From 8c0a1da9a81b6ef1c3b4edad09ffb99272cfbda1 Mon Sep 17 00:00:00 2001
From: Chloe M <chloe@mensia.org>
Date: Fri, 10 Jul 2026 21:10:30 -0400
Subject: [PATCH] ptos/amd64: Add global descriptor table defs

Signed-off-by: Chloe M <chloe@mensia.org>
---
 service/ptos/head/arch/amd64/gdt.h | 40 ++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 service/ptos/head/arch/amd64/gdt.h

diff --git a/service/ptos/head/arch/amd64/gdt.h b/service/ptos/head/arch/amd64/gdt.h
new file mode 100644
index 0000000..325c505
--- /dev/null
+++ b/service/ptos/head/arch/amd64/gdt.h
@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Global descriptor table
+ * Author:      Chloe M.
+ */
+
+#ifndef _MACHINE_GDT_H_
+#define _MACHINE_GDT_H_ 1
+
+#include <ptdef.h>
+
+/* Number of GDT entries */
+#define GDT_ENTRY_COUNT 7
+
+/* Kernel code/data */
+#define GDT_KCODE  0x08
+#define GDT_KDATA  0x10
+
+/* User code/data */
+#define GDT_UCODE  0x18
+#define GDT_UDATA  0x20
+
+/* Task state segment */
+#define GDT_TSS    0x28
+#define GDT_TSS_INDEX 0x05
+
+/*
+ * Global descriptor table entry
+ */
+typedef struct PACKED {
+    USHORT Limit;
+    USHORT BaseLow;
+    UCHAR BaseMid;
+    USHORT Attributes;
+    UCHAR BaseHigh;
+} GDT_ENTRY;
+
+#endif  /* !_MACHINE_GDT_H_ */