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From:   Marco Elver <elver@google.com>
Date:   Wed, 15 Dec 2021 14:39:43 +0100
Message-ID: <CANpmjNNLG0F9WzNnQkJX+QEqdxnhWstuag_9jrid7zdJgivHyw@mail.gmail.com>
Subject: Re: [PATCH 12/43] kcsan: clang: retire CONFIG_KCSAN_KCOV_BROKEN
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Alexander Potapenko <glider@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Matthew Wilcox <willy@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
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On Wed, 15 Dec 2021 at 14:33, Mark Rutland <mark.rutland@arm.com> wrote:
>
> On Tue, Dec 14, 2021 at 05:20:19PM +0100, Alexander Potapenko wrote:
> > kcov used to be broken prior to Clang 11, but right now that version is
> > already the minimum required to build with KCSAN, that is why we don't
> > need KCSAN_KCOV_BROKEN anymore.
>
> Just to check, how is that requirement enforced?

HAVE_KCSAN_COMPILER will only be true with Clang 11 or later, due to
no prior compiler having "-tsan-distinguish-volatile=1".

> I see the core Makefiles enforce 10.0.1+, but I couldn't spot an explicit
> version dependency in Kconfig.kcsan.
>
> Otherwise, this looks good to me!

I think 5.17 will be Clang 11 only, so we could actually revert
ea91a1d45d19469001a4955583187b0d75915759:
https://lkml.kernel.org/r/Yao86FeC2ybOobLO@archlinux-ax161

I should resend that to be added to the -kbuild tree.