blob: 367adcf098da136ca14e1014e263c81fda24f20f [file] [log] [blame]
/*
* Copyright (c) 2017 Intel Corporation
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <sys/atomic.h>
#include <kernel.h>
#include <drivers/entropy.h>
#include <string.h>
static const struct device *entropy_driver;
#if defined(CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR)
uint32_t z_impl_sys_rand32_get(void)
{
const struct device *dev = entropy_driver;
uint32_t random_num;
int ret;
if (unlikely(!dev)) {
/* Only one entropy device exists, so this is safe even
* if the whole operation isn't atomic.
*/
dev = device_get_binding(DT_CHOSEN_ZEPHYR_ENTROPY_LABEL);
__ASSERT((dev != NULL),
"Device driver for %s (DT_CHOSEN_ZEPHYR_ENTROPY_LABEL) not found. "
"Check your build configuration!",
DT_CHOSEN_ZEPHYR_ENTROPY_LABEL);
entropy_driver = dev;
}
ret = entropy_get_entropy(dev, (uint8_t *)&random_num,
sizeof(random_num));
if (unlikely(ret < 0)) {
/* Use system timer in case the entropy device couldn't deliver
* 32-bit of data. There's not much that can be done in this
* situation. An __ASSERT() isn't used here as the HWRNG might
* still be gathering entropy during early boot situations.
*/
random_num = k_cycle_get_32();
}
return random_num;
}
#endif /* CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR */
static int rand_get(uint8_t *dst, size_t outlen, bool csrand)
{
const struct device *dev = entropy_driver;
uint32_t random_num;
int ret;
if (unlikely(!dev)) {
/* Only one entropy device exists, so this is safe even
* if the whole operation isn't atomic.
*/
dev = device_get_binding(DT_CHOSEN_ZEPHYR_ENTROPY_LABEL);
__ASSERT((dev != NULL),
"Device driver for %s (DT_CHOSEN_ZEPHYR_ENTROPY_LABEL) not found. "
"Check your build configuration!",
DT_CHOSEN_ZEPHYR_ENTROPY_LABEL);
entropy_driver = dev;
}
ret = entropy_get_entropy(dev, dst, outlen);
if (unlikely(ret < 0)) {
/* Don't try to fill the buffer in case of
* cryptographically secure random numbers, just
* propagate the driver error.
*/
if (csrand) {
return ret;
}
/* Use system timer in case the entropy device couldn't deliver
* 32-bit of data. There's not much that can be done in this
* situation. An __ASSERT() isn't used here as the HWRNG might
* still be gathering entropy during early boot situations.
*/
uint32_t len = 0;
uint32_t blocksize = 4;
while (len < outlen) {
size_t copylen = outlen - len;
if (copylen > blocksize) {
copylen = blocksize;
}
random_num = k_cycle_get_32();
(void)memcpy(&(dst[len]), &random_num, copylen);
len += copylen;
}
}
return 0;
}
#if defined(CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR)
void z_impl_sys_rand_get(void *dst, size_t outlen)
{
rand_get(dst, outlen, false);
}
#endif /* CONFIG_ENTROPY_DEVICE_RANDOM_GENERATOR */
#if defined(CONFIG_HARDWARE_DEVICE_CS_GENERATOR)
int z_impl_sys_csrand_get(void *dst, size_t outlen)
{
if (rand_get(dst, outlen, true) != 0) {
/* Is it the only error it should return ? entropy_sam
* can return -ETIMEDOUT for example
*/
return -EIO;
}
return 0;
}
#endif /* CONFIG_HARDWARE_DEVICE_CS_GENERATOR */