src/side.c

   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 #include <assert.h>
   9
  10 #include "rcu.h"
  11 #include "list.h"
  12
  13 /* Top 8 bits reserved for kernel tracer use. */
  14 #if SIDE_BITS_PER_LONG == 64
  15 # define SIDE_EVENT_ENABLED_KERNEL_MASK                 0xFF00000000000000ULL
  16 # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK      0x8000000000000000ULL
  17
  18 /* Allow 2^56 tracer references on an event. */
  19 # define SIDE_EVENT_ENABLED_USER_MASK                   0x00FFFFFFFFFFFFFFULL
  20 #else
  21 # define SIDE_EVENT_ENABLED_KERNEL_MASK                 0xFF000000UL
  22 # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK      0x80000000UL
  23
  24 /* Allow 2^24 tracer references on an event. */
  25 # define SIDE_EVENT_ENABLED_USER_MASK                   0x00FFFFFFUL
  26 #endif
  27
  28 struct side_events_register_handle {
  29         struct side_list_node node;
  30         struct side_event_description **events;
  31         uint32_t nr_events;
  32 };
  33
  34 struct side_tracer_handle {
  35         struct side_list_node node;
  36         void (*cb)(enum side_tracer_notification notif,
  37                 struct side_event_description **events, uint32_t nr_events, void *priv);
  38         void *priv;
  39 };
  40
  41 struct side_statedump_request_handle {
  42         struct side_list_node node;
  43         void (*cb)(void);
  44 };
  45
  46 struct side_callback {
  47         union {
  48                 void (*call)(const struct side_event_description *desc,
  49                         const struct side_arg_vec *side_arg_vec,
  50                         void *priv);
  51                 void (*call_variadic)(const struct side_event_description *desc,
  52                         const struct side_arg_vec *side_arg_vec,
  53                         const struct side_arg_dynamic_struct *var_struct,
  54                         void *priv);
  55         } u;
  56         void *priv;
  57         void *key;
  58 };
  59
  60 static struct side_rcu_gp_state rcu_gp;
  61
  62 /*
  63  * Lazy initialization for early use within library constructors.
  64  */
  65 static bool initialized;
  66 /*
  67  * Do not register/unregister any more events after destructor.
  68  */
  69 static bool finalized;
  70
  71 /*
  72  * Recursive mutex to allow tracer callbacks to use the side API.
  73  */
  74 static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  75
  76 static DEFINE_SIDE_LIST_HEAD(side_events_list);
  77 static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
  78 static DEFINE_SIDE_LIST_HEAD(side_statedump_list);
  79
  80 /*
  81  * Callback filter key for state dump.
  82  */
  83 static __thread void *filter_key;
  84
  85 /*
  86  * The empty callback has a NULL function callback pointer, which stops
  87  * iteration on the array of callbacks immediately.
  88  */
  89 const char side_empty_callback[sizeof(struct side_callback)];
  90
  91 static
  92 void _side_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec, void *key)
  93 {
  94         struct side_rcu_read_state rcu_read_state;
  95         const struct side_event_state_0 *es0;
  96         const struct side_callback *side_cb;
  97         uintptr_t enabled;
  98
  99         if (side_unlikely(finalized))
 100                 return;
 101         if (side_unlikely(!initialized))
 102                 side_init();
 103         if (side_unlikely(event_state->version != 0))
 104                 abort();
 105         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 106         assert(!(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC));
 107         enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
 108         if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
 109                 // TODO: call kernel write.
