remote.c

嵌入式ARM的一些源代码

     int len;
{
  unsigned char *buf = alloca (PBUFSIZ);
  int max_buf_size;		/* Max size of packet output buffer */
  int origlen;
  extern int verbose;

  /* Verify that the target can support a binary download */
  check_binary_download (memaddr);

  /* Chop the transfer down if necessary */

  max_buf_size = min (remote_write_size, PBUFSIZ);
  if (remote_register_buf_size != 0)
    max_buf_size = min (max_buf_size, remote_register_buf_size);

  /* Subtract header overhead from max payload size -  $M<memaddr>,<len>:#nn */
  max_buf_size -= 2 + hexnumlen (memaddr + len - 1) + 1 + hexnumlen (len) + 4;

  origlen = len;
  while (len > 0)
    {
      unsigned char *p, *plen;
      int todo;
      int i;

      /* construct "M"<memaddr>","<len>":" */
      /* sprintf (buf, "M%lx,%x:", (unsigned long) memaddr, todo); */
      memaddr = remote_address_masked (memaddr);
      p = buf;
      if (remote_binary_download)
	{
	  *p++ = 'X';
	  todo = min (len, max_buf_size);
	}
      else
	{
	  *p++ = 'M';
	  todo = min (len, max_buf_size / 2);	/* num bytes that will fit */
	}

      p += hexnumstr ((char *)p, (ULONGEST) memaddr);
      *p++ = ',';

      plen = p;			/* remember where len field goes */
      p += hexnumstr ((char *)p, (ULONGEST) todo);
      *p++ = ':';
      *p = '\0';

      /* We send target system values byte by byte, in increasing byte
         addresses, each byte encoded as two hex characters (or one
         binary character).  */
      if (remote_binary_download)
	{
	  int escaped = 0;
	  for (i = 0;
	       (i < todo) && (i + escaped) < (max_buf_size - 2);
	       i++)
	    {
	      switch (myaddr[i] & 0xff)
		{
		case '$':
		case '#':
		case 0x7d:
		  /* These must be escaped */
		  escaped++;
		  *p++ = 0x7d;
		  *p++ = (myaddr[i] & 0xff) ^ 0x20;
		  break;
		default:
		  *p++ = myaddr[i] & 0xff;
		  break;
		}
	    }

	  if (i < todo)
	    {
	      /* Escape chars have filled up the buffer prematurely, 
	         and we have actually sent fewer bytes than planned.
	         Fix-up the length field of the packet.  */

	      /* FIXME: will fail if new len is a shorter string than 
	         old len.  */

	      plen += hexnumstr ((char *)plen, (ULONGEST) i);
	      *plen++ = ':';
	    }
	}
      else
	{
	  for (i = 0; i < todo; i++)
	    {
	      *p++ = tohex ((myaddr[i] >> 4) & 0xf);
	      *p++ = tohex (myaddr[i] & 0xf);
	    }
	  *p = '\0';
	}

      putpkt_binary ((char *)buf, (int) (p - buf));
      getpkt ((char *)buf, 0);

      if (buf[0] == 'E')
	{
	  /* There is no correspondance between what the remote protocol uses
	     for errors and errno codes.  We would like a cleaner way of
	     representing errors (big enough to include errno codes, bfd_error
	     codes, and others).  But for now just return EIO.  */
	  errno = EIO;
	  return 0;
	}

      /* Increment by i, not by todo, in case escape chars 
         caused us to send fewer bytes than we'd planned.  */
      myaddr += i;
      memaddr += i;
      len -= i;

      if (verbose)
	putc('.', stderr);
    }
  return origlen;
}

/* Stuff for dealing with the packets which are part of this protocol.
   See comment at top of file for details.  */

/* Read a single character from the remote end, masking it down to 7 bits. */

static int
readchar (int timeout)
{
  int ch;

  ch = SERIAL_READCHAR (remote_desc, timeout);

  switch (ch)
    {
    case SERIAL_EOF:
      error ("Remote connection closed");
    case SERIAL_ERROR:
      perror_with_name ("Remote communication error");
    case SERIAL_TIMEOUT:
      return ch;
    default:
      return ch & 0x7f;
    }
}

static int
putpkt (buf)
     char *buf;
{
  return putpkt_binary (buf, strlen (buf));
}

