liblttng-ust-ctl/ustctl.c

   1 /*
   2  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
   3  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; only version 2
   8  * of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18  */
  19
  20 #include <string.h>
  21 #include <lttng/ust-ctl.h>
  22 #include <lttng/ust-abi.h>
  23 #include <lttng/usterr-signal-safe.h>
  24 #include <lttng/ust-comm.h>
  25 #include <lttng/ust-events.h>
  26
  27 #include "../libringbuffer/backend.h"
  28 #include "../libringbuffer/frontend.h"
  29
  30 volatile enum ust_loglevel ust_loglevel;
  31
  32 static
  33 void init_object(struct lttng_ust_object_data *data)
  34 {
  35         data->handle = -1;
  36         data->shm_fd = -1;
  37         data->wait_fd = -1;
  38         data->memory_map_size = 0;
  39 }
  40
  41 void ustctl_release_object(int sock, struct lttng_ust_object_data *data)
  42 {
  43         struct ustcomm_ust_msg lum;
  44         struct ustcomm_ust_reply lur;
  45         int ret;
  46
  47         if (data->shm_fd >= 0)
  48                 close(data->shm_fd);
  49         if (data->wait_fd >= 0)
  50                 close(data->wait_fd);
  51         memset(&lum, 0, sizeof(lum));
  52         lum.handle = data->handle;
  53         lum.cmd = LTTNG_UST_RELEASE;
  54         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
  55         assert(!ret);
  56         free(data);
  57 }
  58
  59 /*
  60  * Send registration done packet to the application.
  61  */
  62 int ustctl_register_done(int sock)
  63 {
  64         struct ustcomm_ust_msg lum;
  65         struct ustcomm_ust_reply lur;
  66         int ret;
  67
  68         DBG("Sending register done command to %d", sock);
  69         memset(&lum, 0, sizeof(lum));
  70         lum.handle = LTTNG_UST_ROOT_HANDLE;
  71         lum.cmd = LTTNG_UST_REGISTER_DONE;
  72         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
  73         if (ret)
  74                 return ret;
  75         if (lur.ret_code != USTCOMM_OK) {
  76                 DBG("Return code: %s", ustcomm_get_readable_code(lur.ret_code));
  77                 goto error;
  78         }
  79         return 0;
  80
  81 error:
  82         return -1;
  83 }
  84
  85 /*
  86  * returns session handle.
  87  */
  88 int ustctl_create_session(int sock)
  89 {
  90         struct ustcomm_ust_msg lum;
  91         struct ustcomm_ust_reply lur;
  92         int ret, session_handle;
  93
  94         /* Create session */
  95         memset(&lum, 0, sizeof(lum));
  96         lum.handle = LTTNG_UST_ROOT_HANDLE;
  97         lum.cmd = LTTNG_UST_SESSION;
  98         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
  99         if (ret)
 100                 return ret;
 101         session_handle = lur.ret_val;
 102         DBG("received session handle %u", session_handle);
 103         return session_handle;
 104 }
 105
 106 /* open the metadata global channel */
 107 int ustctl_open_metadata(int sock, int session_handle,
 108                 struct lttng_ust_channel_attr *chops,
 109                 struct lttng_ust_object_data **_metadata_data)
 110 {
 111         struct ustcomm_ust_msg lum;
 112         struct ustcomm_ust_reply lur;
 113         struct lttng_ust_object_data *metadata_data;
 114         int ret;
 115
 116         metadata_data = malloc(sizeof(*metadata_data));
 117         if (!metadata_data)
 118                 return -ENOMEM;
 119         init_object(metadata_data);
 120         /* Create metadata channel */
 121         memset(&lum, 0, sizeof(lum));
 122         lum.handle = session_handle;
 123         lum.cmd = LTTNG_UST_METADATA;
 124         lum.u.channel.overwrite = chops->overwrite;
