linux-kernel - Re: [PATCH 3/3] [RFC] Revert "drm/i915: use variadic macros and arrays to choose port/pipe based registers"

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Message-ID: <87o9wwb38t.fsf@intel.com>
Date:   Mon, 20 Mar 2017 13:24:02 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Mika Kuoppala <mika.kuoppala@...ux.intel.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Imre Deak <imre.deak@...el.com>,
        Ander Conselvan de Oliveira 
        <ander.conselvan.de.oliveira@...el.com>,
        Robert Bragg <robert@...bynine.org>,
        intel-gfx@...ts.freedesktop.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] [RFC] Revert "drm/i915: use variadic macros and arrays to choose port/pipe based registers"

On Mon, 20 Mar 2017, Arnd Bergmann <arnd@...db.de> wrote:
> I don't know how to generate a URL for it, but after adding this to the
> command line for gcc-7,
>
> -fsanitize=kernel-address -fasan-shadow-offset=0xdfff900000000000
> --param asan-stack=1 --param asan-globals=1 --param
> asan-instrumentation-with-call-threshold=10000
> -fsanitize-address-use-after-scope
>
> the code turned from really nice into the log series of checks below.
> Without  -fsanitize-address-use-after-scope (which didn't exist before gcc-7),
> it's less bad but still exceeds the (arbitrary) 1536 byte limit.

It seems to be the combination of --param asan-stack=1 and
-fsanitize-address-use-after-scope that really blows up the code [1]. I
filed a GCC bug on it, mostly to see what they say [2]. I don't know,
maybe they think it's expected. *shrug*.


BR,
Jani.

[1] https://godbolt.org/g/hgS817
[2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80114


-- 
Jani Nikula, Intel Open Source Technology Center