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 (5.8 kb)"
11 //config: default y
12 //config: help
13 //config: The hwclock utility is used to read and set the hardware clock
14 //config: on a system. This is primarily used to set the current time on
15 //config: shutdown in the hardware clock, so the hardware will keep the
16 //config: correct time when Linux is _not_ running.
17 //config:
18 //config:config FEATURE_HWCLOCK_ADJTIME_FHS
19 //config: bool "Use FHS /var/lib/hwclock/adjtime"
20 //config: default n # util-linux-ng in Fedora 13 still uses /etc/adjtime
21 //config: depends on HWCLOCK
22 //config: help
23 //config: Starting with FHS 2.3, the adjtime state file is supposed to exist
24 //config: at /var/lib/hwclock/adjtime instead of /etc/adjtime. If you wish
25 //config: to use the FHS behavior, answer Y here, otherwise answer N for the
26 //config: classic /etc/adjtime path.
27 //config:
28 //config: pathname.com/fhs/pub/fhs-2.3.html#VARLIBHWCLOCKSTATEDIRECTORYFORHWCLO
29
30 //applet:IF_HWCLOCK(APPLET(hwclock, BB_DIR_SBIN, BB_SUID_DROP))
31
32 //kbuild:lib-$(CONFIG_HWCLOCK) += hwclock.o
33
34 #include "libbb.h"
35 /* After libbb.h, since it needs sys/types.h on some systems */
36 #include <sys/utsname.h>
37 #include "rtc_.h"
38
39
40 //musl has no __MUSL__ or similar define to check for,
41 //but its <sys/types.h> has these lines:
42 // #define __NEED_fsblkcnt_t
43 // #define __NEED_fsfilcnt_t
44 #if defined(__linux__) && defined(__NEED_fsblkcnt_t) && defined(__NEED_fsfilcnt_t)
45 # define LIBC_IS_MUSL 1
46 # include <sys/syscall.h>
47 #else
48 # define LIBC_IS_MUSL 0
49 #endif
50
51
52 /* diff code is disabled: it's not sys/hw clock diff, it's some useless
53 * "time between hwclock was started and we saw CMOS tick" quantity.
54 * It's useless since hwclock is started at a random moment,
55 * thus the quantity is also random, useless. Showing 0.000000 does not
56 * deprive us from any useful info.
57 *
58 * SHOW_HWCLOCK_DIFF code in this file shows the difference between system
59 * and hw clock. It is useful, but not compatible with standard hwclock.
60 * Thus disabled.
61 */
62 #define SHOW_HWCLOCK_DIFF 0
63
64
65 #if !SHOW_HWCLOCK_DIFF
66 # define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc)
67 #endif
read_rtc(const char ** pp_rtcname,struct timeval * sys_tv,int utc)68 static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc)
69 {
70 struct tm tm_time;
71 int fd;
72
73 fd = rtc_xopen(pp_rtcname, O_RDONLY);
74
75 rtc_read_tm(&tm_time, fd);
76
77 #if SHOW_HWCLOCK_DIFF
78 {
79 int before = tm_time.tm_sec;
80 while (1) {
81 rtc_read_tm(&tm_time, fd);
82 xgettimeofday(sys_tv);
83 if (before != (int)tm_time.tm_sec)
84 break;
85 }
86 }
87 #endif
88
89 if (ENABLE_FEATURE_CLEAN_UP)
90 close(fd);
91
92 return rtc_tm2time(&tm_time, utc);
93 }
94
show_clock(const char ** pp_rtcname,int utc)95 static void show_clock(const char **pp_rtcname, int utc)
96 {
97 #if SHOW_HWCLOCK_DIFF
98 struct timeval sys_tv;
99 #endif
100 time_t t = read_rtc(pp_rtcname, &sys_tv, utc);
101
102 #if ENABLE_LOCALE_SUPPORT
103 /* Standard hwclock uses locale-specific output format */
104 char cp[64];
105 struct tm *ptm = localtime(&t);
106 strftime(cp, sizeof(cp), "%c", ptm);
107 #else
108 char *cp = ctime(&t);
109 chomp(cp);
110 #endif
111
112 #if !SHOW_HWCLOCK_DIFF
113 printf("%s 0.000000 seconds\n", cp);
114 #else
115 {
116 long diff = sys_tv.tv_sec - t;
117 if (diff < 0 /*&& tv.tv_usec != 0*/) {
118 /* Why we need diff++? */
119 /* diff >= 0 is ok: | diff < 0, can't just use tv.tv_usec: */
120 /* 45.520820 | 43.520820 */
