| 1 | // SPDX-License-Identifier: MIT |
| 2 | /* |
| 3 | * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 4 | */ |
| 5 | |
| 6 | #include <side/trace.h> |
| 7 | #include <string.h> |
| 8 | |
| 9 | #include "rcu.h" |
| 10 | #include "list.h" |
| 11 | |
| 12 | /* Top 8 bits reserved for kernel tracer use. */ |
| 13 | #if SIDE_BITS_PER_LONG == 64 |
| 14 | # define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF00000000000000ULL |
| 15 | # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x8000000000000000ULL |
| 16 | |
| 17 | /* Allow 2^56 tracer references on an event. */ |
| 18 | # define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFFFFFFFFFULL |
| 19 | #else |
| 20 | # define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000UL |
| 21 | # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000UL |
| 22 | |
| 23 | /* Allow 2^24 tracer references on an event. */ |
| 24 | # define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFUL |
| 25 | #endif |
| 26 | |
| 27 | struct side_events_register_handle { |
| 28 | struct side_list_node node; |
| 29 | struct side_event_description **events; |
| 30 | uint32_t nr_events; |
| 31 | }; |
| 32 | |
| 33 | struct side_tracer_handle { |
| 34 | struct side_list_node node; |
| 35 | void (*cb)(enum side_tracer_notification notif, |
| 36 | struct side_event_description **events, uint32_t nr_events, void *priv); |
| 37 | void *priv; |
| 38 | }; |
| 39 | |
| 40 | static struct side_rcu_gp_state rcu_gp; |
| 41 | |
| 42 | /* |
| 43 | * Lazy initialization for early use within library constructors. |
| 44 | */ |
| 45 | static bool initialized; |
| 46 | /* |
| 47 | * Do not register/unregister any more events after destructor. |
| 48 | */ |
| 49 | static bool finalized; |
| 50 | |
| 51 | /* |
| 52 | * Recursive mutex to allow tracer callbacks to use the side API. |
| 53 | */ |
| 54 | static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; |
| 55 | |
| 56 | static DEFINE_SIDE_LIST_HEAD(side_events_list); |
| 57 | static DEFINE_SIDE_LIST_HEAD(side_tracer_list); |
| 58 | |
| 59 | /* |
| 60 | * The empty callback has a NULL function callback pointer, which stops |
| 61 | * iteration on the array of callbacks immediately. |
| 62 | */ |
| 63 | const struct side_callback side_empty_callback = { }; |
| 64 | |
| 65 | void side_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec) |
| 66 | { |
| 67 | struct side_rcu_read_state rcu_read_state; |
| 68 | const struct side_callback *side_cb; |
| 69 | uintptr_t enabled; |
| 70 | |
| 71 | if (side_unlikely(finalized)) |
| 72 | return; |
| 73 | if (side_unlikely(!initialized)) |
| 74 | side_init(); |
| 75 | if (side_unlikely(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC)) { |
| 76 | printf("ERROR: unexpected variadic event description\n"); |
| 77 | abort(); |
| 78 | } |
| 79 | enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED); |
| 80 | if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { |
| 81 | // TODO: call kernel write. |
| 82 | } |
| 83 | side_rcu_read_begin(&rcu_gp, &rcu_read_state); |
| 84 | for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call != NULL; side_cb++) |
| 85 | side_cb->u.call(event_state->desc, side_arg_vec, side_cb->priv); |
| 86 | side_rcu_read_end(&rcu_gp, &rcu_read_state); |
| 87 | } |
| 88 | |
| 89 | void side_call_variadic(const struct side_event_state *event_state, |
| 90 | const struct side_arg_vec *side_arg_vec, |
| 91 | const struct side_arg_dynamic_struct *var_struct) |
| 92 | { |
| 93 | struct side_rcu_read_state rcu_read_state; |
| 94 | const struct side_callback *side_cb; |
| 95 | uintptr_t enabled; |
| 96 | |
| 97 | if (side_unlikely(finalized)) |
| 98 | return; |
| 99 | if (side_unlikely(!initialized)) |
| 100 | side_init(); |
| 101 | if (side_unlikely(!(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC))) { |
| 102 | printf("ERROR: unexpected non-variadic event description\n"); |
| 103 | abort(); |
| 104 | } |
| 105 | enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED); |
| 106 | if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { |
