| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | */ |
| 6 | |
| 7 | #define _LGPL_SOURCE |
| 8 | #include <error.h> |
| 9 | #include <dlfcn.h> |
| 10 | #include <stdlib.h> |
| 11 | #include <stdint.h> |
| 12 | #include <stdio.h> |
| 13 | #include <usterr-signal-safe.h> |
| 14 | #include <lttng/ust-clock.h> |
| 15 | #include <urcu/system.h> |
| 16 | #include <urcu/arch.h> |
| 17 | |
| 18 | #include "clock.h" |
| 19 | #include "getenv.h" |
| 20 | |
| 21 | struct lttng_ust_trace_clock *lttng_ust_trace_clock; |
| 22 | |
| 23 | static |
| 24 | struct lttng_ust_trace_clock user_tc; |
| 25 | |
| 26 | static |
| 27 | void *clock_handle; |
| 28 | |
| 29 | static |
| 30 | uint64_t trace_clock_freq_monotonic(void) |
| 31 | { |
| 32 | return 1000000000ULL; |
| 33 | } |
| 34 | |
| 35 | static |
| 36 | int trace_clock_uuid_monotonic(char *uuid) |
| 37 | { |
| 38 | int ret = 0; |
| 39 | size_t len; |
| 40 | FILE *fp; |
| 41 | |
| 42 | /* |
| 43 | * boot_id needs to be read once before being used concurrently |
| 44 | * to deal with a Linux kernel race. A fix is proposed for |
| 45 | * upstream, but the work-around is needed for older kernels. |
| 46 | */ |
| 47 | fp = fopen("/proc/sys/kernel/random/boot_id", "r"); |
| 48 | if (!fp) { |
| 49 | return -ENOENT; |
| 50 | } |
| 51 | len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp); |
| 52 | if (len < LTTNG_UST_UUID_STR_LEN - 1) { |
| 53 | ret = -EINVAL; |
| 54 | goto end; |
| 55 | } |
| 56 | uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0'; |
| 57 | end: |
| 58 | fclose(fp); |
| 59 | return ret; |
| 60 | } |
| 61 | |
| 62 | static |
| 63 | const char *trace_clock_name_monotonic(void) |
| 64 | { |
| 65 | return "monotonic"; |
| 66 | } |
| 67 | |
| 68 | static |
| 69 | const char *trace_clock_description_monotonic(void) |
| 70 | { |
| 71 | return "Monotonic Clock"; |
| 72 | } |
| 73 | |
| 74 | int lttng_ust_trace_clock_set_read64_cb(lttng_ust_clock_read64_function read64_cb) |
| 75 | { |
| 76 | if (CMM_LOAD_SHARED(lttng_ust_trace_clock)) |
| 77 | return -EBUSY; |
| 78 | user_tc.read64 = read64_cb; |
| 79 | return 0; |
| 80 | } |
| 81 | |
| 82 | int lttng_ust_trace_clock_get_read64_cb(lttng_ust_clock_read64_function *read64_cb) |
| 83 | { |
| 84 | struct lttng_ust_trace_clock *ltc = CMM_LOAD_SHARED(lttng_ust_trace_clock); |
| 85 | |
| 86 | if (caa_likely(!ltc)) { |
| 87 | *read64_cb = &trace_clock_read64_monotonic; |
| 88 | } else { |
| 89 | cmm_read_barrier_depends(); /* load ltc before content */ |
| 90 | *read64_cb = ltc->read64; |
| 91 | } |
| 92 | return 0; |
| 93 | } |
| 94 | |
| 95 | int lttng_ust_trace_clock_set_freq_cb(lttng_ust_clock_freq_function freq_cb) |
| 96 | { |
| 97 | if (CMM_LOAD_SHARED(lttng_ust_trace_clock)) |
| 98 | return -EBUSY; |
| 99 | user_tc.freq = freq_cb; |
| 100 | return 0; |
| 101 | } |
| 102 | |
| 103 | int lttng_ust_trace_clock_get_freq_cb(lttng_ust_clock_freq_function *freq_cb) |
| 104 | { |
| 105 | struct lttng_ust_trace_clock *ltc = CMM_LOAD_SHARED(lttng_ust_trace_clock); |
| 106 | |
| 107 | if (caa_likely(!ltc)) { |
| 108 | *freq_cb = &trace_clock_freq_monotonic; |
| 109 | } else { |
| 110 | cmm_read_barrier_depends(); /* load ltc before content */ |
| 111 | *freq_cb = ltc->freq; |
| 112 | } |
| 113 | return 0; |
| 114 | } |
| 115 | |
| 116 | int lttng_ust_trace_clock_set_uuid_cb(lttng_ust_clock_uuid_function uuid_cb) |
| 117 | { |
| 118 | if (CMM_LOAD_SHARED(lttng_ust_trace_clock)) |
| 119 | return -EBUSY; |
