From 22e5f89bb1a88e22d86347f5ac32d6336169ca55 Mon Sep 17 00:00:00 2001
From: Nocturn9x <hackhab@gmail.com>
Date: Fri, 18 Nov 2022 01:39:08 +0100
Subject: [PATCH] Added experimental code to enable A20 line

---
 src/boot/switch32.s | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/boot/switch32.s b/src/boot/switch32.s
index 7fa64ce..b4338ab 100644
--- a/src/boot/switch32.s
+++ b/src/boot/switch32.s
@@ -16,12 +16,20 @@
 
 [bits 16]
 switch_to_protected_mode:
-    cli ; We disable interrupts...
-    lgdt [gdt_descriptor] ; ... load the GDT descriptor...
+    ; We enable the A20 line using
+    ; the ol' but (mostly) reliable
+    ; keyboard controller method
+    mov al, 0xd1
+    out 0x64, al
+    mov al, 0xdf
+    out 0x60, al
+    cli ; Now we disable interrupts
+    lgdt [gdt_descriptor] ; Time to load the GDT descriptor
+    ; We set 32-bit mode in CR0. Almost done!
     mov eax, cr0
-    or eax, 0x1 ; ... set 32-bit mode in CR0
+    or eax, 0x1
     mov cr0, eax
-    jmp CODE_SEG:switch32 ; ... and perform a far jump using a different segment
+    jmp CODE_SEG:switch32 ; At last, we perform a far jump into a different segment
 
 
 [bits 32]