debug ISR: display flags

kernel/debug.asm

@@ -14,8 +14,27 @@ isr_debug:
   push ax
 
   call printf
-  db "AX=%X BX=%X CX=%X DX=%X SP=%X BP=%X SI=%X DI=%X", 0x0A, 0x0D
+  db "AX=%X BX=%X CX=%X DX=%X", 0x20
-  db "DS=%X ES=%X SS=%X IP=%X CS=%X FL=%X", 0x0A, 0x0D, 0
+  db "SP=%X BP=%X SI=%X DI=%X", 0x0A, 0x0D
+  db "DS=%X ES=%X SS=%X IP=%X CS=%X", 0x20, 0
+
+  mov bp, sp
+  mov bx, [ss:bp+26]
+  mov si, .flags
+  mov cx, 0x0010
+.loop:
+  mov al, [cs:si]
+  inc si
+  test bx, 0x8000
+  jnz .write
+  mov al, '-'
+.write:
+  sal bx, 1
+  call putc
+  loop .loop
+
+  call printf
+  db 0x0A, 0x0D, 0
 
   pop ax
   pop bx
@@ -28,4 +47,7 @@ isr_debug:
   pop ds
   pop es
   pop ss
-  iret
+  iret
+.flags:
+  ; 16 letters for each bit in flags register
+  db "++++ODITSZ+A+P+C"