From d934ea6875932a7139eba77bb5248fca8be7fd01 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matteo=20Gm=C3=BCr?= <matteo.gmuer1@ost.ch>
Date: Sun, 20 Oct 2024 08:37:49 +0000
Subject: =?UTF-8?q?Implement=20translate=20page=20in=20a=20big=20brain=20w?=
 =?UTF-8?q?ay=20=F0=9F=A4=AF?=
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---
 .../include/arch/memory/paging/page_table.hpp      |  2 ++
 .../include/arch/memory/paging/virtual_page.hpp    | 32 +++++++++-------------
 arch/x86_64/src/memory/paging/page_table.cpp       |  8 ++++++
 3 files changed, 23 insertions(+), 19 deletions(-)

(limited to 'arch/x86_64')

diff --git a/arch/x86_64/include/arch/memory/paging/page_table.hpp b/arch/x86_64/include/arch/memory/paging/page_table.hpp
index aa8bd5e..0fe667c 100644
--- a/arch/x86_64/include/arch/memory/paging/page_table.hpp
+++ b/arch/x86_64/include/arch/memory/paging/page_table.hpp
@@ -87,6 +87,8 @@ namespace teachos::arch::memory::paging
                           ///< 1 page table
     table_content * current_table;  ///< Current table we are accessing and indexing.
   };
+
+  auto operator--(page_table::level & level, int) -> page_table::level;
 }  // namespace teachos::arch::memory::paging
 
 #endif  // TEACHOS_ARCH_X86_64_MEMORY_PAGING_PAGE_TABLE_HPP
diff --git a/arch/x86_64/include/arch/memory/paging/virtual_page.hpp b/arch/x86_64/include/arch/memory/paging/virtual_page.hpp
index 46140ff..705de29 100644
--- a/arch/x86_64/include/arch/memory/paging/virtual_page.hpp
+++ b/arch/x86_64/include/arch/memory/paging/virtual_page.hpp
@@ -67,31 +67,25 @@ namespace teachos::arch::memory::paging
   auto translate_page(virtual_page page) -> std::optional<allocator::physical_frame>
   {
     page_table page_table{};
-    bool is_valid = page_table.next_table(page.get_level_index(page_table::LEVEL4));
+    bool is_valid = false;
+    auto huge_page = []() -> std::optional<allocator::physical_frame> { return std::nullopt; };
 
-    auto huge_page = []() -> std::optional<allocator::physical_frame> {
-      // TODO
-      return std::nullopt;
-    };
-
-    if (is_valid)
+    for (auto level = page_table::LEVEL4; level != page_table::LEVEL1; level--)
     {
-      is_valid = page_table.next_table(page.get_level_index(page_table::LEVEL3));
-
-      if (is_valid)
+      is_valid = page_table.next_table(page.get_level_index(level));
+      if (!is_valid)
       {
-        is_valid = page_table.next_table(page.get_level_index(page_table::LEVEL2));
-
-        if (is_valid)
-        {
-          std::size_t level1_index = page.get_level_index(page_table::LEVEL1);
-          std::optional<allocator::physical_frame> frame = page_table[level1_index].calculate_pointed_to_frame();
-
-          return frame;
-        }
+        break;
       }
     }
 
+    if (is_valid)
+    {
+      auto level1_index = page.get_level_index(page_table::LEVEL1);
+      auto frame = page_table[level1_index].calculate_pointed_to_frame();
+      return frame;
+    }
+
     return huge_page();
   }
 
diff --git a/arch/x86_64/src/memory/paging/page_table.cpp b/arch/x86_64/src/memory/paging/page_table.cpp
index ab7331a..02ababe 100644
--- a/arch/x86_64/src/memory/paging/page_table.cpp
+++ b/arch/x86_64/src/memory/paging/page_table.cpp
@@ -54,4 +54,12 @@ namespace teachos::arch::memory::paging
     }
     return std::nullopt;
   }
+
+  auto operator--(page_table::level & level, int) -> page_table::level
+  {
+    exception_handling::assert(level != page_table::LEVEL1,
+                               "[Page table] Attemptd to decrement enum to value outside of range");
+    auto value = static_cast<std::underlying_type<page_table::level>::type>(level);
+    return static_cast<page_table::level>(--value);
+  }
 }  // namespace teachos::arch::memory::paging
-- 
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