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