src/common/event-rule/kernel-syscall.c

   1 /*
   2  * Copyright (C) 2019 Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #include <assert.h>
   9 #include <common/credentials.h>
  10 #include <common/error.h>
  11 #include <common/hashtable/hashtable.h>
  12 #include <common/hashtable/utils.h>
  13 #include <common/macros.h>
  14 #include <common/mi-lttng.h>
  15 #include <common/payload-view.h>
  16 #include <common/payload.h>
  17 #include <common/runas.h>
  18 #include <common/string-utils/string-utils.h>
  19 #include <lttng/event-rule/event-rule-internal.h>
  20 #include <lttng/event-rule/kernel-syscall-internal.h>
  21
  22 #define IS_SYSCALL_EVENT_RULE(rule) \
  23         (lttng_event_rule_get_type(rule) == LTTNG_EVENT_RULE_TYPE_KERNEL_SYSCALL)
  24
  25 static void lttng_event_rule_kernel_syscall_destroy(struct lttng_event_rule *rule)
  26 {
  27         struct lttng_event_rule_kernel_syscall *syscall;
  28
  29         if (rule == NULL) {
  30                 return;
  31         }
  32
  33         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
  34
  35         free(syscall->pattern);
  36         free(syscall->filter_expression);
  37         free(syscall->internal_filter.filter);
  38         free(syscall->internal_filter.bytecode);
  39         free(syscall);
  40 }
  41
  42 static bool lttng_event_rule_kernel_syscall_validate(
  43                 const struct lttng_event_rule *rule)
  44 {
  45         bool valid = false;
  46         struct lttng_event_rule_kernel_syscall *syscall;
  47
  48         if (!rule) {
  49                 goto end;
  50         }
  51
  52         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
  53
  54         /* Required field. */
  55         if (!syscall->pattern) {
  56                 ERR("Invalid syscall event rule: a pattern must be set.");
  57                 goto end;
  58         }
  59
  60         valid = true;
  61 end:
  62         return valid;
  63 }
  64
  65 static int lttng_event_rule_kernel_syscall_serialize(
  66                 const struct lttng_event_rule *rule,
  67                 struct lttng_payload *payload)
  68 {
  69         int ret;
  70         size_t pattern_len, filter_expression_len;
  71         struct lttng_event_rule_kernel_syscall *syscall;
  72         struct lttng_event_rule_kernel_syscall_comm syscall_comm;
  73
  74         if (!rule || !IS_SYSCALL_EVENT_RULE(rule)) {
  75                 ret = -1;
  76                 goto end;
  77         }
  78
  79         DBG("Serializing syscall event rule");
  80         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
  81
  82         pattern_len = strlen(syscall->pattern) + 1;
  83
  84         if (syscall->filter_expression != NULL) {
  85                 filter_expression_len = strlen(syscall->filter_expression) + 1;
  86         } else {
  87                 filter_expression_len = 0;
  88         }
  89
  90         syscall_comm.pattern_len = pattern_len;
  91         syscall_comm.filter_expression_len = filter_expression_len;
  92         syscall_comm.emission_site = syscall->emission_site;
  93
  94         ret = lttng_dynamic_buffer_append(
  95                         &payload->buffer, &syscall_comm, sizeof(syscall_comm));
  96         if (ret) {
  97                 goto end;
  98         }
  99
 100         ret = lttng_dynamic_buffer_append(
 101                         &payload->buffer, syscall->pattern, pattern_len);
 102         if (ret) {
 103                 goto end;
 104         }
 105
 106         ret = lttng_dynamic_buffer_append(&payload->buffer,
 107                         syscall->filter_expression, filter_expression_len);
 108 end:
 109         return ret;
 110 }
 111
 112 static bool lttng_event_rule_kernel_syscall_is_equal(const struct lttng_event_rule *_a,
 113                 const struct lttng_event_rule *_b)
 114 {
 115         bool is_equal = false;
 116         struct lttng_event_rule_kernel_syscall *a, *b;
 117
 118         a = container_of(_a, struct lttng_event_rule_kernel_syscall, parent);
