src/bin/lttng/commands/enable_channels.cpp

   1 /*
   2  * Copyright (C) 2011 EfficiOS Inc.
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #define _LGPL_SOURCE
   9 #include <popt.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <sys/stat.h>
  14 #include <sys/types.h>
  15 #include <unistd.h>
  16 #include <inttypes.h>
  17 #include <ctype.h>
  18
  19 #include <common/sessiond-comm/sessiond-comm.hpp>
  20 #include <common/utils.hpp>
  21 #include <common/mi-lttng.hpp>
  22
  23 #include <lttng/domain-internal.hpp>
  24
  25 #include "../command.hpp"
  26 #include "../utils.hpp"
  27
  28
  29 static struct lttng_channel chan_opts;
  30 static int opt_kernel;
  31 static char *opt_session_name;
  32 static int opt_userspace;
  33 static char *opt_output;
  34 static int opt_buffer_uid;
  35 static int opt_buffer_pid;
  36 static int opt_buffer_global;
  37 static struct {
  38         bool set;
  39         uint64_t interval;
  40 } opt_monitor_timer;
  41 static struct {
  42         bool set;
  43         int64_t value;
  44 } opt_blocking_timeout;
  45
  46 static struct mi_writer *writer;
  47
  48 #ifdef LTTNG_EMBED_HELP
  49 static const char help_msg[] =
  50 #include <lttng-enable-channel.1.h>
  51 ;
  52 #endif
  53
  54 enum {
  55         OPT_HELP = 1,
  56         OPT_DISCARD,
  57         OPT_OVERWRITE,
  58         OPT_SUBBUF_SIZE,
  59         OPT_NUM_SUBBUF,
  60         OPT_SWITCH_TIMER,
  61         OPT_MONITOR_TIMER,
  62         OPT_READ_TIMER,
  63         OPT_USERSPACE,
  64         OPT_LIST_OPTIONS,
  65         OPT_TRACEFILE_SIZE,
  66         OPT_TRACEFILE_COUNT,
  67         OPT_BLOCKING_TIMEOUT,
  68 };
  69
  70 static struct lttng_handle *handle;
  71
  72 const char *output_mmap = "mmap";
  73 const char *output_splice = "splice";
  74
  75 static struct poptOption long_options[] = {
  76         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  77         {"help",           'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
  78         {"session",        's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
  79         {"kernel",         'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
  80         {"userspace",      'u', POPT_ARG_NONE, 0, OPT_USERSPACE, 0, 0},
  81         {"discard",        0,   POPT_ARG_NONE, 0, OPT_DISCARD, 0, 0},
  82         {"overwrite",      0,   POPT_ARG_NONE, 0, OPT_OVERWRITE, 0, 0},
  83         {"subbuf-size",    0,   POPT_ARG_STRING, 0, OPT_SUBBUF_SIZE, 0, 0},
  84         {"num-subbuf",     0,   POPT_ARG_INT, 0, OPT_NUM_SUBBUF, 0, 0},
  85         {"switch-timer",   0,   POPT_ARG_INT, 0, OPT_SWITCH_TIMER, 0, 0},
  86         {"monitor-timer",  0,   POPT_ARG_INT, 0, OPT_MONITOR_TIMER, 0, 0},
  87         {"read-timer",     0,   POPT_ARG_INT, 0, OPT_READ_TIMER, 0, 0},
  88         {"list-options",   0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  89         {"output",         0,   POPT_ARG_STRING, &opt_output, 0, 0, 0},
  90         {"buffers-uid",    0,   POPT_ARG_VAL, &opt_buffer_uid, 1, 0, 0},
  91         {"buffers-pid",    0,   POPT_ARG_VAL, &opt_buffer_pid, 1, 0, 0},
  92         {"buffers-global", 0,   POPT_ARG_VAL, &opt_buffer_global, 1, 0, 0},
  93         {"tracefile-size", 'C',   POPT_ARG_INT, 0, OPT_TRACEFILE_SIZE, 0, 0},
  94         {"tracefile-count", 'W',   POPT_ARG_INT, 0, OPT_TRACEFILE_COUNT, 0, 0},
  95         {"blocking-timeout",     0,   POPT_ARG_INT, 0, OPT_BLOCKING_TIMEOUT, 0, 0},
  96         {0, 0, 0, 0, 0, 0, 0}
  97 };
  98
  99 /*
 100  * Set default attributes depending on those already defined from the command
 101  * line.
