liblttng-ust/lttng-ust-abi.c

   1 /*
   2  * lttng-ust-abi.c
   3  *
   4  * LTTng UST ABI
   5  *
   6  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  *
  22  *
  23  * Mimic system calls for:
  24  * - session creation, returns an object descriptor or failure.
  25  *   - channel creation, returns an object descriptor or failure.
  26  *     - Operates on a session object descriptor
  27  *     - Takes all channel options as parameters.
  28  *   - stream get, returns an object descriptor or failure.
  29  *     - Operates on a channel object descriptor.
  30  *   - stream notifier get, returns an object descriptor or failure.
  31  *     - Operates on a channel object descriptor.
  32  *   - event creation, returns an object descriptor or failure.
  33  *     - Operates on a channel object descriptor
  34  *     - Takes an event name as parameter
  35  *     - Takes an instrumentation source as parameter
  36  *       - e.g. tracepoints, dynamic_probes...
  37  *     - Takes instrumentation source specific arguments.
  38  */
  39
  40 #include <lttng/ust-abi.h>
  41 #include <lttng/ust-error.h>
  42 #include <urcu/compiler.h>
  43 #include <urcu/list.h>
  44 #include <lttng/ust-events.h>
  45 #include <lttng/ust-version.h>
  46 #include <lttng/tracepoint.h>
  47 #include "tracepoint-internal.h"
  48 #include <usterr-signal-safe.h>
  49 #include <helper.h>
  50 #include "lttng-tracer.h"
  51 #include "../libringbuffer/shm.h"
  52 #include "../libringbuffer/frontend_types.h"
  53
  54 #define OBJ_NAME_LEN    16
  55
  56 static int lttng_ust_abi_close_in_progress;
  57
  58 static
  59 int lttng_abi_tracepoint_list(void *owner);
  60 static
  61 int lttng_abi_tracepoint_field_list(void *owner);
  62
  63 /*
  64  * Object descriptor table. Should be protected from concurrent access
  65  * by the caller.
  66  */
  67
  68 struct lttng_ust_obj {
  69         union {
  70                 struct {
  71                         void *private_data;
  72                         const struct lttng_ust_objd_ops *ops;
  73                         int f_count;
  74                         void *owner;
  75                         char name[OBJ_NAME_LEN];
  76                 } s;
  77                 int freelist_next;      /* offset freelist. end is -1. */
  78         } u;
  79 };
  80
  81 struct lttng_ust_objd_table {
  82         struct lttng_ust_obj *array;
  83         unsigned int len, allocated_len;
  84         int freelist_head;              /* offset freelist head. end is -1 */
  85 };
  86
  87 static struct lttng_ust_objd_table objd_table = {
  88         .freelist_head = -1,
  89 };
  90
  91 static
  92 int objd_alloc(void *private_data, const struct lttng_ust_objd_ops *ops,
  93                 void *owner, const char *name)
  94 {
  95         struct lttng_ust_obj *obj;
  96
  97         if (objd_table.freelist_head != -1) {
  98                 obj = &objd_table.array[objd_table.freelist_head];
  99                 objd_table.freelist_head = obj->u.freelist_next;
 100                 goto end;
 101         }
 102
 103         if (objd_table.len >= objd_table.allocated_len) {
 104                 unsigned int new_allocated_len, old_allocated_len;
 105                 struct lttng_ust_obj *new_table, *old_table;
 106
 107                 old_allocated_len = objd_table.allocated_len;
 108                 old_table = objd_table.array;
 109                 if (!old_allocated_len)
 110                         new_allocated_len = 1;
 111                 else
 112                         new_allocated_len = old_allocated_len << 1;
 113                 new_table = zmalloc(sizeof(struct lttng_ust_obj) * new_allocated_len);
 114                 if (!new_table)
 115                         return -ENOMEM;
 116                 memcpy(new_table, old_table,
 117                        sizeof(struct lttng_ust_obj) * old_allocated_len);
 118                 free(old_table);