 125         lum.u.channel.subbuf_size = chops->subbuf_size;
 126         lum.u.channel.num_subbuf = chops->num_subbuf;
 127         lum.u.channel.switch_timer_interval = chops->switch_timer_interval;
 128         lum.u.channel.read_timer_interval = chops->read_timer_interval;
 129         lum.u.channel.output = chops->output;
 130         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 131         if (ret) {
 132                 free(metadata_data);
 133                 return ret;
 134         }
 135         if (lur.ret_code != USTCOMM_OK) {
 136                 free(metadata_data);
 137                 return lur.ret_code;
 138         }
 139         metadata_data->handle = lur.ret_val;
 140         DBG("received metadata handle %u", metadata_data->handle);
 141         metadata_data->memory_map_size = lur.u.channel.memory_map_size;
 142         /* get shm fd */
 143         ret = ustcomm_recv_fd(sock);
 144         if (ret < 0)
 145                 goto error;
 146         metadata_data->shm_fd = ret;
 147         /* get wait fd */
 148         ret = ustcomm_recv_fd(sock);
 149         if (ret < 0)
 150                 goto error;
 151         metadata_data->wait_fd = ret;
 152         *_metadata_data = metadata_data;
 153         return 0;
 154
 155 error:
 156         ustctl_release_object(sock, metadata_data);
 157         return -EINVAL;
 158 }
 159
 160 int ustctl_create_channel(int sock, int session_handle,
 161                 struct lttng_ust_channel_attr *chops,
 162                 struct lttng_ust_object_data **_channel_data)
 163 {
 164         struct ustcomm_ust_msg lum;
 165         struct ustcomm_ust_reply lur;
 166         struct lttng_ust_object_data *channel_data;
 167         int ret;
 168
 169         channel_data = malloc(sizeof(*channel_data));
 170         if (!channel_data)
 171                 return -ENOMEM;
 172         init_object(channel_data);
 173         /* Create metadata channel */
 174         memset(&lum, 0, sizeof(lum));
 175         lum.handle = session_handle;
 176         lum.cmd = LTTNG_UST_CHANNEL;
 177         lum.u.channel.overwrite = chops->overwrite;
 178         lum.u.channel.subbuf_size = chops->subbuf_size;
 179         lum.u.channel.num_subbuf = chops->num_subbuf;
 180         lum.u.channel.switch_timer_interval = chops->switch_timer_interval;
 181         lum.u.channel.read_timer_interval = chops->read_timer_interval;
 182         lum.u.channel.output = chops->output;
 183         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 184         if (ret) {
 185                 free(channel_data);
 186                 return ret;
 187         }
 188         if (lur.ret_code != USTCOMM_OK) {
 189                 free(channel_data);
 190                 return lur.ret_code;
 191         }
 192         channel_data->handle = lur.ret_val;
 193         DBG("received channel handle %u", channel_data->handle);
 194         channel_data->memory_map_size = lur.u.channel.memory_map_size;
 195         /* get shm fd */
 196         ret = ustcomm_recv_fd(sock);
 197         if (ret < 0)
 198                 goto error;
 199         channel_data->shm_fd = ret;
 200         /* get wait fd */
 201         ret = ustcomm_recv_fd(sock);
 202         if (ret < 0)
 203                 goto error;
 204         channel_data->wait_fd = ret;
 205         *_channel_data = channel_data;
 206         return 0;
 207
 208 error:
 209         ustctl_release_object(sock, channel_data);
 210         return -EINVAL;
 211 }
 212
 213 /*
 214  * Return -ENOENT if no more stream is available for creation.
 215  * Return 0 on success.
 216  * Return negative error value on error.