 102  */
 103 static void set_default_attr(struct lttng_domain *dom)
 104 {
 105         struct lttng_channel_attr default_attr;
 106
 107         memset(&default_attr, 0, sizeof(default_attr));
 108
 109         /* Set attributes */
 110         lttng_channel_set_default_attr(dom, &default_attr);
 111
 112         if (chan_opts.attr.overwrite == -1) {
 113                 chan_opts.attr.overwrite = default_attr.overwrite;
 114         }
 115         if (chan_opts.attr.subbuf_size == -1) {
 116                 chan_opts.attr.subbuf_size = default_attr.subbuf_size;
 117         }
 118         if (chan_opts.attr.num_subbuf == -1) {
 119                 chan_opts.attr.num_subbuf = default_attr.num_subbuf;
 120         }
 121         if (chan_opts.attr.switch_timer_interval == -1) {
 122                 chan_opts.attr.switch_timer_interval = default_attr.switch_timer_interval;
 123         }
 124         if (chan_opts.attr.read_timer_interval == -1) {
 125                 chan_opts.attr.read_timer_interval = default_attr.read_timer_interval;
 126         }
 127         if ((int) chan_opts.attr.output == -1) {
 128                 chan_opts.attr.output = default_attr.output;
 129         }
 130         if (chan_opts.attr.tracefile_count == -1) {
 131                 chan_opts.attr.tracefile_count = default_attr.tracefile_count;
 132         }
 133         if (chan_opts.attr.tracefile_size == -1) {
 134                 chan_opts.attr.tracefile_size = default_attr.tracefile_size;
 135         }
 136 }
 137
 138 /*
 139  * Adding channel using the lttng API.
 140  */
 141 static int enable_channel(char *session_name, char *channel_list)
 142 {
 143         struct lttng_channel *channel = NULL;
 144         int ret = CMD_SUCCESS, warn = 0, error = 0, success = 0;
 145         char *channel_name;
 146         struct lttng_domain dom;
 147
 148         memset(&dom, 0, sizeof(dom));
 149
 150         /* Validate options. */
 151         if (opt_kernel) {
 152                 if (opt_blocking_timeout.set) {
 153                         ERR("Retry timeout option not supported for kernel domain (-k)");
 154                         ret = CMD_ERROR;
 155                         goto error;
 156                 }
 157         }
 158
 159         /* Create lttng domain */
 160         if (opt_kernel) {
 161                 dom.type = LTTNG_DOMAIN_KERNEL;
 162                 dom.buf_type = LTTNG_BUFFER_GLOBAL;
 163                 if (opt_buffer_uid || opt_buffer_pid) {
 164                         ERR("Buffer type not supported for domain -k");
 165                         ret = CMD_ERROR;
 166                         goto error;
 167                 }
 168         } else if (opt_userspace) {
 169                 dom.type = LTTNG_DOMAIN_UST;
 170                 if (opt_buffer_pid) {
 171                         dom.buf_type = LTTNG_BUFFER_PER_PID;
 172                 } else {
 173                         if (opt_buffer_global) {
 174                                 ERR("Buffer type not supported for domain -u");
 175                                 ret = CMD_ERROR;
 176                                 goto error;
 177                         }
 178                         dom.buf_type = LTTNG_BUFFER_PER_UID;
 179                 }
 180         } else {
 181                 /* Checked by the caller. */
 182                 abort();
 183         }
 184
 185         set_default_attr(&dom);
 186
 187         if (chan_opts.attr.tracefile_size == 0 && chan_opts.attr.tracefile_count) {
 188                 ERR("Missing option --tracefile-size. "
 189                                 "A file count without a size won't do anything.");
 190                 ret = CMD_ERROR;
 191                 goto error;
 192         }
 193
 194         if ((chan_opts.attr.tracefile_size > 0) &&
 195                         (chan_opts.attr.tracefile_size < chan_opts.attr.subbuf_size)) {
 196                 WARN("Tracefile size rounded up from (%" PRIu64 ") to subbuffer size (%" PRIu64 ")",
 197                                 chan_opts.attr.tracefile_size, chan_opts.attr.subbuf_size);
 198                 chan_opts.attr.tracefile_size = chan_opts.attr.subbuf_size;
 199         }
 200
 201         /* Setting channel output */
 202         if (opt_output) {
 203                 if (!strncmp(output_mmap, opt_output, strlen(output_mmap))) {
 204                         chan_opts.attr.output = LTTNG_EVENT_MMAP;
 205                 } else if (!strncmp(output_splice, opt_output, strlen(output_splice))) {
 206                         chan_opts.attr.output = LTTNG_EVENT_SPLICE;
 207                 } else {
 208                         ERR("Unknown output type %s. Possible values are: %s, %s\n",
 209                                         opt_output, output_mmap, output_splice);
 210                         ret = CMD_ERROR;
 211                         goto error;
 212                 }
 213         }
 214
 215         handle = lttng_create_handle(session_name, &dom);
 216         if (handle == NULL) {