 119                 objd_table.array = new_table;
 120                 objd_table.allocated_len = new_allocated_len;
 121         }
 122         obj = &objd_table.array[objd_table.len];
 123         objd_table.len++;
 124 end:
 125         obj->u.s.private_data = private_data;
 126         obj->u.s.ops = ops;
 127         obj->u.s.f_count = 2;   /* count == 1 : object is allocated */
 128                                 /* count == 2 : allocated + hold ref */
 129         obj->u.s.owner = owner;
 130         strncpy(obj->u.s.name, name, OBJ_NAME_LEN);
 131         obj->u.s.name[OBJ_NAME_LEN - 1] = '\0';
 132         return obj - objd_table.array;
 133 }
 134
 135 static
 136 struct lttng_ust_obj *_objd_get(int id)
 137 {
 138         if (id >= objd_table.len)
 139                 return NULL;
 140         if (!objd_table.array[id].u.s.f_count)
 141                 return NULL;
 142         return &objd_table.array[id];
 143 }
 144
 145 static
 146 void *objd_private(int id)
 147 {
 148         struct lttng_ust_obj *obj = _objd_get(id);
 149         assert(obj);
 150         return obj->u.s.private_data;
 151 }
 152
 153 static
 154 void objd_set_private(int id, void *private_data)
 155 {
 156         struct lttng_ust_obj *obj = _objd_get(id);
 157         assert(obj);
 158         obj->u.s.private_data = private_data;
 159 }
 160
 161 const struct lttng_ust_objd_ops *objd_ops(int id)
 162 {
 163         struct lttng_ust_obj *obj = _objd_get(id);
 164
 165         if (!obj)
 166                 return NULL;
 167         return obj->u.s.ops;
 168 }
 169
 170 static
 171 void objd_free(int id)
 172 {
 173         struct lttng_ust_obj *obj = _objd_get(id);
 174
 175         assert(obj);
 176         obj->u.freelist_next = objd_table.freelist_head;
 177         objd_table.freelist_head = obj - objd_table.array;
 178         assert(obj->u.s.f_count == 1);
 179         obj->u.s.f_count = 0;   /* deallocated */
 180 }
 181
 182 static
 183 void objd_ref(int id)
 184 {
 185         struct lttng_ust_obj *obj = _objd_get(id);
 186         obj->u.s.f_count++;
 187 }
 188
 189 int lttng_ust_objd_unref(int id)
 190 {
 191         struct lttng_ust_obj *obj = _objd_get(id);
 192
 193         if (!obj)
 194                 return -EINVAL;
 195         if (obj->u.s.f_count == 1) {
 196                 ERR("Reference counting error\n");
 197                 return -EINVAL;
 198         }
 199         if ((--obj->u.s.f_count) == 1) {
 200                 const struct lttng_ust_objd_ops *ops = objd_ops(id);
 201
 202                 if (ops->release)
 203                         ops->release(id);
 204                 objd_free(id);
 205         }
 206         return 0;
 207 }
 208
 209 static
 210 void objd_table_destroy(void)
 211 {
 212         int i;
 213
 214         for (i = 0; i < objd_table.allocated_len; i++)
 215                 (void) lttng_ust_objd_unref(i);
 216         free(objd_table.array);
 217         objd_table.array = NULL;
 218         objd_table.len = 0;
 219         objd_table.allocated_len = 0;
 220         objd_table.freelist_head = -1;
 221 }
 222
 223 const char *lttng_ust_obj_get_name(int id)
 224 {
 225         struct lttng_ust_obj *obj = _objd_get(id);
 226
 227         if (!obj)
 228                 return NULL;
 229         return obj->u.s.name;
 230 }
 231
 232 void lttng_ust_objd_table_owner_cleanup(void *owner)
 233 {
 234         int i;
 235
 236         for (i = 0; i < objd_table.allocated_len; i++) {
 237                 struct lttng_ust_obj *obj;
 238
 239                 obj = _objd_get(i);
 240                 if (!obj)
 241                         continue;
 242                 if (!obj->u.s.owner)
 243                         continue;       /* skip root handles */
 244                 if (obj->u.s.owner == owner)
 245                         (void) lttng_ust_objd_unref(i);
 246         }
 247 }
 248
 249 /*
 250  * This is LTTng's own personal way to create an ABI for sessiond.
