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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
* 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 <Kernel/Arch/i386/CPU.h>
#include <Kernel/Devices/RandomDevice.h>
#include <Kernel/Random.h>
#include <Kernel/Time/TimeManagement.h>
namespace Kernel {
static KernelRng* s_the;
KernelRng& KernelRng::the()
{
if (!s_the) {
s_the = new KernelRng;
}
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) {
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);
}
}
}
void KernelRng::wait_for_entropy()
{
if (!resource().is_ready()) {
Thread::current()->wait_on(m_seed_queue, "KernelRng");
}
}
void KernelRng::wake_if_ready()
{
if (resource().is_ready()) {
m_seed_queue.wake_all();
}
}
size_t EntropySource::next_source { 0 };
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++];
}
}
}
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