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129 lines
3.7 KiB
129 lines
3.7 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* include/linux/prandom.h |
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* |
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* Include file for the fast pseudo-random 32-bit |
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* generation. |
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*/ |
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#ifndef _LINUX_PRANDOM_H |
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#define _LINUX_PRANDOM_H |
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#include <linux/types.h> |
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#include <linux/percpu.h> |
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u32 prandom_u32(void); |
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void prandom_bytes(void *buf, size_t nbytes); |
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void prandom_seed(u32 seed); |
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void prandom_reseed_late(void); |
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DECLARE_PER_CPU(unsigned long, net_rand_noise); |
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#define PRANDOM_ADD_NOISE(a, b, c, d) \ |
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prandom_u32_add_noise((unsigned long)(a), (unsigned long)(b), \ |
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(unsigned long)(c), (unsigned long)(d)) |
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#if BITS_PER_LONG == 64 |
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/* |
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* The core SipHash round function. Each line can be executed in |
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* parallel given enough CPU resources. |
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*/ |
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#define PRND_SIPROUND(v0, v1, v2, v3) ( \ |
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v0 += v1, v1 = rol64(v1, 13), v2 += v3, v3 = rol64(v3, 16), \ |
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v1 ^= v0, v0 = rol64(v0, 32), v3 ^= v2, \ |
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v0 += v3, v3 = rol64(v3, 21), v2 += v1, v1 = rol64(v1, 17), \ |
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v3 ^= v0, v1 ^= v2, v2 = rol64(v2, 32) \ |
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) |
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#define PRND_K0 (0x736f6d6570736575 ^ 0x6c7967656e657261) |
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#define PRND_K1 (0x646f72616e646f6d ^ 0x7465646279746573) |
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#elif BITS_PER_LONG == 32 |
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/* |
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* On 32-bit machines, we use HSipHash, a reduced-width version of SipHash. |
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* This is weaker, but 32-bit machines are not used for high-traffic |
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* applications, so there is less output for an attacker to analyze. |
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*/ |
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#define PRND_SIPROUND(v0, v1, v2, v3) ( \ |
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v0 += v1, v1 = rol32(v1, 5), v2 += v3, v3 = rol32(v3, 8), \ |
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v1 ^= v0, v0 = rol32(v0, 16), v3 ^= v2, \ |
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v0 += v3, v3 = rol32(v3, 7), v2 += v1, v1 = rol32(v1, 13), \ |
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v3 ^= v0, v1 ^= v2, v2 = rol32(v2, 16) \ |
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) |
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#define PRND_K0 0x6c796765 |
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#define PRND_K1 0x74656462 |
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#else |
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#error Unsupported BITS_PER_LONG |
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#endif |
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static inline void prandom_u32_add_noise(unsigned long a, unsigned long b, |
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unsigned long c, unsigned long d) |
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{ |
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/* |
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* This is not used cryptographically; it's just |
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* a convenient 4-word hash function. (3 xor, 2 add, 2 rol) |
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*/ |
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a ^= raw_cpu_read(net_rand_noise); |
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PRND_SIPROUND(a, b, c, d); |
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raw_cpu_write(net_rand_noise, d); |
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} |
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struct rnd_state { |
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__u32 s1, s2, s3, s4; |
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}; |
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u32 prandom_u32_state(struct rnd_state *state); |
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void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); |
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void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state); |
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#define prandom_init_once(pcpu_state) \ |
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DO_ONCE(prandom_seed_full_state, (pcpu_state)) |
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/** |
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* prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro) |
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* @ep_ro: right open interval endpoint |
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* |
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* Returns a pseudo-random number that is in interval [0, ep_ro). Note |
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* that the result depends on PRNG being well distributed in [0, ~0U] |
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* u32 space. Here we use maximally equidistributed combined Tausworthe |
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* generator, that is, prandom_u32(). This is useful when requesting a |
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* random index of an array containing ep_ro elements, for example. |
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* |
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* Returns: pseudo-random number in interval [0, ep_ro) |
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*/ |
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static inline u32 prandom_u32_max(u32 ep_ro) |
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{ |
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return (u32)(((u64) prandom_u32() * ep_ro) >> 32); |
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} |
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/* |
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* Handle minimum values for seeds |
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*/ |
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static inline u32 __seed(u32 x, u32 m) |
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{ |
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return (x < m) ? x + m : x; |
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} |
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/** |
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* prandom_seed_state - set seed for prandom_u32_state(). |
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* @state: pointer to state structure to receive the seed. |
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* @seed: arbitrary 64-bit value to use as a seed. |
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*/ |
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static inline void prandom_seed_state(struct rnd_state *state, u64 seed) |
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{ |
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u32 i = (seed >> 32) ^ (seed << 10) ^ seed; |
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state->s1 = __seed(i, 2U); |
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state->s2 = __seed(i, 8U); |
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state->s3 = __seed(i, 16U); |
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state->s4 = __seed(i, 128U); |
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PRANDOM_ADD_NOISE(state, i, 0, 0); |
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} |
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/* Pseudo random number generator from numerical recipes. */ |
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static inline u32 next_pseudo_random32(u32 seed) |
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{ |
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return seed * 1664525 + 1013904223; |
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} |
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#endif
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