linux-kernel - Re: [PATCH] kcov: convert kcov.refcount to refcount

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Date:   Mon, 21 Jan 2019 18:07:03 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     "Reshetova, Elena" <elena.reshetova@...el.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] kcov: convert kcov.refcount to refcount_t

On Mon, Jan 21, 2019 at 3:07 PM Reshetova, Elena
<elena.reshetova@...el.com> wrote:
>
>  > Just to check, has this been tested with CONFIG_REFCOUNT_FULL and
> > > something poking kcov?
> > >
> > > Given lib/refcount.c is instrumented, the refcount_*() calls will
> > > recurse back into the kcov code. It looks like that's fine, given these
> > > are only manipulated in setup/teardown paths, but it would be nice to be
> > > sure.
> >
> > A simple program using KCOV is available here:
> > https://elixir.bootlin.com/linux/v5.0-rc3/source/Documentation/dev-
> > tools/kcov.rst#L42
> > or here (it's like strace but collects and prints KCOV coverage):
> > https://github.com/google/syzkaller/blob/master/tools/kcovtrace/kcovtrace.c
> >
>
> No, this one hasn't gone via any particular testing apart
> the tests that zero day runs automatically (like boot tests, etc.) since normally
> it is hard for me to know how exactly to test a particular component in a meaningful
> way.
>
> But I can try to test with the above example now, if it helps!

We really need automated tests but I wan't able to figure out how to
write/run kernel tests. Sorry about that. Need to try again. I've
filed https://bugzilla.kernel.org/show_bug.cgi?id=202363 for this.