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ntp_adjtime.c revision 1.6 
      1 /*	$NetBSD: ntp_adjtime.c,v 1.6 2005/06/12 05:21:28 lukem Exp $ */
      2 
      3 /*
      4  * Copyright (c) 2001 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Emmanuel Dreyfus.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     27  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #include <sys/cdefs.h>
     35 #if defined(LIBC_SCCS) && !defined(lint)
     36 __RCSID("$NetBSD: ntp_adjtime.c,v 1.6 2005/06/12 05:21:28 lukem Exp $");
     37 #endif /* LIBC_SCCS and not lint */
     38 
     39 #include "namespace.h"
     40 #include <errno.h>
     41 #include <fcntl.h>
     42 #include <paths.h>
     43 #include <unistd.h>
     44 #include <sys/types.h>
     45 #include <sys/time.h>
     46 #include <sys/timex.h>
     47 #include <sys/ioctl.h>
     48 #include <sys/syscall.h>
     49 #include <sys/systm.h>
     50 
     51 #include <sys/clockctl.h>
     52 
     53 #include <fcntl.h>
     54 #include <paths.h>
     55 #include <string.h>
     56 #include <unistd.h>
     57 
     58 #ifdef __weak_alias
     59 __weak_alias(ntp_adjtime,_ntp_adjtime)
     60 #endif
     61 
     62 extern int __clockctl_fd;
     63 
     64 int
     65 ntp_adjtime(tp)
     66 	struct timex *tp;
     67 {
     68 	struct clockctl_ntp_adjtime_args args;
     69 	int error;
     70 	quad_t q;
     71 	int rv;
     72 
     73 	/*
     74 	 * if __clockctl_fd == -1, then this is not our first time,
     75 	 * and we know root is the calling user. We use the system call
     76 	 */
     77 	if (__clockctl_fd == -1) {
     78 try_syscall:
     79 		q = __syscall((quad_t)SYS_ntp_adjtime, tp);
     80 		if (/* LINTED constant */ sizeof (quad_t) == sizeof (register_t)
     81 		    || /* LINTED constant */ BYTE_ORDER == LITTLE_ENDIAN)
     82 			rv = (int)q;
     83 		else
     84 			rv = (int)((u_quad_t)q >> 32);
     85 
     86 		/*
     87 		 * If credentials changed from root to an unprivilegied
     88 		 * user, and we already had __clockctl_fd = -1, then we
     89 		 * tried the system call as a non root user, it failed
     90 		 * with EPERM, and we will try clockctl.
     91 		 */
     92 		if (rv != -1 || errno != EPERM)
     93 			return rv;
     94 		__clockctl_fd = -2;
     95 	}
     96 
     97 	/*
     98 	 * If __clockctl_fd = -2 then this is our first time here,
     99 	 * or credentials have changed (the calling process dropped root
    100 	 * root privilege). Check if root is the calling user. If it is,
    101 	 * we try the system call, if it is not, we try clockctl.
    102 	 */
    103 	if (__clockctl_fd == -2) {
    104 		/*
    105 		 * Root always uses the syscall
    106 		 */
    107 		if (geteuid() == 0) {
    108 			__clockctl_fd = -1;
    109 			goto try_syscall;
    110 		}
    111 
    112 		/*
    113 		 * If this fails, it means that we are not root
    114 		 * and we cannot open clockctl. This is a failure.
    115 		 */
    116 		__clockctl_fd = open(_PATH_CLOCKCTL, O_WRONLY, 0);
    117 		if (__clockctl_fd == -1)
    118 			return -1;
    119 		(void) fcntl(__clockctl_fd, F_SETFD, FD_CLOEXEC);
    120 	}
    121 
    122 	/*
    123 	 * If __clockctl_fd >=0, clockctl has already been open
    124 	 * and used, so we carry on using it.
    125 	 */
    126 	SCARG(&args.uas, tp) = tp;
    127 	error = ioctl(__clockctl_fd, CLOCKCTL_NTP_ADJTIME, &args);
    128 
    129 	/*
    130 	 * There is no way to get retval set through ioctl(), hence we
    131 	 * have to handle it here, using args.retval
    132 	 */
    133 	if (error == 0) {
    134 		rv = (int)args.retval;
    135 		return rv;
    136 	}
    137 	return error;
    138 
    139 }
    140