Messages in this thread | | | Date | Mon, 08 Jun 2015 21:31:54 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH] crypto: drbg - use pragmas for disabling optimization |
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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 <smueller@chronox.de>
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
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