1 /*- 2 * Copyright (c) 2008 Yahoo!, Inc. 3 * All rights reserved. 4 * Written by: John Baldwin <[email protected]> 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the author nor the names of any co-contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 #ifndef FSTACK 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 #else 35 #define _GNU_SOURCE 36 #endif 37 38 #include <sys/types.h> 39 #include <sys/sysctl.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <unistd.h> 43 44 #include "compat.h" 45 46 /* 47 * Returns true if the named feature is present in the currently 48 * running kernel. A feature's presence is indicated by an integer 49 * sysctl node called kern.feature.<feature> that is non-zero. 50 */ 51 int 52 feature_present(const char *feature) 53 { 54 char *mib; 55 size_t len; 56 int i; 57 58 if (asprintf(&mib, "kern.features.%s", feature) < 0) 59 return (0); 60 len = sizeof(i); 61 if (sysctlbyname(mib, &i, &len, NULL, 0) < 0) { 62 free(mib); 63 return (0); 64 } 65 free(mib); 66 if (len != sizeof(i)) 67 return (0); 68 return (i != 0); 69 } 70