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 #include "rculist.h"
  13
  14 /* Top 8 bits reserved for kernel tracer use. */
  15 #if SIDE_BITS_PER_LONG == 64
  16 # define SIDE_EVENT_ENABLED_KERNEL_MASK                 0xFF00000000000000ULL
  17 # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK      0x8000000000000000ULL
  18
  19 /* Allow 2^56 tracer references on an event. */
  20 # define SIDE_EVENT_ENABLED_USER_MASK                   0x00FFFFFFFFFFFFFFULL
  21 #else
  22 # define SIDE_EVENT_ENABLED_KERNEL_MASK                 0xFF000000UL
  23 # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK      0x80000000UL
  24
  25 /* Allow 2^24 tracer references on an event. */
  26 # define SIDE_EVENT_ENABLED_USER_MASK                   0x00FFFFFFUL
  27 #endif
  28
  29 struct side_events_register_handle {
  30         struct side_list_node node;
  31         struct side_event_description **events;
  32         uint32_t nr_events;
  33 };
  34
  35 struct side_tracer_handle {
  36         struct side_list_node node;
  37         void (*cb)(enum side_tracer_notification notif,
  38                 struct side_event_description **events, uint32_t nr_events, void *priv);
  39         void *priv;
  40 };
  41
  42 struct side_statedump_request_handle {
  43         struct side_list_node node;     /* RCU list. */
  44         void (*cb)(void);
  45 };
  46
  47 struct side_callback {
  48         union {
  49                 void (*call)(const struct side_event_description *desc,
  50                         const struct side_arg_vec *side_arg_vec,
  51                         void *priv);
  52                 void (*call_variadic)(const struct side_event_description *desc,
  53                         const struct side_arg_vec *side_arg_vec,
  54                         const struct side_arg_dynamic_struct *var_struct,
  55                         void *priv);
  56         } u;
  57         void *priv;
  58         void *key;
  59 };
  60
  61 static struct side_rcu_gp_state event_rcu_gp, statedump_rcu_gp;
  62
  63 /*
  64  * Lazy initialization for early use within library constructors.
  65  */
  66 static bool initialized;
  67 /*
  68  * Do not register/unregister any more events after destructor.
  69  */
  70 static bool finalized;
  71
  72 /*
  73  * Recursive mutex to allow tracer callbacks to use the side API.
  74  */
  75 static pthread_mutex_t side_event_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  76 static pthread_mutex_t side_statedump_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  77
  78 static DEFINE_SIDE_LIST_HEAD(side_events_list);
  79 static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
  80 static DEFINE_SIDE_LIST_HEAD(side_statedump_list);
  81
  82 /*
  83  * Callback filter key for state dump.
  84  */
  85 static __thread void *filter_key;
  86
  87 /*
  88  * The empty callback has a NULL function callback pointer, which stops
  89  * iteration on the array of callbacks immediately.
  90  */
  91 const char side_empty_callback[sizeof(struct side_callback)];
  92
  93 static
  94 void _side_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec, void *key)
  95 {
  96         struct side_rcu_read_state rcu_read_state;
  97         const struct side_event_state_0 *es0;
  98         const struct side_callback *side_cb;
  99         uintptr_t enabled;
 100
 101         if (side_unlikely(finalized))
 102                 return;
 103         if (side_unlikely(!initialized))
 104                 side_init();
 105         if (side_unlikely(event_state->version != 0))
 106                 abort();
 107         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 108         assert(!(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC));
 109         enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
 110         if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
 111                 // TODO: call kernel write.
