From: Pekka Enberg <penberg@cs.helsinki.fi>
To: Mikael Pettersson <mikpe@it.uu.se>
Cc: Roel Kluin <roel.kluin@gmail.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
linux-crypto@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sha: prevent removal of memset as dead store in sha1_update()
Date: Thu, 25 Feb 2010 18:16:59 +0200 [thread overview]
Message-ID: <84144f021002250816o2c2cef0fke484c7e43256dba4@mail.gmail.com> (raw)
In-Reply-To: <19334.40337.651079.440912@pilspetsen.it.uu.se>
On Thu, Feb 25, 2010 at 5:56 PM, Mikael Pettersson <mikpe@it.uu.se> wrote:
> I fear that the only portable (across compiler versions) and safe
> solution is to invoke an assembly-coded dummy function with prototype
>
> void use(void *p);
>
> and rewrite the code above as
>
> {
> u32 temp[...];
> ...
> memset(temp, 0, sizeof temp);
> use(temp);
> }
>
> This forces the compiler to consider the buffer live after the
> memset, so the memset cannot be eliminated.
So is there some "do not optimize" GCC magic that we could use for a
memzero_secret() helper function?
Pekka
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next prev parent reply other threads:[~2010-02-25 16:17 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-25 15:10 [PATCH] sha: prevent removal of memset as dead store in sha1_update() Roel Kluin
2010-02-25 15:17 ` David Miller
2010-02-25 15:31 ` roel kluin
2010-02-25 15:37 ` David Miller
2010-02-26 11:55 ` Andi Kleen
2010-02-26 14:20 ` Mikael Pettersson
2010-02-26 15:46 ` Mikael Pettersson
2010-02-26 15:55 ` Andi Kleen
2010-02-25 15:56 ` Mikael Pettersson
2010-02-25 16:16 ` Pekka Enberg [this message]
2010-02-25 16:29 ` Mikael Pettersson
2010-02-25 16:33 ` roel kluin
2010-02-25 17:06 ` roel kluin
2010-02-25 16:33 ` Brian Gerst
2010-02-25 17:09 ` Mikael Pettersson
2010-02-25 17:32 ` Brian Gerst
2010-02-25 19:47 ` Roel Kluin
2010-02-25 20:43 ` Roel Kluin
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