From f186a44f826d17786b464b2fcdc7b88b3c55876a Mon Sep 17 00:00:00 2001
From: John Hodge <tpg@mutabah.net>
Date: Thu, 27 May 2010 20:10:53 +0800
Subject: [PATCH] x86_64 starts without erroring, reaches high mem and full
 64-bit

---
 Kernel/Makefile.BuildNum       |  2 +-
 Kernel/arch/x86_64/start32.asm | 11 ++++-------
 Kernel/arch/x86_64/start64.asm | 25 ++++++++++++++++++++++++-
 3 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/Kernel/Makefile.BuildNum b/Kernel/Makefile.BuildNum
index 2e18d025..165c6a4b 100644
--- a/Kernel/Makefile.BuildNum
+++ b/Kernel/Makefile.BuildNum
@@ -1 +1 @@
-BUILD_NUM = 2206
+BUILD_NUM = 2212
diff --git a/Kernel/arch/x86_64/start32.asm b/Kernel/arch/x86_64/start32.asm
index 21e7c408..6f3c9a77 100644
--- a/Kernel/arch/x86_64/start32.asm
+++ b/Kernel/arch/x86_64/start32.asm
@@ -33,8 +33,12 @@ mboot:
 [global start]
 start:
 	; Check for Long Mode support
+	mov eax, 0x80000000
+	cpuid
+	cmp eax, 0x80000001	; Compare the A-register with 0x80000001.
 	mov eax, 0x80000001
 	cpuid
+    jb .not64bitCapable
 	test edx, 1<<29
 	jz .not64bitCapable
 
@@ -60,13 +64,6 @@ start:
 
 	; Load GDT
 	lgdt [gGDTPtr - KERNEL_BASE]
-	mov ax, 0x10
-	mov ss, ax
-	mov ds, ax
-	mov es, ax
-	mov fs, ax
-	mov gs, ax
-
 	jmp 0x08:start64 - KERNEL_BASE
 
 .not64bitCapable:
diff --git a/Kernel/arch/x86_64/start64.asm b/Kernel/arch/x86_64/start64.asm
index a2ffb19b..699c7931 100644
--- a/Kernel/arch/x86_64/start64.asm
+++ b/Kernel/arch/x86_64/start64.asm
@@ -6,9 +6,32 @@
 [section .text]
 [global start64]
 start64:
+	; Load Registers
+	mov ax, 0x10
+	mov ds, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	
+	; Go to high memory
+	mov rax, start64.himem
+	jmp rax
+.himem:
+	
+	; Clear the screen
+	mov rax, 0x1F201F201F201F20	; Set the screen to White on blue, space (4 characters)
+	mov edi, 0xB8000
+	mov ecx, 80*25*2/8
+	rep stosq
+	
 	; Set kernel stack
+	mov rsp, gInitialKernelStack
+	
 	; Call main
-	jmp $
+	cli
+.hlt:
+	hlt
+	jmp .hlt
 
 [global GetRIP]
 GetRIP:
-- 
2.20.1