 217  */
 218 int ustctl_create_stream(int sock, struct lttng_ust_object_data *channel_data,
 219                 struct lttng_ust_object_data **_stream_data)
 220 {
 221         struct ustcomm_ust_msg lum;
 222         struct ustcomm_ust_reply lur;
 223         struct lttng_ust_object_data *stream_data;
 224         int ret, fd;
 225
 226         stream_data = malloc(sizeof(*stream_data));
 227         if (!stream_data)
 228                 return -ENOMEM;
 229         init_object(stream_data);
 230         memset(&lum, 0, sizeof(lum));
 231         lum.handle = channel_data->handle;
 232         lum.cmd = LTTNG_UST_STREAM;
 233         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 234         if (ret) {
 235                 free(stream_data);
 236                 return ret;
 237         }
 238         if (lur.ret_code != USTCOMM_OK) {
 239                 free(stream_data);
 240                 return lur.ret_code;
 241         }
 242
 243         stream_data->handle = lur.ret_val;
 244         DBG("received stream handle %u", stream_data->handle);
 245         stream_data->memory_map_size = lur.u.stream.memory_map_size;
 246         /* get shm fd */
 247         fd = ustcomm_recv_fd(sock);
 248         if (fd < 0)
 249                 goto error;
 250         stream_data->shm_fd = fd;
 251         /* get wait fd */
 252         fd = ustcomm_recv_fd(sock);
 253         if (fd < 0)
 254                 goto error;
 255         stream_data->wait_fd = fd;
 256         *_stream_data = stream_data;
 257         return ret;
 258
 259 error:
 260         ustctl_release_object(sock, stream_data);
 261         return -EINVAL;
 262 }
 263
 264 int ustctl_create_event(int sock, struct lttng_ust_event *ev,
 265                 struct lttng_ust_object_data *channel_data,
 266                 struct lttng_ust_object_data **_event_data)
 267 {
 268         struct ustcomm_ust_msg lum;
 269         struct ustcomm_ust_reply lur;
 270         struct lttng_ust_object_data *event_data;
 271         int ret;
 272
 273         event_data = malloc(sizeof(*event_data));
 274         if (!event_data)
 275                 return -ENOMEM;
 276         init_object(event_data);
 277         memset(&lum, 0, sizeof(lum));
 278         lum.handle = channel_data->handle;
 279         lum.cmd = LTTNG_UST_EVENT;
 280         strncpy(lum.u.event.name, ev->name,
 281                 LTTNG_UST_SYM_NAME_LEN);
 282         lum.u.event.instrumentation = ev->instrumentation;
 283         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 284         if (ret) {
 285                 free(event_data);
 286                 return ret;
 287         }
 288         event_data->handle = lur.ret_val;
 289         DBG("received event handle %u", event_data->handle);
 290         *_event_data = event_data;
 291         return 0;
 292 }
 293
 294 int ustctl_add_context(int sock, struct lttng_ust_context *ctx,
 295                 struct lttng_ust_object_data *obj_data,
 296                 struct lttng_ust_object_data **_context_data)
 297 {
 298         struct ustcomm_ust_msg lum;
 299         struct ustcomm_ust_reply lur;
 300         struct lttng_ust_object_data *context_data;
 301         int ret;
 302
 303         context_data = malloc(sizeof(*context_data));
 304         if (!context_data)
 305                 return -ENOMEM;
 306         init_object(context_data);
 307         memset(&lum, 0, sizeof(lum));
 308         lum.handle = obj_data->handle;
 309         lum.cmd = LTTNG_UST_CONTEXT;
 310         lum.u.context.ctx = ctx->ctx;
 311         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 312         if (ret) {
 313                 free(context_data);
 314                 return ret;
 315         }
 316         context_data->handle = lur.ret_val;
 317         DBG("received context handle %u", context_data->handle);
 318         *_context_data = context_data;
 319         return ret;
 320 }
 321
 322 /* Enable event, channel and session ioctl */
 323 int ustctl_enable(int sock, struct lttng_ust_object_data *object)
 324 {
 325         struct ustcomm_ust_msg lum;
 326         struct ustcomm_ust_reply lur;
 327         int ret;
 328
 329         memset(&lum, 0, sizeof(lum));
 330         lum.handle = object->handle;
 331         lum.cmd = LTTNG_UST_ENABLE;
 332         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 333         if (ret)
 334                 return ret;
 335         DBG("enabled handle %u", object->handle);
 336         return 0;
 337 }
 338
 339 /* Disable event, channel and session ioctl */
 340 int ustctl_disable(int sock, struct lttng_ust_object_data *object)
 341 {
 342         struct ustcomm_ust_msg lum;
 343         struct ustcomm_ust_reply lur;
 344         int ret;
 345
 346         memset(&lum, 0, sizeof(lum));
 347         lum.handle = object->handle;
 348         lum.cmd = LTTNG_UST_DISABLE;
 349         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 350         if (ret)
 351                 return ret;
 352         DBG("disable handle %u", object->handle);
 353         return 0;
 354 }
 355
