callback.c

这个是LINUX下的GDB调度工具的源码

static int
os_shutdown (p)
     host_callback *p;
{
  int i, next, j;
  for (i = 0; i < MAX_CALLBACK_FDS; i++)
    {
      int do_close = 1;

      next = p->fd_buddy[i];
      if (next < 0)
	continue;
      do
	{
	  j = next;
	  if (j == MAX_CALLBACK_FDS)
	    do_close = 0;
	  next = p->fd_buddy[j];
	  p->fd_buddy[j] = -1;
	  /* At the initial call of os_init, we got -1, 0, 0, 0, ...  */
	  if (next < 0)
	    {
	      p->fd_buddy[i] = -1;
	      do_close = 0;
	      break;
	    }
	}
      while (j != i);
      if (do_close)
	close (p->fdmap[i]);
    }
  return 1;
}

static int
os_init (p)
     host_callback *p;
{
  int i;

  os_shutdown (p);
  for (i = 0; i < 3; i++)
    {
      p->fdmap[i] = i;
      p->fd_buddy[i] = i - 1;
    }
  p->fd_buddy[0] = MAX_CALLBACK_FDS;
  p->fd_buddy[MAX_CALLBACK_FDS] = 2;

  p->syscall_map = cb_init_syscall_map;
  p->errno_map = cb_init_errno_map;
  p->open_map = cb_init_open_map;

  return 1;
}

/* DEPRECATED */

/* VARARGS */
static void
#ifdef ANSI_PROTOTYPES
os_printf_filtered (host_callback *p ATTRIBUTE_UNUSED, const char *format, ...)
#else
os_printf_filtered (p, va_alist)
     host_callback *p;
     va_dcl
#endif
{
  va_list args;
#ifdef ANSI_PROTOTYPES
  va_start (args, format);
#else
  char *format;

  va_start (args);
  format = va_arg (args, char *);
#endif

  vfprintf (stdout, format, args);
  va_end (args);
}

/* VARARGS */
static void
#ifdef ANSI_PROTOTYPES
os_vprintf_filtered (host_callback *p ATTRIBUTE_UNUSED, const char *format, va_list args)
#else
os_vprintf_filtered (p, format, args)
     host_callback *p;
     const char *format;
     va_list args;
#endif
{
  vprintf (format, args);
}

/* VARARGS */
static void
#ifdef ANSI_PROTOTYPES
os_evprintf_filtered (host_callback *p ATTRIBUTE_UNUSED, const char *format, va_list args)
#else
os_evprintf_filtered (p, format, args)
     host_callback *p;
     const char *format;
     va_list args;
#endif
{
  vfprintf (stderr, format, args);
}

/* VARARGS */
static void
#ifdef ANSI_PROTOTYPES
os_error (host_callback *p ATTRIBUTE_UNUSED, const char *format, ...)
#else
os_error (p, va_alist)
     host_callback *p;
     va_dcl
#endif
{
  va_list args;
#ifdef ANSI_PROTOTYPES
  va_start (args, format);
#else
  char *format;

  va_start (args);
  format = va_arg (args, char *);
#endif

  vfprintf (stderr, format, args);
  fprintf (stderr, "\n");

  va_end (args);
  exit (1);
}

host_callback default_callback =
{
  os_close,
  os_get_errno,
  os_isatty,
  os_lseek,
  os_open,
  os_read,
  os_read_stdin,
  os_rename,
  os_system,
  os_time,
  os_unlink,
  os_write,
  os_write_stdout,
  os_flush_stdout,
  os_write_stderr,
  os_flush_stderr,

  os_stat,
  os_fstat,

  os_ftruncate,
  os_truncate,

  os_poll_quit,

  os_shutdown,
  os_init,

  os_printf_filtered,  /* deprecated */

  os_vprintf_filtered,
  os_evprintf_filtered,
  os_error,

  0, 		/* last errno */

  { 0, },	/* fdmap */
  { -1, },	/* fd_buddy */

  0, /* syscall_map */
  0, /* errno_map */
  0, /* open_map */
  0, /* signal_map */
  0, /* stat_map */
	
  HOST_CALLBACK_MAGIC,
};

/* Read in a file describing the target's system call values.
   E.g. maybe someone will want to use something other than newlib.
   This assumes that the basic system call recognition and value passing/
   returning is supported.  So maybe some coding/recompilation will be
   necessary, but not as much.

   If an error occurs, the existing mapping is not changed.  */

CB_RC
cb_read_target_syscall_maps (cb, file)
     host_callback *cb;
     const char *file;
{
  CB_TARGET_DEFS_MAP *syscall_map, *errno_map, *open_map, *signal_map;
  const char *stat_map;
  FILE *f;

  if ((f = fopen (file, "r")) == NULL)
    return CB_RC_ACCESS;

