kernel/time/vsyscall.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2019 ARM Ltd.
   4  *
   5  * Generic implementation of update_vsyscall and update_vsyscall_tz.
   6  *
   7  * Based on the x86 specific implementation.
   8  */
   9
  10 #include <linux/hrtimer.h>
  11 #include <linux/timekeeper_internal.h>
  12 #include <vdso/datapage.h>
  13 #include <vdso/helpers.h>
  14 #include <vdso/vsyscall.h>
  15
  16 static inline void update_vdso_data(struct vdso_data *vdata,
  17                                     struct timekeeper *tk)
  18 {
  19         struct vdso_timestamp *vdso_ts;
  20         u64 nsec, sec;
  21
  22         vdata[CS_HRES_COARSE].cycle_last        = tk->tkr_mono.cycle_last;
  23         vdata[CS_HRES_COARSE].mask              = tk->tkr_mono.mask;
  24         vdata[CS_HRES_COARSE].mult              = tk->tkr_mono.mult;
  25         vdata[CS_HRES_COARSE].shift             = tk->tkr_mono.shift;
  26         vdata[CS_RAW].cycle_last                = tk->tkr_raw.cycle_last;
  27         vdata[CS_RAW].mask                      = tk->tkr_raw.mask;
  28         vdata[CS_RAW].mult                      = tk->tkr_raw.mult;
  29         vdata[CS_RAW].shift                     = tk->tkr_raw.shift;
  30
  31         /* CLOCK_REALTIME */
  32         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
  33         vdso_ts->sec    = tk->xtime_sec;
  34         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec;
  35
  36         /* CLOCK_MONOTONIC */
  37         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC];
  38         vdso_ts->sec    = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
  39
  40         nsec = tk->tkr_mono.xtime_nsec;
  41         nsec += ((u64)tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
  42         while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  43                 nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
  44                 vdso_ts->sec++;
  45         }
  46         vdso_ts->nsec   = nsec;
  47
  48         /* Copy MONOTONIC time for BOOTTIME */
  49         sec     = vdso_ts->sec;
  50         /* Add the boot offset */
  51         sec     += tk->monotonic_to_boot.tv_sec;
  52         nsec    += (u64)tk->monotonic_to_boot.tv_nsec << tk->tkr_mono.shift;
  53
  54         /* CLOCK_BOOTTIME */
  55         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_BOOTTIME];
  56         vdso_ts->sec    = sec;
  57
  58         while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  59                 nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
  60                 vdso_ts->sec++;
  61         }
  62         vdso_ts->nsec   = nsec;
  63
  64         /* CLOCK_MONOTONIC_RAW */
  65         vdso_ts         = &vdata[CS_RAW].basetime[CLOCK_MONOTONIC_RAW];
  66         vdso_ts->sec    = tk->raw_sec;
  67         vdso_ts->nsec   = tk->tkr_raw.xtime_nsec;
  68
  69         /* CLOCK_TAI */
  70         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_TAI];
  71         vdso_ts->sec    = tk->xtime_sec + (s64)tk->tai_offset;
  72         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec;
  73
  74         /*
  75          * Read without the seqlock held by clock_getres().
  76          * Note: No need to have a second copy.
  77          */
  78         WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);
  79 }
  80
  81 void update_vsyscall(struct timekeeper *tk)
  82 {
  83         struct vdso_data *vdata = __arch_get_k_vdso_data();
  84         struct vdso_timestamp *vdso_ts;
  85         u64 nsec;
  86
  87         if (__arch_update_vdso_data()) {
  88                 /*
  89                  * Some architectures might want to skip the update of the
  90                  * data page.
  91                  */
  92                 return;
  93         }
  94
  95         /* copy vsyscall data */
  96         vdso_write_begin(vdata);
  97
  98         vdata[CS_HRES_COARSE].clock_mode        = __arch_get_clock_mode(tk);
  99         vdata[CS_RAW].clock_mode                = __arch_get_clock_mode(tk);
 100
 101         /* CLOCK_REALTIME_COARSE */
 102         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE];
 103         vdso_ts->sec    = tk->xtime_sec;
 104         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
 105
 106         /* CLOCK_MONOTONIC_COARSE */
 107         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC_COARSE];
 108         vdso_ts->sec    = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
 109         nsec            = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
 110         nsec            = nsec + tk->wall_to_monotonic.tv_nsec;
 111         vdso_ts->sec    += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
 112
 113         update_vdso_data(vdata, tk);
 114
 115         __arch_update_vsyscall(vdata, tk);
 116
 117         vdso_write_end(vdata);
 118
 119         __arch_sync_vdso_data(vdata);
 120 }
 121
 122 void update_vsyscall_tz(void)
 123 {
 124         struct vdso_data *vdata = __arch_get_k_vdso_data();
 125
 126         vdata[CS_HRES_COARSE].tz_minuteswest = sys_tz.tz_minuteswest;
 127         vdata[CS_HRES_COARSE].tz_dsttime = sys_tz.tz_dsttime;
 128
 129         __arch_sync_vdso_data(vdata);
 130 }