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 = <setting>)
  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 = <setting>)
  Error:
  Failure to open any events for recording.

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

0 files changed, 0 insertions, 0 deletions