core: hle: kernel: k_page_bitmap: Refresh.
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bunnei
parent
50bfacca88
commit
6b6c02f541
@ -16,107 +16,126 @@
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namespace Kernel {
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class KPageBitmap {
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private:
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public:
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class RandomBitGenerator {
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private:
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Common::TinyMT rng{};
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u32 entropy{};
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u32 bits_available{};
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private:
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void RefreshEntropy() {
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entropy = rng.GenerateRandomU32();
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bits_available = static_cast<u32>(Common::BitSize<decltype(entropy)>());
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}
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bool GenerateRandomBit() {
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if (bits_available == 0) {
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this->RefreshEntropy();
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}
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const bool rnd_bit = (entropy & 1) != 0;
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entropy >>= 1;
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--bits_available;
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return rnd_bit;
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}
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public:
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RandomBitGenerator() {
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rng.Initialize(static_cast<u32>(KSystemControl::GenerateRandomU64()));
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m_rng.Initialize(static_cast<u32>(KSystemControl::GenerateRandomU64()));
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}
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std::size_t SelectRandomBit(u64 bitmap) {
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u64 SelectRandomBit(u64 bitmap) {
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u64 selected = 0;
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u64 cur_num_bits = Common::BitSize<decltype(bitmap)>() / 2;
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u64 cur_mask = (1ULL << cur_num_bits) - 1;
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for (size_t cur_num_bits = Common::BitSize<decltype(bitmap)>() / 2; cur_num_bits != 0;
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cur_num_bits /= 2) {
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const u64 high = (bitmap >> cur_num_bits);
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const u64 low = (bitmap & (~(UINT64_C(0xFFFFFFFFFFFFFFFF) << cur_num_bits)));
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while (cur_num_bits) {
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const u64 low = (bitmap >> 0) & cur_mask;
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const u64 high = (bitmap >> cur_num_bits) & cur_mask;
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bool choose_low;
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if (high == 0) {
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// If only low val is set, choose low.
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choose_low = true;
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} else if (low == 0) {
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// If only high val is set, choose high.
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choose_low = false;
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} else {
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// If both are set, choose random.
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choose_low = this->GenerateRandomBit();
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}
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// If we chose low, proceed with low.
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if (choose_low) {
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bitmap = low;
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selected += 0;
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} else {
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// Choose high if we have high and (don't have low or select high randomly).
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if (high && (low == 0 || this->GenerateRandomBit())) {
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bitmap = high;
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selected += cur_num_bits;
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} else {
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bitmap = low;
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selected += 0;
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}
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// Proceed.
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cur_num_bits /= 2;
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cur_mask >>= cur_num_bits;
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}
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return selected;
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}
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u64 GenerateRandom(u64 max) {
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// Determine the number of bits we need.
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const u64 bits_needed = 1 + (Common::BitSize<decltype(max)>() - std::countl_zero(max));
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// Generate a random value of the desired bitwidth.
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const u64 rnd = this->GenerateRandomBits(static_cast<u32>(bits_needed));
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// Adjust the value to be in range.
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return rnd - ((rnd / max) * max);
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}
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private:
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void RefreshEntropy() {
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m_entropy = m_rng.GenerateRandomU32();
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m_bits_available = static_cast<u32>(Common::BitSize<decltype(m_entropy)>());
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}
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bool GenerateRandomBit() {
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if (m_bits_available == 0) {
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this->RefreshEntropy();
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}
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const bool rnd_bit = (m_entropy & 1) != 0;
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m_entropy >>= 1;
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--m_bits_available;
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return rnd_bit;
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}
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u64 GenerateRandomBits(u32 num_bits) {
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u64 result = 0;
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// Iteratively add random bits to our result.
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while (num_bits > 0) {
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// Ensure we have random bits to take from.
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if (m_bits_available == 0) {
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this->RefreshEntropy();
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}
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// Determine how many bits to take this round.
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const auto cur_bits = std::min(num_bits, m_bits_available);
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// Generate mask for our current bits.
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const u64 mask = (static_cast<u64>(1) << cur_bits) - 1;
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// Add bits to output from our entropy.
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result <<= cur_bits;
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result |= (m_entropy & mask);
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// Remove bits from our entropy.
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m_entropy >>= cur_bits;
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m_bits_available -= cur_bits;
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// Advance.
