* remote-sds.c: New file, interface to SDS-compatible monitors.

	* Makefile.in (remote-sds.o): Add build rule.
	* config/powerpc/ppc-eabi.mt, config/powerpc/ppc-sim.mt
 	(TDEPFILES): Add remote-sds.o.

1 files changed, 1278 insertions, 0 deletions

diff --git a/gdb/remote-sds.c b/gdb/remote-sds.c
new file mode 100644
index 0000000..80564a9
--- /dev/null
+++ b/gdb/remote-sds.c
@@ -0,0 +1,1278 @@
+/* Remote target communications for serial-line targets using SDS' protocol.
+   Copyright 1997 Free Software Foundation, Inc.
+
+This file is part of GDB.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* This interface was written by studying the behavior of the SDS
+   monitor on an ADS 821/860 board, and by consulting the
+   documentation of the monitor that is available on Motorola's web
+   site.  -sts 8/13/97 */
+
+#include "defs.h"
+#include "gdb_string.h"
+#include <fcntl.h>
+#include "frame.h"
+#include "inferior.h"
+#include "bfd.h"
+#include "symfile.h"
+#include "target.h"
+#include "wait.h"
+#include "gdbcmd.h"
+#include "objfiles.h"
+#include "gdb-stabs.h"
+#include "gdbthread.h"
+
+#include "dcache.h"
+
+#ifdef USG
+#include <sys/types.h>
+#endif
+
+#include <signal.h>
+#include "serial.h"
+
+/* Declarations of local functions. */
+
+static int sds_write_bytes PARAMS ((CORE_ADDR, char *, int));
+
+static int sds_read_bytes PARAMS ((CORE_ADDR, char *, int));
+
+static void sds_files_info PARAMS ((struct target_ops *ignore));
+
+static int sds_xfer_memory PARAMS ((CORE_ADDR, char *,
+				    int, int, struct target_ops *));
+
+static void sds_prepare_to_store PARAMS ((void));
+
+static void sds_fetch_registers PARAMS ((int));
+
+static void sds_resume PARAMS ((int, int, enum target_signal));
+
+static int sds_start_remote PARAMS ((char *));
+
+static void sds_open PARAMS ((char *, int));
+
+static void sds_close PARAMS ((int));
+
+static void sds_store_registers PARAMS ((int));
+
+static void sds_mourn PARAMS ((void));
+
+static void sds_restart PARAMS ((void));
+
+static void sds_create_inferior PARAMS ((char *, char *, char **));
+
+static int getmessage PARAMS ((unsigned char *, int));
+
+static int putmessage PARAMS ((unsigned char *, int));
+
+static int sds_send PARAMS ((unsigned char *, int));
+
+static int readchar PARAMS ((int));
+
+static int sds_wait PARAMS ((int, struct target_waitstatus *));
+
+static void sds_kill PARAMS ((void));
+
+static int tohex PARAMS ((int));
+
+static int fromhex PARAMS ((int));
+
+static void sds_detach PARAMS ((char *, int));
+
+static void sds_interrupt PARAMS ((int));
+
+static void sds_interrupt_twice PARAMS ((int));
+
+static void interrupt_query PARAMS ((void));
+
+static int read_frame PARAMS ((char *));
+
+static int sds_insert_breakpoint PARAMS ((CORE_ADDR, char *));
+
+static int sds_remove_breakpoint PARAMS ((CORE_ADDR, char *));
+
+
+static struct target_ops sds_ops;	/* Forward decl */
+
+/* This was 5 seconds, which is a long time to sit and wait.
+   Unless this is going though some terminal server or multiplexer or
+   other form of hairy serial connection, I would think 2 seconds would
+   be plenty.  */
+
+/* Changed to allow option to set timeout value.
