3 files changed, 384 insertions, 0 deletions
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 2d403d471..97fbdcbf9 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -131,6 +131,8 @@ add_library(common STATIC
     hash.h
     hex_util.cpp
     hex_util.h
+    host_memory.cpp
+    host_memory.h
     intrusive_red_black_tree.h
     logging/backend.cpp
     logging/backend.h
diff --git a/src/common/host_memory.cpp b/src/common/host_memory.cpp
new file mode 100644
index 000000000..4f5086e90
--- /dev/null
+++ b/src/common/host_memory.cpp
@@ -0,0 +1,320 @@
+#ifdef __linux__
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#elif defined(_WIN32) // ^^^ Linux ^^^ vvv Windows vvv
+#ifdef _WIN32_WINNT
+#undef _WIN32_WINNT
+#endif
+#define _WIN32_WINNT 0x0A00 // Windows 10
+
+#include <windows.h>
+
+#include <boost/icl/separate_interval_set.hpp>
+
+#include <iterator>
+#include <unordered_map>
+
+#pragma comment(lib, "mincore.lib")
+
+#endif // ^^^ Windows ^^^
+
+#include <mutex>
+
+#include "common/assert.h"
+#include "common/host_memory.h"
+#include "common/logging/log.h"
+
+namespace Common {
+
+constexpr size_t PageAlignment = 0x1000;
+
+#ifdef _WIN32
+
+class HostMemory::Impl {
+public:
+    explicit Impl(size_t backing_size_, size_t virtual_size_)
+        : backing_size{backing_size_}, virtual_size{virtual_size_}, process{GetCurrentProcess()} {
+        // Allocate backing file map
+        backing_handle =
+            CreateFileMapping2(INVALID_HANDLE_VALUE, nullptr, FILE_MAP_WRITE | FILE_MAP_READ,
+                               PAGE_READWRITE, SEC_COMMIT, backing_size, nullptr, nullptr, 0);
+        if (!backing_handle) {
+            throw std::bad_alloc{};
+        }
+        // Allocate a virtual memory for the backing file map as placeholder
+        backing_base = static_cast<u8*>(VirtualAlloc2(process, nullptr, backing_size,
+                                                      MEM_RESERVE | MEM_RESERVE_PLACEHOLDER,
+                                                      PAGE_NOACCESS, nullptr, 0));
+        if (!backing_base) {
+            Release();
+            throw std::bad_alloc{};
+        }
+        // Map backing placeholder
+        void* const ret = MapViewOfFile3(backing_handle, process, backing_base, 0, backing_size,
+                                         MEM_REPLACE_PLACEHOLDER, PAGE_READWRITE, nullptr, 0);
+        if (ret != backing_base) {
+            Release();
+            throw std::bad_alloc{};
+        }
+        // Allocate virtual address placeholder
+        virtual_base = static_cast<u8*>(VirtualAlloc2(process, nullptr, virtual_size,
+                                                      MEM_RESERVE | MEM_RESERVE_PLACEHOLDER,
+                                                      PAGE_NOACCESS, nullptr, 0));
+        if (!virtual_base) {
+            Release();
+            throw std::bad_alloc{};
+        }
+    }
+
+    ~Impl() {
+        Release();
+    }
+
+    void Map(size_t virtual_offset, size_t host_offset, size_t length) {
+        std::unique_lock lock{placeholder_mutex};
+        if (!IsNiechePlaceholder(virtual_offset, length)) {
+            Split(virtual_offset, length);
+        }
+        ASSERT(placeholders.find({virtual_offset, virtual_offset + length}) == placeholders.end());
+        TrackPlaceholder(virtual_offset, host_offset, length);
+
+        MapView(virtual_offset, host_offset, length);
+    }
+
+    void Unmap(size_t virtual_offset, size_t length) {
+        std::lock_guard lock{placeholder_mutex};
+
+        // Unmap until there are no more placeholders
+        while (UnmapOnePlaceholder(virtual_offset, length)) {
+        }
+    }
+
+    void Protect(size_t virtual_offset, size_t length, bool read, bool write) {
