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