+   was static int sds_timeout = 2; */
+static int sds_timeout = 2;
+
+/* This variable chooses whether to send a ^C or a break when the user
+   requests program interruption.  Although ^C is usually what remote
+   systems expect, and that is the default here, sometimes a break is
+   preferable instead.  */
+
+static int sds_break;
+
+/* Descriptor for I/O to remote machine.  Initialize it to NULL so
+   that sds_open knows that we don't have a file open when the program
+   starts.  */
+
+static serial_t sds_desc = NULL;
+
+/* Having this larger than 400 causes us to be incompatible with m68k-stub.c
+   and i386-stub.c.  Normally, no one would notice because it only matters
+   for writing large chunks of memory (e.g. in downloads).  Also, this needs
+   to be more than 400 if required to hold the registers (see below, where
+   we round it up based on REGISTER_BYTES).  */
+#define	PBUFSIZ	400
+
+/* Maximum number of bytes to read/write at once.  The value here
+   is chosen to fill up a packet (the headers account for the 32).  */
+#define MAXBUFBYTES ((PBUFSIZ-32)/2)
+
+/* Round up PBUFSIZ to hold all the registers, at least.  */
+/* The blank line after the #if seems to be required to work around a
+   bug in HP's PA compiler.  */
+#if REGISTER_BYTES > MAXBUFBYTES
+
+#undef PBUFSIZ
+#define	PBUFSIZ	(REGISTER_BYTES * 2 + 32)
+#endif
+
+static int next_msg_id;
+
+static int just_started;
+
+static int message_pending;
+
+
+/*  Restart the remote side; this is an extended protocol operation.  */
+
+static void
+sds_restart ()
+{
+}
+
+/* Clean up connection to a remote debugger.  */
+
+/* ARGSUSED */
+static void
+sds_close (quitting)
+     int quitting;
+{
+  if (sds_desc)
+    SERIAL_CLOSE (sds_desc);
+  sds_desc = NULL;
+}
+
+/* Stub for catch_errors.  */
+
+static int
+sds_start_remote (dummy)
+     char *dummy;
+{
+  char c;
+  unsigned char buf[200];
+
+  immediate_quit = 1;		/* Allow user to interrupt it */
+
+  /* Ack any packet which the remote side has already sent.  */
+  SERIAL_WRITE (sds_desc, "{#*\r\n", 5);
+  SERIAL_WRITE (sds_desc, "{#}\r\n", 5);
+
+  while ((c = readchar (1)) >= 0)
+    printf_unfiltered ("%c");
+  printf_unfiltered ("\n");
+
+  next_msg_id = 251;
+
+  buf[0] = 26;
+  sds_send (buf, 1);
+
+  buf[0] = 0;
+  sds_send (buf, 1);
+
+  immediate_quit = 0;
+
+  start_remote ();		/* Initialize gdb process mechanisms */
+  return 1;
+}
+
+/* Open a connection to a remote debugger.
+   NAME is the filename used for communication.  */
+
+static DCACHE *sds_dcache;
+
+static void
+sds_open (name, from_tty)
+     char *name;
+     int from_tty;
+{
+  if (name == 0)
+    error ("To open a remote debug connection, you need to specify what serial\n\
+device is attached to the remote system (e.g. /dev/ttya).");
+
+  target_preopen (from_tty);
+
+  unpush_target (&sds_ops);
+
+  sds_dcache = dcache_init (sds_read_bytes, sds_write_bytes);
+
+  sds_desc = SERIAL_OPEN (name);
+  if (!sds_desc)
+    perror_with_name (name);
+
+  if (baud_rate != -1)
+    {
+      if (SERIAL_SETBAUDRATE (sds_desc, baud_rate))
+	{
+	  SERIAL_CLOSE (sds_desc);
+	  perror_with_name (name);
+	}
+    }
+
+
+  SERIAL_RAW (sds_desc);
+
+  /* If there is something sitting in the buffer we might take it as a
+     response to a command, which would be bad.  */
+  SERIAL_FLUSH_INPUT (sds_desc);
+
+  if (from_tty)
+    {
+      puts_filtered ("Remote debugging using ");
+      puts_filtered (name);
+      puts_filtered ("\n");
+    }
+  push_target (&sds_ops);	/* Switch to using remote target now */
+
+  /* Without this, some commands which require an active target (such
+     as kill) won't work.  This variable serves (at least) double duty
+     as both the pid of the target process (if it has such), and as a
+     flag indicating that a target is active.  These functions should
+     be split out into seperate variables, especially since GDB will
+     someday have a notion of debugging several processes.  */
+
+  inferior_pid = 42000;
+
+  just_started = 1;
+
+  /* Start the remote connection; if error (0), discard this target.
