Added strcmp function

kernel.asm

@@ -1,20 +1,34 @@
-sect2:
   mov ax, 2000h
   mov ds, ax
 
-  mov si, msg
+  push msg
   call print
 
-  mov si, msg2
+  push msg2
   call print
 
+  push 13
+  push msg
+  push msg
+  call strcmp
+
+  cmp ax, 1
+  jne _ne
+  push msg_same
+  call print
+_ne:
+
   jmp $
 
+data:
   msg db "Kernel OK!", 13, 10, 0
   msg2 db "Hello, World!", 13, 10, 0
+  msg_same db "They are the same", 13, 10, 0
 
 print:
-  pop si
+  push bp
+  mov bp, sp
+  mov si, [bp + 4]
   mov ah, 0eh
   mov cx, 1
   mov bh, 0
@@ -25,4 +39,32 @@ print_loop:
   int 10h
   jmp print_loop
 print_exit:
+  pop bp
   ret
+
+strcmp:
+  push bp
+  mov bp, sp
+  mov ax, [bp + 4]
+  lea si, [bp+6]
+  lea di, [bp+8]
+  dec di
+  mov word [bp - 2], 0
+strcmp_loop:
+  inc di
+  inc word [bp - 2]
+  lodsb
+  cmp [di], al
+  jne strcmp_notequal
+  cmp [bp - 2], ax
+  jne strcmp_equal
+
+
+strcmp_equal:
+  mov ax, 1
+  pop bp
+  ret
+strcmp_notequal:
+  mov ax, 0
+  pop bp
+  ret