src/basic/clock-util.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 <errno.h>
  23 #include <fcntl.h>
  24 #include <limits.h>
  25 #include <stdbool.h>
  26 #include <time.h>
  27 #include <linux/rtc.h>
  28 #include <stdio.h>
  29 #include <sys/ioctl.h>
  30 #include <sys/time.h>
  31
  32 #include "clock-util.h"
  33 #include "fd-util.h"
  34 #include "macro.h"
  35 #include "string-util.h"
  36 #include "util.h"
  37
  38 int clock_get_hwclock(struct tm *tm) {
  39         _cleanup_close_ int fd = -1;
  40
  41         assert(tm);
  42
  43         fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
  44         if (fd < 0)
  45                 return -errno;
  46
  47         /* This leaves the timezone fields of struct tm
  48          * uninitialized! */
  49         if (ioctl(fd, RTC_RD_TIME, tm) < 0)
  50                 return -errno;
  51
  52         /* We don't know daylight saving, so we reset this in order not
  53          * to confuse mktime(). */
  54         tm->tm_isdst = -1;
  55
  56         return 0;
  57 }
  58
  59 int clock_set_hwclock(const struct tm *tm) {
  60         _cleanup_close_ int fd = -1;
  61
  62         assert(tm);
  63
  64         fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
  65         if (fd < 0)
  66                 return -errno;
  67
  68         if (ioctl(fd, RTC_SET_TIME, tm) < 0)
  69                 return -errno;
  70
  71         return 0;
  72 }
  73
  74 int clock_is_localtime(void) {
  75         _cleanup_fclose_ FILE *f;
  76
  77         /*
  78          * The third line of adjtime is "UTC" or "LOCAL" or nothing.
  79          *   # /etc/adjtime
  80          *   0.0 0 0
  81          *   0
  82          *   UTC
  83          */
  84         f = fopen("/etc/adjtime", "re");
  85         if (f) {
  86                 char line[LINE_MAX];
  87                 bool b;
  88
  89                 b = fgets(line, sizeof(line), f) &&
  90                         fgets(line, sizeof(line), f) &&
  91                         fgets(line, sizeof(line), f);
  92                 if (!b)
  93                         return -EIO;
  94
  95                 truncate_nl(line);
  96                 return streq(line, "LOCAL");
  97
  98         } else if (errno != ENOENT)
  99                 return -errno;
 100
 101         return 0;
 102 }
 103
 104 int clock_set_timezone(int *min) {
 105         const struct timeval *tv_null = NULL;
 106         struct timespec ts;
 107         struct tm *tm;
 108         int minutesdelta;
 109         struct timezone tz;
 110
 111         assert_se(clock_gettime(CLOCK_REALTIME, &ts) == 0);
 112         assert_se(tm = localtime(&ts.tv_sec));
 113         minutesdelta = tm->tm_gmtoff / 60;
 114
 115         tz.tz_minuteswest = -minutesdelta;
 116         tz.tz_dsttime = 0; /* DST_NONE */
 117
 118         /*
 119          * If the RTC does not run in UTC but in local time, the very first
 120          * call to settimeofday() will set the kernel's timezone and will warp the
 121          * system clock, so that it runs in UTC instead of the local time we
 122          * have read from the RTC.
 123          */
 124         if (settimeofday(tv_null, &tz) < 0)
 125                 return negative_errno();
 126
 127         if (min)
 128                 *min = minutesdelta;
 129         return 0;
 130 }
 131
 132 int clock_reset_timewarp(void) {
 133         const struct timeval *tv_null = NULL;
 134         struct timezone tz;
 135
 136         tz.tz_minuteswest = 0;
 137         tz.tz_dsttime = 0; /* DST_NONE */
 138
 139         /*
 140          * The very first call to settimeofday() does time warp magic. Do a
 141          * dummy call here, so the time warping is sealed and all later calls
 142          * behave as expected.
 143          */
 144         if (settimeofday(tv_null, &tz) < 0)
 145                 return -errno;
 146
 147         return 0;
 148 }