+        DWORD new_flags{};
+        if (read && write) {
+            new_flags = PAGE_READWRITE;
+        } else if (read && !write) {
+            new_flags = PAGE_READONLY;
+        } else if (!read && !write) {
+            new_flags = PAGE_NOACCESS;
+        } else {
+            UNIMPLEMENTED_MSG("Protection flag combination read={} write={}", read, write);
+        }
+        DWORD old_flags{};
+        if (!VirtualProtect(virtual_base + virtual_offset, length, new_flags, &old_flags)) {
+            LOG_CRITICAL(HW_Memory, "Failed to change virtual memory protect rules");
+        }
+    }
+
+    const size_t backing_size; ///< Size of the backing memory in bytes
+    const size_t virtual_size; ///< Size of the virtual address placeholder in bytes
+
+    u8* backing_base{};
+    u8* virtual_base{};
+
+private:
+    /// Release all resources in the object
+    void Release() {
+        if (!placeholders.empty()) {
+            for (const auto& placeholder : placeholders) {
+                if (!UnmapViewOfFile2(process, virtual_base + placeholder.lower(),
+                                      MEM_PRESERVE_PLACEHOLDER)) {
+                    LOG_CRITICAL(HW_Memory, "Failed to unmap virtual memory placeholder");
+                }
+            }
+            Coalesce(0, virtual_size);
+        }
+        if (virtual_base) {
+            if (!VirtualFree(virtual_base, 0, MEM_RELEASE)) {
+                LOG_CRITICAL(HW_Memory, "Failed to free virtual memory");
+            }
+        }
+        if (backing_base) {
+            if (!UnmapViewOfFile2(process, backing_base, MEM_PRESERVE_PLACEHOLDER)) {
+                LOG_CRITICAL(HW_Memory, "Failed to unmap backing memory placeholder");
+            }
+            if (!VirtualFreeEx(process, backing_base, 0, MEM_RELEASE)) {
+                LOG_CRITICAL(HW_Memory, "Failed to free backing memory");
+            }
+        }
+        if (!CloseHandle(backing_handle)) {
+            LOG_CRITICAL(HW_Memory, "Failed to free backing memory file handle");
+        }
+    }
+
+    /// Unmap one placeholder in the given range (partial unmaps are supported)
+    /// Return true when there are no more placeholders to unmap
+    bool UnmapOnePlaceholder(size_t virtual_offset, size_t length) {
+        const auto it = placeholders.find({virtual_offset, virtual_offset + length});
+        const auto begin = placeholders.begin();
+        const auto end = placeholders.end();
+        if (it == end) {
+            return false;
+        }
+        const size_t placeholder_begin = it->lower();
+        const size_t placeholder_end = it->upper();
+        const size_t unmap_begin = std::max(virtual_offset, placeholder_begin);
+        const size_t unmap_end = std::min(virtual_offset + length, placeholder_end);
+        ASSERT(unmap_begin >= placeholder_begin && unmap_begin < placeholder_end);
+        ASSERT(unmap_end <= placeholder_end && unmap_end > placeholder_begin);
+
+        const auto host_pointer_it = placeholder_host_pointers.find(placeholder_begin);
+        ASSERT(host_pointer_it != placeholder_host_pointers.end());
+        const size_t host_offset = host_pointer_it->second;
+
+        const bool split_left = unmap_begin > placeholder_begin;
+        const bool split_right = unmap_end < placeholder_end;
+
+        if (!UnmapViewOfFile2(process, virtual_base + placeholder_begin,
+                              MEM_PRESERVE_PLACEHOLDER)) {
+            LOG_CRITICAL(HW_Memory, "Failed to unmap placeholder");
+        }
+        // If we have to remap memory regions due to partial unmaps, we are in a data race as
+        // Windows doesn't support remapping memory without unmapping first. Avoid adding any extra
+        // logic within the panic region described below.
