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?
>
> 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:
[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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