1 files changed, 157 insertions, 0 deletions
diff --git a/src/shared/clock-util.c b/src/shared/clock-util.c
new file mode 100644
index 0000000000..1877a81434
--- /dev/null
+++ b/src/shared/clock-util.c
@@ -0,0 +1,157 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#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 "fd-util.h"
+#include "fileio.h"
+#include "macro.h"
+#include "string-util.h"
+#include "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;
+
+        if (ioctl(fd, RTC_SET_TIME, tm) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int clock_is_localtime(const char* adjtime_path) {
+        _cleanup_fclose_ FILE *f;
+        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 *min) {
+        const struct timeval *tv_null = NULL;
+        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.tz_minuteswest = -minutesdelta;
+        tz.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(tv_null, &tz) < 0)
+                return negative_errno();
+
+        if (min)
+                *min = minutesdelta;
+        return 0;
+}
+
+int clock_reset_timewarp(void) {
+        const struct timeval *tv_null = NULL;
+        struct timezone tz;
+
+        tz.tz_minuteswest = 0;
+        tz.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.
+         */
+        if (settimeofday(tv_null, &tz) < 0)
+                return -errno;
+
+        return 0;
+}
+
+#define TIME_EPOCH_USEC ((usec_t) TIME_EPOCH * USEC_PER_SEC)
+
+int clock_apply_epoch(void) {
+        struct timespec ts;
+
+        if (now(CLOCK_REALTIME) >= TIME_EPOCH_USEC)
+                return 0;
+
+        if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, TIME_EPOCH_USEC)) < 0)
+                return -errno;
+
+        return 1;
+}