![Thomas Gleixner](/assets/img/avatar_default.png)
Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@mit.edu>
192 lines
4.8 KiB
C
192 lines
4.8 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, gettimeofday, and time.
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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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/* Disable profiling for userspace code: */
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#define DISABLE_BRANCH_PROFILING
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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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#define gtod (&VVAR(vsyscall_gtod_data))
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notrace 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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notrace static inline long vgetns(void)
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{
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long v;
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cycles_t (*vread)(void);
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vread = gtod->clock.vread;
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v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
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return (v * gtod->clock.mult) >> gtod->clock.shift;
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}
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notrace 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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notrace 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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/* wall_time_nsec, vgetns(), and wall_to_monotonic.tv_nsec
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* are all guaranteed to be nonnegative.
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*/
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while (ns >= NSEC_PER_SEC) {
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ns -= NSEC_PER_SEC;
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++secs;
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}
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ts->tv_sec = secs;
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ts->tv_nsec = ns;
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return 0;
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}
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notrace static noinline int do_realtime_coarse(struct timespec *ts)
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{
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unsigned long seq;
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do {
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seq = read_seqbegin(>od->lock);
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ts->tv_sec = gtod->wall_time_coarse.tv_sec;
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ts->tv_nsec = gtod->wall_time_coarse.tv_nsec;
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} while (unlikely(read_seqretry(>od->lock, seq)));
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return 0;
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}
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notrace static noinline int do_monotonic_coarse(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_coarse.tv_sec;
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ns = gtod->wall_time_coarse.tv_nsec;
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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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/* wall_time_nsec and wall_to_monotonic.tv_nsec are
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* guaranteed to be between 0 and NSEC_PER_SEC.
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*/
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if (ns >= NSEC_PER_SEC) {
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ns -= NSEC_PER_SEC;
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++secs;
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}
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ts->tv_sec = secs;
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ts->tv_nsec = ns;
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return 0;
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}
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notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
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{
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if (likely(gtod->sysctl_enabled))
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switch (clock) {
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case CLOCK_REALTIME:
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if (likely(gtod->clock.vread))
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return do_realtime(ts);
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break;
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case CLOCK_MONOTONIC:
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if (likely(gtod->clock.vread))
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return do_monotonic(ts);
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break;
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case CLOCK_REALTIME_COARSE:
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return do_realtime_coarse(ts);
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case CLOCK_MONOTONIC_COARSE:
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return do_monotonic_coarse(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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notrace 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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if (likely(tv != NULL)) {
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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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}
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if (unlikely(tz != NULL)) {
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/* Avoid memcpy. Some old compilers fail to inline it */
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tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;
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tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
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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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/* This will break when the xtime seconds get inaccurate, but that is
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* unlikely */
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static __always_inline long time_syscall(long *t)
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{
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long secs;
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asm volatile("syscall"
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: "=a" (secs)
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: "0" (__NR_time), "D" (t) : "cc", "r11", "cx", "memory");
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return secs;
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}
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notrace time_t __vdso_time(time_t *t)
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{
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time_t result;
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if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled))
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return time_syscall(t);
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/* This is atomic on x86_64 so we don't need any locks. */
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result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec);
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if (t)
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*t = result;
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return result;
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}
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int time(time_t *t)
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__attribute__((weak, alias("__vdso_time")));
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