arch/arm/vdso/vgettimeofday.c

   1 /*
   2  * Userspace implementations of gettimeofday() and friends.
   3  *
   4  * Copyright (C) 2017 Cavium, Inc.
   5  * Copyright (C) 2015 Mentor Graphics Corporation
   6  * Copyright (C) 2012 ARM Limited
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19  *
  20  * Author: Will Deacon <will.deacon@arm.com>
  21  * Rewriten from arch64 version into C by: Andrew Pinski <apinski@cavium.com>
  22  * Reworked and rebased over arm version by: Mark Salyzyn <salyzyn@android.com>
  23  */
  24
  25 #include <asm/barrier.h>
  26 #include <linux/compiler.h>     /* for notrace                          */
  27 #include <linux/math64.h>       /* for __iter_div_u64_rem()             */
  28 #include <uapi/linux/time.h>    /* for struct timespec                  */
  29
  30 #include "compiler.h"
  31 #include "datapage.h"
  32
  33 DEFINE_FALLBACK(gettimeofday, struct timeval *, tv, struct timezone *, tz)
  34 DEFINE_FALLBACK(clock_gettime, clockid_t, clock, struct timespec *, ts)
  35
  36 static notrace u32 vdso_read_begin(const struct vdso_data *vd)
  37 {
  38         u32 seq;
  39
  40         do {
  41                 seq = READ_ONCE(vd->tb_seq_count);
  42
  43                 if ((seq & 1) == 0)
  44                         break;
  45
  46                 cpu_relax();
  47         } while (true);
  48
  49         smp_rmb(); /* Pairs with second smp_wmb in update_vsyscall */
  50         return seq;
  51 }
  52
  53 static notrace int vdso_read_retry(const struct vdso_data *vd, u32 start)
  54 {
  55         u32 seq;
  56
  57         smp_rmb(); /* Pairs with first smp_wmb in update_vsyscall */
  58         seq = READ_ONCE(vd->tb_seq_count);
  59         return seq != start;
  60 }
  61
  62 static notrace int do_realtime_coarse(const struct vdso_data *vd,
  63                                       struct timespec *ts)
  64 {
  65         u32 seq;
  66
  67         do {
  68                 seq = vdso_read_begin(vd);
  69
  70                 ts->tv_sec = vd->xtime_coarse_sec;
  71                 ts->tv_nsec = vd->xtime_coarse_nsec;
  72
  73         } while (vdso_read_retry(vd, seq));
  74
  75         return 0;
  76 }
  77
  78 static notrace int do_monotonic_coarse(const struct vdso_data *vd,
  79                                        struct timespec *ts)
  80 {
  81         struct timespec tomono;
  82         u32 seq;
  83         u64 nsec;
  84
  85         do {
  86                 seq = vdso_read_begin(vd);
  87
  88                 ts->tv_sec = vd->xtime_coarse_sec;
  89                 ts->tv_nsec = vd->xtime_coarse_nsec;
  90
  91                 tomono.tv_sec = vd->wtm_clock_sec;
  92                 tomono.tv_nsec = vd->wtm_clock_nsec;
  93
  94         } while (vdso_read_retry(vd, seq));
  95
  96         ts->tv_sec += tomono.tv_sec;
  97         /* open coding timespec_add_ns */
  98         ts->tv_sec += __iter_div_u64_rem(ts->tv_nsec + tomono.tv_nsec,
  99                                          NSEC_PER_SEC, &nsec);
 100         ts->tv_nsec = nsec;
 101
 102         return 0;
 103 }
 104
 105 #ifdef CONFIG_ARM_ARCH_TIMER
 106
 107 /*
 108  * Returns the clock delta, in nanoseconds left-shifted by the clock
 109  * shift.
