/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2007 Peter Wemm
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: releng/12.0/lib/libc/gen/__getosreldate.c 326193 2017-11-25 17:12:48Z pfg $");

#include <sys/param.h>
#include <sys/sysctl.h>
#include <errno.h>
#include <link.h>
#include "libc_private.h"

/*
 * This is private to libc.  It is intended for wrapping syscall stubs in order
 * to avoid having to put SIGSYS signal handlers in place to test for presence
 * of new syscalls.  This caches the result in order to be as quick as possible.
 *
 * Use getosreldate(3) for public use as it respects the $OSVERSION environment
 * variable.
 */

int
__getosreldate(void)
{
	static int osreldate;
	size_t len;
	int oid[2];
	int error, osrel;

	if (osreldate != 0)
		return (osreldate);

	error = _elf_aux_info(AT_OSRELDATE, &osreldate, sizeof(osreldate));
	if (error == 0 && osreldate != 0)
		return (osreldate);

	oid[0] = CTL_KERN;
	oid[1] = KERN_OSRELDATE;
	osrel = 0;
	len = sizeof(osrel);
	error = sysctl(oid, 2, &osrel, &len, NULL, 0);
	if (error == 0 && osrel > 0 && len == sizeof(osrel))
		osreldate = osrel;
	return (osreldate);
}