 251  * We send commands over a socket.
 252  */
 253
 254 static const struct lttng_ust_objd_ops lttng_ops;
 255 static const struct lttng_ust_objd_ops lttng_session_ops;
 256 static const struct lttng_ust_objd_ops lttng_channel_ops;
 257 static const struct lttng_ust_objd_ops lttng_enabler_ops;
 258 static const struct lttng_ust_objd_ops lttng_tracepoint_list_ops;
 259 static const struct lttng_ust_objd_ops lttng_tracepoint_field_list_ops;
 260
 261 int lttng_abi_create_root_handle(void)
 262 {
 263         int root_handle;
 264
 265         /* root handles have NULL owners */
 266         root_handle = objd_alloc(NULL, &lttng_ops, NULL, "root");
 267         return root_handle;
 268 }
 269
 270 static
 271 int lttng_is_channel_ready(struct lttng_channel *lttng_chan)
 272 {
 273         struct channel *chan;
 274         unsigned int nr_streams, exp_streams;
 275
 276         chan = lttng_chan->chan;
 277         nr_streams = channel_handle_get_nr_streams(lttng_chan->handle);
 278         exp_streams = chan->nr_streams;
 279         return nr_streams == exp_streams;
 280 }
 281
 282 static
 283 int lttng_abi_create_session(void *owner)
 284 {
 285         struct lttng_session *session;
 286         int session_objd, ret;
 287
 288         session = lttng_session_create();
 289         if (!session)
 290                 return -ENOMEM;
 291         session_objd = objd_alloc(session, &lttng_session_ops, owner, "session");
 292         if (session_objd < 0) {
 293                 ret = session_objd;
 294                 goto objd_error;
 295         }
 296         session->objd = session_objd;
 297         session->owner = owner;
 298         return session_objd;
 299
 300 objd_error:
 301         lttng_session_destroy(session);
 302         return ret;
 303 }
 304
 305 static
 306 long lttng_abi_tracer_version(int objd,
 307         struct lttng_ust_tracer_version *v)
 308 {
 309         v->major = LTTNG_UST_MAJOR_VERSION;
 310         v->minor = LTTNG_UST_MINOR_VERSION;
 311         v->patchlevel = LTTNG_UST_PATCHLEVEL_VERSION;
 312         return 0;
 313 }
 314
 315 static
 316 long lttng_abi_add_context(int objd,
 317         struct lttng_ust_context *context_param,
 318         struct lttng_ctx **ctx, struct lttng_session *session)
 319 {
 320         return lttng_attach_context(context_param, ctx, session);
 321 }
 322
 323 /**
 324  *      lttng_cmd - lttng control through socket commands
 325  *
 326  *      @objd: the object descriptor
 327  *      @cmd: the command
 328  *      @arg: command arg
 329  *      @uargs: UST arguments (internal)
 330  *      @owner: objd owner
 331  *
 332  *      This descriptor implements lttng commands:
 333  *      LTTNG_UST_SESSION
 334  *              Returns a LTTng trace session object descriptor
 335  *      LTTNG_UST_TRACER_VERSION
 336  *              Returns the LTTng kernel tracer version
 337  *      LTTNG_UST_TRACEPOINT_LIST
 338  *              Returns a file descriptor listing available tracepoints
 339  *      LTTNG_UST_TRACEPOINT_FIELD_LIST
 340  *              Returns a file descriptor listing available tracepoint fields
 341  *      LTTNG_UST_WAIT_QUIESCENT
 342  *              Returns after all previously running probes have completed
 343  *
 344  * The returned session will be deleted when its file descriptor is closed.
