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