5 files changed, 171 insertions, 0 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index c538c6415..43ae8a9e7 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -92,10 +92,14 @@ add_library(common STATIC
     logging/text_formatter.cpp
     logging/text_formatter.h
     math_util.h
+    memory_hook.cpp
+    memory_hook.h
     microprofile.cpp
     microprofile.h
     microprofileui.h
     misc.cpp
+    page_table.cpp
+    page_table.h
     param_package.cpp
     param_package.h
     quaternion.h
diff --git a/src/common/memory_hook.cpp b/src/common/memory_hook.cpp
new file mode 100644
index 000000000..3986986d6
--- /dev/null
+++ b/src/common/memory_hook.cpp
@@ -0,0 +1,11 @@
+// Copyright 2018 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/memory_hook.h"
+
+namespace Common {
+
+MemoryHook::~MemoryHook() = default;
+
+} // namespace Common
diff --git a/src/common/memory_hook.h b/src/common/memory_hook.h
new file mode 100644
index 000000000..adaa4c2c5
--- /dev/null
+++ b/src/common/memory_hook.h
@@ -0,0 +1,47 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <optional>
+
+#include "common/common_types.h"
+
+namespace Common {
+
+/**
+ * Memory hooks have two purposes:
+ * 1. To allow reads and writes to a region of memory to be intercepted. This is used to implement
+ *    texture forwarding and memory breakpoints for debugging.
+ * 2. To allow for the implementation of MMIO devices.
+ *
+ * A hook may be mapped to multiple regions of memory.
+ *
+ * If a std::nullopt or false is returned from a function, the read/write request is passed through
+ * to the underlying memory region.
+ */
+class MemoryHook {
+public:
+    virtual ~MemoryHook();
+
+    virtual std::optional<bool> IsValidAddress(VAddr addr) = 0;
+
+    virtual std::optional<u8> Read8(VAddr addr) = 0;
+    virtual std::optional<u16> Read16(VAddr addr) = 0;
+    virtual std::optional<u32> Read32(VAddr addr) = 0;
+    virtual std::optional<u64> Read64(VAddr addr) = 0;
+
+    virtual bool ReadBlock(VAddr src_addr, void* dest_buffer, std::size_t size) = 0;
+
+    virtual bool Write8(VAddr addr, u8 data) = 0;
+    virtual bool Write16(VAddr addr, u16 data) = 0;
+    virtual bool Write32(VAddr addr, u32 data) = 0;
+    virtual bool Write64(VAddr addr, u64 data) = 0;
+
+    virtual bool WriteBlock(VAddr dest_addr, const void* src_buffer, std::size_t size) = 0;
+};
+
+using MemoryHookPointer = std::shared_ptr<MemoryHook>;
+} // namespace Common
diff --git a/src/common/page_table.cpp b/src/common/page_table.cpp
new file mode 100644
index 000000000..8eba1c3f1
--- /dev/null
+++ b/src/common/page_table.cpp
@@ -0,0 +1,29 @@
+// Copyright 2019 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/page_table.h"
+
+namespace Common {
+
+PageTable::PageTable(std::size_t page_size_in_bits) : page_size_in_bits{page_size_in_bits} {}
+
+PageTable::~PageTable() = default;
+
+void PageTable::Resize(std::size_t address_space_width_in_bits) {
+    const std::size_t num_page_table_entries = 1ULL
+                                               << (address_space_width_in_bits - page_size_in_bits);
+
+    pointers.resize(num_page_table_entries);
+    attributes.resize(num_page_table_entries);
+
+    // The default is a 39-bit address space, which causes an initial 1GB allocation size. If the
+    // vector size is subsequently decreased (via resize), the vector might not automatically
+    // actually reallocate/resize its underlying allocation, which wastes up to ~800 MB for
+    // 36-bit titles. Call shrink_to_fit to reduce capacity to what's actually in use.
+
+    pointers.shrink_to_fit();
+    attributes.shrink_to_fit();
+}
+
+} // namespace Common
diff --git a/src/common/page_table.h b/src/common/page_table.h
new file mode 100644
index 000000000..8339f2890
--- /dev/null
+++ b/src/common/page_table.h
@@ -0,0 +1,80 @@
+// Copyright 2019 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <vector>
+#include <boost/icl/interval_map.hpp>
+#include "common/common_types.h"
+#include "common/memory_hook.h"
+
+namespace Common {
+
+enum class PageType : u8 {
+    /// Page is unmapped and should cause an access error.
+    Unmapped,
+    /// Page is mapped to regular memory. This is the only type you can get pointers to.
+    Memory,
+    /// Page is mapped to regular memory, but also needs to check for rasterizer cache flushing and
+    /// invalidation
+    RasterizerCachedMemory,
+    /// Page is mapped to a I/O region. Writing and reading to this page is handled by functions.
+    Special,
+};
+
+struct SpecialRegion {
+    enum class Type {
+        DebugHook,
+        IODevice,
+    } type;
+
+    MemoryHookPointer handler;
+
+    bool operator<(const SpecialRegion& other) const {
+        return std::tie(type, handler) < std::tie(other.type, other.handler);
+    }
+
+    bool operator==(const SpecialRegion& other) const {
+        return std::tie(type, handler) == std::tie(other.type, other.handler);
+    }
+};
+
+/**
+ * A (reasonably) fast way of allowing switchable and remappable process address spaces. It loosely
+ * mimics the way a real CPU page table works.
+ */
+struct PageTable {
+    explicit PageTable(std::size_t page_size_in_bits);
+    ~PageTable();
+
+    /**
+     * Resizes the page table to be able to accomodate enough pages within
+     * a given address space.
+     *
+     * @param address_space_width_in_bits The address size width in bits.
+     */
+    void Resize(std::size_t address_space_width_in_bits);
+
+    /**
+     * Vector of memory pointers backing each page. An entry can only be non-null if the
+     * corresponding entry in the `attributes` vector is of type `Memory`.
+     */
+    std::vector<u8*> pointers;
+
+    /**
+     * Contains MMIO handlers that back memory regions whose entries in the `attribute` vector is
+     * of type `Special`.
+     */
+    boost::icl::interval_map<VAddr, std::set<SpecialRegion>> special_regions;
+
+    /**
+     * Vector of fine grained page attributes. If it is set to any value other than `Memory`, then
+     * the corresponding entry in `pointers` MUST be set to null.
+     */
+    std::vector<PageType> attributes;
+
+    const std::size_t page_size_in_bits{};
+};
+
+} // namespace Common