 110  */
 111 static notrace u64 get_clock_shifted_nsec(const u64 cycle_last,
 112                                           const u32 mult,
 113                                           const u64 mask)
 114 {
 115         u64 res;
 116
 117         /* Read the virtual counter. */
 118         res = arch_vdso_read_counter();
 119
 120         res = res - cycle_last;
 121
 122         res &= mask;
 123         return res * mult;
 124 }
 125
 126 static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
 127 {
 128         u32 seq, mult, shift;
 129         u64 nsec, cycle_last;
 130         u64 mask;
 131         vdso_xtime_clock_sec_t sec;
 132
 133         do {
 134                 seq = vdso_read_begin(vd);
 135
 136                 if (vd->use_syscall)
 137                         return -1;
 138
 139                 cycle_last = vd->cs_cycle_last;
 140
 141                 mult = vd->cs_mono_mult;
 142                 shift = vd->cs_shift;
 143                 mask = vd->cs_mask;
 144
 145                 sec = vd->xtime_clock_sec;
 146                 nsec = vd->xtime_clock_snsec;
 147
 148         } while (unlikely(vdso_read_retry(vd, seq)));
 149
 150         nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
 151         nsec >>= shift;
 152         /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
 153         ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
 154         ts->tv_nsec = nsec;
 155
 156         return 0;
 157 }
 158
 159 static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
 160 {
 161         u32 seq, mult, shift;
 162         u64 nsec, cycle_last;
 163         u64 mask;
 164         vdso_wtm_clock_nsec_t wtm_nsec;
 165         __kernel_time_t sec;
 166
 167         do {
 168                 seq = vdso_read_begin(vd);
 169
 170                 if (vd->use_syscall)
 171                         return -1;
 172
 173                 cycle_last = vd->cs_cycle_last;
 174
 175                 mult = vd->cs_mono_mult;
 176                 shift = vd->cs_shift;
 177                 mask = vd->cs_mask;
 178
 179                 sec = vd->xtime_clock_sec;
 180                 nsec = vd->xtime_clock_snsec;
 181
 182                 sec += vd->wtm_clock_sec;
 183                 wtm_nsec = vd->wtm_clock_nsec;
 184
 185         } while (unlikely(vdso_read_retry(vd, seq)));
 186
 187         nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
 188         nsec >>= shift;
 189         nsec += wtm_nsec;
 190         /* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
 191         ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
 192         ts->tv_nsec = nsec;
 193
 194         return 0;
 195 }
 196
 197 #else /* CONFIG_ARM_ARCH_TIMER */
 198
 199 static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
 200 {
 201         return -1;
 202 }
 203
 204 static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
 205 {
 206         return -1;
 207 }
 208
 209 #endif /* CONFIG_ARM_ARCH_TIMER */
 210
 211 notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 212 {
 213         const struct vdso_data *vd = __get_datapage();
 214
 215         switch (clock) {
 216         case CLOCK_REALTIME_COARSE:
 217                 do_realtime_coarse(vd, ts);
 218                 break;
 219         case CLOCK_MONOTONIC_COARSE:
 220                 do_monotonic_coarse(vd, ts);
 221                 break;
 222         case CLOCK_REALTIME:
 223                 if (do_realtime(vd, ts))
 224                         goto fallback;
 225                 break;
 226         case CLOCK_MONOTONIC:
 227                 if (do_monotonic(vd, ts))
 228                         goto fallback;
 229                 break;
 230         default:
 231                 goto fallback;
 232         }
 233
 234         return 0;
 235 fallback:
 236         return clock_gettime_fallback(clock, ts);
 237 }
 238
 239 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 240 {
 241         const struct vdso_data *vd = __get_datapage();
 242
 243         if (likely(tv != NULL)) {
 244                 struct timespec ts;
 245
 246                 if (do_realtime(vd, &ts))
 247                         return gettimeofday_fallback(tv, tz);
 248
 249                 tv->tv_sec = ts.tv_sec;
 250                 tv->tv_usec = ts.tv_nsec / 1000;
 251         }
 252
 253         if (unlikely(tz != NULL)) {
 254                 tz->tz_minuteswest = vd->tz_minuteswest;
 255                 tz->tz_dsttime = vd->tz_dsttime;
 256         }
 257
 258         return 0;
 259 }