 110         }
 111         side_rcu_read_begin(&rcu_gp, &rcu_read_state);
 112         for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call != NULL; side_cb++) {
 113                 /* A NULL key is always a match. */
 114                 if (key && side_cb->key && side_cb->key != key)
 115                         continue;
 116                 side_cb->u.call(es0->desc, side_arg_vec, side_cb->priv);
 117         }
 118         side_rcu_read_end(&rcu_gp, &rcu_read_state);
 119 }
 120
 121 void side_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec)
 122 {
 123         _side_call(event_state, side_arg_vec, NULL);
 124 }
 125
 126 void side_statedump_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec)
 127 {
 128         _side_call(event_state, side_arg_vec, filter_key);
 129 }
 130
 131 static
 132 void _side_call_variadic(const struct side_event_state *event_state,
 133         const struct side_arg_vec *side_arg_vec,
 134         const struct side_arg_dynamic_struct *var_struct,
 135         void *key)
 136 {
 137         struct side_rcu_read_state rcu_read_state;
 138         const struct side_event_state_0 *es0;
 139         const struct side_callback *side_cb;
 140         uintptr_t enabled;
 141
 142         if (side_unlikely(finalized))
 143                 return;
 144         if (side_unlikely(!initialized))
 145                 side_init();
 146         if (side_unlikely(event_state->version != 0))
 147                 abort();
 148         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 149         assert(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC);
 150         enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
 151         if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
 152                 // TODO: call kernel write.
 153         }
 154         side_rcu_read_begin(&rcu_gp, &rcu_read_state);
 155         for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call_variadic != NULL; side_cb++) {
 156                 /* A NULL key is always a match. */
 157                 if (key && side_cb->key && side_cb->key != key)
 158                         continue;
 159                 side_cb->u.call_variadic(es0->desc, side_arg_vec, var_struct, side_cb->priv);
 160         }
 161         side_rcu_read_end(&rcu_gp, &rcu_read_state);
 162 }
 163
 164 void side_call_variadic(const struct side_event_state *event_state,
 165         const struct side_arg_vec *side_arg_vec,
 166         const struct side_arg_dynamic_struct *var_struct)
 167 {
 168         _side_call_variadic(event_state, side_arg_vec, var_struct, NULL);
 169 }
 170
 171 void side_statedump_call_variadic(const struct side_event_state *event_state,
 172         const struct side_arg_vec *side_arg_vec,
 173         const struct side_arg_dynamic_struct *var_struct)
 174 {
 175         _side_call_variadic(event_state, side_arg_vec, var_struct, filter_key);
 176 }
 177
 178 static
 179 const struct side_callback *side_tracer_callback_lookup(
 180                 const struct side_event_description *desc,
 181                 void *call, void *priv, void *key)
 182 {
 183         struct side_event_state *event_state = side_ptr_get(desc->state);
 184         const struct side_event_state_0 *es0;
 185         const struct side_callback *cb;
 186
 187         if (side_unlikely(event_state->version != 0))
 188                 abort();
 189         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 190         for (cb = es0->callbacks; cb->u.call != NULL; cb++) {
 191                 if ((void *) cb->u.call == call && cb->priv == priv && cb->key == key)
 192                         return cb;
 193         }
 194         return NULL;
 195 }
 196
 197 static
 198 int _side_tracer_callback_register(struct side_event_description *desc,
 199                 void *call, void *priv, void *key)
 200 {
 201         struct side_event_state *event_state;
 202         struct side_callback *old_cb, *new_cb;
 203         struct side_event_state_0 *es0;
 204         int ret = SIDE_ERROR_OK;
 205         uint32_t old_nr_cb;
 206
 207         if (!call)
 208                 return SIDE_ERROR_INVAL;
 209         if (finalized)
 210                 return SIDE_ERROR_EXITING;
 211         if (!initialized)
