Kernel: Implement MAP_PRIVATE file mappings

mmap() now supports mapping files with MAP_PRIVATE.

kernel/include/kernel/Memory/FileBackedRegion.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <kernel/FS/Inode.h>
+#include <kernel/Memory/MemoryRegion.h>
+
+namespace Kernel
+{
+
+	class FileBackedRegion final : public MemoryRegion
+	{
+		BAN_NON_COPYABLE(FileBackedRegion);
+		BAN_NON_MOVABLE(FileBackedRegion);
+
+	public:
+		static BAN::ErrorOr<BAN::UniqPtr<FileBackedRegion>> create(BAN::RefPtr<Inode>, PageTable&, off_t offset, size_t size, AddressRange address_range, Type, PageTable::flags_t);
+		~FileBackedRegion();
+
+		virtual BAN::ErrorOr<bool> allocate_page_containing(vaddr_t vaddr) override;
+
+		virtual BAN::ErrorOr<BAN::UniqPtr<MemoryRegion>> clone(PageTable& new_page_table) override;
+
+	private:
+		FileBackedRegion(BAN::RefPtr<Inode>, PageTable&, off_t offset, ssize_t size, Type flags, PageTable::flags_t page_flags);
+
+	private:
+		BAN::RefPtr<Inode> m_inode;
+		const off_t m_offset;
+	};
+
+}

kernel/include/kernel/Memory/MemoryRegion.h

@@ -21,7 +21,7 @@ namespace Kernel
 		BAN_NON_MOVABLE(MemoryRegion);
 
 	public:
-		enum Type : uint8_t
+		enum class Type : uint8_t
 		{
 			PRIVATE,
 			SHARED

kernel/include/kernel/OpenFileDescriptorSet.h

@@ -48,6 +48,7 @@ namespace Kernel
 
 		BAN::ErrorOr<BAN::StringView> path_of(int) const;
 		BAN::ErrorOr<BAN::RefPtr<Inode>> inode_of(int);
+		BAN::ErrorOr<int> flags_of(int) const;
 
 	private:
 		struct OpenFileDescription : public BAN::RefCounted<OpenFileDescription>