Unmap all empty page tables in unmap function.

3 files changed, 22 insertions, 15 deletions

diff --git a/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp b/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp
index 8e971f0..599723f 100644
--- a/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp
+++ b/arch/x86_64/include/arch/memory/allocator/area_frame_allocator.hpp
@@ -41,6 +41,10 @@ namespace teachos::arch::memory::allocator
     /**
      * @brief Deallocates a previously allocated physical_frame.
      *
+     * @note Simply does nothing, because the simply area frame
+     * allocator implementation does not keep track of free or used frames and can therefore not deallocate, because it
+     * does not know which frames have ben alocated in the first place.
+     *
      * @param physical_frame Previously allocated physical_frame that should be allocated.
      */
     auto deallocate_frame(physical_frame physical_frame) -> void;
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 801ccfb..a9f8eb8 100644
--- a/arch/x86_64/include/arch/memory/paging/page_mapper.hpp
+++ b/arch/x86_64/include/arch/memory/paging/page_mapper.hpp
@@ -158,26 +158,34 @@ namespace teachos::arch::memory::paging
                                "[Page Mapper] Attempted to unmap page, which has not been mapped previously");
 
     auto current_handle = create_or_get();
-
-    std::array<page_table_handle *, 4> handles{};
+    std::array<page_table_handle, 4U> handles{current_handle, current_handle, current_handle, current_handle};
 
     for (auto level = page_table_handle::LEVEL4; level != page_table_handle::LEVEL1; --level)
     {
-      handles[level] = *current_handle;
-
       auto const level_index = page.get_level_index(level);
       auto const next_handle = current_handle.next_table(level_index);
       // The next table method failed even tough the page has to be mapped already, because translate_page did not fail.
       // This can only mean that we attempted to unmap a huge page, which is not supported in the first place.
       exception_handling::assert(next_handle.has_value(), "[Page Mapper] Unable to unmap huge pages");
       current_handle = next_handle.value();
+      // The level is used as the index, because it ensures the first level is the lowest one and then the remaining
+      // levels in ascending order. This is required, because we first have to clear the Level 1 page entry to check if
+      // the Level 1 page is now empty, to clear the Level 2 page entry, which will then also check if the Level 2 page
+      // is empty and clear the Level 3 page entry and so on.
+      handles.at(level - 1U) = current_handle;
     }
 
-    std::ranges::for_each(handles, [&allocator, page](page_table_handle * handle) {
-      exception_handling::assert(handle != nullptr, "[Page Mapper] Attempted to unmap page behind nullpointer");
-      unmap_page_table_entry(allocator, page, *handle);
-    });
-
+    // Unmaps all entries starting from the Level 1 page table, and unmaps higher levels as well if that entry was the
+    // last one. We check if it was the last one using is empty on the page table handle, when we have removed the page
+    // to be unmapped.
+    for (auto & handle : handles)
+    {
+      unmap_page_table_entry(allocator, page, handle);
+      if (!handle.is_empty())
+      {
+        break;
+      }
+    }
     invalidate_page_cache(page.start_address());
   }
 }  // namespace teachos::arch::memory::paging
diff --git a/arch/x86_64/src/memory/allocator/area_frame_allocator.cpp b/arch/x86_64/src/memory/allocator/area_frame_allocator.cpp
index e79cd8b..1e87147 100644
--- a/arch/x86_64/src/memory/allocator/area_frame_allocator.cpp
+++ b/arch/x86_64/src/memory/allocator/area_frame_allocator.cpp
@@ -83,10 +83,5 @@ namespace teachos::arch::memory::allocator
     return allocate_frame();
   }
 
-  auto area_frame_allocator::deallocate_frame(physical_frame physical_frame) -> void
-  {
-    // TODO: Fix create acutal deallocation of frames if it is even possible. Can the area frame allocator even
-    // deallocate in the first place?
-    next_free_frame = physical_frame;
-  }
+  auto area_frame_allocator::deallocate_frame(physical_frame physical_frame) -> void { (void)physical_frame; }
 }  // namespace teachos::arch::memory::allocator