Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace

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From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace
Date	Tue, 12 Jul 2016 16:30:03 +0200
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On Tue, Jul 12, 2016 at 08:55:17AM -0500, Eric W. Biederman wrote:

> I completely misread the description of this, or I would have something
> earlier.  For some reason I thought he was talking about the perf
> controller.
> 
> As I recall the tricky part of this was to have tracing that was safe
> and usable inside of a container.  If you can align a per cgroup with
> your container that is probably sufficient for the select of processes.
> 
> At the same time there is a real desire to have identifiers like pids
> translated into the appropriate form for inside of the container.
> Without that translation they are meaningless inside a container.
> Further it is necessary to be certain the trancing that is used is is
> safe for unprivileged users.
> 
> I don't think I ever suggested or approved of the concept of a perf
> namespace and that sounds a bit dubious to me.

So perf uses the pid-namespace of the event-creator to report PID/TID
numbers in.

So sys_perf_event_open() -> perf_event_alloc() does
get_pid_ns(task_active_pid_ns(current)) to set event->ns and then we do:
task_{tgid,pid}_nr_ns(p, event->ns) to report the PID/TID resp., see
perf_event_{pid,tid}().

Thread

Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace Aravinda Prasad <aravinda@linux.vnet.ibm.com> - 2016-07-12 11:30 +0200
  Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace Peter Zijlstra <peterz@infradead.org> - 2016-07-12 13:50 +0200
    Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace Nikolay Borisov <kernel@kyup.com> - 2016-07-12 14:50 +0200
      Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace Peter Zijlstra <peterz@infradead.org> - 2016-07-12 15:10 +0200
        Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace ebiederm@xmission.com (Eric W. Biederman) - 2016-07-12 16:10 +0200
          Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace Peter Zijlstra <peterz@infradead.org> - 2016-07-12 16:30 +0200
            Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace Aravinda Prasad <aravinda@linux.vnet.ibm.com> - 2016-07-12 18:10 +0200
        Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace Aravinda Prasad <aravinda@linux.vnet.ibm.com> - 2016-07-12 18:30 +0200

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