src/common/event.cpp

   1 /*
   2  * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #include <common/align.hpp>
   9 #include <common/buffer-view.hpp>
  10 #include <common/compat/string.hpp>
  11 #include <common/dynamic-array.hpp>
  12 #include <common/dynamic-buffer.hpp>
  13 #include <common/error.hpp>
  14 #include <common/macros.hpp>
  15 #include <common/sessiond-comm/sessiond-comm.hpp>
  16
  17 #include <lttng/constant.h>
  18 #include <lttng/event-internal.hpp>
  19 #include <lttng/event.h>
  20 #include <lttng/lttng-error.h>
  21 #include <lttng/userspace-probe-internal.hpp>
  22
  23 namespace {
  24 struct event_list_element {
  25         struct lttng_event *event;
  26         struct lttng_event_exclusion *exclusions;
  27         char *filter_expression;
  28 };
  29 } /* namespace */
  30
  31 static void event_list_destructor(void *ptr)
  32 {
  33         struct event_list_element *element = (struct event_list_element *) ptr;
  34
  35         free(element->filter_expression);
  36         free(element->exclusions);
  37         lttng_event_destroy(element->event);
  38         free(element);
  39 }
  40
  41 struct lttng_event *lttng_event_copy(const struct lttng_event *event)
  42 {
  43         struct lttng_event *new_event;
  44         struct lttng_event_extended *new_event_extended;
  45
  46         new_event = zmalloc<lttng_event>();
  47         if (!new_event) {
  48                 PERROR("Error allocating event structure");
  49                 goto end;
  50         }
  51
  52         /* Copy the content of the old event. */
  53         memcpy(new_event, event, sizeof(*event));
  54
  55         /*
  56          * We need to create a new extended since the previous pointer is now
  57          * invalid.
  58          */
  59         new_event_extended = zmalloc<lttng_event_extended>();
  60         if (!new_event_extended) {
  61                 PERROR("Error allocating event extended structure");
  62                 goto error;
  63         }
  64
  65         new_event->extended.ptr = new_event_extended;
  66 end:
  67         return new_event;
  68 error:
  69         free(new_event);
  70         new_event = nullptr;
  71         goto end;
  72 }
  73
  74 static int lttng_event_probe_attr_serialize(const struct lttng_event_probe_attr *probe,
  75                                             struct lttng_payload *payload)
  76 {
  77         int ret;
  78         size_t symbol_name_len;
  79         struct lttng_event_probe_attr_comm comm = {};
  80
  81         symbol_name_len = lttng_strnlen(probe->symbol_name, sizeof(probe->symbol_name));
  82         if (symbol_name_len == sizeof(probe->symbol_name)) {
  83                 /* Not null-termintated. */
  84                 ret = -1;
  85                 goto end;
  86         }
  87
  88         /* Include the null terminator. */
  89         symbol_name_len += 1;
  90
  91         comm.symbol_name_len = (uint32_t) symbol_name_len;
  92         comm.addr = probe->addr;
  93         comm.offset = probe->addr;
  94
  95         ret = lttng_dynamic_buffer_append(&payload->buffer, &comm, sizeof(comm));
  96         if (ret < 0) {
  97                 ret = -1;
  98                 goto end;
  99         }
 100
 101         ret = lttng_dynamic_buffer_append(&payload->buffer, probe->symbol_name, symbol_name_len);
 102 end:
 103         return ret;
 104 }
 105
 106 static int lttng_event_function_attr_serialize(const struct lttng_event_function_attr *function,
 107                                                struct lttng_payload *payload)
 108 {
 109         int ret;
 110         size_t symbol_name_len;
 111         struct lttng_event_function_attr_comm comm;
 112
 113         comm.symbol_name_len = 0;
 114
 115         symbol_name_len = lttng_strnlen(function->symbol_name, sizeof(function->symbol_name));
 116         if (symbol_name_len == sizeof(function->symbol_name)) {
 117                 /* Not null-termintated. */
 118                 ret = -1;
 119                 goto end;
 120         }
 121
 122         /* Include the null terminator. */
 123         symbol_name_len += 1;
 124
 125         comm.symbol_name_len = (uint32_t) symbol_name_len;
 126
 127         ret = lttng_dynamic_buffer_append(&payload->buffer, &comm, sizeof(comm));
 128         if (ret < 0) {
 129                 ret = -1;
 130                 goto end;
 131         }
 132
 133         ret = lttng_dynamic_buffer_append(&payload->buffer, function->symbol_name, symbol_name_len);
 134 end:
 135         return ret;
 136 }
 137
 138 static ssize_t
 139 lttng_event_probe_attr_create_from_payload(struct lttng_payload_view *view,
 140                                            struct lttng_event_probe_attr **probe_attr)
 141 {
 142         ssize_t ret, offset = 0;
 143         const struct lttng_event_probe_attr_comm *comm;
 144         struct lttng_event_probe_attr *local_attr = nullptr;
 145         struct lttng_payload_view comm_view =
 146                 lttng_payload_view_from_view(view, offset, sizeof(*comm));
 147
 148         if (!lttng_payload_view_is_valid(&comm_view)) {
 149                 ret = -1;
 150                 goto end;
 151         }
 152
 153         comm = (typeof(comm)) comm_view.buffer.data;
 154         offset += sizeof(*comm);
 155
 156         local_attr = zmalloc<lttng_event_probe_attr>();
 157         if (local_attr == nullptr) {
 158                 ret = -1;
 159                 goto end;
 160         }
 161
 162         local_attr->addr = comm->addr;
 163         local_attr->offset = comm->offset;
 164
 165         {
 166                 const char *name;
 167                 struct lttng_payload_view name_view =
 168                         lttng_payload_view_from_view(view, offset, comm->symbol_name_len);
 169
 170                 if (!lttng_payload_view_is_valid(&name_view)) {
 171                         ret = -1;
 172                         goto end;
 173                 }
 174
 175                 name = name_view.buffer.data;
 176
 177                 if (!lttng_buffer_view_contains_string(
 178                             &name_view.buffer, name, comm->symbol_name_len)) {
 179                         ret = -1;
 180                         goto end;
 181                 }
 182
 183                 ret = lttng_strncpy(local_attr->symbol_name, name, sizeof(local_attr->symbol_name));
 184                 if (ret) {
 185                         ret = -1;
 186                         goto end;
 187                 }
 188
 189                 offset += comm->symbol_name_len;
 190         }
 191
 192         *probe_attr = local_attr;
 193         local_attr = nullptr;
 194         ret = offset;
 195 end:
 196         free(local_attr);
 197         return ret;
 198 }
 199
 200 static ssize_t
 201 lttng_event_function_attr_create_from_payload(struct lttng_payload_view *view,
 202                                               struct lttng_event_function_attr **function_attr)
 203 {
 204         ssize_t ret, offset = 0;
 205         const struct lttng_event_function_attr_comm *comm;
 206         struct lttng_event_function_attr *local_attr = nullptr;
 207         struct lttng_payload_view comm_view =
 208                 lttng_payload_view_from_view(view, offset, sizeof(*comm));
 209
 210         if (!lttng_payload_view_is_valid(&comm_view)) {
 211                 ret = -1;
 212                 goto end;
 213         }
 214
 215         comm = (typeof(comm)) view->buffer.data;
 216         offset += sizeof(*comm);
 217
 218         local_attr = zmalloc<lttng_event_function_attr>();
 219         if (local_attr == nullptr) {
 220                 ret = -1;
 221                 goto end;
 222         }
 223
 224         {
 225                 const char *name;
 226                 struct lttng_payload_view name_view =
 227                         lttng_payload_view_from_view(view, offset, comm->symbol_name_len);
 228
 229                 if (!lttng_payload_view_is_valid(&name_view)) {
 230                         ret = -1;
 231                         goto end;
 232                 }
 233
 234                 name = name_view.buffer.data;
 235
 236                 if (!lttng_buffer_view_contains_string(
 237                             &name_view.buffer, name, comm->symbol_name_len)) {
 238                         ret = -1;
 239                         goto end;
 240                 }
 241
 242                 ret = lttng_strncpy(local_attr->symbol_name, name, sizeof(local_attr->symbol_name));
 243                 if (ret) {
 244                         ret = -1;
 245                         goto end;
 246                 }
 247
 248                 offset += comm->symbol_name_len;
 249         }
 250
 251         *function_attr = local_attr;
 252         local_attr = nullptr;
 253         ret = offset;
 254 end:
 255         free(local_attr);
 256         return ret;
 257 }
 258
 259 static ssize_t lttng_event_exclusions_create_from_payload(struct lttng_payload_view *view,