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num_bits -= cur_bits;
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}
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return result;
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}
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private:
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Common::TinyMT m_rng;
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u32 m_entropy{};
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u32 m_bits_available{};
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};
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public:
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static constexpr std::size_t MaxDepth = 4;
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private:
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std::array<u64*, MaxDepth> bit_storages{};
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RandomBitGenerator rng{};
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std::size_t num_bits{};
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std::size_t used_depths{};
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static constexpr size_t MaxDepth = 4;
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public:
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KPageBitmap() = default;
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constexpr std::size_t GetNumBits() const {
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return num_bits;
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constexpr size_t GetNumBits() const {
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return m_num_bits;
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}
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constexpr s32 GetHighestDepthIndex() const {
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return static_cast<s32>(used_depths) - 1;
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return static_cast<s32>(m_used_depths) - 1;
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}
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u64* Initialize(u64* storage, std::size_t size) {
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u64* Initialize(u64* storage, size_t size) {
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// Initially, everything is un-set.
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num_bits = 0;
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m_num_bits = 0;
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// Calculate the needed bitmap depth.
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used_depths = static_cast<std::size_t>(GetRequiredDepth(size));
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ASSERT(used_depths <= MaxDepth);
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m_used_depths = static_cast<size_t>(GetRequiredDepth(size));
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ASSERT(m_used_depths <= MaxDepth);
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// Set the bitmap pointers.
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for (s32 depth = this->GetHighestDepthIndex(); depth >= 0; depth--) {
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bit_storages[depth] = storage;
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m_bit_storages[depth] = storage;
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size = Common::AlignUp(size, Common::BitSize<u64>()) / Common::BitSize<u64>();
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storage += size;
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m_end_storages[depth] = storage;
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}
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return storage;
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@ -128,19 +147,19 @@ public:
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if (random) {
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do {
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const u64 v = bit_storages[depth][offset];
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const u64 v = m_bit_storages[depth][offset];
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if (v == 0) {
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// If depth is bigger than zero, then a previous level indicated a block was
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// free.
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ASSERT(depth == 0);
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return -1;
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}
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offset = offset * Common::BitSize<u64>() + rng.SelectRandomBit(v);
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offset = offset * Common::BitSize<u64>() + m_rng.SelectRandomBit(v);
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++depth;
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} while (depth < static_cast<s32>(used_depths));
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} while (depth < static_cast<s32>(m_used_depths));
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} else {
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do {
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const u64 v = bit_storages[depth][offset];
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const u64 v = m_bit_storages[depth][offset];
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if (v == 0) {
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// If depth is bigger than zero, then a previous level indicated a block was
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// free.
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@ -149,28 +168,69 @@ public:
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}
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offset = offset * Common::BitSize<u64>() + std::countr_zero(v);
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++depth;
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} while (depth < static_cast<s32>(used_depths));
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} while (depth < static_cast<s32>(m_used_depths));
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}
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return static_cast<s64>(offset);
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}
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void SetBit(std::size_t offset) {
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s64 FindFreeRange(size_t count) {
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// Check that it is possible to find a range.
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const u64* const storage_start = m_bit_storages[m_used_depths - 1];
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const u64* const storage_end = m_end_storages[m_used_depths - 1];
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// If we don't have a storage to iterate (or want more blocks than fit in a single storage),
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// we can't find a free range.
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if (!(storage_start < storage_end && count <= Common::BitSize<u64>())) {
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return -1;
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}
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// Walk the storages to select a random free range.
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const size_t options_per_storage = std::max<size_t>(Common::BitSize<u64>() / count, 1);
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const size_t num_entries = std::max<size_t>(storage_end - storage_start, 1);
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const u64 free_mask = (static_cast<u64>(1) << count) - 1;
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size_t num_valid_options = 0;
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s64 chosen_offset = -1;
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for (size_t storage_index = 0; storage_index < num_entries; ++storage_index) {
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u64 storage = storage_start[storage_index];
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for (size_t option = 0; option < options_per_storage; ++option) {
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if ((storage & free_mask) == free_mask) {
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// We've found a new valid option.
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++num_valid_options;
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// Select the Kth valid option with probability 1/K. This leads to an overall
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// uniform distribution.
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if (num_valid_options == 1 || m_rng.GenerateRandom(num_valid_options) == 0) {
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// This is our first option, so select it.
