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/elf.h>
29 #include <sys/time.h>
30 #include <sys/vdso.h>
31 #include <errno.h>
32 #include <stdbool.h>
33 #include <strings.h>
34 #include <time.h>
35 #include <machine/atomic.h>
36 #include "libc_private.h"
37
38 static int
tc_delta(const struct vdso_timehands * th,u_int * delta)39 tc_delta(const struct vdso_timehands *th, u_int *delta)
40 {
41 int error;
42 u_int tc;
43
44 error = __vdso_gettc(th, &tc);
45 if (error == 0)
46 *delta = (tc - th->th_offset_count) & th->th_counter_mask;
47 return (error);
48 }
49
50 /*
51 * Calculate the absolute or boot-relative time from the
52 * machine-specific fast timecounter and the published timehands
53 * structure read from the shared page.
54 *
55 * The lockless reading scheme is similar to the one used to read the
56 * in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code
57 * is based on the kernel implementation.
58 */
59 static int
binuptime(struct bintime * bt,struct vdso_timekeep * tk,bool abs)60 binuptime(struct bintime *bt, struct vdso_timekeep *tk, bool abs)
61 {
62 struct vdso_timehands *th;
63 uint32_t curr, gen;
64 uint64_t scale, x;
65 u_int delta, scale_bits;
66 int error;
67
68 do {
69 if (!tk->tk_enabled)
70 return (ENOSYS);
71
72 curr = atomic_load_acq_32(&tk->tk_current);
73 th = &tk->tk_th[curr];
74 gen = atomic_load_acq_32(&th->th_gen);
75 *bt = th->th_offset;
76 error = tc_delta(th, &delta);
77 if (error == EAGAIN)
78 continue;
79 if (error != 0)
80 return (error);
81 scale = th->th_scale;
82 #ifdef _LP64
83 scale_bits = flsl(scale);
84 #else
85 scale_bits = flsll(scale);
86 #endif
87 if (__predict_false(scale_bits + fls(delta) > 63)) {
88 x = (scale >> 32) * delta;
89 scale &= 0xffffffff;
90 bt->sec += x >> 32;
91 bintime_addx(bt, x << 32);
92 }
93 bintime_addx(bt, scale * delta);
94 if (abs)
95 bintime_add(bt, &th->th_boottime);
96
97 /*
98 * Ensure that the load of th_offset is completed
99 * before the load of th_gen.
100 */
101 atomic_thread_fence_acq();
102 } while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
103 return (0);
104 }
105
106 static int
getnanouptime(struct bintime * bt,struct vdso_timekeep * tk)107 getnanouptime(struct bintime *bt, struct vdso_timekeep *tk)
108 {
109 struct vdso_timehands *th;
110 uint32_t curr, gen;
111
112 do {
113 if (!tk->tk_enabled)
114 return (ENOSYS);
115
116 curr = atomic_load_acq_32(&tk->tk_current);
117 th = &tk->tk_th[curr];
118 gen = atomic_load_acq_32(&th->th_gen);
119 *bt = th->th_offset;
120
121 /*
122 * Ensure that the load of th_offset is completed
123 * before the load of th_gen.
124 */
125 atomic_thread_fence_acq();
126 } while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
127 return (0);
128 }
129
130 static struct vdso_timekeep *tk;
131
132 #pragma weak __vdso_gettimeofday
133 int
__vdso_gettimeofday(struct timeval * tv,struct timezone * tz)134 __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
135 {
136 struct bintime bt;
137 int error;
138
139 if (tz != NULL)
140 return (ENOSYS);
141 if (tk == NULL) {
142 error = __vdso_gettimekeep(&tk);
143 if (error != 0 || tk == NULL)
144 return (ENOSYS);
145 }
146 if (tk->tk_ver != VDSO_TK_VER_CURR)
147 return (ENOSYS);
148 error = binuptime(&bt, tk, true);
149 if (error != 0)
150 return (error);
151 bintime2timeval(&bt, tv);
152 return (0);
153 }
154
155 #pragma weak __vdso_clock_gettime
156 int
__vdso_clock_gettime(clockid_t clock_id,struct timespec * ts)157 __vdso_clock_gettime(clockid_t clock_id, struct timespec *ts)
158 {
159 struct bintime bt;
160 int error;
161
162 if (tk == NULL) {
163 error = _elf_aux_info(AT_TIMEKEEP, &tk, sizeof(tk));
164 if (error != 0 || tk == NULL)
165 return (ENOSYS);
166 }
167 if (tk->tk_ver != VDSO_TK_VER_CURR)
168 return (ENOSYS);
169 switch (clock_id) {
170 case CLOCK_REALTIME:
171 case CLOCK_REALTIME_PRECISE:
172 case CLOCK_REALTIME_FAST:
173 case CLOCK_SECOND:
174 error = binuptime(&bt, tk, true);
175 break;
176 case CLOCK_MONOTONIC:
177 case CLOCK_MONOTONIC_PRECISE:
178 case CLOCK_UPTIME:
179 case CLOCK_UPTIME_PRECISE:
180 error = binuptime(&bt, tk, false);
181 break;
182 case CLOCK_MONOTONIC_FAST:
183 case CLOCK_UPTIME_FAST:
184 error = getnanouptime(&bt, tk);
185 break;
186 default:
187 error = ENOSYS;
188 break;
189 }
190 if (error != 0)
191 return (error);
192 bintime2timespec(&bt, ts);
193 if (clock_id == CLOCK_SECOND)
194 ts->tv_nsec = 0;
195 return (0);
196 }
197