amd64_detect_rdfsgsbase.c revision 322763 
1/*-
2 * Copyright (c) 2017 The FreeBSD Foundation
3 * All rights reserved.
4 *
5 * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
6 * under sponsorship from the FreeBSD Foundation.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD: head/lib/libc/amd64/sys/amd64_detect_rdfsgsbase.c 322763 2017-08-21 17:39:12Z kib $");
32
33#define	IN_RTLD	1
34#include <sys/param.h>
35#undef IN_RTLD
36#include <machine/cpufunc.h>
37#include <machine/specialreg.h>
38#include "amd64_detect_rdfsgsbase.h"
39#include "libc_private.h"
40
41static int state = RDFSGS_UNKNOWN;
42
43int
44amd64_detect_rdfsgsbase(void)
45{
46	u_int p[4];
47
48	if (__predict_true(state != RDFSGS_UNKNOWN))
49		return (state);
50
51	if (__getosreldate() >= P_OSREL_WRFSBASE) {
52		do_cpuid(0x0, p);
53		if (p[0] >= 0x7) {
54			cpuid_count(0x7, 0x0, p);
55			if ((p[1] & CPUID_STDEXT_FSGSBASE) != 0) {
56				state = RDFSGS_SUPPORTED;
57				return (state);
58			}
59		}
60	}
61	state = RDFSGS_UNSUPPORTED;
62	return (state);
63}
64