src/bin/lttng/commands/enable_channels.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _LGPL_SOURCE
  19 #include <popt.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <sys/stat.h>
  24 #include <sys/types.h>
  25 #include <unistd.h>
  26 #include <inttypes.h>
  27 #include <assert.h>
  28 #include <ctype.h>
  29
  30 #include <common/sessiond-comm/sessiond-comm.h>
  31 #include <common/utils.h>
  32 #include <common/mi-lttng.h>
  33
  34 #include "../command.h"
  35 #include "../utils.h"
  36
  37
  38 static struct lttng_channel chan_opts;
  39 static char *opt_channels;
  40 static int opt_kernel;
  41 static char *opt_session_name;
  42 static int opt_userspace;
  43 static char *opt_output;
  44 static int opt_buffer_uid;
  45 static int opt_buffer_pid;
  46 static int opt_buffer_global;
  47 static struct {
  48         bool set;
  49         uint64_t interval;
  50 } opt_monitor_timer;
  51 static struct {
  52         bool set;
  53         int64_t value;
  54 } opt_blocking_timeout;
  55
  56 static struct mi_writer *writer;
  57
  58 #ifdef LTTNG_EMBED_HELP
  59 static const char help_msg[] =
  60 #include <lttng-enable-channel.1.h>
  61 ;
  62 #endif
  63
  64 enum {
  65         OPT_HELP = 1,
  66         OPT_DISCARD,
  67         OPT_OVERWRITE,
  68         OPT_SUBBUF_SIZE,
  69         OPT_NUM_SUBBUF,
  70         OPT_SWITCH_TIMER,
  71         OPT_MONITOR_TIMER,
  72         OPT_READ_TIMER,
  73         OPT_USERSPACE,
  74         OPT_LIST_OPTIONS,
  75         OPT_TRACEFILE_SIZE,
  76         OPT_TRACEFILE_COUNT,
  77         OPT_BLOCKING_TIMEOUT,
  78 };
  79
  80 static struct lttng_handle *handle;
  81
  82 const char *output_mmap = "mmap";
  83 const char *output_splice = "splice";
  84
  85 static struct poptOption long_options[] = {
  86         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  87         {"help",           'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
  88         {"session",        's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
  89         {"kernel",         'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
  90         {"userspace",      'u', POPT_ARG_NONE, 0, OPT_USERSPACE, 0, 0},
  91         {"discard",        0,   POPT_ARG_NONE, 0, OPT_DISCARD, 0, 0},
  92         {"overwrite",      0,   POPT_ARG_NONE, 0, OPT_OVERWRITE, 0, 0},
  93         {"subbuf-size",    0,   POPT_ARG_STRING, 0, OPT_SUBBUF_SIZE, 0, 0},
  94         {"num-subbuf",     0,   POPT_ARG_INT, 0, OPT_NUM_SUBBUF, 0, 0},
  95         {"switch-timer",   0,   POPT_ARG_INT, 0, OPT_SWITCH_TIMER, 0, 0},
  96         {"monitor-timer",  0,   POPT_ARG_INT, 0, OPT_MONITOR_TIMER, 0, 0},
  97         {"read-timer",     0,   POPT_ARG_INT, 0, OPT_READ_TIMER, 0, 0},
  98         {"list-options",   0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  99         {"output",         0,   POPT_ARG_STRING, &opt_output, 0, 0, 0},
 100         {"buffers-uid",    0,   POPT_ARG_VAL, &opt_buffer_uid, 1, 0, 0},
 101         {"buffers-pid",    0,   POPT_ARG_VAL, &opt_buffer_pid, 1, 0, 0},
 102         {"buffers-global", 0,   POPT_ARG_VAL, &opt_buffer_global, 1, 0, 0},
 103         {"tracefile-size", 'C',   POPT_ARG_INT, 0, OPT_TRACEFILE_SIZE, 0, 0},
 104         {"tracefile-count", 'W',   POPT_ARG_INT, 0, OPT_TRACEFILE_COUNT, 0, 0},
 105         {"blocking-timeout",     0,   POPT_ARG_INT, 0, OPT_BLOCKING_TIMEOUT, 0, 0},
 106         {0, 0, 0, 0, 0, 0, 0}
 107 };
 108
 109 /*
 110  * Set default attributes depending on those already defined from the command
 111  * line.