| 120 | user_tc.uuid = uuid_cb; |
| 121 | return 0; |
| 122 | } |
| 123 | |
| 124 | int lttng_ust_trace_clock_get_uuid_cb(lttng_ust_clock_uuid_function *uuid_cb) |
| 125 | { |
| 126 | struct lttng_ust_trace_clock *ltc = CMM_LOAD_SHARED(lttng_ust_trace_clock); |
| 127 | |
| 128 | if (caa_likely(!ltc)) { |
| 129 | *uuid_cb = &trace_clock_uuid_monotonic; |
| 130 | } else { |
| 131 | cmm_read_barrier_depends(); /* load ltc before content */ |
| 132 | *uuid_cb = ltc->uuid; |
| 133 | } |
| 134 | return 0; |
| 135 | } |
| 136 | |
| 137 | int lttng_ust_trace_clock_set_name_cb(lttng_ust_clock_name_function name_cb) |
| 138 | { |
| 139 | if (CMM_LOAD_SHARED(lttng_ust_trace_clock)) |
| 140 | return -EBUSY; |
| 141 | user_tc.name = name_cb; |
| 142 | return 0; |
| 143 | } |
| 144 | |
| 145 | int lttng_ust_trace_clock_get_name_cb(lttng_ust_clock_name_function *name_cb) |
| 146 | { |
| 147 | struct lttng_ust_trace_clock *ltc = CMM_LOAD_SHARED(lttng_ust_trace_clock); |
| 148 | |
| 149 | if (caa_likely(!ltc)) { |
| 150 | *name_cb = &trace_clock_name_monotonic; |
| 151 | } else { |
| 152 | cmm_read_barrier_depends(); /* load ltc before content */ |
| 153 | *name_cb = ltc->name; |
| 154 | } |
| 155 | return 0; |
| 156 | } |
| 157 | |
| 158 | int lttng_ust_trace_clock_set_description_cb(lttng_ust_clock_description_function description_cb) |
| 159 | { |
| 160 | if (CMM_LOAD_SHARED(lttng_ust_trace_clock)) |
| 161 | return -EBUSY; |
| 162 | user_tc.description = description_cb; |
| 163 | return 0; |
| 164 | } |
| 165 | |
| 166 | int lttng_ust_trace_clock_get_description_cb(lttng_ust_clock_description_function *description_cb) |
| 167 | { |
| 168 | struct lttng_ust_trace_clock *ltc = CMM_LOAD_SHARED(lttng_ust_trace_clock); |
| 169 | |
| 170 | if (caa_likely(!ltc)) { |
| 171 | *description_cb = &trace_clock_description_monotonic; |
| 172 | } else { |
| 173 | cmm_read_barrier_depends(); /* load ltc before content */ |
| 174 | *description_cb = ltc->description; |
| 175 | } |
| 176 | return 0; |
| 177 | } |
| 178 | |
| 179 | int lttng_ust_enable_trace_clock_override(void) |
| 180 | { |
| 181 | if (CMM_LOAD_SHARED(lttng_ust_trace_clock)) |
| 182 | return -EBUSY; |
| 183 | if (!user_tc.read64) |
| 184 | return -EINVAL; |
| 185 | if (!user_tc.freq) |
| 186 | return -EINVAL; |
| 187 | if (!user_tc.name) |
| 188 | return -EINVAL; |
| 189 | if (!user_tc.description) |
| 190 | return -EINVAL; |
| 191 | /* Use default uuid cb when NULL */ |
| 192 | cmm_smp_mb(); /* Store callbacks before trace clock */ |
| 193 | CMM_STORE_SHARED(lttng_ust_trace_clock, &user_tc); |
| 194 | return 0; |
| 195 | } |
| 196 | |
| 197 | void lttng_ust_clock_init(void) |
| 198 | { |
| 199 | const char *libname; |
| 200 | void (*libinit)(void); |
| 201 | |
| 202 | if (clock_handle) |
| 203 | return; |
| 204 | libname = lttng_ust_getenv("LTTNG_UST_CLOCK_PLUGIN"); |
| 205 | if (!libname) |
| 206 | return; |
| 207 | clock_handle = dlopen(libname, RTLD_NOW); |
| 208 | if (!clock_handle) { |
| 209 | PERROR("Cannot load LTTng UST clock override library %s", |
| 210 | libname); |
| 211 | return; |
| 212 | } |
| 213 | dlerror(); |
| 214 | libinit = (void (*)(void)) dlsym(clock_handle, |
| 215 | "lttng_ust_clock_plugin_init"); |
| 216 | if (!libinit) { |
| 217 | PERROR("Cannot find LTTng UST clock override library %s initialization function lttng_ust_clock_plugin_init()", |
| 218 | libname); |
| 219 | return; |
| 220 | } |
| 221 | libinit(); |
| 222 | } |