getpagesizes.c revision 197331 
1/*-
2 * Copyright (c) 2009 Alan L. Cox <alc@cs.rice.edu>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/lib/libc/gen/getpagesizes.c 197331 2009-09-19 18:01:32Z alc $");
29
30#include <sys/param.h>
31#include <sys/mman.h>
32#include <sys/sysctl.h>
33
34#include <errno.h>
35
36/*
37 * Retrieves page size information from the system.  Specifically, returns the
38 * number of distinct page sizes that are supported by the system, if
39 * "pagesize" is NULL and "nelem" is 0.  Otherwise, assigns up to "nelem" of
40 * the system-supported page sizes to consecutive elements of the array
41 * referenced by "pagesize", and returns the number of such page sizes that it
42 * assigned to the array.  These page sizes are expressed in bytes.
43 *
44 * The implementation of this function does not directly or indirectly call
45 * malloc(3) or any other dynamic memory allocator that may itself call this
46 * function.
47 */
48int
49getpagesizes(size_t pagesize[], int nelem)
50{
51	static u_long ps[MAXPAGESIZES];
52	static int nops;
53	size_t size;
54	int i;
55
56	if (nelem < 0 || (nelem > 0 && pagesize == NULL)) {
57		errno = EINVAL;
58		return (-1);
59	}
60	/* Cache the result of the sysctl(2). */
61	if (nops == 0) {
62		size = sizeof(ps);
63		if (sysctlbyname("hw.pagesizes", ps, &size, NULL, 0) == -1)
64			return (-1);
65		/* Count the number of page sizes that are supported. */
66		nops = size / sizeof(ps[0]);
67		while (nops > 0 && ps[nops - 1] == 0)
68			nops--;
69	}
70	if (pagesize == NULL)
71		return (nops);
72	/* Return up to "nelem" page sizes from the cached result. */
73	if (nelem > nops)
74		nelem = nops;
75	for (i = 0; i < nelem; i++)
76		pagesize[i] = ps[i];
77	return (nelem);
78}
79