x86-64: Add time to vDSO

 * Copyright 2006 Andi Kleen, SUSE Labs.

 * Subject to the GNU Public License, v.2

 *

 * Fast user context implementation of clock_gettime and gettimeofday.

 * Fast user context implementation of clock_gettime, gettimeofday, and time.

 *

 * The code should have no internal unresolved relocations.

 * Check with readelf after changing.

}

int gettimeofday(struct timeval *, struct timezone *)

	__attribute__((weak, alias("__vdso_gettimeofday")));

/* This will break when the xtime seconds get inaccurate, but that is

 * unlikely */

static __always_inline long time_syscall(long *t)

{

	long secs;

	asm volatile("syscall"

		     : "=a" (secs)

		     : "0" (__NR_time), "D" (t) : "cc", "r11", "cx", "memory");

	return secs;

}

notrace time_t __vdso_time(time_t *t)

{

	unsigned seq;

	time_t result;

	if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled))

		return time_syscall(t);

	do {

		seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock);

		result = VVAR(vsyscall_gtod_data).wall_time_sec;

	} while (read_seqretry(&VVAR(vsyscall_gtod_data).lock, seq));

	if (t)

		*t = result;

	return result;

}

int time(time_t *t)

	__attribute__((weak, alias("__vdso_time")));

		__vdso_gettimeofday;

		getcpu;

		__vdso_getcpu;

		time;

		__vdso_time;

	local: *;

	};

}