src/common/kernel-ctl/kernel-ctl.c

   1 /*
   2  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
   3  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *               2016 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License, version 2 only,
   8  * as published by the Free Software Foundation.
   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 along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20 #define _LGPL_SOURCE
  21 #define __USE_LINUX_IOCTL_DEFS
  22 #include <sys/ioctl.h>
  23 #include <string.h>
  24 #include <common/align.h>
  25 #include <errno.h>
  26 #include <stdarg.h>
  27 #include <assert.h>
  28
  29 #include "kernel-ctl.h"
  30 #include "kernel-ioctl.h"
  31
  32 #define LTTNG_IOCTL_CHECK(fildes, request, ...) ({      \
  33         int ret = ioctl(fildes, request, ##__VA_ARGS__);\
  34         assert(ret <= 0);                               \
  35         !ret ? 0 : -errno;                              \
  36 })
  37
  38 #define LTTNG_IOCTL_NO_CHECK(fildes, request, ...) ({   \
  39         int ret = ioctl(fildes, request, ##__VA_ARGS__);\
  40         ret >= 0 ? ret : -errno;                        \
  41 })
  42
  43 /*
  44  * This flag indicates which version of the kernel ABI to use. The old
  45  * ABI (namespace _old) does not support a 32-bit user-space when the
  46  * kernel is 64-bit. The old ABI is kept here for compatibility but is
  47  * deprecated and will be removed eventually.
  48  */
  49 static int lttng_kernel_use_old_abi = -1;
  50
  51 /*
  52  * Execute the new or old ioctl depending on the ABI version.
  53  * If the ABI version is not determined yet (lttng_kernel_use_old_abi = -1),
  54  * this function tests if the new ABI is available and otherwise fallbacks
  55  * on the old one.
  56  * This function takes the fd on which the ioctl must be executed and the old
  57  * and new request codes.
  58  * It returns the return value of the ioctl executed.
  59  */
  60 static inline int compat_ioctl_no_arg(int fd, unsigned long oldname,
  61                 unsigned long newname)
  62 {
  63         int ret;
  64
  65         if (lttng_kernel_use_old_abi == -1) {
  66                 ret = LTTNG_IOCTL_NO_CHECK(fd, newname);
  67                 if (!ret) {
  68                         lttng_kernel_use_old_abi = 0;
  69                         goto end;
  70                 }
  71                 lttng_kernel_use_old_abi = 1;
  72         }
  73         if (lttng_kernel_use_old_abi) {
  74                 ret = LTTNG_IOCTL_NO_CHECK(fd, oldname);
  75         } else {
  76                 ret = LTTNG_IOCTL_NO_CHECK(fd, newname);
  77         }
  78
  79 end:
  80         return ret;
  81 }
  82
  83 int kernctl_create_session(int fd)
  84 {
  85         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_SESSION,
  86                         LTTNG_KERNEL_SESSION);
  87 }
  88
  89 /* open the metadata global channel */
  90 int kernctl_open_metadata(int fd, struct lttng_channel_attr *chops)
  91 {
  92         struct lttng_kernel_old_channel old_channel;
  93         struct lttng_kernel_channel channel;
  94
  95         if (lttng_kernel_use_old_abi) {
  96                 old_channel.overwrite = chops->overwrite;
  97                 old_channel.subbuf_size = chops->subbuf_size;
  98                 old_channel.num_subbuf = chops->num_subbuf;
  99                 old_channel.switch_timer_interval = chops->switch_timer_interval;
 100                 old_channel.read_timer_interval = chops->read_timer_interval;
 101                 old_channel.output = chops->output;
 102
 103                 memset(old_channel.padding, 0, sizeof(old_channel.padding));
 104                 /*
 105                  * The new channel padding is smaller than the old ABI so we use the
 106                  * new ABI padding size for the memcpy.
