===== qemu_lib.c =====

  #include <stdint.h>

  // the version of print implemented in assembly
  extern void as_print(char *str);

  #define UART0DR(x)    (*((volatile unsigned int *)(x)))

  #define A8_REG 0x10009000
  #define VERSATILEPB_REG 0x0101f1000
  #define USED_REG  A8_REG
  
  /*versatilepb uartd 0x0101f1000*/
  volatile unsigned char * const UART0_BASE = (unsigned char *) A8_REG;

  void copy_vectors(void) {
   extern uint32_t vectors_start;
   extern uint32_t vectors_end;
   uint32_t *vectors_src = &vectors_start;
   uint32_t *vectors_dst = (uint32_t *)0;

  while(vectors_src < &vectors_end)
   *vectors_dst++ = *vectors_src++;
  }

  void print_string(const char *str)
  {
    while(*str != '\0')
    {
      *UART0_BASE = *str;
      str++;
    }
  }

  void uart_send(unsigned int c)
  {
    *UART0_BASE = c;
  }

  static void printint(int xx, int base, int sign)
  {
    static char digits[] = "0123456789abcdef";
    char buf[16];
    int i;
    unsigned int x;

    if(sign && (sign = xx < 0))
     x = -xx;
    else
     x = xx;

    i = 0;
    do{
     buf[i++] = digits[x % base];
    }while((x /= base) != 0);

    if(sign)
     buf[i++] = '-';

    while(--i >= 0)
     uart_send(buf[i]);
  }

  void cprintf(char *fmt, ...)
  {
   int i, c;
   unsigned int *argp;
   char *s;
   
   argp = (unsigned int*)(void*)(&fmt + 1);
   for(i = 0; (c = fmt[i] & 0xff) != 0; i++)
   {
     if(c != '%')
     {
       uart_send(c);
       continue;
     }
     c = fmt[++i] & 0xff;
     if(c == 0)
       break;
     switch(c)
     {
     case 'd':
       printint(*argp++, 10, 1);
       break;
     case 'x':
     case 'p':
       printint(*argp++, 16, 0);
       break;
     case 's':
       if((s = (char*)*argp++) == 0)
         s = "(null)";
       for(; *s; s++)
        uart_send(*s);
       break;
     case '%':
       uart_send('%');
       break;
     default:
       // Print unknown % sequence to draw attention.
      uart_send('%');
      uart_send(c);
      break;
     }
    }   
  }
  
  void swi_code ( unsigned int inst)
  {
    print_string("In SWI_CODE\n");
    cprintf("SWI SYSCALL : %x\n", inst);
  }