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         case LTTNG_UST_CONTEXT_VTID:
 278                 return lttng_add_vtid_to_ctx(ctx);
 279         default:
 280                 return -EINVAL;
 281         }
 282 }
 283
 284 /**
 285  *      lttng_cmd - lttng control through socket commands
 286  *
 287  *      @objd: the object descriptor
 288  *      @cmd: the command
 289  *      @arg: command arg
 290  *
 291  *      This descriptor implements lttng commands:
 292  *      LTTNG_UST_SESSION
 293  *              Returns a LTTng trace session object descriptor
 294  *      LTTNG_UST_TRACER_VERSION
 295  *              Returns the LTTng kernel tracer version
 296  *      LTTNG_UST_TRACEPOINT_LIST
 297  *              Returns a file descriptor listing available tracepoints
 298  *      LTTNG_UST_WAIT_QUIESCENT
 299  *              Returns after all previously running probes have completed
 300  *
 301  * The returned session will be deleted when its file descriptor is closed.
 302  */
 303 static
 304 long lttng_cmd(int objd, unsigned int cmd, unsigned long arg)
 305 {
 306         switch (cmd) {
 307         case LTTNG_UST_SESSION:
 308                 return lttng_abi_create_session();
 309         case LTTNG_UST_TRACER_VERSION:
 310                 return lttng_abi_tracer_version(objd,
 311                                 (struct lttng_ust_tracer_version *) arg);
 312         case LTTNG_UST_TRACEPOINT_LIST:
 313                 return -ENOSYS; //TODO
 314                 //return lttng_abi_tracepoint_list();
 315         case LTTNG_UST_WAIT_QUIESCENT:
 316                 synchronize_trace();
 317                 return 0;
 318         default:
 319                 return -EINVAL;
 320         }
 321 }
 322
 323 static const struct objd_ops lttng_ops = {
 324         .cmd = lttng_cmd,
 325 };
 326
 327 /*
 328  * We tolerate no failure in this function (if one happens, we print a dmesg
 329  * error, but cannot return any error, because the channel information is
 330  * invariant.
 331  */
 332 static
 333 void lttng_metadata_create_events(int channel_objd)
 334 {
 335         struct ltt_channel *channel = objd_private(channel_objd);
 336         static struct lttng_ust_event metadata_params = {
 337                 .instrumentation = LTTNG_UST_TRACEPOINT,
 338                 .name = "lttng_metadata",
 339         };
 340         struct ltt_event *event;
 341         int ret;
 342
 343         /*
 344          * We tolerate no failure path after event creation. It will stay
 345          * invariant for the rest of the session.
 346          */
 347         event = ltt_event_create(channel, &metadata_params, NULL);
 348         if (!event) {
 349                 ret = -EINVAL;
 350                 goto create_error;
 351         }
 352         return;
 353
 354 create_error:
 355         WARN_ON(1);
 356         return;         /* not allowed to return error */
 357 }
 358
 359 int lttng_abi_create_channel(int session_objd,
 360                              struct lttng_ust_channel *chan_param,
 361                              enum channel_type channel_type)
 362 {
 363         struct ltt_session *session = objd_private(session_objd);
 364         const struct objd_ops *ops;
 365         const char *transport_name;
 366         struct ltt_channel *chan;
 367         int chan_objd;
 368         int ret = 0;
 369
 370         chan_objd = objd_alloc(NULL, &lttng_channel_ops);
 371         if (chan_objd < 0) {
 372                 ret = chan_objd;
 373                 goto objd_error;
 374         }
 375         switch (channel_type) {
 376         case PER_CPU_CHANNEL:
 377                 if (chan_param->output == LTTNG_UST_MMAP) {
 378                         transport_name = chan_param->overwrite ?
 379                                 "relay-overwrite-mmap" : "relay-discard-mmap";
 380                 } else {
 381                         return -EINVAL;
 382                 }
 383                 ops = &lttng_channel_ops;
 384                 break;
 385         case METADATA_CHANNEL:
 386                 if (chan_param->output == LTTNG_UST_MMAP)
 387                         transport_name = "relay-metadata-mmap";
 388                 else
 389                         return -EINVAL;
 390                 ops = &lttng_metadata_ops;
 391                 break;
 392         default:
 393                 transport_name = "<unknown>";
 394                 break;
 395         }
 396         /*
 397          * We tolerate no failure path after channel creation. It will stay
 398          * invariant for the rest of the session.
