1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 #include <sys/cdefs.h>
29 #include <sys/elf.h>
30 #include <sys/time.h>
31 #include <sys/vdso.h>
32 #include <errno.h>
33 #include <stdbool.h>
34 #include <strings.h>
35 #include <time.h>
36 #include <machine/atomic.h>
37 #include "libc_private.h"
38
39 static int
tc_delta(const struct vdso_timehands * th,u_int * delta)40 tc_delta(const struct vdso_timehands *th, u_int *delta)
41 {
42 int error;
43 u_int tc;
44
45 error = __vdso_gettc(th, &tc);
46 if (error == 0)
47 *delta = (tc - th->th_offset_count) & th->th_counter_mask;
48 return (error);
49 }
50
51 /*
52 * Calculate the absolute or boot-relative time from the
53 * machine-specific fast timecounter and the published timehands
54 * structure read from the shared page.
55 *
56 * The lockless reading scheme is similar to the one used to read the
57 * in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code
58 * is based on the kernel implementation.
59 */
60 static int
binuptime(struct bintime * bt,struct vdso_timekeep * tk,bool abs)61 binuptime(struct bintime *bt, struct vdso_timekeep *tk, bool abs)
62 {
63 struct vdso_timehands *th;
64 uint32_t curr, gen;
65 uint64_t scale, x;
66 u_int delta, scale_bits;
67 int error;
68
69 do {
70 if (!tk->tk_enabled)
71 return (ENOSYS);
72
73 curr = atomic_load_acq_32(&tk->tk_current);
74 th = &tk->tk_th[curr];
75 gen = atomic_load_acq_32(&th->th_gen);
76 *bt = th->th_offset;
77 error = tc_delta(th, &delta);
78 if (error == EAGAIN)
79 continue;
80 if (error != 0)
81 return (error);
82 scale = th->th_scale;
83 #ifdef _LP64
84 scale_bits = flsl(scale);
85 #else
86 scale_bits = flsll(scale);
87 #endif
88 if (__predict_false(scale_bits + fls(delta) > 63)) {
89 x = (scale >> 32) * delta;
90 scale &= 0xffffffff;
91 bt->sec += x >> 32;
92 bintime_addx(bt, x << 32);
93 }
94 bintime_addx(bt, scale * delta);
95 if (abs)
96 bintime_add(bt, &th->th_boottime);
97
98 /*
99 * Ensure that the load of th_offset is completed
100 * before the load of th_gen.
101 */
102 atomic_thread_fence_acq();
103 } while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
104 return (0);
105 }
106
107 static int
getnanouptime(struct bintime * bt,struct vdso_timekeep * tk)108 getnanouptime(struct bintime *bt, struct vdso_timekeep *tk)
109 {
110 struct vdso_timehands *th;
111 uint32_t curr, gen;
112
113 do {
114 if (!tk->tk_enabled)
115 return (ENOSYS);
116
117 curr = atomic_load_acq_32(&tk->tk_current);
118 th = &tk->tk_th[curr];
119 gen = atomic_load_acq_32(&th->th_gen);
120 *bt = th->th_offset;
121
122 /*
123 * Ensure that the load of th_offset is completed
124 * before the load of th_gen.
125 */
126 atomic_thread_fence_acq();
127 } while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
128 return (0);
129 }
130
131 static struct vdso_timekeep *tk;
132
133 #pragma weak __vdso_gettimeofday
134 int
__vdso_gettimeofday(struct timeval * tv,struct timezone * tz)135 __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
136 {
137 struct bintime bt;
138 int error;
139
140 if (tz != NULL)
141 return (ENOSYS);
142 if (tk == NULL) {
143 error = __vdso_gettimekeep(&tk);
144 if (error != 0 || tk == NULL)
145 return (ENOSYS);
146 }
147 if (tk->tk_ver != VDSO_TK_VER_CURR)
148 return (ENOSYS);
149 error = binuptime(&bt, tk, true);
150 if (error != 0)
151 return (error);
152 bintime2timeval(&bt, tv);
153 return (0);
154 }
155
156 #pragma weak __vdso_clock_gettime
157 int
__vdso_clock_gettime(clockid_t clock_id,struct timespec * ts)158 __vdso_clock_gettime(clockid_t clock_id, struct timespec *ts)
159 {
160 struct bintime bt;
161 int error;
162
163 if (tk == NULL) {
164 error = _elf_aux_info(AT_TIMEKEEP, &tk, sizeof(tk));
165 if (error != 0 || tk == NULL)
166 return (ENOSYS);
167 }
168 if (tk->tk_ver != VDSO_TK_VER_CURR)
169 return (ENOSYS);
170 switch (clock_id) {
171 case CLOCK_REALTIME:
172 case CLOCK_REALTIME_PRECISE:
173 case CLOCK_REALTIME_FAST:
174 case CLOCK_SECOND:
175 error = binuptime(&bt, tk, true);
176 break;
177 case CLOCK_MONOTONIC:
178 case CLOCK_MONOTONIC_PRECISE:
179 case CLOCK_UPTIME:
180 case CLOCK_UPTIME_PRECISE:
181 error = binuptime(&bt, tk, false);
182 break;
183 case CLOCK_MONOTONIC_FAST:
184 case CLOCK_UPTIME_FAST:
185 error = getnanouptime(&bt, tk);
186 break;
187 default:
188 error = ENOSYS;
189 break;
190 }
191 if (error != 0)
192 return (error);
193 bintime2timespec(&bt, ts);
194 if (clock_id == CLOCK_SECOND)
195 ts->tv_nsec = 0;
196 return (0);
197 }
198