 112  */
 113 static void set_default_attr(struct lttng_domain *dom)
 114 {
 115         struct lttng_channel_attr default_attr;
 116
 117         memset(&default_attr, 0, sizeof(default_attr));
 118
 119         /* Set attributes */
 120         lttng_channel_set_default_attr(dom, &default_attr);
 121
 122         if (chan_opts.attr.overwrite == -1) {
 123                 chan_opts.attr.overwrite = default_attr.overwrite;
 124         }
 125         if (chan_opts.attr.subbuf_size == -1) {
 126                 chan_opts.attr.subbuf_size = default_attr.subbuf_size;
 127         }
 128         if (chan_opts.attr.num_subbuf == -1) {
 129                 chan_opts.attr.num_subbuf = default_attr.num_subbuf;
 130         }
 131         if (chan_opts.attr.switch_timer_interval == -1) {
 132                 chan_opts.attr.switch_timer_interval = default_attr.switch_timer_interval;
 133         }
 134         if (chan_opts.attr.read_timer_interval == -1) {
 135                 chan_opts.attr.read_timer_interval = default_attr.read_timer_interval;
 136         }
 137         if ((int) chan_opts.attr.output == -1) {
 138                 chan_opts.attr.output = default_attr.output;
 139         }
 140         if (chan_opts.attr.tracefile_count == -1) {
 141                 chan_opts.attr.tracefile_count = default_attr.tracefile_count;
 142         }
 143         if (chan_opts.attr.tracefile_size == -1) {
 144                 chan_opts.attr.tracefile_size = default_attr.tracefile_size;
 145         }
 146 }
 147
 148 /*
 149  * Adding channel using the lttng API.
 150  */
 151 static int enable_channel(char *session_name)
 152 {
 153         struct lttng_channel *channel = NULL;
 154         int ret = CMD_SUCCESS, warn = 0, error = 0, success = 0;
 155         char *channel_name;
 156         struct lttng_domain dom;
 157
 158         memset(&dom, 0, sizeof(dom));
 159
 160         /* Validate options. */
 161         if (opt_kernel) {
 162                 if (opt_blocking_timeout.set) {
 163                         ERR("Retry timeout option not supported for kernel domain (-k)");
 164                         ret = CMD_ERROR;
 165                         goto error;
 166                 }
 167         }
 168
 169         /* Create lttng domain */
 170         if (opt_kernel) {
 171                 dom.type = LTTNG_DOMAIN_KERNEL;
 172                 dom.buf_type = LTTNG_BUFFER_GLOBAL;
 173                 if (opt_buffer_uid || opt_buffer_pid) {
 174                         ERR("Buffer type not supported for domain -k");
 175                         ret = CMD_ERROR;
 176                         goto error;
 177                 }
 178         } else if (opt_userspace) {
 179                 dom.type = LTTNG_DOMAIN_UST;
 180                 if (opt_buffer_pid) {
 181                         dom.buf_type = LTTNG_BUFFER_PER_PID;
 182                 } else {
 183                         if (opt_buffer_global) {
 184                                 ERR("Buffer type not supported for domain -u");
 185                                 ret = CMD_ERROR;
 186                                 goto error;
 187                         }
 188                         dom.buf_type = LTTNG_BUFFER_PER_UID;
 189                 }
 190         } else {
 191                 /* Checked by the caller. */
 192                 assert(0);
 193         }
 194
 195         set_default_attr(&dom);
 196
 197         if (chan_opts.attr.tracefile_size == 0 && chan_opts.attr.tracefile_count) {
 198                 ERR("Missing option --tracefile-size. "
 199                                 "A file count without a size won't do anything.");
 200                 ret = CMD_ERROR;
 201                 goto error;
 202         }
 203
 204         if ((chan_opts.attr.tracefile_size > 0) &&
 205                         (chan_opts.attr.tracefile_size < chan_opts.attr.subbuf_size)) {
 206                 WARN("Tracefile size rounded up from (%" PRIu64 ") to subbuffer size (%" PRIu64 ")",
 207                                 chan_opts.attr.tracefile_size, chan_opts.attr.subbuf_size);
 208                 chan_opts.attr.tracefile_size = chan_opts.attr.subbuf_size;
 209         }
 210
 211         /* Setting channel output */
 212         if (opt_output) {
 213                 if (!strncmp(output_mmap, opt_output, strlen(output_mmap))) {
 214                         chan_opts.attr.output = LTTNG_EVENT_MMAP;
 215                 } else if (!strncmp(output_splice, opt_output, strlen(output_splice))) {
 216                         chan_opts.attr.output = LTTNG_EVENT_SPLICE;
 217                 } else {
