diff options
Diffstat (limited to 'lib/random32.c')
| -rw-r--r-- | lib/random32.c | 89 |
1 files changed, 51 insertions, 38 deletions
diff --git a/lib/random32.c b/lib/random32.c index 1e5b2df4429..fa5da61ce7a 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -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); @@ -244,10 +245,22 @@ static void __prandom_reseed(bool late) static bool latch = false; static DEFINE_SPINLOCK(lock); + /* Asking for random bytes might result in bytes getting + * moved into the nonblocking pool and thus marking it + * as initialized. In this case we would double back into + * this function and attempt to do a late reseed. + * Ignore the pointless attempt to reseed again if we're + * already waiting for bytes when the nonblocking pool + * got initialized. + */ + /* only allow initial seeding (late == false) once */ - spin_lock_irqsave(&lock, flags); + if (!spin_trylock_irqsave(&lock, flags)) + return; + if (latch && !late) goto out; + latch = true; for_each_possible_cpu(i) { |