libust/lttng-ust-abi.c

   1 /*
   2  * lttng-ust-abi.c
   3  *
   4  * Copyright 2010-2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * LTTng UST ABI
   7  *
   8  * Mimic system calls for:
   9  * - session creation, returns an object descriptor or failure.
  10  *   - channel creation, returns an object descriptor or failure.
  11  *     - Operates on a session object descriptor
  12  *     - Takes all channel options as parameters.
  13  *   - stream get, returns an object descriptor or failure.
  14  *     - Operates on a channel object descriptor.
  15  *   - stream notifier get, returns an object descriptor or failure.
  16  *     - Operates on a channel object descriptor.
  17  *   - event creation, returns an object descriptor or failure.
  18  *     - Operates on a channel object descriptor
  19  *     - Takes an event name as parameter
  20  *     - Takes an instrumentation source as parameter
  21  *       - e.g. tracepoints, dynamic_probes...
  22  *     - Takes instrumentation source specific arguments.
  23  *
  24  * Dual LGPL v2.1/GPL v2 license.
  25  */
  26
  27 #include <ust/lttng-ust-abi.h>
  28 #include <urcu/compiler.h>
  29 #include <urcu/list.h>
  30 #include <ust/lttng-events.h>
  31 #include <ust/usterr-signal-safe.h>
  32 #include "ust/core.h"
  33 #include "ltt-tracer.h"
  34
  35 /*
  36  * Object descriptor table. Should be protected from concurrent access
  37  * by the caller.
  38  */
  39
  40 struct obj {
  41         union {
  42                 struct {
  43                         void *private_data;
  44                         const struct objd_ops *ops;
  45                         int f_count;
  46                 } s;
  47                 int freelist_next;      /* offset freelist. end is -1. */
  48         } u;
  49 };
  50
  51 struct objd_table {
  52         struct obj *array;
  53         unsigned int len, allocated_len;
  54         int freelist_head;              /* offset freelist head. end is -1 */
  55 };
  56
  57 static struct objd_table objd_table = {
  58         .freelist_head = -1,
  59 };
  60
  61 static
  62 int objd_alloc(void *private_data, const struct objd_ops *ops)
  63 {
  64         struct obj *obj;
  65
  66         if (objd_table.freelist_head != -1) {
  67                 obj = &objd_table.array[objd_table.freelist_head];
  68                 objd_table.freelist_head = obj->u.freelist_next;
  69                 goto end;
  70         }
  71
  72         if (objd_table.len >= objd_table.allocated_len) {
  73                 unsigned int new_allocated_len, old_allocated_len;
  74                 struct obj *new_table, *old_table;
  75
  76                 old_allocated_len = objd_table.allocated_len;
  77                 old_table = objd_table.array;
  78                 if (!old_allocated_len)
  79                         new_allocated_len = 1;
  80                 else
  81                         new_allocated_len = old_allocated_len << 1;
  82                 new_table = zmalloc(sizeof(struct obj) * new_allocated_len);
  83                 if (!new_table)
  84                         return -ENOMEM;
  85                 memcpy(new_table, old_table,
  86                        sizeof(struct obj) * old_allocated_len);
  87                 free(old_table);
  88                 objd_table.array = new_table;
  89                 objd_table.allocated_len = new_allocated_len;
  90         }
  91         obj = &objd_table.array[objd_table.len];
  92         objd_table.len++;
  93 end:
  94         obj->u.s.private_data = private_data;
  95         obj->u.s.ops = ops;
  96         obj->u.s.f_count = 2;   /* count == 1 : object is allocated */