 218                         ERR("Unknown output type %s. Possible values are: %s, %s\n",
 219                                         opt_output, output_mmap, output_splice);
 220                         ret = CMD_ERROR;
 221                         goto error;
 222                 }
 223         }
 224
 225         handle = lttng_create_handle(session_name, &dom);
 226         if (handle == NULL) {
 227                 ret = -1;
 228                 goto error;
 229         }
 230
 231         /* Mi open channels element */
 232         if (lttng_opt_mi) {
 233                 assert(writer);
 234                 ret = mi_lttng_channels_open(writer);
 235                 if (ret) {
 236                         ret = CMD_ERROR;
 237                         goto error;
 238                 }
 239         }
 240
 241         /* Strip channel list (format: chan1,chan2,...) */
 242         channel_name = strtok(opt_channels, ",");
 243         while (channel_name != NULL) {
 244                 void *extended_ptr;
 245
 246                 /* Validate channel name's length */
 247                 if (strlen(channel_name) >= sizeof(chan_opts.name)) {
 248                         ERR("Channel name is too long (max. %zu characters)",
 249                                         sizeof(chan_opts.name) - 1);
 250                         error = 1;
 251                         goto skip_enable;
 252                 }
 253
 254                 /*
 255                  * A dynamically-allocated channel is used in order to allow
 256                  * the configuration of extended attributes (post-2.9).
 257                  */
 258                 channel = lttng_channel_create(&dom);
 259                 if (!channel) {
 260                         ERR("Unable to create channel object");
 261                         error = 1;
 262                         goto error;
 263                 }
 264
 265                 /* Copy channel name */
 266                 strcpy(channel->name, channel_name);
 267                 channel->enabled = 1;
 268                 extended_ptr = channel->attr.extended.ptr;
 269                 memcpy(&channel->attr, &chan_opts.attr, sizeof(chan_opts.attr));
 270                 channel->attr.extended.ptr = extended_ptr;
 271                 if (opt_monitor_timer.set) {
 272                         ret = lttng_channel_set_monitor_timer_interval(channel,
 273                                         opt_monitor_timer.interval);
 274                         if (ret) {
 275                                 ERR("Failed to set the channel's monitor timer interval");
 276                                 error = 1;
 277                                 goto error;
 278                         }
 279                 }
 280                 if (opt_blocking_timeout.set) {
 281                         ret = lttng_channel_set_blocking_timeout(channel,
 282                                         opt_blocking_timeout.value);
 283                         if (ret) {
 284                                 ERR("Failed to set the channel's blocking timeout");
 285                                 error = 1;
 286                                 goto error;
 287                         }
 288                 }
 289
 290                 DBG("Enabling channel %s", channel_name);
 291
 292                 ret = lttng_enable_channel(handle, channel);
 293                 if (ret < 0) {
 294                         success = 0;
 295                         switch (-ret) {
 296                         case LTTNG_ERR_KERN_CHAN_EXIST:
 297                         case LTTNG_ERR_UST_CHAN_EXIST:
 298                         case LTTNG_ERR_CHAN_EXIST:
 299                                 WARN("Channel %s: %s (session %s)", channel_name,
 300                                                 lttng_strerror(ret), session_name);
 301                                 warn = 1;
 302                                 break;
 303                         case LTTNG_ERR_INVALID_CHANNEL_NAME:
 304                                 ERR("Invalid channel name: \"%s\". "
 305                                     "Channel names may not start with '.', and "
 306                                     "may not contain '/'.", channel_name);
 307                                 error = 1;
 308                                 break;
 309                         default:
 310                                 ERR("Channel %s: %s (session %s)", channel_name,
 311                                                 lttng_strerror(ret), session_name);
 312                                 error = 1;
