1 /* SPDX-License-Identifier: GPL-2.0 */
3 * include/linux/prandom.h
5 * Include file for the fast pseudo-random 32-bit
8 #ifndef _LINUX_PRANDOM_H
9 #define _LINUX_PRANDOM_H
11 #include <linux/types.h>
12 #include <linux/once.h>
13 #include <linux/percpu.h>
14 #include <linux/random.h>
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);
24 #define prandom_init_once(pcpu_state) \
25 DO_ONCE(prandom_seed_full_state, (pcpu_state))
27 /* Deprecated: use get_random_u32_below() instead. */
28 static inline u32 prandom_u32_max(u32 ep_ro)
30 return get_random_u32_below(ep_ro);
34 * Handle minimum values for seeds
36 static inline u32 __seed(u32 x, u32 m)
38 return (x < m) ? x + m : x;
42 * prandom_seed_state - set seed for prandom_u32_state().
43 * @state: pointer to state structure to receive the seed.
44 * @seed: arbitrary 64-bit value to use as a seed.
46 static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
48 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
50 state->s1 = __seed(i, 2U);
51 state->s2 = __seed(i, 8U);
52 state->s3 = __seed(i, 16U);
53 state->s4 = __seed(i, 128U);
56 /* Pseudo random number generator from numerical recipes. */
57 static inline u32 next_pseudo_random32(u32 seed)
59 return seed * 1664525 + 1013904223;