 119         b = container_of(_b, struct lttng_event_rule_kernel_syscall, parent);
 120
 121         if (!!a->filter_expression != !!b->filter_expression) {
 122                 goto end;
 123         }
 124
 125         assert(a->pattern);
 126         assert(b->pattern);
 127         if (strcmp(a->pattern, b->pattern)) {
 128                 goto end;
 129         }
 130
 131         if (a->filter_expression && b->filter_expression) {
 132                 if (strcmp(a->filter_expression, b->filter_expression)) {
 133                         goto end;
 134                 }
 135         } else if (!!a->filter_expression != !!b->filter_expression) {
 136                 /* One is set and not the other. */
 137                 goto end;
 138         }
 139
 140         is_equal = true;
 141 end:
 142         return is_equal;
 143 }
 144
 145 static enum lttng_error_code lttng_event_rule_kernel_syscall_generate_filter_bytecode(
 146                 struct lttng_event_rule *rule,
 147                 const struct lttng_credentials *creds)
 148 {
 149         int ret;
 150         enum lttng_error_code ret_code = LTTNG_OK;
 151         struct lttng_event_rule_kernel_syscall *syscall;
 152         enum lttng_event_rule_status status;
 153         const char *filter;
 154         struct lttng_bytecode *bytecode = NULL;
 155
 156         assert(rule);
 157
 158         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 159
 160         /* Generate the filter bytecode. */
 161         status = lttng_event_rule_kernel_syscall_get_filter(rule, &filter);
 162         if (status == LTTNG_EVENT_RULE_STATUS_UNSET) {
 163                 filter = NULL;
 164         } else if (status != LTTNG_EVENT_RULE_STATUS_OK) {
 165                 ret_code = LTTNG_ERR_FILTER_INVAL;
 166                 goto end;
 167         }
 168
 169         if (filter && filter[0] == '\0') {
 170                 ret_code = LTTNG_ERR_FILTER_INVAL;
 171                 goto end;
 172         }
 173
 174         if (filter == NULL) {
 175                 /* Nothing to do. */
 176                 ret = LTTNG_OK;
 177                 goto end;
 178         }
 179
 180         syscall->internal_filter.filter = strdup(filter);
 181         if (syscall->internal_filter.filter == NULL) {
 182                 ret_code = LTTNG_ERR_NOMEM;
 183                 goto end;
 184         }
 185
 186         ret = run_as_generate_filter_bytecode(
 187                         syscall->internal_filter.filter, creds, &bytecode);
 188         if (ret) {
 189                 ret_code = LTTNG_ERR_FILTER_INVAL;
 190         }
 191
 192         syscall->internal_filter.bytecode = bytecode;
 193         bytecode = NULL;
 194
 195 end:
 196         free(bytecode);
 197         return ret_code;
 198 }
 199
 200 static const char *lttng_event_rule_kernel_syscall_get_internal_filter(
 201                 const struct lttng_event_rule *rule)
 202 {
 203         struct lttng_event_rule_kernel_syscall *syscall;
 204
 205         assert(rule);
 206         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 207
 208         return syscall->internal_filter.filter;
 209 }
 210
 211 static const struct lttng_bytecode *
 212 lttng_event_rule_kernel_syscall_get_internal_filter_bytecode(
 213                 const struct lttng_event_rule *rule)
 214 {
 215         struct lttng_event_rule_kernel_syscall *syscall;
 216
 217         assert(rule);
 218         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 219
 220         return syscall->internal_filter.bytecode;
 221 }
 222
 223 static enum lttng_event_rule_generate_exclusions_status
 224 lttng_event_rule_kernel_syscall_generate_exclusions(const struct lttng_event_rule *rule,
 225                 struct lttng_event_exclusion **exclusions)
 226 {
 227         /* Unsupported. */
 228         *exclusions = NULL;
 229         return LTTNG_EVENT_RULE_GENERATE_EXCLUSIONS_STATUS_NONE;
 230 }
 231
 232 static unsigned long
 233 lttng_event_rule_kernel_syscall_hash(
 234                 const struct lttng_event_rule *rule)
 235 {
 236         unsigned long hash;