 313                                 break;
 314                         }
 315                 } else {
 316                         MSG("%s channel %s enabled for session %s",
 317                                         get_domain_str(dom.type), channel_name, session_name);
 318                         success = 1;
 319                 }
 320
 321 skip_enable:
 322                 if (lttng_opt_mi) {
 323                         /* Mi print the channel element and leave it open */
 324                         ret = mi_lttng_channel(writer, channel, 1);
 325                         if (ret) {
 326                                 ret = CMD_ERROR;
 327                                 goto error;
 328                         }
 329
 330                         /* Individual Success ? */
 331                         ret = mi_lttng_writer_write_element_bool(writer,
 332                                         mi_lttng_element_command_success, success);
 333                         if (ret) {
 334                                 ret = CMD_ERROR;
 335                                 goto error;
 336                         }
 337
 338                         /* Close channel element */
 339                         ret = mi_lttng_writer_close_element(writer);
 340                         if (ret) {
 341                                 ret = CMD_ERROR;
 342                                 goto error;
 343                         }
 344                 }
 345
 346                 /* Next channel */
 347                 channel_name = strtok(NULL, ",");
 348                 lttng_channel_destroy(channel);
 349                 channel = NULL;
 350         }
 351
 352         if (lttng_opt_mi) {
 353                 /* Close channels element */
 354                 ret = mi_lttng_writer_close_element(writer);
 355                 if (ret) {
 356                         ret = CMD_ERROR;
 357                         goto error;
 358                 }
 359         }
 360
 361         ret = CMD_SUCCESS;
 362
 363 error:
 364         if (channel) {
 365                 lttng_channel_destroy(channel);
 366         }
 367         /* If more important error happen bypass the warning */
 368         if (!ret && warn) {
 369                 ret = CMD_WARNING;
 370         }
 371         /* If more important error happen bypass the warning */
 372         if (!ret && error) {
 373                 ret = CMD_ERROR;
 374         }
 375
 376         lttng_destroy_handle(handle);
 377
 378         return ret;
 379 }
 380
 381 /*
 382  * Default value for channel configuration.
 383  */
 384 static void init_channel_config(void)
 385 {
 386         /*
 387          * Put -1 everywhere so we can identify those set by the command line and
 388          * those needed to be set by the default values.
 389          */
 390         memset(&chan_opts.attr, -1, sizeof(chan_opts.attr));
 391         chan_opts.attr.extended.ptr = NULL;
 392 }
 393
 394 /*
 395  * Add channel to trace session
 396  */
 397 int cmd_enable_channels(int argc, const char **argv)
 398 {
 399         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 400         static poptContext pc;
 401         char *session_name = NULL;
 402         char *opt_arg = NULL;
 403         const char *leftover = NULL;
 404
 405         init_channel_config();
 406
 407         pc = poptGetContext(NULL, argc, argv, long_options, 0);
 408         poptReadDefaultConfig(pc, 0);
 409
 410         while ((opt = poptGetNextOpt(pc)) != -1) {
 411                 switch (opt) {
 412                 case OPT_HELP:
 413                         SHOW_HELP();
 414                         goto end;
 415                 case OPT_DISCARD:
 416                         chan_opts.attr.overwrite = 0;
 417                         DBG("Channel set to discard");
 418                         break;
 419                 case OPT_OVERWRITE:
 420                         chan_opts.attr.overwrite = 1;
 421                         DBG("Channel set to overwrite");
 422                         break;
 423                 case OPT_SUBBUF_SIZE:
 424                 {
 425                         uint64_t rounded_size;
 426                         int order;
 427
 428                         /* Parse the size */
 429                         opt_arg = poptGetOptArg(pc);
 430                         if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.subbuf_size) < 0 || !chan_opts.attr.subbuf_size) {
 431                                 ERR("Wrong value in --subbuf-size parameter: %s", opt_arg);
 432                                 ret = CMD_ERROR;
 433                                 goto end;
