adjkerntz.c revision 2910 
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 AUTHOR ``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 20 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#include <sys/param.h>
49#include <machine/cpu.h>
50#include <sys/sysctl.h>
51
52#include "pathnames.h"
53
54int main(argc, argv)
55	int argc;
56	char **argv;
57{
58	struct tm local, utc;
59	struct timeval tv, *stv;
60	struct timezone tz, *stz;
61	int kern_offset;
62	size_t len;
63	int mib[2];
64	/* Avoid time_t here, can be unsigned long or worse */
65	long offset, utcsec, localsec, diff;
66	time_t initial_sec, final_sec;
67	int ch, init = -1, verbose = 0;
68
69	while ((ch = getopt(argc, argv, "aiv")) != EOF)
70		switch((char)ch) {
71		case 'i':               /* initial call, save offset */
72			if (init != -1)
73				goto usage;
74			init = 1;
75			break;
76		case 'a':               /* adjustment call, use saved offset */
77			if (init != -1)
78				goto usage;
79			init = 0;
80			break;
81		case 'v':               /* verbose */
82			verbose = 1;
83			break;
84		default:
85		usage:
86			fprintf(stderr, "Usage:\n\
87\tadjkerntz -i [-v]\t(initial call from /etc/rc)\n\
88\tadjkerntz -a [-v]\t(adjustment call from crontab)\n");
89			return 2;
90		}
91	if (init == -1)
92		goto usage;
93
94	if (access(_PATH_CLOCK, F_OK))
95		return 0;
96
97	/* Restore saved offset */
98
99	mib[0] = CTL_MACHDEP;
100	mib[1] = CPU_ADJKERNTZ;
101	len = sizeof(kern_offset);
102	if (sysctl(mib, 2, &kern_offset, &len, NULL, 0) == -1) {
103		perror("sysctl(get_offset)");
104			return 1;
105		}
106
107/****** Critical section, do all things as fast as possible ******/
108
109	/* get local CMOS clock and possible kernel offset */
110	if (gettimeofday(&tv, &tz)) {
111		perror("gettimeofday");
112		return 1;
113	}
114
115	/* get the actual local timezone difference */
116	initial_sec = tv.tv_sec;
117	local = *localtime(&initial_sec);
118	utc = *gmtime(&initial_sec);
119	utc.tm_isdst = local.tm_isdst; /* Use current timezone for mktime(), */
120				       /* because it assumed local time */
121
122	/* calculate local CMOS diff from GMT */
123
124	utcsec = mktime(&utc);
125	localsec = mktime(&local);
126	if (utcsec == -1 || localsec == -1) {
127		/*
128		 * XXX user can only control local time, and it is
129		 * unacceptable to fail here for -i.  2:30 am in the
130		 * middle of the nonexistent hour means 3:30 am.
131		 */
132		fprintf(stderr,
133			"Nonexistent local time - try again in an hour\n");
134		return 1;
135	}
136	offset = utcsec - localsec;
137
138	/* correct the kerneltime for this diffs */
139	/* subtract kernel offset, if present, old offset too */
140
141	diff = offset - tz.tz_minuteswest * 60 - kern_offset;
142
143	if (diff != 0) {
144
145		/* Yet one step for final time */
146
147		final_sec = tv.tv_sec + diff;
148
149		/* get the actual local timezone difference */
150		local = *localtime(&final_sec);
151		utc = *gmtime(&final_sec);
152		utc.tm_isdst = local.tm_isdst; /* Use current timezone for mktime(), */
153					       /* because it assumed local time */
154
155		utcsec = mktime(&utc);
156		localsec = mktime(&local);
157		if (utcsec == -1 || localsec == -1) {
158			/*
159			 * XXX as above.  The user has even less control,
160			 * but perhaps we never get here.
161			 */
162			fprintf(stderr,
163		"Nonexistent (final) local time - try again in an hour\n");
164			return 1;
165		}
166		offset = utcsec - localsec;
167
168		/* correct the kerneltime for this diffs */
169		/* subtract kernel offset, if present, old offset too */
170
171		diff = offset - tz.tz_minuteswest * 60 - kern_offset;
172
173		if (diff != 0) {
174			tv.tv_sec += diff;
175			tv.tv_usec = 0;       /* we are restarting here... */
176			stv = &tv;
177		}
178		else
179			stv = NULL;
180	}
181	else
182		stv = NULL;
183
184	if (kern_offset != offset) {
185		kern_offset = offset;
186		mib[0] = CTL_MACHDEP;
187		mib[1] = CPU_ADJKERNTZ;
188		len = sizeof(kern_offset);
189		if (sysctl(mib, 2, NULL, NULL, &kern_offset, len) == -1) {
190			perror("sysctl(update_offset)");
191			return 1;
192		}
193	}
194
195	if (tz.tz_dsttime != 0 || tz.tz_minuteswest != 0) {
196		tz.tz_dsttime = tz.tz_minuteswest = 0;  /* zone info is garbage */
197		stz = &tz;
198	}
199	else
200		stz = NULL;
201
202	if (stz != NULL || stv != NULL) {
203		if (settimeofday(stv, stz)) {
204			perror("settimeofday");
205			return 1;
206		}
207	}
208
209/****** End of critical section ******/
210
211	if (verbose)
212		printf("Calculated zone offset difference: %ld seconds\n",
213		       diff);
214
215	return 0;
216}
217
218