 260                                                           uint32_t count,
 261                                                           struct lttng_event_exclusion **exclusions)
 262 {
 263         ssize_t ret, offset = 0;
 264         const size_t size = (count * LTTNG_SYMBOL_NAME_LEN);
 265         uint32_t i;
 266         const struct lttng_event_exclusion_comm *comm;
 267         struct lttng_event_exclusion *local_exclusions;
 268
 269         local_exclusions =
 270                 zmalloc<lttng_event_exclusion>(sizeof(struct lttng_event_exclusion) + size);
 271         if (!local_exclusions) {
 272                 ret = -1;
 273                 goto end;
 274         }
 275
 276         local_exclusions->count = count;
 277
 278         for (i = 0; i < count; i++) {
 279                 const char *string;
 280                 struct lttng_buffer_view string_view;
 281                 const struct lttng_buffer_view comm_view =
 282                         lttng_buffer_view_from_view(&view->buffer, offset, sizeof(*comm));
 283
 284                 if (!lttng_buffer_view_is_valid(&comm_view)) {
 285                         ret = -1;
 286                         goto end;
 287                 }
 288
 289                 comm = (typeof(comm)) comm_view.data;
 290                 offset += sizeof(*comm);
 291
 292                 string_view = lttng_buffer_view_from_view(&view->buffer, offset, comm->len);
 293
 294                 if (!lttng_buffer_view_is_valid(&string_view)) {
 295                         ret = -1;
 296                         goto end;
 297                 }
 298
 299                 string = string_view.data;
 300
 301                 if (!lttng_buffer_view_contains_string(&string_view, string, comm->len)) {
 302                         ret = -1;
 303                         goto end;
 304                 }
 305
 306                 ret = lttng_strncpy(LTTNG_EVENT_EXCLUSION_NAME_AT(local_exclusions, i),
 307                                     string,
 308                                     sizeof(LTTNG_EVENT_EXCLUSION_NAME_AT(local_exclusions, i)));
 309                 if (ret) {
 310                         ret = -1;
 311                         goto end;
 312                 }
 313
 314                 offset += comm->len;
 315         }
 316
 317         *exclusions = local_exclusions;
 318         local_exclusions = nullptr;
 319         ret = offset;
 320 end:
 321         free(local_exclusions);
 322         return ret;
 323 }
 324
 325 ssize_t lttng_event_create_from_payload(struct lttng_payload_view *view,
 326                                         struct lttng_event **out_event,
 327                                         struct lttng_event_exclusion **out_exclusion,
 328                                         char **out_filter_expression,
 329                                         struct lttng_bytecode **out_bytecode)
 330 {
 331         ssize_t ret, offset = 0;
 332         struct lttng_event *local_event = nullptr;
 333         struct lttng_event_exclusion *local_exclusions = nullptr;
 334         struct lttng_bytecode *local_bytecode = nullptr;
 335         char *local_filter_expression = nullptr;
 336         const struct lttng_event_comm *event_comm;
 337         struct lttng_event_function_attr *local_function_attr = nullptr;
 338         struct lttng_event_probe_attr *local_probe_attr = nullptr;
 339         struct lttng_userspace_probe_location *local_userspace_probe_location = nullptr;
 340
 341         /*
 342          * Only event is obligatory, the other output argument are optional and
 343          * depends on what the caller is interested in.
 344          */
 345         assert(out_event);
 346         assert(view);
 347
 348         {
 349                 struct lttng_payload_view comm_view =
 350                         lttng_payload_view_from_view(view, offset, sizeof(*event_comm));
 351
 352                 if (!lttng_payload_view_is_valid(&comm_view)) {
 353                         ret = -1;
 354                         goto end;
 355                 }
 356
 357                 /* lttng_event_comm header */
 358                 event_comm = (typeof(event_comm)) comm_view.buffer.data;
 359                 offset += sizeof(*event_comm);
 360         }
 361
 362         local_event = lttng_event_create();
 363         if (local_event == nullptr) {
 364                 ret = -1;
 365                 goto end;
 366         }
 367
 368         local_event->type = (enum lttng_event_type) event_comm->event_type;
 369         local_event->loglevel_type = (enum lttng_loglevel_type) event_comm->loglevel_type;
 370         local_event->loglevel =
 371                 local_event->loglevel_type == LTTNG_EVENT_LOGLEVEL_ALL ? -1 : event_comm->loglevel;
 372         local_event->enabled = !!event_comm->enabled;
 373         local_event->pid = event_comm->pid;
 374         local_event->flags = (enum lttng_event_flag) event_comm->flags;
 375
 376         {
 377                 const char *name;
 378                 const struct lttng_buffer_view name_view =
 379                         lttng_buffer_view_from_view(&view->buffer, offset, event_comm->name_len);
 380
 381                 if (!lttng_buffer_view_is_valid(&name_view)) {
 382                         ret = -1;
 383                         goto end;
 384                 }
 385
 386                 name = (const char *) name_view.data;
 387
 388                 if (!lttng_buffer_view_contains_string(&name_view, name, event_comm->name_len)) {
 389                         ret = -1;
 390                         goto end;
 391                 }
 392
 393                 ret = lttng_strncpy(local_event->name, name, sizeof(local_event->name));
 394                 if (ret) {
 395                         ret = -1;
 396                         goto end;
 397                 }
 398
 399                 offset += event_comm->name_len;
 400         }
 401
 402         /* Exclusions */
 403         if (event_comm->exclusion_count == 0) {
 404                 goto deserialize_filter_expression;
 405         }
 406
 407         {
 408                 struct lttng_payload_view exclusions_view =
 409                         lttng_payload_view_from_view(view, offset, -1);
 410
 411                 if (!lttng_payload_view_is_valid(&exclusions_view)) {
 412                         ret = -1;
 413                         goto end;
 414                 }
 415
 416                 ret = lttng_event_exclusions_create_from_payload(
 417                         &exclusions_view, event_comm->exclusion_count, &local_exclusions);
 418                 if (ret < 0) {
 419                         ret = -1;
 420                         goto end;
 421                 }
 422                 offset += ret;
 423
 424                 local_event->exclusion = 1;
 425         }
 426
 427 deserialize_filter_expression:
 428
 429         if (event_comm->filter_expression_len == 0) {
 430                 if (event_comm->bytecode_len != 0) {
 431                         /*
 432                          * This is an invalid event payload.
 433                          *
 434                          * Filter expression without bytecode is possible but
 435                          * not the other way around.
 436                          * */
 437                         ret = -1;
 438                         goto end;
 439                 }
 440                 goto deserialize_event_type_payload;
 441         }
 442
 443         {
 444                 const char *filter_expression_buffer;
 445                 struct lttng_buffer_view filter_expression_view = lttng_buffer_view_from_view(
 446                         &view->buffer, offset, event_comm->filter_expression_len);
 447
 448                 if (!lttng_buffer_view_is_valid(&filter_expression_view)) {
 449                         ret = -1;
 450                         goto end;
 451                 }
 452
 453                 filter_expression_buffer = filter_expression_view.data;
 454
 455                 if (!lttng_buffer_view_contains_string(&filter_expression_view,
 456                                                        filter_expression_buffer,
 457                                                        event_comm->filter_expression_len)) {
 458                         ret = -1;
 459                         goto end;
 460                 }
 461
 462                 local_filter_expression =
 463                         lttng_strndup(filter_expression_buffer, event_comm->filter_expression_len);
 464                 if (!local_filter_expression) {
 465                         ret = -1;
 466                         goto end;
 467                 }
 468
 469                 local_event->filter = 1;
 470
 471                 offset += event_comm->filter_expression_len;
 472         }
 473
 474         if (event_comm->bytecode_len == 0) {
 475                 /*
 476                  * Filter expression can be present but without bytecode
 477                  * when dealing with event listing.