| 107 | // TODO: call kernel write. |
| 108 | } |
| 109 | side_rcu_read_begin(&rcu_gp, &rcu_read_state); |
| 110 | for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call_variadic != NULL; side_cb++) |
| 111 | side_cb->u.call_variadic(event_state->desc, side_arg_vec, var_struct, side_cb->priv); |
| 112 | side_rcu_read_end(&rcu_gp, &rcu_read_state); |
| 113 | } |
| 114 | |
| 115 | static |
| 116 | const struct side_callback *side_tracer_callback_lookup( |
| 117 | const struct side_event_description *desc, |
| 118 | void *call, void *priv) |
| 119 | { |
| 120 | struct side_event_state *event_state = side_ptr_get(desc->state); |
| 121 | const struct side_callback *cb; |
| 122 | |
| 123 | for (cb = event_state->callbacks; cb->u.call != NULL; cb++) { |
| 124 | if ((void *) cb->u.call == call && cb->priv == priv) |
| 125 | return cb; |
| 126 | } |
| 127 | return NULL; |
| 128 | } |
| 129 | |
| 130 | static |
| 131 | int _side_tracer_callback_register(struct side_event_description *desc, |
| 132 | void *call, void *priv) |
| 133 | { |
| 134 | struct side_event_state *event_state; |
| 135 | struct side_callback *old_cb, *new_cb; |
| 136 | int ret = SIDE_ERROR_OK; |
| 137 | uint32_t old_nr_cb; |
| 138 | |
| 139 | if (!call) |
| 140 | return SIDE_ERROR_INVAL; |
| 141 | if (finalized) |
| 142 | return SIDE_ERROR_EXITING; |
| 143 | if (!initialized) |
| 144 | side_init(); |
| 145 | pthread_mutex_lock(&side_lock); |
| 146 | event_state = side_ptr_get(desc->state); |
| 147 | old_nr_cb = desc->nr_callbacks; |
| 148 | if (old_nr_cb == UINT32_MAX) { |
| 149 | ret = SIDE_ERROR_INVAL; |
| 150 | goto unlock; |
| 151 | } |
| 152 | /* Reject duplicate (call, priv) tuples. */ |
| 153 | if (side_tracer_callback_lookup(desc, call, priv)) { |
| 154 | ret = SIDE_ERROR_EXIST; |
| 155 | goto unlock; |
| 156 | } |
| 157 | old_cb = (struct side_callback *) event_state->callbacks; |
| 158 | /* old_nr_cb + 1 (new cb) + 1 (NULL) */ |
| 159 | new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback)); |
| 160 | if (!new_cb) { |
| 161 | ret = SIDE_ERROR_NOMEM; |
| 162 | goto unlock; |
| 163 | } |
| 164 | memcpy(new_cb, old_cb, old_nr_cb); |
| 165 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) |
| 166 | new_cb[old_nr_cb].u.call_variadic = |
| 167 | (side_tracer_callback_variadic_func) call; |
| 168 | else |
| 169 | new_cb[old_nr_cb].u.call = |
| 170 | (side_tracer_callback_func) call; |
| 171 | new_cb[old_nr_cb].priv = priv; |
| 172 | side_rcu_assign_pointer(event_state->callbacks, new_cb); |
| 173 | side_rcu_wait_grace_period(&rcu_gp); |
| 174 | if (old_nr_cb) |
| 175 | free(old_cb); |
| 176 | desc->nr_callbacks++; |
| 177 | /* Increment concurrently with kernel setting the top bits. */ |
| 178 | if (!old_nr_cb) |
| 179 | (void) __atomic_add_fetch(&event_state->enabled, 1, __ATOMIC_RELAXED); |
| 180 | unlock: |
| 181 | pthread_mutex_unlock(&side_lock); |
| 182 | return ret; |
| 183 | } |
| 184 | |
| 185 | int side_tracer_callback_register(struct side_event_description *desc, |
| 186 | side_tracer_callback_func call, |
| 187 | void *priv) |
| 188 | { |
| 189 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) |
| 190 | return SIDE_ERROR_INVAL; |
| 191 | return _side_tracer_callback_register(desc, (void *) call, priv); |
| 192 | } |
| 193 | |
| 194 | int side_tracer_callback_variadic_register(struct side_event_description *desc, |
| 195 | side_tracer_callback_variadic_func call_variadic, |
| 196 | void *priv) |
| 197 | { |
| 198 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) |
| 199 | return SIDE_ERROR_INVAL; |
| 200 | return _side_tracer_callback_register(desc, (void *) call_variadic, priv); |
| 201 | } |
| 202 | |
| 203 | static int _side_tracer_callback_unregister(struct side_event_description *desc, |
| 204 | void *call, void *priv) |
| 205 | { |
| 206 | struct side_event_state *event_state; |
| 207 | struct side_callback *old_cb, *new_cb; |
| 208 | const struct side_callback *cb_pos; |
| 209 | uint32_t pos_idx; |
| 210 | int ret = SIDE_ERROR_OK; |
| 211 | uint32_t old_nr_cb; |
| 212 | |
| 213 | if (!call) |
