[Kobaz]

Fixed code seems to be:

__asm __volatile (

             "push  %%ebx\n"

             "xorl   %%ebx, %%ebx\n"
              "movl   %1, %%esi\n"   

(cut many lines)

              "xorl   (%%edi,%%ebx,4), %%eax\n"

      "2:\n"
               "pop  %%ebx\n"

              :
              : "a" (val), "g" (buf), "g" (bufsize)
              : "cx", "dx", "si", "di"
      );
        
      return val;