6216c6cf5b
Create syscalls to make possible using random APIs from user mode threads. These APIs can have different implementations, like using entropy driver or Xoroshiro128. Some of these implementations also have some globals to preserve state between calls. Make it run entire in user space would require user adding these globals to their memeory domains and/or grant access to entropy device. Syscalls simplify its usage. Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
122 lines
3.2 KiB
C
122 lines
3.2 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation
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*
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* SPDX-License-Identifier: CC0-1.0
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*
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* Based on code written in 2016 by David Blackman and Sebastiano Vigna
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* (vigna@acm.org)
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*
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* To the extent possible under law, the author has dedicated all copyright
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* and related and neighboring rights to this software to the public domain
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* worldwide. This software is distributed without any warranty.
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*
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* See <http://creativecommons.org/publicdomain/zero/1.0/>.
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*/
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/* This is the successor to xorshift128+. It is the fastest full-period
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* generator passing BigCrush without systematic failures, but due to the
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* relatively short period it is acceptable only for applications with a
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* mild amount of parallelism; otherwise, use a xorshift1024* generator.
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*
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* Beside passing BigCrush, this generator passes the PractRand test suite
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* up to (and included) 16TB, with the exception of binary rank tests, as
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* the lowest bit of this generator is an LSFR. The next bit is not an
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* LFSR, but in the long run it will fail binary rank tests, too. The
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* other bits have no LFSR artifacts.
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*
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* We suggest to use a sign test to extract a random Boolean value, and
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* right shifts to extract subsets of bits.
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*
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* Note that the generator uses a simulated rotate operation, which most C
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* compilers will turn into a single instruction. In Java, you can use
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* Long.rotateLeft(). In languages that do not make low-level rotation
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* instructions accessible xorshift128+ could be faster.
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*
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* The state must be seeded so that it is not everywhere zero. If you have
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* a 64-bit seed, we suggest to seed a splitmix64 generator and use its
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* output to fill s.
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*/
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#include <init.h>
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#include <device.h>
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#include <drivers/entropy.h>
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#include <kernel.h>
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#include <string.h>
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static uint64_t state[2];
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static inline uint64_t rotl(const uint64_t x, int k)
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{
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return (x << k) | (x >> (64 - k));
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}
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static int xoroshiro128_initialize(struct device *dev)
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{
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dev = device_get_binding(DT_CHOSEN_ZEPHYR_ENTROPY_LABEL);
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if (!dev) {
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return -EINVAL;
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}
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int32_t rc = entropy_get_entropy_isr(dev, (uint8_t *)&state,
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sizeof(state), ENTROPY_BUSYWAIT);
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if (rc == -ENOTSUP) {
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/* Driver does not provide an ISR-specific API, assume it can
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* be called from ISR context
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*/
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rc = entropy_get_entropy(dev, (uint8_t *)&state, sizeof(state));
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}
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if (rc < 0) {
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return -EINVAL;
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}
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return 0;
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}
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static uint32_t xoroshiro128_next(void)
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{
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const uint64_t s0 = state[0];
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uint64_t s1 = state[1];
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const uint64_t result = s0 + s1;
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s1 ^= s0;
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state[0] = rotl(s0, 55) ^ s1 ^ (s1 << 14);
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state[1] = rotl(s1, 36);
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return (uint32_t)result;
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}
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uint32_t z_impl_sys_rand32_get(void)
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{
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uint32_t ret;
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ret = xoroshiro128_next();
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return ret;
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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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uint32_t ret;
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uint32_t blocksize = 4;
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uint32_t len = 0;
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uint32_t *udst = (uint32_t *)dst;
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while (len < outlen) {
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ret = xoroshiro128_next();
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if ((outlen-len) < sizeof(ret)) {
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blocksize = len;
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(void)memcpy(udst, &ret, blocksize);
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} else {
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(*udst++) = ret;
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}
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len += blocksize;
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}
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}
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/* In-tree entropy drivers will initialize in PRE_KERNEL_1; ensure that they're
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* initialized properly before initializing ourselves.
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*/
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SYS_INIT(xoroshiro128_initialize, PRE_KERNEL_2,
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CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
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