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1/* vi: set sw=4 ts=4: */
2/*
3 * Mini hwclock implementation for busybox
4 *
5 * Copyright (C) 2002 Robert Griebl <griebl@gmx.de>
6 *
7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
8 */
9//config:config HWCLOCK
10//config: bool "hwclock"
11//config: default y
12//config: select PLATFORM_LINUX
13//config: help
14//config: The hwclock utility is used to read and set the hardware clock
15//config: on a system. This is primarily used to set the current time on
16//config: shutdown in the hardware clock, so the hardware will keep the
17//config: correct time when Linux is _not_ running.
18//config:
19//config:config FEATURE_HWCLOCK_LONG_OPTIONS
20//config: bool "Support long options (--hctosys,...)"
21//config: default y
22//config: depends on HWCLOCK && LONG_OPTS
23//config: help
24//config: By default, the hwclock utility only uses short options. If you
25//config: are overly fond of its long options, such as --hctosys, --utc, etc)
26//config: then enable this option.
27//config:
28//config:config FEATURE_HWCLOCK_ADJTIME_FHS
29//config: bool "Use FHS /var/lib/hwclock/adjtime"
30//config: default n # util-linux-ng in Fedora 13 still uses /etc/adjtime
31//config: depends on HWCLOCK
32//config: help
33//config: Starting with FHS 2.3, the adjtime state file is supposed to exist
34//config: at /var/lib/hwclock/adjtime instead of /etc/adjtime. If you wish
35//config: to use the FHS behavior, answer Y here, otherwise answer N for the
36//config: classic /etc/adjtime path.
37//config:
38//config: pathname.com/fhs/pub/fhs-2.3.html#VARLIBHWCLOCKSTATEDIRECTORYFORHWCLO
39
40//applet:IF_HWCLOCK(APPLET(hwclock, BB_DIR_SBIN, BB_SUID_DROP))
41
42//kbuild:lib-$(CONFIG_HWCLOCK) += hwclock.o
43
44#include "libbb.h"
45/* After libbb.h, since it needs sys/types.h on some systems */
46#include <sys/utsname.h>
47#include "rtc_.h"
48
49/* diff code is disabled: it's not sys/hw clock diff, it's some useless
50 * "time between hwclock was started and we saw CMOS tick" quantity.
51 * It's useless since hwclock is started at a random moment,
52 * thus the quantity is also random, useless. Showing 0.000000 does not
53 * deprive us from any useful info.
54 *
55 * SHOW_HWCLOCK_DIFF code in this file shows the difference between system
56 * and hw clock. It is useful, but not compatible with standard hwclock.
57 * Thus disabled.
58 */
59#define SHOW_HWCLOCK_DIFF 0
60
61
62#if !SHOW_HWCLOCK_DIFF
63# define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc)
64#endif
65static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc)
66{
67 struct tm tm_time;
68 int fd;
69
70 fd = rtc_xopen(pp_rtcname, O_RDONLY);
71
72 rtc_read_tm(&tm_time, fd);
73
74#if SHOW_HWCLOCK_DIFF
75 {
76 int before = tm_time.tm_sec;
77 while (1) {
78 rtc_read_tm(&tm_time, fd);
79 gettimeofday(sys_tv, NULL);
80 if (before != (int)tm_time.tm_sec)
81 break;
82 }
83 }
84#endif
85
86 if (ENABLE_FEATURE_CLEAN_UP)
87 close(fd);
88
89 return rtc_tm2time(&tm_time, utc);
90}
91
92static void show_clock(const char **pp_rtcname, int utc)
93{
94#if SHOW_HWCLOCK_DIFF
95 struct timeval sys_tv;
96#endif
97 time_t t = read_rtc(pp_rtcname, &sys_tv, utc);
98
99#if ENABLE_LOCALE_SUPPORT
100 /* Standard hwclock uses locale-specific output format */
101 char cp[64];
102 struct tm *ptm = localtime(&t);
103 strftime(cp, sizeof(cp), "%c", ptm);
104#else
105 char *cp = ctime(&t);
106 chomp(cp);
107#endif
108
109#if !SHOW_HWCLOCK_DIFF
110 printf("%s 0.000000 seconds\n", cp);
111#else
112 {
113 long diff = sys_tv.tv_sec - t;
114 if (diff < 0 /*&& tv.tv_usec != 0*/) {
115 /* Why we need diff++? */
116 /* diff >= 0 is ok: | diff < 0, can't just use tv.tv_usec: */
117 /* 45.520820 | 43.520820 */
118 /* - 44.000000 | - 45.000000 */
119 /* = 1.520820 | = -1.479180, not -2.520820! */
120 diff++;
121 /* Should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
122 sys_tv.tv_usec = 999999 - sys_tv.tv_usec;
123 }
124 printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec);
125 }
126#endif
127}
128
129static void to_sys_clock(const char **pp_rtcname, int utc)
130{
131 struct timeval tv;
132 struct timezone tz;
133
134 tz.tz_minuteswest = timezone/60;
135 /* ^^^ used to also subtract 60*daylight, but it's wrong:
136 * daylight!=0 means "this timezone has some DST
137 * during the year", not "DST is in effect now".