 478                  */
 479                 goto deserialize_event_type_payload;
 480         }
 481
 482         /* Bytecode */
 483         {
 484                 struct lttng_payload_view bytecode_view =
 485                         lttng_payload_view_from_view(view, offset, event_comm->bytecode_len);
 486
 487                 if (!lttng_payload_view_is_valid(&bytecode_view)) {
 488                         ret = -1;
 489                         goto end;
 490                 }
 491
 492                 local_bytecode = zmalloc<lttng_bytecode>(event_comm->bytecode_len);
 493                 if (!local_bytecode) {
 494                         ret = -1;
 495                         goto end;
 496                 }
 497
 498                 memcpy(local_bytecode, bytecode_view.buffer.data, event_comm->bytecode_len);
 499                 if ((local_bytecode->len + sizeof(*local_bytecode)) != event_comm->bytecode_len) {
 500                         ret = -1;
 501                         goto end;
 502                 }
 503
 504                 offset += event_comm->bytecode_len;
 505         }
 506
 507 deserialize_event_type_payload:
 508         /* Event type specific payload */
 509         switch (local_event->type) {
 510         case LTTNG_EVENT_FUNCTION:
 511                 /* Fallthrough */
 512         case LTTNG_EVENT_PROBE:
 513         {
 514                 struct lttng_payload_view probe_attr_view = lttng_payload_view_from_view(
 515                         view, offset, event_comm->lttng_event_probe_attr_len);
 516
 517                 if (event_comm->lttng_event_probe_attr_len == 0) {
 518                         ret = -1;
 519                         goto end;
 520                 }
 521
 522                 if (!lttng_payload_view_is_valid(&probe_attr_view)) {
 523                         ret = -1;
 524                         goto end;
 525                 }
 526
 527                 ret = lttng_event_probe_attr_create_from_payload(&probe_attr_view,
 528                                                                  &local_probe_attr);
 529                 if (ret < 0 || ret != event_comm->lttng_event_probe_attr_len) {
 530                         ret = -1;
 531                         goto end;
 532                 }
 533
 534                 /* Copy to the local event. */
 535                 memcpy(&local_event->attr.probe, local_probe_attr, sizeof(local_event->attr.probe));
 536
 537                 offset += ret;
 538                 break;
 539         }
 540         case LTTNG_EVENT_FUNCTION_ENTRY:
 541         {
 542                 struct lttng_payload_view function_attr_view = lttng_payload_view_from_view(
 543                         view, offset, event_comm->lttng_event_function_attr_len);
 544
 545                 if (event_comm->lttng_event_function_attr_len == 0) {
 546                         ret = -1;
 547                         goto end;
 548                 }
 549
 550                 if (!lttng_payload_view_is_valid(&function_attr_view)) {
 551                         ret = -1;
 552                         goto end;
 553                 }
 554
 555                 ret = lttng_event_function_attr_create_from_payload(&function_attr_view,
 556                                                                     &local_function_attr);
 557                 if (ret < 0 || ret != event_comm->lttng_event_function_attr_len) {
 558                         ret = -1;
 559                         goto end;
 560                 }
 561
 562                 /* Copy to the local event. */
 563                 memcpy(&local_event->attr.ftrace,
 564                        local_function_attr,
 565                        sizeof(local_event->attr.ftrace));
 566
 567                 offset += ret;
 568
 569                 break;
 570         }
 571         case LTTNG_EVENT_USERSPACE_PROBE:
 572         {
 573                 struct lttng_payload_view userspace_probe_location_view =
 574                         lttng_payload_view_from_view(
 575                                 view, offset, event_comm->userspace_probe_location_len);
 576
 577                 if (event_comm->userspace_probe_location_len == 0) {
 578                         ret = -1;
 579                         goto end;
 580                 }
 581
 582                 if (!lttng_payload_view_is_valid(&userspace_probe_location_view)) {
 583                         ret = -1;
 584                         goto end;
 585                 }
 586
 587                 ret = lttng_userspace_probe_location_create_from_payload(
 588                         &userspace_probe_location_view, &local_userspace_probe_location);
 589                 if (ret < 0) {
 590                         WARN("Failed to create a userspace probe location from the received buffer");
 591                         ret = -1;
 592                         goto end;
 593                 }
 594
 595                 if (ret != event_comm->userspace_probe_location_len) {
 596                         WARN("Userspace probe location from the received buffer is not the advertised length: header length = %" PRIu32
 597                              ", payload length = %zd",
 598                              event_comm->userspace_probe_location_len,
 599                              ret);
 600                         ret = -1;
 601                         goto end;
 602                 }
 603
 604                 /* Attach the probe location to the event. */
 605                 ret = lttng_event_set_userspace_probe_location(local_event,
 606                                                                local_userspace_probe_location);
 607                 if (ret) {
 608                         ret = LTTNG_ERR_PROBE_LOCATION_INVAL;
 609                         goto end;
 610                 }
 611
 612                 /*
 613                  * Userspace probe location object ownership transfered to the
 614                  * event object.
 615                  */
 616                 local_userspace_probe_location = nullptr;
 617                 offset += event_comm->userspace_probe_location_len;
 618                 break;
 619         }
 620         case LTTNG_EVENT_TRACEPOINT:
 621                 /* Fallthrough */
 622         case LTTNG_EVENT_ALL:
 623                 /* Fallthrough */
 624         case LTTNG_EVENT_SYSCALL:
 625                 /* Fallthrough */
 626         case LTTNG_EVENT_NOOP:
 627                 /* Nothing to do here */
 628                 break;
 629         default:
 630                 ret = LTTNG_ERR_UND;
 631                 goto end;
 632                 break;
 633         }
 634
 635         /* Transfer ownership to the caller. */
 636         *out_event = local_event;
 637         local_event = nullptr;
 638
 639         if (out_bytecode) {
 640                 *out_bytecode = local_bytecode;
 641                 local_bytecode = nullptr;
 642         }
 643
 644         if (out_exclusion) {
 645                 *out_exclusion = local_exclusions;
 646                 local_exclusions = nullptr;
 647         }
 648
 649         if (out_filter_expression) {
 650                 *out_filter_expression = local_filter_expression;
 651                 local_filter_expression = nullptr;
 652         }
 653
 654         ret = offset;
 655 end:
 656         lttng_event_destroy(local_event);
 657         lttng_userspace_probe_location_destroy(local_userspace_probe_location);
 658         free(local_filter_expression);
 659         free(local_exclusions);
 660         free(local_bytecode);
 661         free(local_function_attr);
 662         free(local_probe_attr);
 663         return ret;
 664 }
 665
 666 int lttng_event_serialize(const struct lttng_event *event,
 667                           unsigned int exclusion_count,
 668                           const char *const *exclusion_list,
 669                           const char *filter_expression,
 670                           size_t bytecode_len,
 671                           struct lttng_bytecode *bytecode,
 672                           struct lttng_payload *payload)
 673 {
 674         int ret;
 675         unsigned int i;
 676         size_t header_offset, size_before_payload;
 677         size_t name_len;
 678         struct lttng_event_comm event_comm = {};
 679         struct lttng_event_comm *header;
 680
 681         assert(event);