 399          */
 400         chan = ltt_channel_create(session, transport_name, NULL,
 401                                   chan_param->subbuf_size,
 402                                   chan_param->num_subbuf,
 403                                   chan_param->switch_timer_interval,
 404                                   chan_param->read_timer_interval,
 405                                   &chan_param->shm_fd,
 406                                   &chan_param->wait_fd,
 407                                   &chan_param->memory_map_size);
 408         if (!chan) {
 409                 ret = -EINVAL;
 410                 goto chan_error;
 411         }
 412         objd_set_private(chan_objd, chan);
 413         chan->objd = chan_objd;
 414         if (channel_type == METADATA_CHANNEL) {
 415                 session->metadata = chan;
 416                 lttng_metadata_create_events(chan_objd);
 417         }
 418
 419         /* The channel created holds a reference on the session */
 420         objd_ref(session_objd);
 421
 422         return chan_objd;
 423
 424 chan_error:
 425         {
 426                 int err;
 427
 428                 err = objd_unref(chan_objd);
 429                 assert(!err);
 430         }
 431 objd_error:
 432         return ret;
 433 }
 434
 435 /**
 436  *      lttng_session_cmd - lttng session object command
 437  *
 438  *      @obj: the object
 439  *      @cmd: the command
 440  *      @arg: command arg
 441  *
 442  *      This descriptor implements lttng commands:
 443  *      LTTNG_UST_CHANNEL
 444  *              Returns a LTTng channel object descriptor
 445  *      LTTNG_UST_ENABLE
 446  *              Enables tracing for a session (weak enable)
 447  *      LTTNG_UST_DISABLE
 448  *              Disables tracing for a session (strong disable)
 449  *      LTTNG_UST_METADATA
 450  *              Returns a LTTng metadata object descriptor
 451  *
 452  * The returned channel will be deleted when its file descriptor is closed.
 453  */
 454 static
 455 long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg)
 456 {
 457         struct ltt_session *session = objd_private(objd);
 458
 459         switch (cmd) {
 460         case LTTNG_UST_CHANNEL:
 461                 return lttng_abi_create_channel(objd,
 462                                 (struct lttng_ust_channel *) arg,
 463                                 PER_CPU_CHANNEL);
 464         case LTTNG_UST_SESSION_START:
 465         case LTTNG_UST_ENABLE:
 466                 return ltt_session_enable(session);
 467         case LTTNG_UST_SESSION_STOP:
 468         case LTTNG_UST_DISABLE:
 469                 return ltt_session_disable(session);
 470         case LTTNG_UST_METADATA:
 471                 return lttng_abi_create_channel(objd,
 472                                 (struct lttng_ust_channel *) arg,
 473                                 METADATA_CHANNEL);
 474         default:
 475                 return -EINVAL;
 476         }
 477 }
 478
 479 /*
 480  * Called when the last file reference is dropped.
 481  *
 482  * Big fat note: channels and events are invariant for the whole session after
 483  * their creation. So this session destruction also destroys all channel and
 484  * event structures specific to this session (they are not destroyed when their
 485  * individual file is released).
 486  */
 487 static
 488 int lttng_release_session(int objd)
 489 {
 490         struct ltt_session *session = objd_private(objd);
 491
 492         if (session) {
 493                 ltt_session_destroy(session);
 494                 return 0;
 495         } else {
 496                 return -EINVAL;
 497         }
 498 }
 499
 500 static const struct objd_ops lttng_session_ops = {
 501         .release = lttng_release_session,
 502         .cmd = lttng_session_cmd,
 503 };
 504
 505 struct stream_priv_data {
 506         struct lib_ring_buffer *buf;
 507         struct ltt_channel *ltt_chan;
 508 };
 509
 510 static
 511 int lttng_abi_open_stream(int channel_objd, struct lttng_ust_stream *info)
 512 {
 513         struct ltt_channel *channel = objd_private(channel_objd);
 514         struct lib_ring_buffer *buf;
 515         struct stream_priv_data *priv;
 516         int stream_objd, ret;
 517
 518         buf = channel->ops->buffer_read_open(channel->chan, channel->handle,
 519                         &info->shm_fd, &info->wait_fd, &info->memory_map_size);
 520         if (!buf)
 521                 return -ENOENT;
 522
 523         priv = zmalloc(sizeof(*priv));
 524         if (!priv) {
 525                 ret = -ENOMEM;
 526                 goto alloc_error;
 527         }
 528         priv->buf = buf;
 529         priv->ltt_chan = channel;
 530         stream_objd = objd_alloc(priv, &lib_ring_buffer_objd_ops);
 531         if (stream_objd < 0) {
 532                 ret = stream_objd;
 533                 goto objd_error;
 534         }
 535         /* Hold a reference on the channel object descriptor */
 536         objd_ref(channel_objd);
 537         return stream_objd;
 538
 539 objd_error:
 540         free(priv);
 541 alloc_error:
 542         channel->ops->buffer_read_close(buf, channel->handle);
 543         return ret;
 544 }
 545
 546 static
 547 int lttng_abi_create_event(int channel_objd,
 548                            struct lttng_ust_event *event_param)
 549 {
 550         struct ltt_channel *channel = objd_private(channel_objd);
 551         struct ltt_event *event;
 552         int event_objd, ret;
 553
 554         event_param->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 555         event_objd = objd_alloc(NULL, &lttng_event_ops);
 556         if (event_objd < 0) {
 557                 ret = event_objd;
 558                 goto objd_error;
 559         }
 560         /*
 561          * We tolerate no failure path after event creation. It will stay
 562          * invariant for the rest of the session.
