Use virtual level 4 address again

2 files changed, 7 insertions, 3 deletions

diff --git a/arch/x86_64/src/memory/paging/page_mapper.cpp b/arch/x86_64/src/memory/paging/page_mapper.cpp
index 995f2c3..687bffd 100644
--- a/arch/x86_64/src/memory/paging/page_mapper.cpp
+++ b/arch/x86_64/src/memory/paging/page_mapper.cpp
@@ -6,13 +6,15 @@ namespace teachos::arch::memory::paging
 {
   namespace
   {
-    static page_table * PAGE_TABLE_LEVEL_4_ADDRESS = boot::page_map_level_4;
+    constexpr size_t PAGE_TABLE_LEVEL_4_ADDRESS = 0xfffffffffffff000;
   }  // namespace
 
   auto create_or_get() -> page_table_handle
   {
+    // Perhaps we need to access boot::page_map_level_4; so we do not crash when returning entry?
+    static page_table * const active_page = reinterpret_cast<page_table *>(PAGE_TABLE_LEVEL_4_ADDRESS);
     // We can not save page_table_handle as a static variable directly, if we do the program will fail to link.
-    return page_table_handle{PAGE_TABLE_LEVEL_4_ADDRESS, page_table_handle::LEVEL4};
+    return page_table_handle{active_page, page_table_handle::LEVEL4};
   }
 
   auto translate_page(virtual_page page) -> std::optional<allocator::physical_frame>
diff --git a/arch/x86_64/src/memory/paging/page_table.cpp b/arch/x86_64/src/memory/paging/page_table.cpp
index 40662e3..bfd91da 100644
--- a/arch/x86_64/src/memory/paging/page_table.cpp
+++ b/arch/x86_64/src/memory/paging/page_table.cpp
@@ -51,6 +51,7 @@ namespace teachos::arch::memory::paging
   auto page_table::zero_entries() -> void
   {
     constexpr size_t entry_amount = sizeof(entries) / sizeof(entries[0]);
+    static_assert(entry_amount == PAGE_TABLE_ENTRY_COUNT);
     for (size_t i = 0; i < entry_amount; ++i)
     {
       auto entry = this->operator[](i);
@@ -73,7 +74,8 @@ namespace teachos::arch::memory::paging
     // 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.
     exception_handling::assert(index < PAGE_TABLE_ENTRY_COUNT, "[Page Table] Index out of bounds");
-    return entries[index];
+    auto & entry = entries[index];
+    return entry;
   }
 
   auto page_table::next_table_address(std::size_t table_index) -> std::optional<std::size_t>