Basic BIOS-based print function

boot16.S

@@ -1,14 +1,39 @@
             // vim: et:sw=12:ts=12:sts=12
 
-            .code16
             .global     _start
             .text
+            .code16
 
 _start:
-            xor         %bx, %bx
-            mov         $0x0E, %ah
-            mov         $'A', %al
-            int         $0x10
+            mov         %cs, %ax
+            mov         %ax, %ds
+
+            push        $message
+            call        print
+            add         $2, %sp
 
 1:          hlt
             jmp         1b
+            
+print:      push        %bp
+            mov         %sp, %bp
+            push        %bx
+            push        %si
+
+            xor         %bx, %bx
+            mov         4(%bp), %si
+
+1:          lodsb
+            or          %al, %al
+            jz          2f
+            mov         $0x0E, %ah
+            int         $0x10
+            jmp         1b
+
+2:          pop         %si
+            pop         %bx
+            mov         %bp, %sp
+            pop         %bp
+            ret
+
+message:    .asciz     "Hello, World!"