blob: 74ca676098b6250f84cf04ffb9313128942b9d08 [file] [log] [blame]
/*
* Copyright (c) 2013-2015 Wind River Systems, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
* @brief Non-random number generator based on system timer
*
* This module provides a non-random implementation of sys_rand32_get(), which
* is not meant to be used in a final product as a truly random number
* generator. It was provided to allow testing on a platform that does not (yet)
* provide a random number generator.
*/
#include <zephyr/random/random.h>
#include <zephyr/drivers/timer/system_timer.h>
#include <zephyr/kernel.h>
#include <zephyr/spinlock.h>
#include <string.h>
#if defined(__GNUC__)
static struct k_spinlock rand32_lock;
/**
* @brief Get a 32 bit random number
*
* This pseudo-random number generator returns values that are based off the
* target's clock counter, which means that successive calls will return
* different values.
*
* @return a 32-bit number
*/
static inline uint32_t rand32_get(void)
{
/* initial seed value */
static uint64_t state = (uint64_t)CONFIG_TIMER_RANDOM_INITIAL_STATE;
k_spinlock_key_t key = k_spin_lock(&rand32_lock);
state = state + k_cycle_get_32();
state = state * 2862933555777941757ULL + 3037000493ULL;
uint32_t val = (uint32_t)(state >> 32);
k_spin_unlock(&rand32_lock, key);
return val;
}
/**
* @brief Fill destination buffer with random numbers
*
* The pseudo-random number generator returns values that are based off the
* target's clock counter, which means that successive calls will return
* different values.
*
* @param dst destination buffer to fill
* @param outlen size of destination buffer to fill
*/
void z_impl_sys_rand_get(void *dst, size_t outlen)
{
uint8_t *udst = dst;
uint32_t blocksize;
uint32_t ret;
while (outlen > 0) {
ret = rand32_get();
blocksize = MIN(outlen, sizeof(ret));
(void)memcpy((void *)udst, &ret, blocksize);
udst += blocksize;
outlen -= blocksize;
}
}
#endif /* __GNUC__ */