target.c

早期freebsd实现

   Result is zero if the pushed target ended up on top of the stack,
   nonzero if at least one target is on top of it.

   Rather than allow an empty stack, we always have the dummy target at
   the bottom stratum, so we can call the function vectors without
   checking them.  */

int
push_target (t)
     struct target_ops *t;
{
  struct target_ops *st, *prev;

  for (prev = 0, st = current_target;
       st;
       prev = st, st = st->to_next) {
    if ((int)(t->to_stratum) >= (int)(st->to_stratum))
      break;
  }

  while (t->to_stratum == st->to_stratum) {
    /* There's already something on this stratum.  Close it off.  */
    (st->to_close) (0);
    if (prev)
      prev->to_next = st->to_next;	/* Unchain old target_ops */
    else
      current_target = st->to_next;	/* Unchain first on list */
    st = st->to_next;
  }

  /* We have removed all targets in our stratum, now add ourself.  */
  t->to_next = st;
  if (prev)
    prev->to_next = t;
  else
    current_target = t;

  cleanup_target (current_target);
  return prev != 0;
}

/* Remove a target_ops vector from the stack, wherever it may be. 
   Return how many times it was removed (0 or 1 unless bug).  */

int
unpush_target (t)
     struct target_ops *t;
{
  struct target_ops *u, *v;
  int result = 0;

  for (u = current_target, v = 0;
       u;
       v = u, u = u->to_next)
    if (u == t)
      {
	if (v == 0)
	  pop_target();			/* unchain top copy */
	else {
	  (t->to_close)(0);		/* Let it clean up */
	  v->to_next = t->to_next;	/* unchain middle copy */
	}
	result++;
      }
  return result;
}

void
pop_target ()
{
  (current_target->to_close)(0);	/* Let it clean up */
  current_target = current_target->to_next;
  if (!current_target)		/* At bottom, push dummy.  */
    push_target (&dummy_target);
}

#define MIN(A, B) (((A) <= (B)) ? (A) : (B))

/* target_read_string -- read a null terminated string from MEMADDR in target.
   The read may also be terminated early by getting an error from target_xfer_
   memory.
   LEN is the size of the buffer pointed to by MYADDR.  Note that a terminating
   null will only be written if there is sufficient room.  The return value is
   is the number of bytes (including the null) actually transferred.
*/

int
target_read_string (memaddr, myaddr, len)
     CORE_ADDR memaddr;
     char *myaddr;
     int len;
{
  int tlen, origlen, offset, i;
  char buf[4];

  origlen = len;

  while (len > 0)
    {
      tlen = MIN (len, 4 - (memaddr & 3));
      offset = memaddr & 3;

      if (target_xfer_memory (memaddr & ~3, buf, 4, 0))
	return origlen - len;

      for (i = 0; i < tlen; i++)
	{
	  *myaddr++ = buf[i + offset];
	  if (buf[i + offset] == '\000')
	    return (origlen - len) + i + 1;
	}

      memaddr += tlen;
      len -= tlen;
    }
  return origlen;
}

/* Move memory to or from the targets.  Iterate until all of it has
   been moved, if necessary.  The top target gets priority; anything
   it doesn't want, is offered to the next one down, etc.  Note the
   business with curlen:  if an early target says "no, but I have a
   boundary overlapping this xfer" then we shorten what we offer to
   the subsequent targets so the early guy will get a chance at the
   tail before the subsequent ones do. 

   Result is 0 or errno value.  */

int
target_read_memory (memaddr, myaddr, len)
     CORE_ADDR memaddr;
     char *myaddr;
     int len;
{
  return target_xfer_memory (memaddr, myaddr, len, 0);
}

int
target_write_memory (memaddr, myaddr, len)
     CORE_ADDR memaddr;
     char *myaddr;
     int len;
{
  return target_xfer_memory (memaddr, myaddr, len, 1);
}
 
int
target_xfer_memory (memaddr, myaddr, len, write)
     CORE_ADDR memaddr;
     char *myaddr;
     int len;
     int write;
{
  int curlen;
  int res;
  struct target_ops *t;
  
