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clock_settime.c revision 1.5 
      1 /*	$NetBSD: clock_settime.c,v 1.5 2003/07/16 19:42:11 cb 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 "namespace.h"
     35 
     36 #include <sys/types.h>
     37 #include <sys/ioctl.h>
     38 #include <sys/syscall.h>
     39 #include <sys/systm.h>
     40 
     41 #include <errno.h>
     42 #include <fcntl.h>
     43 #include <paths.h>
     44 #include <string.h>
     45 #include <time.h>
     46 #include <unistd.h>
     47 
     48 #include <sys/clockctl.h>
     49 
     50 #ifdef __weak_alias
     51 __weak_alias(clock_settime,_clock_settime)
     52 #endif
     53 
     54 extern int __clockctl_fd;
     55 
     56 int
     57 clock_settime(clock_id, tp)
     58 	clockid_t clock_id;
     59 	const struct timespec *tp;
     60 {
     61 	struct sys_clock_settime_args args;
     62 	int error;
     63 	quad_t q;
     64 	int rv;
     65 
     66 	/*
     67 	 * if __clockctl_fd == -1, then this is not our first time,
     68 	 * and we know root is the calling user. We use the system call
     69 	 */
     70 	if (__clockctl_fd == -1) {
     71 try_syscall:
     72 		q = __syscall((quad_t)SYS_clock_settime, clock_id, tp);
     73 		if (/* LINTED constant */ sizeof (quad_t) == sizeof (register_t)
     74 		    || /* LINTED constant */ BYTE_ORDER == LITTLE_ENDIAN)
     75 			rv = (int)q;
     76 		else
     77 			rv = (int)((u_quad_t)q >> 32);
     78 
     79 		/*
     80 		 * If credentials changed from root to an unprivilegied
     81 		 * user, and we already had __clockctl_fd = -1, then we
     82 		 * tried the system call as a non root user, it failed
     83 		 * with EPERM, and we will try clockctl.
     84 		 */
     85 		if (rv != -1 || errno != EPERM)
     86 			return rv;
     87 		__clockctl_fd = -2;
     88 	}
     89 
     90 	/*
     91 	 * If __clockctl_fd = -2 then this is our first time here,
     92 	 * or credentials have changed (the calling process dropped root
     93 	 * root privilege). Check if root is the calling user. If it is,
     94 	 * we try the system call, if it is not, we try clockctl.
     95 	 */
     96 	if (__clockctl_fd == -2) {
     97 		/*
     98 		 * Root always uses the syscall
     99 		 */
    100 		if (geteuid() == 0) {
    101 			__clockctl_fd = -1;
    102 			goto try_syscall;
    103 		}
    104 
    105 		/*
    106 		 * If this fails, it means that we are not root
    107 		 * and we cannot open clockctl. This is a failure.
    108 		 */
    109 		__clockctl_fd = open(_PATH_CLOCKCTL, O_WRONLY, 0);
    110 		if (__clockctl_fd == -1)
    111 			return -1;
    112 		(void) fcntl(__clockctl_fd, F_SETFD, FD_CLOEXEC);
    113 	}
    114 
    115 	/*
    116 	 * If __clockctl_fd >=0, clockctl has already been open
    117 	 * and used, so we carry on using it.
    118 	 */
    119 	SCARG(&args, clock_id) = clock_id;
    120 	SCARG(&args, tp) = tp;
    121 	error = ioctl(__clockctl_fd, CLOCKCTL_CLOCK_SETTIME, &args);
    122 	return error;
    123 
    124 }
    125