 682         assert(payload);
 683         assert(exclusion_count == 0 || exclusion_list);
 684
 685         /* Save the header location for later in-place header update. */
 686         header_offset = payload->buffer.size;
 687
 688         name_len = lttng_strnlen(event->name, sizeof(event->name));
 689         if (name_len == sizeof(event->name)) {
 690                 /* Event name is not NULL-terminated. */
 691                 ret = -1;
 692                 goto end;
 693         }
 694
 695         /* Add null termination. */
 696         name_len += 1;
 697
 698         if (exclusion_count > UINT32_MAX) {
 699                 /* Possible overflow. */
 700                 ret = -1;
 701                 goto end;
 702         }
 703
 704         if (bytecode_len > UINT32_MAX) {
 705                 /* Possible overflow. */
 706                 ret = -1;
 707                 goto end;
 708         }
 709
 710         event_comm.name_len = (uint32_t) name_len;
 711         event_comm.event_type = (int8_t) event->type;
 712         event_comm.loglevel_type = (int8_t) event->loglevel_type;
 713         event_comm.loglevel = (int32_t) event->loglevel;
 714         event_comm.enabled = (int8_t) event->enabled;
 715         event_comm.pid = (int32_t) event->pid;
 716         event_comm.exclusion_count = (uint32_t) exclusion_count;
 717         event_comm.bytecode_len = (uint32_t) bytecode_len;
 718         event_comm.flags = (int32_t) event->flags;
 719
 720         if (filter_expression) {
 721                 event_comm.filter_expression_len = strlen(filter_expression) + 1;
 722         }
 723
 724         /* Header */
 725         ret = lttng_dynamic_buffer_append(&payload->buffer, &event_comm, sizeof(event_comm));
 726         if (ret) {
 727                 goto end;
 728         }
 729
 730         /* Event name */
 731         ret = lttng_dynamic_buffer_append(&payload->buffer, event->name, name_len);
 732         if (ret) {
 733                 goto end;
 734         }
 735
 736         /* Exclusions */
 737         for (i = 0; i < exclusion_count; i++) {
 738                 const size_t exclusion_len =
 739                         lttng_strnlen(*(exclusion_list + i), LTTNG_SYMBOL_NAME_LEN);
 740                 struct lttng_event_exclusion_comm exclusion_header = {};
 741
 742                 exclusion_header.len = (uint32_t) exclusion_len + 1;
 743
 744                 if (exclusion_len == LTTNG_SYMBOL_NAME_LEN) {
 745                         /* Exclusion is not NULL-terminated. */
 746                         ret = -1;
 747                         goto end;
 748                 }
 749
 750                 ret = lttng_dynamic_buffer_append(
 751                         &payload->buffer, &exclusion_header, sizeof(exclusion_header));
 752                 if (ret) {
 753                         goto end;
 754                 }
 755
 756                 ret = lttng_dynamic_buffer_append(
 757                         &payload->buffer, *(exclusion_list + i), exclusion_len + 1);
 758                 if (ret) {
 759                         goto end;
 760                 }
 761         }
 762
 763         /* Filter expression and its bytecode */
 764         if (filter_expression) {
 765                 ret = lttng_dynamic_buffer_append(
 766                         &payload->buffer, filter_expression, event_comm.filter_expression_len);
 767                 if (ret) {
 768                         goto end;
 769                 }
 770
 771                 /*
 772                  * Bytecode can be absent when we serialize to the client
 773                  * for listing.
 774                  */
 775                 if (bytecode) {
 776                         ret = lttng_dynamic_buffer_append(&payload->buffer, bytecode, bytecode_len);
 777                         if (ret) {
 778                                 goto end;
 779                         }
 780                 }
 781         }
 782
 783         size_before_payload = payload->buffer.size;
 784
 785         /* Event type specific payload */
 786         switch (event->type) {
 787         case LTTNG_EVENT_FUNCTION:
 788                 /* Fallthrough */
 789         case LTTNG_EVENT_PROBE:
 790                 ret = lttng_event_probe_attr_serialize(&event->attr.probe, payload);
 791                 if (ret) {
 792                         ret = -1;
 793                         goto end;
 794                 }
 795
 796                 header =
 797                         (struct lttng_event_comm *) ((char *) payload->buffer.data + header_offset);
 798                 header->lttng_event_probe_attr_len = payload->buffer.size - size_before_payload;
 799
 800                 break;
 801         case LTTNG_EVENT_FUNCTION_ENTRY:
 802                 ret = lttng_event_function_attr_serialize(&event->attr.ftrace, payload);
 803                 if (ret) {
 804                         ret = -1;
 805                         goto end;
 806                 }
 807
 808                 /* Update the lttng_event_function_attr len. */
 809                 header =
 810                         (struct lttng_event_comm *) ((char *) payload->buffer.data + header_offset);
 811                 header->lttng_event_function_attr_len = payload->buffer.size - size_before_payload;
 812
 813                 break;
 814         case LTTNG_EVENT_USERSPACE_PROBE:
 815         {
 816                 const struct lttng_event_extended *ev_ext =
 817                         (const struct lttng_event_extended *) event->extended.ptr;
 818
 819                 assert(event->extended.ptr);
 820                 assert(ev_ext->probe_location);
 821
 822                 size_before_payload = payload->buffer.size;
 823                 if (ev_ext->probe_location) {
 824                         /*
 825                          * lttng_userspace_probe_location_serialize returns the
 826                          * number of bytes that were appended to the buffer.
 827                          */
 828                         ret = lttng_userspace_probe_location_serialize(ev_ext->probe_location,
 829                                                                        payload);
 830                         if (ret < 0) {
 831                                 goto end;
 832                         }
 833
 834                         ret = 0;
 835
 836                         /* Update the userspace probe location len. */
 837                         header = (struct lttng_event_comm *) ((char *) payload->buffer.data +
 838                                                               header_offset);
 839                         header->userspace_probe_location_len =
 840                                 payload->buffer.size - size_before_payload;
 841                 }
 842                 break;
 843         }
 844         case LTTNG_EVENT_TRACEPOINT:
 845                 /* Fallthrough */
 846         case LTTNG_EVENT_ALL:
 847                 /* Fallthrough */
 848         default:
 849                 /* Nothing to do here. */
 850                 break;
 851         }
 852
 853 end:
 854         return ret;
 855 }
 856
 857 static ssize_t lttng_event_context_app_populate_from_payload(const struct lttng_payload_view *view,
 858                                                              struct lttng_event_context *event_ctx)
 859 {
 860         ssize_t ret, offset = 0;
 861         const struct lttng_event_context_app_comm *comm;
 862         char *provider_name = nullptr, *context_name = nullptr;
 863         size_t provider_name_len, context_name_len;
 864         const struct lttng_buffer_view comm_view =
 865                 lttng_buffer_view_from_view(&view->buffer, offset, sizeof(*comm));
 866
 867         assert(event_ctx->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT);
 868
 869         if (!lttng_buffer_view_is_valid(&comm_view)) {
 870                 ret = -1;
 871                 goto end;
 872         }
 873
 874         comm = (typeof(comm)) comm_view.data;
 875         offset += sizeof(*comm);
 876
 877         provider_name_len = comm->provider_name_len;
 878         context_name_len = comm->ctx_name_len;
 879
 880         if (provider_name_len == 0 || context_name_len == 0) {
 881                 /*
 882                  * Application provider and context names MUST
 883                  * be provided.