  97                                 /* count == 2 : allocated + hold ref */
  98         return obj - objd_table.array;
  99 }
 100
 101 static
 102 struct obj *_objd_get(int id)
 103 {
 104         if (id >= objd_table.len)
 105                 return NULL;
 106         if (!objd_table.array[id].u.s.f_count)
 107                 return NULL;
 108         return &objd_table.array[id];
 109 }
 110
 111 static
 112 void *objd_private(int id)
 113 {
 114         struct obj *obj = _objd_get(id);
 115         assert(obj);
 116         return obj->u.s.private_data;
 117 }
 118
 119 static
 120 void objd_set_private(int id, void *private_data)
 121 {
 122         struct obj *obj = _objd_get(id);
 123         assert(obj);
 124         obj->u.s.private_data = private_data;
 125 }
 126
 127 const struct objd_ops *objd_ops(int id)
 128 {
 129         struct obj *obj = _objd_get(id);
 130
 131         if (!obj)
 132                 return NULL;
 133         return obj->u.s.ops;
 134 }
 135
 136 static
 137 void objd_free(int id)
 138 {
 139         struct obj *obj = _objd_get(id);
 140
 141         assert(obj);
 142         obj->u.freelist_next = objd_table.freelist_head;
 143         objd_table.freelist_head = obj - objd_table.array;
 144         assert(obj->u.s.f_count == 1);
 145         obj->u.s.f_count = 0;   /* deallocated */
 146 }
 147
 148 static
 149 void objd_ref(int id)
 150 {
 151         struct obj *obj = _objd_get(id);
 152         obj->u.s.f_count++;
 153 }
 154
 155 int objd_unref(int id)
 156 {
 157         struct obj *obj = _objd_get(id);
 158
 159         if (!obj)
 160                 return -EINVAL;
 161         if (obj->u.s.f_count == 1) {
 162                 ERR("Reference counting error\n");
 163                 return -EINVAL;
 164         }
 165         if ((--obj->u.s.f_count) == 1) {
 166                 const struct objd_ops *ops = objd_ops(id);
 167
 168                 if (ops->release)
 169                         ops->release(id);
 170                 objd_free(id);
 171         }
 172         return 0;
 173 }
 174
 175 static
 176 void objd_table_destroy(void)
 177 {
 178         int i;
 179
 180         for (i = 0; i < objd_table.allocated_len; i++)
 181                 (void) objd_unref(i);
 182         free(objd_table.array);
 183         objd_table.array = NULL;
 184         objd_table.len = 0;
 185         objd_table.allocated_len = 0;
 186         objd_table.freelist_head = -1;
 187 }
 188
 189 /*
 190  * This is LTTng's own personal way to create an ABI for sessiond.
 191  * We send commands over a socket.
 192  */
 193
 194 static const struct objd_ops lttng_ops;
 195 static const struct objd_ops lttng_session_ops;
 196 static const struct objd_ops lttng_channel_ops;
 197 static const struct objd_ops lttng_metadata_ops;
 198 static const struct objd_ops lttng_event_ops;
 199 static const struct objd_ops lib_ring_buffer_objd_ops;
 200
 201 enum channel_type {
 202         PER_CPU_CHANNEL,
 203         METADATA_CHANNEL,
 204 };
 205
 206 int lttng_abi_create_root_handle(void)
 207 {
 208         int root_handle;
 209
 210         root_handle = objd_alloc(NULL, &lttng_ops);
 211         return root_handle;
 212 }
 213
 214 static
 215 int lttng_abi_create_session(void)
 216 {
 217         struct ltt_session *session;
 218         int session_objd, ret;
 219
 220         session = ltt_session_create();
 221         if (!session)
 222                 return -ENOMEM;
 223         session_objd = objd_alloc(session, &lttng_session_ops);
 224         if (session_objd < 0) {
 225                 ret = session_objd;
 226                 goto objd_error;
 227         }
 228         session->objd = session_objd;
 229         return session_objd;
 230
 231 objd_error:
