1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
5 * Copyright (c) 2016, 2017, 2019 The FreeBSD Foundation
6 * Copyright (c) 2021 Dmitry Chagin <dchagin@FreeBSD.org>
7 *
8 * Portions of this software were developed by Konstantin Belousov
9 * under sponsorship from the FreeBSD Foundation.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33static inline u_int
34rdtsc_low(const struct vdso_timehands *th)
35{
36	u_int rv;
37
38	__asm __volatile("rdtsc; shrd %%cl, %%edx, %0"
39	    : "=a" (rv) : "c" (th->th_x86_shift) : "edx");
40	return (rv);
41}
42
43static inline u_int
44rdtscp_low(const struct vdso_timehands *th)
45{
46	u_int rv;
47
48	__asm __volatile("rdtscp; movl %%edi,%%ecx; shrd %%cl, %%edx, %0"
49	    : "=a" (rv) : "D" (th->th_x86_shift) : "ecx", "edx");
50	return (rv);
51}
52
53static u_int
54rdtsc_low_mb_lfence(const struct vdso_timehands *th)
55{
56	lfence();
57	return (rdtsc_low(th));
58}
59
60static u_int
61rdtsc_low_mb_mfence(const struct vdso_timehands *th)
62{
63	mfence();
64	return (rdtsc_low(th));
65}
66
67static u_int
68rdtsc_low_mb_none(const struct vdso_timehands *th)
69{
70	return (rdtsc_low(th));
71}
72
73static u_int
74rdtsc32_mb_lfence(void)
75{
76	lfence();
77	return (rdtsc32());
78}
79
80static u_int
81rdtsc32_mb_mfence(void)
82{
83	mfence();
84	return (rdtsc32());
85}
86
87static u_int
88rdtsc32_mb_none(void)
89{
90	return (rdtsc32());
91}
92
93static u_int
94rdtscp32_(void)
95{
96	return (rdtscp32());
97}
98
99struct tsc_selector_tag {
100	u_int (*ts_rdtsc32)(void);
101	u_int (*ts_rdtsc_low)(const struct vdso_timehands *);
102};
103
104static const struct tsc_selector_tag tsc_selector[] = {
105	[0] = {				/* Intel, LFENCE */
106		.ts_rdtsc32 =	rdtsc32_mb_lfence,
107		.ts_rdtsc_low =	rdtsc_low_mb_lfence,
108	},
109	[1] = {				/* AMD, MFENCE */
110		.ts_rdtsc32 =	rdtsc32_mb_mfence,
111		.ts_rdtsc_low =	rdtsc_low_mb_mfence,
112	},
113	[2] = {				/* No SSE2 */
114		.ts_rdtsc32 = rdtsc32_mb_none,
115		.ts_rdtsc_low = rdtsc_low_mb_none,
116	},
117	[3] = {				/* RDTSCP */
118		.ts_rdtsc32 =	rdtscp32_,
119		.ts_rdtsc_low =	rdtscp_low,
120	},
121};
122
123static u_int
124__vdso_gettc_rdtsc_low(const struct vdso_timehands *th)
125{
126
127	return (tsc_selector[kern_tsc_selector].ts_rdtsc_low(th));
128}
129
130static u_int
131__vdso_gettc_rdtsc32(void)
132{
133
134	return (tsc_selector[kern_tsc_selector].ts_rdtsc32());
135}
136
137int
138__vdso_gettc(const struct vdso_timehands *th, u_int *tc)
139{
140
141	switch (th->th_algo) {
142	case VDSO_TH_ALGO_X86_TSC:
143		*tc = th->th_x86_shift > 0 ? __vdso_gettc_rdtsc_low(th) :
144		    __vdso_gettc_rdtsc32();
145		return (0);
146	case VDSO_TH_ALGO_X86_HPET:
147		/* TODO */
148	default:
149		return (ENOSYS);
150	}
151}
152