linux-kernel - Re: [PATCH -rcu] asm-generic, kcsan: Add KCSAN instrumentation for bitops

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Message-ID: <CANpmjNOpTYnF3ssqrE_s+=UA-2MpfzzdrXoyaifb3A55_mc0uA@mail.gmail.com>
Date:   Wed, 15 Jan 2020 20:51:26 +0100
From:   Marco Elver <elver@...gle.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        christophe leroy <christophe.leroy@....fr>,
        Daniel Axtens <dja@...ens.net>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH -rcu] asm-generic, kcsan: Add KCSAN instrumentation for bitops

On Wed, 15 Jan 2020 at 20:27, Arnd Bergmann <arnd@...db.de> wrote:
>
> On Wed, Jan 15, 2020 at 5:58 PM Marco Elver <elver@...gle.com> wrote:
> >   * set_bit - Atomically set a bit in memory
> > @@ -26,6 +27,7 @@
> >  static inline void set_bit(long nr, volatile unsigned long *addr)
> >  {
> >         kasan_check_write(addr + BIT_WORD(nr), sizeof(long));
> > +       kcsan_check_atomic_write(addr + BIT_WORD(nr), sizeof(long));
> >         arch_set_bit(nr, addr);
> >  }
>
> It looks like you add a kcsan_check_atomic_write or kcsan_check_write directly
> next to almost any instance of kasan_check_write().
>
> Are there any cases where we actually just need one of the two but not the
> other? If not, maybe it's better to rename the macro and have it do both things
> as needed?

Do you mean adding an inline helper at the top of each bitops header
here, similar to what we did for atomic-instrumented?  Happy to do
that if it improves readability.

Thanks,
-- Marco