adjkerntz.c revision 867
1/* 2 * Copyright (C) 1993 by Andrew A. Chernov, Moscow, Russia. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27#ifndef lint 28char copyright[] = 29"@(#)Copyright (C) 1993 by Andrew A. Chernov, Moscow, Russia.\n\ 30 All rights reserved.\n"; 31#endif /* not lint */ 32 33/* 34 * Andrew A. Chernov <ache@astral.msk.su> Dec 15 1993 35 * 36 * Fix kernel time value if machine run wall CMOS clock 37 * (and /etc/wall_cmos_clock file present) 38 * using zoneinfo rules or direct TZ environment variable set. 39 * Use Joerg Wunsch idea for seconds accurate offset calculation 40 * with Garrett Wollman and Bruce Evans fixes. 41 * 42 */ 43#include <stdio.h> 44#include <stdlib.h> 45#include <unistd.h> 46#include <sys/stat.h> 47#include <sys/time.h> 48 49#include "pathnames.h" 50 51char storage[] = _PATH_OFFSET; 52 53int main(argc, argv) 54 int argc; 55 char **argv; 56{ 57 struct tm local, utc; 58 struct timeval tv, *stv; 59 struct timezone tz, *stz; 60 /* Avoid time_t here, can be unsigned long */ 61 long offset, oldoffset, utcsec, localsec, diff; 62 int ch, init = -1, verbose = 0; 63 FILE *f; 64 65 while ((ch = getopt(argc, argv, "aiv")) != EOF) 66 switch((char)ch) { 67 case 'i': /* initial call, save offset */ 68 if (init != -1) 69 goto usage; 70 init = 1; 71 break; 72 case 'a': /* adjustment call, use saved offset */ 73 if (init != -1) 74 goto usage; 75 init = 0; 76 break; 77 case 'v': /* verbose */ 78 verbose = 1; 79 break; 80 default: 81 usage: 82 fprintf(stderr, "Usage:\n\ 83\tadjkerntz -i [-v]\t(initial call from /etc/rc)\n\ 84\tadjkerntz -a [-v]\t(adjustment call from crontab)\n"); 85 return 2; 86 } 87 if (init == -1) 88 goto usage; 89 90 if (access(_PATH_CLOCK, F_OK)) 91 return 0; 92 93 /* Restore saved offset */ 94 95 if (!init) { 96 if ((f = fopen(storage, "r")) == NULL) { 97 perror(storage); 98 return 1; 99 } 100 if (fscanf(f, "%ld", &oldoffset) != 1) { 101 fprintf(stderr, "Incorrect offset in %s\n", storage); 102 return 1; 103 } 104 (void) fclose(f); 105 } 106 else 107 oldoffset = 0; 108 109/****** Critical section, do all things as fast as possible ******/ 110 111 /* get local CMOS clock and possible kernel offset */ 112 if (gettimeofday(&tv, &tz)) { 113 perror("gettimeofday"); 114 return 1; 115 } 116 117 /* get the actual local timezone difference */ 118 local = *localtime(&tv.tv_sec); 119 utc = *gmtime(&tv.tv_sec); 120 utc.tm_isdst = local.tm_isdst; /* Use current timezone for mktime(), */ 121 /* because it assumed local time */ 122 123 /* calculate local CMOS diff from GMT */ 124 125 utcsec = mktime(&utc); 126 localsec = mktime(&local); 127 if (utcsec == -1 || localsec == -1) { 128 fprintf(stderr, "Wrong hour to call\n"); 129 return 1; 130 } 131 offset = utcsec - localsec; 132 133 /* correct the kerneltime for this diffs */ 134 /* subtract kernel offset, if present, old offset too */ 135 136 diff = oldoffset + tz.tz_minuteswest * 60 - offset; 137 if (diff != 0) { 138 tv.tv_sec += diff; 139 tv.tv_usec = 0; /* we are restarting here... */ 140 stv = &tv; 141 } 142 else 143 stv = NULL; 144 145 if (tz.tz_dsttime != 0 || tz.tz_minuteswest != 0) { 146 tz.tz_dsttime = tz.tz_minuteswest = 0; /* zone info is garbage */ 147 stz = &tz; 148 } 149 else 150 stz = NULL; 151 152 if (stz != NULL || stv != NULL) { 153 if (settimeofday(stv, stz)) { 154 perror("settimeofday"); 155 return 1; 156 } 157 } 158 159/****** End of critical section ******/ 160 161 if (verbose) 162 printf("Calculated zone offset diffs: %ld seconds\n", diff); 163 164 if (offset != oldoffset) { 165 (void) umask(022); 166 /* Save offset for next calls from crontab */ 167 if ((f = fopen(storage, "w")) == NULL) { 168 perror(storage); 169 return 1; 170 } 171 fprintf(f, "%ld\n", offset); 172 if (fclose(f)) { 173 perror(storage); 174 return 1; 175 } 176 } 177 178 return 0; 179} 180 181