5 files changed, 99 insertions, 25 deletions
diff --git a/arch/x86_64/src/kernel/main.cpp b/arch/x86_64/src/kernel/main.cpp
index c0d4aed..09fc2a2 100644
--- a/arch/x86_64/src/kernel/main.cpp
+++ b/arch/x86_64/src/kernel/main.cpp
@@ -1,7 +1,7 @@
 #include "arch/kernel/main.hpp"
 
 #include "arch/exception_handling/assert.hpp"
-#include "arch/memory/frame_allocator.hpp"
+#include "arch/memory/allocator/area_frame_allocator.hpp"
 #include "arch/memory/multiboot/reader.hpp"
 #include "arch/video/vga/text.hpp"
 
@@ -18,7 +18,7 @@ namespace teachos::arch::kernel
     text::write("TeachOS is starting up...", text::common_attributes::green_on_black);
 
     auto memory_information = memory::multiboot::read_multiboot2();
-    auto allocator = memory::area_frame_allocator(memory_information);
+    memory::allocator::area_frame_allocator allocator(memory_information);
 
     auto last_allocated = allocator.allocate_frame();
     auto allocated = last_allocated;
diff --git a/arch/x86_64/src/memory/frame_allocator.cpp b/arch/x86_64/src/memory/allocator/area_frame_allocator.cpp
index 7776082..9c344d8 100644
--- a/arch/x86_64/src/memory/frame_allocator.cpp
+++ b/arch/x86_64/src/memory/allocator/area_frame_allocator.cpp
@@ -1,22 +1,9 @@
-#include "arch/memory/frame_allocator.hpp"
+#include "arch/memory/allocator/area_frame_allocator.hpp"
 
 #include "arch/exception_handling/assert.hpp"
 
-namespace teachos::arch::memory
+namespace teachos::arch::memory::allocator
 {
-  physical_frame::physical_frame(std::size_t frame_number)
-      : frame_number(frame_number)
-  {
-    // Nothing to do
-  }
-
-  auto physical_frame::containing_address(std::size_t address) -> physical_frame
-  {
-    return physical_frame{address / PAGE_FRAME_SIZE};
-  }
-
-  auto physical_frame::start_address() const -> uint64_t { return frame_number * PAGE_FRAME_SIZE; }
-
   area_frame_allocator::area_frame_allocator(multiboot::memory_information mem_info)
       : next_free_frame(0)
       , current_area(std::nullopt)
@@ -81,7 +68,7 @@ namespace teachos::arch::memory
       else if (physical_frame >= multiboot_start && physical_frame <= kernel_end)
       {
         // `physical_frame` is used by the kernel or multiboot information structure
-        next_free_frame = arch::memory::physical_frame{kernel_end.frame_number + 1};
+        next_free_frame = allocator::physical_frame{kernel_end.frame_number + 1};
       }
       else
       {
@@ -107,4 +94,4 @@ namespace teachos::arch::memory
   auto area_frame_allocator::begin() -> multiboot::memory_area_iterator { return area_begin; }
 
   auto area_frame_allocator::end() -> multiboot::memory_area_iterator { return area_end; }
-}  // namespace teachos::arch::memory
+}  // namespace teachos::arch::memory::allocator
diff --git a/arch/x86_64/src/memory/allocator/physical_frame.cpp b/arch/x86_64/src/memory/allocator/physical_frame.cpp
new file mode 100644
index 0000000..03ec193
--- /dev/null
+++ b/arch/x86_64/src/memory/allocator/physical_frame.cpp
@@ -0,0 +1,22 @@
+#include "arch/memory/allocator/physical_frame.hpp"
+
+namespace teachos::arch::memory::allocator
+{
+  namespace
+  {
+    constexpr std::size_t PAGE_FRAME_SIZE = 4096U;  ///< Default page size of x86_84 is always 4KiB.
+  }
+
+  physical_frame::physical_frame(std::size_t frame_number)
+      : frame_number(frame_number)
+  {
+    // Nothing to do
+  }
+
+  auto physical_frame::containing_address(std::size_t address) -> physical_frame
+  {
+    return physical_frame{address / PAGE_FRAME_SIZE};
+  }
+
+  auto physical_frame::start_address() const -> uint64_t { return frame_number * PAGE_FRAME_SIZE; }
+}  // namespace teachos::arch::memory::allocator
diff --git a/arch/x86_64/src/memory/paging.cpp b/arch/x86_64/src/memory/paging/page_entry.cpp
index 9774132..43c0b71 100644
--- a/arch/x86_64/src/memory/paging.cpp
+++ b/arch/x86_64/src/memory/paging/page_entry.cpp
@@ -1,19 +1,19 @@
-#include "arch/memory/paging.hpp"
+#include "arch/memory/paging/page_entry.hpp"
 
