Merge branch 'linus' into x86/nmi
[linux-2.6] / 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 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 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 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 static void vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
58 {
59         while (nsec >= NSEC_PER_SEC) {
60                 nsec -= NSEC_PER_SEC;
61                 ++sec;
62         }
63         while (nsec < 0) {
64                 nsec += NSEC_PER_SEC;
65                 --sec;
66         }
67         ts->tv_sec = sec;
68         ts->tv_nsec = nsec;
69 }
70
71 static noinline int do_monotonic(struct timespec *ts)
72 {
73         unsigned long seq, ns, secs;
74         do {
75                 seq = read_seqbegin(&gtod->lock);
76                 secs = gtod->wall_time_sec;
77                 ns = gtod->wall_time_nsec + vgetns();
78                 secs += gtod->wall_to_monotonic.tv_sec;
79                 ns += gtod->wall_to_monotonic.tv_nsec;
80         } while (unlikely(read_seqretry(&gtod->lock, seq)));
81         vset_normalized_timespec(ts, secs, ns);
82         return 0;
83 }
84
85 int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
86 {
87         if (likely(gtod->sysctl_enabled && gtod->clock.vread))
88                 switch (clock) {
89                 case CLOCK_REALTIME:
90                         return do_realtime(ts);
91                 case CLOCK_MONOTONIC:
92                         return do_monotonic(ts);
93                 }
94         return vdso_fallback_gettime(clock, ts);
95 }
96 int clock_gettime(clockid_t, struct timespec *)
97         __attribute__((weak, alias("__vdso_clock_gettime")));
98
99 int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
100 {
101         long ret;
102         if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
103                 BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
104                              offsetof(struct timespec, tv_nsec) ||
105                              sizeof(*tv) != sizeof(struct timespec));
106                 do_realtime((struct timespec *)tv);
107                 tv->tv_usec /= 1000;
108                 if (unlikely(tz != NULL)) {
109                         /* Avoid memcpy. Some old compilers fail to inline it */
110                         tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;
111                         tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
112                 }
113                 return 0;
114         }
115         asm("syscall" : "=a" (ret) :
116             "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
117         return ret;
118 }
119 int gettimeofday(struct timeval *, struct timezone *)
120         __attribute__((weak, alias("__vdso_gettimeofday")));