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 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 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 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 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 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