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         case LTTNG_UST_CONTEXT_VPID:
 280                 return lttng_add_vpid_to_ctx(ctx);
 281         default:
 282                 return -EINVAL;
 283         }
 284 }
 285
 286 /**
 287  *      lttng_cmd - lttng control through socket commands
 288  *
 289  *      @objd: the object descriptor
 290  *      @cmd: the command
 291  *      @arg: command arg
 292  *
 293  *      This descriptor implements lttng commands:
 294  *      LTTNG_UST_SESSION
 295  *              Returns a LTTng trace session object descriptor
 296  *      LTTNG_UST_TRACER_VERSION
 297  *              Returns the LTTng kernel tracer version
 298  *      LTTNG_UST_TRACEPOINT_LIST
 299  *              Returns a file descriptor listing available tracepoints
 300  *      LTTNG_UST_WAIT_QUIESCENT
 301  *              Returns after all previously running probes have completed
 302  *
 303  * The returned session will be deleted when its file descriptor is closed.
 304  */
 305 static
 306 long lttng_cmd(int objd, unsigned int cmd, unsigned long arg)
 307 {
 308         switch (cmd) {
 309         case LTTNG_UST_SESSION:
 310                 return lttng_abi_create_session();
 311         case LTTNG_UST_TRACER_VERSION:
 312                 return lttng_abi_tracer_version(objd,
 313                                 (struct lttng_ust_tracer_version *) arg);
 314         case LTTNG_UST_TRACEPOINT_LIST:
 315                 return -ENOSYS; //TODO
 316                 //return lttng_abi_tracepoint_list();
 317         case LTTNG_UST_WAIT_QUIESCENT:
 318                 synchronize_trace();
 319                 return 0;
 320         default:
 321                 return -EINVAL;
 322         }
 323 }
 324
 325 static const struct objd_ops lttng_ops = {
 326         .cmd = lttng_cmd,
 327 };
 328
 329 /*
 330  * We tolerate no failure in this function (if one happens, we print a dmesg
 331  * error, but cannot return any error, because the channel information is
 332  * invariant.
 333  */
 334 static
 335 void lttng_metadata_create_events(int channel_objd)
 336 {
 337         struct ltt_channel *channel = objd_private(channel_objd);
 338         static struct lttng_ust_event metadata_params = {
 339                 .instrumentation = LTTNG_UST_TRACEPOINT,
 340                 .name = "lttng_metadata",
 341         };
 342         struct ltt_event *event;
 343         int ret;
 344
 345         /*
 346          * We tolerate no failure path after event creation. It will stay
 347          * invariant for the rest of the session.
 348          */
 349         event = ltt_event_create(channel, &metadata_params, NULL);
 350         if (!event) {
 351                 ret = -EINVAL;
 352                 goto create_error;
 353         }
 354         return;
 355
 356 create_error:
 357         WARN_ON(1);
 358         return;         /* not allowed to return error */
 359 }
 360
 361 int lttng_abi_create_channel(int session_objd,
 362                              struct lttng_ust_channel *chan_param,
 363                              enum channel_type channel_type)
 364 {
 365         struct ltt_session *session = objd_private(session_objd);
 366         const struct objd_ops *ops;
 367         const char *transport_name;
 368         struct ltt_channel *chan;
 369         int chan_objd;
 370         int ret = 0;
 371
 372         chan_objd = objd_alloc(NULL, &lttng_channel_ops);
 373         if (chan_objd < 0) {
 374                 ret = chan_objd;
 375                 goto objd_error;
 376         }
 377         switch (channel_type) {
 378         case PER_CPU_CHANNEL:
 379                 if (chan_param->output == LTTNG_UST_MMAP) {
 380                         transport_name = chan_param->overwrite ?
 381                                 "relay-overwrite-mmap" : "relay-discard-mmap";
 382                 } else {
 383                         return -EINVAL;
 384                 }
 385                 ops = &lttng_channel_ops;
 386                 break;
 387         case METADATA_CHANNEL:
 388                 if (chan_param->output == LTTNG_UST_MMAP)
 389                         transport_name = "relay-metadata-mmap";
 390                 else
 391                         return -EINVAL;
 392                 ops = &lttng_metadata_ops;
 393                 break;
 394         default:
 395                 transport_name = "<unknown>";
 396                 break;
 397         }
 398         /*
 399          * We tolerate no failure path after channel creation. It will stay
 400          * invariant for the rest of the session.
