blob: 23476c2ebfc4b38b817e5907e0c658e7d21a6715 [file] [log] [blame]
Andi Kleen2aae9502007-07-21 17:10:01 +02001/*
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>
Andi Kleen2aae9502007-07-21 17:10:01 +020022#include "vextern.h"
23
24#define gtod vdso_vsyscall_gtod_data
25
26static 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
34static inline long vgetns(void)
35{
Andi Kleen95b08672007-09-11 14:02:09 +020036 long v;
Andi Kleen2aae9502007-07-21 17:10:01 +020037 cycles_t (*vread)(void);
38 vread = gtod->clock.vread;
Andi Kleen95b08672007-09-11 14:02:09 +020039 v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
40 return (v * gtod->clock.mult) >> gtod->clock.shift;
Andi Kleen2aae9502007-07-21 17:10:01 +020041}
42
43static 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 */
57static 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
71static 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
85int __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}
96int clock_gettime(clockid_t, struct timespec *)
97 __attribute__((weak, alias("__vdso_clock_gettime")));
98
99int __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 /* This relies on gcc inlining the memcpy. We'll notice
110 if it ever fails to do so. */
111 memcpy(tz, &gtod->sys_tz, sizeof(struct timezone));
112 }
113 return 0;
114 }
115 asm("syscall" : "=a" (ret) :
116 "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
117 return ret;
118}
119int gettimeofday(struct timeval *, struct timezone *)
120 __attribute__((weak, alias("__vdso_gettimeofday")));