UserspaceEmulator: Start sketching out a SoftMMU class :^)

This Emulator sub-object will keep track of all active memory regions
and handle memory read/write operations from the CPU.

A memory region is currently represented by a virtual Region object
that can implement arbitrary behavior by overriding read/write ops.

DevTools/UserspaceEmulator/SoftMMU.h

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/NonnullOwnPtrVector.h>
+#include <AK/Types.h>
+
+namespace UserspaceEmulator {
+
+class SoftMMU {
+public:
+    class Region {
+    public:
+        virtual ~Region() { }
+
+        u32 base() const { return m_base; }
+        u32 size() const { return m_size; }
+        u32 end() const { return m_base + m_size; }
+
+        bool contains(u32 address) const { return address >= base() && address < end(); }
+
+        virtual void write32(u32 offset, u32 value) = 0;
+        virtual u32 read32(u32 offset) = 0;
+
+    protected:
+        Region(u32 base, u32 size)
+            : m_base(base)
+            , m_size(size)
+        {
+        }
+
+    private:
+        u32 m_base { 0 };
+        u32 m_size { 0 };
+    };
+
+    u32 read32(u32 address);
+    void write32(u32 address, u32 value);
+
+    Region* find_region(u32 address);
+    void add_region(NonnullOwnPtr<Region>);
+
+private:
+    NonnullOwnPtrVector<Region> m_regions;
+};
+
+}