From 936e2073a92ec1ca49543b932444cdacd7fbe8fc Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Tue, 11 Apr 2017 14:55:41 +0200
Subject: [PATCH] Enable paging

---
 src/arch/x86_64/boot.asm | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/arch/x86_64/boot.asm b/src/arch/x86_64/boot.asm
index 71703ee..3e8e594 100644
--- a/src/arch/x86_64/boot.asm
+++ b/src/arch/x86_64/boot.asm
@@ -10,6 +10,7 @@ start:
     call check_long_mode
 
     call set_up_page_tables
+    call enable_paging
 
     ; print `OK` to screen
     mov dword [0xb8000], 0x2f4b2f4f
@@ -103,6 +104,29 @@ set_up_page_tables:
 
     ret
 
+enable_paging:
+    ; load P4 to cr3 register (cpu uses this to access the P4 table)
+    mov eax, p4_table
+    mov cr3, eax
+
+    ; enable PAE-flag in cr4 (Physical Address Extension)
+    mov eax, cr4
+    or eax, 1 << 5
+    mov cr4, eax
+
+    ; set the long mode bit in the EFER MSR (model specific register)
+    mov ecx, 0xC0000080
+    rdmsr
+    or eax, 1 << 8
+    wrmsr
+
+    ; enable paging in the cr0 register
+    mov eax, cr0
+    or eax, 1 << 31
+    mov cr0, eax
+
+    ret
+
 ; Prints `ERR: ` and the given error code to screen and hangs.
 ; parameter: error code (in ascii) in al
 error: