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Add a feature_present(3) function which checks to see if a named kernel

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feature is present by checking the kern.features sysctl MIB.

MFC after:	1 week
This commit is contained in:
John Baldwin 2008-01-10 22:11:21 +00:00
parent d92909c1d4
commit ce309a2f26
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=175220
4 changed files with 138 additions and 2 deletions
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1
include/unistd.h
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@ -480,6 +480,7 @@ int des_setkey(const char *key);
void endusershell(void);
int exect(const char *, char * const *, char * const *);
int execvP(const char *, const char *, char * const *);
int feature_present(const char *);
char *fflagstostr(u_long);
int getdomainname(char *, int);
int getgrouplist(const char *, gid_t, gid_t *, int *);

5
lib/libc/gen/Makefile.inc
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@ -10,7 +10,7 @@ SRCS+= __getosreldate.c __xuname.c \
clock.c closedir.c confstr.c \
crypt.c ctermid.c daemon.c devname.c dirname.c disklabel.c \
dlfcn.c dlfunc.c drand48.c erand48.c err.c errlst.c errno.c \
exec.c fmtcheck.c fmtmsg.c fnmatch.c \
exec.c feature_present.c fmtcheck.c fmtmsg.c fnmatch.c \
fpclassify.c frexp.c fstab.c ftok.c fts.c ftw.c \
getbootfile.c getbsize.c \
getcap.c getcwd.c getdomainname.c getgrent.c getgrouplist.c \
@ -45,7 +45,8 @@ MAN+= alarm.3 arc4random.3 \
basename.3 check_utility_compat.3 clock.3 \
confstr.3 ctermid.3 daemon.3 devname.3 directory.3 dirname.3 \
dladdr.3 dlinfo.3 dllockinit.3 dlopen.3 \
err.3 exec.3 fmtcheck.3 fmtmsg.3 fnmatch.3 fpclassify.3 frexp.3 \
err.3 exec.3 \
feature_present.3 fmtcheck.3 fmtmsg.3 fnmatch.3 fpclassify.3 frexp.3 \
ftok.3 fts.3 ftw.3 \
getbootfile.3 getbsize.3 getcap.3 getcontext.3 getcwd.3 \
getdiskbyname.3 getdomainname.3 getfsent.3 \

72
lib/libc/gen/feature_present.3 Normal file
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@ -0,0 +1,72 @@
.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd January 8, 2008
.Dt feature_present 3
.Os
.Sh NAME
.Nm feature_present
.Nd query presence of a kernel feature
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn feature_present "const char *feature"
.Sh DESCRIPTION
The
.Fn feature_present
function provides a method for an application to determine if a specific
kernel feature is present in the currently running kernel.
The
.Fa feature
argument specifies the name of the feature to check.
The
.Fn feature_present
function will return 1 if the specified feature is present,
otherwise it will return 0.
If the
.Fn feature_present
function is not able to determine the presence of
.Fa feature
due to an internal error it will return 0.
.Sh RETURN VALUES
If
.Fa feature
is present then 1 is returned;
otherwise 0 is returned.
.Sh SEE ALSO
.Xr sysconf 3 ,
.Xr sysctl 3
.Sh HISTORY
The
.Fn feature_present
function first appeared in
.Fx 8.0 .

62
lib/libc/gen/feature_present.c Normal file
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@ -0,0 +1,62 @@
/*-
* 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);
}