linux-kernel - Re: READ_ONCE() + STACKPROTECTOR_STRONG == :/ (was Re: [GIT PULL] Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops))

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Message-ID: <CAHk-=whBnZBVNwu8aVVp205EKk7xtsnQgSjs38a5=y9HyheXzQ@mail.gmail.com>
Date:   Tue, 17 Dec 2019 10:04:29 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Will Deacon <will@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Daniel Axtens <dja@...ens.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        linux-arch <linux-arch@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: READ_ONCE() + STACKPROTECTOR_STRONG == :/ (was Re: [GIT PULL]
 Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops))

On Tue, Dec 17, 2019 at 9:07 AM Will Deacon <will@...nel.org> wrote:
>
> However, I'm really banging my head against the compiler trying to get
> your trick above to work for pointer types when the pointed-to-type is
> not defined.

You are right, of course. The trick works fine with arithmetic types,
but since it does use arithmetic, it requires that pointer types be
not only declared, but defined. The addition wants the size of the
underlying type (even though with an addition of zero it wouldn't be
required - but that's not how C works).

Let me think about it.

             Linus