 107                  */
 108                 memcpy(old_channel.padding, chops->padding, sizeof(chops->padding));
 109
 110                 return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_OLD_METADATA,
 111                                 &old_channel);
 112         }
 113
 114         channel.overwrite = chops->overwrite;
 115         channel.subbuf_size = chops->subbuf_size;
 116         channel.num_subbuf = chops->num_subbuf;
 117         channel.switch_timer_interval = chops->switch_timer_interval;
 118         channel.read_timer_interval = chops->read_timer_interval;
 119         channel.output = chops->output;
 120         memcpy(channel.padding, chops->padding, sizeof(chops->padding));
 121
 122         return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_METADATA, &channel);
 123 }
 124
 125 int kernctl_create_channel(int fd, struct lttng_channel_attr *chops)
 126 {
 127         struct lttng_kernel_channel channel;
 128
 129         memset(&channel, 0, sizeof(channel));
 130         if (lttng_kernel_use_old_abi) {
 131                 struct lttng_kernel_old_channel old_channel;
 132
 133                 old_channel.overwrite = chops->overwrite;
 134                 old_channel.subbuf_size = chops->subbuf_size;
 135                 old_channel.num_subbuf = chops->num_subbuf;
 136                 old_channel.switch_timer_interval = chops->switch_timer_interval;
 137                 old_channel.read_timer_interval = chops->read_timer_interval;
 138                 old_channel.output = chops->output;
 139
 140                 memset(old_channel.padding, 0, sizeof(old_channel.padding));
 141                 /*
 142                  * The new channel padding is smaller than the old ABI so we use the
 143                  * new ABI padding size for the memcpy.
 144                  */
 145                 memcpy(old_channel.padding, chops->padding, sizeof(chops->padding));
 146
 147                 return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_OLD_CHANNEL,
 148                                 &old_channel);
 149         }
 150
 151         channel.overwrite = chops->overwrite;
 152         channel.subbuf_size = chops->subbuf_size;
 153         channel.num_subbuf = chops->num_subbuf;
 154         channel.switch_timer_interval = chops->switch_timer_interval;
 155         channel.read_timer_interval = chops->read_timer_interval;
 156         channel.output = chops->output;
 157         memcpy(channel.padding, chops->padding, sizeof(chops->padding));
 158
 159         return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_CHANNEL, &channel);
 160 }
 161
 162 int kernctl_syscall_mask(int fd, char **syscall_mask, uint32_t *nr_bits)
 163 {
 164         struct lttng_kernel_syscall_mask kmask_len, *kmask = NULL;
 165         size_t array_alloc_len;
 166         char *new_mask;
 167         int ret = 0;
 168
 169         if (!syscall_mask) {
 170                 ret = -1;
 171                 goto end;
 172         }
 173
 174         if (!nr_bits) {
 175                 ret = -1;
 176                 goto end;
 177         }
 178
 179         kmask_len.len = 0;
 180         ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_SYSCALL_MASK, &kmask_len);
 181         if (ret) {
 182                 goto end;
 183         }
 184
 185         array_alloc_len = ALIGN(kmask_len.len, 8) >> 3;
 186
 187         kmask = zmalloc(sizeof(*kmask) + array_alloc_len);
 188         if (!kmask) {
 189                 ret = -1;
 190                 goto end;
 191         }
 192
 193         kmask->len = kmask_len.len;
 194         ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_SYSCALL_MASK, kmask);
 195         if (ret) {
 196                 goto end;
 197         }
 198
 199         new_mask = realloc(*syscall_mask, array_alloc_len);
 200         if (!new_mask) {
 201                 ret = -1;
 202                 goto end;
 203         }
 204         memcpy(new_mask, kmask->mask, array_alloc_len);
 205         *syscall_mask = new_mask;
 206         *nr_bits = kmask->len;
 207
 208 end:
 209         free(kmask);
 210         return ret;
 211 }
 212
 213 int kernctl_track_pid(int fd, int pid)
 214 {
 215         return LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_SESSION_TRACK_PID, pid);
 216 }
 217
 218 int kernctl_untrack_pid(int fd, int pid)
 219 {
 220         return LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_SESSION_UNTRACK_PID, pid);
 221 }
 222
 223 int kernctl_list_tracker_pids(int fd)
 224 {
