linux-kernel - Re: [PATCH] selinux: add tracepoint on denials

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Date:   Tue, 28 Jul 2020 09:12:20 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thiébaud Weksteen <tweek@...gle.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Nick Kralevich <nnk@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Eric Paris <eparis@...isplace.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        SElinux list <selinux@...r.kernel.org>
Subject: Re: [PATCH] selinux: add tracepoint on denials

On Tue, 28 Jul 2020 14:49:24 +0200
Thiébaud Weksteen <tweek@...gle.com> wrote:

> Thanks for the review! I'll send a new revision of the patch with the
> %x formatter and using the TP_CONDITION macro.
> 
> On adding further information to the trace event, I would prefer
> adding the strict minimum to be able to correlate the event with the
> avc message. The reason is that tracevents have a fixed size (see
> https://www.kernel.org/doc/Documentation/trace/events.txt). For

Wait! What?

Where in that document does it say that trace events have a fixed size.
We have a lot of dynamically sized trace events.

> instance, we would need to decide on a maximum size for the string
> representation of the list of permissions. This would also duplicate
> the reporting done in the avc audit event. I'll simply add the pid as
> part of the printk, which should be sufficient for the correlation.
> 

Please take a look at samples/trace_events/trace_events_sample.h

and read the example on __print_symbolic().

I think that's what you are looking for.

-- Steve