src/basic/clock-util.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2010-2012 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <limits.h>
  23 #include <stdbool.h>
  24 #include <time.h>
  25 #include <linux/rtc.h>
  26 #include <stdio.h>
  27 #include <sys/ioctl.h>
  28 #include <sys/time.h>
  29
  30 #include "clock-util.h"
  31 #include "fd-util.h"
  32 #include "macro.h"
  33 #include "string-util.h"
  34 #include "util.h"
  35
  36 int clock_get_hwclock(struct tm *tm) {
  37         _cleanup_close_ int fd = -1;
  38
  39         assert(tm);
  40
  41         fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
  42         if (fd < 0)
  43                 return -errno;
  44
  45         /* This leaves the timezone fields of struct tm
  46          * uninitialized! */
  47         if (ioctl(fd, RTC_RD_TIME, tm) < 0)
  48                 return -errno;
  49
  50         /* We don't know daylight saving, so we reset this in order not
  51          * to confuse mktime(). */
  52         tm->tm_isdst = -1;
  53
  54         return 0;
  55 }
  56
  57 int clock_set_hwclock(const struct tm *tm) {
  58         _cleanup_close_ int fd = -1;
  59
  60         assert(tm);
  61
  62         fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
  63         if (fd < 0)
  64                 return -errno;
  65
  66         if (ioctl(fd, RTC_SET_TIME, tm) < 0)
  67                 return -errno;
  68
  69         return 0;
  70 }
  71
  72 int clock_is_localtime(const char* adjtime_path) {
  73         _cleanup_fclose_ FILE *f;
  74
  75         if (adjtime_path == NULL)
  76                 adjtime_path = "/etc/adjtime";
  77
  78         /*
  79          * The third line of adjtime is "UTC" or "LOCAL" or nothing.
  80          *   # /etc/adjtime
  81          *   0.0 0 0
  82          *   0
  83          *   UTC
  84          */
  85         f = fopen(adjtime_path, "re");
  86         if (f) {
  87                 char line[LINE_MAX];
  88                 bool b;
  89
  90                 b = fgets(line, sizeof(line), f) &&
  91                         fgets(line, sizeof(line), f) &&
  92                         fgets(line, sizeof(line), f);
  93                 if (!b)
  94                         /* less than three lines -> default to UTC */
  95                         return 0;
  96
  97                 truncate_nl(line);
  98                 return streq(line, "LOCAL");
  99
 100         } else if (errno != ENOENT)
 101                 return -errno;
 102
 103         /* adjtime not present -> default to UTC */
 104         return 0;
 105 }
 106
 107 int clock_set_timezone(int *min) {
 108         const struct timeval *tv_null = NULL;
 109         struct timespec ts;
 110         struct tm *tm;
 111         int minutesdelta;
 112         struct timezone tz;
 113
 114         assert_se(clock_gettime(CLOCK_REALTIME, &ts) == 0);
 115         assert_se(tm = localtime(&ts.tv_sec));
 116         minutesdelta = tm->tm_gmtoff / 60;
 117
 118         tz.tz_minuteswest = -minutesdelta;
 119         tz.tz_dsttime = 0; /* DST_NONE */
 120
 121         /*
 122          * If the RTC does not run in UTC but in local time, the very first
 123          * call to settimeofday() will set the kernel's timezone and will warp the
 124          * system clock, so that it runs in UTC instead of the local time we
 125          * have read from the RTC.
 126          */
 127         if (settimeofday(tv_null, &tz) < 0)
 128                 return negative_errno();
 129
 130         if (min)
 131                 *min = minutesdelta;
 132         return 0;
 133 }
 134
 135 int clock_reset_timewarp(void) {
 136         const struct timeval *tv_null = NULL;
 137         struct timezone tz;
 138
 139         tz.tz_minuteswest = 0;
 140         tz.tz_dsttime = 0; /* DST_NONE */
 141
 142         /*
 143          * The very first call to settimeofday() does time warp magic. Do a
 144          * dummy call here, so the time warping is sealed and all later calls
 145          * behave as expected.
 146          */
 147         if (settimeofday(tv_null, &tz) < 0)
 148                 return -errno;
 149
 150         return 0;
 151 }
 152
 153 #define TIME_EPOCH_USEC ((usec_t) TIME_EPOCH * USEC_PER_SEC)
 154
 155 int clock_apply_epoch(void) {
 156         struct timespec ts;
 157
 158         if (now(CLOCK_REALTIME) >= TIME_EPOCH_USEC)
 159                 return 0;
 160
 161         if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, TIME_EPOCH_USEC)) < 0)
 162                 return -errno;
 163
 164         return 1;
 165 }