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-rw-r--r--src/core/hle/kernel/k_page_bitmap.h243
1 files changed, 155 insertions, 88 deletions
diff --git a/src/core/hle/kernel/k_page_bitmap.h b/src/core/hle/kernel/k_page_bitmap.h
index c97b3dc0b..0ff987732 100644
--- a/src/core/hle/kernel/k_page_bitmap.h
+++ b/src/core/hle/kernel/k_page_bitmap.h
@@ -16,107 +16,126 @@
namespace Kernel {
class KPageBitmap {
-private:
+public:
class RandomBitGenerator {
- private:
- Common::TinyMT rng{};
- u32 entropy{};
- u32 bits_available{};
+ public:
+ RandomBitGenerator() {
+ m_rng.Initialize(static_cast<u32>(KSystemControl::GenerateRandomU64()));
+ }
+
+ u64 SelectRandomBit(u64 bitmap) {
+ u64 selected = 0;
+
+ for (size_t cur_num_bits = Common::BitSize<decltype(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 + (Common::BitSize<decltype(max)>() - std::countl_zero(max));
+
+ // Generate a random value of the desired bitwidth.
+ const u64 rnd = this->GenerateRandomBits(static_cast<u32>(bits_needed));
+
+ // Adjust the value to be in range.
+ return rnd - ((rnd / max) * max);
+ }
private:
void RefreshEntropy() {
- entropy = rng.GenerateRandomU32();
- bits_available = static_cast<u32>(Common::BitSize<decltype(entropy)>());
+ m_entropy = m_rng.GenerateRandomU32();
+ m_bits_available = static_cast<u32>(Common::BitSize<decltype(m_entropy)>());
}
bool GenerateRandomBit() {
- if (bits_available == 0) {
+ if (m_bits_available == 0) {
this->RefreshEntropy();
}
- const bool rnd_bit = (entropy & 1) != 0;
- entropy >>= 1;
- --bits_available;
+ const bool rnd_bit = (m_entropy & 1) != 0;
+ m_entropy >>= 1;
+ --m_bits_available;
return rnd_bit;
}
- public:
- RandomBitGenerator() {
- rng.Initialize(static_cast<u32>(KSystemControl::GenerateRandomU64()));
- }
+ u64 GenerateRandomBits(u32 num_bits) {
+ u64 result = 0;
- std::size_t SelectRandomBit(u64 bitmap) {
- u64 selected = 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();
+ }
- u64 cur_num_bits = Common::BitSize<decltype(bitmap)>() / 2;
- u64 cur_mask = (1ULL << cur_num_bits) - 1;
+ // Determine how many bits to take this round.
+ const auto cur_bits = std::min(num_bits, m_bits_available);
- while (cur_num_bits) {
- const u64 low = (bitmap >> 0) & cur_mask;
- const u64 high = (bitmap >> cur_num_bits) & cur_mask;
+ // Generate mask for our current bits.
+ const u64 mask = (static_cast<u64>(1) << cur_bits) - 1;
- 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();
- }
+ // Add bits to output from our entropy.
+ result <<= cur_bits;
+ result |= (m_entropy & mask);
- // If we chose low, proceed with low.
- if (choose_low) {
- bitmap = low;
- selected += 0;
- } else {
- bitmap = high;
- selected += cur_num_bits;
- }
+ // Remove bits from our entropy.
+ m_entropy >>= cur_bits;
+ m_bits_available -= cur_bits;
- // Proceed.
- cur_num_bits /= 2;
- cur_mask >>= cur_num_bits;
+ // Advance.
+ num_bits -= cur_bits;
}
- return selected;
+ return result;
}
+
+ private:
+ Common::TinyMT m_rng;
+ u32 m_entropy{};
+ u32 m_bits_available{};
};
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{};
+ static constexpr size_t MaxDepth = 4;
public:
KPageBitmap() = default;
- constexpr std::size_t GetNumBits() const {
- return num_bits;
+ constexpr size_t GetNumBits() const {
+ return m_num_bits;
}
constexpr s32 GetHighestDepthIndex() const {
- return static_cast<s32>(used_depths) - 1;
+ return static_cast<s32>(m_used_depths) - 1;
}
- u64* Initialize(u64* storage, std::size_t size) {
+ u64* Initialize(u64* storage, size_t size) {
// Initially, everything is un-set.
- num_bits = 0;
+ m_num_bits = 0;
// Calculate the needed bitmap depth.
- used_depths = static_cast<std::size_t>(GetRequiredDepth(size));
- ASSERT(used_depths <= MaxDepth);
+ m_used_depths = static_cast<size_t>(GetRequiredDepth(size));
+ ASSERT(m_used_depths <= MaxDepth);
// Set the bitmap pointers.
for (s32 depth = this->GetHighestDepthIndex(); depth >= 0; depth--) {
- bit_storages[depth] = storage;
+ m_bit_storages[depth] = storage;
size = Common::AlignUp(size, Common::BitSize<u64>()) / Common::BitSize<u64>();
storage += size;
+ m_end_storages[depth] = storage;
}
return storage;
@@ -128,19 +147,19 @@ public:
if (random) {
do {
- const u64 v = bit_storages[depth][offset];
+ 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.
ASSERT(depth == 0);
return -1;
}
- offset = offset * Common::BitSize<u64>() + rng.SelectRandomBit(v);
+ offset = offset * Common::BitSize<u64>() + m_rng.SelectRandomBit(v);
++depth;
- } while (depth < static_cast<s32>(used_depths));
+ } while (depth < static_cast<s32>(m_used_depths));
} else {
do {
- const u64 v = bit_storages[depth][offset];
+ 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.