 237         struct lttng_event_rule_kernel_syscall *syscall_rule =
 238                         container_of(rule, typeof(*syscall_rule), parent);
 239
 240         hash = hash_key_ulong((void *) LTTNG_EVENT_RULE_TYPE_KERNEL_SYSCALL,
 241                         lttng_ht_seed);
 242         hash ^= hash_key_str(syscall_rule->pattern, lttng_ht_seed);
 243         if (syscall_rule->filter_expression) {
 244                 hash ^= hash_key_str(syscall_rule->filter_expression,
 245                                 lttng_ht_seed);
 246         }
 247
 248         return hash;
 249 }
 250
 251 static enum lttng_error_code lttng_event_rule_kernel_syscall_mi_serialize(
 252                 const struct lttng_event_rule *rule, struct mi_writer *writer)
 253 {
 254         int ret;
 255         enum lttng_error_code ret_code;
 256         enum lttng_event_rule_status status;
 257
 258         enum lttng_event_rule_kernel_syscall_emission_site site_type;
 259         const char *filter = NULL;
 260         const char *name_pattern = NULL;
 261         const char *site_type_str = NULL;
 262
 263         assert(rule);
 264         assert(writer);
 265         assert(IS_SYSCALL_EVENT_RULE(rule));
 266
 267         status = lttng_event_rule_kernel_syscall_get_name_pattern(
 268                         rule, &name_pattern);
 269         assert(status == LTTNG_EVENT_RULE_STATUS_OK);
 270         assert(name_pattern);
 271
 272         status = lttng_event_rule_kernel_syscall_get_filter(rule, &filter);
 273         assert(status == LTTNG_EVENT_RULE_STATUS_OK ||
 274                         status == LTTNG_EVENT_RULE_STATUS_UNSET);
 275
 276         site_type = lttng_event_rule_kernel_syscall_get_emission_site(rule);
 277
 278         switch (site_type) {
 279         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_ENTRY_EXIT:
 280                 site_type_str = mi_lttng_event_rule_kernel_syscall_emission_site_entry_exit;
 281                 break;
 282         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_ENTRY:
 283                 site_type_str = mi_lttng_event_rule_kernel_syscall_emission_site_entry;
 284                 break;
 285         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_EXIT:
 286                 site_type_str = mi_lttng_event_rule_kernel_syscall_emission_site_exit;
 287                 break;
 288         default:
 289                 abort();
 290                 break;
 291         }
 292
 293         /* Open event rule kernel syscall element. */
 294         ret = mi_lttng_writer_open_element(
 295                         writer, mi_lttng_element_event_rule_kernel_syscall);
 296         if (ret) {
 297                 goto mi_error;
 298         }
 299
 300         /* Emission site. */
 301         ret = mi_lttng_writer_write_element_string(writer,
 302                         mi_lttng_element_event_rule_kernel_syscall_emission_site,
 303                         site_type_str);
 304         if (ret) {
 305                 goto mi_error;
 306         }
 307
 308         /* Name pattern. */
 309         ret = mi_lttng_writer_write_element_string(writer,
 310                         mi_lttng_element_event_rule_name_pattern, name_pattern);
 311         if (ret) {
 312                 goto mi_error;
 313         }
 314
 315         /* Filter. */
 316         if (filter != NULL) {
 317                 ret = mi_lttng_writer_write_element_string(writer,
 318                                 mi_lttng_element_event_rule_filter_expression,
 319                                 filter);
 320                 if (ret) {
 321                         goto mi_error;
 322                 }
 323         }
 324
 325         /* Close event rule kernel syscall. */
 326         ret = mi_lttng_writer_close_element(writer);
 327         if (ret) {
 328                 goto mi_error;
 329         }
 330
 331         ret_code = LTTNG_OK;
 332         goto end;
 333
 334 mi_error:
 335         ret_code = LTTNG_ERR_MI_IO_FAIL;
 336 end:
 337         return ret_code;
 338 }
 339