121 /* - 44.000000 | - 45.000000 */
122 /* = 1.520820 | = -1.479180, not -2.520820! */
123 diff++;
124 /* Should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
125 sys_tv.tv_usec = 999999 - sys_tv.tv_usec;
126 }
127 printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec);
128 }
129 #endif
130 }
131
set_kernel_tz(const struct timezone * tz)132 static void set_kernel_tz(const struct timezone *tz)
133 {
134 #if LIBC_IS_MUSL
135 /* musl libc does not pass tz argument to syscall
136 * because "it's deprecated by POSIX, therefore it's fine
137 * if we gratuitously break stuff" :(
138 */
139 #if !defined(SYS_settimeofday) && defined(SYS_settimeofday_time32)
140 # define SYS_settimeofday SYS_settimeofday_time32
141 #endif
142 int ret = syscall(SYS_settimeofday, NULL, tz);
143 #else
144 int ret = settimeofday(NULL, tz);
145 #endif
146 if (ret)
147 bb_simple_perror_msg_and_die("settimeofday");
148 }
149
150 /*
151 * At system boot, kernel may set system time from RTC,
152 * but it knows nothing about timezones. If RTC is in local time,
153 * then system time is wrong - it is offset by timezone.
154 * --systz option corrects system time if RTC is in local time,
155 * and (always) sets in-kernel timezone.
156 * (Unlike --hctosys, it does not read the RTC).
157 *
158 * util-linux's code has this comment:
159 * RTC | settimeofday calls
160 * ------|-------------------------------------------------
161 * Local | 1st) warps system time*, sets PCIL* and kernel tz
162 * UTC | 1st) locks warp_clock 2nd) sets kernel tz
163 * * only on first call after boot
164 * (PCIL is "persistent_clock_is_local" kernel internal flag,
165 * it makes kernel save RTC in local time, not UTC.)
166 */
set_kernel_timezone_and_clock(int utc,const struct timeval * hctosys)167 static void set_kernel_timezone_and_clock(int utc, const struct timeval *hctosys)
168 {
169 time_t cur;
170 struct tm *broken;
171 struct timezone tz = { 0 };
172
173 /* if --utc, prevent kernel's warp_clock() with a dummy call */
174 if (utc)
175 set_kernel_tz(&tz);
176
177 /* Set kernel's timezone offset based on userspace one */
178 //It's tempting to call tzset() and use libc global "timezone" variable
179 //...but it does NOT include DST shift (IOW: it's WRONG, usually by one hour,
180 //if DST is in effect!) Thus this ridiculous dance:
181 cur = time(NULL);
182 broken = localtime(&cur);
183 tz.tz_minuteswest = -broken->tm_gmtoff / 60;
184 /*tz.tz_dsttime = 0; already is */
185 set_kernel_tz(&tz); /* MIGHT warp_clock() if 1st call since boot */
186
187 if (hctosys) /* it's --hctosys: set time too */
188 xsettimeofday(hctosys);
189 }
190
to_sys_clock(const char ** pp_rtcname,int utc)191 static void to_sys_clock(const char **pp_rtcname, int utc)
192 {
193 struct timeval tv;
194
195 tv.tv_sec = read_rtc(pp_rtcname, NULL, utc);
196 tv.tv_usec = 0;
197 return set_kernel_timezone_and_clock(utc, &tv);
198 }
199
from_sys_clock(const char ** pp_rtcname,int utc)200 static void from_sys_clock(const char **pp_rtcname, int utc)
201 {
202 #if 1
203 struct timeval tv;
204 struct tm tm_time;
205 int rtc;
206
207 rtc = rtc_xopen(pp_rtcname, O_WRONLY);
208 xgettimeofday(&tv);
209 /* Prepare tm_time */
210 if (sizeof(time_t) == sizeof(tv.tv_sec)) {
211 if (utc)
212 gmtime_r((time_t*)&tv.tv_sec, &tm_time);
213 else
214 localtime_r((time_t*)&tv.tv_sec, &tm_time);
215 } else {
216 time_t t = tv.tv_sec;
217 if (utc)
218 gmtime_r(&t, &tm_time);
219 else
220 localtime_r(&t, &tm_time);
221 }
222 #else
223 /* Bloated code which tries to set hw clock with better precision.