+     In particular, if the user quits, be sure to discard it (we'd be
+     in an inconsistent state otherwise).  */
+  if (!catch_errors (sds_start_remote, (char *)0, 
+		     "Couldn't establish connection to remote target\n",
+		     RETURN_MASK_ALL))
+    pop_target ();
+}
+
+/* This takes a program previously attached to and detaches it.  After
+   this is done, GDB can be used to debug some other program.  We
+   better not have left any breakpoints in the target program or it'll
+   die when it hits one.  */
+
+static void
+sds_detach (args, from_tty)
+     char *args;
+     int from_tty;
+{
+  char buf[PBUFSIZ];
+
+  if (args)
+    error ("Argument given to \"detach\" when remotely debugging.");
+
+#if 0
+  /* Tell the remote target to detach.  */
+  strcpy (buf, "D");
+  sds_send (buf, 1);
+#endif
+
+  pop_target ();
+  if (from_tty)
+    puts_filtered ("Ending remote debugging.\n");
+}
+
+/* Convert hex digit A to a number.  */
+
+static int
+fromhex (a)
+     int a;
+{
+  if (a >= '0' && a <= '9')
+    return a - '0';
+  else if (a >= 'a' && a <= 'f')
+    return a - 'a' + 10;
+  else 
+    error ("Reply contains invalid hex digit %d", a);
+}
+
+/* Convert number NIB to a hex digit.  */
+
+static int
+tohex (nib)
+     int nib;
+{
+  if (nib < 10)
+    return '0'+nib;
+  else
+    return 'a'+nib-10;
+}
+
+static int
+tob64 (inbuf, outbuf, len)
+     unsigned char *inbuf;
+     char *outbuf;
+     int len;
+{
+  int i, sum;
+
+  if (len % 3 != 0)
+    error ("bad length");
+
+  for (i = 0; i < len; i += 3)
+    {
+      /* Collect the next three bytes into a number.  */
+      sum = ((long) *inbuf++) << 16;
+      sum |= ((long) *inbuf++) <<  8;
+      sum |= ((long) *inbuf++);
+
+      /* Spit out 4 6-bit encodings.  */
+      *outbuf++ = ((sum >> 18) & 0x3f) + '0';
+      *outbuf++ = ((sum >> 12) & 0x3f) + '0';
+      *outbuf++ = ((sum >>  6) & 0x3f) + '0';
+      *outbuf++ = (sum & 0x3f) + '0';
+    }
+}
+
+static int
+fromb64 (inbuf, outbuf, len)
+     char *inbuf, *outbuf;
+     int len;
+{
+  int i, sum;
+
+  if (len % 4 != 0)
+    error ("bad length");
+
+  for (i = 0; i < len; i += 4)
+    {
+      /* Collect 4 6-bit digits.  */
+      sum  = (*inbuf++ - '0') << 18;
+      sum |= (*inbuf++ - '0') << 12;
+      sum |= (*inbuf++ - '0') <<  6;
+      sum |= (*inbuf++ - '0');
+
+      /* Now take the resulting 24-bit number and get three bytes out
+         of it.  */
+      *outbuf++ = (sum >> 16) & 0xff;
+      *outbuf++ = (sum >>  8) & 0xff;
+      *outbuf++ = sum & 0xff;
+    }
+
+  return (len / 4) * 3;
+}
+
+
+/* Tell the remote machine to resume.  */
+
+static enum target_signal last_sent_signal = TARGET_SIGNAL_0;
+int last_sent_step;
+
+static void
+sds_resume (pid, step, siggnal)
+     int pid, step;
+     enum target_signal siggnal;
+{
+  unsigned char buf[PBUFSIZ];
+
+  dcache_flush (sds_dcache);
+
+  last_sent_signal = siggnal;
+  last_sent_step = step;
+
+  buf[0] = (step ? 21 : 20);
+  buf[1] = 0;  /* (should be signal?) */
+
+  sds_send (buf, 2);
+}
+
+/* Send ^C to target to halt it.  Target will respond, and send us a
+   packet.  */
+
+static void
+sds_interrupt (signo)
+     int signo;
+{
+  /* If this doesn't work, try more severe steps.  */
+  signal (signo, sds_interrupt_twice);
+  
+  if (remote_debug)
+    printf_unfiltered ("sds_interrupt called\n");
+
+  /* Send a break or a ^C, depending on user preference.  */
+  if (sds_break)
+    SERIAL_SEND_BREAK (sds_desc);
+  else
+    SERIAL_WRITE (sds_desc, "\003", 1);
+}
+
+static void (*ofunc)();
+
+/* The user typed ^C twice.  */
+static void
+sds_interrupt_twice (signo)
+     int signo;
+{
+  signal (signo, ofunc);
+  
+  interrupt_query ();
+
+  signal (signo, sds_interrupt);
+}
+
+/* Ask the user what to do when an interrupt is received.  */
+
+static void
+interrupt_query ()
+{
+  target_terminal_ours ();
+