 401          */
 402         chan = ltt_channel_create(session, transport_name, NULL,
 403                                   chan_param->subbuf_size,
 404                                   chan_param->num_subbuf,
 405                                   chan_param->switch_timer_interval,
 406                                   chan_param->read_timer_interval,
 407                                   &chan_param->shm_fd,
 408                                   &chan_param->wait_fd,
 409                                   &chan_param->memory_map_size);
 410         if (!chan) {
 411                 ret = -EINVAL;
 412                 goto chan_error;
 413         }
 414         objd_set_private(chan_objd, chan);
 415         chan->objd = chan_objd;
 416         if (channel_type == METADATA_CHANNEL) {
 417                 session->metadata = chan;
 418                 lttng_metadata_create_events(chan_objd);
 419         }
 420
 421         /* The channel created holds a reference on the session */
 422         objd_ref(session_objd);
 423
 424         return chan_objd;
 425
 426 chan_error:
 427         {
 428                 int err;
 429
 430                 err = objd_unref(chan_objd);
 431                 assert(!err);
 432         }
 433 objd_error:
 434         return ret;
 435 }
 436
 437 /**
 438  *      lttng_session_cmd - lttng session object command
 439  *
 440  *      @obj: the object
 441  *      @cmd: the command
 442  *      @arg: command arg
 443  *
 444  *      This descriptor implements lttng commands:
 445  *      LTTNG_UST_CHANNEL
 446  *              Returns a LTTng channel object descriptor
 447  *      LTTNG_UST_ENABLE
 448  *              Enables tracing for a session (weak enable)
 449  *      LTTNG_UST_DISABLE
 450  *              Disables tracing for a session (strong disable)
 451  *      LTTNG_UST_METADATA
 452  *              Returns a LTTng metadata object descriptor
 453  *
 454  * The returned channel will be deleted when its file descriptor is closed.
 455  */
 456 static
 457 long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg)
 458 {
 459         struct ltt_session *session = objd_private(objd);
 460
 461         switch (cmd) {
 462         case LTTNG_UST_CHANNEL:
 463                 return lttng_abi_create_channel(objd,
 464                                 (struct lttng_ust_channel *) arg,
 465                                 PER_CPU_CHANNEL);
 466         case LTTNG_UST_SESSION_START:
 467         case LTTNG_UST_ENABLE:
 468                 return ltt_session_enable(session);
 469         case LTTNG_UST_SESSION_STOP:
 470         case LTTNG_UST_DISABLE:
 471                 return ltt_session_disable(session);
 472         case LTTNG_UST_METADATA:
 473                 return lttng_abi_create_channel(objd,
 474                                 (struct lttng_ust_channel *) arg,
 475                                 METADATA_CHANNEL);
 476         default:
 477                 return -EINVAL;
 478         }
 479 }
 480
 481 /*
 482  * Called when the last file reference is dropped.
 483  *
 484  * Big fat note: channels and events are invariant for the whole session after
 485  * their creation. So this session destruction also destroys all channel and
 486  * event structures specific to this session (they are not destroyed when their
 487  * individual file is released).
 488  */
 489 static
 490 int lttng_release_session(int objd)
 491 {
 492         struct ltt_session *session = objd_private(objd);
 493
 494         if (session) {
 495                 ltt_session_destroy(session);
 496                 return 0;
 497         } else {
 498                 return -EINVAL;
 499         }
 500 }
 501
 502 static const struct objd_ops lttng_session_ops = {
 503         .release = lttng_release_session,
 504         .cmd = lttng_session_cmd,
 505 };
 506
 507 struct stream_priv_data {
 508         struct lib_ring_buffer *buf;
 509         struct ltt_channel *ltt_chan;
 510 };
 511
 512 static
 513 int lttng_abi_open_stream(int channel_objd, struct lttng_ust_stream *info)
 514 {
 515         struct ltt_channel *channel = objd_private(channel_objd);
 516         struct lib_ring_buffer *buf;
 517         struct stream_priv_data *priv;
 518         int stream_objd, ret;
 519
 520         buf = channel->ops->buffer_read_open(channel->chan, channel->handle,
 521                         &info->shm_fd, &info->wait_fd, &info->memory_map_size);
 522         if (!buf)
 523                 return -ENOENT;
 524
 525         priv = zmalloc(sizeof(*priv));
 526         if (!priv) {
 527                 ret = -ENOMEM;
 528                 goto alloc_error;
 529         }
 530         priv->buf = buf;
 531         priv->ltt_chan = channel;
 532         stream_objd = objd_alloc(priv, &lib_ring_buffer_objd_ops);
 533         if (stream_objd < 0) {
 534                 ret = stream_objd;
 535                 goto objd_error;
 536         }
 537         /* Hold a reference on the channel object descriptor */
 538         objd_ref(channel_objd);
 539         return stream_objd;
 540
 541 objd_error:
 542         free(priv);
 543 alloc_error:
 544         channel->ops->buffer_read_close(buf, channel->handle);
 545         return ret;
 546 }
 547
 548 static
 549 int lttng_abi_create_event(int channel_objd,
 550                            struct lttng_ust_event *event_param)
 551 {
 552         struct ltt_channel *channel = objd_private(channel_objd);
 553         struct ltt_event *event;
 554         int event_objd, ret;
 555
 556         event_param->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 557         event_objd = objd_alloc(NULL, &lttng_event_ops);
 558         if (event_objd < 0) {
 559                 ret = event_objd;
 560                 goto objd_error;
 561         }
 562         /*
 563          * We tolerate no failure path after event creation. It will stay
 564          * invariant for the rest of the session.
