Merge branch 'linus' into tracing/mmiotrace
[linux-2.6.git] / 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 #include <linux/kernel.h>
13 #include <linux/posix-timers.h>
14 #include <linux/time.h>
15 #include <linux/string.h>
16 #include <asm/vsyscall.h>
17 #include <asm/vgtod.h>
18 #include <asm/timex.h>
19 #include <asm/hpet.h>
20 #include <asm/unistd.h>
21 #include <asm/io.h>
22 #include "vextern.h"
23
24 #define gtod vdso_vsyscall_gtod_data
25
26 notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
27 {
28         long ret;
29         asm("syscall" : "=a" (ret) :
30             "0" (__NR_clock_gettime),"D" (clock), "S" (ts) : "memory");
31         return ret;
32 }
33
34 notrace static inline long vgetns(void)
35 {
36         long v;
37         cycles_t (*vread)(void);
38         vread = gtod->clock.vread;
39         v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
40         return (v * gtod->clock.mult) >> gtod->clock.shift;
41 }
42
43 notrace static noinline int do_realtime(struct timespec *ts)
44 {
45         unsigned long seq, ns;
46         do {
47                 seq = read_seqbegin(&gtod->lock);
48                 ts->tv_sec = gtod->wall_time_sec;
49                 ts->tv_nsec = gtod->wall_time_nsec;
50                 ns = vgetns();
51         } while (unlikely(read_seqretry(&gtod->lock, seq)));
52         timespec_add_ns(ts, ns);
53         return 0;
54 }
55
56 /* Copy of the version in kernel/time.c which we cannot directly access */
57 notrace static void
58 vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
59 {
60         while (nsec >= NSEC_PER_SEC) {
61                 nsec -= NSEC_PER_SEC;
62                 ++sec;
63         }
64         while (nsec < 0) {
65                 nsec += NSEC_PER_SEC;
66                 --sec;
67         }
68         ts->tv_sec = sec;
69         ts->tv_nsec = nsec;
70 }
71
72 notrace static noinline int do_monotonic(struct timespec *ts)
73 {
74         unsigned long seq, ns, secs;
75         do {
76                 seq = read_seqbegin(&gtod->lock);
77                 secs = gtod->wall_time_sec;
78                 ns = gtod->wall_time_nsec + vgetns();
79                 secs += gtod->wall_to_monotonic.tv_sec;
80                 ns += gtod->wall_to_monotonic.tv_nsec;
81         } while (unlikely(read_seqretry(&gtod->lock, seq)));
82         vset_normalized_timespec(ts, secs, ns);
83         return 0;
84 }
85
86 notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
87 {
88         if (likely(gtod->sysctl_enabled && gtod->clock.vread))
89                 switch (clock) {
90                 case CLOCK_REALTIME:
91                         return do_realtime(ts);
92                 case CLOCK_MONOTONIC:
93                         return do_monotonic(ts);
94                 }
95         return vdso_fallback_gettime(clock, ts);
96 }
97 int clock_gettime(clockid_t, struct timespec *)
98         __attribute__((weak, alias("__vdso_clock_gettime")));
99
100 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
101 {
102         long ret;
103         if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
104                 BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
105                              offsetof(struct timespec, tv_nsec) ||
106                              sizeof(*tv) != sizeof(struct timespec));
107                 do_realtime((struct timespec *)tv);
108                 tv->tv_usec /= 1000;
109                 if (unlikely(tz != NULL)) {
110                         /* Avoid memcpy. Some old compilers fail to inline it */
111                         tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;
112                         tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
113                 }
114                 return 0;
115         }
116         asm("syscall" : "=a" (ret) :
117             "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
118         return ret;
119 }
120 int gettimeofday(struct timeval *, struct timezone *)
121         __attribute__((weak, alias("__vdso_gettimeofday")));