 217                 ret = -1;
 218                 goto error;
 219         }
 220
 221         /* Mi open channels element */
 222         if (lttng_opt_mi) {
 223                 LTTNG_ASSERT(writer);
 224                 ret = mi_lttng_channels_open(writer);
 225                 if (ret) {
 226                         ret = CMD_ERROR;
 227                         goto error;
 228                 }
 229         }
 230
 231         /* Strip channel list (format: chan1,chan2,...) */
 232         channel_name = strtok(channel_list, ",");
 233         while (channel_name != NULL) {
 234                 void *extended_ptr;
 235
 236                 /* Validate channel name's length */
 237                 if (strlen(channel_name) >= sizeof(chan_opts.name)) {
 238                         ERR("Channel name is too long (max. %zu characters)",
 239                                         sizeof(chan_opts.name) - 1);
 240                         error = 1;
 241                         goto skip_enable;
 242                 }
 243
 244                 /*
 245                  * A dynamically-allocated channel is used in order to allow
 246                  * the configuration of extended attributes (post-2.9).
 247                  */
 248                 channel = lttng_channel_create(&dom);
 249                 if (!channel) {
 250                         ERR("Unable to create channel object");
 251                         error = 1;
 252                         goto error;
 253                 }
 254
 255                 /* Copy channel name */
 256                 strcpy(channel->name, channel_name);
 257                 channel->enabled = 1;
 258                 extended_ptr = channel->attr.extended.ptr;
 259                 memcpy(&channel->attr, &chan_opts.attr, sizeof(chan_opts.attr));
 260                 channel->attr.extended.ptr = extended_ptr;
 261                 if (opt_monitor_timer.set) {
 262                         ret = lttng_channel_set_monitor_timer_interval(channel,
 263                                         opt_monitor_timer.interval);
 264                         if (ret) {
 265                                 ERR("Failed to set the channel's monitor timer interval");
 266                                 error = 1;
 267                                 goto error;
 268                         }
 269                 }
 270                 if (opt_blocking_timeout.set) {
 271                         ret = lttng_channel_set_blocking_timeout(channel,
 272                                         opt_blocking_timeout.value);
 273                         if (ret) {
 274                                 ERR("Failed to set the channel's blocking timeout");
 275                                 error = 1;
 276                                 goto error;
 277                         }
 278                 }
 279
 280                 DBG("Enabling channel %s", channel_name);
 281
 282                 ret = lttng_enable_channel(handle, channel);
 283                 if (ret < 0) {
 284                         success = 0;
 285                         switch (-ret) {
 286                         case LTTNG_ERR_KERN_CHAN_EXIST:
 287                         case LTTNG_ERR_UST_CHAN_EXIST:
 288                         case LTTNG_ERR_CHAN_EXIST:
 289                                 WARN("Channel %s: %s (session %s)", channel_name,
 290                                                 lttng_strerror(ret), session_name);
 291                                 warn = 1;
 292                                 break;
 293                         case LTTNG_ERR_INVALID_CHANNEL_NAME:
 294                                 ERR("Invalid channel name: \"%s\". "
 295                                     "Channel names may not start with '.', and "
 296                                     "may not contain '/'.", channel_name);
 297                                 error = 1;
 298                                 break;
 299                         default:
 300                                 ERR("Channel %s: %s (session %s)", channel_name,
 301                                                 lttng_strerror(ret), session_name);
 302                                 error = 1;
 303                                 break;
 304                         }
 305                 } else {
 306                         MSG("%s channel %s enabled for session %s",
 307                                         lttng_domain_type_str(dom.type),
 308                                         channel_name, session_name);
 309                         success = 1;
 310                 }
 311
 312 skip_enable:
 313                 if (lttng_opt_mi) {
 314                         /* Mi print the channel element and leave it open */
 315                         ret = mi_lttng_channel(writer, channel, 1);
 316                         if (ret) {
 317                                 ret = CMD_ERROR;
 318                                 goto error;
 319                         }
 320
