arch/x86/entry/vsyscall/vsyscall_gtod.c

   1 /*
   2  *  Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
   3  *  Copyright 2003 Andi Kleen, SuSE Labs.
   4  *
   5  *  Modified for x86 32 bit architecture by
   6  *  Stefani Seibold <stefani@seibold.net>
   7  *  sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
   8  *
   9  *  Thanks to hpa@transmeta.com for some useful hint.
  10  *  Special thanks to Ingo Molnar for his early experience with
  11  *  a different vsyscall implementation for Linux/IA32 and for the name.
  12  *
  13  */
  14
  15 #include <linux/timekeeper_internal.h>
  16 #include <asm/vgtod.h>
  17 #include <asm/vvar.h>
  18
  19 int vclocks_used __read_mostly;
  20
  21 DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);
  22
  23 void update_vsyscall_tz(void)
  24 {
  25         vsyscall_gtod_data.tz_minuteswest = sys_tz.tz_minuteswest;
  26         vsyscall_gtod_data.tz_dsttime = sys_tz.tz_dsttime;
  27 }
  28
  29 void update_vsyscall(struct timekeeper *tk)
  30 {
  31         int vclock_mode = tk->tkr_mono.clock->archdata.vclock_mode;
  32         struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;
  33
  34         /* Mark the new vclock used. */
  35         BUILD_BUG_ON(VCLOCK_MAX >= 32);
  36         WRITE_ONCE(vclocks_used, READ_ONCE(vclocks_used) | (1 << vclock_mode));
  37
  38         gtod_write_begin(vdata);
  39
  40         /* copy vsyscall data */
  41         vdata->vclock_mode      = vclock_mode;
  42         vdata->cycle_last       = tk->tkr_mono.cycle_last;
  43         vdata->mask             = tk->tkr_mono.mask;
  44         vdata->mult             = tk->tkr_mono.mult;
  45         vdata->shift            = tk->tkr_mono.shift;
  46
  47         vdata->wall_time_sec            = tk->xtime_sec;
  48         vdata->wall_time_snsec          = tk->tkr_mono.xtime_nsec;
  49
  50         vdata->monotonic_time_sec       = tk->xtime_sec
  51                                         + tk->wall_to_monotonic.tv_sec;
  52         vdata->monotonic_time_snsec     = tk->tkr_mono.xtime_nsec
  53                                         + ((u64)tk->wall_to_monotonic.tv_nsec
  54                                                 << tk->tkr_mono.shift);
  55         while (vdata->monotonic_time_snsec >=
  56                                         (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  57                 vdata->monotonic_time_snsec -=
  58                                         ((u64)NSEC_PER_SEC) << tk->tkr_mono.shift;
  59                 vdata->monotonic_time_sec++;
  60         }
  61
  62         vdata->wall_time_coarse_sec     = tk->xtime_sec;
  63         vdata->wall_time_coarse_nsec    = (long)(tk->tkr_mono.xtime_nsec >>
  64                                                  tk->tkr_mono.shift);
  65
  66         vdata->monotonic_time_coarse_sec =
  67                 vdata->wall_time_coarse_sec + tk->wall_to_monotonic.tv_sec;
  68         vdata->monotonic_time_coarse_nsec =
  69                 vdata->wall_time_coarse_nsec + tk->wall_to_monotonic.tv_nsec;
  70
  71         while (vdata->monotonic_time_coarse_nsec >= NSEC_PER_SEC) {
  72                 vdata->monotonic_time_coarse_nsec -= NSEC_PER_SEC;
  73                 vdata->monotonic_time_coarse_sec++;
  74         }
  75
  76         gtod_write_end(vdata);
  77 }