From: Stephan Mueller <smueller@chronox.de>
Subject: Re: [BUG/PATCH] kernel RNG and its secrets
Date: Mon, 27 Apr 2015 22:41:56 +0200
Message-ID: <3111959.ZXZJYjVLIH@myon.chronox.de>
References: <20150318095345.GA12923@zoho.com> <11353383.zL7vZDIZ69@tauon> <553E9D56.1020202@iogearbox.net>
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Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>,
	mancha <mancha1@zoho.com>, tytso@mit.edu,
	linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
	herbert@gondor.apana.org.au, dborkman@redhat.com
To: Daniel Borkmann <daniel@iogearbox.net>
In-Reply-To: <553E9D56.1020202@iogearbox.net>
Sender: linux-crypto-owner@vger.kernel.org

Am Montag, 27. April 2015, 22:34:30 schrieb Daniel Borkmann:

Hi Daniel,

> On 04/27/2015 09:10 PM, Stephan Mueller wrote:
> ...
> 
> > I posted the issue on the clang mailing list on April 10 -- no word so
> > far. I would interpret this as a sign that it is a no-issue for them.
> 
> Hm. ;)
> 
> Here's a bug report on the topic, gcc vs llvm:
> 
>    https://llvm.org/bugs/show_bug.cgi?id=15495
> 
> Lets add a new barrier macro to linux/compiler{,-gcc}.h, f.e.
> 
>    #define barrier_data(ptr) __asm__ __volatile__("" : : "r" (ptr) :
> "memory")
> 
> or the version Mancha proposed. You could wrap that ...
> 
>    #define OPTIMIZER_HIDE(ptr)   barrier_data(ptr)
> 
> ... and use that one for memzero_explicit() instead:
> 
>    void memzero_explicit(void *s, size_t count)
>    {
>       memset(s, 0, count);
>       OPTIMIZER_HIDE(s);
>    }
> 
> It certainly needs comments explaining in what situations to use
> which OPTIMIZER_HIDE* variants, etc.
> 
> Do you want to send a patch?

It seems you have the code already in mind, so please if you could write it 
:-)

-- 
Ciao
Stephan