From 1b03bcecac1276b486e17daf0384de7fa203d974 Mon Sep 17 00:00:00 2001
From: Fabian Imhof <fabian.imhof@ost.ch>
Date: Sun, 20 Oct 2024 12:57:21 +0000
Subject: create active_page_table

---
 .../arch/memory/paging/active_page_table.hpp       | 31 ++++++++++++++++++++++
 .../include/arch/memory/paging/page_mapper.hpp     |  1 -
 .../x86_64/src/memory/paging/active_page_table.cpp | 31 ++++++++++++++++++++++
 3 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86_64/include/arch/memory/paging/active_page_table.hpp
 create mode 100644 arch/x86_64/src/memory/paging/active_page_table.cpp

(limited to 'arch/x86_64')

diff --git a/arch/x86_64/include/arch/memory/paging/active_page_table.hpp b/arch/x86_64/include/arch/memory/paging/active_page_table.hpp
new file mode 100644
index 0000000..4a94b40
--- /dev/null
+++ b/arch/x86_64/include/arch/memory/paging/active_page_table.hpp
@@ -0,0 +1,31 @@
+#ifndef TEACHOS_ARCH_X86_64_MEMORY_PAGING_VIRTUAL_PAGE_HPP
+#define TEACHOS_ARCH_X86_64_MEMORY_PAGING_VIRTUAL_PAGE_HPP
+
+#include "arch/memory/paging/page_table.hpp"
+
+namespace teachos::arch::memory::paging
+{
+
+  struct active_page_table
+  {
+    /**
+     * @brief Ensures only one instance of active_page_table exists.
+     *
+     * @param level4_page_table A pointer to the level 4 page table.
+     * @return The only instance of active_page_table.
+     */
+    auto create(page_table * level4_page_table) -> active_page_table *;
+
+  private:
+    /**
+     * @brief Construct a new active page table object.
+     *
+     * @param level4_page_table A pointer to the level 4 page table.
+     */
+    active_page_table(page_table * level4_page_table);
+
+    bool instantiated = false;       ///< Indicates wether an instance already exists.
+    page_table * level4_page_table;  ///< The active level4 page table.
+  };
+}  // namespace teachos::arch::memory::paging
+#endif
\ No newline at end of file
diff --git a/arch/x86_64/include/arch/memory/paging/page_mapper.hpp b/arch/x86_64/include/arch/memory/paging/page_mapper.hpp
index 5bdd82a..ae3502e 100644
--- a/arch/x86_64/include/arch/memory/paging/page_mapper.hpp
+++ b/arch/x86_64/include/arch/memory/paging/page_mapper.hpp
@@ -48,7 +48,6 @@ namespace teachos::arch::memory::paging
   template<allocator::FrameAllocator T>
   auto map_page_to_frame(T & allocator, virtual_page page, allocator::physical_frame frame,
                          std::bitset<64U> flags) -> void
-
   {
     page_table page_table{};
     bool table_exists = false;
diff --git a/arch/x86_64/src/memory/paging/active_page_table.cpp b/arch/x86_64/src/memory/paging/active_page_table.cpp
new file mode 100644
index 0000000..eb85c34
--- /dev/null
+++ b/arch/x86_64/src/memory/paging/active_page_table.cpp
@@ -0,0 +1,31 @@
+#include "arch/memory/paging/active_page_table.hpp"
+
+namespace teachos::arch::memory::paging
+{
+  struct active_page_table
+  {
+    auto create(page_table * level4_page_table) -> active_page_table *
+    {
+      if (instantiated)
+      {
+        return this;
+      }
+
+      instantiated = true;
+      return &active_page_table(level4_page_table);
+    }
+
+    active_page_table(const active_page_table &) = delete;
+    active_page_table & operator=(const active_page_table &) = delete;
+
+  private:
+    active_page_table(page_table * level4_page_table)
+        : level4_page_table(level4_page_table)
+    {
+      // Nothing to do
+    }
+
+    bool instantiated = false;
+    page_table * level4_page_table;
+  };
+}  // namespace teachos::arch::memory::paging
\ No newline at end of file
-- 
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