From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH] crypto: drbg - use pragmas for disabling optimization Date: Mon, 08 Jun 2015 21:31:54 -0700 Message-ID: <55766C3A.3070101@roeck-us.net> References: <3181127.KGS6GDHCq6@tachyon.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <3181127.KGS6GDHCq6@tachyon.chronox.de> Sender: linux-crypto-owner@vger.kernel.org To: Stephan Mueller , herbert@gondor.apana.org.au Cc: Peter Zijlstra , Andy Shevchenko , Jim Davis , Stephen Rothwell , Linux-Next , linux-kernel@vger.kernel.org, "David S. Miller" , linux-crypto@vger.kernel.org, Waiman Long , Ingo Molnar , x86 List-Id: linux-next.vger.kernel.org On 06/08/2015 07:08 PM, Stephan Mueller wrote: > Hi, > > I performed measurements of the upper and lower boundary of the minimum and > Shannon entropy for the RNG before the patch and after the patch. The values > are very similar which demonstrates that the change does not affect the > cryptographic characteristics of the RNG. > > The tests are available at: > > [1] shows the lower boundary of the fully non-optimized RNG > > [2] shows the lower boundary of the RNG with the patch below > > [3] shows the upper boundary of the fully non-optimized RNG > > [4] shows the upper boundary of the RNG with the patch below > > The pictures are fully explained in [5], but the key values are the minimum > and Shannon entropy numbers in the legend of the graphs. > > [1] http://www.eperm.de/userspace-foldtime-testO0.data-single-time-dist-delta-3036-hist.pdf > > [2] http://www.eperm.de/userspace-foldtime-test-pragmas-O2.data-single-time-dist-delta-2370-hist.pdf > > [3] http://www.eperm.de/userspace-foldtime-testO0.data-varying-time-dist-delta-7302-hist.pdf > > [4] http://www.eperm.de/userspace-foldtime-test-pragmas-O2.data-varying-time-dist-delta-7055-hist.pdf > > [5] http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.pdf > > ---8<--- > Replace the global -O0 compiler flag from the Makefile with GCC > pragmas to mark only the functions required to be compiled without > optimizations. > > This patch also adds a comment describing the rationale for the > functions chosen to be compiled without optimizations. > > Signed-off-by: Stephan Mueller With openrisc, I get: CC [M] crypto/jitterentropy.o crypto/jitterentropy.c:266:9: warning: #pragma GCC target is not supported for this machine which may not be perfect, but is better than a compile error ;-). nios2 still fails to build with ERROR: "get_cycles" [crypto/jitterentropy.ko] undefined! Guenter