224 * On x86, even though code does set hw clock within <1ms of exact
225 * whole seconds, apparently hw clock (at least on some machines)
226 * doesn't reset internal fractional seconds to 0,
227 * making all this a pointless exercise.
228 */
229 /* If we see that we are N usec away from whole second,
230 * we'll sleep for N-ADJ usecs. ADJ corrects for the fact
231 * that CPU is not infinitely fast.
232 * On infinitely fast CPU, next wakeup would be
233 * on (exactly_next_whole_second - ADJ). On real CPUs,
234 * this difference between current time and whole second
235 * is less than ADJ (assuming system isn't heavily loaded).
236 */
237 /* Small value of 256us gives very precise sync for 2+ GHz CPUs.
238 * Slower CPUs will fail to sync and will go to bigger
239 * ADJ values. qemu-emulated armv4tl with ~100 MHz
240 * performance ends up using ADJ ~= 4*1024 and it takes
241 * 2+ secs (2 tries with successively larger ADJ)
242 * to sync. Even straced one on the same qemu (very slow)
243 * takes only 4 tries.
244 */
245 #define TWEAK_USEC 256
246 unsigned adj = TWEAK_USEC;
247 struct tm tm_time;
248 struct timeval tv;
249 int rtc = rtc_xopen(pp_rtcname, O_WRONLY);
250
251 /* Try to catch the moment when whole second is close */
252 while (1) {
253 unsigned rem_usec;
254 time_t t;
255
256 xgettimeofday(&tv);
257
258 t = tv.tv_sec;
259 rem_usec = 1000000 - tv.tv_usec;
260 if (rem_usec < adj) {
261 /* Close enough */
262 small_rem:
263 t++;
264 }
265
266 /* Prepare tm_time from t */
267 if (utc)
268 gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
269 else
270 localtime_r(&t, &tm_time); /* same */
271
272 if (adj >= 32*1024) {
273 break; /* 32 ms diff and still no luck?? give up trying to sync */
274 }
275
276 /* gmtime/localtime took some time, re-get cur time */
277 xgettimeofday(&tv);
278
279 if (tv.tv_sec < t /* we are still in old second */
280 || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
281 ) {
282 break; /* good, we are in sync! */
283 }
284
285 rem_usec = 1000000 - tv.tv_usec;
286 if (rem_usec < adj) {
287 t = tv.tv_sec;
288 goto small_rem; /* already close to next sec, don't sleep */
289 }
290
291 /* Try to sync up by sleeping */
292 usleep(rem_usec - adj);
293
294 /* Jump to 1ms diff, then increase fast (x2): EVERY loop
295 * takes ~1 sec, people won't like slowly converging code here!
296 */
297 //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
298 if (adj < 512)
299 adj = 512;
300 /* ... and if last "overshoot" does not look insanely big,
301 * just use it as adj increment. This makes convergence faster.
302 */
303 if (tv.tv_usec < adj * 8) {
304 adj += tv.tv_usec;
305 continue;
306 }
307 adj *= 2;
308 }
309 /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
310 * Look for a value which makes tv_usec close to 999999 or 0.
311 * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
312 */
313 //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
314 #endif
315
316 tm_time.tm_isdst = 0;
317 xioctl(rtc, RTC_SET_TIME, &tm_time);
318
319 if (ENABLE_FEATURE_CLEAN_UP)
320 close(rtc);
321 }
322
323 // hwclock from util-linux 2.36.1
324 // hwclock [function] [option...]
