From 415d27814f40d10f5125c621913e23e751a1e261 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Tue, 11 Apr 2017 14:59:09 +0200
Subject: [PATCH] Do a far jump to long mode and print `OKAY`

---
 src/arch/x86_64/boot.asm           | 4 ++++
 src/arch/x86_64/long_mode_init.asm | 9 +++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 src/arch/x86_64/long_mode_init.asm

diff --git a/src/arch/x86_64/boot.asm b/src/arch/x86_64/boot.asm
index 98155c2..fcd2422 100644
--- a/src/arch/x86_64/boot.asm
+++ b/src/arch/x86_64/boot.asm
@@ -1,4 +1,5 @@
 global start
+extern long_mode_start
 
 section .text
 bits 32
@@ -15,6 +16,8 @@ start:
     ; load the 64-bit GDT
     lgdt [gdt64.pointer]
 
+    jmp gdt64.code:long_mode_start
+
     ; print `OK` to screen
     mov dword [0xb8000], 0x2f4b2f4f
     hlt
@@ -154,6 +157,7 @@ stack_top:
 section .rodata
 gdt64:
     dq 0 ; zero entry
+.code: equ $ - gdt64 ; new
     dq (1<<43) | (1<<44) | (1<<47) | (1<<53) ; code segment
 .pointer:
     dw $ - gdt64 - 1
diff --git a/src/arch/x86_64/long_mode_init.asm b/src/arch/x86_64/long_mode_init.asm
new file mode 100644
index 0000000..507f389
--- /dev/null
+++ b/src/arch/x86_64/long_mode_init.asm
@@ -0,0 +1,9 @@
+global long_mode_start
+
+section .text
+bits 64
+long_mode_start:
+    ; print `OKAY` to screen
+    mov rax, 0x2f592f412f4b2f4f
+    mov qword [0xb8000], rax
+    hlt