cs_etm//u' for error 13 Error: Failure to open event 'dummy:u' on PMU 'software' which will be removed. No fallback found for 'dummy:u' for error 13 Error: Failure to open any events for recording. The log is not very helpful, as no clear indication of what "error 13" means or how to address the issue. This commit restores evsel__open_strerror() to generate a readable error message and print it out: perf record -e cs_etm// -C 3 -- ls Error: Failure to open event 'cs_etm//' on PMU 'cs_etm' which will be removed. Access to performance monitoring and observability operations is limited. Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open access to performance monitoring and observability operations for processes without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability. More information can be found at 'Perf events and tool security' document: https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html perf_event_paranoid setting is 1: -1: Allow use of (almost) all events by all users Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK >= 0: Disallow raw and ftrace function tracepoint access >= 1: Disallow CPU event access >= 2: Disallow kernel profiling To make the adjusted perf_event_paranoid setting permanent preserve it in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = ) Error: Failure to open event 'dummy:u' on PMU 'software' which will be removed. Access to performance monitoring and observability operations is limited. Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open access to performance monitoring and observability operations for processes without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability. More information can be found at 'Perf events and tool security' document: https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html perf_event_paranoid setting is 1: -1: Allow use of (almost) all events by all users Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK >= 0: Disallow raw and ftrace function tracepoint access >= 1: Disallow CPU event access >= 2: Disallow kernel profiling To make the adjusted perf_event_paranoid setting permanent preserve it in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = ) Error: Failure to open any events for recording. Reviewed-by: Ian Rogers Signed-off-by: Leo Yan Cc: Adrian Hunter Cc: James Clark Cc: Jiri Olsa Cc: Namhyung Kim Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 663ca3a03396..60d764068302 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -1403,6 +1403,7 @@ try_again: } #endif if (report_error || verbose > 0) { + evsel__open_strerror(pos, &opts->target, errno, msg, sizeof(msg)); ui__error("Failure to open event '%s' on PMU '%s' which will be " "removed.\n%s\n", evsel__name(pos), evsel__pmu_name(pos), msg);