 345  */
 346 static
 347 long lttng_cmd(int objd, unsigned int cmd, unsigned long arg,
 348         union ust_args *uargs, void *owner)
 349 {
 350         switch (cmd) {
 351         case LTTNG_UST_SESSION:
 352                 return lttng_abi_create_session(owner);
 353         case LTTNG_UST_TRACER_VERSION:
 354                 return lttng_abi_tracer_version(objd,
 355                                 (struct lttng_ust_tracer_version *) arg);
 356         case LTTNG_UST_TRACEPOINT_LIST:
 357                 return lttng_abi_tracepoint_list(owner);
 358         case LTTNG_UST_TRACEPOINT_FIELD_LIST:
 359                 return lttng_abi_tracepoint_field_list(owner);
 360         case LTTNG_UST_WAIT_QUIESCENT:
 361                 synchronize_trace();
 362                 return 0;
 363         default:
 364                 return -EINVAL;
 365         }
 366 }
 367
 368 static const struct lttng_ust_objd_ops lttng_ops = {
 369         .cmd = lttng_cmd,
 370 };
 371
 372 int lttng_abi_map_channel(int session_objd,
 373                 struct lttng_ust_channel *ust_chan,
 374                 union ust_args *uargs,
 375                 void *owner)
 376 {
 377         struct lttng_session *session = objd_private(session_objd);
 378         const char *transport_name;
 379         const struct lttng_transport *transport;
 380         const char *chan_name;
 381         int chan_objd;
 382         struct lttng_ust_shm_handle *channel_handle;
 383         struct lttng_channel *lttng_chan;
 384         struct channel *chan;
 385         struct lttng_ust_lib_ring_buffer_config *config;
 386         void *chan_data;
 387         uint64_t len;
 388         int ret;
 389         enum lttng_ust_chan_type type;
 390
 391         chan_data = uargs->channel.chan_data;
 392         len = ust_chan->len;
 393         type = ust_chan->type;
 394
 395         switch (type) {
 396         case LTTNG_UST_CHAN_PER_CPU:
 397                 break;
 398         default:
 399                 return -EINVAL;
 400         }
 401
 402         if (session->been_active) {
 403                 ret = -EBUSY;
 404                 goto active;    /* Refuse to add channel to active session */
 405         }
 406
 407         channel_handle = channel_handle_create(chan_data, len);
 408         if (!channel_handle) {
 409                 ret = -EINVAL;
 410                 goto handle_error;
 411         }
 412
 413         chan = shmp(channel_handle, channel_handle->chan);
 414         assert(chan);
 415         config = &chan->backend.config;
 416         lttng_chan = channel_get_private(chan);
 417         if (!lttng_chan) {
 418                 ret = -EINVAL;
 419                 goto alloc_error;
 420         }
 421
 422         /* Lookup transport name */
 423         switch (type) {
 424         case LTTNG_UST_CHAN_PER_CPU:
 425                 if (config->output == RING_BUFFER_MMAP) {
 426                         transport_name = config->mode == RING_BUFFER_OVERWRITE ?
 427                                 "relay-overwrite-mmap" : "relay-discard-mmap";
 428                 } else {
 429                         ret = -EINVAL;
 430                         goto notransport;
 431                 }
 432                 chan_name = "channel";
 433                 break;
 434         default:
 435                 transport_name = "<unknown>";
 436                 chan_name = "<unknown>";
 437                 ret = -EINVAL;
 438                 goto notransport;
 439         }
 440         transport = lttng_transport_find(transport_name);
 441         if (!transport) {
 442                 DBG("LTTng transport %s not found\n",
 443                        transport_name);
 444                 ret = -EINVAL;
 445                 goto notransport;
 446         }
 447
 448         chan_objd = objd_alloc(NULL, &lttng_channel_ops, owner, chan_name);
 449         if (chan_objd < 0) {
 450                 ret = chan_objd;
 451                 goto objd_error;
 452         }
 453
 454         /* Initialize our lttng chan */
 455         lttng_chan->chan = chan;
 456         lttng_chan->enabled = 1;
 457         lttng_chan->ctx = NULL;
 458         lttng_chan->session = session;
 459         lttng_chan->ops = &transport->ops;
 460         memcpy(&lttng_chan->chan->backend.config,
 461                 transport->client_config,
 462                 sizeof(lttng_chan->chan->backend.config));
 463         cds_list_add(&lttng_chan->node, &session->chan_head);
 464         lttng_chan->header_type = 0;
 465         lttng_chan->handle = channel_handle;
 466         lttng_chan->type = type;
 467
 468         /*
 469          * We tolerate no failure path after channel creation. It will stay
 470          * invariant for the rest of the session.
