x86_64/memory: extract PML4 injection

6 files changed, 103 insertions, 84 deletions

diff --git a/arch/x86_64/include/x86_64/memory/page_table.hpp b/arch/x86_64/include/x86_64/memory/page_table.hpp
index 53af5d0..6b8eb8c 100644
--- a/arch/x86_64/include/x86_64/memory/page_table.hpp
+++ b/arch/x86_64/include/x86_64/memory/page_table.hpp
@@ -74,6 +74,9 @@ namespace teachos::memory::x86_64
     //! Clear the entire page table, effectively evicting all entries.
     auto clear() -> void;
 
+    //! Check if the page table is empty.
+    [[nodiscard]] auto empty() const noexcept -> bool;
+
   private:
     std::array<entry, entry_count> m_entries{};
   };
diff --git a/arch/x86_64/include/x86_64/memory/scoped_mapping.hpp b/arch/x86_64/include/x86_64/memory/scoped_mapping.hpp
index 1719e6b..5737bb0 100644
--- a/arch/x86_64/include/x86_64/memory/scoped_mapping.hpp
+++ b/arch/x86_64/include/x86_64/memory/scoped_mapping.hpp
@@ -12,7 +12,7 @@ namespace teachos::memory::x86_64
   {
     scoped_mapping(scoped_mapping const &) = delete;
     scoped_mapping(scoped_mapping &&);
-    scoped_mapping(linear_address address, frame_allocator & allocator);
+    scoped_mapping(page page, frame_allocator & allocator);
 
     ~scoped_mapping();
 
@@ -29,7 +29,7 @@ namespace teachos::memory::x86_64
     }
 
   private:
-    linear_address m_address;
+    page m_page;
     frame_allocator * m_allocator;
     bool m_mapped;
   };
diff --git a/arch/x86_64/src/kapi/memory.cpp b/arch/x86_64/src/kapi/memory.cpp
index 920c82b..36b1706 100644
--- a/arch/x86_64/src/kapi/memory.cpp
+++ b/arch/x86_64/src/kapi/memory.cpp
@@ -1,6 +1,5 @@
 #include "kapi/memory.hpp"
 
-#include "kapi/cio.hpp"
 #include "kapi/system.hpp"
 
 #include "x86_64/boot/boot.hpp"
@@ -28,7 +27,8 @@ namespace teachos::memory
     // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
     auto constinit allocator = static_cast<frame_allocator *>(nullptr);
 
-    constexpr auto static unused_page_address = 0x0000'7fff'cafe'faceuz;
+    constexpr auto static unused_page_address = linear_address{0x0000'7fff'cafe'faceuz};
+    constexpr auto static recursive_page_map_index = 510;
 
     auto create_memory_information() -> x86_64::region_allocator::memory_information
     {
@@ -61,62 +61,18 @@ namespace teachos::memory
 
     auto inject_faux_pml4(frame_allocator & allocator) -> void
     {
-      using entry_flags = x86_64::page_table::entry::flags;
-      using page_table = x86_64::page_table;
-
-      auto temporary_page = page::containing(linear_address{unused_page_address});
-      auto temporary_page_address = temporary_page.start_address();
-
-      auto & pml4 = x86_64::paging_root::get();
-
-      // NOLINTBEGIN(cppcoreguidelines-avoid-magic-numbers)
-      auto faux_pml4_frame =
-          allocator.allocate()
-              .and_then([&](auto frame) -> auto {
-                auto index = temporary_page_address >> 39 & 0x1ffu;
-                pml4[index].frame(frame, entry_flags::present | entry_flags::writable);
-                return pml4.next(index);
-              })
-              .and_then([&](auto pml) -> auto {
-                std::construct_at(pml);
-                auto index = temporary_page_address >> 30 & 0x1ffu;
-                (*pml)[index].frame(*allocator.allocate(), entry_flags::present | entry_flags::writable);
-                return pml->next(index);
-              })
-              .and_then([&](auto pml) -> auto {
-                std::construct_at(pml);
-                auto index = temporary_page_address >> 21 & 0x1ffu;
-                (*pml)[index].frame(*allocator.allocate(), entry_flags::present | entry_flags::writable);
-                return pml->next(index);
-              })
-              .transform([&](auto pml) -> auto {
-                std::construct_at(pml);
-                auto index = temporary_page_address >> 12 & 0x1ffu;
-                (*pml)[index].frame(*allocator.allocate(), entry_flags::present | entry_flags::writable);
-                return pml;
-              })
-              .and_then([&](auto pml) -> auto {
-                auto faux_pml4_pointer = std::bit_cast<page_table *>(temporary_page_address.raw());
-                auto faux_pml4 = std::construct_at<page_table>(faux_pml4_pointer);
-
-                auto index = temporary_page_address >> 12 & 0x1ffu;
-                auto frame = (*pml)[index].frame();
-
-                (*faux_pml4)[510].frame(*frame, entry_flags::present | entry_flags::writable);
-                return frame;
-              });
-      // NOLINTEND(cppcoreguidelines-avoid-magic-numbers)
-
-      if (!faux_pml4_frame)
-      {
-        system::panic("[MEM] Failed to map and construct faux PML4");
-      }
+      using namespace x86_64;
+      using entry_flags = page_table::entry::flags;
+
+      auto temporary_mapper = scoped_mapping{page::containing(unused_page_address), allocator};
+      auto new_pml4_frame = allocator.allocate();
 
