arch/x86/vdso/vclock_gettime.c

   1 /*
   2  * Copyright 2006 Andi Kleen, SUSE Labs.
   3  * Subject to the GNU Public License, v.2
   4  *
   5  * Fast user context implementation of clock_gettime and gettimeofday.
   6  *
   7  * The code should have no internal unresolved relocations.
   8  * Check with readelf after changing.
   9  * Also alternative() doesn't work.
  10  */
  11
  12 /* Disable profiling for userspace code: */
  13 #define DISABLE_BRANCH_PROFILING
  14
  15 #include <linux/kernel.h>
  16 #include <linux/posix-timers.h>
  17 #include <linux/time.h>
  18 #include <linux/string.h>
  19 #include <asm/vsyscall.h>
  20 #include <asm/vgtod.h>
  21 #include <asm/timex.h>
  22 #include <asm/hpet.h>
  23 #include <asm/unistd.h>
  24 #include <asm/io.h>
  25 #include "vextern.h"
  26
  27 #define gtod vdso_vsyscall_gtod_data
  28
  29 notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
  30 {
  31         long ret;
  32         asm("syscall" : "=a" (ret) :
  33             "0" (__NR_clock_gettime),"D" (clock), "S" (ts) : "memory");
  34         return ret;
  35 }
  36
  37 notrace static inline long vgetns(void)
  38 {
  39         long v;
  40         cycles_t (*vread)(void);
  41         vread = gtod->clock.vread;
  42         v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
  43         return (v * gtod->clock.mult) >> gtod->clock.shift;
  44 }
  45
  46 notrace static noinline int do_realtime(struct timespec *ts)
  47 {
  48         unsigned long seq, ns;
  49         do {
  50                 seq = read_seqbegin(&gtod->lock);
  51                 ts->tv_sec = gtod->wall_time_sec;
  52                 ts->tv_nsec = gtod->wall_time_nsec;
  53                 ns = vgetns();
  54         } while (unlikely(read_seqretry(&gtod->lock, seq)));
  55         timespec_add_ns(ts, ns);
  56         return 0;
  57 }
  58
  59 /* Copy of the version in kernel/time.c which we cannot directly access */
  60 notrace static void
  61 vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
  62 {
  63         while (nsec >= NSEC_PER_SEC) {
  64                 nsec -= NSEC_PER_SEC;
  65                 ++sec;
  66         }
  67         while (nsec < 0) {
  68                 nsec += NSEC_PER_SEC;
  69                 --sec;
  70         }
  71         ts->tv_sec = sec;
  72         ts->tv_nsec = nsec;
  73 }
  74
  75 notrace static noinline int do_monotonic(struct timespec *ts)
  76 {
  77         unsigned long seq, ns, secs;
  78         do {
  79                 seq = read_seqbegin(&gtod->lock);
  80                 secs = gtod->wall_time_sec;
  81                 ns = gtod->wall_time_nsec + vgetns();
  82                 secs += gtod->wall_to_monotonic.tv_sec;
  83                 ns += gtod->wall_to_monotonic.tv_nsec;
  84         } while (unlikely(read_seqretry(&gtod->lock, seq)));
  85         vset_normalized_timespec(ts, secs, ns);
  86         return 0;
  87 }
  88
  89 notrace static noinline int do_realtime_coarse(struct timespec *ts)
  90 {
  91         unsigned long seq;
  92         do {
  93                 seq = read_seqbegin(&gtod->lock);
  94                 ts->tv_sec = gtod->wall_time_coarse.tv_sec;
  95                 ts->tv_nsec = gtod->wall_time_coarse.tv_nsec;
  96         } while (unlikely(read_seqretry(&gtod->lock, seq)));
  97         return 0;
  98 }
  99
 100 notrace static noinline int do_monotonic_coarse(struct timespec *ts)
 101 {
 102         unsigned long seq, ns, secs;
 103         do {
 104                 seq = read_seqbegin(&gtod->lock);
 105                 secs = gtod->wall_time_coarse.tv_sec;
 106                 ns = gtod->wall_time_coarse.tv_nsec;
 107                 secs += gtod->wall_to_monotonic.tv_sec;
 108                 ns += gtod->wall_to_monotonic.tv_nsec;
 109         } while (unlikely(read_seqretry(&gtod->lock, seq)));
 110         vset_normalized_timespec(ts, secs, ns);
 111         return 0;
 112 }
 113
 114 notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 115 {
 116         if (likely(gtod->sysctl_enabled))
 117                 switch (clock) {
 118                 case CLOCK_REALTIME:
 119                         if (likely(gtod->clock.vread))
 120                                 return do_realtime(ts);
 121                         break;
 122                 case CLOCK_MONOTONIC:
 123                         if (likely(gtod->clock.vread))
 124                                 return do_monotonic(ts);
 125                         break;
 126                 case CLOCK_REALTIME_COARSE:
 127                         return do_realtime_coarse(ts);
 128                 case CLOCK_MONOTONIC_COARSE:
 129                         return do_monotonic_coarse(ts);
 130                 }
 131         return vdso_fallback_gettime(clock, ts);
 132 }
 133 int clock_gettime(clockid_t, struct timespec *)
 134         __attribute__((weak, alias("__vdso_clock_gettime")));
 135
 136 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 137 {
 138         long ret;
 139         if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
 140                 if (likely(tv != NULL)) {
 141                         BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
 142                                      offsetof(struct timespec, tv_nsec) ||
 143                                      sizeof(*tv) != sizeof(struct timespec));
 144                         do_realtime((struct timespec *)tv);
 145                         tv->tv_usec /= 1000;
 146                 }
 147                 if (unlikely(tz != NULL)) {
 148                         /* Avoid memcpy. Some old compilers fail to inline it */
 149                         tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;
 150                         tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
 151                 }
 152                 return 0;
 153         }
 154         asm("syscall" : "=a" (ret) :
 155             "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
 156         return ret;
 157 }
 158 int gettimeofday(struct timeval *, struct timezone *)
 159         __attribute__((weak, alias("__vdso_gettimeofday")));