 340 struct lttng_event_rule *lttng_event_rule_kernel_syscall_create(
 341                 enum lttng_event_rule_kernel_syscall_emission_site
 342                                 emission_site)
 343 {
 344         struct lttng_event_rule *rule = NULL;
 345         struct lttng_event_rule_kernel_syscall *syscall_rule;
 346         enum lttng_event_rule_status status;
 347
 348         /* Validate the emission site type */
 349         switch (emission_site) {
 350         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_ENTRY_EXIT:
 351         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_ENTRY:
 352         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_EXIT:
 353                 break;
 354         default:
 355                 /* Invalid emission type */
 356                 goto end;
 357         }
 358
 359         syscall_rule = zmalloc(sizeof(struct lttng_event_rule_kernel_syscall));
 360         if (!syscall_rule) {
 361                 goto end;
 362         }
 363
 364         rule = &syscall_rule->parent;
 365         lttng_event_rule_init(
 366                         &syscall_rule->parent, LTTNG_EVENT_RULE_TYPE_KERNEL_SYSCALL);
 367         syscall_rule->parent.validate = lttng_event_rule_kernel_syscall_validate;
 368         syscall_rule->parent.serialize = lttng_event_rule_kernel_syscall_serialize;
 369         syscall_rule->parent.equal = lttng_event_rule_kernel_syscall_is_equal;
 370         syscall_rule->parent.destroy = lttng_event_rule_kernel_syscall_destroy;
 371         syscall_rule->parent.generate_filter_bytecode =
 372                         lttng_event_rule_kernel_syscall_generate_filter_bytecode;
 373         syscall_rule->parent.get_filter =
 374                         lttng_event_rule_kernel_syscall_get_internal_filter;
 375         syscall_rule->parent.get_filter_bytecode =
 376                         lttng_event_rule_kernel_syscall_get_internal_filter_bytecode;
 377         syscall_rule->parent.generate_exclusions =
 378                         lttng_event_rule_kernel_syscall_generate_exclusions;
 379         syscall_rule->parent.hash = lttng_event_rule_kernel_syscall_hash;
 380         syscall_rule->parent.mi_serialize = lttng_event_rule_kernel_syscall_mi_serialize;
 381
 382         /* Default pattern is '*'. */
 383         status = lttng_event_rule_kernel_syscall_set_name_pattern(rule, "*");
 384         if (status != LTTNG_EVENT_RULE_STATUS_OK) {
 385                 lttng_event_rule_destroy(rule);
 386                 rule = NULL;
 387         }
 388
 389         /* Emission site type */
 390         syscall_rule->emission_site = emission_site;
 391
 392 end:
 393         return rule;
 394 }
 395
 396 LTTNG_HIDDEN
 397 ssize_t lttng_event_rule_kernel_syscall_create_from_payload(
 398                 struct lttng_payload_view *view,
 399                 struct lttng_event_rule **_event_rule)
 400 {
 401         ssize_t ret, offset = 0;
 402         enum lttng_event_rule_status status;
 403         const struct lttng_event_rule_kernel_syscall_comm *syscall_comm;
 404         const char *pattern;
 405         const char *filter_expression = NULL;
 406         struct lttng_buffer_view current_buffer_view;
 407         struct lttng_event_rule *rule = NULL;
 408
 409         if (!_event_rule) {
 410                 ret = -1;
 411                 goto end;
 412         }
 413
 414         if (view->buffer.size < sizeof(*syscall_comm)) {
 415                 ERR("Failed to initialize from malformed event rule syscall: buffer too short to contain header");
 416                 ret = -1;
 417                 goto end;
 418         }
 419
 420         current_buffer_view = lttng_buffer_view_from_view(
 421                         &view->buffer, offset, sizeof(*syscall_comm));
 422         if (!lttng_buffer_view_is_valid(&current_buffer_view)) {
 423                 ret = -1;
 424                 goto end;
 425         }
 426
 427         syscall_comm = (typeof(syscall_comm)) current_buffer_view.data;
 428         rule = lttng_event_rule_kernel_syscall_create(syscall_comm->emission_site);
