add 4th level page table

1 files changed, 27 insertions, 0 deletions

diff --git a/arch/x86_64/src/memory/paging.cpp b/arch/x86_64/src/memory/paging.cpp
index 445c796..61d9d0f 100644
--- a/arch/x86_64/src/memory/paging.cpp
+++ b/arch/x86_64/src/memory/paging.cpp
@@ -50,4 +50,31 @@ namespace teachos::arch::memory
       entry->set_unused();
     }
   }
+
+  auto page_table::next_table_address(std::size_t index) const -> std::optional<std::size_t>
+  {
+    auto entry = entries[index];
+
+    if (entry.contains_flags(entry.PRESENT) && !entry.contains_flags(entry.HUGE_PAGE))
+    {
+      std::size_t table_address = reinterpret_cast<std::size_t>(this);
+      return (table_address << 9) | (index << 12);
+    }
+    else
+    {
+      return std::nullopt;
+    }
+  }
+
+  auto page_table::next_table(size_t index) const -> std::optional<const page_table *>
+  {
+    auto address = next_table_address(index);
+
+    if (address.has_value())
+    {
+      return reinterpret_cast<const page_table *>(*address);
+    }
+
+    return std::nullopt;
+  }
 }  // namespace teachos::arch::memory