 #include "arch/exception_handling/assert.hpp"
 
-namespace teachos::arch::memory
+namespace teachos::arch::memory::paging
 {
   auto entry::is_unused() const -> bool { return flags == 0U; }
 
   auto entry::set_unused() -> void { flags = 0U; }
 
-  auto entry::calculate_pointed_to_frame() const -> std::optional<physical_frame>
+  auto entry::calculate_pointed_to_frame() const -> std::optional<allocator::physical_frame>
   {
     if (contains_flags(PRESENT))
     {
       auto physical_address = calculate_physical_address();
-      return physical_frame::containing_address(physical_address);
+      return allocator::physical_frame::containing_address(physical_address);
     }
     return std::nullopt;
   }
@@ -33,10 +33,10 @@ namespace teachos::arch::memory
 
   auto entry::contains_flags(std::bitset<64U> other) const -> bool { return (flags & other) == other; }
 
-  auto entry::set_address(physical_frame frame) -> void
+  auto entry::set_address(allocator::physical_frame frame) -> void
   {
     arch::exception_handling::assert((frame.start_address() & ~0x000fffff'fffff000) == 0,
                                      "Start address is not aligned with Page");
     flags = std::bitset<64U>(frame.start_address()) | flags;
   }
-}  // namespace teachos::arch::memory
+}  // namespace teachos::arch::memory::paging
diff --git a/arch/x86_64/src/memory/paging/page_table.cpp b/arch/x86_64/src/memory/paging/page_table.cpp
new file mode 100644
index 0000000..a1cbc72
--- /dev/null
+++ b/arch/x86_64/src/memory/paging/page_table.cpp
@@ -0,0 +1,65 @@
+#include "arch/memory/paging/page_table.hpp"
+
+#include "arch/exception_handling/assert.hpp"
+
+namespace teachos::arch::memory::paging
+{
+  page_table::page_table()
+      : current_level(LEVEL4)
+      , current_table(reinterpret_cast<table_content *>(0xfffffffffffff000))
+  {
+    // Nothing to do
+  }
+
+  auto page_table::zero_entries() -> void
+  {
+    constexpr size_t entry_amount = sizeof(current_table->entries) / sizeof(current_table->entries[0]);
+    for (size_t i = 0; i < entry_amount; ++i)
+    {
+      auto entry = this->operator[](i);
+      entry.set_unused();
+    }
+  }
+
+  auto page_table::next_table(std::size_t table_index) -> void
+  {
+    arch::exception_handling::assert(current_level != LEVEL1,
+                                     "[Page Table] Attempted to call next_table on level 1 page table");
+    auto address = next_table_address(table_index);
+
+    if (address.has_value())
+    {
+      current_table = reinterpret_cast<table_content *>(*address);
+      current_level = static_cast<level>(current_level - 1U);
+    }
+  }
+
+  auto page_table::operator[](std::size_t index) -> entry &
+  {
+    // C array is not bounds checked, therefore we have to check ourselves, to ensure no out of bounds reads, which
+    // could be incredibly hard to debug later.
+    arch::exception_handling::assert(index < PAGE_TABLE_ENTRY_COUNT, "[Page Table] index out of bounds");
+    return current_table->entries[index];
+  }
+
+  auto page_table::operator[](std::size_t index) const -> entry const &
+  {
+    // C array is not bounds checked, therefore we have to check ourselves, to ensure no out of bounds reads, which
+    // could be incredibly hard to debug later.
+    arch::exception_handling::assert(index < PAGE_TABLE_ENTRY_COUNT, "[Page Table] index out of bounds");
+    return current_table->entries[index];
+  }
+
+  auto page_table::next_table_address(std::size_t table_index) const -> std::optional<std::size_t>
+  {
+    auto entry = this->operator[](table_index);
+
+    if (entry.contains_flags(entry::PRESENT) && !entry.contains_flags(entry::HUGE_PAGE))
+    {
+      std::size_t const table_address = reinterpret_cast<std::size_t>(this);
+      return (table_address << 9) | (table_index << 12);
+    }
+    // TODO: Implement behaviour for huge pages currently not done
+    return std::nullopt;
+  }
+}  // namespace teachos::arch::memory::paging