+  if (query ("Interrupted while waiting for the program.\n\
+Give up (and stop debugging it)? "))
+    {
+      target_mourn_inferior ();
+      return_to_top_level (RETURN_QUIT);
+    }
+
+  target_terminal_inferior ();
+}
+
+/* If nonzero, ignore the next kill.  */
+int kill_kludge;
+
+/* Wait until the remote machine stops, then return, storing status in
+   STATUS just as `wait' would.  Returns "pid" (though it's not clear
+   what, if anything, that means in the case of this target).  */
+
+static int
+sds_wait (pid, status)
+     int pid;
+     struct target_waitstatus *status;
+{
+  unsigned char buf[PBUFSIZ];
+  int retlen;
+
+  status->kind = TARGET_WAITKIND_EXITED;
+  status->value.integer = 0;
+
+  ofunc = (void (*)()) signal (SIGINT, sds_interrupt);
+
+  signal (SIGINT, ofunc);
+
+  if (just_started)
+    {
+      just_started = 0;
+      status->kind = TARGET_WAITKIND_STOPPED;
+      return inferior_pid;
+    }
+
+  while (1)
+    {
+      getmessage (buf, 1);
+
+      if (message_pending)
+	{
+	  buf[0] = 26;
+	  retlen = sds_send (buf, 1);
+	  message_pending = 0;
+	  status->kind = TARGET_WAITKIND_STOPPED;
+	  goto got_status;
+	}
+    }
+ got_status:
+  return inferior_pid;
+}
+
+/* Number of bytes of registers this stub implements.  */
+static int register_bytes_found;
+
+/* Read the remote registers into the block REGS.  */
+/* Currently we just read all the registers, so we don't use regno.  */
+
+/* ARGSUSED */
+static void
+sds_fetch_registers (regno)
+     int regno;
+{
+  unsigned char buf[PBUFSIZ];
+  int i, len;
+  char *p;
+  char regs[REGISTER_BYTES];
+
+  /* Unimplemented registers read as all bits zero.  */
+  memset (regs, 0, REGISTER_BYTES);
+
+  buf[0] = 18;
+  buf[1] = 2;
+  buf[2] = 0;
+  len = sds_send (buf, 3);
+
+  /* Reply describes registers byte by byte.  Suck them all up, then
+     supply them to the register cacheing/storage mechanism.  */
+
+  for (i = 0; i < len; i++)
+    regs[i] = buf[i];
+
+  buf[0] = 18;
+  buf[1] = 1;
+  buf[2] = 0;
+  len = sds_send (buf, 3);
+
+  for (i = 0; i < 4 * 6; i++)
+    {
+      regs[i + 4 * 32 + 8 * 32] = buf[i];
+    }
+
+  /* (should warn about reply too short) */
+
+ supply_them:
+  for (i = 0; i < NUM_REGS; i++)
+    supply_register (i, &regs[REGISTER_BYTE(i)]);
+}
+
+/* Prepare to store registers.  Since we may send them all (using a
+   'G' request), we have to read out the ones we don't want to change
+   first.  */
+
+static void 
+sds_prepare_to_store ()
+{
+  /* Make sure the entire registers array is valid.  */
+  read_register_bytes (0, (char *)NULL, REGISTER_BYTES);
+}
+
+/* Store register REGNO, or all registers if REGNO == -1, from the contents
+   of REGISTERS.  FIXME: ignores errors.  */
+
+static void
+sds_store_registers (regno)
+     int regno;
+{
+  unsigned char buf[PBUFSIZ];
+  int i;
+  char *p;
+
+  buf[0] = 19;
+  buf[1] = 2;
+  buf[2] = 0;
+  buf[3] = 0;
+
+  p = buf + 4;
+
+  for (i = 0; i < 4 * 32; i++)
+    p[i] = registers[i];
+
+  sds_send (buf, 4 + 4 * 32);
+
+  buf[0] = 19;
+  buf[1] = 1;
+  buf[2] = 0;
+  buf[3] = 0;
+
+  p = buf + 4;
+
+  for (i = 0; i < 4 * 10; i++)
+    p[i] = registers[i];
+
+  sds_send (buf, 4 + 4 * 10);
+}
+
+/* 
+   Use of the data cache *used* to be disabled because it loses for looking at
+   and changing hardware I/O ports and the like.  Accepting `volatile'
+   would perhaps be one way to fix it.  Another idea would be to use the
+   executable file for the text segment (for all SEC_CODE sections?
+   For all SEC_READONLY sections?).  This has problems if you want to
+   actually see what the memory contains (e.g. self-modifying code,
+   clobbered memory, user downloaded the wrong thing).  
+
+   Because it speeds so much up, it's now enabled, if you're playing
+   with registers you turn it of (set remotecache 0)
+*/
+
+/* Read a word from remote address ADDR and return it.
