/* Copyright (C) 2000-2018 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 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 <errno.h>

#include <fcntl.h>

#include <unistd.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <not-cancel.h>

static int itc_usable;

static int

has_cpuclock (void)

{

  if (__builtin_expect (itc_usable == 0, 0))

    {

      int newval = 1;

      int fd = __open_nocancel ("/proc/sal/itc_drift", O_RDONLY);

      if (__builtin_expect (fd != -1, 1))

	{

	  char buf[16];

	  /* We expect the file to contain a single digit followed by

	     a newline.  If the format changes we better not rely on

	     the file content.  */

	  if (__read_nocancel (fd, buf, sizeof buf) != 2

	      || buf[0] != '0' || buf[1] != '\n')

	    newval = -1;

	  __close_nocancel_nostatus (fd);

	}

      itc_usable = newval;

    }

  return itc_usable;

}