 232         ltt_session_destroy(session);
 233         return ret;
 234 }
 235
 236 #if 0
 237 static
 238 int lttng_abi_tracepoint_list(void)
 239 {
 240         int list_objd, ret;
 241
 242         /* TODO: Create list private data */
 243         list_objd = objd_alloc(NULL, &lttng_tracepoint_list_ops);
 244         if (list_objd < 0) {
 245                 ret = list_objd;
 246                 goto objd_error;
 247         }
 248
 249         return list_objd;
 250
 251 objd_error:
 252         return ret;
 253 }
 254 #endif //0
 255
 256 static
 257 long lttng_abi_tracer_version(int objd,
 258         struct lttng_ust_tracer_version *v)
 259 {
 260         v->version = LTTNG_UST_VERSION;
 261         v->patchlevel = LTTNG_UST_PATCHLEVEL;
 262         v->sublevel = LTTNG_UST_SUBLEVEL;
 263         return 0;
 264 }
 265
 266 static
 267 long lttng_abi_add_context(int objd,
 268         struct lttng_ust_context *context_param,
 269         struct lttng_ctx **ctx, struct ltt_session *session)
 270 {
 271         if (session->been_active)
 272                 return -EPERM;
 273
 274         switch (context_param->ctx) {
 275         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 276                 return lttng_add_pthread_id_to_ctx(ctx);
 277         default:
 278                 return -EINVAL;
 279         }
 280 }
 281
 282 /**
 283  *      lttng_cmd - lttng control through socket commands
 284  *
 285  *      @objd: the object descriptor
 286  *      @cmd: the command
 287  *      @arg: command arg
 288  *
 289  *      This descriptor implements lttng commands:
 290  *      LTTNG_UST_SESSION
 291  *              Returns a LTTng trace session object descriptor
 292  *      LTTNG_UST_TRACER_VERSION
 293  *              Returns the LTTng kernel tracer version
 294  *      LTTNG_UST_TRACEPOINT_LIST
 295  *              Returns a file descriptor listing available tracepoints
 296  *      LTTNG_UST_WAIT_QUIESCENT
 297  *              Returns after all previously running probes have completed
 298  *
 299  * The returned session will be deleted when its file descriptor is closed.
 300  */
 301 static
 302 long lttng_cmd(int objd, unsigned int cmd, unsigned long arg)
 303 {
 304         switch (cmd) {
 305         case LTTNG_UST_SESSION:
 306                 return lttng_abi_create_session();
 307         case LTTNG_UST_TRACER_VERSION:
 308                 return lttng_abi_tracer_version(objd,
 309                                 (struct lttng_ust_tracer_version *) arg);
 310         case LTTNG_UST_TRACEPOINT_LIST:
 311                 return -ENOSYS; //TODO
 312                 //return lttng_abi_tracepoint_list();
 313         case LTTNG_UST_WAIT_QUIESCENT:
 314                 synchronize_trace();
 315                 return 0;
 316         default:
 317                 return -EINVAL;
 318         }
 319 }
 320
 321 static const struct objd_ops lttng_ops = {
 322         .cmd = lttng_cmd,
 323 };
 324
 325 /*
 326  * We tolerate no failure in this function (if one happens, we print a dmesg
 327  * error, but cannot return any error, because the channel information is
 328  * invariant.
 329  */
 330 static
 331 void lttng_metadata_create_events(int channel_objd)
 332 {
 333         struct ltt_channel *channel = objd_private(channel_objd);
 334         static struct lttng_ust_event metadata_params = {
 335                 .instrumentation = LTTNG_UST_TRACEPOINT,
 336                 .name = "lttng_metadata",
 337         };
 338         struct ltt_event *event;
 339         int ret;
 340
 341         /*
 342          * We tolerate no failure path after event creation. It will stay
 343          * invariant for the rest of the session.