 321                         /* Individual Success ? */
 322                         ret = mi_lttng_writer_write_element_bool(writer,
 323                                         mi_lttng_element_command_success, success);
 324                         if (ret) {
 325                                 ret = CMD_ERROR;
 326                                 goto error;
 327                         }
 328
 329                         /* Close channel element */
 330                         ret = mi_lttng_writer_close_element(writer);
 331                         if (ret) {
 332                                 ret = CMD_ERROR;
 333                                 goto error;
 334                         }
 335                 }
 336
 337                 /* Next channel */
 338                 channel_name = strtok(NULL, ",");
 339                 lttng_channel_destroy(channel);
 340                 channel = NULL;
 341         }
 342
 343         if (lttng_opt_mi) {
 344                 /* Close channels element */
 345                 ret = mi_lttng_writer_close_element(writer);
 346                 if (ret) {
 347                         ret = CMD_ERROR;
 348                         goto error;
 349                 }
 350         }
 351
 352         ret = CMD_SUCCESS;
 353
 354 error:
 355         if (channel) {
 356                 lttng_channel_destroy(channel);
 357         }
 358         /* If more important error happen bypass the warning */
 359         if (!ret && warn) {
 360                 ret = CMD_WARNING;
 361         }
 362         /* If more important error happen bypass the warning */
 363         if (!ret && error) {
 364                 ret = CMD_ERROR;
 365         }
 366
 367         lttng_destroy_handle(handle);
 368
 369         return ret;
 370 }
 371
 372 /*
 373  * Default value for channel configuration.
 374  */
 375 static void init_channel_config(void)
 376 {
 377         /*
 378          * Put -1 everywhere so we can identify those set by the command line and
 379          * those needed to be set by the default values.
 380          */
 381         memset(&chan_opts.attr, -1, sizeof(chan_opts.attr));
 382         chan_opts.attr.extended.ptr = NULL;
 383 }
 384
 385 /*
 386  * Add channel to trace session
 387  */
 388 int cmd_enable_channels(int argc, const char **argv)
 389 {
 390         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 391         static poptContext pc;
 392         char *session_name = NULL;
 393         char *channel_list = NULL;
 394         char *opt_arg = NULL;
 395         const char *arg_channel_list = NULL;
 396         const char *leftover = NULL;
 397
 398         init_channel_config();
 399
 400         pc = poptGetContext(NULL, argc, argv, long_options, 0);
 401         poptReadDefaultConfig(pc, 0);
 402
 403         while ((opt = poptGetNextOpt(pc)) != -1) {
 404                 switch (opt) {
 405                 case OPT_HELP:
 406                         SHOW_HELP();
 407                         goto end;
 408                 case OPT_DISCARD:
 409                         chan_opts.attr.overwrite = 0;
 410                         DBG("Channel set to discard");
 411                         break;
 412                 case OPT_OVERWRITE:
 413                         chan_opts.attr.overwrite = 1;
 414                         DBG("Channel set to overwrite");
 415                         break;
 416                 case OPT_SUBBUF_SIZE:
 417                 {
 418                         uint64_t rounded_size;
 419                         int order;
 420
 421                         /* Parse the size */
 422                         opt_arg = poptGetOptArg(pc);
 423                         if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.subbuf_size) < 0 || !chan_opts.attr.subbuf_size) {
 424                                 ERR("Wrong value in --subbuf-size parameter: %s", opt_arg);
 425                                 ret = CMD_ERROR;
 426                                 goto end;
 427                         }
 428
 429                         order = get_count_order_u64(chan_opts.attr.subbuf_size);
 430                         LTTNG_ASSERT(order >= 0);
 431                         rounded_size = 1ULL << order;
 432                         if (rounded_size < chan_opts.attr.subbuf_size) {
 433                                 ERR("The subbuf size (%" PRIu64 ") is rounded and overflows!",
 434                                                 chan_opts.attr.subbuf_size);
 435                                 ret = CMD_ERROR;
 436                                 goto end;
 437                         }
 438
 439                         if (rounded_size != chan_opts.attr.subbuf_size) {
 440                                 WARN("The subbuf size (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 441                                                 chan_opts.attr.subbuf_size, rounded_size);
 442                                 chan_opts.attr.subbuf_size = rounded_size;
 443                         }
 444