  /* The quick case is that the top target does it all.  */
  res = current_target->to_xfer_memory
			(memaddr, myaddr, len, write, current_target);
  if (res == len)
    return 0;

  if (res > 0)
    goto bump;
  /* If res <= 0 then we call it again in the loop.  Ah well.  */

  for (; len > 0;)
    {
      curlen = len;		/* Want to do it all */
      for (t = current_target;
	   t;
	   t = t->to_has_all_memory? 0: t->to_next)
	{
	  res = t->to_xfer_memory(memaddr, myaddr, curlen, write, t);
	  if (res > 0) break;	/* Handled all or part of xfer */
	  if (res == 0) continue;	/* Handled none */
	  curlen = -res;	/* Could handle once we get past res bytes */
	}
      if (res <= 0)
	{
	  /* If this address is for nonexistent memory,
	     read zeros if reading, or do nothing if writing.  Return error. */
	  if (!write)
	    memset (myaddr, 0, len);
	  if (errno == 0)
	    return EIO;
	  else
	    return errno;
	}
bump:
      memaddr += res;
      myaddr  += res;
      len     -= res;
    }
  return 0;			/* We managed to cover it all somehow. */
}


/* ARGSUSED */
static void
target_info (args, from_tty)
     char *args;
     int from_tty;
{
  struct target_ops *t;
  int has_all_mem = 0;
  
  if (symfile_objfile != NULL)
    printf ("Symbols from \"%s\".\n", symfile_objfile->name);

#ifdef FILES_INFO_HOOK
  if (FILES_INFO_HOOK ())
    return;
#endif

  for (t = current_target;
       t;
       t = t->to_next)
    {
      if ((int)(t->to_stratum) <= (int)dummy_stratum)
	continue;
      if (has_all_mem)
	printf("\tWhile running this, gdb does not access memory from...\n");
      printf("%s:\n", t->to_longname);
      (t->to_files_info)(t);
      has_all_mem = t->to_has_all_memory;
    }
}

/* This is to be called by the open routine before it does
   anything.  */

void
target_preopen (from_tty)
     int from_tty;
{
  dont_repeat();

  if (target_has_execution)
    {   
      if (query ("A program is being debugged already.  Kill it? "))
        target_kill ();
      else
        error ("Program not killed.");
    }
}

/* Look through the list of possible targets for a target that can
   execute a run or attach command without any other data.  This is
   used to locate the default process stratum.

   Result is always valid (error() is called for errors).  */

static struct target_ops *
find_default_run_target (do_mesg)
     char *do_mesg;
{
  struct target_ops **t;
  struct target_ops *runable;
  int count;

  count = 0;

  for (t = target_structs; t < target_structs + target_struct_size;
       ++t)
    {
      if (target_can_run(*t))
	{
	  runable = *t;
	  ++count;
	}
    }

  if (count != 1)
    error ("Don't know how to %s.  Try \"help target\".", do_mesg);

  return runable;
}

void
find_default_attach (args, from_tty)
     char *args;
     int from_tty;
{
  struct target_ops *t;

  t = find_default_run_target("attach");
  (t->to_attach) (args, from_tty);
  return;
}

void
find_default_create_inferior (exec_file, allargs, env)
     char *exec_file;
     char *allargs;
     char **env;
{
  struct target_ops *t;

  t = find_default_run_target("run");
  (t->to_create_inferior) (exec_file, allargs, env);
  return;
}

static int
return_zero ()
{
  return 0;
}

struct target_ops *
find_core_target ()
{
  struct target_ops **t;
  struct target_ops *runable;
  int count;
  
  count = 0;
  
  for (t = target_structs; t < target_structs + target_struct_size;
       ++t)
    {
      if ((*t)->to_stratum == core_stratum)
	{
	  runable = *t;
	  ++count;
	}
    }
  
  return(count == 1 ? runable : NULL);
}
  

static char targ_desc[] = 
    "Names of targets and files being debugged.\n\
Shows the entire stack of targets currently in use (including the exec-file,\n\
core-file, and process, if any), as well as the symbol file name.";

void
_initialize_targets ()
{
  current_target = &dummy_target;
  cleanup_target (current_target);

  add_info ("target", target_info, targ_desc);
  add_info ("files", target_info, targ_desc);
}