linux-kernel - Re: [PATCH] crypto: more robust crypto

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Message-ID: <5293C88E.9000203@cesarb.eti.br>
Date:	Mon, 25 Nov 2013 20:00:46 -0200
From:	Cesar Eduardo Barros <cesarb@...arb.eti.br>
To:	Daniel Borkmann <dborkman@...hat.com>,
	James Yonan <james@...nvpn.net>
CC:	linux-crypto@...r.kernel.org,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	"David S. Miller" <davem@...emloft.net>,
	Florian Weimer <fw@...eb.enyo.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: more robust crypto_memneq

Em 25-11-2013 14:26, Daniel Borkmann escreveu:
> On 11/25/2013 04:59 PM, James Yonan wrote:
>> This approach using __asm__ ("" : "=r" (var) : "0" (var)) to try to
>> prevent compiler optimizations of var is interesting.
>>
>> I like the fact that it's finer-grained than -Os and doesn't preclude
>> inlining.
>
> Agreed. This looks much better than the Makefile workaround. Do we have
> a hard guarantee that in future, this will not be detected and optimized
> away by the compiler?

That guarantee is something only the compiler people can give you. But 
given that RELOC_HIDE will break if that ever changes, and there are 
other constructs depending on the optimization-blocking behavior of 
inline assembly (like the many kinds of barriers in the kernel), I am 
not worried about that.

-- 
Cesar Eduardo Barros
cesarb@...arb.eti.br
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