Kernel: Rename Kernel/VM/ to Kernel/Memory/

This directory isn't just about virtual memory, it's about all kinds
of memory management.

Kernel/Memory/MappedROM.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/OwnPtr.h>
+#include <Kernel/Memory/Region.h>
+#include <Kernel/PhysicalAddress.h>
+
+namespace Kernel {
+
+class MappedROM {
+public:
+    const u8* base() const { return region->vaddr().offset(offset).as_ptr(); }
+    const u8* end() const { return base() + size; }
+    OwnPtr<Region> region;
+    size_t size { 0 };
+    size_t offset { 0 };
+    PhysicalAddress paddr;
+
+    Optional<PhysicalAddress> find_chunk_starting_with(StringView prefix, size_t chunk_size) const
+    {
+        for (auto* candidate = base(); candidate < end(); candidate += chunk_size) {
+            if (!__builtin_memcmp(prefix.characters_without_null_termination(), candidate, prefix.length()))
+                return paddr_of(candidate);
+        }
+        return {};
+    }
+
+    PhysicalAddress paddr_of(const u8* ptr) const { return paddr.offset(ptr - this->base()); }
+};
+
+}