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Date:   Tue, 16 Jul 2019 19:55:00 -0400
From:   Joel Fernandes <joel@joelfernandes.org>
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        Adrian Ratiu <adrian.ratiu@collabora.com>,
        Alexei Starovoitov <ast@kernel.org>, bpf@vger.kernel.org,
        Brendan Gregg <brendan.d.gregg@gmail.com>, connoro@google.com,
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        Masami Hiramatsu <mhiramat@kernel.org>,
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Subject: Re: [PATCH RFC 0/4] Add support to directly attach BPF program to
 ftrace
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On Tue, Jul 16, 2019 at 06:41:50PM -0400, Joel Fernandes wrote:
> On Tue, Jul 16, 2019 at 03:26:52PM -0700, Alexei Starovoitov wrote:
> > On Tue, Jul 16, 2019 at 05:30:50PM -0400, Joel Fernandes wrote:
> > > 
> > > I also thought about the pinning idea before, but we also want to add support
> > > for not just raw tracepoints, but also regular tracepoints (events if you
> > > will). I am hesitant to add a new BPF API just for creating regular
> > > tracepoints and then pinning those as well.
> > 
> > and they should be done through the pinning as well.
> 
> Hmm ok, I will give it some more thought.

I think I can make the new BPF API + pinning approach work, I will try to
work on something like this and post it soon.

Also, I had a question below if you don't mind taking a look:

thanks Alexei!

> > > I don't see why a new bpf node for a trace event is a bad idea, really.
> > 
> > See the patches for kprobe/uprobe FD-based api and the reasons behind it.
> > tldr: text is racy, doesn't scale, poor security, etc.
> 
> Is it possible to use perf without CAP_SYS_ADMIN and control security at the
> per-event level? We are selective about who can access which event, using
> selinux. That's how our ftrace-based tracers work. Its fine grained per-event
> control. That's where I was going with the tracefs approach since we get that
> granularity using the file system.
> 
> Thanks.
>