text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #pragma once
  
  #include <AK/HashMap.h>
  #include <AK/IntrusiveRedBlackTree.h>
  #include <AK/RefCounted.h>
  #include <AK/RefPtr.h>
  #include <Kernel/Forward.h>
  #include <Kernel/Memory/PhysicalPage.h>
  #include <Kernel/Memory/VirtualRangeAllocator.h>
  
  namespace Kernel::Memory {
  
  class PageDirectory : public RefCounted<PageDirectory> {
      friend class MemoryManager;
  
  public:
      static KResultOr<NonnullRefPtr<PageDirectory>> try_create_for_userspace(VirtualRangeAllocator const* parent_range_allocator = nullptr);
      static NonnullRefPtr<PageDirectory> must_create_kernel_page_directory();
      static RefPtr<PageDirectory> find_by_cr3(FlatPtr);
  
      ~PageDirectory();
  
      void allocate_kernel_directory();
  
      FlatPtr cr3() const
      {
  #if ARCH(X86_64)
          return m_pml4t->paddr().get();
  #else
          return m_directory_table->paddr().get();
  #endif
      }
  
      VirtualRangeAllocator& range_allocator() { return m_range_allocator; }
      VirtualRangeAllocator const& range_allocator() const { return m_range_allocator; }
  
      AddressSpace* address_space() { return m_space; }
      const AddressSpace* address_space() const { return m_space; }
  
      void set_space(Badge<AddressSpace>, AddressSpace& space) { m_space = &space; }
  
      RecursiveSpinlock& get_lock() { return m_lock; }
  
      // This has to be public to let the global singleton access the member pointer
      IntrusiveRedBlackTreeNode<FlatPtr, PageDirectory, RawPtr<PageDirectory>> m_tree_node;
  
  private:
      PageDirectory();
  
      AddressSpace* m_space { nullptr };
      VirtualRangeAllocator m_range_allocator;
  #if ARCH(X86_64)
      RefPtr<PhysicalPage> m_pml4t;
  #endif
      RefPtr<PhysicalPage> m_directory_table;
  #if ARCH(X86_64)
      RefPtr<PhysicalPage> m_directory_pages[512];
  #else
      RefPtr<PhysicalPage> m_directory_pages[4];
  #endif
      HashMap<FlatPtr, NonnullRefPtr<PhysicalPage>> m_page_tables;
      RecursiveSpinlock m_lock;
  };
  
  }
  