-      // NOLINTNEXTLINE(cppcoreguidelines-avoid-magic-numbers)
-      pml4[510].frame(*faux_pml4_frame, entry_flags::present | entry_flags::writable);
-      x86_64::tlb_flush_all();
+      auto pml4 = std::construct_at(temporary_mapper.map_as<page_table>(*new_pml4_frame, entry_flags::writable));
+      (*pml4)[recursive_page_map_index].frame(new_pml4_frame.value(), entry_flags::present | entry_flags::writable);
+      paging_root::get()[recursive_page_map_index].frame(new_pml4_frame.value(),
+                                                         entry_flags::present | entry_flags::writable);
 
-      cio::println("[MEM] Injected faux PML4 as recursive map.");
+      tlb_flush_all();
     }
 
   }  // namespace
@@ -141,19 +97,8 @@ namespace teachos::memory
 
     auto allocator = create_early_frame_allocator();
     enable_cpu_protections();
-
-    // TODO: remove
     inject_faux_pml4(allocator);
 
-    // TODO: implement
-    auto temporary_mapper = x86_64::scoped_mapping{linear_address{unused_page_address}, allocator};
-    auto new_pml4_frame = allocator.allocate();
-
-    auto new_plm4 = temporary_mapper.map_as<x86_64::page_table>(
-        *new_pml4_frame, x86_64::page_table::entry::flags::present | x86_64::page_table::entry::flags::writable);
-    (*new_plm4)[510].frame(new_pml4_frame.value(),
-                           x86_64::page_table::entry::flags::present | x86_64::page_table::entry::flags::writable);
-
     // paging::kernel_mapper kernel(allocator, memory_information);
     // kernel.remap_kernel();
     // video::vga::text::write("Kernel remapping successful", video::vga::text::common_attributes::green_on_black);
diff --git a/arch/x86_64/src/memory/page_table.cpp b/arch/x86_64/src/memory/page_table.cpp
index 1273676..60bf94d 100644
--- a/arch/x86_64/src/memory/page_table.cpp
+++ b/arch/x86_64/src/memory/page_table.cpp
@@ -54,4 +54,10 @@ namespace teachos::memory::x86_64
     std::ranges::for_each(m_entries, &page_table::entry::clear);
   }
 
+  auto page_table::empty() const noexcept -> bool
+  {
+    return std::ranges::all_of(m_entries,
+                               [](auto const & entry) -> auto { return entry.all_flags() == entry::flags::empty; });
+  }
+
 }  // namespace teachos::memory::x86_64
diff --git a/arch/x86_64/src/memory/paging_root.cpp b/arch/x86_64/src/memory/paging_root.cpp
index 6b65f60..a29304e 100644
--- a/arch/x86_64/src/memory/paging_root.cpp
+++ b/arch/x86_64/src/memory/paging_root.cpp
@@ -40,13 +40,27 @@ namespace teachos::memory::x86_64
 
     auto handle_huge_page = [&] -> std::optional<frame> {
       auto pml3_entry = pml3.transform([&](auto pml3) -> auto { return (*pml3)[pml_index<3>(page)]; });
-      if (pml3_entry && pml3_entry->huge())
+      if (!pml3_entry)
+      {
+        return std::nullopt;
+      }
+      else if (pml3_entry->huge())
       {
         auto pml3_entry_frame = *pml3_entry->frame();
         return frame{pml3_entry_frame.number() + pml_index<2>(page) * entry_count + pml_index<1>(page)};
       }
 
-      // auto pml3_entry = (**pml3)[page.start_address().raw() >> 39 & 0x1ff];
+      auto pml2 = (*pml3)->next(pml_index<3>(page));
+      auto pml2_entry = pml2.transform([&](auto pml2) -> auto { return (*pml2)[pml_index<2>(page)]; });
+      if (!pml2_entry)
+      {
+        return std::nullopt;
+      }
+      else if (pml2_entry->huge())
+      {
+        auto pml2_entry_frame = *pml2_entry->frame();
+        return frame{pml2_entry_frame.number() + pml_index<1>(page)};
+      }
 
       return std::nullopt;
     };
diff --git a/arch/x86_64/src/memory/scoped_mapping.cpp b/arch/x86_64/src/memory/scoped_mapping.cpp
index 27c4785..602198e 100644
--- a/arch/x86_64/src/memory/scoped_mapping.cpp
+++ b/arch/x86_64/src/memory/scoped_mapping.cpp
@@ -4,25 +4,28 @@
 #include "kapi/system.hpp"
 