 112         }
 113         side_rcu_read_begin(&event_rcu_gp, &rcu_read_state);
 114         for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call != NULL; side_cb++) {
 115                 /* A NULL key is always a match. */
 116                 if (key && side_cb->key && side_cb->key != key)
 117                         continue;
 118                 side_cb->u.call(es0->desc, side_arg_vec, side_cb->priv);
 119         }
 120         side_rcu_read_end(&event_rcu_gp, &rcu_read_state);
 121 }
 122
 123 void side_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec)
 124 {
 125         _side_call(event_state, side_arg_vec, NULL);
 126 }
 127
 128 void side_statedump_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec)
 129 {
 130         _side_call(event_state, side_arg_vec, filter_key);
 131 }
 132
 133 static
 134 void _side_call_variadic(const struct side_event_state *event_state,
 135         const struct side_arg_vec *side_arg_vec,
 136         const struct side_arg_dynamic_struct *var_struct,
 137         void *key)
 138 {
 139         struct side_rcu_read_state rcu_read_state;
 140         const struct side_event_state_0 *es0;
 141         const struct side_callback *side_cb;
 142         uintptr_t enabled;
 143
 144         if (side_unlikely(finalized))
 145                 return;
 146         if (side_unlikely(!initialized))
 147                 side_init();
 148         if (side_unlikely(event_state->version != 0))
 149                 abort();
 150         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 151         assert(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC);
 152         enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
 153         if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
 154                 // TODO: call kernel write.
 155         }
 156         side_rcu_read_begin(&event_rcu_gp, &rcu_read_state);
 157         for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call_variadic != NULL; side_cb++) {
 158                 /* A NULL key is always a match. */
 159                 if (key && side_cb->key && side_cb->key != key)
 160                         continue;
 161                 side_cb->u.call_variadic(es0->desc, side_arg_vec, var_struct, side_cb->priv);
 162         }
 163         side_rcu_read_end(&event_rcu_gp, &rcu_read_state);
 164 }
 165
 166 void side_call_variadic(const struct side_event_state *event_state,
 167         const struct side_arg_vec *side_arg_vec,
 168         const struct side_arg_dynamic_struct *var_struct)
 169 {
 170         _side_call_variadic(event_state, side_arg_vec, var_struct, NULL);
 171 }
 172
 173 void side_statedump_call_variadic(const struct side_event_state *event_state,
 174         const struct side_arg_vec *side_arg_vec,
 175         const struct side_arg_dynamic_struct *var_struct)
 176 {
 177         _side_call_variadic(event_state, side_arg_vec, var_struct, filter_key);
 178 }
 179
 180 static
 181 const struct side_callback *side_tracer_callback_lookup(
 182                 const struct side_event_description *desc,
 183                 void *call, void *priv, void *key)
 184 {
 185         struct side_event_state *event_state = side_ptr_get(desc->state);
 186         const struct side_event_state_0 *es0;
 187         const struct side_callback *cb;
 188
 189         if (side_unlikely(event_state->version != 0))
 190                 abort();
 191         es0 = side_container_of(event_state, const struct side_event_state_0, parent);
 192         for (cb = es0->callbacks; cb->u.call != NULL; cb++) {
 193                 if ((void *) cb->u.call == call && cb->priv == priv && cb->key == key)
 194                         return cb;
 195         }
 196         return NULL;
 197 }
 198
 199 static
 200 int _side_tracer_callback_register(struct side_event_description *desc,
 201                 void *call, void *priv, void *key)
 202 {
 203         struct side_event_state *event_state;
 204         struct side_callback *old_cb, *new_cb;
 205         struct side_event_state_0 *es0;
 206         int ret = SIDE_ERROR_OK;
 207         uint32_t old_nr_cb;
 208
 209         if (!call)
 210                 return SIDE_ERROR_INVAL;
 211         if (finalized)
 212                 return SIDE_ERROR_EXITING;
 213         if (!initialized)
 214                 side_init();
 215         pthread_mutex_lock(&side_event_lock);
 216         event_state = side_ptr_get(desc->state);
 217         if (side_unlikely(event_state->version != 0))
 218                 abort();
 219         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 220         old_nr_cb = es0->nr_callbacks;
 221         if (old_nr_cb == UINT32_MAX) {
 222                 ret = SIDE_ERROR_INVAL;
 223                 goto unlock;
 224         }
 225         /* Reject duplicate (call, priv) tuples. */