/* Send a packet to the remote machine, with error checking.  The data
   of the packet is in BUF.  The string in BUF can be at most  PBUFSIZ - 5
   to account for the $, # and checksum, and for a possible /0 if we are
   debugging (remote_debug) and want to print the sent packet as a string */

static int
putpkt_binary (buf, cnt)
     char *buf;
     int cnt;
{
  int i;
  unsigned char csum = 0;
  char *buf2 = alloca (PBUFSIZ);
  char *junkbuf = alloca (PBUFSIZ);

  int ch;
  int tcount = 0;
  char *p;

  /* Copy the packet into buffer BUF2, encapsulating it
     and giving it a checksum.  */

  if (cnt > BUFSIZ - 5)		/* Prosanity check */
    abort ();

  p = buf2;
  *p++ = '$';

  for (i = 0; i < cnt; i++)
    {
      csum += buf[i];
      *p++ = buf[i];
    }
  *p++ = '#';
  *p++ = tohex ((csum >> 4) & 0xf);
  *p++ = tohex (csum & 0xf);

  /* Send it over and over until we get a positive ack.  */

  while (1)
    {
      int started_error_output = 0;

      if (remote_debug)
	{
	  *p = '\0';
	  fprintf_unfiltered (gdb_stdlog, "Sending packet: ");
	  fputstrn_unfiltered (buf2, p - buf2, 0, gdb_stdlog);
	  fprintf_unfiltered (gdb_stdlog, "...");
	  gdb_flush (gdb_stdlog);
	}
      if (SERIAL_WRITE (remote_desc, buf2, p - buf2))
	perror_with_name ("putpkt: write failed");

      /* read until either a timeout occurs (-2) or '+' is read */
      while (1)
	{
	  ch = readchar (remote_timeout);

	  if (remote_debug)
	    {
	      switch (ch)
		{
		case '+':
		case SERIAL_TIMEOUT:
		case '$':
		  if (started_error_output)
		    {
		      putchar_unfiltered ('\n');
		      started_error_output = 0;
		    }
		}
	    }

	  switch (ch)
	    {
	    case '+':
	      if (remote_debug)
		fprintf_unfiltered (gdb_stdlog, "Ack\n");
	      return 1;
	    case SERIAL_TIMEOUT:
	      tcount++;
	      if (tcount > 3)
		return 0;
	      break;		/* Retransmit buffer */
	    case '$':
	      {
		/* It's probably an old response, and we're out of sync.
		   Just gobble up the packet and ignore it.  */
		getpkt (junkbuf, 0);
		continue;	/* Now, go look for + */
	      }
	    default:
	      if (remote_debug)
		{
		  if (!started_error_output)
		    {
		      started_error_output = 1;
		      fprintf_unfiltered (gdb_stdlog, "putpkt: Junk: ");
		    }
		  fputc_unfiltered (ch & 0177, gdb_stdlog);
		}
	      continue;
	    }
	  break;		/* Here to retransmit */
	}

#if 0
      /* This is wrong.  If doing a long backtrace, the user should be
         able to get out next time we call QUIT, without anything as
         violent as interrupt_query.  If we want to provide a way out of
         here without getting to the next QUIT, it should be based on
         hitting ^C twice as in remote_wait.  */
      if (quit_flag)
	{
	  quit_flag = 0;
	  interrupt_query ();
	}
#endif
    }
}

/* Come here after finding the start of the frame.  Collect the rest
   into BUF, verifying the checksum, length, and handling run-length
   compression.  Returns 0 on any error, 1 on success.  */

static int
read_frame (char *buf)
{
  unsigned char csum;
  char *bp;
  int c;

  csum = 0;
  bp = buf;

  while (1)
    {
      c = readchar (remote_timeout);

      switch (c)
	{
	case SERIAL_TIMEOUT:
	  if (remote_debug)
	    fputs_filtered ("Timeout in mid-packet, retrying\n", gdb_stdlog);
	  return 0;
	case '$':
	  if (remote_debug)
	    fputs_filtered ("Saw new packet start in middle of old one\n",
			    gdb_stdlog);
	  return 0;		/* Start a new packet, count retries */
	case '#':
	  {
	    unsigned char pktcsum;

