qemu/util/guest-random.c
Eric Blake bd1386cce1 cutils: Adjust signature of parse_uint[_full]
It's already confusing that we have two very similar functions for
wrapping the parse of a 64-bit unsigned value, differing mainly on
whether they permit leading '-'.  Adjust the signature of parse_uint()
and parse_uint_full() to be like all of qemu_strto*(): put the result
parameter last, use the same types (uint64_t and unsigned long long
have the same width, but are not always the same type), and mark
endptr const (this latter change only affects the rare caller of
parse_uint).  Adjust all callers in the tree.

While at it, note that since cutils.c already includes:

    QEMU_BUILD_BUG_ON(sizeof(int64_t) != sizeof(long long));

we are guaranteed that the result of parse_uint* cannot exceed
UINT64_MAX (or the build would have failed), so we can drop
pre-existing dead comparisons in opts-visitor.c that were never false.

Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20230522190441.64278-8-eblake@redhat.com>
[eblake: Drop dead code spotted by Markus]
Signed-off-by: Eric Blake <eblake@redhat.com>
2023-06-02 12:27:19 -05:00

102 lines
2.5 KiB
C

/*
* 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"
#include "exec/replay-core.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, len - i);
}
return 0;
}
int qemu_guest_getrandom(void *buf, size_t len, Error **errp)
{
int ret;
if (replay_mode == REPLAY_MODE_PLAY) {
return replay_read_random(buf, len);
}
if (unlikely(deterministic)) {
/* Deterministic implementation using Glib's Mersenne Twister. */
ret = glib_random_bytes(buf, len);
} else {
/* Non-deterministic implementation using crypto routines. */
ret = qcrypto_random_bytes(buf, len, errp);
}
if (replay_mode == REPLAY_MODE_RECORD) {
replay_save_random(ret, buf, len);
}
return ret;
}
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)
{
uint64_t seed;
if (parse_uint_full(optarg, 0, &seed)) {
error_setg(errp, "Invalid seed number: %s", optarg);
return -1;
} else {
deterministic = true;
qemu_guest_random_seed_thread_part2(seed);
return 0;
}
}