linux-kernel - Re: [PATCH] x86, crypto: Check if gas supports CRC32

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Date:	Thu, 31 Jul 2014 07:57:22 +0200
From:	Mathias Krause <minipli@...glemail.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	x86-ml <x86@...nel.org>,
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, crypto: Check if gas supports CRC32

On 31 July 2014 00:11, Borislav Petkov <bp@...en8.de> wrote:
>
> On Wed, Jul 30, 2014 at 11:28:14PM +0200, Mathias Krause wrote:
> > Gah, CONFIG_AS_CRC32 gets defined as a preprocessor symbol only so
> > cannot be used in makefiles. So crc32c-pcl-intel-asm_64.S needs a
> > "#ifdef CONFIG_AS_CRC32" guard and still be compiled for CONFIG_64BIT,
> > as it is now. It'll be an empty object for older binutils versions not
> > supporting the crc32 instruction.
>
> Yeah, that makes it all even simpler, thanks!
>
> We're still b0rked though:
>
> arch/x86/crypto/crct10dif-pcl-asm_64.S: Assembler messages:
> arch/x86/crypto/crct10dif-pcl-asm_64.S:147: Error: no such instruction: `pclmulqdq $0x0,%xmm10,%xmm0'
> arch/x86/crypto/crct10dif-pcl-asm_64.S:148: Error: no such instruction: `pclmulqdq $0x11,%xmm10,%xmm8'
> arch/x86/crypto/crct10dif-pcl-asm_64.S:149: Error: no such instruction: `pclmulqdq $0x0,%xmm10,%xmm1'
> ...
>
> and need checking for more instructions. I'll play with this more
> tomorrow.
>

You probably can reuse the AVX test for this -- either the
CONFIG_AS_AVX preprocessor one or the $(avx_supported) make one, local
to arch/x86/crypto/Makefile.
Even though the CLMUL feature has not much to with AVX (it has a
dedicated CPUID feature bit), support for it in binutils was added
together with AVX support, see
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c0f3af977b0f28a0dc5a620110b8dcf9d8286f84

Regards,
Mathias

> Good night :-)
>
> --
> Regards/Gruss,
>     Boris.
>
> Sent from a fat crate under my desk. Formatting is fine.
> --
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