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