+   This goes through the data cache.  */
+
+#if 0	/* unused? */
+static int
+sds_fetch_word (addr)
+     CORE_ADDR addr;
+{
+  return dcache_fetch (sds_dcache, addr);
+}
+
+/* Write a word WORD into remote address ADDR.
+   This goes through the data cache.  */
+
+static void
+sds_store_word (addr, word)
+     CORE_ADDR addr;
+     int word;
+{
+  dcache_poke (sds_dcache, addr, word);
+}
+#endif	/* 0 (unused?) */
+
+
+/* Write memory data directly to the remote machine.  This does not
+   inform the data cache; the data cache uses this.  MEMADDR is the
+   address in the remote memory space.  MYADDR is the address of the
+   buffer in our space.  LEN is the number of bytes.
+
+   Returns number of bytes transferred, or 0 for error.  */
+
+static int
+sds_write_bytes (memaddr, myaddr, len)
+     CORE_ADDR memaddr;
+     char *myaddr;
+     int len;
+{
+  int max_buf_size;		/* Max size of packet output buffer */
+  int origlen;
+  unsigned char buf[PBUFSIZ];
+  int todo;
+  int i;
+
+  /* Chop the transfer down if necessary */
+
+  max_buf_size = 150;
+
+  origlen = len;
+  while (len > 0)
+    {
+      todo = min (len, max_buf_size);
+
+      buf[0] = 13;
+      buf[1] = 0;
+      buf[2] = (int) (memaddr >> 24) & 0xff;
+      buf[3] = (int) (memaddr >> 16) & 0xff;
+      buf[4] = (int) (memaddr >>  8) & 0xff;
+      buf[5] = (int) (memaddr      ) & 0xff;
+      buf[6] = 1;
+      buf[7] = 0;
+
+      for (i = 0; i < todo; i++)
+	buf[i + 8] = myaddr[i];
+
+      sds_send (buf, 8 + todo);
+
+      /* (should look at result) */
+
+      myaddr += todo;
+      memaddr += todo;
+      len -= todo;
+    }
+  return origlen;
+}
+
+/* Read memory data directly from the remote machine.  This does not
+   use the data cache; the data cache uses this.  MEMADDR is the
+   address in the remote memory space.  MYADDR is the address of the
+   buffer in our space.  LEN is the number of bytes.
+
+   Returns number of bytes transferred, or 0 for error.  */
+
+static int
+sds_read_bytes (memaddr, myaddr, len)
+     CORE_ADDR memaddr;
+     char *myaddr;
+     int len;
+{
+  int max_buf_size;		/* Max size of packet output buffer */
+  int origlen, retlen;
+  unsigned char buf[PBUFSIZ];
+  int todo;
+  int i;
+
+  /* Chop the transfer down if necessary */
+
+  max_buf_size = 150;
+
+  origlen = len;
+  while (len > 0)
+    {
+      todo = min (len, max_buf_size);
+
+      buf[0] = 12;
+      buf[1] = 0;
+      buf[2] = (int) (memaddr >> 24) & 0xff;
+      buf[3] = (int) (memaddr >> 16) & 0xff;
+      buf[4] = (int) (memaddr >>  8) & 0xff;
+      buf[5] = (int) (memaddr      ) & 0xff;
+      buf[6] = (int) (todo >> 8) & 0xff;
+      buf[7] = (int) (todo     ) & 0xff;
+      buf[8] = 1;
+
+      retlen = sds_send (buf, 9);
+
+      if (retlen - 2 != todo)
+	{
+	  return 0;
+	}
+
+      /* Reply describes memory byte by byte. */
+
+      for (i = 0; i < todo; i++)
+	myaddr[i] = buf[i + 2];
+
+      myaddr += todo;
+      memaddr += todo;
+      len -= todo;
+    }
+
+  return origlen;
+}
+
+/* Read or write LEN bytes from inferior memory at MEMADDR,
+   transferring to or from debugger address MYADDR.  Write to inferior
+   if SHOULD_WRITE is nonzero.  Returns length of data written or
+   read; 0 for error.  */
+
+/* ARGSUSED */
+static int
+sds_xfer_memory(memaddr, myaddr, len, should_write, target)
+     CORE_ADDR memaddr;
+     char *myaddr;
+     int len;
+     int should_write;
+     struct target_ops *target;			/* ignored */
+{
+  return dcache_xfer_memory (sds_dcache, memaddr, myaddr, len, should_write);
+}
+
+
+static void
+sds_files_info (ignore)