 212                 side_init();
 213         pthread_mutex_lock(&side_lock);
 214         event_state = side_ptr_get(desc->state);
 215         if (side_unlikely(event_state->version != 0))
 216                 abort();
 217         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 218         old_nr_cb = es0->nr_callbacks;
 219         if (old_nr_cb == UINT32_MAX) {
 220                 ret = SIDE_ERROR_INVAL;
 221                 goto unlock;
 222         }
 223         /* Reject duplicate (call, priv) tuples. */
 224         if (side_tracer_callback_lookup(desc, call, priv, key)) {
 225                 ret = SIDE_ERROR_EXIST;
 226                 goto unlock;
 227         }
 228         old_cb = (struct side_callback *) es0->callbacks;
 229         /* old_nr_cb + 1 (new cb) + 1 (NULL) */
 230         new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
 231         if (!new_cb) {
 232                 ret = SIDE_ERROR_NOMEM;
 233                 goto unlock;
 234         }
 235         memcpy(new_cb, old_cb, old_nr_cb);
 236         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 237                 new_cb[old_nr_cb].u.call_variadic =
 238                         (side_tracer_callback_variadic_func) call;
 239         else
 240                 new_cb[old_nr_cb].u.call =
 241                         (side_tracer_callback_func) call;
 242         new_cb[old_nr_cb].priv = priv;
 243         new_cb[old_nr_cb].key = key;
 244         /* High order bits are already zeroed. */
 245         side_rcu_assign_pointer(es0->callbacks, new_cb);
 246         side_rcu_wait_grace_period(&rcu_gp);
 247         if (old_nr_cb)
 248                 free(old_cb);
 249         es0->nr_callbacks++;
 250         /* Increment concurrently with kernel setting the top bits. */
 251         if (!old_nr_cb)
 252                 (void) __atomic_add_fetch(&es0->enabled, 1, __ATOMIC_RELAXED);
 253 unlock:
 254         pthread_mutex_unlock(&side_lock);
 255         return ret;
 256 }
 257
 258 int side_tracer_callback_register(struct side_event_description *desc,
 259                 side_tracer_callback_func call,
 260                 void *priv, void *key)
 261 {
 262         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 263                 return SIDE_ERROR_INVAL;
 264         return _side_tracer_callback_register(desc, (void *) call, priv, key);
 265 }
 266
 267 int side_tracer_callback_variadic_register(struct side_event_description *desc,
 268                 side_tracer_callback_variadic_func call_variadic,
 269                 void *priv, void *key)
 270 {
 271         if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
 272                 return SIDE_ERROR_INVAL;
 273         return _side_tracer_callback_register(desc, (void *) call_variadic, priv, key);
 274 }
 275
 276 static int _side_tracer_callback_unregister(struct side_event_description *desc,
 277                 void *call, void *priv, void *key)
 278 {
 279         struct side_event_state *event_state;
 280         struct side_callback *old_cb, *new_cb;
 281         const struct side_callback *cb_pos;
 282         struct side_event_state_0 *es0;
 283         uint32_t pos_idx;
 284         int ret = SIDE_ERROR_OK;
 285         uint32_t old_nr_cb;
 286
 287         if (!call)
 288                 return SIDE_ERROR_INVAL;
 289         if (finalized)
 290                 return SIDE_ERROR_EXITING;
 291         if (!initialized)
 292                 side_init();
 293         pthread_mutex_lock(&side_lock);
 294         event_state = side_ptr_get(desc->state);
 295         if (side_unlikely(event_state->version != 0))
 296                 abort();
 297         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 298         cb_pos = side_tracer_callback_lookup(desc, call, priv, key);
 299         if (!cb_pos) {
 300                 ret = SIDE_ERROR_NOENT;
 301                 goto unlock;
 302         }
 303         old_nr_cb = es0->nr_callbacks;
 304         old_cb = (struct side_callback *) es0->callbacks;
 305         if (old_nr_cb == 1) {
 306                 new_cb = (struct side_callback *) &side_empty_callback;
 307         } else {
 308                 pos_idx = cb_pos - es0->callbacks;
 309                 /* Remove entry at pos_idx. */
