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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
	"herbert@gondor.apana.org.au" <herbert@gondor.apana.org.au>,
	"samitolvanen@google.com" <samitolvanen@google.com>
Subject: Re: [PATCH v2] crypto/arm: accelerated SHA-512 using ARM generic ASM and NEON
Date: Sat, 11 Apr 2015 09:35:15 +0200	[thread overview]
Message-ID: <CAKv+Gu-6mZwrVSCvS+ZWWwwM-294nWAqX4_J3r5Z8NM7KKC0=Q@mail.gmail.com> (raw)
In-Reply-To: <F695F357-2A5C-4DFC-9F0E-188CDBBE7C01@linaro.org>

On 10 April 2015 at 22:23, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>
>> On 10 apr. 2015, at 22:08, Arnd Bergmann <arnd@arndb.de> wrote:
>>
>>> On Friday 10 April 2015 16:29:08 Ard Biesheuvel wrote:
>>> +#if __ARM_MAX_ARCH__>=7
>>> +.arch  armv7-a
>>> +.fpu   neon
>>> +
>>
>> This will cause a build failure on an ARMv7-M build, which is incompatible
>> with .arch  armv7-a and .fpu   neon.
>>
>
> The neon part depends on CONFIG_KERNEL_MODE_NEON, which would never be set for that platform, I suppose

On second thought, that is not entirely true, but I still don't think
there is problem here:
the .arch/.fpu declarations are understood perfectly fine by GAS when
targeting ARMv7-M. Only, it will emit code that is incompatible with
it. However, this code is invoked at runtime only if a NEON unit has
been detected, so it will just be ignored on ARMv7-M

-- 
Ard.

WARNING: multiple messages have this Message-ID (diff)
From: ard.biesheuvel@linaro.org (Ard Biesheuvel)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] crypto/arm: accelerated SHA-512 using ARM generic ASM and NEON
Date: Sat, 11 Apr 2015 09:35:15 +0200	[thread overview]
Message-ID: <CAKv+Gu-6mZwrVSCvS+ZWWwwM-294nWAqX4_J3r5Z8NM7KKC0=Q@mail.gmail.com> (raw)
In-Reply-To: <F695F357-2A5C-4DFC-9F0E-188CDBBE7C01@linaro.org>

On 10 April 2015 at 22:23, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>
>> On 10 apr. 2015, at 22:08, Arnd Bergmann <arnd@arndb.de> wrote:
>>
>>> On Friday 10 April 2015 16:29:08 Ard Biesheuvel wrote:
>>> +#if __ARM_MAX_ARCH__>=7
>>> +.arch  armv7-a
>>> +.fpu   neon
>>> +
>>
>> This will cause a build failure on an ARMv7-M build, which is incompatible
>> with .arch  armv7-a and .fpu   neon.
>>
>
> The neon part depends on CONFIG_KERNEL_MODE_NEON, which would never be set for that platform, I suppose

On second thought, that is not entirely true, but I still don't think
there is problem here:
the .arch/.fpu declarations are understood perfectly fine by GAS when
targeting ARMv7-M. Only, it will emit code that is incompatible with
it. However, this code is invoked at runtime only if a NEON unit has
been detected, so it will just be ignored on ARMv7-M

-- 
Ard.

  reply	other threads:[~2015-04-11  7:35 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-10 14:29 [PATCH v2] crypto/arm: accelerated SHA-512 using ARM generic ASM and NEON Ard Biesheuvel
2015-04-10 14:29 ` Ard Biesheuvel
2015-04-10 20:08 ` Arnd Bergmann
2015-04-10 20:08   ` Arnd Bergmann
2015-04-10 20:23   ` Ard Biesheuvel
2015-04-10 20:23     ` Ard Biesheuvel
2015-04-11  7:35     ` Ard Biesheuvel [this message]
2015-04-11  7:35       ` Ard Biesheuvel
2015-04-11  8:48       ` Arnd Bergmann
2015-04-11  8:48         ` Arnd Bergmann
2015-04-11 10:27         ` Ard Biesheuvel
2015-04-11 10:27           ` Ard Biesheuvel
2015-04-11 20:43           ` Arnd Bergmann
2015-04-11 20:43             ` Arnd Bergmann
2015-04-11 19:15         ` Ard Biesheuvel
2015-04-11 19:15           ` Ard Biesheuvel
2015-04-13  4:13           ` Herbert Xu
2015-04-13  4:13             ` Herbert Xu
2015-04-13  9:34             ` Ard Biesheuvel
2015-04-13  9:34               ` Ard Biesheuvel

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