x86_64/memory: only deallocate allocated frames

2 files changed, 28 insertions, 12 deletions

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 dff54ec..99585bc 100644
--- a/arch/x86_64/include/x86_64/memory/scoped_mapping.hpp
+++ b/arch/x86_64/include/x86_64/memory/scoped_mapping.hpp
@@ -57,6 +57,7 @@ namespace teachos::memory::x86_64
     page m_page;
     frame_allocator * m_allocator;
     bool m_mapped;
+    std::uint8_t m_allocated;
   };
 
 }  // namespace teachos::memory::x86_64
diff --git a/arch/x86_64/src/memory/scoped_mapping.cpp b/arch/x86_64/src/memory/scoped_mapping.cpp
index 6e2328d..be15330 100644
--- a/arch/x86_64/src/memory/scoped_mapping.cpp
+++ b/arch/x86_64/src/memory/scoped_mapping.cpp
@@ -18,12 +18,14 @@ namespace teachos::memory::x86_64
       : m_page{std::exchange(other.m_page, page{})}
       , m_allocator{std::exchange(other.m_allocator, nullptr)}
       , m_mapped{std::exchange(other.m_mapped, false)}
+      , m_allocated{std::exchange(other.m_allocated, 0)}
   {}
 
   scoped_mapping::scoped_mapping(page page, frame_allocator & allocator)
       : m_page{page}
       , m_allocator{&allocator}
       , m_mapped{false}
+      , m_allocated{}
   {
     if (paging_root::get().translate(page))
     {
@@ -52,6 +54,7 @@ namespace teachos::memory::x86_64
     swap(m_page, other.m_page);
     swap(m_allocator, other.m_allocator);
     swap(m_mapped, other.m_mapped);
+    swap(m_allocated, other.m_allocated);
 
     return *this;
   }
@@ -65,6 +68,7 @@ namespace teachos::memory::x86_64
       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_allocated |= 1uz << 2;
     }
 
     auto pml3 = pml4.next(pml4_index).value();
@@ -74,6 +78,7 @@ namespace teachos::memory::x86_64
       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());
+      m_allocated |= 1uz << 1;
     }
 
     auto pml2 = (*pml3).next(pml3_index).value();
@@ -83,6 +88,7 @@ namespace teachos::memory::x86_64
       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());
+      m_allocated |= 1uz << 0;
     }
 
     auto pml1 = (*pml2).next(pml2_index).value();
@@ -105,25 +111,34 @@ namespace teachos::memory::x86_64
     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())
+    if (m_allocated & 1uz << 0)
     {
-      m_allocator->release(pml1_entry.frame().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())
+    if (m_allocated & 1uz << 1)
     {
-      m_allocator->release(pml2_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())
+    if (m_allocated & 1uz << 2)
     {
-      m_allocator->release(pml3_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;