 434                         }
 435
 436                         order = get_count_order_u64(chan_opts.attr.subbuf_size);
 437                         assert(order >= 0);
 438                         rounded_size = 1ULL << order;
 439                         if (rounded_size < chan_opts.attr.subbuf_size) {
 440                                 ERR("The subbuf size (%" PRIu64 ") is rounded and overflows!",
 441                                                 chan_opts.attr.subbuf_size);
 442                                 ret = CMD_ERROR;
 443                                 goto end;
 444                         }
 445
 446                         if (rounded_size != chan_opts.attr.subbuf_size) {
 447                                 WARN("The subbuf size (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 448                                                 chan_opts.attr.subbuf_size, rounded_size);
 449                                 chan_opts.attr.subbuf_size = rounded_size;
 450                         }
 451
 452                         /* Should now be power of 2 */
 453                         assert(!((chan_opts.attr.subbuf_size - 1) & chan_opts.attr.subbuf_size));
 454
 455                         DBG("Channel subbuf size set to %" PRIu64, chan_opts.attr.subbuf_size);
 456                         break;
 457                 }
 458                 case OPT_NUM_SUBBUF:
 459                 {
 460                         uint64_t rounded_size;
 461                         int order;
 462
 463                         errno = 0;
 464                         opt_arg = poptGetOptArg(pc);
 465                         chan_opts.attr.num_subbuf = strtoull(opt_arg, NULL, 0);
 466                         if (errno != 0 || !chan_opts.attr.num_subbuf || !isdigit(opt_arg[0])) {
 467                                 ERR("Wrong value in --num-subbuf parameter: %s", opt_arg);
 468                                 ret = CMD_ERROR;
 469                                 goto end;
 470                         }
 471
 472                         order = get_count_order_u64(chan_opts.attr.num_subbuf);
 473                         assert(order >= 0);
 474                         rounded_size = 1ULL << order;
 475                         if (rounded_size < chan_opts.attr.num_subbuf) {
 476                                 ERR("The number of subbuffers (%" PRIu64 ") is rounded and overflows!",
 477                                                 chan_opts.attr.num_subbuf);
 478                                 ret = CMD_ERROR;
 479                                 goto end;
 480                         }
 481
 482                         if (rounded_size != chan_opts.attr.num_subbuf) {
 483                                 WARN("The number of subbuffers (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 484                                                 chan_opts.attr.num_subbuf, rounded_size);
 485                                 chan_opts.attr.num_subbuf = rounded_size;
 486                         }
 487
 488                         /* Should now be power of 2 */
 489                         assert(!((chan_opts.attr.num_subbuf - 1) & chan_opts.attr.num_subbuf));
 490
 491                         DBG("Channel subbuf num set to %" PRIu64, chan_opts.attr.num_subbuf);
 492                         break;
 493                 }
 494                 case OPT_SWITCH_TIMER:
 495                 {
 496                         uint64_t v;
 497
 498                         errno = 0;
 499                         opt_arg = poptGetOptArg(pc);
 500
 501                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 502                                 ERR("Wrong value for --switch-timer parameter: %s", opt_arg);
 503                                 ret = CMD_ERROR;
 504                                 goto end;
 505                         }
 506
 507                         if (v != (uint32_t) v) {
 508                                 ERR("32-bit overflow in --switch-timer parameter: %s", opt_arg);
 509                                 ret = CMD_ERROR;
 510                                 goto end;
 511                         }
 512                         chan_opts.attr.switch_timer_interval = (uint32_t) v;
 513                         DBG("Channel switch timer interval set to %d %s",
 514                                         chan_opts.attr.switch_timer_interval,
 515                                         USEC_UNIT);
 516                         break;
 517                 }
 518                 case OPT_READ_TIMER:
 519                 {
