linux-kernel - Re: [PATCH] x86: crypto: fix building crc32c with clang ias

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Message-ID: <20200527164219.GB1073507@ubuntu-s3-xlarge-x86>
Date:   Wed, 27 May 2020 09:42:19 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Tim Chen <tim.c.chen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] x86: crypto: fix building crc32c with clang ias

On Wed, May 27, 2020 at 04:17:40PM +0200, Arnd Bergmann wrote:
> The clang integrated assembler complains about movzxw:
> 
> arch/x86/crypto/crc32c-pcl-intel-asm_64.S:173:2: error: invalid instruction mnemonic 'movzxw'
> 
> It seems that movzwq is the mnemonic that it expects instead,
> and this is what objdump prints when disassembling the file.
> 
> Fixes: 6a8ce1ef3940 ("crypto: crc32c - Optimize CRC32C calculation with PCLMULQDQ instruction")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

We had an identical patch pending from another contributor, see the
discussion and result in the issue below.

https://github.com/ClangBuiltLinux/linux/issues/1010

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
>  arch/x86/crypto/crc32c-pcl-intel-asm_64.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S
> index 8501ec4532f4..442599cbe796 100644
> --- a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S
> +++ b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S
> @@ -170,7 +170,7 @@ continue_block:
>  
>  	## branch into array
>  	lea	jump_table(%rip), %bufp
> -	movzxw  (%bufp, %rax, 2), len
> +	movzwq  (%bufp, %rax, 2), len
>  	lea	crc_array(%rip), %bufp
>  	lea     (%bufp, len, 1), %bufp
>  	JMP_NOSPEC bufp
> -- 
> 2.26.2
>