1
0
Fork 0
mirror of https://github.com/Atmosphere-NX/Atmosphere.git synced 2024-12-27 04:36:04 +00:00
Atmosphere/libraries/libmesosphere/include/mesosphere/kern_k_page_bitmap.hpp

291 lines
11 KiB
C++
Raw Normal View History

/*
* Copyright (c) Atmosphère-NX
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include <mesosphere/kern_common.hpp>
#include <mesosphere/kern_select_system_control.hpp>
namespace ams::kern {
class KPageBitmap {
public:
class RandomBitGenerator {
private:
util::TinyMT m_rng;
u32 m_entropy;
u32 m_bits_available;
private:
void RefreshEntropy() {
m_entropy = m_rng.GenerateRandomU32();
m_bits_available = BITSIZEOF(m_entropy);
}
bool GenerateRandomBit() {
if (m_bits_available == 0) {
this->RefreshEntropy();
}
const bool rnd_bit = (m_entropy & 1) != 0;
m_entropy >>= 1;
--m_bits_available;
return rnd_bit;
}
u64 GenerateRandomBits(u32 num_bits) {
u64 result = 0;
/* Iteratively add random bits to our result. */
while (num_bits > 0) {
/* Ensure we have random bits to take from. */
if (m_bits_available == 0) {
this->RefreshEntropy();
}
/* Determine how many bits to take this round. */
const auto cur_bits = std::min(num_bits, m_bits_available);
/* Generate mask for our current bits. */
const u64 mask = (static_cast<u64>(1) << cur_bits) - 1;
/* Add bits to output from our entropy. */
result <<= cur_bits;
result |= (m_entropy & mask);
/* Remove bits from our entropy. */
m_entropy >>= cur_bits;
m_bits_available -= cur_bits;
/* Advance. */
num_bits -= cur_bits;
}
return result;
}
public:
RandomBitGenerator() : m_entropy(), m_bits_available() {
m_rng.Initialize(static_cast<u32>(KSystemControl::GenerateRandomU64()));
}
u64 SelectRandomBit(u64 bitmap) {
u64 selected = 0;
for (size_t cur_num_bits = BITSIZEOF(bitmap) / 2; cur_num_bits != 0; cur_num_bits /= 2) {
const u64 high = (bitmap >> cur_num_bits);
const u64 low = (bitmap & (~(UINT64_C(0xFFFFFFFFFFFFFFFF) << cur_num_bits)));
/* Choose high if we have high and (don't have low or select high randomly). */
if (high && (low == 0 || this->GenerateRandomBit())) {
bitmap = high;
selected += cur_num_bits;
} else {
bitmap = low;
selected += 0;
}
}
return selected;
}
u64 GenerateRandom(u64 max) {
/* Determine the number of bits we need. */
const u64 bits_needed = 1 + (BITSIZEOF(max) - util::CountLeadingZeros(max));
/* Generate a random value of the desired bitwidth. */
const u64 rnd = this->GenerateRandomBits(bits_needed);
/* Adjust the value to be in range. */
return rnd - ((rnd / max) * max);
}
};
public:
static constexpr size_t MaxDepth = 4;
private:
u64 *m_bit_storages[MaxDepth];
RandomBitGenerator m_rng;
size_t m_num_bits;
size_t m_used_depths;
public:
KPageBitmap() : m_bit_storages(), m_rng(), m_num_bits(), m_used_depths() { /* ... */ }
constexpr size_t GetNumBits() const { return m_num_bits; }
constexpr s32 GetHighestDepthIndex() const { return static_cast<s32>(m_used_depths) - 1; }
u64 *Initialize(u64 *storage, size_t size) {
/* Initially, everything is un-set. */
m_num_bits = 0;
/* Calculate the needed bitmap depth. */
m_used_depths = static_cast<size_t>(GetRequiredDepth(size));
MESOSPHERE_ASSERT(m_used_depths <= MaxDepth);
/* Set the bitmap pointers. */
for (s32 depth = this->GetHighestDepthIndex(); depth >= 0; depth--) {
m_bit_storages[depth] = storage;
size = util::AlignUp(size, BITSIZEOF(u64)) / BITSIZEOF(u64);
