freebsd-dev/lib/libc/gen/getpagesize.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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>
__SCCSID("@(#)getpagesize.c	8.1 (Berkeley) 6/4/93");
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/sysctl.h>

#include <errno.h>
#include <link.h>
#include <unistd.h>

#include "libc_private.h"

/*
 * This is unlikely to change over the running time of any
 * program, so we cache the result to save some syscalls.
 *
 * NB: This function may be called from malloc(3) at initialization
 * NB: so must not result in a malloc(3) related call!
 */

int
getpagesize(void)
{
	int mib[2];
	static int value;
	size_t size;
	int error;

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

	error = _elf_aux_info(AT_PAGESZ, &value, sizeof(value));
	if (error == 0 && value != 0)
		return (value);

	mib[0] = CTL_HW;
	mib[1] = HW_PAGESIZE;
	size = sizeof value;
	if (sysctl(mib, nitems(mib), &value, &size, NULL, 0) == -1)
		return (PAGE_SIZE);

	return (value);
}