 356 int ustctl_start_session(int sock, int handle)
 357 {
 358         struct lttng_ust_object_data obj;
 359
 360         obj.handle = handle;
 361         return ustctl_enable(sock, &obj);
 362 }
 363
 364 int ustctl_stop_session(int sock, int handle)
 365 {
 366         struct lttng_ust_object_data obj;
 367
 368         obj.handle = handle;
 369         return ustctl_disable(sock, &obj);
 370 }
 371
 372
 373 int ustctl_tracepoint_list(int sock)
 374 {
 375         return -ENOSYS; /* not implemented */
 376 }
 377
 378 int ustctl_tracer_version(int sock, struct lttng_ust_tracer_version *v)
 379 {
 380         struct ustcomm_ust_msg lum;
 381         struct ustcomm_ust_reply lur;
 382         int ret;
 383
 384         memset(&lum, 0, sizeof(lum));
 385         lum.handle = LTTNG_UST_ROOT_HANDLE;
 386         lum.cmd = LTTNG_UST_TRACER_VERSION;
 387         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 388         if (ret)
 389                 return ret;
 390         memcpy(v, &lur.u.version, sizeof(*v));
 391         DBG("received tracer version");
 392         return 0;
 393 }
 394
 395 int ustctl_wait_quiescent(int sock)
 396 {
 397         struct ustcomm_ust_msg lum;
 398         struct ustcomm_ust_reply lur;
 399         int ret;
 400
 401         memset(&lum, 0, sizeof(lum));
 402         lum.handle = LTTNG_UST_ROOT_HANDLE;
 403         lum.cmd = LTTNG_UST_WAIT_QUIESCENT;
 404         ret = ustcomm_send_app_cmd(sock, &lum, &lur);
 405         if (ret)
 406                 return ret;
 407         DBG("waited for quiescent state");
 408         return 0;
 409 }
 410
 411 int ustctl_calibrate(int sock, struct lttng_ust_calibrate *calibrate)
 412 {
 413         return -ENOSYS;
 414 }
 415
 416 /* Buffer operations */
 417
 418 /* Map channel shm into process memory */
 419 struct lttng_ust_shm_handle *ustctl_map_channel(struct lttng_ust_object_data *chan_data)
 420 {
 421         struct lttng_ust_shm_handle *handle;
 422         struct channel *chan;
 423         size_t chan_size;
 424         struct lttng_ust_lib_ring_buffer_config *config;
 425
 426         handle = channel_handle_create(chan_data->shm_fd,
 427                 chan_data->wait_fd,
 428                 chan_data->memory_map_size);
 429         if (!handle) {
 430                 ERR("create handle error");
 431                 return NULL;
 432         }
 433         /*
 434          * Set to -1 because the lttng_ust_shm_handle destruction will take care
 435          * of closing shm_fd and wait_fd.
 436          */
 437         chan_data->shm_fd = -1;
 438         chan_data->wait_fd = -1;
 439
 440         /*
 441          * TODO: add consistency checks to be resilient if the
 442          * application try to feed us with incoherent channel structure
 443          * values.
 444          */
 445         chan = shmp(handle, handle->chan);
 446         /* chan is object 0. This is hardcoded. */
 447         chan_size = handle->table->objects[0].allocated_len;
 448         handle->shadow_chan = malloc(chan_size);
 449         if (!handle->shadow_chan) {
 450                 channel_destroy(chan, handle, 1);
 451                 return NULL;
 452         }
 453         memcpy(handle->shadow_chan, chan, chan_size);
 454         /*
 455          * The callback pointers in the producer are invalid in the
 456          * consumer. We need to look them up here.
 457          */
 458         config = &handle->shadow_chan->backend.config;
 459         switch (config->client_type) {
 460         case LTTNG_CLIENT_METADATA:
 461                 memcpy(&config->cb, lttng_client_callbacks_metadata,
 462                         sizeof(config->cb));
 463                 break;
 464         case LTTNG_CLIENT_DISCARD:
 465                 memcpy(&config->cb, lttng_client_callbacks_discard,
 466                         sizeof(config->cb));
 467                 break;
 468         case LTTNG_CLIENT_OVERWRITE:
 469                 memcpy(&config->cb, lttng_client_callbacks_overwrite,
 470                         sizeof(config->cb));
 471                 break;
 472         default:
 473                 ERR("Unknown client type %d", config->client_type);
 474                 channel_destroy(chan, handle, 1);
 475                 return NULL;
 476         }
 477         return handle;
 478 }
 479
 480 /* Add stream to channel shm and map its shm into process memory */
 481 int ustctl_add_stream(struct lttng_ust_shm_handle *handle,
 482                 struct lttng_ust_object_data *stream_data)
 483 {
 484         int ret;
 485
 486         if (!stream_data->handle)
 487                 return -ENOENT;
 488         /* map stream */
 489         ret = channel_handle_add_stream(handle,
 490                 stream_data->shm_fd,
 491                 stream_data->wait_fd,
 492                 stream_data->memory_map_size);
 493         if (ret) {
 494                 ERR("add stream error\n");
 495                 return ret;
 496         }
 497         /*
 498          * Set to -1 because the lttng_ust_shm_handle destruction will take care
 499          * of closing shm_fd and wait_fd.