 310                 /* old_nr_cb - 1 (removed cb) + 1 (NULL) */
 311                 new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
 312                 if (!new_cb) {
 313                         ret = SIDE_ERROR_NOMEM;
 314                         goto unlock;
 315                 }
 316                 memcpy(new_cb, old_cb, pos_idx);
 317                 memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
 318         }
 319         /* High order bits are already zeroed. */
 320         side_rcu_assign_pointer(es0->callbacks, new_cb);
 321         side_rcu_wait_grace_period(&rcu_gp);
 322         free(old_cb);
 323         es0->nr_callbacks--;
 324         /* Decrement concurrently with kernel setting the top bits. */
 325         if (old_nr_cb == 1)
 326                 (void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
 327 unlock:
 328         pthread_mutex_unlock(&side_lock);
 329         return ret;
 330 }
 331
 332 int side_tracer_callback_unregister(struct side_event_description *desc,
 333                 side_tracer_callback_func call,
 334                 void *priv, void *key)
 335 {
 336         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 337                 return SIDE_ERROR_INVAL;
 338         return _side_tracer_callback_unregister(desc, (void *) call, priv, key);
 339 }
 340
 341 int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
 342                 side_tracer_callback_variadic_func call_variadic,
 343                 void *priv, void *key)
 344 {
 345         if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
 346                 return SIDE_ERROR_INVAL;
 347         return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv, key);
 348 }
 349
 350 struct side_events_register_handle *side_events_register(struct side_event_description **events, uint32_t nr_events)
 351 {
 352         struct side_events_register_handle *events_handle = NULL;
 353         struct side_tracer_handle *tracer_handle;
 354
 355         if (finalized)
 356                 return NULL;
 357         if (!initialized)
 358                 side_init();
 359         events_handle = (struct side_events_register_handle *)
 360                         calloc(1, sizeof(struct side_events_register_handle));
 361         if (!events_handle)
 362                 return NULL;
 363         events_handle->events = events;
 364         events_handle->nr_events = nr_events;
 365
 366         pthread_mutex_lock(&side_lock);
 367         side_list_insert_node_tail(&side_events_list, &events_handle->node);
 368         side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
 369                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
 370                         events, nr_events, tracer_handle->priv);
 371         }
 372         pthread_mutex_unlock(&side_lock);
 373         //TODO: call event batch register ioctl
 374         return events_handle;
 375 }
 376
 377 static
 378 void side_event_remove_callbacks(struct side_event_description *desc)
 379 {
 380         struct side_event_state *event_state = side_ptr_get(desc->state);
 381         struct side_event_state_0 *es0;
 382         struct side_callback *old_cb;
 383         uint32_t nr_cb;
 384
 385         if (side_unlikely(event_state->version != 0))
 386                 abort();
 387         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 388         nr_cb = es0->nr_callbacks;
 389         if (!nr_cb)
 390                 return;
 391         old_cb = (struct side_callback *) es0->callbacks;
 392         (void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
 393         /*
 394          * Setting the state back to 0 cb and empty callbacks out of
 395          * caution. This should not matter because instrumentation is
 396          * unreachable.
 397          */
 398         es0->nr_callbacks = 0;
 399         side_rcu_assign_pointer(es0->callbacks, &side_empty_callback);
 400         /*
 401          * No need to wait for grace period because instrumentation is
 402          * unreachable.
 403          */
 404         free(old_cb);
 405 }
 406
 407 /*
 408  * Unregister event handle. At this point, all side events in that
 409  * handle should be unreachable.