 344          */
 345         event = ltt_event_create(channel, &metadata_params, NULL);
 346         if (!event) {
 347                 ret = -EINVAL;
 348                 goto create_error;
 349         }
 350         return;
 351
 352 create_error:
 353         WARN_ON(1);
 354         return;         /* not allowed to return error */
 355 }
 356
 357 int lttng_abi_create_channel(int session_objd,
 358                              struct lttng_ust_channel *chan_param,
 359                              enum channel_type channel_type)
 360 {
 361         struct ltt_session *session = objd_private(session_objd);
 362         const struct objd_ops *ops;
 363         const char *transport_name;
 364         struct ltt_channel *chan;
 365         int chan_objd;
 366         int ret = 0;
 367
 368         chan_objd = objd_alloc(NULL, &lttng_channel_ops);
 369         if (chan_objd < 0) {
 370                 ret = chan_objd;
 371                 goto objd_error;
 372         }
 373         switch (channel_type) {
 374         case PER_CPU_CHANNEL:
 375                 if (chan_param->output == LTTNG_UST_MMAP) {
 376                         transport_name = chan_param->overwrite ?
 377                                 "relay-overwrite-mmap" : "relay-discard-mmap";
 378                 } else {
 379                         return -EINVAL;
 380                 }
 381                 ops = &lttng_channel_ops;
 382                 break;
 383         case METADATA_CHANNEL:
 384                 if (chan_param->output == LTTNG_UST_MMAP)
 385                         transport_name = "relay-metadata-mmap";
 386                 else
 387                         return -EINVAL;
 388                 ops = &lttng_metadata_ops;
 389                 break;
 390         default:
 391                 transport_name = "<unknown>";
 392                 break;
 393         }
 394         /*
 395          * We tolerate no failure path after channel creation. It will stay
 396          * invariant for the rest of the session.
 397          */
 398         chan = ltt_channel_create(session, transport_name, NULL,
 399                                   chan_param->subbuf_size,
 400                                   chan_param->num_subbuf,
 401                                   chan_param->switch_timer_interval,
 402                                   chan_param->read_timer_interval,
 403                                   &chan_param->shm_fd,
 404                                   &chan_param->wait_fd,
 405                                   &chan_param->memory_map_size);
 406         if (!chan) {
 407                 ret = -EINVAL;
 408                 goto chan_error;
 409         }
 410         objd_set_private(chan_objd, chan);
 411         chan->objd = chan_objd;
 412         if (channel_type == METADATA_CHANNEL) {
 413                 session->metadata = chan;
 414                 lttng_metadata_create_events(chan_objd);
 415         }
 416
 417         /* The channel created holds a reference on the session */
 418         objd_ref(session_objd);
 419
 420         return chan_objd;
 421
 422 chan_error:
 423         {
 424                 int err;
 425
 426                 err = objd_unref(chan_objd);
 427                 assert(!err);
 428         }
 429 objd_error:
 430         return ret;
 431 }
 432
 433 /**
 434  *      lttng_session_cmd - lttng session object command
 435  *
 436  *      @obj: the object
 437  *      @cmd: the command
 438  *      @arg: command arg
 439  *
 440  *      This descriptor implements lttng commands:
 441  *      LTTNG_UST_CHANNEL
 442  *              Returns a LTTng channel object descriptor
 443  *      LTTNG_UST_ENABLE
 444  *              Enables tracing for a session (weak enable)
 445  *      LTTNG_UST_DISABLE
 446  *              Disables tracing for a session (strong disable)
 447  *      LTTNG_UST_METADATA
 448  *              Returns a LTTng metadata object descriptor
 449  *
 450  * The returned channel will be deleted when its file descriptor is closed.