 471          */
 472         objd_set_private(chan_objd, lttng_chan);
 473         lttng_chan->objd = chan_objd;
 474         /* The channel created holds a reference on the session */
 475         objd_ref(session_objd);
 476         return chan_objd;
 477
 478 objd_error:
 479 notransport:
 480         free(lttng_chan);
 481 alloc_error:
 482         channel_destroy(chan, channel_handle, 0);
 483 handle_error:
 484 active:
 485         return ret;
 486 }
 487
 488 /**
 489  *      lttng_session_cmd - lttng session object command
 490  *
 491  *      @obj: the object
 492  *      @cmd: the command
 493  *      @arg: command arg
 494  *      @uargs: UST arguments (internal)
 495  *      @owner: objd owner
 496  *
 497  *      This descriptor implements lttng commands:
 498  *      LTTNG_UST_CHANNEL
 499  *              Returns a LTTng channel object descriptor
 500  *      LTTNG_UST_ENABLE
 501  *              Enables tracing for a session (weak enable)
 502  *      LTTNG_UST_DISABLE
 503  *              Disables tracing for a session (strong disable)
 504  *
 505  * The returned channel will be deleted when its file descriptor is closed.
 506  */
 507 static
 508 long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg,
 509         union ust_args *uargs, void *owner)
 510 {
 511         struct lttng_session *session = objd_private(objd);
 512
 513         switch (cmd) {
 514         case LTTNG_UST_CHANNEL:
 515                 return lttng_abi_map_channel(objd,
 516                                 (struct lttng_ust_channel *) arg,
 517                                 uargs, owner);
 518         case LTTNG_UST_SESSION_START:
 519         case LTTNG_UST_ENABLE:
 520                 return lttng_session_enable(session);
 521         case LTTNG_UST_SESSION_STOP:
 522         case LTTNG_UST_DISABLE:
 523                 return lttng_session_disable(session);
 524         default:
 525                 return -EINVAL;
 526         }
 527 }
 528
 529 /*
 530  * Called when the last file reference is dropped.
 531  *
 532  * Big fat note: channels and events are invariant for the whole session after
 533  * their creation. So this session destruction also destroys all channel and
 534  * event structures specific to this session (they are not destroyed when their
 535  * individual file is released).
 536  */
 537 static
 538 int lttng_release_session(int objd)
 539 {
 540         struct lttng_session *session = objd_private(objd);
 541
 542         if (session) {
 543                 lttng_session_destroy(session);
 544                 return 0;
 545         } else {
 546                 return -EINVAL;
 547         }
 548 }
 549
 550 static const struct lttng_ust_objd_ops lttng_session_ops = {
 551         .release = lttng_release_session,
 552         .cmd = lttng_session_cmd,
 553 };
 554
 555 static
 556 long lttng_tracepoint_list_cmd(int objd, unsigned int cmd, unsigned long arg,
 557         union ust_args *uargs, void *owner)
 558 {
 559         struct lttng_ust_tracepoint_list *list = objd_private(objd);
 560         struct lttng_ust_tracepoint_iter *tp =
 561                 (struct lttng_ust_tracepoint_iter *) arg;
 562         struct lttng_ust_tracepoint_iter *iter;
 563
 564         switch (cmd) {
 565         case LTTNG_UST_TRACEPOINT_LIST_GET:
 566         {
 567                 iter = lttng_ust_tracepoint_list_get_iter_next(list);
 568                 if (!iter)
 569                         return -LTTNG_UST_ERR_NOENT;
 570                 memcpy(tp, iter, sizeof(*tp));
 571                 return 0;
 572         }
 573         default:
 574                 return -EINVAL;
 575         }
 576 }
 577
 578 static
 579 int lttng_abi_tracepoint_list(void *owner)
 580 {
 581         int list_objd, ret;