 884                  */
 885                 ret = -1;
 886                 goto end;
 887         }
 888
 889         {
 890                 const char *name;
 891                 const struct lttng_buffer_view provider_name_view =
 892                         lttng_buffer_view_from_view(&view->buffer, offset, provider_name_len);
 893
 894                 if (!lttng_buffer_view_is_valid(&provider_name_view)) {
 895                         ret = -1;
 896                         goto end;
 897                 }
 898
 899                 name = provider_name_view.data;
 900
 901                 if (!lttng_buffer_view_contains_string(
 902                             &provider_name_view, name, provider_name_len)) {
 903                         ret = -1;
 904                         goto end;
 905                 }
 906
 907                 provider_name = lttng_strndup(name, provider_name_len);
 908                 if (!provider_name) {
 909                         ret = -1;
 910                         goto end;
 911                 }
 912
 913                 offset += provider_name_len;
 914         }
 915
 916         {
 917                 const char *name;
 918                 const struct lttng_buffer_view context_name_view =
 919                         lttng_buffer_view_from_view(&view->buffer, offset, context_name_len);
 920
 921                 if (!lttng_buffer_view_is_valid(&context_name_view)) {
 922                         ret = -1;
 923                         goto end;
 924                 }
 925
 926                 name = context_name_view.data;
 927
 928                 if (!lttng_buffer_view_contains_string(&context_name_view, name, context_name_len)) {
 929                         ret = -1;
 930                         goto end;
 931                 }
 932
 933                 context_name = lttng_strndup(name, context_name_len);
 934                 if (!context_name) {
 935                         ret = -1;
 936                         goto end;
 937                 }
 938
 939                 offset += context_name_len;
 940         }
 941
 942         /* Transfer ownership of the strings */
 943         event_ctx->u.app_ctx.provider_name = provider_name;
 944         event_ctx->u.app_ctx.ctx_name = context_name;
 945         provider_name = nullptr;
 946         context_name = nullptr;
 947
 948         ret = offset;
 949 end:
 950         free(provider_name);
 951         free(context_name);
 952
 953         return ret;
 954 }
 955
 956 static ssize_t
 957 lttng_event_context_perf_counter_populate_from_payload(const struct lttng_payload_view *view,
 958                                                        struct lttng_event_context *event_ctx)
 959 {
 960         int ret;
 961         ssize_t consumed, offset = 0;
 962         const struct lttng_event_context_perf_counter_comm *comm;
 963         size_t name_len;
 964         const struct lttng_buffer_view comm_view =
 965                 lttng_buffer_view_from_view(&view->buffer, offset, sizeof(*comm));
 966
 967         assert(event_ctx->ctx == LTTNG_EVENT_CONTEXT_PERF_COUNTER ||
 968                event_ctx->ctx == LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER ||
 969                event_ctx->ctx == LTTNG_EVENT_CONTEXT_PERF_CPU_COUNTER);
 970
 971         if (!lttng_buffer_view_is_valid(&comm_view)) {
 972                 consumed = -1;
 973                 goto end;
 974         }
 975
 976         comm = (typeof(comm)) comm_view.data;
 977         offset += sizeof(*comm);
 978
 979         name_len = comm->name_len;
 980
 981         {
 982                 const char *name;
 983                 const struct lttng_buffer_view provider_name_view =
 984                         lttng_buffer_view_from_view(&view->buffer, offset, name_len);
 985
 986                 if (!lttng_buffer_view_is_valid(&provider_name_view)) {
 987                         consumed = -1;
 988                         goto end;
 989                 }
 990
 991                 name = provider_name_view.data;
 992
 993                 if (!lttng_buffer_view_contains_string(&provider_name_view, name, name_len)) {
 994                         consumed = -1;
 995                         goto end;
 996                 }
 997
 998                 ret = lttng_strncpy(event_ctx->u.perf_counter.name,
 999                                     name,
1000                                     sizeof(event_ctx->u.perf_counter.name));
1001                 if (ret) {
1002                         consumed = -1;
1003                         goto end;
1004                 }
1005                 offset += name_len;
1006         }
1007
1008         event_ctx->u.perf_counter.config = comm->config;
1009         event_ctx->u.perf_counter.type = comm->type;
1010
1011         consumed = offset;
1012
1013 end:
1014         return consumed;
1015 }
1016
1017 ssize_t lttng_event_context_create_from_payload(struct lttng_payload_view *view,
1018                                                 struct lttng_event_context **event_ctx)
1019 {
1020         ssize_t ret, offset = 0;
1021         const struct lttng_event_context_comm *comm;
1022         struct lttng_event_context *local_context = nullptr;
1023         struct lttng_buffer_view comm_view =
1024                 lttng_buffer_view_from_view(&view->buffer, offset, sizeof(*comm));
1025
1026         assert(event_ctx);
1027         assert(view);
1028
1029         if (!lttng_buffer_view_is_valid(&comm_view)) {
1030                 ret = -1;
1031                 goto end;
1032         }
1033
1034         comm = (typeof(comm)) comm_view.data;
1035         offset += sizeof(*comm);
1036
1037         local_context = zmalloc<lttng_event_context>();
1038         if (!local_context) {
1039                 ret = -1;
1040                 goto end;
1041         }
1042
1043         local_context->ctx = (lttng_event_context_type) comm->type;
1044
1045         {
1046                 struct lttng_payload_view subtype_view =
1047                         lttng_payload_view_from_view(view, offset, -1);
1048
1049                 switch (local_context->ctx) {
1050                 case LTTNG_EVENT_CONTEXT_APP_CONTEXT:
1051                         ret = lttng_event_context_app_populate_from_payload(&subtype_view,
1052                                                                             local_context);
1053                         break;
1054                 case LTTNG_EVENT_CONTEXT_PERF_COUNTER:
1055                 case LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER:
1056                 case LTTNG_EVENT_CONTEXT_PERF_CPU_COUNTER:
1057                         ret = lttng_event_context_perf_counter_populate_from_payload(&subtype_view,
1058                                                                                      local_context);
1059                         break;
1060                 default:
1061                         /* Nothing else to deserialize. */
1062                         ret = 0;
1063                         break;
1064                 }
1065         }
1066
1067         if (ret < 0) {
1068                 goto end;
1069         }
1070
1071         offset += ret;
1072
1073         *event_ctx = local_context;
1074         local_context = nullptr;
1075         ret = offset;
1076
1077 end:
1078         free(local_context);
1079         return ret;
1080 }
1081
1082 static int lttng_event_context_app_serialize(struct lttng_event_context *context,
1083                                              struct lttng_payload *payload)
1084 {
1085         int ret;
1086         struct lttng_event_context_app_comm comm = {};
1087         size_t provider_len, ctx_len;
1088         const char *provider_name;
1089         const char *ctx_name;
1090
1091         assert(payload);
1092         assert(context);
1093         assert(context->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT);
1094
1095         provider_name = context->u.app_ctx.provider_name;
1096         ctx_name = context->u.app_ctx.ctx_name;
1097
1098         if (!provider_name || !ctx_name) {
1099                 ret = -LTTNG_ERR_INVALID;
1100                 goto end;
1101         }
1102
1103         provider_len = strlen(provider_name);
1104         if (provider_len == 0) {
1105                 ret = -LTTNG_ERR_INVALID;
1106                 goto end;
1107         }
1108
1109         /* Include the null terminator. */
1110         provider_len += 1;
1111         comm.provider_name_len = provider_len;
1112
1113         ctx_len = strlen(ctx_name);
1114         if (ctx_len == 0) {
1115                 ret = -LTTNG_ERR_INVALID;
1116                 goto end;
1117         }
1118
1119         /* Include the null terminator. */
1120         ctx_len += 1;
1121         comm.ctx_name_len = ctx_len;
1122
1123         /* Header */
1124         ret = lttng_dynamic_buffer_append(&payload->buffer, &comm, sizeof(comm));
1125         if (ret) {
1126                 ret = -1;
1127                 goto end;
1128         }
1129
1130         ret = lttng_dynamic_buffer_append(&payload->buffer, provider_name, provider_len);
1131         if (ret) {
1132                 ret = -1;
1133                 goto end;
1134         }
1135
1136         ret = lttng_dynamic_buffer_append(&payload->buffer, ctx_name, ctx_len);
1137         if (ret) {
1138                 ret = -1;
1139                 goto end;
1140         }
1141
1142 end:
1143         return ret;
1144 }
1145
1146 static int lttng_event_context_perf_counter_serialize(struct lttng_event_perf_counter_ctx *context,
1147                                                       struct lttng_payload *payload)
1148 {
1149         int ret;
1150         struct lttng_event_context_perf_counter_comm comm = {};
1151
1152         assert(payload);
1153         assert(context);
1154
1155         comm.config = context->config;
1156         comm.type = context->type;
1157         comm.name_len = lttng_strnlen(context->name, sizeof(context->name));
1158
1159         if (comm.name_len == sizeof(context->name)) {
1160                 ret = -1;
1161                 goto end;
1162         }
1163
1164         /* Include the null terminator. */
1165         comm.name_len += 1;
1166
1167         /* Header */
1168         ret = lttng_dynamic_buffer_append(&payload->buffer, &comm, sizeof(comm));
1169         if (ret) {
1170                 ret = -1;
1171                 goto end;
1172         }
1173
1174         ret = lttng_dynamic_buffer_append(&payload->buffer, context->name, comm.name_len);
1175         if (ret) {
1176                 ret = -1;
1177                 goto end;
1178         }
1179
1180 end:
1181         return ret;
1182 }
1183
1184 int lttng_event_context_serialize(struct lttng_event_context *context,
1185                                   struct lttng_payload *payload)
1186 {
1187         int ret;
1188         struct lttng_event_context_comm context_comm;
1189
1190         context_comm.type = 0;
1191
1192         assert(context);
1193         assert(payload);
1194
1195         context_comm.type = (uint32_t) context->ctx;
1196
1197         /* Header */
1198         ret = lttng_dynamic_buffer_append(&payload->buffer, &context_comm, sizeof(context_comm));
1199         if (ret) {
1200                 goto end;
1201         }
1202
1203         switch (context->ctx) {
1204         case LTTNG_EVENT_CONTEXT_APP_CONTEXT:
1205                 ret = lttng_event_context_app_serialize(context, payload);
1206                 break;
1207         case LTTNG_EVENT_CONTEXT_PERF_COUNTER:
1208         case LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER:
1209         case LTTNG_EVENT_CONTEXT_PERF_CPU_COUNTER:
1210                 ret = lttng_event_context_perf_counter_serialize(&context->u.perf_counter, payload);
1211                 break;
1212         default:
1213                 /* Nothing else to serialize. */
1214                 break;
1215         }
1216
1217         if (ret) {
1218                 goto end;
1219         }
1220
1221 end:
1222         return ret;
1223 }
1224
1225 void lttng_event_context_destroy(struct lttng_event_context *context)
1226 {
1227         if (!context) {
1228                 return;
1229         }
1230
1231         if (context->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
1232                 free(context->u.app_ctx.provider_name);
1233                 free(context->u.app_ctx.ctx_name);
1234         }
1235
1236         free(context);
1237 }
1238
1239 /*
1240  * This is a specialized populate for lttng_event_field since it ignores
1241  * the extension field of the lttng_event struct and simply copies what it can
1242  * to the internal struct lttng_event of a lttng_event_field.
