/* Validate a thread handle.
   Copyright (C) 1999-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 1999.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include "thread_dbP.h"
#include <stdbool.h>

static td_err_e
check_thread_list (const td_thrhandle_t *th, psaddr_t head, bool *uninit)
{
  td_err_e err;
  psaddr_t next, ofs;

  err = DB_GET_FIELD (next, th->th_ta_p, head, list_t, next, 0);
  if (err == TD_OK)
    {
      if (next == 0)
	{
	  *uninit = true;
	  return TD_NOTHR;
	}
      err = DB_GET_FIELD_ADDRESS (ofs, th->th_ta_p, 0, pthread, list, 0);
    }

  while (err == TD_OK)
    {
      if (next == head)
	return TD_NOTHR;

      if (next - (ofs - (psaddr_t) 0) == th->th_unique)
	return TD_OK;

      err = DB_GET_FIELD (next, th->th_ta_p, next, list_t, next, 0);
    }

  return err;
}


td_err_e
td_thr_validate (const td_thrhandle_t *th)
{
  td_err_e err;
  psaddr_t list;

  LOG ("td_thr_validate");

  /* First check the list with threads using user allocated stacks.  */
  bool uninit = false;
  err = DB_GET_SYMBOL (list, th->th_ta_p, __stack_user);
  if (err == TD_OK)
    err = check_thread_list (th, list, &uninit);

  /* If our thread is not on this list search the list with stack
     using implementation allocated stacks.  */
  if (err == TD_NOTHR)
    {
      err = DB_GET_SYMBOL (list, th->th_ta_p, stack_used);
      if (err == TD_OK)
	err = check_thread_list (th, list, &uninit);

      if (err == TD_NOTHR && uninit && th->th_unique == 0)
	/* __pthread_initialize_minimal has not run yet.
	   There is only the special case thread handle.  */
	err = TD_OK;
    }

  if (err == TD_OK)
    {
      /* Verify that this is not a stale element in a fork child.  */
      pid_t match_pid = ps_getpid (th->th_ta_p->ph);
      psaddr_t pid;
      err = DB_GET_FIELD (pid, th->th_ta_p, th->th_unique, pthread, pid, 0);
      if (err == TD_OK && (pid_t) (uintptr_t) pid < 0)
	{
	  /* This was a thread that was about to fork, or it is the new sole
	     thread in a fork child.  In the latter case, its tid was stored
	     via CLONE_CHILD_SETTID and so is already the proper child PID.  */
	  if (-(pid_t) (uintptr_t) pid == match_pid)
	    /* It is about to do a fork, but is really still the parent PID.  */
	    pid = (psaddr_t) (uintptr_t) match_pid;
	  else
	    /* It must be a fork child, whose new PID is in the tid field.  */
	    err = DB_GET_FIELD (pid, th->th_ta_p, th->th_unique,
				pthread, tid, 0);
	}
      if (err == TD_OK && (pid_t) (uintptr_t) pid != match_pid)
	err = TD_NOTHR;
    }

  return err;
}