static void
inf_ptrace_create_inferior (struct target_ops *ops,
			    char *exec_file, char *allargs, char **env,
			    int from_tty)
{
  int pid;

  /* Do not change either targets above or the same target if already present.
     The reason is the target stack is shared across multiple inferiors.  */
  int ops_already_pushed = target_is_pushed (ops);
  struct cleanup *back_to = make_cleanup (null_cleanup, NULL);

  if (! ops_already_pushed)
    {
      /* Clear possible core file with its process_stratum.  */
      push_target (ops);
      make_cleanup_unpush_target (ops);
    }

  pid = fork_inferior (exec_file, allargs, env, inf_ptrace_me, NULL,
		       NULL, NULL, NULL);

  discard_cleanups (back_to);

  startup_inferior (START_INFERIOR_TRAPS_EXPECTED);

  /* On some targets, there must be some explicit actions taken after
     the inferior has been started up.  */
  target_post_startup_inferior (pid_to_ptid (pid));
}

static void
i386_linux_dr_set_control (unsigned long control)
{
  ptid_t pid_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));

  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
}

static void
inf_ptrace_create_inferior (struct target_ops *ops,
			    char *exec_file, char *allargs, char **env,
			    int from_tty)
{
  int pid;

  pid = fork_inferior (exec_file, allargs, env, inf_ptrace_me, NULL,
		       NULL, NULL);

  push_target (ops);

  /* On some targets, there must be some explicit synchronization
     between the parent and child processes after the debugger
     forks, and before the child execs the debuggee program.  This
     call basically gives permission for the child to exec.  */

  target_acknowledge_created_inferior (pid);

  /* START_INFERIOR_TRAPS_EXPECTED is defined in inferior.h, and will
     be 1 or 2 depending on whether we're starting without or with a
     shell.  */
  startup_inferior (START_INFERIOR_TRAPS_EXPECTED);

  /* On some targets, there must be some explicit actions taken after
     the inferior has been started up.  */
  target_post_startup_inferior (pid_to_ptid (pid));
}

static void
sol_thread_detach (char *args, int from_tty)
{
  inferior_ptid = pid_to_ptid (PIDGET (main_ph.ptid));
  unpush_target (&sol_thread_ops);
  procfs_ops.to_detach (args, from_tty);
}

static int
inf_ptrace_follow_fork (struct target_ops *ops, int follow_child)
{
  pid_t pid, fpid;
  ptrace_state_t pe;

  /* FIXME: kettenis/20050720: This stuff should really be passed as
     an argument by our caller.  */
  {
    ptid_t ptid;
    struct target_waitstatus status;

    get_last_target_status (&ptid, &status);
    gdb_assert (status.kind == TARGET_WAITKIND_FORKED);

    pid = ptid_get_pid (ptid);
  }

  if (ptrace (PT_GET_PROCESS_STATE, pid,
	       (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)
    perror_with_name (("ptrace"));

  gdb_assert (pe.pe_report_event == PTRACE_FORK);
  fpid = pe.pe_other_pid;

  if (follow_child)
    {
      inferior_ptid = pid_to_ptid (fpid);
      detach_breakpoints (pid);

      /* Reset breakpoints in the child as appropriate.  */
      follow_inferior_reset_breakpoints ();

      if (ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3)1, 0) == -1)
	perror_with_name (("ptrace"));
    }
  else
    {
      inferior_ptid = pid_to_ptid (pid);
      detach_breakpoints (fpid);

      if (ptrace (PT_DETACH, fpid, (PTRACE_TYPE_ARG3)1, 0) == -1)
	perror_with_name (("ptrace"));
    }

  return 0;
}

void
add_pid_to_list (struct inferior_list *list, unsigned long pid)
{
  struct inferior_list_entry *new_entry;

  new_entry = xmalloc (sizeof (struct inferior_list_entry));
  new_entry->id = pid_to_ptid (pid);
  add_inferior_to_list (list, new_entry);
}

static void
i386_linux_dr_set_addr (int regnum, CORE_ADDR addr)
{
  ptid_t pid_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));

  gdb_assert (regnum >= 0 && regnum <= DR_LASTADDR - DR_FIRSTADDR);

  linux_nat_iterate_watchpoint_lwps (update_debug_registers_callback, NULL);
}

static void
amd64_linux_dr_set_addr (int regnum, CORE_ADDR addr)
{
  ptid_t pid_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));

  gdb_assert (regnum >= 0 && regnum <= DR_LASTADDR - DR_FIRSTADDR);