1243  */
1244 static void lttng_event_field_populate_lttng_event_from_event(const struct lttng_event *src,
1245                                                               struct lttng_event *destination)
1246 {
1247         memcpy(destination, src, sizeof(*destination));
1248
1249         /* Remove all possible dynamic data from the destination event rule. */
1250         destination->extended.ptr = nullptr;
1251 }
1252
1253 ssize_t lttng_event_field_create_from_payload(struct lttng_payload_view *view,
1254                                               struct lttng_event_field **field)
1255 {
1256         ssize_t ret, offset = 0;
1257         struct lttng_event_field *local_event_field = nullptr;
1258         struct lttng_event *event = nullptr;
1259         const struct lttng_event_field_comm *comm;
1260         const char *name = nullptr;
1261
1262         assert(field);
1263         assert(view);
1264
1265         {
1266                 const struct lttng_buffer_view comm_view =
1267                         lttng_buffer_view_from_view(&view->buffer, offset, sizeof(*comm));
1268
1269                 if (!lttng_buffer_view_is_valid(&comm_view)) {
1270                         ret = -1;
1271                         goto end;
1272                 }
1273
1274                 /* lttng_event_field_comm header */
1275                 comm = (const lttng_event_field_comm *) comm_view.data;
1276                 offset += sizeof(*comm);
1277         }
1278
1279         local_event_field = zmalloc<lttng_event_field>();
1280         if (!local_event_field) {
1281                 ret = -1;
1282                 goto end;
1283         }
1284
1285         local_event_field->type = (lttng_event_field_type) comm->type;
1286         local_event_field->nowrite = comm->nowrite;
1287
1288         /* Field name */
1289         {
1290                 const struct lttng_buffer_view name_view =
1291                         lttng_buffer_view_from_view(&view->buffer, offset, comm->name_len);
1292
1293                 if (!lttng_buffer_view_is_valid(&name_view)) {
1294                         ret = -1;
1295                         goto end;
1296                 }
1297
1298                 name = name_view.data;
1299
1300                 if (!lttng_buffer_view_contains_string(&name_view, name_view.data, comm->name_len)) {
1301                         ret = -1;
1302                         goto end;
1303                 }
1304
1305                 if (comm->name_len > LTTNG_SYMBOL_NAME_LEN - 1) {
1306                         /* Name is too long.*/
1307                         ret = -1;
1308                         goto end;
1309                 }
1310
1311                 offset += comm->name_len;
1312         }
1313
1314         /* Event */
1315         {
1316                 struct lttng_payload_view event_view =
1317                         lttng_payload_view_from_view(view, offset, comm->event_len);
1318
1319                 if (!lttng_payload_view_is_valid(&event_view)) {
1320                         ret = -1;
1321                         goto end;
1322                 }
1323
1324                 ret = lttng_event_create_from_payload(
1325                         &event_view, &event, nullptr, nullptr, nullptr);
1326                 if (ret != comm->event_len) {
1327                         ret = -1;
1328                         goto end;
1329                 }
1330
1331                 offset += ret;
1332         }
1333
1334         assert(name);
1335         assert(event);
1336
1337         if (lttng_strncpy(
1338                     local_event_field->field_name, name, sizeof(local_event_field->field_name))) {
1339                 ret = -1;
1340                 goto end;
1341         }
1342
1343         lttng_event_field_populate_lttng_event_from_event(event, &local_event_field->event);
1344
1345         *field = local_event_field;
1346         local_event_field = nullptr;
1347         ret = offset;
1348 end:
1349         lttng_event_destroy(event);
1350         free(local_event_field);
1351         return ret;
1352 }
1353
1354 int lttng_event_field_serialize(const struct lttng_event_field *field,
1355                                 struct lttng_payload *payload)
1356 {
1357         int ret;
1358         size_t header_offset, size_before_event;
1359         size_t name_len;
1360         struct lttng_event_field_comm event_field_comm = {};
1361         struct lttng_event_field_comm *header;
1362
1363         assert(field);
1364         assert(payload);
1365
1366         /* Save the header location for later in-place header update. */
1367         header_offset = payload->buffer.size;
1368
1369         name_len = strnlen(field->field_name, sizeof(field->field_name));
1370         if (name_len == sizeof(field->field_name)) {
1371                 /* Event name is not NULL-terminated. */
1372                 ret = -1;
1373                 goto end;
1374         }
1375
1376         /* Add null termination. */
1377         name_len += 1;
1378
1379         event_field_comm.type = field->type;
1380         event_field_comm.nowrite = (uint8_t) field->nowrite;
1381         event_field_comm.name_len = name_len;
1382
1383         /* Header */
1384         ret = lttng_dynamic_buffer_append(
1385                 &payload->buffer, &event_field_comm, sizeof(event_field_comm));
1386         if (ret) {
1387                 goto end;
1388         }
1389
1390         /* Field name */
1391         ret = lttng_dynamic_buffer_append(&payload->buffer, field->field_name, name_len);
1392         if (ret) {
1393                 goto end;
1394         }
1395
1396         size_before_event = payload->buffer.size;
1397         ret = lttng_event_serialize(&field->event, 0, nullptr, nullptr, 0, nullptr, payload);
1398         if (ret) {
1399                 ret = -1;
1400                 goto end;
1401         }
1402
1403         /* Update the event len. */
1404         header = (struct lttng_event_field_comm *) ((char *) payload->buffer.data + header_offset);
1405         header->event_len = payload->buffer.size - size_before_event;
1406
1407 end:
1408         return ret;
1409 }
1410
1411 static enum lttng_error_code compute_flattened_size(struct lttng_dynamic_pointer_array *events,
1412                                                     size_t *size)
1413 {
1414         enum lttng_error_code ret_code;
1415         int ret = 0;
1416         size_t storage_req, event_count, i;
1417
1418         assert(size);
1419         assert(events);
1420
1421         event_count = lttng_dynamic_pointer_array_get_count(events);
1422
1423         /* The basic struct lttng_event */
1424         storage_req = event_count * sizeof(struct lttng_event);
1425
1426         /* The struct·lttng_event_extended */
1427         storage_req += event_count * sizeof(struct lttng_event_extended);
1428
1429         for (i = 0; i < event_count; i++) {
1430                 int probe_storage_req = 0;
1431                 const struct event_list_element *element =
1432                         (const struct event_list_element *) lttng_dynamic_pointer_array_get_pointer(
1433                                 events, i);
1434                 const struct lttng_userspace_probe_location *location = nullptr;
1435
1436                 location = lttng_event_get_userspace_probe_location(element->event);
1437                 if (location) {
1438                         ret = lttng_userspace_probe_location_flatten(location, nullptr);
1439                         if (ret < 0) {
1440                                 ret_code = LTTNG_ERR_PROBE_LOCATION_INVAL;
1441                                 goto end;
1442                         }
1443
1444                         probe_storage_req = ret;
1445                 }
1446
1447                 if (element->filter_expression) {
1448                         storage_req += strlen(element->filter_expression) + 1;
1449                 }
1450
1451                 if (element->exclusions) {
1452                         storage_req += element->exclusions->count * LTTNG_SYMBOL_NAME_LEN;
1453                 }
1454
1455                 /* Padding to ensure the flat probe is aligned. */
1456                 storage_req = lttng_align_ceil(storage_req, sizeof(uint64_t));
1457                 storage_req += probe_storage_req;
1458         }
1459
1460         *size = storage_req;
1461         ret_code = LTTNG_OK;
1462
1463 end:
1464         return ret_code;
1465 }
1466
1467 /*
1468  * Flatten a list of struct lttng_event.