 445                         /* Should now be power of 2 */
 446                         LTTNG_ASSERT(!((chan_opts.attr.subbuf_size - 1) & chan_opts.attr.subbuf_size));
 447
 448                         DBG("Channel subbuf size set to %" PRIu64, chan_opts.attr.subbuf_size);
 449                         break;
 450                 }
 451                 case OPT_NUM_SUBBUF:
 452                 {
 453                         uint64_t rounded_size;
 454                         int order;
 455
 456                         errno = 0;
 457                         opt_arg = poptGetOptArg(pc);
 458                         chan_opts.attr.num_subbuf = strtoull(opt_arg, NULL, 0);
 459                         if (errno != 0 || !chan_opts.attr.num_subbuf || !isdigit(opt_arg[0])) {
 460                                 ERR("Wrong value in --num-subbuf parameter: %s", opt_arg);
 461                                 ret = CMD_ERROR;
 462                                 goto end;
 463                         }
 464
 465                         order = get_count_order_u64(chan_opts.attr.num_subbuf);
 466                         LTTNG_ASSERT(order >= 0);
 467                         rounded_size = 1ULL << order;
 468                         if (rounded_size < chan_opts.attr.num_subbuf) {
 469                                 ERR("The number of subbuffers (%" PRIu64 ") is rounded and overflows!",
 470                                                 chan_opts.attr.num_subbuf);
 471                                 ret = CMD_ERROR;
 472                                 goto end;
 473                         }
 474
 475                         if (rounded_size != chan_opts.attr.num_subbuf) {
 476                                 WARN("The number of subbuffers (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 477                                                 chan_opts.attr.num_subbuf, rounded_size);
 478                                 chan_opts.attr.num_subbuf = rounded_size;
 479                         }
 480
 481                         /* Should now be power of 2 */
 482                         LTTNG_ASSERT(!((chan_opts.attr.num_subbuf - 1) & chan_opts.attr.num_subbuf));
 483
 484                         DBG("Channel subbuf num set to %" PRIu64, chan_opts.attr.num_subbuf);
 485                         break;
 486                 }
 487                 case OPT_SWITCH_TIMER:
 488                 {
 489                         uint64_t v;
 490
 491                         errno = 0;
 492                         opt_arg = poptGetOptArg(pc);
 493
 494                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 495                                 ERR("Wrong value for --switch-timer parameter: %s", opt_arg);
 496                                 ret = CMD_ERROR;
 497                                 goto end;
 498                         }
 499
 500                         if (v != (uint32_t) v) {
 501                                 ERR("32-bit overflow in --switch-timer parameter: %s", opt_arg);
 502                                 ret = CMD_ERROR;
 503                                 goto end;
 504                         }
 505                         chan_opts.attr.switch_timer_interval = (uint32_t) v;
 506                         DBG("Channel switch timer interval set to %d %s",
 507                                         chan_opts.attr.switch_timer_interval,
 508                                         USEC_UNIT);
 509                         break;
 510                 }
 511                 case OPT_READ_TIMER:
 512                 {
 513                         uint64_t v;
 514
 515                         errno = 0;
 516                         opt_arg = poptGetOptArg(pc);
 517
 518                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 519                                 ERR("Wrong value for --read-timer parameter: %s", opt_arg);
 520                                 ret = CMD_ERROR;
 521                                 goto end;
 522                         }
 523
 524                         if (v != (uint32_t) v) {
 525                                 ERR("32-bit overflow in --read-timer parameter: %s", opt_arg);
 526                                 ret = CMD_ERROR;
 527                                 goto end;
 528                         }
 529                         chan_opts.attr.read_timer_interval = (uint32_t) v;
 530                         DBG("Channel read timer interval set to %d %s",
 531                                         chan_opts.attr.read_timer_interval,
 532                                         USEC_UNIT);
 533                         break;
 534                 }
 535                 case OPT_MONITOR_TIMER:
 536                 {
 537                         uint64_t v;
 538
 539                         errno = 0;
 540                         opt_arg = poptGetOptArg(pc);
 541
 542                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 543                                 ERR("Wrong value for --monitor-timer parameter: %s", opt_arg);