 563          */
 564         event = ltt_event_create(channel, event_param, NULL);
 565         if (!event) {
 566                 ret = -EINVAL;
 567                 goto event_error;
 568         }
 569         objd_set_private(event_objd, event);
 570         /* The event holds a reference on the channel */
 571         objd_ref(channel_objd);
 572         return event_objd;
 573
 574 event_error:
 575         {
 576                 int err;
 577
 578                 err = objd_unref(event_objd);
 579                 assert(!err);
 580         }
 581 objd_error:
 582         return ret;
 583 }
 584
 585 /**
 586  *      lttng_channel_cmd - lttng control through object descriptors
 587  *
 588  *      @objd: the object descriptor
 589  *      @cmd: the command
 590  *      @arg: command arg
 591  *
 592  *      This object descriptor implements lttng commands:
 593  *      LTTNG_UST_STREAM
 594  *              Returns an event stream object descriptor or failure.
 595  *              (typically, one event stream records events from one CPU)
 596  *      LTTNG_UST_EVENT
 597  *              Returns an event object descriptor or failure.
 598  *      LTTNG_UST_CONTEXT
 599  *              Prepend a context field to each event in the channel
 600  *      LTTNG_UST_ENABLE
 601  *              Enable recording for events in this channel (weak enable)
 602  *      LTTNG_UST_DISABLE
 603  *              Disable recording for events in this channel (strong disable)
 604  *
 605  * Channel and event file descriptors also hold a reference on the session.
 606  */
 607 static
 608 long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg)
 609 {
 610         struct ltt_channel *channel = objd_private(objd);
 611
 612         switch (cmd) {
 613         case LTTNG_UST_STREAM:
 614         {
 615                 struct lttng_ust_stream *stream;
 616
 617                 stream = (struct lttng_ust_stream *) arg;
 618                 /* stream used as output */
 619                 return lttng_abi_open_stream(objd, stream);
 620         }
 621         case LTTNG_UST_EVENT:
 622                 return lttng_abi_create_event(objd, (struct lttng_ust_event *) arg);
 623         case LTTNG_UST_CONTEXT:
 624                 return lttng_abi_add_context(objd,
 625                                 (struct lttng_ust_context *) arg,
 626                                 &channel->ctx, channel->session);
 627         case LTTNG_UST_ENABLE:
 628                 return ltt_channel_enable(channel);
 629         case LTTNG_UST_DISABLE:
 630                 return ltt_channel_disable(channel);
 631         default:
 632                 return -EINVAL;
 633         }
 634 }
 635
 636 /**
 637  *      lttng_metadata_cmd - lttng control through object descriptors
 638  *
 639  *      @objd: the object descriptor
 640  *      @cmd: the command
 641  *      @arg: command arg
 642  *
 643  *      This object descriptor implements lttng commands:
 644  *      LTTNG_UST_STREAM
 645  *              Returns an event stream file descriptor or failure.
 646  *
 647  * Channel and event file descriptors also hold a reference on the session.
