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/*
* QEMU guest-visible random functions
*
* Copyright 2019 Linaro, Ltd.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*/
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include "qapi/error.h"
#include "qemu/guest-random.h"
#include "crypto/random.h"
static __thread GRand *thread_rand;
static bool deterministic;
static int glib_random_bytes(void *buf, size_t len)
{
GRand *rand = thread_rand;
size_t i;
uint32_t x;
if (unlikely(rand == NULL)) {
/* Thread not initialized for a cpu, or main w/o -seed. */
thread_rand = rand = g_rand_new();
}
for (i = 0; i + 4 <= len; i += 4) {
x = g_rand_int(rand);
__builtin_memcpy(buf + i, &x, 4);
}
if (i < len) {
x = g_rand_int(rand);
__builtin_memcpy(buf + i, &x, i - len);
}
return 0;
}
int qemu_guest_getrandom(void *buf, size_t len, Error **errp)
{
if (unlikely(deterministic)) {
/* Deterministic implementation using Glib's Mersenne Twister. */
return glib_random_bytes(buf, len);
} else {
/* Non-deterministic implementation using crypto routines. */
return qcrypto_random_bytes(buf, len, errp);
}
}
void qemu_guest_getrandom_nofail(void *buf, size_t len)
{
(void)qemu_guest_getrandom(buf, len, &error_fatal);
}
uint64_t qemu_guest_random_seed_thread_part1(void)
{
if (deterministic) {
uint64_t ret;
glib_random_bytes(&ret, sizeof(ret));
return ret;
}
return 0;
}
void qemu_guest_random_seed_thread_part2(uint64_t seed)
{
g_assert(thread_rand == NULL);
if (deterministic) {
thread_rand =
g_rand_new_with_seed_array((const guint32 *)&seed,
sizeof(seed) / sizeof(guint32));
}
}
int qemu_guest_random_seed_main(const char *optarg, Error **errp)
{
unsigned long long seed;
if (parse_uint_full(optarg, &seed, 0)) {
error_setg(errp, "Invalid seed number: %s", optarg);
return -1;
} else {
deterministic = true;
qemu_guest_random_seed_thread_part2(seed);
return 0;
}
}
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