linux-kernel - Re: [PATCH] crypto: arm/curve25519

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Message-ID: <20210416113248.GM16633@gondor.apana.org.au>
Date:   Fri, 16 Apr 2021 21:32:48 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Russell King <linux@...linux.org.uk>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Jessica Clarke <jrtc27@...c27.com>
Subject: Re: [PATCH] crypto: arm/curve25519 - Move '.fpu' after '.arch'

On Fri, Apr 09, 2021 at 03:11:55PM -0700, Nathan Chancellor wrote:
> Debian's clang carries a patch that makes the default FPU mode
> 'vfp3-d16' instead of 'neon' for 'armv7-a' to avoid generating NEON
> instructions on hardware that does not support them:
> 
> https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/-/raw/5a61ca6f21b4ad8c6ac4970e5ea5a7b5b4486d22/debian/patches/clang-arm-default-vfp3-on-armv7a.patch
> https://bugs.debian.org/841474
> https://bugs.debian.org/842142
> https://bugs.debian.org/914268
> 
> This results in the following build error when clang's integrated
> assembler is used because the '.arch' directive overrides the '.fpu'
> directive:
> 
> arch/arm/crypto/curve25519-core.S:25:2: error: instruction requires: NEON
>  vmov.i32 q0, #1
>  ^
> arch/arm/crypto/curve25519-core.S:26:2: error: instruction requires: NEON
>  vshr.u64 q1, q0, #7
>  ^
> arch/arm/crypto/curve25519-core.S:27:2: error: instruction requires: NEON
>  vshr.u64 q0, q0, #8
>  ^
> arch/arm/crypto/curve25519-core.S:28:2: error: instruction requires: NEON
>  vmov.i32 d4, #19
>  ^
> 
> Shuffle the order of the '.arch' and '.fpu' directives so that the code
> builds regardless of the default FPU mode. This has been tested against
> both clang with and without Debian's patch and GCC.
> 
> Cc: stable@...r.kernel.org
> Fixes: d8f1308a025f ("crypto: arm/curve25519 - wire up NEON implementation")
> Link: https://github.com/ClangBuiltLinux/continuous-integration2/issues/118
> Reported-by: Arnd Bergmann <arnd@...db.de>
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Suggested-by: Jessica Clarke <jrtc27@...c27.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>  arch/arm/crypto/curve25519-core.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt