From e40da55691ad2c36b349ace7cd368394976a1d6d Mon Sep 17 00:00:00 2001
From: Aqua-sama <aqua@iserlohn-fortress.net>
Date: Sat, 6 Mar 2021 16:01:29 +0200
Subject: GDT: flush segment registers on lgdt

---
 src/gdt.h | 41 +++++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 20 deletions(-)

(limited to 'src/gdt.h')

diff --git a/src/gdt.h b/src/gdt.h
index bb7181b..6aeaa33 100644
--- a/src/gdt.h
+++ b/src/gdt.h
@@ -27,11 +27,6 @@
 
 class GDT {
 public:
-  GDT();
-  ~GDT() = default;
-
-  uint16_t codeDescriptor() const;
-
   struct Pointer {
     uint16_t limit;
     uint32_t base;
@@ -41,18 +36,24 @@ public:
   public:
     enum Ring : unsigned int { Ring0 = 0x0, Ring1 = 0x1, Ring2 = 0x2, Ring3 = 0x3 };
     struct Access {
-      bool accessed : 1 = false;              // if 0, is set by processor when accessed
-      bool r_w : 1 = false;                   // on code segment: read toggle
-                                              // on data segment: write toggle
-      bool direction_conforming : 1 = false;  // TODO
-      bool exe : 1 = false;                   // true for code segment, false for data segment
-      bool segment : 1 = false;               // segment bit: 1 for code/data segments
-                                              //              0 for gates and tss
-      Ring privilege : 2 = Ring0;             // descriptor privilege level
-      bool present : 1 = true;                // must be 1 for every active segment
+      bool accessed : 1 = false;   // if 0, is set by processor when accessed
+      bool r_w : 1 = false;        // on code segment: read toggle
+                                   // on data segment: write toggle
+      bool direction : 1 = false;  // TODO
+      bool exe : 1 = false;        // true for code segment, false for data segment
+      bool segment : 1 = false;    // segment bit: 1 for code/data segments
+                                   //              0 for gates and tss
+      Ring privilege : 2 = Ring0;  // descriptor privilege level
+      bool present : 1 = false;    // must be 1 for every active segment
+
+      constexpr operator uint8_t() const {
+        return static_cast<uint8_t>(accessed) | static_cast<uint8_t>(r_w << 1) | static_cast<uint8_t>(direction << 2) |
+               static_cast<uint8_t>(exe << 3) | static_cast<uint8_t>(segment << 4) |
+               static_cast<uint8_t>(privilege << 5) | static_cast<uint8_t>(present << 7);
+      }
     } __attribute__((packed));
 
-    SegmentDescriptor() { access.present = false; };
+    constexpr SegmentDescriptor() { access.present = false; };
 
     template <uint32_t limit>
     static SegmentDescriptor make(uint32_t base, Access type) {
@@ -94,11 +95,11 @@ public:
 
     unsigned int base_31_24 : 8 = 0;   // high bits of segment address
   } __attribute__((packed));
+  enum SegmentMap { null0, kcode, kdata };
+
+  GDT();
+  ~GDT() = default;
 
-private:
-  SegmentDescriptor segments[256];
+  uint16_t descriptor(SegmentMap) const;
 };
 
-static_assert(sizeof(GDT::Pointer) == 6);
-static_assert(sizeof(GDT::SegmentDescriptor) == 8);
-static_assert(sizeof(GDT::SegmentDescriptor::Access) == 1);
-- 
cgit v1.2.1