linux-kernel - Re: [PATCH] kcov: fix generic Kconfig dependencies if ARCH_WANTS_NO

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Message-ID: <CANpmjNPaKMsgfDo5PE_dX794otFXbJvGubxG44C8-QL66UVaUw@mail.gmail.com>
Date:   Thu, 9 Dec 2021 11:00:00 +0100
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, Andrew Morton <akpm@...ux-foundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, kasan-dev@...glegroups.com,
        Peter Zijlstra <peterz@...radead.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] kcov: fix generic Kconfig dependencies if ARCH_WANTS_NO_INSTR

On Wed, 1 Dec 2021 at 16:26, Marco Elver <elver@...gle.com> wrote:
[...]
> At the time of 0f1441b44e823, we didn't yet have ARCH_WANTS_NO_INSTR,
> but now we can move the Kconfig dependency checks to the generic KCOV
> option. KCOV will be available if:
>
>         - architecture does not care about noinstr, OR
>         - we have objtool support (like on x86), OR
>         - GCC is 12.0 or newer, OR
>         - Clang is 13.0 or newer.
>
> Signed-off-by: Marco Elver <elver@...gle.com>

I think this is good to pick up. Even though it has an x86 change in
it, I think kcov changes go through -mm. Andrew, x86 maintainers, any
preference?

With the conclusion from [1], I think we decided it's better to take
this now, given we discovered KCOV already appears broken on arm64
(likely due to noinstr) and e.g. syzbot disables it on arm64.

[1] https://lkml.kernel.org/r/Yae+6clmwHox7CHN@FVFF77S0Q05N

Thanks,
-- Marco