 544                                 ret = CMD_ERROR;
 545                                 goto end;
 546                         }
 547                         opt_monitor_timer.interval = (uint64_t) v;
 548                         opt_monitor_timer.set = true;
 549                         DBG("Channel monitor timer interval set to %" PRIu64 " %s",
 550                                         opt_monitor_timer.interval,
 551                                         USEC_UNIT);
 552                         break;
 553                 }
 554                 case OPT_BLOCKING_TIMEOUT:
 555                 {
 556                         uint64_t v;
 557                         long long v_msec;
 558
 559                         errno = 0;
 560                         opt_arg = poptGetOptArg(pc);
 561
 562                         if (strcmp(opt_arg, "inf") == 0) {
 563                                 opt_blocking_timeout.value = (int64_t) -1;
 564                                 opt_blocking_timeout.set = true;
 565                                 DBG("Channel blocking timeout set to infinity");
 566                                 break;
 567                         }
 568
 569                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 570                                 ERR("Wrong value for --blocking-timeout parameter: %s", opt_arg);
 571                                 ret = CMD_ERROR;
 572                                 goto end;
 573                         }
 574
 575                         /*
 576                          * While LTTng-UST and LTTng-tools will accept a
 577                          * blocking timeout expressed in µs, the current
 578                          * tracer implementation relies on poll() which
 579                          * takes an "int timeout" parameter expressed in
 580                          * msec.
 581                          *
 582                          * Since the error reporting from the tracer is
 583                          * not precise, we perform this check here to
 584                          * provide a helpful error message in case of
 585                          * overflow.
 586                          *
 587                          * The setter (liblttng-ctl) also performs an
 588                          * equivalent check.
 589                          */
 590                         v_msec = v / 1000;
 591                         if (v_msec != (int32_t) v_msec) {
 592                                 ERR("32-bit milliseconds overflow in --blocking-timeout parameter: %s", opt_arg);
 593                                 ret = CMD_ERROR;
 594                                 goto end;
 595                         }
 596
 597                         opt_blocking_timeout.value = (int64_t) v;
 598                         opt_blocking_timeout.set = true;
 599                         DBG("Channel blocking timeout set to %" PRId64 " %s%s",
 600                                         opt_blocking_timeout.value,
 601                                         USEC_UNIT,
 602                                         opt_blocking_timeout.value == 0 ?
 603                                                 " (non-blocking)" : "");
 604                         break;
 605                 }
 606                 case OPT_USERSPACE:
 607                         opt_userspace = 1;
 608                         break;
 609                 case OPT_TRACEFILE_SIZE:
 610                         opt_arg = poptGetOptArg(pc);
 611                         if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.tracefile_size) < 0) {
 612                                 ERR("Wrong value in --tracefile-size parameter: %s", opt_arg);
 613                                 ret = CMD_ERROR;
 614                                 goto end;
 615                         }
 616                         DBG("Maximum tracefile size set to %" PRIu64,
 617                                         chan_opts.attr.tracefile_size);
 618                         break;
 619                 case OPT_TRACEFILE_COUNT:
 620                 {
 621                         unsigned long v;
 622
 623                         errno = 0;
 624                         opt_arg = poptGetOptArg(pc);
 625                         v = strtoul(opt_arg, NULL, 0);
 626                         if (errno != 0 || !isdigit(opt_arg[0])) {
 627                                 ERR("Wrong value in --tracefile-count parameter: %s", opt_arg);
 628                                 ret = CMD_ERROR;
 629                                 goto end;
 630                         }
 631                         if (v != (uint32_t) v) {
 632                                 ERR("32-bit overflow in --tracefile-count parameter: %s", opt_arg);
 633                                 ret = CMD_ERROR;
 634                                 goto end;
 635                         }
 636                         chan_opts.attr.tracefile_count = (uint32_t) v;