 520                         uint64_t v;
 521
 522                         errno = 0;
 523                         opt_arg = poptGetOptArg(pc);
 524
 525                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 526                                 ERR("Wrong value for --read-timer parameter: %s", opt_arg);
 527                                 ret = CMD_ERROR;
 528                                 goto end;
 529                         }
 530
 531                         if (v != (uint32_t) v) {
 532                                 ERR("32-bit overflow in --read-timer parameter: %s", opt_arg);
 533                                 ret = CMD_ERROR;
 534                                 goto end;
 535                         }
 536                         chan_opts.attr.read_timer_interval = (uint32_t) v;
 537                         DBG("Channel read timer interval set to %d %s",
 538                                         chan_opts.attr.read_timer_interval,
 539                                         USEC_UNIT);
 540                         break;
 541                 }
 542                 case OPT_MONITOR_TIMER:
 543                 {
 544                         uint64_t v;
 545
 546                         errno = 0;
 547                         opt_arg = poptGetOptArg(pc);
 548
 549                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 550                                 ERR("Wrong value for --monitor-timer parameter: %s", opt_arg);
 551                                 ret = CMD_ERROR;
 552                                 goto end;
 553                         }
 554                         opt_monitor_timer.interval = (uint64_t) v;
 555                         opt_monitor_timer.set = true;
 556                         DBG("Channel monitor timer interval set to %" PRIu64 " %s",
 557                                         opt_monitor_timer.interval,
 558                                         USEC_UNIT);
 559                         break;
 560                 }
 561                 case OPT_BLOCKING_TIMEOUT:
 562                 {
 563                         uint64_t v;
 564                         long long v_msec;
 565
 566                         errno = 0;
 567                         opt_arg = poptGetOptArg(pc);
 568
 569                         if (strcmp(opt_arg, "inf") == 0) {
 570                                 opt_blocking_timeout.value = (int64_t) -1;
 571                                 opt_blocking_timeout.set = true;
 572                                 DBG("Channel blocking timeout set to infinity");
 573                                 break;
 574                         }
 575
 576                         if (utils_parse_time_suffix(opt_arg, &v) < 0) {
 577                                 ERR("Wrong value for --blocking-timeout parameter: %s", opt_arg);
 578                                 ret = CMD_ERROR;
 579                                 goto end;
 580                         }
 581
 582                         /*
 583                          * While LTTng-UST and LTTng-tools will accept a
 584                          * blocking timeout expressed in µs, the current
 585                          * tracer implementation relies on poll() which
 586                          * takes an "int timeout" parameter expressed in
 587                          * msec.
 588                          *
 589                          * Since the error reporting from the tracer is
 590                          * not precise, we perform this check here to
 591                          * provide a helpful error message in case of
 592                          * overflow.
 593                          *
 594                          * The setter (liblttng-ctl) also performs an
 595                          * equivalent check.
 596                          */
 597                         v_msec = v / 1000;
 598                         if (v_msec != (int32_t) v_msec) {
 599                                 ERR("32-bit milliseconds overflow in --blocking-timeout parameter: %s", opt_arg);
 600                                 ret = CMD_ERROR;
 601                                 goto end;
 602                         }
 603
 604                         opt_blocking_timeout.value = (int64_t) v;
 605                         opt_blocking_timeout.set = true;
 606                         DBG("Channel blocking timeout set to %" PRId64 " %s%s",
 607                                         opt_blocking_timeout.value,
 608                                         USEC_UNIT,
 609                                         opt_blocking_timeout.value == 0 ?