 226         if (side_tracer_callback_lookup(desc, call, priv, key)) {
 227                 ret = SIDE_ERROR_EXIST;
 228                 goto unlock;
 229         }
 230         old_cb = (struct side_callback *) es0->callbacks;
 231         /* old_nr_cb + 1 (new cb) + 1 (NULL) */
 232         new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
 233         if (!new_cb) {
 234                 ret = SIDE_ERROR_NOMEM;
 235                 goto unlock;
 236         }
 237         memcpy(new_cb, old_cb, old_nr_cb);
 238         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 239                 new_cb[old_nr_cb].u.call_variadic =
 240                         (side_tracer_callback_variadic_func) call;
 241         else
 242                 new_cb[old_nr_cb].u.call =
 243                         (side_tracer_callback_func) call;
 244         new_cb[old_nr_cb].priv = priv;
 245         new_cb[old_nr_cb].key = key;
 246         /* High order bits are already zeroed. */
 247         side_rcu_assign_pointer(es0->callbacks, new_cb);
 248         side_rcu_wait_grace_period(&event_rcu_gp);
 249         if (old_nr_cb)
 250                 free(old_cb);
 251         es0->nr_callbacks++;
 252         /* Increment concurrently with kernel setting the top bits. */
 253         if (!old_nr_cb)
 254                 (void) __atomic_add_fetch(&es0->enabled, 1, __ATOMIC_RELAXED);
 255 unlock:
 256         pthread_mutex_unlock(&side_event_lock);
 257         return ret;
 258 }
 259
 260 int side_tracer_callback_register(struct side_event_description *desc,
 261                 side_tracer_callback_func call,
 262                 void *priv, void *key)
 263 {
 264         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 265                 return SIDE_ERROR_INVAL;
 266         return _side_tracer_callback_register(desc, (void *) call, priv, key);
 267 }
 268
 269 int side_tracer_callback_variadic_register(struct side_event_description *desc,
 270                 side_tracer_callback_variadic_func call_variadic,
 271                 void *priv, void *key)
 272 {
 273         if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
 274                 return SIDE_ERROR_INVAL;
 275         return _side_tracer_callback_register(desc, (void *) call_variadic, priv, key);
 276 }
 277
 278 static int _side_tracer_callback_unregister(struct side_event_description *desc,
 279                 void *call, void *priv, void *key)
 280 {
 281         struct side_event_state *event_state;
 282         struct side_callback *old_cb, *new_cb;
 283         const struct side_callback *cb_pos;
 284         struct side_event_state_0 *es0;
 285         uint32_t pos_idx;
 286         int ret = SIDE_ERROR_OK;
 287         uint32_t old_nr_cb;
 288
 289         if (!call)
 290                 return SIDE_ERROR_INVAL;
 291         if (finalized)
 292                 return SIDE_ERROR_EXITING;
 293         if (!initialized)
 294                 side_init();
 295         pthread_mutex_lock(&side_event_lock);
 296         event_state = side_ptr_get(desc->state);
 297         if (side_unlikely(event_state->version != 0))
 298                 abort();
 299         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 300         cb_pos = side_tracer_callback_lookup(desc, call, priv, key);
 301         if (!cb_pos) {
 302                 ret = SIDE_ERROR_NOENT;
 303                 goto unlock;
 304         }
 305         old_nr_cb = es0->nr_callbacks;
 306         old_cb = (struct side_callback *) es0->callbacks;
 307         if (old_nr_cb == 1) {
 308                 new_cb = (struct side_callback *) &side_empty_callback;
 309         } else {
 310                 pos_idx = cb_pos - es0->callbacks;
 311                 /* Remove entry at pos_idx. */
 312                 /* old_nr_cb - 1 (removed cb) + 1 (NULL) */
 313                 new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
 314                 if (!new_cb) {
 315                         ret = SIDE_ERROR_NOMEM;
 316                         goto unlock;
 317                 }
 318                 memcpy(new_cb, old_cb, pos_idx);
 319                 memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
 320         }
 321         /* High order bits are already zeroed. */
 322         side_rcu_assign_pointer(es0->callbacks, new_cb);
 323         side_rcu_wait_grace_period(&event_rcu_gp);
 324         free(old_cb);
 325         es0->nr_callbacks--;
 326         /* Decrement concurrently with kernel setting the top bits. */
 327         if (old_nr_cb == 1)
 328                 (void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
 329 unlock:
 330         pthread_mutex_unlock(&side_event_lock);
 331         return ret;
 332 }
 333
 334 int side_tracer_callback_unregister(struct side_event_description *desc,