 410  */
 411 void side_events_unregister(struct side_events_register_handle *events_handle)
 412 {
 413         struct side_tracer_handle *tracer_handle;
 414         uint32_t i;
 415
 416         if (!events_handle)
 417                 return;
 418         if (finalized)
 419                 return;
 420         if (!initialized)
 421                 side_init();
 422         pthread_mutex_lock(&side_lock);
 423         side_list_remove_node(&events_handle->node);
 424         side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
 425                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
 426                         events_handle->events, events_handle->nr_events,
 427                         tracer_handle->priv);
 428         }
 429         for (i = 0; i < events_handle->nr_events; i++) {
 430                 struct side_event_description *event = events_handle->events[i];
 431
 432                 /* Skip NULL pointers */
 433                 if (!event)
 434                         continue;
 435                 side_event_remove_callbacks(event);
 436         }
 437         pthread_mutex_unlock(&side_lock);
 438         //TODO: call event batch unregister ioctl
 439         free(events_handle);
 440 }
 441
 442 struct side_tracer_handle *side_tracer_event_notification_register(
 443                 void (*cb)(enum side_tracer_notification notif,
 444                         struct side_event_description **events, uint32_t nr_events, void *priv),
 445                 void *priv)
 446 {
 447         struct side_tracer_handle *tracer_handle;
 448         struct side_events_register_handle *events_handle;
 449
 450         if (finalized)
 451                 return NULL;
 452         if (!initialized)
 453                 side_init();
 454         tracer_handle = (struct side_tracer_handle *)
 455                                 calloc(1, sizeof(struct side_tracer_handle));
 456         if (!tracer_handle)
 457                 return NULL;
 458         pthread_mutex_lock(&side_lock);
 459         tracer_handle->cb = cb;
 460         tracer_handle->priv = priv;
 461         side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
 462         side_list_for_each_entry(events_handle, &side_events_list, node) {
 463                 cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
 464                         events_handle->events, events_handle->nr_events, priv);
 465         }
 466         pthread_mutex_unlock(&side_lock);
 467         return tracer_handle;
 468 }
 469
 470 void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
 471 {
 472         struct side_events_register_handle *events_handle;
 473
 474         if (finalized)
 475                 return;
 476         if (!initialized)
 477                 side_init();
 478         pthread_mutex_lock(&side_lock);
 479         side_list_for_each_entry(events_handle, &side_events_list, node) {
 480                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
 481                         events_handle->events, events_handle->nr_events,
 482                         tracer_handle->priv);
 483         }
 484         side_list_remove_node(&tracer_handle->node);
 485         pthread_mutex_unlock(&side_lock);
 486         free(tracer_handle);
 487 }
 488
 489 struct side_statedump_request_handle *side_statedump_request_notification_register(void (*statedump_cb)(void))
 490 {
 491         struct side_statedump_request_handle *handle;
 492
 493         if (finalized)
 494                 return NULL;
 495         if (!initialized)
 496                 side_init();
 497         /*
 498          * The statedump request notification should not be registered
 499          * from a notification callback.
 500          */
 501         assert(filter_key == NULL);
 502         handle = (struct side_statedump_request_handle *)
 503                                 calloc(1, sizeof(struct side_statedump_request_handle));
 504         if (!handle)
 505                 return NULL;
 506         pthread_mutex_lock(&side_lock);
 507         handle->cb = statedump_cb;
 508         side_list_insert_node_tail(&side_statedump_list, &handle->node);
 509         /* Invoke callback for all tracers. */
 510         statedump_cb();
 511         pthread_mutex_unlock(&side_lock);
 512         return handle;
 513 }
 514
 515 void side_statedump_request_notification_unregister(struct side_statedump_request_handle *handle)
 516 {
 517         if (finalized)
 518                 return;
 519         if (!initialized)
 520                 side_init();
 521         assert(filter_key == NULL);
 522         pthread_mutex_lock(&side_lock);
 523         side_list_remove_node(&handle->node);
 524         pthread_mutex_unlock(&side_lock);
 525         free(handle);
 526 }
 527
 528 void side_tracer_statedump_request(void *key)
 529 {
 530         struct side_statedump_request_handle *handle;
 531
 532         /* Invoke the state dump callback specifically for the tracer key. */
 533         filter_key = key;
 534         pthread_mutex_lock(&side_lock);
 535         side_list_for_each_entry(handle, &side_statedump_list, node)
 536                 handle->cb();
 537         pthread_mutex_unlock(&side_lock);
 538         filter_key = NULL;
 539 }
 540
 541 void side_init(void)
 542 {
 543         if (initialized)
 544                 return;
 545         side_rcu_gp_init(&rcu_gp);
 546         initialized = true;
 547 }
 548
 549 /*
 550  * side_exit() is executed from a library destructor. It can be called
 551  * explicitly at application exit as well. Concurrent side API use is
 552  * not expected at that point.
 553  */
 554 void side_exit(void)
 555 {
 556         struct side_events_register_handle *handle, *tmp;
 557
 558         if (finalized)
 559                 return;
 560         side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
 561                 side_events_unregister(handle);
 562         side_rcu_gp_exit(&rcu_gp);
 563         finalized = true;
 564 }