 637                         DBG("Maximum tracefile count set to %" PRIu64,
 638                                         chan_opts.attr.tracefile_count);
 639                         break;
 640                 }
 641                 case OPT_LIST_OPTIONS:
 642                         list_cmd_options(stdout, long_options);
 643                         goto end;
 644                 default:
 645                         ret = CMD_UNDEFINED;
 646                         goto end;
 647                 }
 648
 649                 if (opt_arg) {
 650                         free(opt_arg);
 651                         opt_arg = nullptr;
 652                 }
 653         }
 654
 655         ret = print_missing_or_multiple_domains(
 656                         opt_kernel + opt_userspace, false);
 657         if (ret) {
 658                 ret = CMD_ERROR;
 659                 goto end;
 660         }
 661
 662         if (chan_opts.attr.overwrite == 1 && opt_blocking_timeout.set &&
 663                         opt_blocking_timeout.value != 0) {
 664                 ERR("You cannot specify --overwrite and --blocking-timeout=N, "
 665                         "where N is different than 0");
 666                 ret = CMD_ERROR;
 667                 goto end;
 668         }
 669
 670         /* Mi check */
 671         if (lttng_opt_mi) {
 672                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 673                 if (!writer) {
 674                         ret = -LTTNG_ERR_NOMEM;
 675                         goto end;
 676                 }
 677
 678                 /* Open command element */
 679                 ret = mi_lttng_writer_command_open(writer,
 680                                 mi_lttng_element_command_enable_channels);
 681                 if (ret) {
 682                         ret = CMD_ERROR;
 683                         goto end;
 684                 }
 685
 686                 /* Open output element */
 687                 ret = mi_lttng_writer_open_element(writer,
 688                                 mi_lttng_element_command_output);
 689                 if (ret) {
 690                         ret = CMD_ERROR;
 691                         goto end;
 692                 }
 693         }
 694
 695         arg_channel_list = poptGetArg(pc);
 696         if (arg_channel_list == NULL) {
 697                 ERR("Missing channel name.");
 698                 ret = CMD_ERROR;
 699                 success = 0;
 700                 goto mi_closing;
 701         }
 702
 703         channel_list = strdup(arg_channel_list);
 704         if (channel_list == NULL) {
 705                 PERROR("Failed to copy channel name");
 706                 ret = CMD_ERROR;
 707                 success = 0;
 708                 goto mi_closing;
 709         }
 710
 711         leftover = poptGetArg(pc);
 712         if (leftover) {
 713                 ERR("Unknown argument: %s", leftover);
 714                 ret = CMD_ERROR;
 715                 success = 0;
 716                 goto mi_closing;
 717         }
 718
 719         if (!opt_session_name) {
 720                 session_name = get_session_name();
 721                 if (session_name == NULL) {
 722                         command_ret = CMD_ERROR;
 723                         success = 0;
 724                         goto mi_closing;
 725                 }
 726         } else {
 727                 session_name = opt_session_name;
 728         }
 729
 730         command_ret = enable_channel(session_name, channel_list);
 731         if (command_ret) {
 732                 success = 0;
 733         }
 734
 735 mi_closing:
 736         /* Mi closing */
 737         if (lttng_opt_mi) {
 738                 /* Close  output element */
 739                 ret = mi_lttng_writer_close_element(writer);
 740                 if (ret) {
 741                         goto end;
 742                 }
 743
 744                 /* Success ? */
 745                 ret = mi_lttng_writer_write_element_bool(writer,
 746                                 mi_lttng_element_command_success, success);
 747                 if (ret) {
 748                         goto end;
 749                 }
 750
 751                 /* Command element close */
 752                 ret = mi_lttng_writer_command_close(writer);
 753                 if (ret) {
 754                         goto end;
 755                 }
 756         }
 757
 758 end:
 759         /* Mi clean-up */
 760         if (writer && mi_lttng_writer_destroy(writer)) {
 761                 /* Preserve original error code */
 762                 ret = ret ? ret : LTTNG_ERR_MI_IO_FAIL;
 763         }
 764
 765         if (!opt_session_name && session_name) {
 766                 free(session_name);
 767         }
 768
 769         free(channel_list);
 770
 771         /* Overwrite ret if an error occurred when enable_channel */
 772         ret = command_ret ? command_ret : ret;
 773         poptFreeContext(pc);
 774         free(opt_arg);
 775         return ret;
 776 }