 335                 side_tracer_callback_func call,
 336                 void *priv, void *key)
 337 {
 338         if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
 339                 return SIDE_ERROR_INVAL;
 340         return _side_tracer_callback_unregister(desc, (void *) call, priv, key);
 341 }
 342
 343 int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
 344                 side_tracer_callback_variadic_func call_variadic,
 345                 void *priv, void *key)
 346 {
 347         if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
 348                 return SIDE_ERROR_INVAL;
 349         return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv, key);
 350 }
 351
 352 struct side_events_register_handle *side_events_register(struct side_event_description **events, uint32_t nr_events)
 353 {
 354         struct side_events_register_handle *events_handle = NULL;
 355         struct side_tracer_handle *tracer_handle;
 356
 357         if (finalized)
 358                 return NULL;
 359         if (!initialized)
 360                 side_init();
 361         events_handle = (struct side_events_register_handle *)
 362                         calloc(1, sizeof(struct side_events_register_handle));
 363         if (!events_handle)
 364                 return NULL;
 365         events_handle->events = events;
 366         events_handle->nr_events = nr_events;
 367
 368         pthread_mutex_lock(&side_event_lock);
 369         side_list_insert_node_tail(&side_events_list, &events_handle->node);
 370         side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
 371                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
 372                         events, nr_events, tracer_handle->priv);
 373         }
 374         pthread_mutex_unlock(&side_event_lock);
 375         //TODO: call event batch register ioctl
 376         return events_handle;
 377 }
 378
 379 static
 380 void side_event_remove_callbacks(struct side_event_description *desc)
 381 {
 382         struct side_event_state *event_state = side_ptr_get(desc->state);
 383         struct side_event_state_0 *es0;
 384         struct side_callback *old_cb;
 385         uint32_t nr_cb;
 386
 387         if (side_unlikely(event_state->version != 0))
 388                 abort();
 389         es0 = side_container_of(event_state, struct side_event_state_0, parent);
 390         nr_cb = es0->nr_callbacks;
 391         if (!nr_cb)
 392                 return;
 393         old_cb = (struct side_callback *) es0->callbacks;
 394         (void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
 395         /*
 396          * Setting the state back to 0 cb and empty callbacks out of
 397          * caution. This should not matter because instrumentation is
 398          * unreachable.
 399          */
 400         es0->nr_callbacks = 0;
 401         side_rcu_assign_pointer(es0->callbacks, &side_empty_callback);
 402         /*
 403          * No need to wait for grace period because instrumentation is
 404          * unreachable.
 405          */
 406         free(old_cb);
 407 }
 408
 409 /*
 410  * Unregister event handle. At this point, all side events in that
 411  * handle should be unreachable.
 412  */
 413 void side_events_unregister(struct side_events_register_handle *events_handle)
 414 {
 415         struct side_tracer_handle *tracer_handle;
 416         uint32_t i;
 417
 418         if (!events_handle)
 419                 return;
 420         if (finalized)
 421                 return;
 422         if (!initialized)
 423                 side_init();
 424         pthread_mutex_lock(&side_event_lock);
 425         side_list_remove_node(&events_handle->node);
 426         side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
 427                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
 428                         events_handle->events, events_handle->nr_events,
 429                         tracer_handle->priv);
 430         }
 431         for (i = 0; i < events_handle->nr_events; i++) {
 432                 struct side_event_description *event = events_handle->events[i];
 433
 434                 /* Skip NULL pointers */
 435                 if (!event)
 436                         continue;
 437                 side_event_remove_callbacks(event);
 438         }
 439         pthread_mutex_unlock(&side_event_lock);
 440         //TODO: call event batch unregister ioctl
 441         free(events_handle);
 442 }
 443
 444 struct side_tracer_handle *side_tracer_event_notification_register(
 445                 void (*cb)(enum side_tracer_notification notif,
 446                         struct side_event_description **events, uint32_t nr_events, void *priv),
 447                 void *priv)
 448 {
 449         struct side_tracer_handle *tracer_handle;
