linux-kernel - Re: [Y2038] [PATCH v2] crypto: Jitter RNG

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Date:	Wed, 22 Jun 2016 22:16:03 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	y2038@...ts.linaro.org
Cc:	Stephan Mueller <smueller@...onox.de>, herbert@...dor.apana.org.au,
	John Stultz <john.stultz@...aro.org>,
	Kees Cook <keescook@...omium.org>,
	Alexander Kuleshov <kuleshovmail@...il.com>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [Y2038] [PATCH v2] crypto: Jitter RNG - use ktime_get_ns as fallback

On Wednesday, June 22, 2016 7:26:06 PM CEST Stephan Mueller wrote:
> As part of the Y2038 development, __getnstimeofday is not supposed to be
> used any more. It is now replaced with ktime_get_ns. The Jitter RNG uses
> the time stamp to measure the execution time of a given code path and
> tries to detect variations in the execution time. Therefore, the only
> requirement the Jitter RNG has, is a sufficient high resolution to
> detect these variations.
> 
> The change was tested on x86 to show an identical behavior as RDTSC. The
> used test code simply measures the execution time of the heart of the
> RNG:
> 
>         jent_get_nstime(&time);
>         jent_memaccess(ec, min);
>         jent_fold_time(NULL, time, &folded, min);
>         jent_get_nstime(&time2);
>         return ((time2 - time));
> 
> Signed-off-by: Stephan Mueller <smueller@...onox.de>
> ---
> 

Acked-by: Arnd Bergmann <arnd@...db.de>