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In-Reply-To: <9d4156e6-ec4f-a742-a44e-f38bf7fa9ba9@arm.com>
From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Mon, 16 Nov 2020 14:50:47 +0100
Message-ID: <CAAeHK+xb4w1XSe_cXeV77d3VkHq6ABAKkKuEaFN-uFVY457-Ww@mail.gmail.com>
Subject: Re: [PATCH RFC v2 04/21] kasan: unpoison stack only with CONFIG_KASAN_STACK
To:     Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Marco Elver <elver@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>
Cc:     Will Deacon <will.deacon@arm.com>,
        Alexander Potapenko <glider@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Kostya Serebryany <kcc@google.com>,
        Peter Collingbourne <pcc@google.com>,
        Serban Constantinescu <serbanc@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Elena Petrova <lenaptr@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, Nov 16, 2020 at 1:42 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> >>>>
> >>>> Not sure why we did this instead of the following, but okay.
> >>>>
> >>>>  config KASAN_STACK
> >>>> -       int
> >>>> -       default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
> >>>> -       default 0
> >>>> +       bool
> >>>> +       default y if KASAN_STACK_ENABLE || CC_IS_GCC
> >>>> +       default n
> >>>
> >>> I wondered the same, but then looking at scripts/Makefile.kasan I
> >>> think it's because we directly pass it to the compiler:
> >>>     ...
> >>>     $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
> >>>     ...
> >>
> >> Try this instead:
> >>
> >>       $(call cc-param,asan-stack=$(if $(CONFIG_KASAN_STACK),1,0)) \
> >
> >
> > We could have just 1 config instead of 2 as well.
> > For gcc we could do no prompt and default value y, and for clang --
> > prompt and default value n. I think it should do what we need.
> >
>
> I agree with Catalin's proposal since it should simplify things.
>
> Nit: 'default n' is the default hence I do not think it should be required
> explicitly.

Fixing this sounds like a good idea, but perhaps not as a part of this
series, to not overinflate it even further.

I've filed a bug for this: https://bugzilla.kernel.org/show_bug.cgi?id=210221