 450         struct side_events_register_handle *events_handle;
 451
 452         if (finalized)
 453                 return NULL;
 454         if (!initialized)
 455                 side_init();
 456         tracer_handle = (struct side_tracer_handle *)
 457                                 calloc(1, sizeof(struct side_tracer_handle));
 458         if (!tracer_handle)
 459                 return NULL;
 460         pthread_mutex_lock(&side_event_lock);
 461         tracer_handle->cb = cb;
 462         tracer_handle->priv = priv;
 463         side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
 464         side_list_for_each_entry(events_handle, &side_events_list, node) {
 465                 cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
 466                         events_handle->events, events_handle->nr_events, priv);
 467         }
 468         pthread_mutex_unlock(&side_event_lock);
 469         return tracer_handle;
 470 }
 471
 472 void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
 473 {
 474         struct side_events_register_handle *events_handle;
 475
 476         if (finalized)
 477                 return;
 478         if (!initialized)
 479                 side_init();
 480         pthread_mutex_lock(&side_event_lock);
 481         side_list_for_each_entry(events_handle, &side_events_list, node) {
 482                 tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
 483                         events_handle->events, events_handle->nr_events,
 484                         tracer_handle->priv);
 485         }
 486         side_list_remove_node(&tracer_handle->node);
 487         pthread_mutex_unlock(&side_event_lock);
 488         free(tracer_handle);
 489 }
 490
 491 struct side_statedump_request_handle *side_statedump_request_notification_register(void (*statedump_cb)(void))
 492 {
 493         struct side_statedump_request_handle *handle;
 494
 495         if (finalized)
 496                 return NULL;
 497         if (!initialized)
 498                 side_init();
 499         /*
 500          * The statedump request notification should not be registered
 501          * from a notification callback.
 502          */
 503         assert(filter_key == NULL);
 504         handle = (struct side_statedump_request_handle *)
 505                                 calloc(1, sizeof(struct side_statedump_request_handle));
 506         if (!handle)
 507                 return NULL;
 508         handle->cb = statedump_cb;
 509
 510         pthread_mutex_lock(&side_statedump_lock);
 511         side_list_insert_node_tail_rcu(&side_statedump_list, &handle->node);
 512         pthread_mutex_unlock(&side_statedump_lock);
 513
 514         /* Invoke callback for all tracers. */
 515         statedump_cb();
 516
 517         return handle;
 518 }
 519
 520 void side_statedump_request_notification_unregister(struct side_statedump_request_handle *handle)
 521 {
 522         if (finalized)
 523                 return;
 524         if (!initialized)
 525                 side_init();
 526         assert(filter_key == NULL);
 527
 528         pthread_mutex_lock(&side_statedump_lock);
 529         side_list_remove_node_rcu(&handle->node);
 530         pthread_mutex_unlock(&side_statedump_lock);
 531
 532         side_rcu_wait_grace_period(&statedump_rcu_gp);
 533         free(handle);
 534 }
 535
 536 void side_tracer_statedump_request(void *key)
 537 {
 538         struct side_statedump_request_handle *handle;
 539         struct side_rcu_read_state rcu_read_state;
 540
 541         /* Invoke the state dump callback specifically for the tracer key. */
 542         filter_key = key;
 543         side_rcu_read_begin(&statedump_rcu_gp, &rcu_read_state);
 544         side_list_for_each_entry_rcu(handle, &side_statedump_list, node)
 545                 handle->cb();
 546         side_rcu_read_end(&statedump_rcu_gp, &rcu_read_state);
 547         filter_key = NULL;
 548 }
 549
 550 void side_init(void)
 551 {
 552         if (initialized)
 553                 return;
 554         side_rcu_gp_init(&event_rcu_gp);
 555         side_rcu_gp_init(&statedump_rcu_gp);
 556         initialized = true;
 557 }
 558
 559 /*
 560  * side_exit() is executed from a library destructor. It can be called
 561  * explicitly at application exit as well. Concurrent side API use is
 562  * not expected at that point.
 563  */
 564 void side_exit(void)
 565 {
 566         struct side_events_register_handle *handle, *tmp;
 567
 568         if (finalized)
 569                 return;
 570         side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
 571                 side_events_unregister(handle);
 572         side_rcu_gp_exit(&event_rcu_gp);
 573         side_rcu_gp_exit(&statedump_rcu_gp);
 574         finalized = true;
 575 }