hmac-cpp/include/hmac_cpp/page_lock_registry.hpp at main · LimiNode/hmac-cpp · GitHub

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#ifndef HMAC_CPP_PAGE_LOCK_REGISTRY_HPP

#define HMAC_CPP_PAGE_LOCK_REGISTRY_HPP

#include <cstddef>

#include <cstdint>

#include <limits>

#include <map>

#include <memory>

#include <mutex>

#include <utility>

namespace hmac_cpp {

namespace detail {

struct page_lock_page_state {

std::size_t owners{};

bool os_locked{};

bool pending_lock{};

};

/// \brief Process-wide ownership registry for page-granular memory locks.

/// \tparam PageLocker Type exposing lock_page() and unlock_page().

/// \tparam Mutex Mutex type used to synchronize access to the registry.

/// \tparam PageStateAllocator Allocator used by the registry's page-state map.

template<class PageLocker,

class Mutex = std::mutex,

class PageStateAllocator = std::allocator<std::pair<const std::uintptr_t, page_lock_page_state>>>

class page_lock_registry {

public:

static_assert(noexcept(std::declval<PageLocker&>().lock_page(nullptr, std::size_t{})),

"PageLocker::lock_page must be noexcept");

static_assert(noexcept(std::declval<PageLocker&>().unlock_page(nullptr, std::size_t{})),

"PageLocker::unlock_page must be noexcept");

explicit page_lock_registry(std::size_t page_size, PageLocker locker = PageLocker())

: page_size_(page_size), locker_(locker) {}

bool lock(void* ptr, std::size_t len) noexcept {

std::uintptr_t first = 0;

std::uintptr_t last = 0;

if (!normalize(ptr, len, first, last)) {

return false;

}

try {

std::lock_guard<Mutex> guard(mutex_);

return lock_range(first, last);

} catch (...) {

return false;

}

bool unlock(void* ptr, std::size_t len) noexcept {

std::uintptr_t first = 0;

std::uintptr_t last = 0;

if (!normalize(ptr, len, first, last)) {

return false;

}

try {

std::lock_guard<Mutex> guard(mutex_);

if (!all_pages_owned(first, last)) {

return false;

}

bool success = true;

for_each_page(first, last, [this, &success](std::uintptr_t page) {

typename page_states_type::iterator entry = page_states_.find(page);

page_state& state = entry->second;

if (state.owners > 1) {

--state.owners;

return true;

}

state.owners = 0;

if (!state.os_locked || locker_.unlock_page(reinterpret_cast<void*>(page), page_size_)) {

page_states_.erase(entry);

} else {

success = false;

}

return true;

});

return success;

} catch (...) {

return false;

}

private:

using page_state = page_lock_page_state;

using page_states_type = std::map<std::uintptr_t,

page_state,

std::less<std::uintptr_t>,

PageStateAllocator>;

bool normalize(void* ptr, std::size_t len, std::uintptr_t& first,

std::uintptr_t& last) const noexcept {

if (ptr == nullptr || len == 0 || page_size_ == 0) {

return false;

}

const std::uintptr_t address = reinterpret_cast<std::uintptr_t>(ptr);

if (len - 1 > std::numeric_limits<std::uintptr_t>::max() - address) {

return false;

}

const std::uintptr_t end = address + len - 1;

first = address - address % page_size_;

last = end - end % page_size_;

return true;

}

template<class Visitor>

void for_each_page(std::uintptr_t first, std::uintptr_t last, Visitor visitor) {

for (std::uintptr_t page = first;; page += page_size_) {

if (!visitor(page) || page == last) {

return;

}

bool all_pages_owned(std::uintptr_t first, std::uintptr_t last) const noexcept {

for (std::uintptr_t page = first;; page += page_size_) {

const typename page_states_type::const_iterator entry = page_states_.find(page);

if (entry == page_states_.end() || entry->second.owners == 0 || entry->second.pending_lock) {

return false;

}

if (page == last) {

return true;

}

bool lock_range(std::uintptr_t first, std::uintptr_t last) noexcept {

try {

for_each_page(first, last, [this](std::uintptr_t page) {

page_states_.emplace(page, page_state{});

return true;

});

} catch (...) {

erase_unlocked_pages(first, last);

return false;

}

bool overflow = false;

for_each_page(first, last, [this, &overflow](std::uintptr_t page) {

const typename page_states_type::const_iterator entry = page_states_.find(page);

if (entry->second.owners == std::numeric_limits<std::size_t>::max()) {

overflow = true;

return false;

}

return true;

});

if (overflow) {

erase_unlocked_pages(first, last);

return false;

}

for_each_page(first, last, [this](std::uintptr_t page) {

typename page_states_type::iterator entry = page_states_.find(page);

page_state& state = entry->second;

if (state.owners != 0 || state.os_locked) {

return true;

}

if (!locker_.lock_page(reinterpret_cast<void*>(page), page_size_)) {

return false;

}

state.os_locked = true;

state.pending_lock = true;

return true;

});

if (has_unlocked_page(first, last)) {

rollback_pending_locks(first, last);

return false;

}

for_each_page(first, last, [this](std::uintptr_t page) {

typename page_states_type::iterator entry = page_states_.find(page);

++entry->second.owners;

entry->second.pending_lock = false;

return true;

});

return true;

}

bool has_unlocked_page(std::uintptr_t first, std::uintptr_t last) const noexcept {

for (std::uintptr_t page = first;; page += page_size_) {

const typename page_states_type::const_iterator entry = page_states_.find(page);

if (entry == page_states_.end() || (!entry->second.os_locked && entry->second.owners == 0)) {

return true;

}

if (page == last) {

return false;

}

void erase_unlocked_pages(std::uintptr_t first, std::uintptr_t last) noexcept {

for_each_page(first, last, [this](std::uintptr_t page) {

typename page_states_type::iterator entry = page_states_.find(page);

if (entry != page_states_.end() && entry->second.owners == 0 && !entry->second.os_locked) {

page_states_.erase(entry);

}

return true;

});

}

void rollback_pending_locks(std::uintptr_t first, std::uintptr_t last) noexcept {

for_each_page(first, last, [this](std::uintptr_t page) {

typename page_states_type::iterator entry = page_states_.find(page);

if (entry == page_states_.end()) {

return true;

}

page_state& state = entry->second;

if (state.pending_lock) {

if (locker_.unlock_page(reinterpret_cast<void*>(page), page_size_)) {

page_states_.erase(entry);

} else {

state.pending_lock = false;

}

} else if (state.owners == 0 && !state.os_locked) {

page_states_.erase(entry);

}

return true;

});

}

std::size_t page_size_{};

PageLocker locker_;

page_states_type page_states_;

Mutex mutex_;

};

} // namespace detail

} // namespace hmac_cpp

#endif // HMAC_CPP_PAGE_LOCK_REGISTRY_HPP

hmac-cpp/include/hmac_cpp/page_lock_registry.hpp at main · LimiNode/hmac-cpp · GitHub

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