 582         struct lttng_ust_tracepoint_list *list;
 583
 584         list_objd = objd_alloc(NULL, &lttng_tracepoint_list_ops, owner, "tp_list");
 585         if (list_objd < 0) {
 586                 ret = list_objd;
 587                 goto objd_error;
 588         }
 589         list = zmalloc(sizeof(*list));
 590         if (!list) {
 591                 ret = -ENOMEM;
 592                 goto alloc_error;
 593         }
 594         objd_set_private(list_objd, list);
 595
 596         /* populate list by walking on all registered probes. */
 597         ret = lttng_probes_get_event_list(list);
 598         if (ret) {
 599                 goto list_error;
 600         }
 601         return list_objd;
 602
 603 list_error:
 604         free(list);
 605 alloc_error:
 606         {
 607                 int err;
 608
 609                 err = lttng_ust_objd_unref(list_objd);
 610                 assert(!err);
 611         }
 612 objd_error:
 613         return ret;
 614 }
 615
 616 static
 617 int lttng_release_tracepoint_list(int objd)
 618 {
 619         struct lttng_ust_tracepoint_list *list = objd_private(objd);
 620
 621         if (list) {
 622                 lttng_probes_prune_event_list(list);
 623                 free(list);
 624                 return 0;
 625         } else {
 626                 return -EINVAL;
 627         }
 628 }
 629
 630 static const struct lttng_ust_objd_ops lttng_tracepoint_list_ops = {
 631         .release = lttng_release_tracepoint_list,
 632         .cmd = lttng_tracepoint_list_cmd,
 633 };
 634
 635 static
 636 long lttng_tracepoint_field_list_cmd(int objd, unsigned int cmd,
 637         unsigned long arg, union ust_args *uargs, void *owner)
 638 {
 639         struct lttng_ust_field_list *list = objd_private(objd);
 640         struct lttng_ust_field_iter *tp = &uargs->field_list.entry;
 641         struct lttng_ust_field_iter *iter;
 642
 643         switch (cmd) {
 644         case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
 645         {
 646                 iter = lttng_ust_field_list_get_iter_next(list);
 647                 if (!iter)
 648                         return -LTTNG_UST_ERR_NOENT;
 649                 memcpy(tp, iter, sizeof(*tp));
 650                 return 0;
 651         }
 652         default:
 653                 return -EINVAL;
 654         }
 655 }
 656
 657 static
 658 int lttng_abi_tracepoint_field_list(void *owner)
 659 {
 660         int list_objd, ret;
 661         struct lttng_ust_field_list *list;
 662
 663         list_objd = objd_alloc(NULL, &lttng_tracepoint_field_list_ops, owner,
 664                         "tp_field_list");
 665         if (list_objd < 0) {
 666                 ret = list_objd;
 667                 goto objd_error;
 668         }
 669         list = zmalloc(sizeof(*list));
 670         if (!list) {
 671                 ret = -ENOMEM;
 672                 goto alloc_error;
 673         }
 674         objd_set_private(list_objd, list);
 675
 676         /* populate list by walking on all registered probes. */
 677         ret = lttng_probes_get_field_list(list);
 678         if (ret) {
 679                 goto list_error;
 680         }
 681         return list_objd;
 682
 683 list_error:
 684         free(list);
 685 alloc_error:
 686         {
 687                 int err;
 688
 689                 err = lttng_ust_objd_unref(list_objd);
 690                 assert(!err);
 691         }
 692 objd_error:
 693         return ret;
 694 }
 695
 696 static
 697 int lttng_release_tracepoint_field_list(int objd)
 698 {
 699         struct lttng_ust_field_list *list = objd_private(objd);
 700
 701         if (list) {
 702                 lttng_probes_prune_field_list(list);
 703                 free(list);
