/* Copyright (C) 1992, 1993, 1994, 1995, 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <hurd.h>
#include <hurd/signal.h>

/* Run signals handlers on the stack specified by SS (if not NULL).
   If OSS is not NULL, it is filled in with the old signal stack status.  */
/* XXX should be __sigaltstack ? */
int
sigaltstack (ss, oss)
     const struct sigaltstack *argss;
     struct sigaltstack *oss;
{
  struct hurd_sigstate *s;
  struct sigaltstack ss, old;

  /* Fault before taking any locks.  */
  if (argss != NULL)
    ss = *argss;
  if (oss != NULL)
    *(volatile struct sigaltstack *) oss = *oss;

  s = _hurd_self_sigstate ();
  __spin_lock (&s->lock);

  if (argss != NULL &&
      (ss.ss_flags & SA_DISABLE) && (s->sigaltstack.ss_flags & SA_ONSTACK))
    {
      /* Can't disable a stack that is in use.  */
      __spin_unlock (&s->lock);
      errno = EINVAL;
      return -1;
    }

  old = s->sigaltstack;

  if (argss != NULL)
    s->sigaltstack = ss;

  __spin_unlock (&s->lock);

  if (oss != NULL)
    *oss = old;

  return 0;
}