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         struct vgtod_ts *base;
  35         u64 nsec;
  36
  37         /* Mark the new vclock used. */
  38         BUILD_BUG_ON(VCLOCK_MAX >= 32);
  39         WRITE_ONCE(vclocks_used, READ_ONCE(vclocks_used) | (1 << vclock_mode));
  40
  41         gtod_write_begin(vdata);
  42
  43         /* copy vsyscall data */
  44         vdata->vclock_mode      = vclock_mode;
  45         vdata->cycle_last       = tk->tkr_mono.cycle_last;
  46         vdata->mask             = tk->tkr_mono.mask;
  47         vdata->mult             = tk->tkr_mono.mult;
  48         vdata->shift            = tk->tkr_mono.shift;
  49
  50         base = &vdata->basetime[CLOCK_REALTIME];
  51         base->sec = tk->xtime_sec;
  52         base->nsec = tk->tkr_mono.xtime_nsec;
  53
  54         base = &vdata->basetime[CLOCK_TAI];
  55         base->sec = tk->xtime_sec + (s64)tk->tai_offset;
  56         base->nsec = tk->tkr_mono.xtime_nsec;
  57
  58         base = &vdata->basetime[CLOCK_MONOTONIC];
  59         base->sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
  60         nsec = tk->tkr_mono.xtime_nsec;
  61         nsec += ((u64)tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
  62         while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  63                 nsec -= ((u64)NSEC_PER_SEC) << tk->tkr_mono.shift;
  64                 base->sec++;
  65         }
  66         base->nsec = nsec;
  67
  68         base = &vdata->basetime[CLOCK_REALTIME_COARSE];
  69         base->sec = tk->xtime_sec;
  70         base->nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
  71
  72         base = &vdata->basetime[CLOCK_MONOTONIC_COARSE];
  73         base->sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
  74         nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
  75         nsec += tk->wall_to_monotonic.tv_nsec;
  76         while (nsec >= NSEC_PER_SEC) {
  77                 nsec -= NSEC_PER_SEC;
  78                 base->sec++;
  79         }
  80         base->nsec = nsec;
  81
  82         gtod_write_end(vdata);
  83 }