Adjust register segment descriptors to possible states

3 files changed, 43 insertions, 8 deletions

diff --git a/arch/x86_64/src/context_switching/descriptor_table/access_byte.cpp b/arch/x86_64/src/context_switching/descriptor_table/access_byte.cpp
index 15a0947..7a2b0b0 100644
--- a/arch/x86_64/src/context_switching/descriptor_table/access_byte.cpp
+++ b/arch/x86_64/src/context_switching/descriptor_table/access_byte.cpp
@@ -1,14 +1,15 @@
 #include "arch/context_switching/descriptor_table/access_byte.hpp"
 
-#include <bitset>
-
 namespace teachos::arch::context_switching::descriptor_table
 {
-  auto access_byte::contains_flags(std::bitset<8U> other) const -> bool { return (flags & other) == other; }
-
-  auto access_byte::get_privilege_level() const -> privilege_level
+  access_byte::access_byte(uint8_t flags)
+      : _flags(flags)
+      , _type(flags)
   {
-    constexpr uint8_t PRIVILEGE_MASK = 0b0110'0000;
-    return static_cast<privilege_level>(flags.to_ulong() & PRIVILEGE_MASK);
+    // Nothing to do.
   }
+
+  auto access_byte::contains_flags(std::bitset<4U> other) const -> bool { return (_flags & other) == other; }
+
+  auto access_byte::get_type_field() const -> type_field { return _type; }
 }  // namespace teachos::arch::context_switching::descriptor_table
diff --git a/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp b/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp
index 8a05956..8e1e939 100644
--- a/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp
+++ b/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp
@@ -1,6 +1,28 @@
 #include "arch/context_switching/descriptor_table/gdt_flags.hpp"
 
+#include "arch/exception_handling/assert.hpp"
+
 namespace teachos::arch::context_switching::descriptor_table
 {
-  auto gdt_flags::contains_flags(std::bitset<4U> other) const -> bool { return (flags & other) == other; }
+  gdt_flags::gdt_flags(uint8_t flags, segment_descriptor_type type)
+      : _flags(flags << 5U)
+  {
+    switch (type)
+    {
+      case segment_descriptor_type::SYSTEM_SEGMENT:
+        _flags.set(2, false);
+        _flags.set(3, false);
+        break;
+      case segment_descriptor_type::DATA_SEGMENT:
+        _flags.set(3, false);
+        break;
+      case segment_descriptor_type::CODE_SEGMENT:
+        exception_handling::assert((contains_flags(LENGTH) && !contains_flags(DEFAULT_LENGTH)) ||
+                                       !contains_flags(LENGTH),
+                                   "[GDT] Flags of code segment descriptor has both ");
+        break;
+    }
+  }
+
+  auto gdt_flags::contains_flags(std::bitset<4U> other) const -> bool { return (_flags & other) == other; }
 }  // namespace teachos::arch::context_switching::descriptor_table
diff --git a/arch/x86_64/src/context_switching/descriptor_table/type_field.cpp b/arch/x86_64/src/context_switching/descriptor_table/type_field.cpp
new file mode 100644
index 0000000..d967a97
--- /dev/null
+++ b/arch/x86_64/src/context_switching/descriptor_table/type_field.cpp
@@ -0,0 +1,12 @@
+#include "arch/context_switching/descriptor_table/type_field.hpp"
+
+namespace teachos::arch::context_switching::descriptor_table
+{
+  type_field::type_field(uint8_t flags)
+      : _flags(flags)
+  {
+    // Nothing to do.
+  }
+
+  auto type_field::contains_flags(std::bitset<4U> other) const -> bool { return (_flags & other) == other; }
+}  // namespace teachos::arch::context_switching::descriptor_table