Added disk manager and fixed bug with _format(changed call to je)

Author: Retr0-code

boot.asm

@@ -36,16 +36,54 @@ section .text:
         pop ax                      ; Recover AX value from stack
         pop bx                      ; Recover BX value from stack
         
+        mov [disk_index], dl
+        mov bx, kernel_address
+        mov dh, 2
+        call _read_disk
 
         jmp $                       ; Stops the processor
 
 
 ; Data Section
 %include "functions/io.asm"
+%include "functions/disk_mng.asm"
 
         msg: db "Hello, There!\nPlease enter your message: ", 0x0 ; Printable string
     
         buffer: times 4 db 0        ; Defines input buffer
 
-        times 510-($-$$) db 0       ; Fills binary with 0 to keep the offset of 512
-        dw 0xAA55                   ; Magic Word
+        kernel_address: equ 0x1000
+        disk_index: db 0
+
+ Global Descriptor Table
+GDT_start:
+    GDT_null:
+        dd 0x0
+        dd 0x0
+
+    GDT_code:
+        dw 0xffff
+        dw 0x0
+        db 0x0
+        db 0b10011010
+        db 0b11001111
+        db 0x0
+
+    GDT_data:
+        dw 0xffff
+        dw 0x0
+        db 0x0
+        db 0b10010010
+        db 0b11001111
+        db 0x0
+
+        GDT_end:
+
+    GDT_descriptor:
+        dw GDT_end - GDT_start - 1
+        dd GDT_start
+
+    times 510-($-$$) db 0       ; Fills binary with 0 to keep the offset of 512
+    dw 0xAA55                   ; Magic Word
+    times 512 db 'A' ; sector 2 = 512 bytes
+    times 512 db 'B' ; sector 3 = 512 bytes

functions/disk_mng.asm

@@ -0,0 +1,33 @@
+global _read_disk
+
+section .text:
+    _read_disk:
+        pusha
+        push dx
+
+        mov ah, 0x02
+        mov al, dh
+        mov cl, 0x02
+        mov ch, 0x00
+        mov dh, 0x00
+
+        int 0x13
+        jc disk_error
+
+        pop dx
+        cmp al, dh
+        jne sectors_error
+        popa
+        ret
+
+
+    disk_error:
+        push DISK_ERROR
+        call _printformat
+
+    sectors_error:
+        push SECTORS_ERROR
+        call _printformat
+
+    DISK_ERROR: db "Disk read error", 0
+    SECTORS_ERROR: db "Incorrect number of sectors read", 0

functions/printf.asm

@@ -46,7 +46,9 @@ section .text:
         mov al, [bx]                ; Moves addresses value to AL
         
         cmp al, 0x6e                ; If character is 'n'
-        call _newline               ; Call new line
+        je _newline                 ; Call new line
+        cmp al, 0x30                ; If character is '0'
+        je _done_printf             ; Exits if was \0
         
         inc bx                      ; Incriment BX
         jmp _print_next_char        ; Jump to next char

run.sh

@@ -1,4 +1,4 @@
 #!/bin/bash
 
 nasm -f bin -o boot.bin boot.asm
-qemu-system-x86_64 boot.bin
+qemu-system-x86_64 -fda boot.bin