Fix segment descriptor bit order of private members

2 files changed, 18 insertions, 11 deletions

diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp
index b5697e3..06e2e8a 100644
--- a/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp
+++ b/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp
@@ -51,11 +51,14 @@ namespace teachos::arch::context_switching::descriptor_table
     auto get_segment_type() const -> segment_descriptor_type;
 
   private:
-    uint32_t _reserved = {};
-    access_byte _access = {};
-    gdt_flags _flag = {};
-    uint64_t _base = {};
-    std::bitset<20U> _limit = {};
+    // The order in private variables starts for the first variable being the rightmost bit.
+    std::bitset<16U> _limit_1 = {};  ///< First part of the limit field (0 - 15)
+    std::bitset<24U> _base_1 = {};   ///< First part of the base field (16 - 39)
+    access_byte _access = {};        ///< Access byte field (40 - 47)
+    std::bitset<4U> _limit_2 = {};   ///< Second part of the limit field (48 - 51)
+    gdt_flags _flag = {};            ///< Flags field (52 - 55)
+    std::bitset<40U> _base_2 = {};   ///< Second part of the base field (56 - 95)
+    uint32_t _reserved = {};         ///< Reserved field used to ensure this struct is 128 bits big (96 - 127)
   };
 }  // namespace teachos::arch::context_switching::descriptor_table
 
diff --git a/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp b/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp
index ab8eaba..a743ad2 100644
--- a/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp
+++ b/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp
@@ -3,22 +3,26 @@
 namespace teachos::arch::context_switching::descriptor_table
 {
   segment_descriptor::segment_descriptor(uint128_t flags)
-      : _reserved(flags >> 96U)
+      : _limit_1(flags << 112U)
+      , _base_1((flags >> 16U) << 88U)
       , _access((flags >> 44U) << 80U, (flags >> 40U) << 84U)
+      , _limit_2((flags >> 48U) << 72U)
       , _flag((flags >> 52U) << 72U)
-      , _base(((flags >> 64U) << 32U) << 32U | ((flags >> 56U) << 64U) << 24U | (flags >> 16U) << 88U)
-      , _limit(((flags >> 48U) << 72U) << 16U | flags << 112U)
+      , _base_2((flags >> 56U) << 32U)
+      , _reserved(flags >> 96U)
   {
     // Nothing to do.
   }
 
   segment_descriptor::segment_descriptor(access_byte access_byte, gdt_flags flags, uint64_t base,
                                          std::bitset<20U> limit)
-      : _reserved(0U)
+      : _limit_1((limit.to_ulong() << 4U) >> 16U)
+      , _base_1((base << 40U) >> 40U)
       , _access(access_byte)
+      , _limit_2(limit.to_ulong() >> 16U)
       , _flag(flags)
-      , _base(base)
-      , _limit(limit)
+      , _base_2(base >> 24U)
+      , _reserved(0U)
   {
     // Nothing to do
   }