linux-kernel - Re: [PATCH] crypto: ccree - avoid out-of-range warnings from clang

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Message-ID: <CAOtvUMfNYkfKw-Vji7uVWXO=CbwGLj6=+awCKif5=cPCK1P-cQ@mail.gmail.com>
Date:   Tue, 28 Sep 2021 17:02:06 +0300
From:   Gilad Ben-Yossef <gilad@...yossef.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        YueHaibing <yuehaibing@...wei.com>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] crypto: ccree - avoid out-of-range warnings from clang

Hi,

Thank you Arnd.

On Mon, Sep 27, 2021 at 3:18 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> clang points out inconsistencies in the FIELD_PREP() invocation in
> this driver that result from the 'mask' being a 32-bit value:
>
> drivers/crypto/ccree/cc_driver.c:117:18: error: result of comparison of constant 18446744073709551615 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>         cache_params |= FIELD_PREP(mask, val);
>                         ^~~~~~~~~~~~~~~~~~~~~
> include/linux/bitfield.h:94:3: note: expanded from macro 'FIELD_PREP'
>                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/linux/bitfield.h:52:28: note: expanded from macro '__BF_FIELD_CHECK'
>                 BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull,         \
>                 ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> This does not happen in other places that just pass a constant here.
>
> Work around the warnings by widening the type of the temporary variable.
>
> Fixes: 05c2a705917b ("crypto: ccree - rework cache parameters handling")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Gilad ben-Yossef <gilad@...yossef.com>

Gilad



-- 
Gilad Ben-Yossef
Chief Coffee Drinker

values of β will give rise to dom!