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 #include "timekeeping_internal.h"
  17
  18 static inline void update_vdso_data(struct vdso_data *vdata,
  19                                     struct timekeeper *tk)
  20 {
  21         struct vdso_timestamp *vdso_ts;
  22         u64 nsec, sec;
  23
  24         vdata[CS_HRES_COARSE].cycle_last        = tk->tkr_mono.cycle_last;
  25         vdata[CS_HRES_COARSE].mask              = tk->tkr_mono.mask;
  26         vdata[CS_HRES_COARSE].mult              = tk->tkr_mono.mult;
  27         vdata[CS_HRES_COARSE].shift             = tk->tkr_mono.shift;
  28         vdata[CS_RAW].cycle_last                = tk->tkr_raw.cycle_last;
  29         vdata[CS_RAW].mask                      = tk->tkr_raw.mask;
  30         vdata[CS_RAW].mult                      = tk->tkr_raw.mult;
  31         vdata[CS_RAW].shift                     = tk->tkr_raw.shift;
  32
  33         /* CLOCK_MONOTONIC */
  34         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC];
  35         vdso_ts->sec    = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
  36
  37         nsec = tk->tkr_mono.xtime_nsec;
  38         nsec += ((u64)tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
  39         while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  40                 nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
  41                 vdso_ts->sec++;
  42         }
  43         vdso_ts->nsec   = nsec;
  44
  45         /* Copy MONOTONIC time for BOOTTIME */
  46         sec     = vdso_ts->sec;
  47         /* Add the boot offset */
  48         sec     += tk->monotonic_to_boot.tv_sec;
  49         nsec    += (u64)tk->monotonic_to_boot.tv_nsec << tk->tkr_mono.shift;
  50
  51         /* CLOCK_BOOTTIME */
  52         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_BOOTTIME];
  53         vdso_ts->sec    = sec;
  54
  55         while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
  56                 nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
  57                 vdso_ts->sec++;
  58         }
  59         vdso_ts->nsec   = nsec;
  60
  61         /* CLOCK_MONOTONIC_RAW */
  62         vdso_ts         = &vdata[CS_RAW].basetime[CLOCK_MONOTONIC_RAW];
  63         vdso_ts->sec    = tk->raw_sec;
  64         vdso_ts->nsec   = tk->tkr_raw.xtime_nsec;
  65
  66         /* CLOCK_TAI */
  67         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_TAI];
  68         vdso_ts->sec    = tk->xtime_sec + (s64)tk->tai_offset;
  69         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec;
  70 }
  71
  72 void update_vsyscall(struct timekeeper *tk)
  73 {
  74         struct vdso_data *vdata = __arch_get_k_vdso_data();
  75         struct vdso_timestamp *vdso_ts;
  76         s32 clock_mode;
  77         u64 nsec;
  78
  79         /* copy vsyscall data */
  80         vdso_write_begin(vdata);
  81
  82         clock_mode = tk->tkr_mono.clock->vdso_clock_mode;
  83         vdata[CS_HRES_COARSE].clock_mode        = clock_mode;
  84         vdata[CS_RAW].clock_mode                = clock_mode;
  85
  86         /* CLOCK_REALTIME also required for time() */
  87         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
  88         vdso_ts->sec    = tk->xtime_sec;
  89         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec;
  90
  91         /* CLOCK_REALTIME_COARSE */
  92         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE];
  93         vdso_ts->sec    = tk->xtime_sec;
  94         vdso_ts->nsec   = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
  95
  96         /* CLOCK_MONOTONIC_COARSE */
  97         vdso_ts         = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC_COARSE];
  98         vdso_ts->sec    = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
  99         nsec            = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
 100         nsec            = nsec + tk->wall_to_monotonic.tv_nsec;
 101         vdso_ts->sec    += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
 102
 103         /*
 104          * Read without the seqlock held by clock_getres().
 105          * Note: No need to have a second copy.
 106          */
 107         WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);
 108
 109         /*
 110          * If the current clocksource is not VDSO capable, then spare the
 111          * update of the high reolution parts.
 112          */
 113         if (clock_mode != VDSO_CLOCKMODE_NONE)
 114                 update_vdso_data(vdata, tk);
 115
 116         __arch_update_vsyscall(vdata, tk);
 117
 118         vdso_write_end(vdata);
 119
 120         __arch_sync_vdso_data(vdata);
 121 }
 122
 123 void update_vsyscall_tz(void)
 124 {
 125         struct vdso_data *vdata = __arch_get_k_vdso_data();
 126
 127         vdata[CS_HRES_COARSE].tz_minuteswest = sys_tz.tz_minuteswest;
 128         vdata[CS_HRES_COARSE].tz_dsttime = sys_tz.tz_dsttime;
 129
 130         __arch_sync_vdso_data(vdata);
 131 }
 132
 133 /**
 134  * vdso_update_begin - Start of a VDSO update section
 135  *
 136  * Allows architecture code to safely update the architecture specific VDSO
 137  * data. Disables interrupts, acquires timekeeper lock to serialize against
 138  * concurrent updates from timekeeping and invalidates the VDSO data
 139  * sequence counter to prevent concurrent readers from accessing
 140  * inconsistent data.
 141  *
 142  * Returns: Saved interrupt flags which need to be handed in to
 143  * vdso_update_end().
 144  */
 145 unsigned long vdso_update_begin(void)
 146 {
 147         struct vdso_data *vdata = __arch_get_k_vdso_data();
 148         unsigned long flags;
 149
 150         raw_spin_lock_irqsave(&timekeeper_lock, flags);
 151         vdso_write_begin(vdata);
 152         return flags;
 153 }
 154
 155 /**
 156  * vdso_update_end - End of a VDSO update section
 157  * @flags:      Interrupt flags as returned from vdso_update_begin()
 158  *
 159  * Pairs with vdso_update_begin(). Marks vdso data consistent, invokes data
 160  * synchronization if the architecture requires it, drops timekeeper lock
 161  * and restores interrupt flags.
 162  */
 163 void vdso_update_end(unsigned long flags)
 164 {
 165         struct vdso_data *vdata = __arch_get_k_vdso_data();
 166
 167         vdso_write_end(vdata);
 168         __arch_sync_vdso_data(vdata);
 169         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
 170 }