From f81dee10ef19f0c82eb89d0e528bcbfb7a38b016 Mon Sep 17 00:00:00 2001
From: kotorifan <kotorifan05@gmail.com>
Date: Sat, 7 Mar 2026 17:14:14 +0100
Subject: Kernel loads now, bootloader works kind of

---
 src/boot/boot.stage2.a20.asm | 135 ++++++-------------------------------------
 1 file changed, 17 insertions(+), 118 deletions(-)

(limited to 'src/boot/boot.stage2.a20.asm')

diff --git a/src/boot/boot.stage2.a20.asm b/src/boot/boot.stage2.a20.asm
index 3c69d79..d0b52c4 100644
--- a/src/boot/boot.stage2.a20.asm
+++ b/src/boot/boot.stage2.a20.asm
@@ -1,147 +1,46 @@
-    ;;  boot.stage2.a20.asm
-    section .stage2
+    ;; boot.stage2.a20.asm
 _enable_a20:    
-    call _check_a20
-    test ax, ax
-    jnz .end
+    cli
 
-    call _enable_a20_bios
-    call _check_a20
-    test ax, ax
-    jnz .end
-    
-    call _enable_a20_keyb
-    call _check_a20
-    test ax, ax
-    jnz .end
-
-    call _enable_a20_io92
-    call _check_a20
-    test ax, ax
-    jnz .end
-
-    .halt: hlt
-    jmp .halt
-    .end:
-    ret
-
-_check_a20:     
-    pushf
-    push ds
-    push es
-    push di
-    push si
-    cli                         ; Clear Interrupts
-    
-    xor ax, ax
-    mov es, ax
-    not ax
-    mov ds, ax
-    ;; 0500 and 0510 are guaranteed to be free
-    mov di, 0x0500
-    mov si, 0x0510
-    
-    ;; Save the original values
-    mov dl, byte [es:di]
-    push dx
-    mov dl, byte [ds:si]
-    push dx
-
-    mov byte [es:di], 0x00
-    mov byte [ds:si], 0xFF
-    cmp byte [es:di], 0xFF
-
-    mov ax, 0                   ; The A20 is disabled
-    je .a20_disabled
-    mov ax, 1                   ; The A20 is enabled
-    .a20_disabled:
-    pop dx
-    mov byte [ds:si], dl
-    pop dx
-    mov byte [es:di], dl
-    
-    pop si
-    pop di
-    pop es
-    pop ds
-    popf
-    sti                         ; Enable interrupts again
-    ret
-
-_enable_a20_bios:   
-    mov ax, 0x2401
-    int 0x15
-    jc .fast_gate
-    test ah, ah
-    jnz .failed
-    call _check_a20
-    test ax, ax
-    jnz .done
-    
-    .fast_gate:
-    in al, 0x92
-    test al, 2
-    jnz .done
-    
-    or al, 2
-    and al, 0xfe
-    out 0x92, al
-   
-    call _check_a20
-    test ax, ax
-    jnz .done
-
-    .done:
-    mov ax, 1
-    ret
-
-    .failed:
-    mov ax, 0
-    ret
-
-_enable_a20_keyb:   
-    cli 
+    ;; Disable keyboard
     call .wait_io1
     mov al, 0xad
     out 0x64, al
 
+    ;; Read from keyboard controller
     call .wait_io1
-    mov al, 0x0d0
+    mov al, 0xd0
     out 0x64, al
 
     call .wait_io2
     in al, 0x60
-    push eax
+    push eax ; Save current value
 
+
+    ;; Write back with the A20 bit set
     call .wait_io1
     mov al, 0xd1
     out 0x64, al
 
+    call .wait_io1
+    pop eax
+    or al, 2 ; Set A20 bit
+
+    ;; Enable keyboard
     call .wait_io1
     mov al, 0xae
     out 0x64, al
-    
-    sti 
-    ret
 
+    call .wait_io1
+    
     .wait_io1:
     in al, 0x64
     test al, 2
     jnz .wait_io1
     ret
-    
-    .wait_io2:  
+
+    .wait_io2:
     in al, 0x64
     test al, 1
     jz .wait_io2
     ret
-
-_enable_a20_io92:   
-    in al, 0x92                 ; Read from port 0x92
-    test al, 2                  ; Check if bit 1
-    jnz .end
-    or al, 2
-    and al, 0xfe
-    out 0x92, al
-    .end:
-    ret
-- 
cgit v1.3