LXR linux/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
  16static 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
  81void 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        if (__arch_use_vsyscall(vdata))
 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
 123void update_vsyscall_tz(void)
 124{
 125        struct vdso_data *vdata = __arch_get_k_vdso_data();
 126
 127        if (__arch_use_vsyscall(vdata)) {
 128                vdata[CS_HRES_COARSE].tz_minuteswest = sys_tz.tz_minuteswest;
 129                vdata[CS_HRES_COARSE].tz_dsttime = sys_tz.tz_dsttime;
 130        }
 131
 132        __arch_sync_vdso_data(vdata);
 133}
 134