RE: [PATCH 2/3] sha512: reduce stack usage to safe number

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Le lundi 16 janvier 2012 à 09:56 +0000, David Laight a écrit :
> Doesn't this badly overflow W[] ..
>  
> > +#define SHA512_0_15(i, a, b, c, d, e, f, g, h) \
> > +	t1 = h + e1(e) + Ch(e, f, g) + sha512_K[i] + W[i];	\
> ...
> > +	for (i = 0; i < 16; i += 8) {
> ...
> > +		SHA512_0_15(i + 7, b, c, d, e, f, g, h, a);
> > +	}
> 
> 	David
> 
> 

No overflow since loop is done for only i=0 and i=8

By the way, I suspect previous code was chosen years ago because this
version uses less stack but adds much more code bloat.


size crypto/sha512_generic.o crypto/sha512_generic_old.o
   text	   data	    bss	    dec	    hex	filename
  17369	    704	      0	  18073	   4699	crypto/sha512_generic.o
   8249	    704	      0	   8953	   22f9	crypto/sha512_generic_old.o



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