 451  */
 452 static
 453 long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg)
 454 {
 455         struct ltt_session *session = objd_private(objd);
 456
 457         switch (cmd) {
 458         case LTTNG_UST_CHANNEL:
 459                 return lttng_abi_create_channel(objd,
 460                                 (struct lttng_ust_channel *) arg,
 461                                 PER_CPU_CHANNEL);
 462         case LTTNG_UST_SESSION_START:
 463         case LTTNG_UST_ENABLE:
 464                 return ltt_session_enable(session);
 465         case LTTNG_UST_SESSION_STOP:
 466         case LTTNG_UST_DISABLE:
 467                 return ltt_session_disable(session);
 468         case LTTNG_UST_METADATA:
 469                 return lttng_abi_create_channel(objd,
 470                                 (struct lttng_ust_channel *) arg,
 471                                 METADATA_CHANNEL);
 472         default:
 473                 return -EINVAL;
 474         }
 475 }
 476
 477 /*
 478  * Called when the last file reference is dropped.
 479  *
 480  * Big fat note: channels and events are invariant for the whole session after
 481  * their creation. So this session destruction also destroys all channel and
 482  * event structures specific to this session (they are not destroyed when their
 483  * individual file is released).
 484  */
 485 static
 486 int lttng_release_session(int objd)
 487 {
 488         struct ltt_session *session = objd_private(objd);
 489
 490         if (session) {
 491                 ltt_session_destroy(session);
 492                 return 0;
 493         } else {
 494                 return -EINVAL;
 495         }
 496 }
 497
 498 static const struct objd_ops lttng_session_ops = {
 499         .release = lttng_release_session,
 500         .cmd = lttng_session_cmd,
 501 };
 502
 503 struct stream_priv_data {
 504         struct lib_ring_buffer *buf;
 505         struct ltt_channel *ltt_chan;
 506 };
 507
 508 static
 509 int lttng_abi_open_stream(int channel_objd, struct lttng_ust_stream *info)
 510 {
 511         struct ltt_channel *channel = objd_private(channel_objd);
 512         struct lib_ring_buffer *buf;
 513         struct stream_priv_data *priv;
 514         int stream_objd, ret;
 515
 516         buf = channel->ops->buffer_read_open(channel->chan, channel->handle,
 517                         &info->shm_fd, &info->wait_fd, &info->memory_map_size);
 518         if (!buf)
 519                 return -ENOENT;
 520
 521         priv = zmalloc(sizeof(*priv));
 522         if (!priv) {
 523                 ret = -ENOMEM;
 524                 goto alloc_error;
 525         }
 526         priv->buf = buf;
 527         priv->ltt_chan = channel;
 528         stream_objd = objd_alloc(priv, &lib_ring_buffer_objd_ops);
 529         if (stream_objd < 0) {
 530                 ret = stream_objd;
 531                 goto objd_error;
 532         }
 533         /* Hold a reference on the channel object descriptor */
 534         objd_ref(channel_objd);
 535         return stream_objd;
 536
 537 objd_error:
 538         free(priv);
 539 alloc_error:
 540         channel->ops->buffer_read_close(buf, channel->handle);
 541         return ret;
 542 }
 543
 544 static
 545 int lttng_abi_create_event(int channel_objd,
 546                            struct lttng_ust_event *event_param)
 547 {
 548         struct ltt_channel *channel = objd_private(channel_objd);
 549         struct ltt_event *event;
 550         int event_objd, ret;
 551
 552         event_param->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 553         event_objd = objd_alloc(NULL, &lttng_event_ops);
 554         if (event_objd < 0) {
 555                 ret = event_objd;
 556                 goto objd_error;
 557         }
 558         /*
 559          * We tolerate no failure path after event creation. It will stay
 560          * invariant for the rest of the session.
 561          */
 562         event = ltt_event_create(channel, event_param, NULL);
 563         if (!event) {
 564                 ret = -EINVAL;
 565                 goto event_error;
 566         }
 567         objd_set_private(event_objd, event);
 568         /* The event holds a reference on the channel */
 569         objd_ref(channel_objd);
 570         return event_objd;
 571
 572 event_error:
 573         {
 574                 int err;
 575
 576                 err = objd_unref(event_objd);
 577                 assert(!err);
 578         }
 579 objd_error:
 580         return ret;
 581 }
 582
 583 /**
 584  *      lttng_channel_cmd - lttng control through object descriptors
 585  *
 586  *      @objd: the object descriptor
 587  *      @cmd: the command
 588  *      @arg: command arg
 589  *
 590  *      This object descriptor implements lttng commands:
 591  *      LTTNG_UST_STREAM
 592  *              Returns an event stream object descriptor or failure.