 648  */
 649 static
 650 long lttng_metadata_cmd(int objd, unsigned int cmd, unsigned long arg)
 651 {
 652         switch (cmd) {
 653         case LTTNG_UST_STREAM:
 654         {
 655                 struct lttng_ust_stream *stream;
 656
 657                 stream = (struct lttng_ust_stream *) arg;
 658                 /* stream used as output */
 659                 return lttng_abi_open_stream(objd, stream);
 660         }
 661         default:
 662                 return -EINVAL;
 663         }
 664 }
 665
 666 #if 0
 667 /**
 668  *      lttng_channel_poll - lttng stream addition/removal monitoring
 669  *
 670  *      @file: the file
 671  *      @wait: poll table
 672  */
 673 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 674 {
 675         struct ltt_channel *channel = file->private_data;
 676         unsigned int mask = 0;
 677
 678         if (file->f_mode & FMODE_READ) {
 679                 poll_wait_set_exclusive(wait);
 680                 poll_wait(file, channel->ops->get_hp_wait_queue(channel->chan),
 681                           wait);
 682
 683                 if (channel->ops->is_disabled(channel->chan))
 684                         return POLLERR;
 685                 if (channel->ops->is_finalized(channel->chan))
 686                         return POLLHUP;
 687                 if (channel->ops->buffer_has_read_closed_stream(channel->chan))
 688                         return POLLIN | POLLRDNORM;
 689                 return 0;
 690         }
 691         return mask;
 692
 693 }
 694 #endif //0
 695
 696 static
 697 int lttng_channel_release(int objd)
 698 {
 699         struct ltt_channel *channel = objd_private(objd);
 700
 701         if (channel)
 702                 return objd_unref(channel->session->objd);
 703         return 0;
 704 }
 705
 706 static const struct objd_ops lttng_channel_ops = {
 707         .release = lttng_channel_release,
 708         //.poll = lttng_channel_poll,
 709         .cmd = lttng_channel_cmd,
 710 };
 711
 712 static const struct objd_ops lttng_metadata_ops = {
 713         .release = lttng_channel_release,
 714         .cmd = lttng_metadata_cmd,
 715 };
 716
 717 /**
 718  *      lttng_rb_cmd - lttng ring buffer control through object descriptors
 719  *
 720  *      @objd: the object descriptor
 721  *      @cmd: the command
 722  *      @arg: command arg
 723  *
 724  *      This object descriptor implements lttng commands:
 725  *              (None for now. Access is done directly though shm.)
 726  *              TODO: Add buffer flush.
 727  */
 728 static
 729 long lttng_rb_cmd(int objd, unsigned int cmd, unsigned long arg)
 730 {
 731         //struct stream_priv_data *priv = objd_private(objd);
 732
 733         switch (cmd) {
 734         default:
 735                 return -EINVAL;
 736         }
 737 }
 738
 739 static
 740 int lttng_rb_release(int objd)
 741 {
 742         struct stream_priv_data *priv = objd_private(objd);
 743         struct lib_ring_buffer *buf;
 744         struct ltt_channel *channel;
 745
 746         if (priv) {
 747                 buf = priv->buf;
 748                 channel = priv->ltt_chan;
 749                 free(priv);
 750                 channel->ops->buffer_read_close(buf, channel->handle);
 751
 752                 return objd_unref(channel->objd);
 753         }
 754         return 0;
 755 }
 756
 757 static const struct objd_ops lib_ring_buffer_objd_ops = {
 758         .release = lttng_rb_release,
 759         .cmd = lttng_rb_cmd,
 760 };
 761
 762 /**
 763  *      lttng_event_cmd - lttng control through object descriptors
 764  *
 765  *      @objd: the object descriptor
 766  *      @cmd: the command
 767  *      @arg: command arg
 768  *
 769  *      This object descriptor implements lttng commands:
 770  *      LTTNG_UST_CONTEXT
 771  *              Prepend a context field to each record of this event
 772  *      LTTNG_UST_ENABLE
 773  *              Enable recording for this event (weak enable)
 774  *      LTTNG_UST_DISABLE
 775  *              Disable recording for this event (strong disable)
 776  */
 777 static
 778 long lttng_event_cmd(int objd, unsigned int cmd, unsigned long arg)
 779 {
 780         struct ltt_event *event = objd_private(objd);
 781
 782         switch (cmd) {
 783         case LTTNG_UST_CONTEXT:
 784                 return lttng_abi_add_context(objd,
 785                                 (struct lttng_ust_context *) arg,
 786                                 &event->ctx, event->chan->session);
 787         case LTTNG_UST_ENABLE:
 788                 return ltt_event_enable(event);
 789         case LTTNG_UST_DISABLE:
 790                 return ltt_event_disable(event);
 791         default:
 792                 return -EINVAL;
 793         }
 794 }
 795
 796 static
 797 int lttng_event_release(int objd)
 798 {
 799         struct ltt_event *event = objd_private(objd);
 800
 801         if (event)
 802                 return objd_unref(event->chan->objd);
 803         return 0;
 804 }
 805
 806 /* TODO: filter control ioctl */
 807 static const struct objd_ops lttng_event_ops = {
 808         .release = lttng_event_release,
 809         .cmd = lttng_event_cmd,
 810 };
 811
 812 void lttng_ust_abi_exit(void)
 813 {
 814         objd_table_destroy();
 815 }