 225         return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_SESSION_LIST_TRACKER_PIDS);
 226 }
 227
 228 int kernctl_session_regenerate_metadata(int fd)
 229 {
 230         return LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_SESSION_METADATA_REGEN);
 231 }
 232
 233 int kernctl_create_stream(int fd)
 234 {
 235         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_STREAM,
 236                         LTTNG_KERNEL_STREAM);
 237 }
 238
 239 int kernctl_create_event(int fd, struct lttng_kernel_event *ev)
 240 {
 241         if (lttng_kernel_use_old_abi) {
 242                 struct lttng_kernel_old_event old_event;
 243
 244                 memcpy(old_event.name, ev->name, sizeof(old_event.name));
 245                 old_event.instrumentation = ev->instrumentation;
 246                 switch (ev->instrumentation) {
 247                 case LTTNG_KERNEL_KPROBE:
 248                         old_event.u.kprobe.addr = ev->u.kprobe.addr;
 249                         old_event.u.kprobe.offset = ev->u.kprobe.offset;
 250                         memcpy(old_event.u.kprobe.symbol_name,
 251                                 ev->u.kprobe.symbol_name,
 252                                 sizeof(old_event.u.kprobe.symbol_name));
 253                         break;
 254                 case LTTNG_KERNEL_KRETPROBE:
 255                         old_event.u.kretprobe.addr = ev->u.kretprobe.addr;
 256                         old_event.u.kretprobe.offset = ev->u.kretprobe.offset;
 257                         memcpy(old_event.u.kretprobe.symbol_name,
 258                                 ev->u.kretprobe.symbol_name,
 259                                 sizeof(old_event.u.kretprobe.symbol_name));
 260                         break;
 261                 case LTTNG_KERNEL_FUNCTION:
 262                         memcpy(old_event.u.ftrace.symbol_name,
 263                                         ev->u.ftrace.symbol_name,
 264                                         sizeof(old_event.u.ftrace.symbol_name));
 265                         break;
 266                 default:
 267                         break;
 268                 }
 269
 270                 return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_OLD_EVENT,
 271                                 &old_event);
 272         }
 273         return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_EVENT, ev);
 274 }
 275
 276 int kernctl_add_context(int fd, struct lttng_kernel_context *ctx)
 277 {
 278         if (lttng_kernel_use_old_abi) {
 279                 struct lttng_kernel_old_context old_ctx;
 280
 281                 old_ctx.ctx = ctx->ctx;
 282                 /* only type that uses the union */
 283                 if (ctx->ctx == LTTNG_KERNEL_CONTEXT_PERF_CPU_COUNTER) {
 284                         old_ctx.u.perf_counter.type =
 285                                 ctx->u.perf_counter.type;
 286                         old_ctx.u.perf_counter.config =
 287                                 ctx->u.perf_counter.config;
 288                         memcpy(old_ctx.u.perf_counter.name,
 289                                 ctx->u.perf_counter.name,
 290                                 sizeof(old_ctx.u.perf_counter.name));
 291                 }
 292                 return LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_OLD_CONTEXT, &old_ctx);
 293         }
 294         return LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_CONTEXT, ctx);
 295 }
 296
 297
 298 /* Enable event, channel and session LTTNG_IOCTL_CHECK */
 299 int kernctl_enable(int fd)
 300 {
 301         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_ENABLE,
 302                         LTTNG_KERNEL_ENABLE);
 303 }
 304
 305 /* Disable event, channel and session LTTNG_IOCTL_CHECK */
 306 int kernctl_disable(int fd)
 307 {
 308         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_DISABLE,
 309                         LTTNG_KERNEL_DISABLE);
 310 }
 311
 312 int kernctl_start_session(int fd)
 313 {
 314         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_SESSION_START,
 315                         LTTNG_KERNEL_SESSION_START);
 316 }
 317
 318 int kernctl_stop_session(int fd)
 319 {
 320         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_SESSION_STOP,
 321                         LTTNG_KERNEL_SESSION_STOP);
 322 }
 323
 324 int kernctl_filter(int fd, struct lttng_filter_bytecode *filter)
 325 {
 326         struct lttng_kernel_filter_bytecode *kb;
 327         uint32_t len;