 429         if (!rule) {
 430                 ERR("Failed to create event rule syscall");
 431                 ret = -1;
 432                 goto end;
 433         }
 434
 435         /* Skip to payload. */
 436         offset += current_buffer_view.size;
 437
 438         /* Map the pattern. */
 439         current_buffer_view = lttng_buffer_view_from_view(
 440                         &view->buffer, offset, syscall_comm->pattern_len);
 441         if (!lttng_buffer_view_is_valid(&current_buffer_view)) {
 442                 ret = -1;
 443                 goto end;
 444         }
 445
 446         pattern = current_buffer_view.data;
 447         if (!lttng_buffer_view_contains_string(&current_buffer_view, pattern,
 448                         syscall_comm->pattern_len)) {
 449                 ret = -1;
 450                 goto end;
 451         }
 452
 453         /* Skip after the pattern. */
 454         offset += syscall_comm->pattern_len;
 455
 456         if (!syscall_comm->filter_expression_len) {
 457                 goto skip_filter_expression;
 458         }
 459
 460         /* Map the filter_expression. */
 461         current_buffer_view = lttng_buffer_view_from_view(&view->buffer, offset,
 462                         syscall_comm->filter_expression_len);
 463         if (!lttng_buffer_view_is_valid(&current_buffer_view)) {
 464                 ret = -1;
 465                 goto end;
 466         }
 467
 468         filter_expression = current_buffer_view.data;
 469         if (!lttng_buffer_view_contains_string(&current_buffer_view,
 470                                 filter_expression,
 471                                 syscall_comm->filter_expression_len)) {
 472                 ret = -1;
 473                 goto end;
 474         }
 475
 476         /* Skip after the pattern. */
 477         offset += syscall_comm->filter_expression_len;
 478
 479 skip_filter_expression:
 480
 481         status = lttng_event_rule_kernel_syscall_set_name_pattern(rule, pattern);
 482         if (status != LTTNG_EVENT_RULE_STATUS_OK) {
 483                 ERR("Failed to set event rule syscall pattern");
 484                 ret = -1;
 485                 goto end;
 486         }
 487
 488         if (filter_expression) {
 489                 status = lttng_event_rule_kernel_syscall_set_filter(
 490                                 rule, filter_expression);
 491                 if (status != LTTNG_EVENT_RULE_STATUS_OK) {
 492                         ERR("Failed to set event rule syscall pattern");
 493                         ret = -1;
 494                         goto end;
 495                 }
 496         }
 497
 498         *_event_rule = rule;
 499         rule = NULL;
 500         ret = offset;
 501 end:
 502         lttng_event_rule_destroy(rule);
 503         return ret;
 504 }
 505
 506 enum lttng_event_rule_status lttng_event_rule_kernel_syscall_set_name_pattern(
 507                 struct lttng_event_rule *rule, const char *pattern)
 508 {
 509         char *pattern_copy = NULL;
 510         struct lttng_event_rule_kernel_syscall *syscall;
 511         enum lttng_event_rule_status status = LTTNG_EVENT_RULE_STATUS_OK;
 512
 513         if (!rule || !IS_SYSCALL_EVENT_RULE(rule) || !pattern ||
 514                         strlen(pattern) == 0) {
 515                 status = LTTNG_EVENT_RULE_STATUS_INVALID;
 516                 goto end;
 517         }
 518
 519         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 520         pattern_copy = strdup(pattern);
 521         if (!pattern_copy) {
 522                 status = LTTNG_EVENT_RULE_STATUS_ERROR;
 523                 goto end;
 524         }
 525
 526         strutils_normalize_star_glob_pattern(pattern_copy);
 527
 528         free(syscall->pattern);
 529
 530         syscall->pattern = pattern_copy;
 531         pattern_copy = NULL;
 532 end:
 533         return status;
 534 }
 535
 536 enum lttng_event_rule_status lttng_event_rule_kernel_syscall_get_name_pattern(
 537                 const struct lttng_event_rule *rule, const char **pattern)
