2 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 #include <sys/cdefs.h>
27 __FBSDID("$FreeBSD$");
29 #include <sys/types.h>
33 #include <machine/cpufunc.h>
34 #include <machine/specialreg.h>
35 #include "libc_private.h"
37 static int lfence_works = -1;
40 get_lfence_usage(void)
42 u_int cpuid_supported, p[4];
44 if (lfence_works == -1) {
49 " xorl $0x200000,%%eax\n"
60 : "=r" (cpuid_supported) : : "eax", "ecx");
61 if (cpuid_supported) {
67 : "=a" (p[0]), "=r" (p[1]), "=c" (p[2]), "=d" (p[3])
69 lfence_works = (p[3] & CPUID_SSE2) != 0;
73 return (lfence_works);
77 __vdso_gettc_low(const struct vdso_timehands *th)
81 if (get_lfence_usage() == 1)
83 __asm __volatile("rdtsc; shrd %%cl, %%edx, %0"
84 : "=a" (rv) : "c" (th->th_x86_shift) : "edx");
93 if (get_lfence_usage() == 1)
99 #pragma weak __vdso_gettc
101 __vdso_gettc(const struct vdso_timehands *th)
104 return (th->th_x86_shift > 0 ? __vdso_gettc_low(th) :
108 #pragma weak __vdso_gettimekeep
110 __vdso_gettimekeep(struct vdso_timekeep **tk)
113 return (_elf_aux_info(AT_TIMEKEEP, tk, sizeof(*tk)));