Re: Patch 4/6 randomize the stack pointer

[Julien TINNES <julien.tinnes.NOSPAM@xxxxxxxxxxxxxxxxxxxxxxxx>]

Horst von Brand wrote:
> Julien TINNES <julien.tinnes.NOSPAM@xxxxxxxxxxxxxxxxxxxxxxxx> said:
>
> > Not very important but ((get_random_int() % 4096) << 4) could be 
> > optimized into get_random_int() & 0xFFF0.
>
>
> Check first if the compiler doesn't do it by itself.

The compiler cannot guess that get_random_int() gives a random result. 
%4096 and & 0xFFF is'nt the same operation. But (get_random_int() % 
4096) and (get_random_int() & 0xFFF) gives the same result: a random 
number between 0 and 4095, without loss of entropy because 0xFFF has no 
0 bit.

--
Julien TINNES - & france telecom - R&D Division/MAPS/NSS
Research Engineer - Internet/Intranet Security
GPG: C050 EF1A 2919 FD87 57C4 DEDD E778 A9F0 14B9 C7D6
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