1469  *
1470  * The buffer that is returned to the API client  must contain a "flat" version
1471  * of the events that are returned. In other words, all pointers within an
1472  * lttng_event must point to a location within the returned buffer so that the
1473  * user may free everything by simply calling free() on the returned buffer.
1474  * This is needed in order to maintain API compatibility.
1475  *
1476  * A first pass is performed to compute the size of the buffer that must be
1477  * allocated. A second pass is then performed to setup the returned events so
1478  * that their members always point within the buffer.
1479  *
1480  * The layout of the returned buffer is as follows:
1481  *   - struct lttng_event[nb_events],
1482  *   - nb_events times the following:
1483  *     - struct lttng_event_extended,
1484  *     - filter_expression
1485  *     - exclusions
1486  *     - padding to align to 64-bits
1487  *     - flattened version of userspace_probe_location
1488  */
1489 static enum lttng_error_code flatten_lttng_events(struct lttng_dynamic_pointer_array *events,
1490                                                   struct lttng_event **flattened_events)
1491 {
1492         enum lttng_error_code ret_code;
1493         int ret, i;
1494         size_t storage_req;
1495         struct lttng_dynamic_buffer local_flattened_events;
1496         int nb_events;
1497
1498         assert(events);
1499         assert(flattened_events);
1500
1501         lttng_dynamic_buffer_init(&local_flattened_events);
1502         nb_events = lttng_dynamic_pointer_array_get_count(events);
1503
1504         ret_code = compute_flattened_size(events, &storage_req);
1505         if (ret_code != LTTNG_OK) {
1506                 goto end;
1507         }
1508
1509         /*
1510          * We must ensure that "local_flattened_events" is never resized so as
1511          * to preserve the validity of the flattened objects.
1512          */
1513         ret = lttng_dynamic_buffer_set_capacity(&local_flattened_events, storage_req);
1514         if (ret) {
1515                 ret_code = LTTNG_ERR_NOMEM;
1516                 goto end;
1517         }
1518
1519         /* Start by laying the struct lttng_event */
1520         for (i = 0; i < nb_events; i++) {
1521                 const struct event_list_element *element =
1522                         (const struct event_list_element *) lttng_dynamic_pointer_array_get_pointer(
1523                                 events, i);
1524
1525                 if (!element) {
1526                         ret_code = LTTNG_ERR_FATAL;
1527                         goto end;
1528                 }
1529
1530                 ret = lttng_dynamic_buffer_append(
1531                         &local_flattened_events, element->event, sizeof(struct lttng_event));
1532                 if (ret) {
1533                         ret_code = LTTNG_ERR_NOMEM;
1534                         goto end;
1535                 }
1536         }
1537
1538         for (i = 0; i < nb_events; i++) {
1539                 const struct event_list_element *element =
1540                         (const struct event_list_element *) lttng_dynamic_pointer_array_get_pointer(
1541                                 events, i);
1542                 struct lttng_event *event =
1543                         (struct lttng_event *) (local_flattened_events.data +
1544                                                 (sizeof(struct lttng_event) * i));
1545                 struct lttng_event_extended *event_extended =
1546                         (struct lttng_event_extended *) (local_flattened_events.data +
1547                                                          local_flattened_events.size);
1548                 const struct lttng_userspace_probe_location *location = nullptr;
1549
1550                 assert(element);
1551
1552                 /* Insert struct lttng_event_extended. */
1553                 ret = lttng_dynamic_buffer_set_size(&local_flattened_events,
1554                                                     local_flattened_events.size +
1555                                                             sizeof(*event_extended));
1556                 if (ret) {
1557                         ret_code = LTTNG_ERR_NOMEM;
1558                         goto end;
1559                 }
1560                 event->extended.ptr = event_extended;
1561
1562                 /* Insert filter expression. */
1563                 if (element->filter_expression) {
1564                         const size_t len = strlen(element->filter_expression) + 1;
1565
1566                         event_extended->filter_expression =
1567                                 local_flattened_events.data + local_flattened_events.size;
1568                         ret = lttng_dynamic_buffer_append(
1569                                 &local_flattened_events, element->filter_expression, len);
1570                         if (ret) {
1571                                 ret_code = LTTNG_ERR_NOMEM;
1572                                 goto end;
1573                         }
1574                 }
1575
1576                 /* Insert exclusions. */
1577                 if (element->exclusions) {
1578                         event_extended->exclusions.count = element->exclusions->count;
1579                         event_extended->exclusions.strings =
1580                                 local_flattened_events.data + local_flattened_events.size;
1581
1582                         ret = lttng_dynamic_buffer_append(&local_flattened_events,
1583                                                           element->exclusions->names,
1584                                                           element->exclusions->count *
1585                                                                   LTTNG_SYMBOL_NAME_LEN);
1586                         if (ret) {
1587                                 ret_code = LTTNG_ERR_NOMEM;
1588                                 goto end;
1589                         }
1590                 }
1591
1592                 /* Insert padding to align to 64-bits. */
1593                 ret = lttng_dynamic_buffer_set_size(&local_flattened_events,
1594                                                     lttng_align_ceil(local_flattened_events.size,
1595                                                                      sizeof(uint64_t)));
1596                 if (ret) {
1597                         ret_code = LTTNG_ERR_NOMEM;
1598                         goto end;
1599                 }
1600
1601                 location = lttng_event_get_userspace_probe_location(element->event);
1602                 if (location) {
1603                         event_extended->probe_location = (struct lttng_userspace_probe_location
1604                                                                   *) (local_flattened_events.data +
1605                                                                       local_flattened_events.size);
1606                         ret = lttng_userspace_probe_location_flatten(location,
1607                                                                      &local_flattened_events);
1608                         if (ret < 0) {
1609                                 ret_code = LTTNG_ERR_PROBE_LOCATION_INVAL;
1610                                 goto end;
1611                         }
1612                 }
1613         }
1614
1615         /* Don't reset local_flattened_events buffer as we return its content. */
1616         *flattened_events = (struct lttng_event *) local_flattened_events.data;
1617         lttng_dynamic_buffer_init(&local_flattened_events);
1618         ret_code = LTTNG_OK;
1619 end:
1620         lttng_dynamic_buffer_reset(&local_flattened_events);
1621         return ret_code;
1622 }
1623
1624 static enum lttng_error_code
1625 event_list_create_from_payload(struct lttng_payload_view *view,
1626                                unsigned int count,
1627                                struct lttng_dynamic_pointer_array *event_list)
1628 {
1629         enum lttng_error_code ret_code;
1630         int ret;
1631         unsigned int i;
1632         int offset = 0;
1633
1634         assert(view);
1635         assert(event_list);
1636
1637         for (i = 0; i < count; i++) {
1638                 ssize_t event_size;
1639                 struct lttng_payload_view event_view =
1640                         lttng_payload_view_from_view(view, offset, -1);
1641                 struct event_list_element *element = zmalloc<event_list_element>();
1642
1643                 if (!element) {
1644                         ret_code = LTTNG_ERR_NOMEM;
1645                         goto end;
1646                 }
1647
1648                 /*
1649                  * Lifetime and management of the object is now bound to the
1650                  * array.
