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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdbool.h>
#include <time.h>
#include <linux/rtc.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include "alloc-util.h"
#include "clock-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "macro.h"
#include "string-util.h"
int clock_get_hwclock(struct tm *tm) {
_cleanup_close_ int fd = -1;
assert(tm);
fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
if (fd < 0)
return -errno;
/* This leaves the timezone fields of struct tm
* uninitialized! */
if (ioctl(fd, RTC_RD_TIME, tm) < 0)
return -errno;
/* We don't know daylight saving, so we reset this in order not
* to confuse mktime(). */
tm->tm_isdst = -1;
return 0;
}
int clock_set_hwclock(const struct tm *tm) {
_cleanup_close_ int fd = -1;
assert(tm);
fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
if (fd < 0)
return -errno;
return RET_NERRNO(ioctl(fd, RTC_SET_TIME, tm));
}
int clock_is_localtime(const char* adjtime_path) {
_cleanup_fclose_ FILE *f = NULL;
int r;
if (!adjtime_path)
adjtime_path = "/etc/adjtime";
/*
* The third line of adjtime is "UTC" or "LOCAL" or nothing.
* # /etc/adjtime
* 0.0 0 0
* 0
* UTC
*/
f = fopen(adjtime_path, "re");
if (f) {
_cleanup_free_ char *line = NULL;
unsigned i;
for (i = 0; i < 2; i++) { /* skip the first two lines */
r = read_line(f, LONG_LINE_MAX, NULL);
if (r < 0)
return r;
if (r == 0)
return false; /* less than three lines → default to UTC */
}
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0)
return r;
if (r == 0)
return false; /* less than three lines → default to UTC */
return streq(line, "LOCAL");
} else if (errno != ENOENT)
return -errno;
/* adjtime not present → default to UTC */
return false;
}
int clock_set_timezone(int *ret_minutesdelta) {
struct timespec ts;
struct tm tm;
int minutesdelta;
struct timezone tz;
assert_se(clock_gettime(CLOCK_REALTIME, &ts) == 0);
assert_se(localtime_r(&ts.tv_sec, &tm));
minutesdelta = tm.tm_gmtoff / 60;
tz = (struct timezone) {
.tz_minuteswest = -minutesdelta,
.tz_dsttime = 0, /* DST_NONE */
};
/* If the RTC does not run in UTC but in local time, the very first call to settimeofday() will set
* the kernel's timezone and will warp the system clock, so that it runs in UTC instead of the local
* time we have read from the RTC. */
if (settimeofday(NULL, &tz) < 0)
return -errno;
if (ret_minutesdelta)
*ret_minutesdelta = minutesdelta;
return 0;
}
int clock_reset_timewarp(void) {
static const struct timezone tz = {
.tz_minuteswest = 0,
.tz_dsttime = 0, /* DST_NONE */
};
/* The very first call to settimeofday() does time warp magic. Do a dummy call here, so the time
* warping is sealed and all later calls behave as expected. */
return RET_NERRNO(settimeofday(NULL, &tz));
}
#define EPOCH_FILE "/usr/lib/clock-epoch"
int clock_apply_epoch(ClockChangeDirection *ret_attempted_change) {
usec_t epoch_usec, now_usec;
struct stat st;
/* NB: we update *ret_attempted_change in *all* cases, both
* on success and failure, to indicate what we intended to do! */
assert(ret_attempted_change);
if (stat(EPOCH_FILE, &st) < 0) {
if (errno != ENOENT)
log_warning_errno(errno, "Cannot stat " EPOCH_FILE ": %m");
epoch_usec = (usec_t) TIME_EPOCH * USEC_PER_SEC;
} else
epoch_usec = timespec_load(&st.st_mtim);
now_usec = now(CLOCK_REALTIME);
if (now_usec < epoch_usec)
*ret_attempted_change = CLOCK_CHANGE_FORWARD;
else if (CLOCK_VALID_RANGE_USEC_MAX > 0 && now_usec > usec_add(epoch_usec, CLOCK_VALID_RANGE_USEC_MAX))
*ret_attempted_change = CLOCK_CHANGE_BACKWARD;
else {
*ret_attempted_change = CLOCK_CHANGE_NOOP;
return 0;
}
if (clock_settime(CLOCK_REALTIME, TIMESPEC_STORE(epoch_usec)) < 0)
return -errno;
return 1;
}
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