138 */
139 tz.tz_dsttime = 0;
140
141 tv.tv_sec = read_rtc(pp_rtcname, NULL, utc);
142 tv.tv_usec = 0;
143 if (settimeofday(&tv, &tz))
144 bb_perror_msg_and_die("settimeofday");
145}
146
147static void from_sys_clock(const char **pp_rtcname, int utc)
148{
149#if 1
150 struct timeval tv;
151 struct tm tm_time;
152 int rtc;
153
154 rtc = rtc_xopen(pp_rtcname, O_WRONLY);
155 gettimeofday(&tv, NULL);
156 /* Prepare tm_time */
157 if (sizeof(time_t) == sizeof(tv.tv_sec)) {
158 if (utc)
159 gmtime_r((time_t*)&tv.tv_sec, &tm_time);
160 else
161 localtime_r((time_t*)&tv.tv_sec, &tm_time);
162 } else {
163 time_t t = tv.tv_sec;
164 if (utc)
165 gmtime_r(&t, &tm_time);
166 else
167 localtime_r(&t, &tm_time);
168 }
169#else
170/* Bloated code which tries to set hw clock with better precision.
171 * On x86, even though code does set hw clock within <1ms of exact
172 * whole seconds, apparently hw clock (at least on some machines)
173 * doesn't reset internal fractional seconds to 0,
174 * making all this a pointless excercise.
175 */
176 /* If we see that we are N usec away from whole second,
177 * we'll sleep for N-ADJ usecs. ADJ corrects for the fact
178 * that CPU is not infinitely fast.
179 * On infinitely fast CPU, next wakeup would be
180 * on (exactly_next_whole_second - ADJ). On real CPUs,
181 * this difference between current time and whole second
182 * is less than ADJ (assuming system isn't heavily loaded).
183 */
184 /* Small value of 256us gives very precise sync for 2+ GHz CPUs.
185 * Slower CPUs will fail to sync and will go to bigger
186 * ADJ values. qemu-emulated armv4tl with ~100 MHz
187 * performance ends up using ADJ ~= 4*1024 and it takes
188 * 2+ secs (2 tries with successively larger ADJ)
189 * to sync. Even straced one on the same qemu (very slow)
190 * takes only 4 tries.
191 */
192#define TWEAK_USEC 256
193 unsigned adj = TWEAK_USEC;
194 struct tm tm_time;
195 struct timeval tv;
196 int rtc = rtc_xopen(pp_rtcname, O_WRONLY);
197
198 /* Try to catch the moment when whole second is close */
199 while (1) {
200 unsigned rem_usec;
201 time_t t;
202
203 gettimeofday(&tv, NULL);
204
205 t = tv.tv_sec;
206 rem_usec = 1000000 - tv.tv_usec;
207 if (rem_usec < adj) {
208 /* Close enough */
209 small_rem:
210 t++;
211 }
212
213 /* Prepare tm_time from t */
214 if (utc)
215 gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
216 else
217 localtime_r(&t, &tm_time); /* same */
218
219 if (adj >= 32*1024) {
220 break; /* 32 ms diff and still no luck?? give up trying to sync */
221 }
222
223 /* gmtime/localtime took some time, re-get cur time */
224 gettimeofday(&tv, NULL);
225
226 if (tv.tv_sec < t /* we are still in old second */
227 || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
228 ) {
229 break; /* good, we are in sync! */
230 }
231
232 rem_usec = 1000000 - tv.tv_usec;
233 if (rem_usec < adj) {
234 t = tv.tv_sec;
235 goto small_rem; /* already close to next sec, don't sleep */
236 }
237
238 /* Try to sync up by sleeping */
239 usleep(rem_usec - adj);
240
241 /* Jump to 1ms diff, then increase fast (x2): EVERY loop
242 * takes ~1 sec, people won't like slowly converging code here!
243 */
244 //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
245 if (adj < 512)
246 adj = 512;
247 /* ... and if last "overshoot" does not look insanely big,
248 * just use it as adj increment. This makes convergence faster.
249 */
250 if (tv.tv_usec < adj * 8) {
251 adj += tv.tv_usec;
252 continue;
253 }
254 adj *= 2;
255 }
256 /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
257 * Look for a value which makes tv_usec close to 999999 or 0.