 593  *              (typically, one event stream records events from one CPU)
 594  *      LTTNG_UST_EVENT
 595  *              Returns an event object descriptor or failure.
 596  *      LTTNG_UST_CONTEXT
 597  *              Prepend a context field to each event in the channel
 598  *      LTTNG_UST_ENABLE
 599  *              Enable recording for events in this channel (weak enable)
 600  *      LTTNG_UST_DISABLE
 601  *              Disable recording for events in this channel (strong disable)
 602  *
 603  * Channel and event file descriptors also hold a reference on the session.
 604  */
 605 static
 606 long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg)
 607 {
 608         struct ltt_channel *channel = objd_private(objd);
 609
 610         switch (cmd) {
 611         case LTTNG_UST_STREAM:
 612         {
 613                 struct lttng_ust_stream *stream;
 614
 615                 stream = (struct lttng_ust_stream *) arg;
 616                 /* stream used as output */
 617                 return lttng_abi_open_stream(objd, stream);
 618         }
 619         case LTTNG_UST_EVENT:
 620                 return lttng_abi_create_event(objd, (struct lttng_ust_event *) arg);
 621         case LTTNG_UST_CONTEXT:
 622                 return lttng_abi_add_context(objd,
 623                                 (struct lttng_ust_context *) arg,
 624                                 &channel->ctx, channel->session);
 625         case LTTNG_UST_ENABLE:
 626                 return ltt_channel_enable(channel);
 627         case LTTNG_UST_DISABLE:
 628                 return ltt_channel_disable(channel);
 629         default:
 630                 return -EINVAL;
 631         }
 632 }
 633
 634 /**
 635  *      lttng_metadata_cmd - lttng control through object descriptors
 636  *
 637  *      @objd: the object descriptor
 638  *      @cmd: the command
 639  *      @arg: command arg
 640  *
 641  *      This object descriptor implements lttng commands:
 642  *      LTTNG_UST_STREAM
 643  *              Returns an event stream file descriptor or failure.
 644  *
 645  * Channel and event file descriptors also hold a reference on the session.
 646  */
 647 static
 648 long lttng_metadata_cmd(int objd, unsigned int cmd, unsigned long arg)
 649 {
 650         switch (cmd) {
 651         case LTTNG_UST_STREAM:
 652         {
 653                 struct lttng_ust_stream *stream;
 654
 655                 stream = (struct lttng_ust_stream *) arg;
 656                 /* stream used as output */
 657                 return lttng_abi_open_stream(objd, stream);
 658         }
 659         default:
 660                 return -EINVAL;
 661         }
 662 }
 663
 664 #if 0
 665 /**
 666  *      lttng_channel_poll - lttng stream addition/removal monitoring
 667  *
 668  *      @file: the file
 669  *      @wait: poll table
 670  */
 671 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 672 {
 673         struct ltt_channel *channel = file->private_data;
 674         unsigned int mask = 0;
 675
 676         if (file->f_mode & FMODE_READ) {
 677                 poll_wait_set_exclusive(wait);
 678                 poll_wait(file, channel->ops->get_hp_wait_queue(channel->chan),
 679                           wait);
 680
 681                 if (channel->ops->is_disabled(channel->chan))
 682                         return POLLERR;
 683                 if (channel->ops->is_finalized(channel->chan))
 684                         return POLLHUP;
 685                 if (channel->ops->buffer_has_read_closed_stream(channel->chan))
 686                         return POLLIN | POLLRDNORM;
 687                 return 0;
 688         }
 689         return mask;
 690
 691 }
 692 #endif //0
 693
 694 static
 695 int lttng_channel_release(int objd)
 696 {
 697         struct ltt_channel *channel = objd_private(objd);
 698
 699         if (channel)
 700                 return objd_unref(channel->session->objd);
 701         return 0;
 702 }
 703
 704 static const struct objd_ops lttng_channel_ops = {
 705         .release = lttng_channel_release,
 706         //.poll = lttng_channel_poll,
 707         .cmd = lttng_channel_cmd,
 708 };
 709
 710 static const struct objd_ops lttng_metadata_ops = {
 711         .release = lttng_channel_release,
 712         .cmd = lttng_metadata_cmd,
 713 };
 714
 715 /**
 716  *      lttng_rb_cmd - lttng ring buffer control through object descriptors
 717  *
 718  *      @objd: the object descriptor
 719  *      @cmd: the command
 720  *      @arg: command arg
 721  *
 722  *      This object descriptor implements lttng commands:
 723  *              (None for now. Access is done directly though shm.)
