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// SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include <array>
#include <bit>
#include "common/alignment.h"
#include "common/assert.h"
#include "common/bit_util.h"
#include "common/common_types.h"
#include "common/tiny_mt.h"
#include "core/hle/kernel/k_system_control.h"
namespace Kernel {
class KPageBitmap {
private:
class RandomBitGenerator {
private:
Common::TinyMT rng{};
u32 entropy{};
u32 bits_available{};
private:
void RefreshEntropy() {
entropy = rng.GenerateRandomU32();
bits_available = static_cast<u32>(Common::BitSize<decltype(entropy)>());
}
bool GenerateRandomBit() {
if (bits_available == 0) {
this->RefreshEntropy();
}
const bool rnd_bit = (entropy & 1) != 0;
entropy >>= 1;
--bits_available;
return rnd_bit;
}
public:
RandomBitGenerator() {
rng.Initialize(static_cast<u32>(KSystemControl::GenerateRandomU64()));
}
std::size_t SelectRandomBit(u64 bitmap) {
u64 selected = 0;
u64 cur_num_bits = Common::BitSize<decltype(bitmap)>() / 2;
u64 cur_mask = (1ULL << cur_num_bits) - 1;
while (cur_num_bits) {
const u64 low = (bitmap >> 0) & cur_mask;
const u64 high = (bitmap >> cur_num_bits) & cur_mask;
bool choose_low;
if (high == 0) {
// If only low val is set, choose low.
choose_low = true;
} else if (low == 0) {
// If only high val is set, choose high.
choose_low = false;
} else {
// If both are set, choose random.
choose_low = this->GenerateRandomBit();
}
// If we chose low, proceed with low.
if (choose_low) {
bitmap = low;
selected += 0;
} else {
bitmap = high;
selected += cur_num_bits;
}
// Proceed.
cur_num_bits /= 2;
cur_mask >>= cur_num_bits;
}
return selected;
}
};
public:
static constexpr std::size_t MaxDepth = 4;
private:
std::array<u64*, MaxDepth> bit_storages{};
RandomBitGenerator rng{};
std::size_t num_bits{};
std::size_t used_depths{};
public:
KPageBitmap() = default;
constexpr std::size_t GetNumBits() const {
return num_bits;
}
constexpr s32 GetHighestDepthIndex() const {
return static_cast<s32>(used_depths) - 1;
}
u64* Initialize(u64* storage, std::size_t size) {
// Initially, everything is un-set.
num_bits = 0;
// Calculate the needed bitmap depth.
used_depths = static_cast<std::size_t>(GetRequiredDepth(size));
ASSERT(used_depths <= MaxDepth);
// Set the bitmap pointers.
for (s32 depth = this->GetHighestDepthIndex(); depth >= 0; depth--) {
bit_storages[depth] = storage;
size = Common::AlignUp(size, Common::BitSize<u64>()) / Common::BitSize<u64>();
storage += size;
}
return storage;
}
s64 FindFreeBlock(bool random) {
uintptr_t offset = 0;
s32 depth = 0;
if (random) {
do {
const u64 v = bit_storages[depth][offset];
if (v == 0) {
// If depth is bigger than zero, then a previous level indicated a block was
// free.
ASSERT(depth == 0);
return -1;
}
offset = offset * Common::BitSize<u64>() + rng.SelectRandomBit(v);
++depth;
} while (depth < static_cast<s32>(used_depths));
} else {
do {
const u64 v = bit_storages[depth][offset];
if (v == 0) {
// If depth is bigger than zero, then a previous level indicated a block was
// free.
ASSERT(depth == 0);
return -1;
}
offset = offset * Common::BitSize<u64>() + std::countr_zero(v);
++depth;
} while (depth < static_cast<s32>(used_depths));
}
return static_cast<s64>(offset);
}
void SetBit(std::size_t offset) {
this->SetBit(this->GetHighestDepthIndex(), offset);
num_bits++;
}
void ClearBit(std::size_t offset) {
this->ClearBit(this->GetHighestDepthIndex(), offset);
num_bits--;
}
bool ClearRange(std::size_t offset, std::size_t count) {
s32 depth = this->GetHighestDepthIndex();
u64* bits = bit_storages[depth];
std::size_t bit_ind = offset / Common::BitSize<u64>();
if (count < Common::BitSize<u64>()) {
const std::size_t shift = offset % Common::BitSize<u64>();
ASSERT(shift + count <= Common::BitSize<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 {
ASSERT(offset % Common::BitSize<u64>() == 0);
ASSERT(count % Common::BitSize<u64>() == 0);
// Check that all the bits are set.
std::size_t remaining = count;
std::size_t i = 0;
do {
if (bits[bit_ind + i++] != ~u64(0)) {
return false;
}
remaining -= Common::BitSize<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 -= Common::BitSize<u64>();
} while (remaining > 0);
}
num_bits -= count;
return true;
}
private:
void SetBit(s32 depth, std::size_t offset) {
while (depth >= 0) {
std::size_t ind = offset / Common::BitSize<u64>();
std::size_t which = offset % Common::BitSize<u64>();
const u64 mask = u64(1) << which;
u64* bit = std::addressof(bit_storages[depth][ind]);
u64 v = *bit;
ASSERT((v & mask) == 0);
*bit = v | mask;
if (v) {
break;
}
offset = ind;
depth--;
}
}
void ClearBit(s32 depth, std::size_t offset) {
while (depth >= 0) {
std::size_t ind = offset / Common::BitSize<u64>();
std::size_t which = offset % Common::BitSize<u64>();
const u64 mask = u64(1) << which;
u64* bit = std::addressof(bit_storages[depth][ind]);
u64 v = *bit;
ASSERT((v & mask) != 0);
v &= ~mask;
*bit = v;
if (v) {
break;
}
offset = ind;
depth--;
}
}
private:
static constexpr s32 GetRequiredDepth(std::size_t region_size) {
s32 depth = 0;
while (true) {
region_size /= Common::BitSize<u64>();
depth++;
if (region_size == 0) {
return depth;
}
}
}
public:
static constexpr std::size_t CalculateManagementOverheadSize(std::size_t region_size) {
std::size_t overhead_bits = 0;
for (s32 depth = GetRequiredDepth(region_size) - 1; depth >= 0; depth--) {
region_size =
Common::AlignUp(region_size, Common::BitSize<u64>()) / Common::BitSize<u64>();
overhead_bits += region_size;
}
return overhead_bits * sizeof(u64);
}
};
} // namespace Kernel
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