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lib/random32.c: minor cleanups and kdoc fix

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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: Daniel Borkmann <dborkman@redhat.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Daniel Borkmann 2014-04-03 14:49:08 -07:00 committed by Linus Torvalds
parent b104d6a5a8
commit d3d47eb265
1 changed files with 39 additions and 37 deletions
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76
lib/random32.c
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@ -1,37 +1,35 @@
/*
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>
#include <linux/percpu.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) {