+     struct target_ops *ignore;
+{
+  puts_filtered ("Debugging a target over a serial line.\n");
+}
+
+/* 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 (timeout)
+     int timeout;
+{
+  int ch;
+
+  ch = SERIAL_READCHAR (sds_desc, timeout);
+
+  if (remote_debug > 1 && ch >= 0)
+    printf_unfiltered("%c(%x)", ch, ch);
+
+  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
+compute_checksum (csum, buf, len)
+     int csum, len;
+     char *buf;
+{
+  int i;
+
+  for (i = 0; i < len; ++i)
+    csum += (unsigned char) buf[i];
+
+  csum %= 253;
+  return csum;
+}
+
+/* Send the command in BUF to the remote machine, and read the reply
+   into BUF also.  */
+
+static int
+sds_send (buf, len)
+     unsigned char *buf;
+     int len;
+{
+  putmessage (buf, len);
+
+  return getmessage (buf, 0);
+}
+
+/* Send a message to the remote machine.  */
+
+static int
+putmessage (buf, len)
+     unsigned char *buf;
+     int len;
+{
+  int i;
+  unsigned char csum = 0;
+  char buf2[PBUFSIZ], buf3[PBUFSIZ];
+  unsigned char header[3];
+  int ch;
+  int tcount = 0;
+  char *p;
+
+  /* Copy the packet into buffer BUF2, encapsulating it
+     and giving it a checksum.  */
+
+  if (len > (int) sizeof (buf2) - 5)		/* Prosanity check */
+    abort();
+
+  if (remote_debug)
+    {
+      fprintf_unfiltered (gdb_stderr, "Message to send: \"");
+      for (i = 0; i < len; ++i)
+	fprintf_unfiltered (gdb_stderr, "%02x", buf[i]);
+      fprintf_unfiltered (gdb_stderr, "\"\n");
+    }
+
+  p = buf2;
+  *p++ = '$';
+
+  header[1] = next_msg_id;
+
+  if (len % 3 != 0)
+    {
+      buf[len] = '\0';
+      buf[len+1] = '\0';
+    }
+
+  len = ((len + 2) / 3) * 3;
+
+  header[2] = len;
+
+  csum = compute_checksum (csum, buf, len);
+  csum = compute_checksum (csum, header+1, 2);
+
+  header[0] = csum;
+
+  tob64 (header, p, 3);
+  p += 4;
+  tob64 (buf, buf3, len);
+
+  for (i = 0; i < (len / 3) * 4; i++)
+    {
+      *p++ = buf3[i];
+    }
+  *p++ = '\r';
+  *p++ = '\n';
+
+  next_msg_id = (next_msg_id + 3) % 245;
+
+  /* Send it over and over until we get a positive ack.  */
+
+  while (1)
+    {
+      int started_error_output = 0;
+
+      if (remote_debug)
+	{
+	  *p = '\0';
+	  printf_unfiltered ("Sending encoded: \"%s\"", buf2);
+	  printf_unfiltered ("  (Checksum %d, id %d, length %d)\n",
+			     header[0], header[1], header[2]);
+	  gdb_flush (gdb_stdout);
+	}
+      if (SERIAL_WRITE (sds_desc, buf2, p - buf2))
+	perror_with_name ("putmessage: write failed");
+
+      return 1;
+
+    }
+
+}
+
+/* Come here after finding the start of the frame.  Collect the rest
+   into BUF.  Returns 0 on any error, 1 on success.  */
+
+static int
+read_frame (buf)
+     char *buf;
+{
+  char *bp;
+  int c;
+
+  bp = buf;
+
+  while (1)
+    {
+      c = readchar (sds_timeout);
+
+      switch (c)
+	{
+	case SERIAL_TIMEOUT:
+	  if (remote_debug)
+	    puts_filtered ("Timeout in mid-message, retrying\n");
+	  return 0;
+	case '$':
+	  if (remote_debug)
+	    puts_filtered ("Saw new packet start in middle of old one\n");
+	  return 0;		/* Start a new packet, count retries */
+	case '\r':
+	  break;
+
+	case '\n':
+	  {
+	    *bp = '\000';
+	    if (remote_debug)
+	      printf_filtered ("Received encoded: \"%s\"\n", buf);
+	    return 1;
+	  }
+
+	default:
+	  if (bp < buf + PBUFSIZ - 1)
+	    {
+	      *bp++ = c;
+	      continue;
+	    }
+
+	  *bp = '\0';
+	  puts_filtered ("Message 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 int
+getmessage (buf, forever)
+     unsigned char *buf;
+     int forever;
+{
+  int c, c2, c3;
+  int tries;
+  int timeout;
