include/linux/prandom.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * include/linux/prandom.h
   4  *
   5  * Include file for the fast pseudo-random 32-bit
   6  * generation.
   7  */
   8 #ifndef _LINUX_PRANDOM_H
   9 #define _LINUX_PRANDOM_H
  10
  11 #include <linux/types.h>
  12 #include <linux/once.h>
  13 #include <linux/percpu.h>
  14 #include <linux/random.h>
  15
  16 struct rnd_state {
  17         __u32 s1, s2, s3, s4;
  18 };
  19
  20 u32 prandom_u32_state(struct rnd_state *state);
  21 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
  22 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
  23
  24 #define prandom_init_once(pcpu_state)                   \
  25         DO_ONCE(prandom_seed_full_state, (pcpu_state))
  26
  27 /*
  28  * Handle minimum values for seeds
  29  */
  30 static inline u32 __seed(u32 x, u32 m)
  31 {
  32         return (x < m) ? x + m : x;
  33 }
  34
  35 /**
  36  * prandom_seed_state - set seed for prandom_u32_state().
  37  * @state: pointer to state structure to receive the seed.
  38  * @seed: arbitrary 64-bit value to use as a seed.
  39  */
  40 static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
  41 {
  42         u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
  43
  44         state->s1 = __seed(i,   2U);
  45         state->s2 = __seed(i,   8U);
  46         state->s3 = __seed(i,  16U);
  47         state->s4 = __seed(i, 128U);
  48 }
  49
  50 /* Pseudo random number generator from numerical recipes. */
  51 static inline u32 next_pseudo_random32(u32 seed)
  52 {
  53         return seed * 1664525 + 1013904223;
  54 }
  55
  56 #endif