+
+        // Panic region, we are in a data race right now
+        if (split_left || split_right) {
+            Split(unmap_begin, unmap_end - unmap_begin);
+        }
+        if (split_left) {
+            MapView(placeholder_begin, host_offset, unmap_begin - placeholder_begin);
+        }
+        if (split_right) {
+            MapView(unmap_end, host_offset + unmap_end - placeholder_begin,
+                    placeholder_end - unmap_end);
+        }
+        // End panic region
+
+        size_t coalesce_begin = unmap_begin;
+        if (!split_left) {
+            // Try to coalesce pages to the left
+            coalesce_begin = it == begin ? 0 : std::prev(it)->upper();
+            if (coalesce_begin != placeholder_begin) {
+                Coalesce(coalesce_begin, unmap_end - coalesce_begin);
+            }
+        }
+        if (!split_right) {
+            // Try to coalesce pages to the right
+            const auto next = std::next(it);
+            const size_t next_begin = next == end ? virtual_size : next->lower();
+            if (placeholder_end != next_begin) {
+                // We can coalesce to the right
+                Coalesce(coalesce_begin, next_begin - coalesce_begin);
+            }
+        }
+        // Remove and reinsert placeholder trackers
+        UntrackPlaceholder(it);
+        if (split_left) {
+            TrackPlaceholder(placeholder_begin, host_offset, unmap_begin - placeholder_begin);
+        }
+        if (split_right) {
+            TrackPlaceholder(unmap_end, host_offset + unmap_end - placeholder_begin,
+                             placeholder_end - unmap_end);
+        }
+        return true;
+    }
+
+    void MapView(size_t virtual_offset, size_t host_offset, size_t length) {
+        if (!MapViewOfFile3(backing_handle, process, virtual_base + virtual_offset, host_offset,
+                            length, MEM_REPLACE_PLACEHOLDER, PAGE_READWRITE, nullptr, 0)) {
+            LOG_CRITICAL(HW_Memory, "Failed to map placeholder");
+        }
+    }
+
+    void Split(size_t virtual_offset, size_t length) {
+        if (!VirtualFreeEx(process, reinterpret_cast<LPVOID>(virtual_base + virtual_offset), length,
+                           MEM_RELEASE | MEM_PRESERVE_PLACEHOLDER)) {
+            LOG_CRITICAL(HW_Memory, "Failed to split placeholder");
+        }
+    }
+
+    void Coalesce(size_t virtual_offset, size_t length) {
+        if (!VirtualFreeEx(process, reinterpret_cast<LPVOID>(virtual_base + virtual_offset), length,
+                           MEM_RELEASE | MEM_COALESCE_PLACEHOLDERS)) {
+            LOG_CRITICAL(HW_Memory, "Failed to coalesce placeholders");
+        }
+    }
+
+    void TrackPlaceholder(size_t virtual_offset, size_t host_offset, size_t length) {
+        placeholders.insert({virtual_offset, virtual_offset + length});
+        placeholder_host_pointers.emplace(virtual_offset, host_offset);
+    }
+
+    void UntrackPlaceholder(boost::icl::separate_interval_set<size_t>::iterator it) {
+        placeholders.erase(it);
+        placeholder_host_pointers.erase(it->lower());
+    }
+
+    /// Return true when a given memory region is a "nieche" and the placeholders don't have to be
+    /// splitted.
