forked from SerenityOS/serenity
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Random.cpp
142 lines (126 loc) Β· 4.73 KB
/
Random.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
/*
* Copyright (c) 2018-2020, Andreas Kling <[email protected]>
* Copyright (c) 2020, Peter Elliott <[email protected]>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/Singleton.h>
#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/Devices/RandomDevice.h>
#include <Kernel/Random.h>
#include <Kernel/Time/HPET.h>
#include <Kernel/Time/RTC.h>
#include <Kernel/Time/TimeManagement.h>
namespace Kernel {
static AK::Singleton<KernelRng> s_the;
KernelRng& KernelRng::the()
{
return *s_the;
}
KernelRng::KernelRng()
{
bool supports_rdseed = Processor::current().has_feature(CPUFeature::RDSEED);
bool supports_rdrand = Processor::current().has_feature(CPUFeature::RDRAND);
if (supports_rdseed || supports_rdrand) {
klog() << "KernelRng: Using RDSEED or RDRAND as entropy source";
for (size_t i = 0; i < resource().pool_count * resource().reseed_threshold; ++i) {
u32 value = 0;
if (supports_rdseed) {
asm volatile(
"1:\n"
"rdseed %0\n"
"jnc 1b\n"
: "=r"(value));
} else {
asm volatile(
"1:\n"
"rdrand %0\n"
"jnc 1b\n"
: "=r"(value));
}
this->resource().add_random_event(value, i % 32);
}
} else if (TimeManagement::the().can_query_precise_time()) {
// Add HPET as entropy source if we don't have anything better.
klog() << "KernelRng: Using HPET as entropy source";
for (size_t i = 0; i < resource().pool_count * resource().reseed_threshold; ++i) {
u64 hpet_time = HPET::the().read_main_counter();
this->resource().add_random_event(hpet_time, i % 32);
}
} else {
// Fallback to RTC
klog() << "KernelRng: Using RTC as entropy source (bad!)";
time_t current_time = RTC::now();
for (size_t i = 0; i < resource().pool_count * resource().reseed_threshold; ++i) {
this->resource().add_random_event(current_time, i % 32);
current_time *= 0x574a;
current_time += 0x40b2;
}
}
}
void KernelRng::wait_for_entropy()
{
if (!resource().is_ready()) {
dbgln("Entropy starvation...");
m_seed_queue.wait_on({}, "KernelRng");
}
}
void KernelRng::wake_if_ready()
{
if (resource().is_ready()) {
m_seed_queue.wake_all();
}
}
size_t EntropySource::next_source { static_cast<size_t>(EntropySource::Static::MaxHardcodedSourceIndex) };
void get_good_random_bytes(u8* buffer, size_t buffer_size)
{
KernelRng::the().wait_for_entropy();
// FIXME: What if interrupts are disabled because we're in an interrupt?
if (are_interrupts_enabled()) {
LOCKER(KernelRng::the().lock());
KernelRng::the().resource().get_random_bytes(buffer, buffer_size);
} else {
KernelRng::the().resource().get_random_bytes(buffer, buffer_size);
}
}
void get_fast_random_bytes(u8* buffer, size_t buffer_size)
{
if (KernelRng::the().resource().is_ready()) {
return get_good_random_bytes(buffer, buffer_size);
}
static u32 next = 1;
union {
u8 bytes[4];
u32 value;
} u;
size_t offset = 4;
for (size_t i = 0; i < buffer_size; ++i) {
if (offset >= 4) {
next = next * 1103515245 + 12345;
u.value = next;
offset = 0;
}
buffer[i] = u.bytes[offset++];
}
}
}