 565          */
 566         event = ltt_event_create(channel, event_param, NULL);
 567         if (!event) {
 568                 ret = -EINVAL;
 569                 goto event_error;
 570         }
 571         objd_set_private(event_objd, event);
 572         /* The event holds a reference on the channel */
 573         objd_ref(channel_objd);
 574         return event_objd;
 575
 576 event_error:
 577         {
 578                 int err;
 579
 580                 err = objd_unref(event_objd);
 581                 assert(!err);
 582         }
 583 objd_error:
 584         return ret;
 585 }
 586
 587 /**
 588  *      lttng_channel_cmd - lttng control through object descriptors
 589  *
 590  *      @objd: the object descriptor
 591  *      @cmd: the command
 592  *      @arg: command arg
 593  *
 594  *      This object descriptor implements lttng commands:
 595  *      LTTNG_UST_STREAM
 596  *              Returns an event stream object descriptor or failure.
 597  *              (typically, one event stream records events from one CPU)
 598  *      LTTNG_UST_EVENT
 599  *              Returns an event object descriptor or failure.
 600  *      LTTNG_UST_CONTEXT
 601  *              Prepend a context field to each event in the channel
 602  *      LTTNG_UST_ENABLE
 603  *              Enable recording for events in this channel (weak enable)
 604  *      LTTNG_UST_DISABLE
 605  *              Disable recording for events in this channel (strong disable)
 606  *
 607  * Channel and event file descriptors also hold a reference on the session.
 608  */
 609 static
 610 long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg)
 611 {
 612         struct ltt_channel *channel = objd_private(objd);
 613
 614         switch (cmd) {
 615         case LTTNG_UST_STREAM:
 616         {
 617                 struct lttng_ust_stream *stream;
 618
 619                 stream = (struct lttng_ust_stream *) arg;
 620                 /* stream used as output */
 621                 return lttng_abi_open_stream(objd, stream);
 622         }
 623         case LTTNG_UST_EVENT:
 624                 return lttng_abi_create_event(objd, (struct lttng_ust_event *) arg);
 625         case LTTNG_UST_CONTEXT:
 626                 return lttng_abi_add_context(objd,
 627                                 (struct lttng_ust_context *) arg,
 628                                 &channel->ctx, channel->session);
 629         case LTTNG_UST_ENABLE:
 630                 return ltt_channel_enable(channel);
 631         case LTTNG_UST_DISABLE:
 632                 return ltt_channel_disable(channel);
 633         default:
 634                 return -EINVAL;
 635         }
 636 }
 637
 638 /**
 639  *      lttng_metadata_cmd - lttng control through object descriptors
 640  *
 641  *      @objd: the object descriptor
 642  *      @cmd: the command
 643  *      @arg: command arg
 644  *
 645  *      This object descriptor implements lttng commands:
 646  *      LTTNG_UST_STREAM
 647  *              Returns an event stream file descriptor or failure.
 648  *
 649  * Channel and event file descriptors also hold a reference on the session.
