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_MONOTONIC */
  32         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC];
  33         vdso_ts->sec    = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
  34
  35         nsec = tk->tkr_mono.xtime_nsec;
  36         nsec += ((u64)tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
  37         while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  38                 nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
  39                 vdso_ts->sec++;
  40         }
  41         vdso_ts->nsec   = nsec;
  42
  43         /* Copy MONOTONIC time for BOOTTIME */
  44         sec     = vdso_ts->sec;
  45         /* Add the boot offset */
  46         sec     += tk->monotonic_to_boot.tv_sec;
  47         nsec    += (u64)tk->monotonic_to_boot.tv_nsec << tk->tkr_mono.shift;
  48
  49         /* CLOCK_BOOTTIME */
  50         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_BOOTTIME];
  51         vdso_ts->sec    = sec;
  52
  53         while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  54                 nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
  55                 vdso_ts->sec++;
  56         }
  57         vdso_ts->nsec   = nsec;
  58
  59         /* CLOCK_MONOTONIC_RAW */
  60         vdso_ts         = &vdata[CS_RAW].basetime[CLOCK_MONOTONIC_RAW];
  61         vdso_ts->sec    = tk->raw_sec;
  62         vdso_ts->nsec   = tk->tkr_raw.xtime_nsec;
  63
  64         /* CLOCK_TAI */
  65         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_TAI];
  66         vdso_ts->sec    = tk->xtime_sec + (s64)tk->tai_offset;
  67         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec;
  68 }
  69
  70 void update_vsyscall(struct timekeeper *tk)
  71 {
  72         struct vdso_data *vdata = __arch_get_k_vdso_data();
  73         struct vdso_timestamp *vdso_ts;
  74         u64 nsec;
  75
  76         /* copy vsyscall data */
  77         vdso_write_begin(vdata);
  78
  79         vdata[CS_HRES_COARSE].clock_mode        = __arch_get_clock_mode(tk);
  80         vdata[CS_RAW].clock_mode                = __arch_get_clock_mode(tk);
  81
  82         /* CLOCK_REALTIME also required for time() */
  83         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
  84         vdso_ts->sec    = tk->xtime_sec;
  85         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec;
  86
  87         /* CLOCK_REALTIME_COARSE */
  88         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE];
  89         vdso_ts->sec    = tk->xtime_sec;
  90         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
  91
  92         /* CLOCK_MONOTONIC_COARSE */
  93         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC_COARSE];
  94         vdso_ts->sec    = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
  95         nsec            = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
  96         nsec            = nsec + tk->wall_to_monotonic.tv_nsec;
  97         vdso_ts->sec    += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
  98
  99         /*
 100          * Read without the seqlock held by clock_getres().
 101          * Note: No need to have a second copy.
 102          */
 103         WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);
 104
 105         /*
 106          * Architectures can opt out of updating the high resolution part
 107          * of the VDSO.
 108          */
 109         if (__arch_update_vdso_data())
 110                 update_vdso_data(vdata, tk);
 111
 112         __arch_update_vsyscall(vdata, tk);
 113
 114         vdso_write_end(vdata);
 115
 116         __arch_sync_vdso_data(vdata);
 117 }
 118
 119 void update_vsyscall_tz(void)
 120 {
 121         struct vdso_data *vdata = __arch_get_k_vdso_data();
 122
 123         vdata[CS_HRES_COARSE].tz_minuteswest = sys_tz.tz_minuteswest;
 124         vdata[CS_HRES_COARSE].tz_dsttime = sys_tz.tz_dsttime;
 125
 126         __arch_sync_vdso_data(vdata);
 127 }