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chosen_offset = storage_index * Common::BitSize<u64>() + option * count;
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}
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}
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storage >>= count;
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}
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}
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// Return the random offset we chose.*/
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return chosen_offset;
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}
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void SetBit(size_t offset) {
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this->SetBit(this->GetHighestDepthIndex(), offset);
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num_bits++;
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m_num_bits++;
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}
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void ClearBit(std::size_t offset) {
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void ClearBit(size_t offset) {
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this->ClearBit(this->GetHighestDepthIndex(), offset);
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num_bits--;
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m_num_bits--;
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}
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bool ClearRange(std::size_t offset, std::size_t count) {
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bool ClearRange(size_t offset, size_t count) {
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s32 depth = this->GetHighestDepthIndex();
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u64* bits = bit_storages[depth];
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std::size_t bit_ind = offset / Common::BitSize<u64>();
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if (count < Common::BitSize<u64>()) {
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const std::size_t shift = offset % Common::BitSize<u64>();
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u64* bits = m_bit_storages[depth];
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size_t bit_ind = offset / Common::BitSize<u64>();
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if (count < Common::BitSize<u64>()) [[likely]] {
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const size_t shift = offset % Common::BitSize<u64>();
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ASSERT(shift + count <= Common::BitSize<u64>());
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// Check that all the bits are set.
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const u64 mask = ((u64(1) << count) - 1) << shift;
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@ -189,8 +249,8 @@ public:
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ASSERT(offset % Common::BitSize<u64>() == 0);
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ASSERT(count % Common::BitSize<u64>() == 0);
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// Check that all the bits are set.
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std::size_t remaining = count;
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std::size_t i = 0;
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size_t remaining = count;
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size_t i = 0;
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do {
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if (bits[bit_ind + i++] != ~u64(0)) {
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return false;
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@ -209,18 +269,18 @@ public:
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} while (remaining > 0);
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}
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num_bits -= count;
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m_num_bits -= count;
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return true;
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}
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private:
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void SetBit(s32 depth, std::size_t offset) {
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void SetBit(s32 depth, size_t offset) {
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while (depth >= 0) {
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std::size_t ind = offset / Common::BitSize<u64>();
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std::size_t which = offset % Common::BitSize<u64>();
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size_t ind = offset / Common::BitSize<u64>();
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size_t which = offset % Common::BitSize<u64>();
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const u64 mask = u64(1) << which;
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u64* bit = std::addressof(bit_storages[depth][ind]);
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u64* bit = std::addressof(m_bit_storages[depth][ind]);
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u64 v = *bit;
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ASSERT((v & mask) == 0);
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*bit = v | mask;
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@ -232,13 +292,13 @@ private:
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}
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}
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void ClearBit(s32 depth, std::size_t offset) {
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void ClearBit(s32 depth, size_t offset) {
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while (depth >= 0) {
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std::size_t ind = offset / Common::BitSize<u64>();
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std::size_t which = offset % Common::BitSize<u64>();
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size_t ind = offset / Common::BitSize<u64>();
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size_t which = offset % Common::BitSize<u64>();
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const u64 mask = u64(1) << which;
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u64* bit = std::addressof(bit_storages[depth][ind]);
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u64* bit = std::addressof(m_bit_storages[depth][ind]);
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u64 v = *bit;
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ASSERT((v & mask) != 0);
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v &= ~mask;
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@ -252,7 +312,7 @@ private:
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}
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private:
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static constexpr s32 GetRequiredDepth(std::size_t region_size) {
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static constexpr s32 GetRequiredDepth(size_t region_size) {
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s32 depth = 0;
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while (true) {
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region_size /= Common::BitSize<u64>();
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@ -264,8 +324,8 @@ private:
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}
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public:
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static constexpr std::size_t CalculateManagementOverheadSize(std::size_t region_size) {
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std::size_t overhead_bits = 0;
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static constexpr size_t CalculateManagementOverheadSize(size_t region_size) {
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size_t overhead_bits = 0;
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for (s32 depth = GetRequiredDepth(region_size) - 1; depth >= 0; depth--) {
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region_size =
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Common::AlignUp(region_size, Common::BitSize<u64>()) / Common::BitSize<u64>();
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@ -273,6 +333,13 @@ public:
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}
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return overhead_bits * sizeof(u64);
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}
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private:
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std::array<u64*, MaxDepth> m_bit_storages{};
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std::array<u64*, MaxDepth> m_end_storages{};
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RandomBitGenerator m_rng;
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size_t m_num_bits{};
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size_t m_used_depths{};
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};
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} // namespace Kernel
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