| 214 | return SIDE_ERROR_INVAL; |
| 215 | if (finalized) |
| 216 | return SIDE_ERROR_EXITING; |
| 217 | if (!initialized) |
| 218 | side_init(); |
| 219 | pthread_mutex_lock(&side_lock); |
| 220 | event_state = side_ptr_get(desc->state); |
| 221 | cb_pos = side_tracer_callback_lookup(desc, call, priv); |
| 222 | if (!cb_pos) { |
| 223 | ret = SIDE_ERROR_NOENT; |
| 224 | goto unlock; |
| 225 | } |
| 226 | old_nr_cb = desc->nr_callbacks; |
| 227 | old_cb = (struct side_callback *) event_state->callbacks; |
| 228 | if (old_nr_cb == 1) { |
| 229 | new_cb = (struct side_callback *) &side_empty_callback; |
| 230 | } else { |
| 231 | pos_idx = cb_pos - event_state->callbacks; |
| 232 | /* Remove entry at pos_idx. */ |
| 233 | /* old_nr_cb - 1 (removed cb) + 1 (NULL) */ |
| 234 | new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback)); |
| 235 | if (!new_cb) { |
| 236 | ret = SIDE_ERROR_NOMEM; |
| 237 | goto unlock; |
| 238 | } |
| 239 | memcpy(new_cb, old_cb, pos_idx); |
| 240 | memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1); |
| 241 | } |
| 242 | side_rcu_assign_pointer(event_state->callbacks, new_cb); |
| 243 | side_rcu_wait_grace_period(&rcu_gp); |
| 244 | free(old_cb); |
| 245 | desc->nr_callbacks--; |
| 246 | /* Decrement concurrently with kernel setting the top bits. */ |
| 247 | if (old_nr_cb == 1) |
| 248 | (void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED); |
| 249 | unlock: |
| 250 | pthread_mutex_unlock(&side_lock); |
| 251 | return ret; |
| 252 | } |
| 253 | |
| 254 | int side_tracer_callback_unregister(struct side_event_description *desc, |
| 255 | side_tracer_callback_func call, |
| 256 | void *priv) |
| 257 | { |
| 258 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) |
| 259 | return SIDE_ERROR_INVAL; |
| 260 | return _side_tracer_callback_unregister(desc, (void *) call, priv); |
| 261 | } |
| 262 | |
| 263 | int side_tracer_callback_variadic_unregister(struct side_event_description *desc, |
| 264 | side_tracer_callback_variadic_func call_variadic, |
| 265 | void *priv) |
| 266 | { |
| 267 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) |
| 268 | return SIDE_ERROR_INVAL; |
| 269 | return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv); |
| 270 | } |
| 271 | |
| 272 | struct side_events_register_handle *side_events_register(struct side_event_description **events, uint32_t nr_events) |
| 273 | { |
| 274 | struct side_events_register_handle *events_handle = NULL; |
| 275 | struct side_tracer_handle *tracer_handle; |
| 276 | |
| 277 | if (finalized) |
| 278 | return NULL; |
| 279 | if (!initialized) |
| 280 | side_init(); |
| 281 | events_handle = (struct side_events_register_handle *) |
| 282 | calloc(1, sizeof(struct side_events_register_handle)); |
| 283 | if (!events_handle) |
| 284 | return NULL; |
| 285 | events_handle->events = events; |
| 286 | events_handle->nr_events = nr_events; |
| 287 | |
| 288 | pthread_mutex_lock(&side_lock); |
| 289 | side_list_insert_node_tail(&side_events_list, &events_handle->node); |
| 290 | side_list_for_each_entry(tracer_handle, &side_tracer_list, node) { |
| 291 | tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS, |
| 292 | events, nr_events, tracer_handle->priv); |
| 293 | } |
| 294 | pthread_mutex_unlock(&side_lock); |
| 295 | //TODO: call event batch register ioctl |
| 296 | return events_handle; |
| 297 | } |
| 298 | |
| 299 | static |
| 300 | void side_event_remove_callbacks(struct side_event_description *desc) |
| 301 | { |
| 302 | struct side_event_state *event_state = side_ptr_get(desc->state); |
| 303 | uint32_t nr_cb = desc->nr_callbacks; |
| 304 | struct side_callback *old_cb; |
| 305 | |
| 306 | if (!nr_cb) |
| 307 | return; |
| 308 | old_cb = (struct side_callback *) event_state->callbacks; |
| 309 | (void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED); |
| 310 | /* |
| 311 | * Setting the state back to 0 cb and empty callbacks out of |
| 312 | * caution. This should not matter because instrumentation is |
| 313 | * unreachable. |
| 314 | */ |
| 315 | desc->nr_callbacks = 0; |
