Handout

kernel/arch/gdt.cc

@@ -0,0 +1,36 @@
+#include "gdt.h"
+
+#include "core.h"
+
+namespace GDT {
+
+// The static 32-bit Global Descriptor Table (GDT)
+alignas(16) constinit SegmentDescriptor protected_mode[] = {
+	// Null descriptor
+	{},
+
+	// Global code segment von 0-4GB
+	SegmentDescriptor::Segment(0, UINT32_MAX, true, 0, Size::Bit32),
+
+	// Global data segment von 0-4GB
+	SegmentDescriptor::Segment(0, UINT32_MAX, false, 0, Size::Bit32),
+};
+extern "C" constexpr Pointer gdt_protected_mode_pointer(protected_mode);
+
+// The static 64-bit Global Descriptor Table (GDT)
+// \see [ISDMv3 3.2.4 Segmentation in IA-32e
+// Mode](intel_manual_vol3.pdf#page=91)
+alignas(16) constinit SegmentDescriptor long_mode[] = {
+	// Null descriptor
+	SegmentDescriptor::Null(),
+
+	// Global code segment
+	SegmentDescriptor::Segment64(true, 0),
+
+	// Global data segment
+	SegmentDescriptor::Segment64(false, 0),
+
+};
+extern "C" constexpr Pointer gdt_long_mode_pointer(long_mode);
+
+}  // namespace GDT