 328         int ret;
 329
 330         /* Translate bytecode to kernel bytecode */
 331         kb = zmalloc(sizeof(*kb) + filter->len);
 332         if (!kb)
 333                 return -ENOMEM;
 334         kb->len = len = filter->len;
 335         kb->reloc_offset = filter->reloc_table_offset;
 336         kb->seqnum = filter->seqnum;
 337         memcpy(kb->data, filter->data, len);
 338         ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_FILTER, kb);
 339         free(kb);
 340         return ret;
 341 }
 342
 343 int kernctl_tracepoint_list(int fd)
 344 {
 345         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_TRACEPOINT_LIST,
 346                         LTTNG_KERNEL_TRACEPOINT_LIST);
 347 }
 348
 349 int kernctl_syscall_list(int fd)
 350 {
 351         return LTTNG_IOCTL_NO_CHECK(fd, LTTNG_KERNEL_SYSCALL_LIST);
 352 }
 353
 354 int kernctl_tracer_version(int fd, struct lttng_kernel_tracer_version *v)
 355 {
 356         int ret;
 357
 358         if (lttng_kernel_use_old_abi == -1) {
 359                 ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_TRACER_VERSION, v);
 360                 if (!ret) {
 361                         lttng_kernel_use_old_abi = 0;
 362                         goto end;
 363                 }
 364                 lttng_kernel_use_old_abi = 1;
 365         }
 366         if (lttng_kernel_use_old_abi) {
 367                 struct lttng_kernel_old_tracer_version old_v;
 368
 369                 ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_OLD_TRACER_VERSION, &old_v);
 370                 if (ret) {
 371                         goto end;
 372                 }
 373                 v->major = old_v.major;
 374                 v->minor = old_v.minor;
 375                 v->patchlevel = old_v.patchlevel;
 376         } else {
 377                 ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_TRACER_VERSION, v);
 378         }
 379
 380 end:
 381         return ret;
 382 }
 383
 384 int kernctl_tracer_abi_version(int fd,
 385                 struct lttng_kernel_tracer_abi_version *v)
 386 {
 387         return LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_TRACER_ABI_VERSION, v);
 388 }
 389
 390 int kernctl_wait_quiescent(int fd)
 391 {
 392         return compat_ioctl_no_arg(fd, LTTNG_KERNEL_OLD_WAIT_QUIESCENT,
 393                         LTTNG_KERNEL_WAIT_QUIESCENT);
 394 }
 395
 396 int kernctl_calibrate(int fd, struct lttng_kernel_calibrate *calibrate)
 397 {
 398         int ret;
 399
 400         if (lttng_kernel_use_old_abi == -1) {
 401                 ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_CALIBRATE, calibrate);
 402                 if (!ret) {
 403                         lttng_kernel_use_old_abi = 0;
 404                         goto end;
 405                 }
 406                 lttng_kernel_use_old_abi = 1;
 407         }
 408         if (lttng_kernel_use_old_abi) {
 409                 struct lttng_kernel_old_calibrate old_calibrate;
 410
 411                 old_calibrate.type = calibrate->type;
 412                 ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_OLD_CALIBRATE,
 413                                 &old_calibrate);
 414                 if (ret) {
 415                         goto end;
 416                 }
 417                 calibrate->type = old_calibrate.type;
 418         } else {
 419                 ret = LTTNG_IOCTL_CHECK(fd, LTTNG_KERNEL_CALIBRATE, calibrate);
 420         }
 421
 422 end:
 423         return ret;
 424 }
 425
 426
 427 int kernctl_buffer_flush(int fd)
 428 {
 429         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_FLUSH);
 430 }
 431
 432 /* returns the version of the metadata. */
 433 int kernctl_get_metadata_version(int fd, uint64_t *version)
 434 {
 435         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_METADATA_VERSION, version);
 436 }
 437
 438
 439 /* Buffer operations */
 440
 441 /* For mmap mode, readable without "get" operation */
 442
 443 /* returns the length to mmap. */
 444 int kernctl_get_mmap_len(int fd, unsigned long *len)
 445 {
 446         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_MMAP_LEN, len);
 447 }
 448
 449 /* returns the maximum size for sub-buffers. */
 450 int kernctl_get_max_subbuf_size(int fd, unsigned long *len)
 451 {
 452         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_MAX_SUBBUF_SIZE, len);
 453 }
 454
 455 /*
 456  * For mmap mode, operate on the current packet (between get/put or
 457  * get_next/put_next).