  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
}

static int
inf_ptrace_follow_fork (struct target_ops *ops, int follow_child,
			int detach_fork)
{
  pid_t pid, fpid;
  ptrace_state_t pe;

  pid = ptid_get_pid (inferior_ptid);

  if (ptrace (PT_GET_PROCESS_STATE, pid,
	       (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)
    perror_with_name (("ptrace"));

  gdb_assert (pe.pe_report_event == PTRACE_FORK);
  fpid = pe.pe_other_pid;

  if (follow_child)
    {
      struct inferior *parent_inf, *child_inf;
      struct thread_info *tp;

      parent_inf = find_inferior_pid (pid);

      /* Add the child.  */
      child_inf = add_inferior (fpid);
      child_inf->attach_flag = parent_inf->attach_flag;
      copy_terminal_info (child_inf, parent_inf);
      child_inf->pspace = parent_inf->pspace;
      child_inf->aspace = parent_inf->aspace;

      /* Before detaching from the parent, remove all breakpoints from
	 it.  */
      remove_breakpoints ();

      if (ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3)1, 0) == -1)
	perror_with_name (("ptrace"));

      /* Switch inferior_ptid out of the parent's way.  */
      inferior_ptid = pid_to_ptid (fpid);

      /* Delete the parent.  */
      detach_inferior (pid);

      add_thread_silent (inferior_ptid);
    }
  else
    {
      /* Breakpoints have already been detached from the child by
	 infrun.c.  */

      if (ptrace (PT_DETACH, fpid, (PTRACE_TYPE_ARG3)1, 0) == -1)
	perror_with_name (("ptrace"));
    }

  return 0;
}

static ptid_t
rs6000_wait (ptid_t ptid, struct target_waitstatus *ourstatus)
{
  pid_t pid;
  int status, save_errno;

  do
    {
      set_sigint_trap ();
      set_sigio_trap ();

      do
	{
	  pid = waitpid (ptid_get_pid (ptid), &status, 0);
	  save_errno = errno;
	}
      while (pid == -1 && errno == EINTR);

      clear_sigio_trap ();
      clear_sigint_trap ();

      if (pid == -1)
	{
	  fprintf_unfiltered (gdb_stderr,
			      _("Child process unexpectedly missing: %s.\n"),
			      safe_strerror (save_errno));

	  /* Claim it exited with unknown signal.  */
	  ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
	  ourstatus->value.sig = TARGET_SIGNAL_UNKNOWN;
	  return minus_one_ptid;
	}

      /* Ignore terminated detached child processes.  */
      if (!WIFSTOPPED (status) && pid != ptid_get_pid (inferior_ptid))
	pid = -1;
    }
  while (pid == -1);

  /* AIX has a couple of strange returns from wait().  */

  /* stop after load" status.  */
  if (status == 0x57c)
    ourstatus->kind = TARGET_WAITKIND_LOADED;
  /* signal 0. I have no idea why wait(2) returns with this status word.  */
  else if (status == 0x7f)
    ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
  /* A normal waitstatus.  Let the usual macros deal with it.  */
  else
    store_waitstatus (ourstatus, status);

  return pid_to_ptid (pid);
}

static void
fbsd_thread_deactivate (void)
{
  if (target_has_execution)
    disable_thread_event_reporting();
  td_ta_delete_p (thread_agent);

  inferior_ptid = pid_to_ptid (proc_handle.pid);
  proc_handle.pid = 0;
  fbsd_thread_active = 0;
  fbsd_thread_present = 0;
}

struct process_info *
add_process (int pid, int attached)
{
  struct process_info *process = XCNEW (struct process_info);

  process->entry.id = pid_to_ptid (pid);
  process->attached = attached;

  add_inferior_to_list (&all_processes, &process->entry);

  return process;
}

static void
fbsd_thread_deactivate (void)
{
  if (fbsd_thread_core == 0)
    disable_thread_event_reporting();
  td_ta_delete_p (thread_agent);

  inferior_ptid = pid_to_ptid (proc_handle.pid);
  proc_handle.pid = 0;
  fbsd_thread_active = 0;
  fbsd_thread_present = 0;
  init_thread_list ();
}