 704                 return 0;
 705         } else {
 706                 return -EINVAL;
 707         }
 708 }
 709
 710 static const struct lttng_ust_objd_ops lttng_tracepoint_field_list_ops = {
 711         .release = lttng_release_tracepoint_field_list,
 712         .cmd = lttng_tracepoint_field_list_cmd,
 713 };
 714
 715 static
 716 int lttng_abi_map_stream(int channel_objd, struct lttng_ust_stream *info,
 717                 union ust_args *uargs, void *owner)
 718 {
 719         struct lttng_channel *channel = objd_private(channel_objd);
 720         int ret;
 721
 722         ret = channel_handle_add_stream(channel->handle,
 723                 uargs->stream.shm_fd, uargs->stream.wakeup_fd,
 724                 info->stream_nr, info->len);
 725         if (ret)
 726                 goto error_add_stream;
 727
 728         return 0;
 729
 730 error_add_stream:
 731         return ret;
 732 }
 733
 734 static
 735 int lttng_abi_create_enabler(int channel_objd,
 736                            struct lttng_ust_event *event_param,
 737                            void *owner,
 738                            enum lttng_enabler_type type)
 739 {
 740         struct lttng_channel *channel = objd_private(channel_objd);
 741         struct lttng_enabler *enabler;
 742         int event_objd, ret;
 743
 744         event_param->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 745         event_objd = objd_alloc(NULL, &lttng_enabler_ops, owner, "enabler");
 746         if (event_objd < 0) {
 747                 ret = event_objd;
 748                 goto objd_error;
 749         }
 750         /*
 751          * We tolerate no failure path after event creation. It will stay
 752          * invariant for the rest of the session.
 753          */
 754         enabler = lttng_enabler_create(type, event_param, channel);
 755         if (!enabler) {
 756                 ret = -ENOMEM;
 757                 goto event_error;
 758         }
 759         objd_set_private(event_objd, enabler);
 760         /* The event holds a reference on the channel */
 761         objd_ref(channel_objd);
 762         return event_objd;
 763
 764 event_error:
 765         {
 766                 int err;
 767
 768                 err = lttng_ust_objd_unref(event_objd);
 769                 assert(!err);
 770         }
 771 objd_error:
 772         return ret;
 773 }
 774
 775 /**
 776  *      lttng_channel_cmd - lttng control through object descriptors
 777  *
 778  *      @objd: the object descriptor
 779  *      @cmd: the command
 780  *      @arg: command arg
 781  *      @uargs: UST arguments (internal)
 782  *      @owner: objd owner
 783  *
 784  *      This object descriptor implements lttng commands:
 785  *      LTTNG_UST_STREAM
 786  *              Returns an event stream object descriptor or failure.
 787  *              (typically, one event stream records events from one CPU)
 788  *      LTTNG_UST_EVENT
 789  *              Returns an event object descriptor or failure.
 790  *      LTTNG_UST_CONTEXT
 791  *              Prepend a context field to each event in the channel
 792  *      LTTNG_UST_ENABLE
 793  *              Enable recording for events in this channel (weak enable)
 794  *      LTTNG_UST_DISABLE
 795  *              Disable recording for events in this channel (strong disable)
 796  *
 797  * Channel and event file descriptors also hold a reference on the session.
 798  */
 799 static
 800 long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg,
 801         union ust_args *uargs, void *owner)
 802 {
 803         struct lttng_channel *channel = objd_private(objd);
 804
 805         if (cmd != LTTNG_UST_STREAM) {
 806                 /*
 807                  * Check if channel received all streams.
