src/shared/hwclock.c

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