linux-kernel - Re: Collecting both remote and "local" coverage with KCOV

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Date:   Mon, 16 Nov 2020 09:34:49 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Alexander Bulekov <alxndr@...edu>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Collecting both remote and "local" coverage with KCOV

On Mon, Nov 16, 2020 at 3:39 AM Alexander Bulekov <alxndr@...edu> wrote:
>
> Hello,
> I'm trying to collect coverage over the syscalls issued by my process,
> as well as the kthreads spawned as a result of these syscalls
> (eg coverage over vhost ioctls and the worker kthread). Is there a way
> to collect coverage with both KCOV_REMOTE_ENABLE(with common_handle) and
> KCOV_ENABLE, simultaneously?
>
> Based on the code it seems that these two modes are mutually
> exclusive within a single task, but I don't think this is mentioned in
> the Documentation, so I want to make sure I'm not missing something.

Hi Alex,

Yes, it's probably not supported within a single task. The easiest way
to verify is to try it ;)

It is possible to collect both coverages, but you will need 2 threads
(one just to set up remote KCOV).

Unless I am missing any fundamental limitations, I would say it would
be reasonable to support this within a single task as well.