/* vi: set sw=4 ts=4: */
/*
* Mini hwclock implementation for busybox
*
* Copyright (C) 2002 Robert Griebl <griebl@gmx.de>
*
* 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 <sys/utsname.h>
#include "rtc_.h"
//musl has no __MUSL__ or similar define to check for,
//but its <sys/types.h> 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 <sys/syscall.h>
#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 <file> use an alternate file to /dev/rtc0
// --directisa use the ISA bus instead of /dev/rtc0 access
// --date <time> date/time input for --set and --predict
// --delay <sec> delay used when set new RTC time
// --update-drift update the RTC drift factor
// --noadjfile do not use /etc/adjtime
// --adjfile <file> use an alternate file to /etc/adjtime
// --test dry run; implies --verbose
// -v, --verbose display more details
//usage:#define hwclock_trivial_usage
//usage: IF_LONG_OPTS(
//usage: "[-swul] [--systz] [-f DEV]"
//usage: )
//usage: IF_NOT_LONG_OPTS(
//usage: "[-swult] [-f DEV]"
//usage: )
//usage:#define hwclock_full_usage "\n\n"
//usage: "Show or set hardware clock (RTC)\n"
///////: "\n -r Show RTC time"
///////-r is default, don't bother showing it in help
//usage: "\n -s Set system time from RTC"
//usage: "\n -w Set RTC from system time"
//usage: IF_LONG_OPTS(
//usage: "\n --systz Set in-kernel timezone, correct system time"
//usage: "\n if RTC is kept in local time"
//usage: )
//usage: "\n -f DEV Use specified device (e.g. /dev/rtc2)"
//usage: "\n -u Assume RTC is kept in UTC"
//usage: "\n -l Assume RTC is kept in local time"
//usage: "\n (if neither is given, read from "ADJTIME_PATH")"
//TODO: get rid of incompatible -t alias to --systz?
#define HWCLOCK_OPT_LOCALTIME 0x01
#define HWCLOCK_OPT_UTC 0x02
#define HWCLOCK_OPT_SHOW 0x04
#define HWCLOCK_OPT_HCTOSYS 0x08
#define HWCLOCK_OPT_SYSTOHC 0x10
#define HWCLOCK_OPT_SYSTZ 0x20
#define HWCLOCK_OPT_RTCFILE 0x40
int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int hwclock_main(int argc UNUSED_PARAM, char **argv)
{
const char *rtcname = NULL;
unsigned opt;
int utc;
#if ENABLE_LONG_OPTS
static const char hwclock_longopts[] ALIGN1 =
"localtime\0" No_argument "l"
"utc\0" No_argument "u"
"show\0" No_argument "r"
"hctosys\0" No_argument "s"
"systohc\0" No_argument "w"
"systz\0" No_argument "t" /* short opt is non-standard */
"rtc\0" Required_argument "f"
;
#endif
opt = getopt32long(argv,
"^""lurswtf:v" /* -v is accepted and ignored */
"\0"
"r--wst:w--rst:s--wrt:t--rsw:l--u:u--l",
hwclock_longopts,
&rtcname
);
/* If -u or -l wasn't given, check if we are using utc */
if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
utc = (opt & HWCLOCK_OPT_UTC);
else
utc = rtc_adjtime_is_utc();
if (opt & HWCLOCK_OPT_HCTOSYS)
to_sys_clock(&rtcname, utc);
else if (opt & HWCLOCK_OPT_SYSTOHC)
from_sys_clock(&rtcname, utc);
else if (opt & HWCLOCK_OPT_SYSTZ)
set_kernel_timezone_and_clock(utc, NULL);
else
/* default HWCLOCK_OPT_SHOW */
show_clock(&rtcname, utc);
return 0;
}