258 * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
259 */
260 //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
261#endif
262
263 tm_time.tm_isdst = 0;
264 xioctl(rtc, RTC_SET_TIME, &tm_time);
265
266 if (ENABLE_FEATURE_CLEAN_UP)
267 close(rtc);
268}
269
270/*
271 * At system boot, kernel may set system time from RTC,
272 * but it knows nothing about timezones. If RTC is in local time,
273 * then system time is wrong - it is offset by timezone.
274 * This option corrects system time if RTC is in local time,
275 * and (always) sets in-kernel timezone.
276 *
277 * This is an alternate option to --hctosys that does not read the
278 * hardware clock.
279 */
280static void set_system_clock_timezone(int utc)
281{
282 struct timeval tv;
283 struct tm *broken;
284 struct timezone tz;
285
286 gettimeofday(&tv, NULL);
287 broken = localtime(&tv.tv_sec);
288 tz.tz_minuteswest = timezone / 60;
289 if (broken->tm_isdst > 0)
290 tz.tz_minuteswest -= 60;
291 tz.tz_dsttime = 0;
292 gettimeofday(&tv, NULL);
293 if (!utc)
294 tv.tv_sec += tz.tz_minuteswest * 60;
295 if (settimeofday(&tv, &tz))
296 bb_perror_msg_and_die("settimeofday");
297}
298
299//usage:#define hwclock_trivial_usage
300//usage: IF_FEATURE_HWCLOCK_LONG_OPTIONS(
301//usage: "[-r|--show] [-s|--hctosys] [-w|--systohc] [-t|--systz]"
302//usage: " [-l|--localtime] [-u|--utc]"
303//usage: " [-f|--rtc FILE]"
304//usage: )
305//usage: IF_NOT_FEATURE_HWCLOCK_LONG_OPTIONS(
306//usage: "[-r] [-s] [-w] [-t] [-l] [-u] [-f FILE]"
307//usage: )
308//usage:#define hwclock_full_usage "\n\n"
309//usage: "Query and set hardware clock (RTC)\n"
310//usage: "\n -r Show hardware clock time"
311//usage: "\n -s Set system time from hardware clock"
312//usage: "\n -w Set hardware clock from system time"
313//usage: "\n -t Set in-kernel timezone, correct system time"
314//usage: "\n if hardware clock is in local time"
315//usage: "\n -u Assume hardware clock is kept in UTC"
316//usage: "\n -l Assume hardware clock is kept in local time"
317//usage: "\n -f FILE Use specified device (e.g. /dev/rtc2)"
318
319#define HWCLOCK_OPT_LOCALTIME 0x01
320#define HWCLOCK_OPT_UTC 0x02
321#define HWCLOCK_OPT_SHOW 0x04
322#define HWCLOCK_OPT_HCTOSYS 0x08
323#define HWCLOCK_OPT_SYSTOHC 0x10
324#define HWCLOCK_OPT_SYSTZ 0x20
325#define HWCLOCK_OPT_RTCFILE 0x40
326
327int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
328int hwclock_main(int argc UNUSED_PARAM, char **argv)
329{
330 const char *rtcname = NULL;
331 unsigned opt;
332 int utc;
333
334#if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
335 static const char hwclock_longopts[] ALIGN1 =
336 "localtime\0" No_argument "l" /* short opt is non-standard */
337 "utc\0" No_argument "u"
338 "show\0" No_argument "r"
339 "hctosys\0" No_argument "s"
340 "systohc\0" No_argument "w"
341 "systz\0" No_argument "t" /* short opt is non-standard */
342 "rtc\0" Required_argument "f"
343 ;
344 applet_long_options = hwclock_longopts;
345#endif
346
347 /* Initialize "timezone" (libc global variable) */
348 tzset();
349
350 opt_complementary = "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l";
351 opt = getopt32(argv, "lurswtf:", &rtcname);
352
353 /* If -u or -l wasn't given check if we are using utc */
354 if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
355 utc = (opt & HWCLOCK_OPT_UTC);
356 else
357 utc = rtc_adjtime_is_utc();
358
359 if (opt & HWCLOCK_OPT_HCTOSYS)
360 to_sys_clock(&rtcname, utc);
361 else if (opt & HWCLOCK_OPT_SYSTOHC)
362 from_sys_clock(&rtcname, utc);
363 else if (opt & HWCLOCK_OPT_SYSTZ)
364 set_system_clock_timezone(utc);
365 else
366 /* default HWCLOCK_OPT_SHOW */
367 show_clock(&rtcname, utc);
368
369 return 0;
370}
371
generated by cgit at 2024-05-16 00:50:55 (GMT)