From 9c4b8fef9d150add335daf906f62214aaa06f149 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Thu, 13 Aug 2015 13:20:15 +0200
Subject: [PATCH] Add and load a 64-bit GDT

---
 src/arch/x86_64/boot.asm | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/arch/x86_64/boot.asm b/src/arch/x86_64/boot.asm
index 9c168bd5..3e3a6b93 100644
--- a/src/arch/x86_64/boot.asm
+++ b/src/arch/x86_64/boot.asm
@@ -26,6 +26,9 @@ start:
     call setup_page_tables
     call enable_paging
 
+    ; load the 64-bit GDT
+    lgdt [gdt64.pointer]
+
     ; print `OK` to screen
     mov dword [0xb8000], 0x2f4b2f4f
     hlt
@@ -126,3 +129,14 @@ p3_table:
 stack_bottom:
     resb 64
 stack_top:
+
+section .rodata
+gdt64:
+    dq 0 ; zero entry
+.code: equ $ - gdt64 ; new
+    dq (1<<44) | (1<<47) | (1<<41) | (1<<43) | (1<<53) ; code segment
+.data: equ $ - gdt64 ; new
+    dq (1<<44) | (1<<47) | (1<<41) ; data segment
+.pointer:
+    dw $ - gdt64 - 1
+    dq gdt64