 458  */
 459
 460 /* returns the offset of the subbuffer belonging to the mmap reader. */
 461 int kernctl_get_mmap_read_offset(int fd, unsigned long *off)
 462 {
 463         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_MMAP_READ_OFFSET, off);
 464 }
 465
 466 /* returns the size of the current sub-buffer, without padding (for mmap). */
 467 int kernctl_get_subbuf_size(int fd, unsigned long *len)
 468 {
 469         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_SUBBUF_SIZE, len);
 470 }
 471
 472 /* returns the size of the current sub-buffer, without padding (for mmap). */
 473 int kernctl_get_padded_subbuf_size(int fd, unsigned long *len)
 474 {
 475         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_PADDED_SUBBUF_SIZE, len);
 476 }
 477
 478 /* Get exclusive read access to the next sub-buffer that can be read. */
 479 int kernctl_get_next_subbuf(int fd)
 480 {
 481         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_NEXT_SUBBUF);
 482 }
 483
 484
 485 /* Release exclusive sub-buffer access, move consumer forward. */
 486 int kernctl_put_next_subbuf(int fd)
 487 {
 488         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_PUT_NEXT_SUBBUF);
 489 }
 490
 491 /* snapshot */
 492
 493 /* Get a snapshot of the current ring buffer producer and consumer positions */
 494 int kernctl_snapshot(int fd)
 495 {
 496         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_SNAPSHOT);
 497 }
 498
 499 /* Get the consumer position (iteration start) */
 500 int kernctl_snapshot_get_consumed(int fd, unsigned long *pos)
 501 {
 502         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_SNAPSHOT_GET_CONSUMED, pos);
 503 }
 504
 505 /* Get the producer position (iteration end) */
 506 int kernctl_snapshot_get_produced(int fd, unsigned long *pos)
 507 {
 508         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_SNAPSHOT_GET_PRODUCED, pos);
 509 }
 510
 511 /* Get exclusive read access to the specified sub-buffer position */
 512 int kernctl_get_subbuf(int fd, unsigned long *len)
 513 {
 514         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_SUBBUF, len);
 515 }
 516
 517 /* Release exclusive sub-buffer access */
 518 int kernctl_put_subbuf(int fd)
 519 {
 520         return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_PUT_SUBBUF);
 521 }
 522
 523 /* Returns the timestamp begin of the current sub-buffer. */
 524 int kernctl_get_timestamp_begin(int fd, uint64_t *timestamp_begin)
 525 {
 526         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_TIMESTAMP_BEGIN,
 527                         timestamp_begin);
 528 }
 529
 530 /* Returns the timestamp end of the current sub-buffer. */
 531 int kernctl_get_timestamp_end(int fd, uint64_t *timestamp_end)
 532 {
 533         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_TIMESTAMP_END,
 534                         timestamp_end);
 535 }
 536
 537 /* Returns the number of discarded events in the current sub-buffer. */
 538 int kernctl_get_events_discarded(int fd, uint64_t *events_discarded)
 539 {
 540         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_EVENTS_DISCARDED,
 541                         events_discarded);
 542 }
 543
 544 /* Returns the content size in the current sub-buffer. */
 545 int kernctl_get_content_size(int fd, uint64_t *content_size)
 546 {
 547         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_CONTENT_SIZE,
 548                         content_size);
 549 }
 550
 551 /* Returns the packet size in the current sub-buffer. */
 552 int kernctl_get_packet_size(int fd, uint64_t *packet_size)
 553 {
 554         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_PACKET_SIZE,
 555                         packet_size);
 556 }
 557
 558 /* Returns the stream id of the current sub-buffer. */
 559 int kernctl_get_stream_id(int fd, uint64_t *stream_id)
 560 {
 561         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_STREAM_ID,
 562                         stream_id);
 563 }
 564
 565 /* Returns the current timestamp. */
 566 int kernctl_get_current_timestamp(int fd, uint64_t *ts)
 567 {
 568         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_CURRENT_TIMESTAMP,
 569                         ts);
 570 }
 571
 572 /* Returns the packet sequence number of the current sub-buffer. */
 573 int kernctl_get_sequence_number(int fd, uint64_t *seq)
 574 {
 575         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_GET_SEQ_NUM, seq);
 576 }
 577
 578 /* Returns the stream instance id. */
 579 int kernctl_get_instance_id(int fd, uint64_t *id)
 580 {
 581         return LTTNG_IOCTL_CHECK(fd, LTTNG_RING_BUFFER_INSTANCE_ID, id);
 582 }