325 //Functions:
326 // -r, --show display the RTC time
327 // --get display drift corrected RTC time
328 // --set set the RTC according to --date
329 // -s, --hctosys set the system time from the RTC
330 // -w, --systohc set the RTC from the system time
331 // --systz send timescale configurations to the kernel
332 // -a, --adjust adjust the RTC to account for systematic drift
333 // --predict predict the drifted RTC time according to --date
334 //Options:
335 // -u, --utc the RTC timescale is UTC
336 // -l, --localtime the RTC timescale is Local
337 // -f, --rtc <file> use an alternate file to /dev/rtc0
338 // --directisa use the ISA bus instead of /dev/rtc0 access
339 // --date <time> date/time input for --set and --predict
340 // --delay <sec> delay used when set new RTC time
341 // --update-drift update the RTC drift factor
342 // --noadjfile do not use /etc/adjtime
343 // --adjfile <file> use an alternate file to /etc/adjtime
344 // --test dry run; implies --verbose
345 // -v, --verbose display more details
346
347 //usage:#define hwclock_trivial_usage
348 //usage: IF_LONG_OPTS(
349 //usage: "[-swul] [--systz] [-f DEV]"
350 //usage: )
351 //usage: IF_NOT_LONG_OPTS(
352 //usage: "[-swult] [-f DEV]"
353 //usage: )
354 //usage:#define hwclock_full_usage "\n\n"
355 //usage: "Show or set hardware clock (RTC)\n"
356 ///////: "\n -r Show RTC time"
357 ///////-r is default, don't bother showing it in help
358 //usage: "\n -s Set system time from RTC"
359 //usage: "\n -w Set RTC from system time"
360 //usage: IF_LONG_OPTS(
361 //usage: "\n --systz Set in-kernel timezone, correct system time"
362 //usage: "\n if RTC is kept in local time"
363 //usage: )
364 //usage: "\n -f DEV Use specified device (e.g. /dev/rtc2)"
365 //usage: "\n -u Assume RTC is kept in UTC"
366 //usage: "\n -l Assume RTC is kept in local time"
367 //usage: "\n (if neither is given, read from "ADJTIME_PATH")"
368
369 //TODO: get rid of incompatible -t alias to --systz?
370
371 #define HWCLOCK_OPT_LOCALTIME 0x01
372 #define HWCLOCK_OPT_UTC 0x02
373 #define HWCLOCK_OPT_SHOW 0x04
374 #define HWCLOCK_OPT_HCTOSYS 0x08
375 #define HWCLOCK_OPT_SYSTOHC 0x10
376 #define HWCLOCK_OPT_SYSTZ 0x20
377 #define HWCLOCK_OPT_RTCFILE 0x40
378
379 int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
hwclock_main(int argc UNUSED_PARAM,char ** argv)380 int hwclock_main(int argc UNUSED_PARAM, char **argv)
381 {
382 const char *rtcname = NULL;
383 unsigned opt;
384 int utc;
385 #if ENABLE_LONG_OPTS
386 static const char hwclock_longopts[] ALIGN1 =
387 "localtime\0" No_argument "l"
388 "utc\0" No_argument "u"
389 "show\0" No_argument "r"
390 "hctosys\0" No_argument "s"
391 "systohc\0" No_argument "w"
392 "systz\0" No_argument "t" /* short opt is non-standard */
393 "rtc\0" Required_argument "f"
394 ;
395 #endif
396 opt = getopt32long(argv,
397 "^""lurswtf:v" /* -v is accepted and ignored */
398 "\0"
399 "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l",
400 hwclock_longopts,
401 &rtcname
402 );
403
404 /* If -u or -l wasn't given, check if we are using utc */
405 if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
406 utc = (opt & HWCLOCK_OPT_UTC);
407 else
408 utc = rtc_adjtime_is_utc();
409
410 if (opt & HWCLOCK_OPT_HCTOSYS)
411 to_sys_clock(&rtcname, utc);
412 else if (opt & HWCLOCK_OPT_SYSTOHC)
413 from_sys_clock(&rtcname, utc);
414 else if (opt & HWCLOCK_OPT_SYSTZ)
415 set_kernel_timezone_and_clock(utc, NULL);
416 else
417 /* default HWCLOCK_OPT_SHOW */
418 show_clock(&rtcname, utc);
419
420 return 0;
421 }
422