storage += size;
}
return storage;
}
ssize_t FindFreeBlock(bool random) {
uintptr_t offset = 0;
s32 depth = 0;
if (random) {
do {
const u64 v = m_bit_storages[depth][offset];
if (v == 0) {
/* If depth is bigger than zero, then a previous level indicated a block was free. */
MESOSPHERE_ASSERT(depth == 0);
return -1;
}
offset = offset * BITSIZEOF(u64) + m_rng.SelectRandomBit(v);
++depth;
} while (depth < static_cast<s32>(m_used_depths));
} else {
do {
const u64 v = m_bit_storages[depth][offset];
if (v == 0) {
/* If depth is bigger than zero, then a previous level indicated a block was free. */
MESOSPHERE_ASSERT(depth == 0);
return -1;
}
offset = offset * BITSIZEOF(u64) + __builtin_ctzll(v);
++depth;
} while (depth < static_cast<s32>(m_used_depths));
}
return static_cast<ssize_t>(offset);
}
void SetBit(size_t offset) {
this->SetBit(this->GetHighestDepthIndex(), offset);
m_num_bits++;
}
void ClearBit(size_t offset) {
this->ClearBit(this->GetHighestDepthIndex(), offset);
m_num_bits--;
}
bool ClearRange(size_t offset, size_t count) {
s32 depth = this->GetHighestDepthIndex();
u64 *bits = m_bit_storages[depth];
size_t bit_ind = offset / BITSIZEOF(u64);
if (AMS_LIKELY(count < BITSIZEOF(u64))) {
const size_t shift = offset % BITSIZEOF(u64);
MESOSPHERE_ASSERT(shift + count <= BITSIZEOF(u64));
/* Check that all the bits are set. */
const u64 mask = ((u64(1) << count) - 1) << shift;
u64 v = bits[bit_ind];
if ((v & mask) != mask) {
return false;
}
/* Clear the bits. */
v &= ~mask;
bits[bit_ind] = v;
if (v == 0) {
this->ClearBit(depth - 1, bit_ind);
}
} else {
MESOSPHERE_ASSERT(offset % BITSIZEOF(u64) == 0);
MESOSPHERE_ASSERT(count % BITSIZEOF(u64) == 0);
/* Check that all the bits are set. */
size_t remaining = count;
size_t i = 0;
do {
if (bits[bit_ind + i++] != ~u64(0)) {
return false;
}
remaining -= BITSIZEOF(u64);
} while (remaining > 0);
/* Clear the bits. */
remaining = count;
i = 0;
do {
bits[bit_ind + i] = 0;
this->ClearBit(depth - 1, bit_ind + i);
i++;
remaining -= BITSIZEOF(u64);
} while (remaining > 0);
}
m_num_bits -= count;
return true;
}
private:
void SetBit(s32 depth, size_t offset) {
while (depth >= 0) {
size_t ind = offset / BITSIZEOF(u64);
size_t which = offset % BITSIZEOF(u64);
const u64 mask = u64(1) << which;
u64 *bit = std::addressof(m_bit_storages[depth][ind]);
u64 v = *bit;
MESOSPHERE_ASSERT((v & mask) == 0);
*bit = v | mask;
if (v) {
break;
}
offset = ind;
depth--;
}
}
void ClearBit(s32 depth, size_t offset) {
while (depth >= 0) {
size_t ind = offset / BITSIZEOF(u64);
size_t which = offset % BITSIZEOF(u64);
const u64 mask = u64(1) << which;
u64 *bit = std::addressof(m_bit_storages[depth][ind]);
u64 v = *bit;
MESOSPHERE_ASSERT((v & mask) != 0);
v &= ~mask;
*bit = v;
if (v) {
break;
}
offset = ind;
depth--;
}
}
private:
static constexpr s32 GetRequiredDepth(size_t region_size) {
s32 depth = 0;
while (true) {
region_size /= BITSIZEOF(u64);
depth++;
if (region_size == 0) {
return depth;
}
}
}
public:
static constexpr size_t CalculateManagementOverheadSize(size_t region_size) {
size_t overhead_bits = 0;
for (s32 depth = GetRequiredDepth(region_size) - 1; depth >= 0; depth--) {
region_size = util::AlignUp(region_size, BITSIZEOF(u64)) / BITSIZEOF(u64);
overhead_bits += region_size;
}
return overhead_bits * sizeof(u64);
}
};
}