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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Mon, 11 Jan 2021 20:30:28 +0100
Message-ID: <CAAeHK+x5VaQ5U4G0pei7Bzf6CWcz+BqADj411rd9P6b=j4uNvw@mail.gmail.com>
Subject: Re: [PATCH v3] kasan: remove redundant config option
To:     Nathan Chancellor <natechancellor@gmail.com>
Cc:     Walter Wu <walter-zh.wu@mediatek.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        wsd_upstream <wsd_upstream@mediatek.com>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@lists.infradead.org>
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On Mon, Jan 11, 2021 at 8:11 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Mon, Jan 11, 2021 at 08:03:29PM +0100, Andrey Konovalov wrote:
> > On Mon, Jan 11, 2021 at 7:59 PM Nathan Chancellor
> > <natechancellor@gmail.com> wrote:
> > >
> > > > > -config KASAN_STACK_ENABLE
> > > > > +config KASAN_STACK
> > > > >         bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> > > >
> > > > Does this syntax mean that KASAN_STACK is only present for
> > > > CC_IS_CLANG? Or that it can only be disabled for CC_IS_CLANG?
> > >
> > > It means that the option can only be disabled for clang.
> >
> > OK, got it.
> >
> > > > Anyway, I think it's better to 1. allow to control KASAN_STACK
> > > > regardless of the compiler (as it was possible before), and 2. avoid
> > >
> > > It has never been possible to control KASAN_STACK for GCC because of the
> > > bool ... if ... syntax. This patch does not change that logic. Making it
> > > possible to control KASAN_STACK with GCC seems fine but that is going to
> > > be a new change that would probably be suited for a new patch on top of
> > > this one.
> >
> > The if syntax was never applied to KASAN_STACK, only to
> > KASAN_STACK_ENABLE, so it should have been possible (although I've
> > never specifically tried it).
>
> CONFIG_KASAN_STACK was not a user selectable symbol so it was always 1
> for GCC.

Ah, indeed.

Thanks for the clarification!