+  int val, i, len, csum;
+  unsigned char header[3];
+  unsigned char inbuf[500];
+
+  strcpy (buf, "timeout");
+
+  if (forever)
+    {
+#ifdef MAINTENANCE_CMDS
+      timeout = watchdog > 0 ? watchdog : -1;
+#else
+      timeout = -1;
+#endif
+    }
+
+  else
+    timeout = sds_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 sds_timeout intervals.  */
+
+      do
+	{
+	  c = readchar (timeout);
+
+	  if (c == SERIAL_TIMEOUT)
+	    {
+#ifdef MAINTENANCE_CMDS
+	      if (forever)	/* Watchdog went off.  Kill the target. */
+		{
+		  target_mourn_inferior ();
+		  error ("Watchdog has expired.  Target detached.\n");
+		}
+#endif
+	      if (remote_debug)
+		puts_filtered ("Timed out.\n");
+	      goto retry;
+	    }
+	}
+      while (c != '$' && c != '{');
+
+      /* We might have seen a "trigraph", a sequence of three characters
+	 that indicate various sorts of communication state.  */
+
+      if (c == '{')
+	{
+	  /* Read the other two chars of the trigraph. */
+	  c2 = readchar (timeout);
+	  c3 = readchar (timeout);
+	  if (remote_debug)
+	    fprintf_unfiltered (gdb_stderr, "Trigraph %c%c%c received\n",
+				c, c2, c3);
+	  if (c3 == '+')
+	    {
+	      message_pending = 1;
+	      return;
+	    }
+	  continue;
+	}
+
+      val = read_frame (inbuf);
+
+      if (val == 1)
+	{
+	  fromb64 (inbuf, header, 4);
+	  /* (should check out other bits) */
+	  fromb64 (inbuf + 4, buf, strlen (inbuf) - 4);
+
+	  len = header[2];
+
+	  csum = 0;
+	  csum = compute_checksum (csum, buf, len);
+	  csum = compute_checksum (csum, header + 1, 2);
+
+	  if (csum != header[0])
+	    fprintf_unfiltered (gdb_stderr,
+				"Checksum mismatch: computed %d, received %d\n",
+				csum, header[0]);
+
+	  if (header[2] == 0xff)
+	    fprintf_unfiltered (gdb_stderr, "Requesting resend...\n");
+
+	  if (remote_debug)
+	    {
+	      fprintf_unfiltered (gdb_stderr,
+				  "... (Got checksum %d, id %d, length %d)\n",
+				  header[0], header[1], header[2]);
+	      fprintf_unfiltered (gdb_stderr, "Message received: \"");
+	      for (i = 0; i < len; ++i)
+		{
+		  fprintf_unfiltered (gdb_stderr, "%02x", (unsigned char) buf[i]);
+		}
+	      fprintf_unfiltered (gdb_stderr, "\"\n");
+	    }
+
+	  /* no ack required? */
+	  return len;
+	}
+
+      /* Try the whole thing again.  */
+    retry:
+      /* need to do something here */
+    }
+
+  /* We have tried hard enough, and just can't receive the packet.  Give up. */
+
+  printf_unfiltered ("Ignoring packet error, continuing...\n");
+}
+
+static void
+sds_kill ()
+{
+  /* For some mysterious reason, wait_for_inferior calls kill instead of
+     mourn after it gets TARGET_WAITKIND_SIGNALLED.  Work around it.  */
+  if (kill_kludge)
+    {
+      kill_kludge = 0;
+      target_mourn_inferior ();
+      return;
+    }
+
+#if 0 /* fix to use 1-arg fn */
+  /* Use catch_errors so the user can quit from gdb even when we aren't on
+     speaking terms with the remote system.  */
+  catch_errors (putmessage, "k", "", RETURN_MASK_ERROR);
+#endif
+
+  /* Don't wait for it to die.  I'm not really sure it matters whether
+     we do or not.  For the existing stubs, kill is a noop.  */
+  target_mourn_inferior ();
+}
+
+static void
+sds_mourn ()
+{
+  unpush_target (&sds_ops);
+  generic_mourn_inferior ();
+}
+
+static void
+sds_create_inferior (exec_file, args, env)
+     char *exec_file;
+     char *args;
+     char **env;
+{
+  /* Rip out the breakpoints; we'll reinsert them after restarting
+     the remote server.  */
+  remove_breakpoints ();
+
+  /* Now restart the remote server.  */
+  sds_restart ();
+