/* Wait for the inferior process to change state.
   STATUS will be filled in with a response code to send to GDB.
   Returns the signal which caused the process to stop. */
static ptid_t
win32_wait (ptid_t ptid, struct target_waitstatus *ourstatus, int options)
{
  struct regcache *regcache;

  while (1)
    {
      if (!get_child_debug_event (ourstatus))
	continue;

      switch (ourstatus->kind)
	{
	case TARGET_WAITKIND_EXITED:
	  OUTMSG2 (("Child exited with retcode = %x\n",
		    ourstatus->value.integer));
	  win32_clear_inferiors ();
	  return pid_to_ptid (current_event.dwProcessId);
	case TARGET_WAITKIND_STOPPED:
	case TARGET_WAITKIND_LOADED:
	  OUTMSG2 (("Child Stopped with signal = %d \n",
		    ourstatus->value.sig));

	  regcache = get_thread_regcache (current_inferior, 1);
	  child_fetch_inferior_registers (regcache, -1);

	  if (ourstatus->kind == TARGET_WAITKIND_LOADED
	      && !server_waiting)
	    {
	      /* When gdb connects, we want to be stopped at the
		 initial breakpoint, not in some dll load event.  */
	      child_continue (DBG_CONTINUE, -1);
	      break;
	    }

	  /* We don't expose _LOADED events to gdbserver core.  See
	     the `dlls_changed' global.  */
	  if (ourstatus->kind == TARGET_WAITKIND_LOADED)
	    ourstatus->kind = TARGET_WAITKIND_STOPPED;

	  return debug_event_ptid (&current_event);
	default:
	  OUTMSG (("Ignoring unknown internal event, %d\n", ourstatus->kind));
	  /* fall-through */
	case TARGET_WAITKIND_SPURIOUS:
	case TARGET_WAITKIND_EXECD:
	  /* do nothing, just continue */
	  child_continue (DBG_CONTINUE, -1);
	  break;
	}
    }
}

struct process_info *
add_process (int pid, int attached)
{
  struct process_info *process;

  process = xcalloc (1, sizeof (*process));

  process->entry.id = pid_to_ptid (pid);
  process->attached = attached;

  add_inferior_to_list (&all_processes, &process->entry);

  return process;
}

int
pull_pid_from_list (struct inferior_list *list, unsigned long pid)
{
  struct inferior_list_entry *new_entry;

  new_entry = find_inferior_id (list, pid_to_ptid (pid));
  if (new_entry == NULL)
    return 0;
  else
    {
      remove_inferior (list, new_entry);
      free (new_entry);
      return 1;
    }
}

/* Wait for the inferior process to change state.
   STATUS will be filled in with a response code to send to GDB.
   Returns the signal which caused the process to stop. */
static ptid_t
win32_wait (ptid_t ptid, struct target_waitstatus *ourstatus, int options)
{
  struct regcache *regcache;

  if (cached_status.kind != TARGET_WAITKIND_IGNORE)
    {
      /* The core always does a wait after creating the inferior, and
	 do_initial_child_stuff already ran the inferior to the
	 initial breakpoint (or an exit, if creating the process
	 fails).  Report it now.  */
      *ourstatus = cached_status;
      cached_status.kind = TARGET_WAITKIND_IGNORE;
      return debug_event_ptid (&current_event);
    }

  while (1)
    {
      if (!get_child_debug_event (ourstatus))
	continue;

      switch (ourstatus->kind)
	{
	case TARGET_WAITKIND_EXITED:
	  OUTMSG2 (("Child exited with retcode = %x\n",
		    ourstatus->value.integer));
	  win32_clear_inferiors ();
	  return pid_to_ptid (current_event.dwProcessId);
	case TARGET_WAITKIND_STOPPED:
	case TARGET_WAITKIND_LOADED:
	  OUTMSG2 (("Child Stopped with signal = %d \n",
		    ourstatus->value.sig));