 724  *              TODO: Add buffer flush.
 725  */
 726 static
 727 long lttng_rb_cmd(int objd, unsigned int cmd, unsigned long arg)
 728 {
 729         //struct stream_priv_data *priv = objd_private(objd);
 730
 731         switch (cmd) {
 732         default:
 733                 return -EINVAL;
 734         }
 735 }
 736
 737 static
 738 int lttng_rb_release(int objd)
 739 {
 740         struct stream_priv_data *priv = objd_private(objd);
 741         struct lib_ring_buffer *buf;
 742         struct ltt_channel *channel;
 743
 744         if (priv) {
 745                 buf = priv->buf;
 746                 channel = priv->ltt_chan;
 747                 free(priv);
 748                 channel->ops->buffer_read_close(buf, channel->handle);
 749
 750                 return objd_unref(channel->objd);
 751         }
 752         return 0;
 753 }
 754
 755 static const struct objd_ops lib_ring_buffer_objd_ops = {
 756         .release = lttng_rb_release,
 757         .cmd = lttng_rb_cmd,
 758 };
 759
 760 /**
 761  *      lttng_event_cmd - lttng control through object descriptors
 762  *
 763  *      @objd: the object descriptor
 764  *      @cmd: the command
 765  *      @arg: command arg
 766  *
 767  *      This object descriptor implements lttng commands:
 768  *      LTTNG_UST_CONTEXT
 769  *              Prepend a context field to each record of this event
 770  *      LTTNG_UST_ENABLE
 771  *              Enable recording for this event (weak enable)
 772  *      LTTNG_UST_DISABLE
 773  *              Disable recording for this event (strong disable)
 774  */
 775 static
 776 long lttng_event_cmd(int objd, unsigned int cmd, unsigned long arg)
 777 {
 778         struct ltt_event *event = objd_private(objd);
 779
 780         switch (cmd) {
 781         case LTTNG_UST_CONTEXT:
 782                 return lttng_abi_add_context(objd,
 783                                 (struct lttng_ust_context *) arg,
 784                                 &event->ctx, event->chan->session);
 785         case LTTNG_UST_ENABLE:
 786                 return ltt_event_enable(event);
 787         case LTTNG_UST_DISABLE:
 788                 return ltt_event_disable(event);
 789         default:
 790                 return -EINVAL;
 791         }
 792 }
 793
 794 static
 795 int lttng_event_release(int objd)
 796 {
 797         struct ltt_event *event = objd_private(objd);
 798
 799         if (event)
 800                 return objd_unref(event->chan->objd);
 801         return 0;
 802 }
 803
 804 /* TODO: filter control ioctl */
 805 static const struct objd_ops lttng_event_ops = {
 806         .release = lttng_event_release,
 807         .cmd = lttng_event_cmd,
 808 };
 809
 810 void lttng_ust_abi_exit(void)
 811 {
 812         objd_table_destroy();
 813 }