@@ -149,28 +168,69 @@ public:
}
offset = offset * Common::BitSize<u64>() + std::countr_zero(v);
++depth;
- } while (depth < static_cast<s32>(used_depths));
+ } while (depth < static_cast<s32>(m_used_depths));
}
return static_cast<s64>(offset);
}
- void SetBit(std::size_t offset) {
+ s64 FindFreeRange(size_t count) {
+ // Check that it is possible to find a range.
+ const u64* const storage_start = m_bit_storages[m_used_depths - 1];
+ const u64* const storage_end = m_end_storages[m_used_depths - 1];
+
+ // If we don't have a storage to iterate (or want more blocks than fit in a single storage),
+ // we can't find a free range.
+ if (!(storage_start < storage_end && count <= Common::BitSize<u64>())) {
+ return -1;
+ }
+
+ // Walk the storages to select a random free range.
+ const size_t options_per_storage = std::max<size_t>(Common::BitSize<u64>() / count, 1);
+ const size_t num_entries = std::max<size_t>(storage_end - storage_start, 1);
+
+ const u64 free_mask = (static_cast<u64>(1) << count) - 1;
+
+ size_t num_valid_options = 0;
+ s64 chosen_offset = -1;
+ for (size_t storage_index = 0; storage_index < num_entries; ++storage_index) {
+ u64 storage = storage_start[storage_index];
+ for (size_t option = 0; option < options_per_storage; ++option) {
+ if ((storage & free_mask) == free_mask) {
+ // We've found a new valid option.
+ ++num_valid_options;
+
+ // Select the Kth valid option with probability 1/K. This leads to an overall
+ // uniform distribution.
+ if (num_valid_options == 1 || m_rng.GenerateRandom(num_valid_options) == 0) {
+ // This is our first option, so select it.
+ chosen_offset = storage_index * Common::BitSize<u64>() + option * count;
+ }
+ }
+ storage >>= count;
+ }
+ }
+
+ // Return the random offset we chose.*/
+ return chosen_offset;
+ }
+
+ void SetBit(size_t offset) {
this->SetBit(this->GetHighestDepthIndex(), offset);
- num_bits++;
+ m_num_bits++;
}
- void ClearBit(std::size_t offset) {
+ void ClearBit(size_t offset) {
this->ClearBit(this->GetHighestDepthIndex(), offset);
- num_bits--;
+ m_num_bits--;
}
- bool ClearRange(std::size_t offset, std::size_t count) {
+ bool ClearRange(size_t offset, 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>();
+ u64* bits = m_bit_storages[depth];
+ size_t bit_ind = offset / Common::BitSize<u64>();
+ if (count < Common::BitSize<u64>()) [[likely]] {
+ const 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;
@@ -189,8 +249,8 @@ public:
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;
+ size_t remaining = count;
+ size_t i = 0;
do {
if (bits[bit_ind + i++] != ~u64(0)) {
return false;
@@ -209,18 +269,18 @@ public:
} while (remaining > 0);
}
- num_bits -= count;
+ m_num_bits -= count;
return true;
}
private:
- void SetBit(s32 depth, std::size_t offset) {
+ void SetBit(s32 depth, size_t offset) {
while (depth >= 0) {
- std::size_t ind = offset / Common::BitSize<u64>();
- std::size_t which = offset % Common::BitSize<u64>();
+ size_t ind = offset / Common::BitSize<u64>();
+ size_t which = offset % Common::BitSize<u64>();
const u64 mask = u64(1) << which;
- u64* bit = std::addressof(bit_storages[depth][ind]);
+ u64* bit = std::addressof(m_bit_storages[depth][ind]);
u64 v = *bit;
ASSERT((v & mask) == 0);
*bit = v | mask;
@@ -232,13 +292,13 @@ private:
}
}
- void ClearBit(s32 depth, std::size_t offset) {
+ void ClearBit(s32 depth, size_t offset) {
while (depth >= 0) {
- std::size_t ind = offset / Common::BitSize<u64>();
- std::size_t which = offset % Common::BitSize<u64>();
+ size_t ind = offset / Common::BitSize<u64>();
+ size_t which = offset % Common::BitSize<u64>();
const u64 mask = u64(1) << which;
- u64* bit = std::addressof(bit_storages[depth][ind]);
+ u64* bit = std::addressof(m_bit_storages[depth][ind]);
u64 v = *bit;
ASSERT((v & mask) != 0);
v &= ~mask;
@@ -252,7 +312,7 @@ private:
}
private:
- static constexpr s32 GetRequiredDepth(std::size_t region_size) {
+ static constexpr s32 GetRequiredDepth(size_t region_size) {
s32 depth = 0;
while (true) {
region_size /= Common::BitSize<u64>();
@@ -264,8 +324,8 @@ private:
}
public:
- static constexpr std::size_t CalculateManagementOverheadSize(std::size_t region_size) {
- std::size_t overhead_bits = 0;
+ 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 =
Common::AlignUp(region_size, Common::BitSize<u64>()) / Common::BitSize<u64>();
@@ -273,6 +333,13 @@ public:
}
return overhead_bits * sizeof(u64);
}
+
+private:
+ std::array<u64*, MaxDepth> m_bit_storages{};
+ std::array<u64*, MaxDepth> m_end_storages{};
+ RandomBitGenerator m_rng;
+ size_t m_num_bits{};
+ size_t m_used_depths{};
};
} // namespace Kernel