Hi Jiri,
On Thu, Sep 10, 2015 at 10:05:37AM +0200, Jiri Olsa wrote:
> On Thu, Sep 10, 2015 at 04:00:30PM +0900, Namhyung Kim wrote:
> > On Mon, Sep 07, 2015 at 10:38:07AM +0200, Jiri Olsa wrote:
> > > Enhancing parsing events tracepoint error output. Adding
> > > more verbose output when the tracepoint is not found or
> > > the tracing event path cannot be access.
> > >
> > > $ sudo perf record -e sched:sched_krava ls
> > > event syntax error: 'sched:sched_krava'
> > > \___ unknown tracepoint
> > >
> > > Error: File
> > > /sys/kernel/debug/tracing//tracing/events/sched/sched_krava not found.
> > > Hint: Perhaps this kernel misses some CONFIG_ setting to enable this
> > > feature?.
> > >
> > > Run 'perf list' for a list of valid events
> > > ...
> > >
> > > $ perf record -e sched:sched_krava ls
> > > event syntax error: 'sched:sched_krava'
> > > \___ can't access trace events
> > >
> > > Error: No permissions to read
> > > /sys/kernel/debug/tracing//tracing/events/sched/sched_krava
> > > Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug'
> >
> > What about tracefs? On my system, tracefs is mounted on
> > /sys/kernel/debug/tracing thus I cannot access trace events after
> > remounting debugfs with mode=755.
>
> right, patch below keeps the actual mount and
> display proper info.. could you please try?
Sure, this patch displays the proper tracefs mountpoint. But it also
has a problem - if tracefs is mounted under debugfs, the access mode
of debugfs also affects, so in this case I had to change it both for
debugfs and tracefs..
>
> >
> > Also, IIRC tracepoint events adds PERF_SAMPLE_RAW bit automatically,
> > and it requires perf_event_paranoid being -1 for non-root user, right?
>
> there's related error message when you try to open the
> tracepoint, the whole session is like:
Ah, great. :)
Thanks,
Namhyung
> [jolsa@krava perf]$ ./perf record -e sched:sched_switch ls
> event syntax error: 'sched:sched_switch'
> \___ can't access trace events
>
> Error: No permissions to read
> /sys/kernel/debug/tracing/events/sched/sched_switch
> Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing'
>
> Run 'perf list' for a list of valid events
>
> usage: perf record [<options>] [<command>]
> or: perf record [<options>] -- <command> [<options>]
>
> -e, --event <event> event selector. use 'perf list' to list available
> events
> [jolsa@krava perf]$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
> [jolsa@krava perf]$ ./perf record -e sched:sched_switch ls
> Error:
> You may not have permission to collect stats.
> Consider tweaking /proc/sys/kernel/perf_event_paranoid:
> -1 - Not paranoid at all
> 0 - Disallow raw tracepoint access for unpriv
> 1 - Disallow cpu events for unpriv
> 2 - Disallow kernel profiling for unpriv
>
>
>
> thanks,
> jirka
>
>
> ---
> diff --git a/tools/lib/api/fs/tracing_path.c b/tools/lib/api/fs/tracing_path.c
> index 38aca2dd1946..0406a7d5c891 100644
> --- a/tools/lib/api/fs/tracing_path.c
> +++ b/tools/lib/api/fs/tracing_path.c
> @@ -12,12 +12,14 @@
> #include "tracing_path.h"
>
>
> +char tracing_mnt[PATH_MAX + 1] = "/sys/kernel/debug";
> char tracing_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing";
> char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
>
>
> static void __tracing_path_set(const char *tracing, const char *mountpoint)
> {
> + snprintf(tracing_mnt, sizeof(tracing_mnt), "%s", mountpoint);
> snprintf(tracing_path, sizeof(tracing_path), "%s/%s",
> mountpoint, tracing);
> snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s%s",
> @@ -109,19 +111,10 @@ static int strerror_open(int err, char *buf, size_t
> size, const char *filename)
> "Hint:\tTry 'sudo mount -t debugfs nodev
> /sys/kernel/debug'");
> break;
> case EACCES: {
> - const char *mountpoint = debugfs__mountpoint();
> -
> - if (!access(mountpoint, R_OK) && strncmp(filename, "tracing/",
> 8) == 0) {
> - const char *tracefs_mntpoint = tracefs__mountpoint();
> -
> - if (tracefs_mntpoint)
> - mountpoint = tracefs__mountpoint();
> - }
> -
> snprintf(buf, size,
> "Error:\tNo permissions to read %s/%s\n"
> "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
> - tracing_events_path, filename, mountpoint);
> + tracing_events_path, filename, tracing_mnt);
> }
> break;
> default:
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