1651                  */
1652                 ret = lttng_dynamic_pointer_array_add_pointer(event_list, element);
1653                 if (ret) {
1654                         event_list_destructor(element);
1655                         ret_code = LTTNG_ERR_NOMEM;
1656                         goto end;
1657                 }
1658
1659                 /*
1660                  * Bytecode is not transmitted on listing in any case we do not
1661                  * care about it.
1662                  */
1663                 event_size = lttng_event_create_from_payload(&event_view,
1664                                                              &element->event,
1665                                                              &element->exclusions,
1666                                                              &element->filter_expression,
1667                                                              nullptr);
1668                 if (event_size < 0) {
1669                         ret_code = LTTNG_ERR_INVALID;
1670                         goto end;
1671                 }
1672
1673                 offset += event_size;
1674         }
1675
1676         if (view->buffer.size != offset) {
1677                 ret_code = LTTNG_ERR_INVALID_PROTOCOL;
1678                 goto end;
1679         }
1680
1681         ret_code = LTTNG_OK;
1682
1683 end:
1684         return ret_code;
1685 }
1686
1687 enum lttng_error_code lttng_events_create_and_flatten_from_payload(
1688         struct lttng_payload_view *payload, unsigned int count, struct lttng_event **events)
1689 {
1690         enum lttng_error_code ret = LTTNG_OK;
1691         struct lttng_dynamic_pointer_array local_events;
1692
1693         lttng_dynamic_pointer_array_init(&local_events, event_list_destructor);
1694
1695         /* Deserialize the events. */
1696         {
1697                 struct lttng_payload_view events_view =
1698                         lttng_payload_view_from_view(payload, 0, -1);
1699
1700                 ret = event_list_create_from_payload(&events_view, count, &local_events);
1701                 if (ret != LTTNG_OK) {
1702                         goto end;
1703                 }
1704         }
1705
1706         ret = flatten_lttng_events(&local_events, events);
1707         if (ret != LTTNG_OK) {
1708                 goto end;
1709         }
1710
1711 end:
1712         lttng_dynamic_pointer_array_reset(&local_events);
1713         return ret;
1714 }
1715
1716 static enum lttng_error_code
1717 flatten_lttng_event_fields(struct lttng_dynamic_pointer_array *event_fields,
1718                            struct lttng_event_field **flattened_event_fields)
1719 {
1720         int ret, i;
1721         enum lttng_error_code ret_code;
1722         size_t storage_req = 0;
1723         struct lttng_dynamic_buffer local_flattened_event_fields;
1724         int nb_event_field;
1725
1726         assert(event_fields);
1727         assert(flattened_event_fields);
1728
1729         lttng_dynamic_buffer_init(&local_flattened_event_fields);
1730         nb_event_field = lttng_dynamic_pointer_array_get_count(event_fields);
1731
1732         /*
1733          * Here even if the event field contains a `struct lttng_event` that
1734          * could contain dynamic data, in reality it is not the case.
1735          * Dynamic data is not present. Here the flattening is mostly a direct
1736          * memcpy. This is less than ideal but this code is still better than
1737          * direct usage of an unpacked lttng_event_field array.
1738          */
1739         storage_req += sizeof(struct lttng_event_field) * nb_event_field;
1740
1741         lttng_dynamic_buffer_init(&local_flattened_event_fields);
1742
1743         /*
1744          * We must ensure that "local_flattened_event_fields" is never resized
1745          * so as to preserve the validity of the flattened objects.
1746          */
1747         ret = lttng_dynamic_buffer_set_capacity(&local_flattened_event_fields, storage_req);
1748         if (ret) {
1749                 ret_code = LTTNG_ERR_NOMEM;
1750                 goto end;
1751         }
1752
1753         for (i = 0; i < nb_event_field; i++) {
1754                 const struct lttng_event_field *element =
1755                         (const struct lttng_event_field *) lttng_dynamic_pointer_array_get_pointer(
1756                                 event_fields, i);
1757
1758                 if (!element) {
1759                         ret_code = LTTNG_ERR_FATAL;
1760                         goto end;
1761                 }
1762                 ret = lttng_dynamic_buffer_append(
1763                         &local_flattened_event_fields, element, sizeof(struct lttng_event_field));
1764                 if (ret) {
1765                         ret_code = LTTNG_ERR_NOMEM;
1766                         goto end;
1767                 }
1768         }
1769
1770         /* Don't reset local_flattened_channels buffer as we return its content. */
1771         *flattened_event_fields = (struct lttng_event_field *) local_flattened_event_fields.data;
1772         lttng_dynamic_buffer_init(&local_flattened_event_fields);
1773         ret_code = LTTNG_OK;
1774 end:
1775         lttng_dynamic_buffer_reset(&local_flattened_event_fields);
1776         return ret_code;
1777 }
1778
1779 static enum lttng_error_code
1780 event_field_list_create_from_payload(struct lttng_payload_view *view,
1781                                      unsigned int count,
1782                                      struct lttng_dynamic_pointer_array **event_field_list)
1783 {
1784         enum lttng_error_code ret_code;
1785         int ret, offset = 0;
1786         unsigned int i;
1787         struct lttng_dynamic_pointer_array *list = nullptr;
1788
1789         assert(view);
1790         assert(event_field_list);
1791
1792         list = zmalloc<lttng_dynamic_pointer_array>();
1793         if (!list) {
1794                 ret_code = LTTNG_ERR_NOMEM;
1795                 goto end;
1796         }
1797
1798         lttng_dynamic_pointer_array_init(list, free);
1799
1800         for (i = 0; i < count; i++) {
1801                 ssize_t event_field_size;
1802                 struct lttng_event_field *field = nullptr;
1803                 struct lttng_payload_view event_field_view =
1804                         lttng_payload_view_from_view(view, offset, -1);
1805
1806                 event_field_size = lttng_event_field_create_from_payload(&event_field_view, &field);
1807                 if (event_field_size < 0) {
1808                         ret_code = LTTNG_ERR_INVALID;
1809                         goto end;
1810                 }
1811
1812                 /* Lifetime and management of the object is now bound to the array. */
1813                 ret = lttng_dynamic_pointer_array_add_pointer(list, field);
1814                 if (ret) {
1815                         free(field);
1816                         ret_code = LTTNG_ERR_NOMEM;
1817                         goto end;
1818                 }
1819
1820                 offset += event_field_size;
1821         }
1822
1823         if (view->buffer.size != offset) {
1824                 ret_code = LTTNG_ERR_INVALID;
1825                 goto end;
1826         }
1827
1828         *event_field_list = list;
1829         list = nullptr;
1830         ret_code = LTTNG_OK;
1831
1832 end:
1833         if (list) {
1834                 lttng_dynamic_pointer_array_reset(list);
1835                 free(list);
1836         }
1837
1838         return ret_code;
1839 }
1840
1841 enum lttng_error_code lttng_event_fields_create_and_flatten_from_payload(
1842         struct lttng_payload_view *view, unsigned int count, struct lttng_event_field **fields)
1843 {
1844         enum lttng_error_code ret_code;
1845         struct lttng_dynamic_pointer_array *local_event_fields = nullptr;
1846
1847         ret_code = event_field_list_create_from_payload(view, count, &local_event_fields);
1848         if (ret_code != LTTNG_OK) {
1849                 goto end;
1850         }
1851
1852         ret_code = flatten_lttng_event_fields(local_event_fields, fields);
1853         if (ret_code != LTTNG_OK) {
1854                 goto end;
1855         }
1856 end:
1857         if (local_event_fields) {
1858                 lttng_dynamic_pointer_array_reset(local_event_fields);
1859                 free(local_event_fields);
1860         }
1861
1862         return ret_code;
1863 }