perf tracepoints for regular user?

Hi,

I am trying to use 'perf stat -e uprobes:xyz' on a tracepoint that I have previously set, but with no success.
I thought that I should be able to do that when allowing my user access to debugfs, but this is what I get:

$ id -u;id -g
1001
1001
$ mount|grep debug
none on /sys/kernel/debug type debugfs (rw,uid=1001,gid=1001)
$ ls /sys/kernel/debug
acpi  bluetooth  cleancache  dell_laptop  dri extfrag ...
$ ls /sys/kernel/debug/tracing/
ls: cannot open directory /sys/kernel/debug/tracing/: Permission denied

So, my user can't look in the tracing subdirectory and perf list doesn't show the uprobes either.

I have also tried to ´sudo setcap cap_sys_admin+eip $(which perf)´, also without success.

Quoted 20 lines · On Freitag, 15. Januar 2016 22:05:16 CET Benjamin King wrote:

Hi,

I am trying to use 'perf stat -e uprobes:xyz' on a tracepoint that I have previously set, but with no success.
I thought that I should be able to do that when allowing my user access to debugfs, but this is what I get:

$ id -u;id -g
1001
1001
$ mount|grep debug
none on /sys/kernel/debug type debugfs (rw,uid=1001,gid=1001)
$ ls /sys/kernel/debug
acpi  bluetooth  cleancache  dell_laptop  dri extfrag ...
$ ls /sys/kernel/debug/tracing/
ls: cannot open directory /sys/kernel/debug/tracing/: Permission denied

So, my user can't look in the tracing subdirectory and perf list doesn't show the uprobes either.

Quoted 2 lines

I have also tried to ´sudo setcap cap_sys_admin+eip $(which perf)´, also without success.

Try these commands:

$ sudo mount -o remount,mode=755 /sys/kernel/debug
$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
$ echo \"-1\" | sudo tee /proc/sys/kernel/perf_event_paranoid

Quoted 2 lines · On Freitag, 15. Januar 2016 22:05:16 CET Benjamin King wrote:

I am trying to use 'perf stat -e uprobes:xyz' on a tracepoint that I have previously set, but with no success.

Try these commands:

$ sudo mount -o remount,mode=755 /sys/kernel/debug
$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
$ echo \"-1\" | sudo tee /proc/sys/kernel/perf_event_paranoid

Hi Milian,

Quoted 8 lines · Milian Wolff

Quoted 2 lines · On Freitag, 15. Januar 2016 22:05:16 CET Benjamin King wrote:

I am trying to use 'perf stat -e uprobes:xyz' on a tracepoint that I have previously set, but with no success.

Try these commands:

$ sudo mount -o remount,mode=755 /sys/kernel/debug
$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
$ echo \"-1\" | sudo tee /proc/sys/kernel/perf_event_paranoid

Hm, that does not work for me. I can do the first remount, but not the second:
-----

$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
mount: can't find /sys/kernel/debug/tracing in /etc/fstab
$ mount|grep debug
none on /sys/kernel/debug type debugfs (rw,mode=755,mode=755)
-----

And then, I still can not see tracepoints as a regular user:
-----

$ perf list tracepoint

List of pre-defined events (to be used in -e):

$ -----

If this works for you, then maybe it's my version? I'm on 4.2.3

Quoted 4 lines

$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
mount: can't find /sys/kernel/debug/tracing in /etc/fstab
$ mount|grep debug
none on /sys/kernel/debug type debugfs (rw,mode=755,mode=755)

Ok, your kernel is old and doesn't have the tracefs:

[acme@zoo ~]$ mount | egrep \(debug\|trace\)fs
debugfs on /sys/kernel/debug type debugfs (rw,relatime,seclabel,mode=755) tracefs on /sys/kernel/debug/tracing type tracefs (rw,relatime,mode=755) [...]
[acme@zoo ~]$ uname -r
4.3.0+

Hi Arnaldo,

Quoted 6 lines

Quoted 4 lines

$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing
mount: can't find /sys/kernel/debug/tracing in /etc/fstab
$ mount|grep debug
none on /sys/kernel/debug type debugfs (rw,mode=755,mode=755)

Ok, your kernel is old and doesn't have the tracefs:

Quoted 6 lines

[acme@zoo ~]$ mount | egrep \(debug\|trace\)fs
debugfs on /sys/kernel/debug type debugfs (rw,relatime,seclabel,mode=755) tracefs on /sys/kernel/debug/tracing type tracefs (rw,relatime,mode=755) [...]
[acme@zoo ~]$ uname -r
4.3.0+

That's odd. According to kernelnewbies.org (Yes, I am that much of a kernel hacker :-) ), tracefs should be in since 4.1 and I'm on 4.2, but I can only find CONFIG_DEBUG_FS in my kernel configuration. There is no mentioning of a corresponding CONFIG_TRACE_FS there.

I'll try to upgrade to a more recent kernel and stop bugging you guys until then.

Not having tracefs, if that is indeed the case, only means that the remount isn't needed, as what is in tracefs is what, before its existence, lived in a debugfs directory, /sys/kernel/debug/tracing, i.e. remounting just /sys/kernel/debug/ would then be enough.