/* vi: set sw=4 ts=4: */ /* * Mini hwclock implementation for busybox * * Copyright (C) 2002 Robert Griebl * * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ //config:config HWCLOCK //config: bool "hwclock (5.8 kb)" //config: default y //config: help //config: The hwclock utility is used to read and set the hardware clock //config: on a system. This is primarily used to set the current time on //config: shutdown in the hardware clock, so the hardware will keep the //config: correct time when Linux is _not_ running. //config: //config:config FEATURE_HWCLOCK_ADJTIME_FHS //config: bool "Use FHS /var/lib/hwclock/adjtime" //config: default n # util-linux-ng in Fedora 13 still uses /etc/adjtime //config: depends on HWCLOCK //config: help //config: Starting with FHS 2.3, the adjtime state file is supposed to exist //config: at /var/lib/hwclock/adjtime instead of /etc/adjtime. If you wish //config: to use the FHS behavior, answer Y here, otherwise answer N for the //config: classic /etc/adjtime path. //config: //config: pathname.com/fhs/pub/fhs-2.3.html#VARLIBHWCLOCKSTATEDIRECTORYFORHWCLO //applet:IF_HWCLOCK(APPLET(hwclock, BB_DIR_SBIN, BB_SUID_DROP)) //kbuild:lib-$(CONFIG_HWCLOCK) += hwclock.o #include "libbb.h" /* After libbb.h, since it needs sys/types.h on some systems */ #include #include "rtc_.h" //musl has no __MUSL__ or similar define to check for, //but its has these lines: // #define __NEED_fsblkcnt_t // #define __NEED_fsfilcnt_t #if defined(__linux__) && defined(__NEED_fsblkcnt_t) && defined(__NEED_fsfilcnt_t) # define LIBC_IS_MUSL 1 # include #else # define LIBC_IS_MUSL 0 #endif /* diff code is disabled: it's not sys/hw clock diff, it's some useless * "time between hwclock was started and we saw CMOS tick" quantity. * It's useless since hwclock is started at a random moment, * thus the quantity is also random, useless. Showing 0.000000 does not * deprive us from any useful info. * * SHOW_HWCLOCK_DIFF code in this file shows the difference between system * and hw clock. It is useful, but not compatible with standard hwclock. * Thus disabled. */ #define SHOW_HWCLOCK_DIFF 0 #if !SHOW_HWCLOCK_DIFF # define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc) #endif static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc) { struct tm tm_time; int fd; fd = rtc_xopen(pp_rtcname, O_RDONLY); rtc_read_tm(&tm_time, fd); #if SHOW_HWCLOCK_DIFF { int before = tm_time.tm_sec; while (1) { rtc_read_tm(&tm_time, fd); xgettimeofday(sys_tv); if (before != (int)tm_time.tm_sec) break; } } #endif if (ENABLE_FEATURE_CLEAN_UP) close(fd); return rtc_tm2time(&tm_time, utc); } static void show_clock(const char **pp_rtcname, int utc) { #if SHOW_HWCLOCK_DIFF struct timeval sys_tv; #endif time_t t = read_rtc(pp_rtcname, &sys_tv, utc); #if ENABLE_LOCALE_SUPPORT /* Standard hwclock uses locale-specific output format */ char cp[64]; struct tm *ptm = localtime(&t); strftime(cp, sizeof(cp), "%c", ptm); #else char *cp = ctime(&t); chomp(cp); #endif #if !SHOW_HWCLOCK_DIFF printf("%s 0.000000 seconds\n", cp); #else { long diff = sys_tv.tv_sec - t; if (diff < 0 /*&& tv.tv_usec != 0*/) { /* Why we need diff++? */ /* diff >= 0 is ok: | diff < 0, can't just use tv.tv_usec: */ /* 45.520820 | 43.520820 */ /* - 44.000000 | - 45.000000 */ /* = 1.520820 | = -1.479180, not -2.520820! */ diff++; /* Should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */ sys_tv.tv_usec = 999999 - sys_tv.tv_usec; } printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec); } #endif } static void set_kernel_tz(const struct timezone *tz) { #if LIBC_IS_MUSL /* musl libc does not pass tz argument to syscall * because "it's deprecated by POSIX, therefore it's fine * if we gratuitously break stuff" :( */ #if !defined(SYS_settimeofday) && defined(SYS_settimeofday_time32) # define SYS_settimeofday SYS_settimeofday_time32 #endif int ret = syscall(SYS_settimeofday, NULL, tz); #else int ret = settimeofday(NULL, tz); #endif if (ret) bb_simple_perror_msg_and_die("settimeofday"); } /* * At system boot, kernel may set system time from RTC, * but it knows nothing about timezones. If RTC is in local time, * then system time is wrong - it is offset by timezone. * --systz option corrects system time if RTC is in local time, * and (always) sets in-kernel timezone. * (Unlike --hctosys, it does not read the RTC). * * util-linux's code has this comment: * RTC | settimeofday calls * ------|------------------------------------------------- * Local | 1st) warps system time*, sets PCIL* and kernel tz * UTC | 1st) locks warp_clock 2nd) sets kernel tz * * only on first call after boot * (PCIL is "persistent_clock_is_local" kernel internal flag, * it makes kernel save RTC in local time, not UTC.) */ static void set_kernel_timezone_and_clock(int utc, const struct timeval *hctosys) { time_t cur; struct tm *broken; struct timezone tz = { 0 }; /* if --utc, prevent kernel's warp_clock() with a dummy call */ if (utc) set_kernel_tz(&tz); /* Set kernel's timezone offset based on userspace one */ //It's tempting to call tzset() and use libc global "timezone" variable //...but it does NOT include DST shift (IOW: it's WRONG, usually by one hour, //if DST is in effect!) Thus this ridiculous dance: cur = time(NULL); broken = localtime(&cur); tz.tz_minuteswest = -broken->tm_gmtoff / 60; /*tz.tz_dsttime = 0; already is */ set_kernel_tz(&tz); /* MIGHT warp_clock() if 1st call since boot */ if (hctosys) /* it's --hctosys: set time too */ xsettimeofday(hctosys); } static void to_sys_clock(const char **pp_rtcname, int utc) { struct timeval tv; tv.tv_sec = read_rtc(pp_rtcname, NULL, utc); tv.tv_usec = 0; return set_kernel_timezone_and_clock(utc, &tv); } static void from_sys_clock(const char **pp_rtcname, int utc) { #if 1 struct timeval tv; struct tm tm_time; int rtc; rtc = rtc_xopen(pp_rtcname, O_WRONLY); xgettimeofday(&tv); /* Prepare tm_time */ if (sizeof(time_t) == sizeof(tv.tv_sec)) { if (utc) gmtime_r((time_t*)&tv.tv_sec, &tm_time); else localtime_r((time_t*)&tv.tv_sec, &tm_time); } else { time_t t = tv.tv_sec; if (utc) gmtime_r(&t, &tm_time); else localtime_r(&t, &tm_time); } #else /* Bloated code which tries to set hw clock with better precision. * On x86, even though code does set hw clock within <1ms of exact * whole seconds, apparently hw clock (at least on some machines) * doesn't reset internal fractional seconds to 0, * making all this a pointless exercise. */ /* If we see that we are N usec away from whole second, * we'll sleep for N-ADJ usecs. ADJ corrects for the fact * that CPU is not infinitely fast. * On infinitely fast CPU, next wakeup would be * on (exactly_next_whole_second - ADJ). On real CPUs, * this difference between current time and whole second * is less than ADJ (assuming system isn't heavily loaded). */ /* Small value of 256us gives very precise sync for 2+ GHz CPUs. * Slower CPUs will fail to sync and will go to bigger * ADJ values. qemu-emulated armv4tl with ~100 MHz * performance ends up using ADJ ~= 4*1024 and it takes * 2+ secs (2 tries with successively larger ADJ) * to sync. Even straced one on the same qemu (very slow) * takes only 4 tries. */ #define TWEAK_USEC 256 unsigned adj = TWEAK_USEC; struct tm tm_time; struct timeval tv; int rtc = rtc_xopen(pp_rtcname, O_WRONLY); /* Try to catch the moment when whole second is close */ while (1) { unsigned rem_usec; time_t t; xgettimeofday(&tv); t = tv.tv_sec; rem_usec = 1000000 - tv.tv_usec; if (rem_usec < adj) { /* Close enough */ small_rem: t++; } /* Prepare tm_time from t */ if (utc) gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */ else localtime_r(&t, &tm_time); /* same */ if (adj >= 32*1024) { break; /* 32 ms diff and still no luck?? give up trying to sync */ } /* gmtime/localtime took some time, re-get cur time */ xgettimeofday(&tv); if (tv.tv_sec < t /* we are still in old second */ || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */ ) { break; /* good, we are in sync! */ } rem_usec = 1000000 - tv.tv_usec; if (rem_usec < adj) { t = tv.tv_sec; goto small_rem; /* already close to next sec, don't sleep */ } /* Try to sync up by sleeping */ usleep(rem_usec - adj); /* Jump to 1ms diff, then increase fast (x2): EVERY loop * takes ~1 sec, people won't like slowly converging code here! */ //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec); if (adj < 512) adj = 512; /* ... and if last "overshoot" does not look insanely big, * just use it as adj increment. This makes convergence faster. */ if (tv.tv_usec < adj * 8) { adj += tv.tv_usec; continue; } adj *= 2; } /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync. * Look for a value which makes tv_usec close to 999999 or 0. * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200 */ //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec); #endif tm_time.tm_isdst = 0; xioctl(rtc, RTC_SET_TIME, &tm_time); if (ENABLE_FEATURE_CLEAN_UP) close(rtc); } // hwclock from util-linux 2.36.1 // hwclock [function] [option...] //Functions: // -r, --show display the RTC time // --get display drift corrected RTC time // --set set the RTC according to --date // -s, --hctosys set the system time from the RTC // -w, --systohc set the RTC from the system time // --systz send timescale configurations to the kernel // -a, --adjust adjust the RTC to account for systematic drift // --predict predict the drifted RTC time according to --date //Options: // -u, --utc the RTC timescale is UTC // -l, --localtime the RTC timescale is Local // -f, --rtc use an alternate file to /dev/rtc0 // --directisa use the ISA bus instead of /dev/rtc0 access // --date