freebsd-dev/lib/libc/gen/feature_present.c
John Baldwin ce309a2f26 Add a feature_present(3) function which checks to see if a named kernel
feature is present by checking the kern.features sysctl MIB.

MFC after:	1 week
2008-01-10 22:11:21 +00:00

63 lines
2.2 KiB
C

/*-
* Copyright (c) 2008 Yahoo!, Inc.
* All rights reserved.
* Written by: John Baldwin <jhb@FreeBSD.org>
*
* 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 author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* 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("$FreeBSD$");
#include <sys/types.h>
#include <sys/sysctl.h>
#include <stdio.h>
#include <stdlib.h>
/*
* Returns true if the named feature is present in the currently
* running kernel. A feature's presence is indicated by an integer
* sysctl node called kern.feature.<feature> that is non-zero.
*/
int
feature_present(const char *feature)
{
char *mib;
size_t len;
int i;
if (asprintf(&mib, "kern.features.%s", feature) < 0)
return (0);
len = sizeof(i);
if (sysctlbyname(mib, &i, &len, NULL, 0) < 0) {
free(mib);
return (0);
}
free(mib);
if (len != sizeof(i))
return (0);
return (i != 0);
}