121 lines
3.1 KiB
C
121 lines
3.1 KiB
C
/*
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* Copyright 2006 Andi Kleen, SUSE Labs.
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* Subject to the GNU Public License, v.2
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*
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* Fast user context implementation of clock_gettime and gettimeofday.
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*
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* The code should have no internal unresolved relocations.
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* Check with readelf after changing.
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* Also alternative() doesn't work.
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*/
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#include <linux/kernel.h>
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#include <linux/posix-timers.h>
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#include <linux/time.h>
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#include <linux/string.h>
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#include <asm/vsyscall.h>
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#include <asm/vgtod.h>
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#include <asm/timex.h>
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#include <asm/hpet.h>
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#include <asm/unistd.h>
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#include <asm/io.h>
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#include <asm/vgtod.h>
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#include "vextern.h"
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#define gtod vdso_vsyscall_gtod_data
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static long vdso_fallback_gettime(long clock, struct timespec *ts)
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{
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long ret;
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asm("syscall" : "=a" (ret) :
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"0" (__NR_clock_gettime),"D" (clock), "S" (ts) : "memory");
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return ret;
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}
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static inline long vgetns(void)
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{
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cycles_t (*vread)(void);
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vread = gtod->clock.vread;
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return ((vread() - gtod->clock.cycle_last) * gtod->clock.mult) >>
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gtod->clock.shift;
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}
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static noinline int do_realtime(struct timespec *ts)
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{
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unsigned long seq, ns;
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do {
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seq = read_seqbegin(>od->lock);
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ts->tv_sec = gtod->wall_time_sec;
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ts->tv_nsec = gtod->wall_time_nsec;
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ns = vgetns();
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} while (unlikely(read_seqretry(>od->lock, seq)));
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timespec_add_ns(ts, ns);
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return 0;
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}
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/* Copy of the version in kernel/time.c which we cannot directly access */
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static void vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
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{
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while (nsec >= NSEC_PER_SEC) {
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nsec -= NSEC_PER_SEC;
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++sec;
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}
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while (nsec < 0) {
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nsec += NSEC_PER_SEC;
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--sec;
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}
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ts->tv_sec = sec;
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ts->tv_nsec = nsec;
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}
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static noinline int do_monotonic(struct timespec *ts)
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{
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unsigned long seq, ns, secs;
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do {
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seq = read_seqbegin(>od->lock);
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secs = gtod->wall_time_sec;
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ns = gtod->wall_time_nsec + vgetns();
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secs += gtod->wall_to_monotonic.tv_sec;
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ns += gtod->wall_to_monotonic.tv_nsec;
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} while (unlikely(read_seqretry(>od->lock, seq)));
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vset_normalized_timespec(ts, secs, ns);
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return 0;
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}
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int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
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{
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if (likely(gtod->sysctl_enabled && gtod->clock.vread))
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switch (clock) {
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case CLOCK_REALTIME:
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return do_realtime(ts);
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case CLOCK_MONOTONIC:
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return do_monotonic(ts);
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}
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return vdso_fallback_gettime(clock, ts);
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}
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int clock_gettime(clockid_t, struct timespec *)
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__attribute__((weak, alias("__vdso_clock_gettime")));
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int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
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{
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long ret;
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if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
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BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
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offsetof(struct timespec, tv_nsec) ||
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sizeof(*tv) != sizeof(struct timespec));
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do_realtime((struct timespec *)tv);
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tv->tv_usec /= 1000;
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if (unlikely(tz != NULL)) {
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/* This relies on gcc inlining the memcpy. We'll notice
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if it ever fails to do so. */
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memcpy(tz, >od->sys_tz, sizeof(struct timezone));
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}
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return 0;
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}
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asm("syscall" : "=a" (ret) :
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"0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
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return ret;
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}
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int gettimeofday(struct timeval *, struct timezone *)
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__attribute__((weak, alias("__vdso_gettimeofday")));
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