arch/x86/entry/vsyscall/vsyscall_gtod.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
   4  *  Copyright 2003 Andi Kleen, SuSE Labs.
   5  *
   6  *  Modified for x86 32 bit architecture by
   7  *  Stefani Seibold <stefani@seibold.net>
   8  *  sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
   9  *
  10  *  Thanks to hpa@transmeta.com for some useful hint.
  11  *  Special thanks to Ingo Molnar for his early experience with
  12  *  a different vsyscall implementation for Linux/IA32 and for the name.
  13  *
  14  */
  15
  16 #include <linux/timekeeper_internal.h>
  17 #include <asm/vgtod.h>
  18 #include <asm/vvar.h>
  19
  20 int vclocks_used __read_mostly;
  21
  22 DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);
  23
  24 void update_vsyscall_tz(void)
  25 {
  26         vsyscall_gtod_data.tz_minuteswest = sys_tz.tz_minuteswest;
  27         vsyscall_gtod_data.tz_dsttime = sys_tz.tz_dsttime;
  28 }
  29
  30 void update_vsyscall(struct timekeeper *tk)
  31 {
  32         int vclock_mode = tk->tkr_mono.clock->archdata.vclock_mode;
  33         struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;
  34
  35         /* Mark the new vclock used. */
  36         BUILD_BUG_ON(VCLOCK_MAX >= 32);
  37         WRITE_ONCE(vclocks_used, READ_ONCE(vclocks_used) | (1 << vclock_mode));
  38
  39         gtod_write_begin(vdata);
  40
  41         /* copy vsyscall data */
  42         vdata->vclock_mode      = vclock_mode;
  43         vdata->cycle_last       = tk->tkr_mono.cycle_last;
  44         vdata->mask             = tk->tkr_mono.mask;
  45         vdata->mult             = tk->tkr_mono.mult;
  46         vdata->shift            = tk->tkr_mono.shift;
  47
  48         vdata->wall_time_sec            = tk->xtime_sec;
  49         vdata->wall_time_snsec          = tk->tkr_mono.xtime_nsec;
  50
  51         vdata->monotonic_time_sec       = tk->xtime_sec
  52                                         + tk->wall_to_monotonic.tv_sec;
  53         vdata->monotonic_time_snsec     = tk->tkr_mono.xtime_nsec
  54                                         + ((u64)tk->wall_to_monotonic.tv_nsec
  55                                                 << tk->tkr_mono.shift);
  56         while (vdata->monotonic_time_snsec >=
  57                                         (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  58                 vdata->monotonic_time_snsec -=
  59                                         ((u64)NSEC_PER_SEC) << tk->tkr_mono.shift;
  60                 vdata->monotonic_time_sec++;
  61         }
  62
  63         vdata->wall_time_coarse_sec     = tk->xtime_sec;
  64         vdata->wall_time_coarse_nsec    = (long)(tk->tkr_mono.xtime_nsec >>
  65                                                  tk->tkr_mono.shift);
  66
  67         vdata->monotonic_time_coarse_sec =
  68                 vdata->wall_time_coarse_sec + tk->wall_to_monotonic.tv_sec;
  69         vdata->monotonic_time_coarse_nsec =
  70                 vdata->wall_time_coarse_nsec + tk->wall_to_monotonic.tv_nsec;
  71
  72         while (vdata->monotonic_time_coarse_nsec >= NSEC_PER_SEC) {
  73                 vdata->monotonic_time_coarse_nsec -= NSEC_PER_SEC;
  74                 vdata->monotonic_time_coarse_sec++;
  75         }
  76
  77         gtod_write_end(vdata);
  78 }