| 316 | side_rcu_assign_pointer(event_state->callbacks, &side_empty_callback); |
| 317 | /* |
| 318 | * No need to wait for grace period because instrumentation is |
| 319 | * unreachable. |
| 320 | */ |
| 321 | free(old_cb); |
| 322 | } |
| 323 | |
| 324 | /* |
| 325 | * Unregister event handle. At this point, all side events in that |
| 326 | * handle should be unreachable. |
| 327 | */ |
| 328 | void side_events_unregister(struct side_events_register_handle *events_handle) |
| 329 | { |
| 330 | struct side_tracer_handle *tracer_handle; |
| 331 | uint32_t i; |
| 332 | |
| 333 | if (!events_handle) |
| 334 | return; |
| 335 | if (finalized) |
| 336 | return; |
| 337 | if (!initialized) |
| 338 | side_init(); |
| 339 | pthread_mutex_lock(&side_lock); |
| 340 | side_list_remove_node(&events_handle->node); |
| 341 | side_list_for_each_entry(tracer_handle, &side_tracer_list, node) { |
| 342 | tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS, |
| 343 | events_handle->events, events_handle->nr_events, |
| 344 | tracer_handle->priv); |
| 345 | } |
| 346 | for (i = 0; i < events_handle->nr_events; i++) { |
| 347 | struct side_event_description *event = events_handle->events[i]; |
| 348 | |
| 349 | /* Skip NULL pointers */ |
| 350 | if (!event) |
| 351 | continue; |
| 352 | side_event_remove_callbacks(event); |
| 353 | } |
| 354 | pthread_mutex_unlock(&side_lock); |
| 355 | //TODO: call event batch unregister ioctl |
| 356 | free(events_handle); |
| 357 | } |
| 358 | |
| 359 | struct side_tracer_handle *side_tracer_event_notification_register( |
| 360 | void (*cb)(enum side_tracer_notification notif, |
| 361 | struct side_event_description **events, uint32_t nr_events, void *priv), |
| 362 | void *priv) |
| 363 | { |
| 364 | struct side_tracer_handle *tracer_handle; |
| 365 | struct side_events_register_handle *events_handle; |
| 366 | |
| 367 | if (finalized) |
| 368 | return NULL; |
| 369 | if (!initialized) |
| 370 | side_init(); |
| 371 | tracer_handle = (struct side_tracer_handle *) |
| 372 | calloc(1, sizeof(struct side_tracer_handle)); |
| 373 | if (!tracer_handle) |
| 374 | return NULL; |
| 375 | pthread_mutex_lock(&side_lock); |
| 376 | tracer_handle->cb = cb; |
| 377 | tracer_handle->priv = priv; |
| 378 | side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node); |
| 379 | side_list_for_each_entry(events_handle, &side_events_list, node) { |
| 380 | cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS, |
| 381 | events_handle->events, events_handle->nr_events, priv); |
| 382 | } |
| 383 | pthread_mutex_unlock(&side_lock); |
| 384 | return tracer_handle; |
| 385 | } |
| 386 | |
| 387 | void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle) |
| 388 | { |
| 389 | struct side_events_register_handle *events_handle; |
| 390 | |
| 391 | if (finalized) |
| 392 | return; |
| 393 | if (!initialized) |
| 394 | side_init(); |
| 395 | pthread_mutex_lock(&side_lock); |
| 396 | side_list_for_each_entry(events_handle, &side_events_list, node) { |
| 397 | tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS, |
| 398 | events_handle->events, events_handle->nr_events, |
| 399 | tracer_handle->priv); |
| 400 | } |
| 401 | side_list_remove_node(&tracer_handle->node); |
| 402 | pthread_mutex_unlock(&side_lock); |
| 403 | free(tracer_handle); |
| 404 | } |
| 405 | |
| 406 | void side_init(void) |
| 407 | { |
| 408 | if (initialized) |
| 409 | return; |
| 410 | side_rcu_gp_init(&rcu_gp); |
| 411 | initialized = true; |
| 412 | } |
| 413 | |
| 414 | /* |
| 415 | * side_exit() is executed from a library destructor. It can be called |
| 416 | * explicitly at application exit as well. Concurrent side API use is |
| 417 | * not expected at that point. |
| 418 | */ |
| 419 | void side_exit(void) |
| 420 | { |
| 421 | struct side_events_register_handle *handle, *tmp; |
| 422 | |
| 423 | if (finalized) |
| 424 | return; |
| 425 | side_list_for_each_entry_safe(handle, tmp, &side_events_list, node) |
| 426 | side_events_unregister(handle); |
| 427 | side_rcu_gp_exit(&rcu_gp); |
| 428 | finalized = true; |
| 429 | } |