  /* ... read in and parse file ... */

  fclose (f);
  return CB_RC_NO_MEM; /* FIXME:wip */

  /* Free storage allocated for any existing maps.  */
  if (cb->syscall_map)
    free (cb->syscall_map);
  if (cb->errno_map)
    free (cb->errno_map);
  if (cb->open_map)
    free (cb->open_map);
  if (cb->signal_map)
    free (cb->signal_map);
  if (cb->stat_map)
    free ((PTR) cb->stat_map);

  cb->syscall_map = syscall_map;
  cb->errno_map = errno_map;
  cb->open_map = open_map;
  cb->signal_map = signal_map;
  cb->stat_map = stat_map;

  return CB_RC_OK;
}

/* Translate the target's version of a syscall number to the host's.
   This isn't actually the host's version, rather a canonical form.
   ??? Perhaps this should be renamed to ..._canon_syscall.  */

int
cb_target_to_host_syscall (cb, target_val)
     host_callback *cb;
     int target_val;
{
  CB_TARGET_DEFS_MAP *m;

  for (m = &cb->syscall_map[0]; m->target_val != -1; ++m)
    if (m->target_val == target_val)
      return m->host_val;

  return -1;
}

/* FIXME: sort tables if large.
   Alternatively, an obvious improvement for errno conversion is
   to machine generate a function with a large switch().  */

/* Translate the host's version of errno to the target's.  */

int
cb_host_to_target_errno (cb, host_val)
     host_callback *cb;
     int host_val;
{
  CB_TARGET_DEFS_MAP *m;

  for (m = &cb->errno_map[0]; m->host_val; ++m)
    if (m->host_val == host_val)
      return m->target_val;

  /* ??? Which error to return in this case is up for grabs.
     Note that some missing values may have standard alternatives.
     For now return 0 and require caller to deal with it.  */
  return 0;
}

/* Given a set of target bitmasks for the open system call,
   return the host equivalent.
   Mapping open flag values is best done by looping so there's no need
   to machine generate this function.  */

int
cb_target_to_host_open (cb, target_val)
     host_callback *cb;
     int target_val;
{
  int host_val = 0;
  CB_TARGET_DEFS_MAP *m;

  for (m = &cb->open_map[0]; m->host_val != -1; ++m)
    {
      switch (m->target_val)
	{
	  /* O_RDONLY can be (and usually is) 0 which needs to be treated
	     specially.  */
	case TARGET_O_RDONLY :
	case TARGET_O_WRONLY :
	case TARGET_O_RDWR :
	  if ((target_val & (TARGET_O_RDONLY | TARGET_O_WRONLY | TARGET_O_RDWR))
	      == m->target_val)
	    host_val |= m->host_val;
	  /* Handle the host/target differentiating between binary and
             text mode.  Only one case is of importance */
#if ! defined (TARGET_O_BINARY) && defined (O_BINARY)
	  host_val |= O_BINARY;
#endif
	  break;
	default :
	  if ((m->target_val & target_val) == m->target_val)
	    host_val |= m->host_val;
	  break;
	}
    }

  return host_val;
}

/* Utility for cb_host_to_target_stat to store values in the target's
   stat struct.  */

static void
store (p, size, val, big_p)
     char *p;
     int size;
     long val; /* ??? must be as big as target word size */
     int big_p;
{
  if (big_p)
    {
      p += size;
      while (size-- > 0)
	{
	  *--p = val;
	  val >>= 8;
	}
    }
  else
    {
      while (size-- > 0)
	{
	  *p++ = val;
	  val >>= 8;
	}
    }
}

/* Translate a host's stat struct into a target's.
   If HS is NULL, just compute the length of the buffer required,
   TS is ignored.

   The result is the size of the target's stat struct,
   or zero if an error occurred during the translation.  */

int
cb_host_to_target_stat (cb, hs, ts)
     host_callback *cb;
     const struct stat *hs;
     PTR ts;
{
  const char *m = cb->stat_map;
  char *p;
  int big_p = 0;

  if (hs == NULL)
    ts = NULL;
  p = ts;

  while (m)
    {
      char *q = strchr (m, ',');
      int size;

      /* FIXME: Use sscanf? */
      if (q == NULL)
	{
	  /* FIXME: print error message */
	  return 0;
	}
      size = atoi (q + 1);
      if (size == 0)
	{
	  /* FIXME: print error message */
	  return 0;
	}

      if (hs != NULL)
	{
	  if (strncmp (m, "st_dev", q - m) == 0)
	    store (p, size, hs->st_dev, big_p);
	  else if (strncmp (m, "st_ino", q - m) == 0)
	    store (p, size, hs->st_ino, big_p);
	  /* FIXME:wip */
	  else
	    store (p, size, 0, big_p); /* unsupported field, store 0 */
	}

      p += size;
      m = strchr (q, ':');
      if (m)
	++m;
    }

  return p - (char *) ts;
}

/* Cover functions to the vfprintf callbacks.

   ??? If one thinks of the callbacks as a subsystem onto itself [or part of
   a larger "remote target subsystem"] with a well defined interface, then
   one would think that the subsystem would provide these.  However, until
   one is allowed to create such a subsystem (with its own source tree
   independent of any particular user), such a critter can't exist.  Thus
   these functions are here for the time being.  */

void
sim_cb_printf (host_callback *p, const char *fmt, ...)
{
  va_list ap;

  va_start (ap, fmt);
  p->vprintf_filtered (p, fmt, ap);
  va_end (ap);
}

void
sim_cb_eprintf (host_callback *p, const char *fmt, ...)
{
  va_list ap;

  va_start (ap, fmt);
  p->evprintf_filtered (p, fmt, ap);
  va_end (ap);
}