 500          */
 501         stream_data->shm_fd = -1;
 502         stream_data->wait_fd = -1;
 503         return 0;
 504 }
 505
 506 void ustctl_unmap_channel(struct lttng_ust_shm_handle *handle)
 507 {
 508         struct channel *chan;
 509
 510         chan = shmp(handle, handle->chan);
 511         channel_destroy(chan, handle, 1);
 512 }
 513
 514 struct lttng_ust_lib_ring_buffer *ustctl_open_stream_read(struct lttng_ust_shm_handle *handle,
 515         int cpu)
 516 {
 517         struct channel *chan = handle->shadow_chan;
 518         int shm_fd, wait_fd;
 519         uint64_t memory_map_size;
 520         struct lttng_ust_lib_ring_buffer *buf;
 521         int ret;
 522
 523         buf = channel_get_ring_buffer(&chan->backend.config,
 524                 chan, cpu, handle, &shm_fd, &wait_fd, &memory_map_size);
 525         if (!buf)
 526                 return NULL;
 527         ret = lib_ring_buffer_open_read(buf, handle, 1);
 528         if (ret)
 529                 return NULL;
 530         return buf;
 531 }
 532
 533 void ustctl_close_stream_read(struct lttng_ust_shm_handle *handle,
 534                 struct lttng_ust_lib_ring_buffer *buf)
 535 {
 536         lib_ring_buffer_release_read(buf, handle, 1);
 537 }
 538
 539 /* For mmap mode, readable without "get" operation */
 540
 541 void *ustctl_get_mmap_base(struct lttng_ust_shm_handle *handle,
 542                 struct lttng_ust_lib_ring_buffer *buf)
 543 {
 544         return shmp(handle, buf->backend.memory_map);
 545 }
 546
 547 /* returns the length to mmap. */
 548 int ustctl_get_mmap_len(struct lttng_ust_shm_handle *handle,
 549                 struct lttng_ust_lib_ring_buffer *buf,
 550                 unsigned long *len)
 551 {
 552         unsigned long mmap_buf_len;
 553         struct channel *chan = handle->shadow_chan;
 554
 555         if (chan->backend.config.output != RING_BUFFER_MMAP)
 556                 return -EINVAL;
 557         mmap_buf_len = chan->backend.buf_size;
 558         if (chan->backend.extra_reader_sb)
 559                 mmap_buf_len += chan->backend.subbuf_size;
 560         if (mmap_buf_len > INT_MAX)
 561                 return -EFBIG;
 562         *len = mmap_buf_len;
 563         return 0;
 564 }
 565
 566 /* returns the maximum size for sub-buffers. */
 567 int ustctl_get_max_subbuf_size(struct lttng_ust_shm_handle *handle,
 568                 struct lttng_ust_lib_ring_buffer *buf,
 569                 unsigned long *len)
 570 {
 571         struct channel *chan = handle->shadow_chan;
 572
 573         *len = chan->backend.subbuf_size;
 574         return 0;
 575 }
 576
 577 /*
 578  * For mmap mode, operate on the current packet (between get/put or
 579  * get_next/put_next).