 #include "x86_64/memory/mmu.hpp"
+#include "x86_64/memory/page_table.hpp"
+#include "x86_64/memory/page_utilities.hpp"
 #include "x86_64/memory/paging_root.hpp"
 
+#include <memory>
 #include <utility>
 
 namespace teachos::memory::x86_64
 {
 
   scoped_mapping::scoped_mapping(scoped_mapping && other)
-      : m_address{std::exchange(other.m_address, linear_address{})}
+      : m_page{std::exchange(other.m_page, page{})}
       , m_allocator{std::exchange(other.m_allocator, nullptr)}
       , m_mapped{std::exchange(other.m_mapped, false)}
   {}
 
-  scoped_mapping::scoped_mapping(linear_address address, frame_allocator & allocator)
-      : m_address{address}
+  scoped_mapping::scoped_mapping(page page, frame_allocator & allocator)
+      : m_page{page}
       , m_allocator{&allocator}
       , m_mapped{false}
   {
-    if (paging_root::get().translate(address))
+    if (paging_root::get().translate(page))
     {
       system::panic("[MEM] Tried to map a page that is already mapped!");
     }
@@ -33,7 +36,7 @@ namespace teachos::memory::x86_64
     if (m_mapped)
     {
       unmap();
-      x86_64::tlb_flush(m_address);
+      x86_64::tlb_flush(m_page.start_address());
     }
   }
 
@@ -46,7 +49,7 @@ namespace teachos::memory::x86_64
 
     using std::swap;
 
-    swap(m_address, other.m_address);
+    swap(m_page, other.m_page);
     swap(m_allocator, other.m_allocator);
     swap(m_mapped, other.m_mapped);
 
@@ -55,12 +58,38 @@ namespace teachos::memory::x86_64
 
   auto scoped_mapping::map(frame frame, page_table::entry::flags flags) -> std::byte *
   {
-    static_cast<void>(frame);
-    static_cast<void>(flags);
+    auto & pml4 = paging_root::get();
+    auto pml4_index = pml_index<4>(m_page);
+    if (!pml4[pml4_index].present())
+    {
+      auto new_frame = m_allocator->allocate();
+      pml4[pml4_index].frame(*new_frame, page_table::entry::flags::present | flags);
+      std::construct_at(pml4.next(pml4_index).value());
+    }
 
-    m_mapped = true;
+    auto pml3 = pml4.next(pml4_index).value();
+    auto pml3_index = pml_index<3>(m_page);
+    if (!(*pml3)[pml3_index].present())
+    {
+      auto new_frame = m_allocator->allocate();
+      (*pml3)[pml3_index].frame(*new_frame, page_table::entry::flags::present | flags);
+      std::construct_at((*pml3).next(pml3_index).value());
+    }
 
-    return nullptr;
+    auto pml2 = (*pml3).next(pml3_index).value();
+    auto pml2_index = pml_index<2>(m_page);
+    if (!(*pml2)[pml2_index].present())
+    {
+      auto new_frame = m_allocator->allocate();
+      (*pml2)[pml2_index].frame(*new_frame, page_table::entry::flags::present | flags);
+      std::construct_at((*pml2).next(pml2_index).value());
+    }
+
+    auto pml1 = (*pml2).next(pml2_index).value();
+    auto pml1_index = pml_index<1>(m_page);
+    (*pml1)[pml1_index].frame(frame, page_table::entry::flags::present | flags);
+
+    return static_cast<std::byte *>(frame.start_address());
   }
 
   auto scoped_mapping::unmap() -> void
@@ -70,9 +99,31 @@ namespace teachos::memory::x86_64
       system::panic("[MEM] Tried to release an unmapped temporary mapping!");
     }
 
-    // TODO: scan pages
-    // TODO: remove mapping
-    // TODO: release temporary table frames
+    auto pml3 = paging_root::get().next(pml_index<4>(m_page)).value();
+    auto pml2 = pml3->next(pml_index<3>(m_page)).value();
+    auto pml1 = pml2->next(pml_index<2>(m_page)).value();
+
+    auto pml1_entry = (*pml1)[pml_index<1>(m_page)];
+    (*pml1)[pml_index<1>(m_page)].clear();
+    if (pml1->empty())
+    {
+      m_allocator->release(pml1_entry.frame().value());
+    }
+
+    auto pml2_entry = (*pml2)[pml_index<2>(m_page)];
+    (*pml2)[pml_index<2>(m_page)].clear();
+    if (pml2->empty())
+    {
+      m_allocator->release(pml2_entry.frame().value());
+    }
+
+    auto pml3_entry = (*pml3)[pml_index<3>(m_page)];
+    (*pml3)[pml_index<3>(m_page)].clear();
+    if (pml3->empty())
+    {
+      m_allocator->release(pml3_entry.frame().value());
+    }
+
     m_mapped = false;
   }