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/*-
* Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/elf.h>
#include <sys/time.h>
#include <sys/vdso.h>
#include <machine/cpufunc.h>
#include <machine/specialreg.h>
#include "libc_private.h"
static int lfence_works = -1;
static int
get_lfence_usage(void)
{
u_int cpuid_supported, p[4];
if (lfence_works == -1) {
__asm __volatile(
" pushfl\n"
" popl %%eax\n"
" movl %%eax,%%ecx\n"
" xorl $0x200000,%%eax\n"
" pushl %%eax\n"
" popfl\n"
" pushfl\n"
" popl %%eax\n"
" xorl %%eax,%%ecx\n"
" je 1f\n"
" movl $1,%0\n"
" jmp 2f\n"
"1: movl $0,%0\n"
"2:\n"
: "=r" (cpuid_supported) : : "eax", "ecx");
if (cpuid_supported) {
__asm __volatile(
" pushl %%ebx\n"
" cpuid\n"
" movl %%ebx,%1\n"
" popl %%ebx\n"
: "=a" (p[0]), "=r" (p[1]), "=c" (p[2]), "=d" (p[3])
: "0" (0x1));
lfence_works = (p[3] & CPUID_SSE2) != 0;
} else
lfence_works = 0;
}
return (lfence_works);
}
static u_int
__vdso_gettc_low(const struct vdso_timehands *th)
{
u_int rv;
if (get_lfence_usage() == 1)
lfence();
__asm __volatile("rdtsc; shrd %%cl, %%edx, %0"
: "=a" (rv) : "c" (th->th_x86_shift) : "edx");
return (rv);
}
static u_int
__vdso_rdtsc32(void)
{
u_int rv;
if (get_lfence_usage() == 1)
lfence();
rv = rdtsc32();
return (rv);
}
#pragma weak __vdso_gettc
u_int
__vdso_gettc(const struct vdso_timehands *th)
{
return (th->th_x86_shift > 0 ? __vdso_gettc_low(th) :
__vdso_rdtsc32());
}
#pragma weak __vdso_gettimekeep
int
__vdso_gettimekeep(struct vdso_timekeep **tk)
{
return (_elf_aux_info(AT_TIMEKEEP, tk, sizeof(*tk)));
}
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