	  regcache = get_thread_regcache (current_thread, 1);
	  child_fetch_inferior_registers (regcache, -1);
	  return debug_event_ptid (&current_event);
	default:
	  OUTMSG (("Ignoring unknown internal event, %d\n", ourstatus->kind));
	  /* fall-through */
	case TARGET_WAITKIND_SPURIOUS:
	case TARGET_WAITKIND_EXECD:
	  /* do nothing, just continue */
	  child_continue (DBG_CONTINUE, -1);
	  break;
	}
    }
}

static int
nbsd_thread_proc_getregs (void *arg, int regset, int lwp, void *buf)
{
  struct nbsd_thread_proc_arg *a = (struct nbsd_thread_proc_arg *) arg; 
  struct regcache *cache = a->cache;
  struct target_ops *ops = a->ops;
  struct cleanup *old_chain;
  struct target_ops *beneath = find_target_beneath (ops);
  int ret;

  old_chain = save_inferior_ptid ();

  if (target_has_execution)
    {
      /* Fetching registers from a live process requires that
	 inferior_ptid is a LWP value rather than a thread value. */
      inferior_ptid = ptid_build (ptid_get_pid (main_ptid), lwp, 0);
      beneath->to_fetch_registers (beneath, cache, -1);
    }
  else
    {
      /* Fetching registers from a core process requires that
	 the PID value of inferior_ptid have the funky value that
	 the kernel drops rather than the real PID. Gross. */
      inferior_ptid = pid_to_ptid ((lwp << 16) | ptid_get_pid (main_ptid));
      beneath->to_fetch_registers (ops, cache, -1);
    }

  ret = 0;
  switch (regset)
    {
    case 0:
      fill_gregset (cache, (gregset_t *)buf, -1);
      break;
    case 1:
#ifdef HAVE_FPREGS
      fill_fpregset (cache, (fpregset_t *)buf, -1);
#endif
      break;
    default: /* XXX need to handle other reg sets: SSE, AltiVec, etc. */
      ret = TD_ERR_INVAL;
    }

  do_cleanups (old_chain);

  return ret;
}

static int
maybe_attach_thread (const td_thrhandle_t *th_p, td_thrinfo_t *ti_p,
		     int *counter)
{
  struct lwp_info *lwp;

  lwp = find_lwp_pid (pid_to_ptid (ti_p->ti_lid));
  if (lwp != NULL)
    return 1;

  if (!attach_thread (th_p, ti_p))
    return 0;

  if (counter != NULL)
    *counter += 1;

  return 1;
}

static void
fbsd_add_threads (pid_t pid)
{
  struct cleanup *cleanup;
  lwpid_t *lwps;
  int i, nlwps;

  gdb_assert (!in_thread_list (pid_to_ptid (pid)));
  nlwps = ptrace (PT_GETNUMLWPS, pid, NULL, 0);
  if (nlwps == -1)
    perror_with_name (("ptrace"));

  lwps = XCNEWVEC (lwpid_t, nlwps);
  cleanup = make_cleanup (xfree, lwps);

  nlwps = ptrace (PT_GETLWPLIST, pid, (caddr_t) lwps, nlwps);
  if (nlwps == -1)
    perror_with_name (("ptrace"));

  for (i = 0; i < nlwps; i++)
    {
      ptid_t ptid = ptid_build (pid, lwps[i], 0);

      if (!in_thread_list (ptid))
	{
#ifdef PT_LWP_EVENTS
	  struct ptrace_lwpinfo pl;

	  /* Don't add exited threads.  Note that this is only called
	     when attaching to a multi-threaded process.  */
	  if (ptrace (PT_LWPINFO, lwps[i], (caddr_t) &pl, sizeof pl) == -1)
	    perror_with_name (("ptrace"));
	  if (pl.pl_flags & PL_FLAG_EXITED)
	    continue;
#endif
	  if (debug_fbsd_lwp)
	    fprintf_unfiltered (gdb_stdlog,
				"FLWP: adding thread for LWP %u\n",
				lwps[i]);
	  add_thread (ptid);
	}
    }
  do_cleanups (cleanup);
}