 808                  */
 809                 if (!lttng_is_channel_ready(channel))
 810                         return -EPERM;
 811         }
 812
 813         switch (cmd) {
 814         case LTTNG_UST_STREAM:
 815         {
 816                 struct lttng_ust_stream *stream;
 817
 818                 stream = (struct lttng_ust_stream *) arg;
 819                 /* stream used as output */
 820                 return lttng_abi_map_stream(objd, stream, uargs, owner);
 821         }
 822         case LTTNG_UST_EVENT:
 823         {
 824                 struct lttng_ust_event *event_param =
 825                         (struct lttng_ust_event *) arg;
 826                 if (event_param->name[strlen(event_param->name) - 1] == '*') {
 827                         /* If ends with wildcard, create wildcard. */
 828                         return lttng_abi_create_enabler(objd, event_param,
 829                                         owner, LTTNG_ENABLER_WILDCARD);
 830                 } else {
 831                         return lttng_abi_create_enabler(objd, event_param,
 832                                         owner, LTTNG_ENABLER_EVENT);
 833                 }
 834         }
 835         case LTTNG_UST_CONTEXT:
 836                 return lttng_abi_add_context(objd,
 837                                 (struct lttng_ust_context *) arg,
 838                                 &channel->ctx, channel->session);
 839         case LTTNG_UST_ENABLE:
 840                 return lttng_channel_enable(channel);
 841         case LTTNG_UST_DISABLE:
 842                 return lttng_channel_disable(channel);
 843         case LTTNG_UST_FLUSH_BUFFER:
 844                 return channel->ops->flush_buffer(channel->chan, channel->handle);
 845         default:
 846                 return -EINVAL;
 847         }
 848 }
 849
 850 static
 851 int lttng_channel_release(int objd)
 852 {
 853         struct lttng_channel *channel = objd_private(objd);
 854
 855         if (channel)
 856                 return lttng_ust_objd_unref(channel->session->objd);
 857         return 0;
 858 }
 859
 860 static const struct lttng_ust_objd_ops lttng_channel_ops = {
 861         .release = lttng_channel_release,
 862         .cmd = lttng_channel_cmd,
 863 };
 864
 865 /**
 866  *      lttng_enabler_cmd - lttng control through object descriptors
 867  *
 868  *      @objd: the object descriptor
 869  *      @cmd: the command
 870  *      @arg: command arg
 871  *      @uargs: UST arguments (internal)
 872  *      @owner: objd owner
 873  *
 874  *      This object descriptor implements lttng commands:
 875  *      LTTNG_UST_CONTEXT
 876  *              Prepend a context field to each record of events of this
 877  *              enabler.
 878  *      LTTNG_UST_ENABLE
 879  *              Enable recording for this enabler
 880  *      LTTNG_UST_DISABLE
 881  *              Disable recording for this enabler
 882  *      LTTNG_UST_FILTER
 883  *              Attach a filter to an enabler.
 884  */
 885 static
 886 long lttng_enabler_cmd(int objd, unsigned int cmd, unsigned long arg,
 887         union ust_args *uargs, void *owner)
 888 {
 889         struct lttng_enabler *enabler = objd_private(objd);
 890
 891         switch (cmd) {
 892         case LTTNG_UST_CONTEXT:
 893                 return lttng_enabler_attach_context(enabler,
 894                                 (struct lttng_ust_context *) arg);
 895         case LTTNG_UST_ENABLE:
 896                 return lttng_enabler_enable(enabler);
 897         case LTTNG_UST_DISABLE:
 898                 return lttng_enabler_disable(enabler);
 899         case LTTNG_UST_FILTER:
 900         {
 901                 int ret;
 902
 903                 ret = lttng_enabler_attach_bytecode(enabler,
 904                                 (struct lttng_ust_filter_bytecode_node *) arg);
 905                 if (ret)
 906                         return ret;
 907                 return 0;
 908         }
 909         default:
 910                 return -EINVAL;
 911         }
 912 }
 913
 914 static
 915 int lttng_enabler_release(int objd)
 916 {
 917         struct lttng_enabler *enabler = objd_private(objd);
 918
 919         if (enabler)
 920                 return lttng_ust_objd_unref(enabler->chan->objd);
 921         return 0;
 922 }
 923
 924 static const struct lttng_ust_objd_ops lttng_enabler_ops = {
 925         .release = lttng_enabler_release,
 926         .cmd = lttng_enabler_cmd,
 927 };
 928
 929 void lttng_ust_abi_exit(void)
 930 {
 931         lttng_ust_abi_close_in_progress = 1;
 932         objd_table_destroy();
 933         lttng_ust_abi_close_in_progress = 0;
 934 }