Commit d3d47eb2 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Linus Torvalds
Browse files

lib/random32.c: minor cleanups and kdoc fix 



These are just some very minor and misc cleanups in the PRNG.  In
prandom_u32() we store the result in an unsigned long which is
unnecessary as it should be u32 instead that we get from
prandom_u32_state().  prandom_bytes_state()'s comment is in kdoc format,
so change it into such as it's done everywhere else.  Also, use the
normal comment style for the header comment.  Last but not least for
readability, add some newlines.

Signed-off-by: default avatarDaniel Borkmann <dborkman@redhat.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b104d6a5

lib/random32.c

+39 −37
Original line number Diff line number Diff line 
/*

  This is a maximally equidistributed combined Tausworthe generator

  based on code from GNU Scientific Library 1.5 (30 Jun 2004)



  lfsr113 version:



   x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)



   s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n <<  6) ^ s1_n) >> 13))

   s2_{n+1} = (((s2_n & 4294967288) <<  2) ^ (((s2_n <<  2) ^ s2_n) >> 27))

   s3_{n+1} = (((s3_n & 4294967280) <<  7) ^ (((s3_n << 13) ^ s3_n) >> 21))

   s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n <<  3) ^ s4_n) >> 12))



   The period of this generator is about 2^113 (see erratum paper).



   From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe

   Generators", Mathematics of Computation, 65, 213 (1996), 203--213:

   http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps

   ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps



   There is an erratum in the paper "Tables of Maximally

   Equidistributed Combined LFSR Generators", Mathematics of

   Computation, 68, 225 (1999), 261--269:

   http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps



        ... the k_j most significant bits of z_j must be non-

        zero, for each j. (Note: this restriction also applies to the

        computer code given in [4], but was mistakenly not mentioned in

        that paper.)



   This affects the seeding procedure by imposing the requirement

   s1 > 1, s2 > 7, s3 > 15, s4 > 127.



 * This is a maximally equidistributed combined Tausworthe generator

 * based on code from GNU Scientific Library 1.5 (30 Jun 2004)

 *

 * lfsr113 version:

 *

 * x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)

 *

 * s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n <<  6) ^ s1_n) >> 13))

 * s2_{n+1} = (((s2_n & 4294967288) <<  2) ^ (((s2_n <<  2) ^ s2_n) >> 27))

 * s3_{n+1} = (((s3_n & 4294967280) <<  7) ^ (((s3_n << 13) ^ s3_n) >> 21))

 * s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n <<  3) ^ s4_n) >> 12))

 *

 * The period of this generator is about 2^113 (see erratum paper).

 *

 * From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe

 * Generators", Mathematics of Computation, 65, 213 (1996), 203--213:

 * http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps

 * ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps

 *

 * There is an erratum in the paper "Tables of Maximally Equidistributed

 * Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999),

 * 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps

 *

 *      ... the k_j most significant bits of z_j must be non-zero,

 *      for each j. (Note: this restriction also applies to the

 *      computer code given in [4], but was mistakenly not mentioned

 *      in that paper.)

 *

 * This affects the seeding procedure by imposing the requirement

 * s1 > 1, s2 > 7, s3 > 15, s4 > 127.

 */



#include <linux/types.h>
@@ -75,15 +73,17 @@ EXPORT_SYMBOL(prandom_u32_state); 
 */

u32 prandom_u32(void)

{

	unsigned long r;

	struct rnd_state *state = &get_cpu_var(net_rand_state);

	r = prandom_u32_state(state);

	u32 res;



	res = prandom_u32_state(state);

	put_cpu_var(state);

	return r;



	return res;

}

EXPORT_SYMBOL(prandom_u32);



/*

/**

 *	prandom_bytes_state - get the requested number of pseudo-random bytes

 *

 *	@state: pointer to state structure holding seeded state.
@@ -204,6 +204,7 @@ static int __init prandom_init(void) 
		prandom_seed_very_weak(state, (i + jiffies) ^ random_get_entropy());

		prandom_warmup(state);

	}



	return 0;

}

core_initcall(prandom_init);
@@ -259,6 +260,7 @@ static void __prandom_reseed(bool late) 


	if (latch && !late)

		goto out;



	latch = true;



	for_each_possible_cpu(i) {

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