 610                                                 " (non-blocking)" : "");
 611                         break;
 612                 }
 613                 case OPT_USERSPACE:
 614                         opt_userspace = 1;
 615                         break;
 616                 case OPT_TRACEFILE_SIZE:
 617                         opt_arg = poptGetOptArg(pc);
 618                         if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.tracefile_size) < 0) {
 619                                 ERR("Wrong value in --tracefile-size parameter: %s", opt_arg);
 620                                 ret = CMD_ERROR;
 621                                 goto end;
 622                         }
 623                         DBG("Maximum tracefile size set to %" PRIu64,
 624                                         chan_opts.attr.tracefile_size);
 625                         break;
 626                 case OPT_TRACEFILE_COUNT:
 627                 {
 628                         unsigned long v;
 629
 630                         errno = 0;
 631                         opt_arg = poptGetOptArg(pc);
 632                         v = strtoul(opt_arg, NULL, 0);
 633                         if (errno != 0 || !isdigit(opt_arg[0])) {
 634                                 ERR("Wrong value in --tracefile-count parameter: %s", opt_arg);
 635                                 ret = CMD_ERROR;
 636                                 goto end;
 637                         }
 638                         if (v != (uint32_t) v) {
 639                                 ERR("32-bit overflow in --tracefile-count parameter: %s", opt_arg);
 640                                 ret = CMD_ERROR;
 641                                 goto end;
 642                         }
 643                         chan_opts.attr.tracefile_count = (uint32_t) v;
 644                         DBG("Maximum tracefile count set to %" PRIu64,
 645                                         chan_opts.attr.tracefile_count);
 646                         break;
 647                 }
 648                 case OPT_LIST_OPTIONS:
 649                         list_cmd_options(stdout, long_options);
 650                         goto end;
 651                 default:
 652                         ret = CMD_UNDEFINED;
 653                         goto end;
 654                 }
 655         }
 656
 657         ret = print_missing_or_multiple_domains(opt_kernel + opt_userspace);
 658         if (ret) {
 659                 ret = CMD_ERROR;
 660                 goto end;
 661         }
 662
 663         if (chan_opts.attr.overwrite == 1 && opt_blocking_timeout.set &&
 664                         opt_blocking_timeout.value != 0) {
 665                 ERR("You cannot specify --overwrite and --blocking-timeout=N, "
 666                         "where N is different than 0");
 667                 ret = CMD_ERROR;
 668                 goto end;
 669         }
 670
 671         /* Mi check */
 672         if (lttng_opt_mi) {
 673                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 674                 if (!writer) {
 675                         ret = -LTTNG_ERR_NOMEM;
 676                         goto end;
 677                 }
 678
 679                 /* Open command element */
 680                 ret = mi_lttng_writer_command_open(writer,
 681                                 mi_lttng_element_command_enable_channels);
 682                 if (ret) {
 683                         ret = CMD_ERROR;
 684                         goto end;
 685                 }
 686
 687                 /* Open output element */
 688                 ret = mi_lttng_writer_open_element(writer,
 689                                 mi_lttng_element_command_output);
 690                 if (ret) {
 691                         ret = CMD_ERROR;
 692                         goto end;
 693                 }
 694         }
 695
 696         opt_channels = (char*) poptGetArg(pc);
 697         if (opt_channels == NULL) {
 698                 ERR("Missing channel name.\n");
 699                 ret = CMD_ERROR;
 700                 success = 0;
 701                 goto mi_closing;
 702         }
 703
 704         leftover = poptGetArg(pc);
 705         if (leftover) {
 706                 ERR("Unknown argument: %s", leftover);
 707                 ret = CMD_ERROR;
 708                 success = 0;
 709                 goto mi_closing;
 710         }
 711
 712         if (!opt_session_name) {
 713                 session_name = get_session_name();
 714                 if (session_name == NULL) {
 715                         command_ret = CMD_ERROR;
 716                         success = 0;
 717                         goto mi_closing;
 718                 }
 719         } else {
 720                 session_name = opt_session_name;
 721         }
 722
 723         command_ret = enable_channel(session_name);
 724         if (command_ret) {
 725                 success = 0;
 726         }
 727
 728 mi_closing:
 729         /* Mi closing */
 730         if (lttng_opt_mi) {
 731                 /* Close  output element */
 732                 ret = mi_lttng_writer_close_element(writer);
 733                 if (ret) {
 734                         goto end;
 735                 }
 736
 737                 /* Success ? */
 738                 ret = mi_lttng_writer_write_element_bool(writer,
 739                                 mi_lttng_element_command_success, success);
 740                 if (ret) {
 741                         goto end;
 742                 }
 743
 744                 /* Command element close */
 745                 ret = mi_lttng_writer_command_close(writer);
 746                 if (ret) {
 747                         goto end;
 748                 }
 749         }
 750
 751 end:
 752         /* Mi clean-up */
 753         if (writer && mi_lttng_writer_destroy(writer)) {
 754                 /* Preserve original error code */
 755                 ret = ret ? ret : LTTNG_ERR_MI_IO_FAIL;
 756         }
 757
 758         if (!opt_session_name && session_name) {
 759                 free(session_name);
 760         }
 761
 762         /* Overwrite ret if an error occurred when enable_channel */
 763         ret = command_ret ? command_ret : ret;
 764         poptFreeContext(pc);
 765         return ret;
 766 }