1 /* $NetBSD: ntp_adjtime.c,v 1.7 2006/03/09 23:44:43 christos 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 1.7 2006/03/09 23:44:43 christos 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 50 #include <sys/clockctl.h> 51 52 #include <fcntl.h> 53 #include <paths.h> 54 #include <string.h> 55 #include <unistd.h> 56 57 #ifdef __weak_alias 58 __weak_alias(ntp_adjtime,_ntp_adjtime) 59 #endif 60 61 extern int __clockctl_fd; 62 63 int 64 ntp_adjtime(tp) 65 struct timex *tp; 66 { 67 struct clockctl_ntp_adjtime args; 68 int error; 69 quad_t q; 70 int rv; 71 72 /* 73 * if __clockctl_fd == -1, then this is not our first time, 74 * and we know root is the calling user. We use the system call 75 */ 76 if (__clockctl_fd == -1) { 77 try_syscall: 78 q = __syscall((quad_t)SYS_ntp_adjtime, tp); 79 if (/* LINTED constant */ sizeof (quad_t) == sizeof (register_t) 80 || /* LINTED constant */ BYTE_ORDER == LITTLE_ENDIAN) 81 rv = (int)q; 82 else 83 rv = (int)((u_quad_t)q >> 32); 84 85 /* 86 * If credentials changed from root to an unprivilegied 87 * user, and we already had __clockctl_fd = -1, then we 88 * tried the system call as a non root user, it failed 89 * with EPERM, and we will try clockctl. 90 */ 91 if (rv != -1 || errno != EPERM) 92 return rv; 93 __clockctl_fd = -2; 94 } 95 96 /* 97 * If __clockctl_fd = -2 then this is our first time here, 98 * or credentials have changed (the calling process dropped root 99 * root privilege). Check if root is the calling user. If it is, 100 * we try the system call, if it is not, we try clockctl. 101 */ 102 if (__clockctl_fd == -2) { 103 /* 104 * Root always uses the syscall 105 */ 106 if (geteuid() == 0) { 107 __clockctl_fd = -1; 108 goto try_syscall; 109 } 110 111 /* 112 * If this fails, it means that we are not root 113 * and we cannot open clockctl. This is a failure. 114 */ 115 __clockctl_fd = open(_PATH_CLOCKCTL, O_WRONLY, 0); 116 if (__clockctl_fd == -1) 117 return -1; 118 (void) fcntl(__clockctl_fd, F_SETFD, FD_CLOEXEC); 119 } 120 121 /* 122 * If __clockctl_fd >=0, clockctl has already been open 123 * and used, so we carry on using it. 124 */ 125 args.tp = tp; 126 error = ioctl(__clockctl_fd, CLOCKCTL_NTP_ADJTIME, &args); 127 128 /* 129 * There is no way to get retval set through ioctl(), hence we 130 * have to handle it here, using args.retval 131 */ 132 if (error == 0) { 133 rv = (int)args.retval; 134 return rv; 135 } 136 return error; 137 138 } 139