 650  */
 651 static
 652 long lttng_metadata_cmd(int objd, unsigned int cmd, unsigned long arg)
 653 {
 654         switch (cmd) {
 655         case LTTNG_UST_STREAM:
 656         {
 657                 struct lttng_ust_stream *stream;
 658
 659                 stream = (struct lttng_ust_stream *) arg;
 660                 /* stream used as output */
 661                 return lttng_abi_open_stream(objd, stream);
 662         }
 663         default:
 664                 return -EINVAL;
 665         }
 666 }
 667
 668 #if 0
 669 /**
 670  *      lttng_channel_poll - lttng stream addition/removal monitoring
 671  *
 672  *      @file: the file
 673  *      @wait: poll table
 674  */
 675 unsigned int lttng_channel_poll(struct file *file, poll_table *wait)
 676 {
 677         struct ltt_channel *channel = file->private_data;
 678         unsigned int mask = 0;
 679
 680         if (file->f_mode & FMODE_READ) {
 681                 poll_wait_set_exclusive(wait);
 682                 poll_wait(file, channel->ops->get_hp_wait_queue(channel->chan),
 683                           wait);
 684
 685                 if (channel->ops->is_disabled(channel->chan))
 686                         return POLLERR;
 687                 if (channel->ops->is_finalized(channel->chan))
 688                         return POLLHUP;
 689                 if (channel->ops->buffer_has_read_closed_stream(channel->chan))
 690                         return POLLIN | POLLRDNORM;
 691                 return 0;
 692         }
 693         return mask;
 694
 695 }
 696 #endif //0
 697
 698 static
 699 int lttng_channel_release(int objd)
 700 {
 701         struct ltt_channel *channel = objd_private(objd);
 702
 703         if (channel)
 704                 return objd_unref(channel->session->objd);
 705         return 0;
 706 }
 707
 708 static const struct objd_ops lttng_channel_ops = {
 709         .release = lttng_channel_release,
 710         //.poll = lttng_channel_poll,
 711         .cmd = lttng_channel_cmd,
 712 };
 713
 714 static const struct objd_ops lttng_metadata_ops = {
 715         .release = lttng_channel_release,
 716         .cmd = lttng_metadata_cmd,
 717 };
 718
 719 /**
 720  *      lttng_rb_cmd - lttng ring buffer control through object descriptors
 721  *
 722  *      @objd: the object descriptor
 723  *      @cmd: the command
 724  *      @arg: command arg
 725  *
 726  *      This object descriptor implements lttng commands:
 727  *              (None for now. Access is done directly though shm.)
 728  *              TODO: Add buffer flush.
 729  */
 730 static
 731 long lttng_rb_cmd(int objd, unsigned int cmd, unsigned long arg)
 732 {
 733         //struct stream_priv_data *priv = objd_private(objd);
 734
 735         switch (cmd) {
 736         default:
 737                 return -EINVAL;
 738         }
 739 }
 740
 741 static
 742 int lttng_rb_release(int objd)
 743 {
 744         struct stream_priv_data *priv = objd_private(objd);
 745         struct lib_ring_buffer *buf;
 746         struct ltt_channel *channel;
 747
 748         if (priv) {
 749                 buf = priv->buf;
 750                 channel = priv->ltt_chan;
 751                 free(priv);
 752                 channel->ops->buffer_read_close(buf, channel->handle);
 753
 754                 return objd_unref(channel->objd);
 755         }
 756         return 0;
 757 }
 758
 759 static const struct objd_ops lib_ring_buffer_objd_ops = {
 760         .release = lttng_rb_release,
 761         .cmd = lttng_rb_cmd,
 762 };
 763
 764 /**
 765  *      lttng_event_cmd - lttng control through object descriptors
 766  *
 767  *      @objd: the object descriptor
 768  *      @cmd: the command
 769  *      @arg: command arg
 770  *
 771  *      This object descriptor implements lttng commands:
 772  *      LTTNG_UST_CONTEXT
 773  *              Prepend a context field to each record of this event
 774  *      LTTNG_UST_ENABLE
 775  *              Enable recording for this event (weak enable)
 776  *      LTTNG_UST_DISABLE
 777  *              Disable recording for this event (strong disable)
 778  */
 779 static
 780 long lttng_event_cmd(int objd, unsigned int cmd, unsigned long arg)
 781 {
 782         struct ltt_event *event = objd_private(objd);
 783
 784         switch (cmd) {
 785         case LTTNG_UST_CONTEXT:
 786                 return lttng_abi_add_context(objd,
 787                                 (struct lttng_ust_context *) arg,
 788                                 &event->ctx, event->chan->session);
 789         case LTTNG_UST_ENABLE:
 790                 return ltt_event_enable(event);
 791         case LTTNG_UST_DISABLE:
 792                 return ltt_event_disable(event);
 793         default:
 794                 return -EINVAL;
 795         }
 796 }
 797
 798 static
 799 int lttng_event_release(int objd)
 800 {
 801         struct ltt_event *event = objd_private(objd);
 802
 803         if (event)
 804                 return objd_unref(event->chan->objd);
 805         return 0;
 806 }
 807
 808 /* TODO: filter control ioctl */
 809 static const struct objd_ops lttng_event_ops = {
 810         .release = lttng_event_release,
 811         .cmd = lttng_event_cmd,
 812 };
 813
 814 void lttng_ust_abi_exit(void)
 815 {
 816         objd_table_destroy();
 817 }