+  /* Now put the breakpoints back in.  This way we're safe if the
+     restart function works via a unix fork on the remote side.  */
+  insert_breakpoints ();
+
+  /* Clean up from the last time we were running.  */
+  clear_proceed_status ();
+
+  /* Let the remote process run.  */
+  proceed (-1, TARGET_SIGNAL_0, 0);
+}
+
+
+/* The SDS monitor has commands for breakpoint insertion, although it
+   it doesn't actually manage the breakpoints, it just returns the
+   replaced instruction back to the debugger.  */
+
+static int
+sds_insert_breakpoint (addr, contents_cache)
+     CORE_ADDR addr;
+     char *contents_cache;
+{
+  int retlen;
+  unsigned char buf[PBUFSIZ];
+
+  buf[0] = 16;
+  buf[1] = 0;
+
+  retlen = sds_send (buf, 7);
+}
+
+static int
+sds_remove_breakpoint (addr, contents_cache)
+     CORE_ADDR addr;
+     char *contents_cache;
+{
+  int retlen;
+  unsigned char buf[PBUFSIZ];
+
+  buf[0] = 17;
+  buf[1] = 0;
+
+  retlen = sds_send (buf, 7);
+}
+
+/* Define the target operations vector. */
+
+static struct target_ops sds_ops =
+{
+  "sds",			/* to_shortname */
+  "Remote serial target with SDS protocol",	/* to_longname */
+  "Use a remote computer via a serial line, using the SDS protocol.\n\
+Specify the serial device it is connected to (e.g. /dev/ttya).",  /* to_doc */
+  sds_open,			/* to_open */
+  sds_close,			/* to_close */
+  NULL,				/* to_attach */
+  sds_detach,			/* to_detach */
+  sds_resume,			/* to_resume */
+  sds_wait,			/* to_wait */
+  sds_fetch_registers,		/* to_fetch_registers */
+  sds_store_registers,		/* to_store_registers */
+  sds_prepare_to_store,		/* to_prepare_to_store */
+  sds_xfer_memory,		/* to_xfer_memory */
+  sds_files_info,		/* to_files_info */
+  sds_insert_breakpoint,	/* to_insert_breakpoint */
+  sds_remove_breakpoint,	/* to_remove_breakpoint */
+  NULL,				/* to_terminal_init */
+  NULL,				/* to_terminal_inferior */
+  NULL,				/* to_terminal_ours_for_output */
+  NULL,				/* to_terminal_ours */
+  NULL,				/* to_terminal_info */
+  sds_kill,			/* to_kill */
+  generic_load,			/* to_load */
+  NULL,				/* to_lookup_symbol */
+  sds_create_inferior,		/* to_create_inferior */
+  sds_mourn,			/* to_mourn_inferior */
+  0,				/* to_can_run */
+  0,				/* to_notice_signals */
+  0,				/* to_thread_alive */
+  0,				/* to_stop */
+  process_stratum,		/* to_stratum */
+  NULL,				/* to_next */
+  1,				/* to_has_all_memory */
+  1,				/* to_has_memory */
+  1,				/* to_has_stack */
+  1,				/* to_has_registers */
+  1,				/* to_has_execution */
+  NULL,				/* sections */
+  NULL,				/* sections_end */
+  OPS_MAGIC			/* to_magic */
+};
+
+/* Put a command string, in args, out to the monitor and display the
+   reply message.  */
+
+static void
+sds_command (args, from_tty)
+     char *args;
+     int from_tty;
+{
+  char *p;
+  int i, len, resp_len;
+  unsigned char buf[1000];
+
+  /* Convert hexadecimal chars into a byte buffer.  */
+  p = args;
+  len = 0;
+  while (*p != '\0')
+    {
+      buf[len++] = fromhex (p[0]) * 16 + fromhex (p[1]);
+      if (p[1] == '\0')
+	break;
+      p += 2;
+    }
+
+  len = sds_send (buf, len);
+
+  printf_filtered ("Reply is ");
+  for (i = 0; i < len; ++i)
+    {
+      printf_filtered ("%02x", buf[i]);
+    }  
+  printf_filtered ("\n");
+}
+
+void
+_initialize_remote_sds ()
+{
+  add_target (&sds_ops);
+
+  add_show_from_set (add_set_cmd ("sdstimeout", no_class,
+				  var_integer, (char *)&sds_timeout,
+				  "Set timeout value for sds read.\n", &setlist),
+		     &showlist);
+
+  add_com ("sds", class_obscure, sds_command,
+	   "Send a command to the SDS monitor."); 
+}