 538 {
 539         struct lttng_event_rule_kernel_syscall *syscall;
 540         enum lttng_event_rule_status status = LTTNG_EVENT_RULE_STATUS_OK;
 541
 542         if (!rule || !IS_SYSCALL_EVENT_RULE(rule) || !pattern) {
 543                 status = LTTNG_EVENT_RULE_STATUS_INVALID;
 544                 goto end;
 545         }
 546
 547         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 548         if (!syscall->pattern) {
 549                 status = LTTNG_EVENT_RULE_STATUS_UNSET;
 550                 goto end;
 551         }
 552
 553         *pattern = syscall->pattern;
 554 end:
 555         return status;
 556 }
 557
 558 enum lttng_event_rule_status lttng_event_rule_kernel_syscall_set_filter(
 559                 struct lttng_event_rule *rule, const char *expression)
 560 {
 561         char *expression_copy = NULL;
 562         struct lttng_event_rule_kernel_syscall *syscall;
 563         enum lttng_event_rule_status status = LTTNG_EVENT_RULE_STATUS_OK;
 564
 565         /* TODO: validate that the passed expression is valid. */
 566
 567         if (!rule || !IS_SYSCALL_EVENT_RULE(rule) || !expression ||
 568                         strlen(expression) == 0) {
 569                 status = LTTNG_EVENT_RULE_STATUS_INVALID;
 570                 goto end;
 571         }
 572
 573         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 574         expression_copy = strdup(expression);
 575         if (!expression_copy) {
 576                 status = LTTNG_EVENT_RULE_STATUS_ERROR;
 577                 goto end;
 578         }
 579
 580         if (syscall->filter_expression) {
 581                 free(syscall->filter_expression);
 582         }
 583
 584         syscall->filter_expression = expression_copy;
 585         expression_copy = NULL;
 586 end:
 587         return status;
 588 }
 589
 590 enum lttng_event_rule_status lttng_event_rule_kernel_syscall_get_filter(
 591                 const struct lttng_event_rule *rule, const char **expression)
 592 {
 593         struct lttng_event_rule_kernel_syscall *syscall;
 594         enum lttng_event_rule_status status = LTTNG_EVENT_RULE_STATUS_OK;
 595
 596         if (!rule || !IS_SYSCALL_EVENT_RULE(rule) || !expression) {
 597                 status = LTTNG_EVENT_RULE_STATUS_INVALID;
 598                 goto end;
 599         }
 600
 601         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 602         if (!syscall->filter_expression) {
 603                 status = LTTNG_EVENT_RULE_STATUS_UNSET;
 604                 goto end;
 605         }
 606
 607         *expression = syscall->filter_expression;
 608 end:
 609         return status;
 610 }
 611 extern enum lttng_event_rule_kernel_syscall_emission_site
 612 lttng_event_rule_kernel_syscall_get_emission_site(
 613                 const struct lttng_event_rule *rule)
 614 {
 615         enum lttng_event_rule_kernel_syscall_emission_site emission_site =
 616                 LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_UNKNOWN;
 617         struct lttng_event_rule_kernel_syscall *syscall;
 618
 619         if (!rule || !IS_SYSCALL_EVENT_RULE(rule)) {
 620                 goto end;
 621         }
 622
 623         syscall = container_of(rule, struct lttng_event_rule_kernel_syscall, parent);
 624         emission_site = syscall->emission_site;
 625
 626 end:
 627         return emission_site;
 628 }
 629
 630 LTTNG_HIDDEN
 631 const char *lttng_event_rule_kernel_syscall_emission_site_str(
 632                 enum lttng_event_rule_kernel_syscall_emission_site emission_site)
 633 {
 634         switch (emission_site) {
 635         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_ENTRY:
 636                 return "entry";
 637         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_ENTRY_EXIT:
 638                 return "entry+exit";
 639         case LTTNG_EVENT_RULE_KERNEL_SYSCALL_EMISSION_SITE_EXIT:
 640                 return "exit";
 641         default:
 642                 return "???";
 643         }
 644 }