[RFC][PATCH 2/2] Twofish cipher x86_64-asm optimized

[Joachim Fritschi <jfritschi@freenet.de>]

Implementation:
-----------------------
This code is based on the current linux twofish cipher c implementation. Only 
the decrypt/encrypt routines were replaced by optimized assembler code. The 
in-kernel code by Matthew Skala takes care of the keysetup and precomputation 
of the sbox lookup tables.
I have eliminated stack use, tried to optimize the code as much as possible 
and limit code size. The patch is similar to the existing aes assembler 
implementation.

Testing:
-----------
The code passed the kernel test module and passed automated tests on a 
dm-crypt volume reading/writing large files with alternating modules ( c / 
assembler ) and comparing results. It is also running on my workstation for 
over a week now.

Benchmarks:
-------------------

Performance on a dm-crypt volume increased about 47% while reading. With 
256bit keylength its pretty close to the speed of the aes assembler version.

http://homepages.tu-darmstadt.de/~fritschi/twofish/output_20060426_175710_x86_64.html

The write performance in this benchmark was limited by the harddrive and not 
the algorithm / system speed. Any suggestions how to benchmark the overall 
speed accurately are welcome.


Patch:
----------

http://homepages.tu-darmstadt.de/~fritschi/twofish/twofish-x86_64-asm-2.6.17.diff


Please have a look, try, improve and criticise.

Regards,
Joachim
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