 580  */
 581
 582 /* returns the offset of the subbuffer belonging to the mmap reader. */
 583 int ustctl_get_mmap_read_offset(struct lttng_ust_shm_handle *handle,
 584                 struct lttng_ust_lib_ring_buffer *buf, unsigned long *off)
 585 {
 586         struct channel *chan = handle->shadow_chan;
 587         unsigned long sb_bindex;
 588
 589         if (chan->backend.config.output != RING_BUFFER_MMAP)
 590                 return -EINVAL;
 591         sb_bindex = subbuffer_id_get_index(&chan->backend.config,
 592                                            buf->backend.buf_rsb.id);
 593         *off = shmp(handle, shmp_index(handle, buf->backend.array, sb_bindex)->shmp)->mmap_offset;
 594         return 0;
 595 }
 596
 597 /* returns the size of the current sub-buffer, without padding (for mmap). */
 598 int ustctl_get_subbuf_size(struct lttng_ust_shm_handle *handle,
 599                 struct lttng_ust_lib_ring_buffer *buf, unsigned long *len)
 600 {
 601         struct channel *chan = handle->shadow_chan;
 602
 603         *len = lib_ring_buffer_get_read_data_size(&chan->backend.config, buf,
 604                 handle);
 605         return 0;
 606 }
 607
 608 /* returns the size of the current sub-buffer, without padding (for mmap). */
 609 int ustctl_get_padded_subbuf_size(struct lttng_ust_shm_handle *handle,
 610                 struct lttng_ust_lib_ring_buffer *buf, unsigned long *len)
 611 {
 612         struct channel *chan = handle->shadow_chan;
 613
 614         *len = lib_ring_buffer_get_read_data_size(&chan->backend.config, buf,
 615                 handle);
 616         *len = PAGE_ALIGN(*len);
 617         return 0;
 618 }
 619
 620 /* Get exclusive read access to the next sub-buffer that can be read. */
 621 int ustctl_get_next_subbuf(struct lttng_ust_shm_handle *handle,
 622                 struct lttng_ust_lib_ring_buffer *buf)
 623 {
 624         return lib_ring_buffer_get_next_subbuf(buf, handle);
 625 }
 626
 627
 628 /* Release exclusive sub-buffer access, move consumer forward. */
 629 int ustctl_put_next_subbuf(struct lttng_ust_shm_handle *handle,
 630                 struct lttng_ust_lib_ring_buffer *buf)
 631 {
 632         lib_ring_buffer_put_next_subbuf(buf, handle);
 633         return 0;
 634 }
 635
 636 /* snapshot */
 637
 638 /* Get a snapshot of the current ring buffer producer and consumer positions */
 639 int ustctl_snapshot(struct lttng_ust_shm_handle *handle,
 640                 struct lttng_ust_lib_ring_buffer *buf)
 641 {
 642         return lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 643                         &buf->prod_snapshot, handle);
 644 }
 645
 646 /* Get the consumer position (iteration start) */
 647 int ustctl_snapshot_get_consumed(struct lttng_ust_shm_handle *handle,
 648                 struct lttng_ust_lib_ring_buffer *buf, unsigned long *pos)
 649 {
 650         *pos = buf->cons_snapshot;
 651         return 0;
 652 }
 653
 654 /* Get the producer position (iteration end) */
 655 int ustctl_snapshot_get_produced(struct lttng_ust_shm_handle *handle,
 656                 struct lttng_ust_lib_ring_buffer *buf, unsigned long *pos)
 657 {
 658         *pos = buf->prod_snapshot;
 659         return 0;
 660 }
 661
 662 /* Get exclusive read access to the specified sub-buffer position */
 663 int ustctl_get_subbuf(struct lttng_ust_shm_handle *handle,
 664                 struct lttng_ust_lib_ring_buffer *buf, unsigned long *pos)
 665 {
 666         return lib_ring_buffer_get_subbuf(buf, *pos, handle);
 667 }
 668
 669 /* Release exclusive sub-buffer access */
 670 int ustctl_put_subbuf(struct lttng_ust_shm_handle *handle,
 671                 struct lttng_ust_lib_ring_buffer *buf)
 672 {
 673         lib_ring_buffer_put_subbuf(buf, handle);
 674         return 0;
 675 }
 676
 677 void ustctl_flush_buffer(struct lttng_ust_shm_handle *handle,
 678                 struct lttng_ust_lib_ring_buffer *buf,
 679                 int producer_active)
 680 {
 681         lib_ring_buffer_switch_slow(buf,
 682                 producer_active ? SWITCH_ACTIVE : SWITCH_FLUSH,
 683                 handle);
 684 }