Kernel loads now, bootloader works kind of

4 files changed, 78 insertions, 152 deletions

diff --git a/src/boot/boot.stage1.asm b/src/boot/boot.stage1.asm
index a67e7fa..6bed463 100644
--- a/src/boot/boot.stage1.asm
+++ b/src/boot/boot.stage1.asm
@@ -30,6 +30,7 @@ _start:
     int 0x13                    ; Read disk 
     jc _disk_read_err
 
+    mov dl, [drive]
     jmp 0x0000:STAGE2_ADDR
     
 
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
diff --git a/src/boot/boot.stage2.asm b/src/boot/boot.stage2.asm
index 52c73e5..968bedc 100644
--- a/src/boot/boot.stage2.asm
+++ b/src/boot/boot.stage2.asm
@@ -3,6 +3,8 @@
     [bits 16]
     [org 0x7e00]
     
+    %include "common.asm"
+
     jmp 0x0000:_s2_entry
 
 _s2_entry:  
@@ -10,6 +12,19 @@ _s2_entry:
     xor ax, ax
     mov ds, ax
 
+    mov si, DAP_kernel
+    mov ah, 0x42
+    int 0x13
+    jc _kernel_load_err
+    jmp _kernel_loaded
+
+_kernel_load_err:   
+    mov si, boot_kernel_err
+    call _print_string
+
+    jmp $
+
+_kernel_loaded: 
     mov si, boot_s2_msg
     call _print_string
 
@@ -27,21 +42,34 @@ _s2_entry:
 _protected_mode:    
     mov ax, DATA_SEG32
     mov ds, ax
+    mov ss, ax
     mov esp, 0x90000
+    and esp, 0xFFFFFFF0         ; Align to 16-byte boundary
 
     mov esi, boot_protmode_msg
     call _print_string_pm_vga 
 
     call 0x10000
-
-    jmp $
     
+boot_s2_msg:    
+    db "Entering Stage 2", 13, 10, 0
+boot_protmode_msg:  
+    db "Enabling Protected Mode", 13, 10, 0
+boot_kernel_err:    
+    db "Error loading kernel from disk", 13, 10, 0
+
+
+    align 16
+DAP_kernel: 
+    db 0x10
+    db 0
+    dw 1                         ; Number of sectors
+    dw 0x0000   
+    dw 0x1000                    ; Offset
+    dq 66                        ; Starting sector
+
     %include "boot.stage1.print.asm"
     %include "boot.stage2.a20.asm"
     %include "boot.stage2.gdt32.asm"
     %include "boot.stage2.print.asm"
 
-boot_s2_msg:    
-    db "Entering Stage 2", 13, 10, 0
-boot_protmode_msg:  
-    db "Enabling Protected Mode", 13, 10, 0
diff --git a/src/boot/boot.stage2.print.asm b/src/boot/boot.stage2.print.asm
index d567d6d..4527b87 100644
--- a/src/boot/boot.stage2.print.asm
+++ b/src/boot/boot.stage2.print.asm
@@ -1,39 +1,37 @@
     ;; boot.stage2.print.asm
-
-    section .stage2
     
     %define VGA_BUFFER 0xb8000
     %define WB_COLOR 0xf
 
 
 _print_string_pm_vga:   
-    mov eax, [esi]
-    lea esi, [esi+1]
-    cmp al, 0   
-    jne .print_char_pm_vga
-    add byte [pos_x], 0
-    add byte [pos_y], 1
-    ret
+    pusha
+    mov edi, VGA_BUFFER
+    mov ah, WB_COLOR
+    xor ecx, ecx
+    xor edx, edx
 
-    .print_char_pm_vga:
-    mov ah, WB_COLOR               ; White on black
-    mov ecx, eax
-    movzx eax, byte [pos_y]
-    mov edx, 160
-    mul edx
-    movzx ebx, byte [pos_x]
-    shl ebx, 1
-    
-    mov edi, VGA_BUFFER         ; Video memory start
-    add edi, ebx                ; Add X offset
-    add edi, eax                ; Add Y offset
-    
-    mov eax, ecx                ; Restore char
-    mov word [ds:edi], ax
-    add byte [pos_x], 1         ; Advance to right  
-    ret
+    .print_loop:
+    lodsb
+    test al, al
+    jz .done
 
-pos_x:  db 0
-pos_y:  db 0
+    push eax
+    mov eax, edx
+    imul eax, eax, 160
+    lea edi, [VGA_BUFFER + eax]
+    lea edi, [edi + ecx * 2]
+    pop eax
     
+    ;; Advance cursor
+    inc cl
+    cmp cl, 80
+    jb .print_loop
+    xor cl, cl
+    inc dl
+
+    jmp .print_loop
     
+    .done:
+    popa
+    ret