	    *bp = '\000';

	    pktcsum = fromhex (readchar (remote_timeout)) << 4;
	    pktcsum |= fromhex (readchar (remote_timeout));

	    if (csum == pktcsum)
	      {
		return 1;
	      }

	    if (remote_debug)
	      {
		fprintf_filtered (gdb_stdlog,
			      "Bad checksum, sentsum=0x%x, csum=0x%x, buf=",
				  pktcsum, csum);
		fputs_filtered (buf, gdb_stdlog);
		fputs_filtered ("\n", gdb_stdlog);
	      }
	    return 0;
	  }
	case '*':		/* Run length encoding */
	  csum += c;
	  c = readchar (remote_timeout);
	  csum += c;
	  c = c - ' ' + 3;	/* Compute repeat count */

	  if (c > 0 && c < 255 && bp + c - 1 < buf + PBUFSIZ - 1)
	    {
	      memset (bp, *(bp - 1), c);
	      bp += c;
	      continue;
	    }

	  *bp = '\0';
	  printf_filtered ("Repeat count %d too large for buffer: ", c);
	  puts_filtered (buf);
	  puts_filtered ("\n");
	  return 0;
	default:
	  if (bp < buf + PBUFSIZ - 1)
	    {
	      *bp++ = c;
	      csum += c;
	      continue;
	    }

	  *bp = '\0';
	  puts_filtered ("Remote packet too long: ");
	  puts_filtered (buf);
	  puts_filtered ("\n");

	  return 0;
	}
    }
}

/* Read a packet from the remote machine, with error checking, and
   store it in BUF.  BUF is expected to be of size PBUFSIZ.  If
   FOREVER, wait forever rather than timing out; this is used while
   the target is executing user code.  */

static void
getpkt (buf, forever)
     char *buf;
     int forever;
{
  int c;
  int tries;
  int timeout;
  int val;

  strcpy (buf, "timeout");

  if (forever)
    {
      timeout = watchdog > 0 ? watchdog : -1;
    }

  else
    timeout = remote_timeout;

#define MAX_TRIES 3

  for (tries = 1; tries <= MAX_TRIES; tries++)
    {
      /* This can loop forever if the remote side sends us characters
         continuously, but if it pauses, we'll get a zero from readchar
         because of timeout.  Then we'll count that as a retry.  */

      /* Note that we will only wait forever prior to the start of a packet.
         After that, we expect characters to arrive at a brisk pace.  They
         should show up within remote_timeout intervals.  */

      do
	{
	  c = readchar (timeout);

	  if (c == SERIAL_TIMEOUT)
	    {
	      if (forever)	/* Watchdog went off.  Kill the target. */
		{
		  target_mourn_inferior ();
		  error ("Watchdog has expired.  Target detached.\n");
		}
	      if (remote_debug)
		fputs_filtered ("Timed out.\n", gdb_stdlog);
	      goto retry;
	    }
	}
      while (c != '$');

      /* We've found the start of a packet, now collect the data.  */

      val = read_frame (buf);

      if (val == 1)
	{
	  if (remote_debug)
	    {
	      fprintf_unfiltered (gdb_stdlog, "Packet received: ");
	      fputstr_unfiltered (buf, 0, gdb_stdlog);
	      fprintf_unfiltered (gdb_stdlog, "\n");
	    }
	  SERIAL_WRITE (remote_desc, "+", 1);
	  return;
	}

      /* Try the whole thing again.  */
    retry:
      SERIAL_WRITE (remote_desc, "-", 1);
    }

  /* We have tried hard enough, and just can't receive the packet.  Give up. */

  printf_unfiltered ("Ignoring packet error, continuing...\n");
  SERIAL_WRITE (remote_desc, "+", 1);
}