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Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright notice, this
9 * list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
23 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include <Kernel/Arch/i386/CPU.h>
28#include <Kernel/Devices/RandomDevice.h>
29#include <Kernel/Random.h>
30
31namespace Kernel {
32
33static u32 random32()
34{
35 if (g_cpu_supports_rdrand) {
36 u32 value = 0;
37 asm volatile(
38 "1%=:\n"
39 "rdrand %0\n"
40 "jnc 1%=\n"
41 : "=r"(value));
42 return value;
43 }
44 // FIXME: This sucks lol
45 static u32 next = 1;
46 next = next * 1103515245 + 12345;
47 return next;
48}
49
50void get_good_random_bytes(u8* buffer, size_t buffer_size)
51{
52 union {
53 u8 bytes[4];
54 u32 value;
55 } u;
56 size_t offset = 4;
57 for (size_t i = 0; i < buffer_size; ++i) {
58 if (offset >= 4) {
59 u.value = random32();
60 offset = 0;
61 }
62 buffer[i] = u.bytes[offset++];
63 }
64}
65
66void get_fast_random_bytes(u8* buffer, size_t buffer_size)
67{
68 return get_good_random_bytes(buffer, buffer_size);
69}
70
71}