From 0c4fd9eaed4a71975879aa83cd2da4b6266a64b5 Mon Sep 17 00:00:00 2001
From: Fabian Imhof <fabian.imhof@ost.ch>
Date: Tue, 15 Oct 2024 15:48:43 +0000
Subject: add 4th level page table

---
 arch/x86_64/include/arch/memory/paging.hpp | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

(limited to 'arch/x86_64/include')

diff --git a/arch/x86_64/include/arch/memory/paging.hpp b/arch/x86_64/include/arch/memory/paging.hpp
index 16fa476..7b705ac 100644
--- a/arch/x86_64/include/arch/memory/paging.hpp
+++ b/arch/x86_64/include/arch/memory/paging.hpp
@@ -91,6 +91,9 @@ namespace teachos::arch::memory
      */
     auto contains_flags(std::bitset<64U> other) const -> bool;
 
+    std::bitset<64U> flags;  ///< Underlying bitset used to read the flags from. Bits 9 - 11 and 52 - 62 can be freely
+                             ///< used for additional flags by the operating system.
+
   private:
     /**
      * @brief Extracts the physical address from the underlying bitset read from bit index 12 - 51. Is a 52 bit page
@@ -100,9 +103,6 @@ namespace teachos::arch::memory
      * @return Extracted physical address of the next page or of the frame for P1 page tables.
      */
     auto calculate_physical_address() const -> std::size_t;
-
-    std::bitset<64U> flags;  ///< Underlying bitset used to read the flags from. Bits 9 - 11 and 52 - 62 can be freely
-                             ///< used for additional flags by the operating system.
   };
 
   /**
@@ -115,6 +115,25 @@ namespace teachos::arch::memory
      */
     auto zero_entries() -> void;
 
+    /**
+     * @brief Find and return the next table address
+     *
+     * The next table address is only valid if the corresponding entry is present
+     * and does not create a huge page
+     *
+     * @param index
+     * @return An optional of the address of the next page table or null
+     */
+    auto next_table_address(std::size_t index) const -> std::optional<std::size_t>;
+
+    /**
+     * @brief Convert the address of a page_table into a page_table
+     *
+     * @param index
+     * @return An optional of the next page table or null
+     */
+    auto next_table(size_t index) const -> std::optional<const page_table *>;
+
     /**
      * @brief Index operator overload to access specific entries directy
      *
@@ -129,6 +148,7 @@ namespace teachos::arch::memory
 
   private:
     entry entries[PAGE_TABLE_ENTRY_COUNT];
+    page_table const * p4 = reinterpret_cast<page_table *>(0xfffffffffffff000);
   };
 }  // namespace teachos::arch::memory
 
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