+    bool IsNiechePlaceholder(size_t virtual_offset, size_t length) const {
+        const auto it = placeholders.upper_bound({virtual_offset, virtual_offset + length});
+        if (it != placeholders.end() && it->lower() == virtual_offset + length) {
+            const bool is_root = it == placeholders.begin() && virtual_offset == 0;
+            return is_root || std::prev(it)->upper() == virtual_offset;
+        }
+        return false;
+    }
+
+    HANDLE process{};        ///< Current process handle
+    HANDLE backing_handle{}; ///< File based backing memory
+
+    std::mutex placeholder_mutex;                                 ///< Mutex for placeholders
+    boost::icl::separate_interval_set<size_t> placeholders;       ///< Mapped placeholders
+    std::unordered_map<size_t, size_t> placeholder_host_pointers; ///< Placeholder backing offset
+};
+
+#else
+
+#error Please implement the host memory for your platform
+
+#endif
+
+HostMemory::HostMemory(size_t backing_size, size_t virtual_size)
+    : impl{std::make_unique<HostMemory::Impl>(backing_size, virtual_size)},
+      backing_base{impl->backing_base}, virtual_base{impl->virtual_base} {}
+
+HostMemory::~HostMemory() = default;
+
+HostMemory::HostMemory(HostMemory&&) noexcept = default;
+
+HostMemory& HostMemory::operator=(HostMemory&&) noexcept = default;
+
+void HostMemory::Map(size_t virtual_offset, size_t host_offset, size_t length) {
+    ASSERT(virtual_offset % PageAlignment == 0);
+    ASSERT(host_offset % PageAlignment == 0);
+    ASSERT(length % PageAlignment == 0);
+    ASSERT(virtual_offset + length <= impl->virtual_size);
+    ASSERT(host_offset + length <= impl->backing_size);
+    if (length == 0) {
+        return;
+    }
+    impl->Map(virtual_offset, host_offset, length);
+}
+
+void HostMemory::Unmap(size_t virtual_offset, size_t length) {
+    ASSERT(virtual_offset % PageAlignment == 0);
+    ASSERT(length % PageAlignment == 0);
+    ASSERT(virtual_offset + length <= impl->virtual_size);
+    if (length == 0) {
+        return;
+    }
+    impl->Unmap(virtual_offset, length);
+}
+
+void HostMemory::Protect(size_t virtual_offset, size_t length, bool read, bool write) {
+    ASSERT(virtual_offset % PageAlignment == 0);
+    ASSERT(length % PageAlignment == 0);
+    ASSERT(virtual_offset + length <= impl->virtual_size);
+    if (length == 0) {
+        return;
+    }
+    impl->Protect(virtual_offset, length, read, write);
+}
+
+} // namespace Common
diff --git a/src/common/host_memory.h b/src/common/host_memory.h
new file mode 100644
index 000000000..98005df7a
--- /dev/null
+++ b/src/common/host_memory.h
@@ -0,0 +1,62 @@
+// Copyright 2019 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include "common/common_types.h"
+
+namespace Common {
+
+/**
+ * A low level linear memory buffer, which supports multiple mappings
+ * Its purpose is to rebuild a given sparse memory layout, including mirrors.
+ */
+class HostMemory {
+public:
+    explicit HostMemory(size_t backing_size, size_t virtual_size);
+    ~HostMemory();
+
+    /**
+     * Copy constructors. They shall return a copy of the buffer without the mappings.
+     * TODO: Implement them with COW if needed.
+     */
+    HostMemory(const HostMemory& other) = delete;
+    HostMemory& operator=(const HostMemory& other) = delete;
+
+    /**
+     * Move constructors. They will move the buffer and the mappings to the new object.
+     */
+    HostMemory(HostMemory&& other) noexcept;
+    HostMemory& operator=(HostMemory&& other) noexcept;
+
+    void Map(size_t virtual_offset, size_t host_offset, size_t length);
+
+    void Unmap(size_t virtual_offset, size_t length);
+
+    void Protect(size_t virtual_offset, size_t length, bool read, bool write);
+
+    [[nodiscard]] u8* BackingBasePointer() noexcept {
+        return backing_base;
+    }
+    [[nodiscard]] const u8* BackingBasePointer() const noexcept {
+        return backing_base;
+    }
+
+    [[nodiscard]] u8* VirtualBasePointer() noexcept {
+        return virtual_base;
+    }
+    [[nodiscard]] const u8* VirtualBasePointer() const noexcept {
+        return virtual_base;
+    }
+
+private:
+    // Low level handler for the platform dependent memory routines
+    class Impl;
+    std::unique_ptr<Impl> impl;
+    u8* backing_base{};
+    u8* virtual_base{};
+};
+
+} // namespace Common