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 _GNU_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 char *opt_channels;
  39 static int opt_kernel;
  40 static char *opt_session_name;
  41 static int opt_userspace;
  42 static struct lttng_channel chan;
  43 static char *opt_output;
  44 static int opt_buffer_uid;
  45 static int opt_buffer_pid;
  46 static int opt_buffer_global;
  47
  48 static struct mi_writer *writer;
  49
  50 enum {
  51         OPT_HELP = 1,
  52         OPT_DISCARD,
  53         OPT_OVERWRITE,
  54         OPT_SUBBUF_SIZE,
  55         OPT_NUM_SUBBUF,
  56         OPT_SWITCH_TIMER,
  57         OPT_READ_TIMER,
  58         OPT_USERSPACE,
  59         OPT_LIST_OPTIONS,
  60         OPT_TRACEFILE_SIZE,
  61         OPT_TRACEFILE_COUNT,
  62 };
  63
  64 static struct lttng_handle *handle;
  65
  66 const char *output_mmap = "mmap";
  67 const char *output_splice = "splice";
  68
  69 static struct poptOption long_options[] = {
  70         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  71         {"help",           'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
  72         {"session",        's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
  73         {"kernel",         'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
  74         {"userspace",      'u', POPT_ARG_NONE, 0, OPT_USERSPACE, 0, 0},
  75         {"discard",        0,   POPT_ARG_NONE, 0, OPT_DISCARD, 0, 0},
  76         {"overwrite",      0,   POPT_ARG_NONE, 0, OPT_OVERWRITE, 0, 0},
  77         {"subbuf-size",    0,   POPT_ARG_STRING, 0, OPT_SUBBUF_SIZE, 0, 0},
  78         {"num-subbuf",     0,   POPT_ARG_INT, 0, OPT_NUM_SUBBUF, 0, 0},
  79         {"switch-timer",   0,   POPT_ARG_INT, 0, OPT_SWITCH_TIMER, 0, 0},
  80         {"read-timer",     0,   POPT_ARG_INT, 0, OPT_READ_TIMER, 0, 0},
  81         {"list-options",   0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  82         {"output",         0,   POPT_ARG_STRING, &opt_output, 0, 0, 0},
  83         {"buffers-uid",    0,   POPT_ARG_VAL, &opt_buffer_uid, 1, 0, 0},
  84         {"buffers-pid",    0,   POPT_ARG_VAL, &opt_buffer_pid, 1, 0, 0},
  85         {"buffers-global", 0,   POPT_ARG_VAL, &opt_buffer_global, 1, 0, 0},
  86         {"tracefile-size", 'C',   POPT_ARG_INT, 0, OPT_TRACEFILE_SIZE, 0, 0},
  87         {"tracefile-count", 'W',   POPT_ARG_INT, 0, OPT_TRACEFILE_COUNT, 0, 0},
  88         {0, 0, 0, 0, 0, 0, 0}
  89 };
  90
  91 /*
  92  * usage
  93  */
  94 static void usage(FILE *ofp)
  95 {
  96         fprintf(ofp, "usage: lttng enable-channel NAME[,NAME2,...] (-u | -k) [OPTIONS]\n");
  97         fprintf(ofp, "\n");
  98         fprintf(ofp, "Options:\n");
  99         fprintf(ofp, "  -h, --help               Show this help\n");
 100         fprintf(ofp, "      --list-options       Simple listing of options\n");
 101         fprintf(ofp, "  -s, --session NAME       Apply to session name\n");
 102         fprintf(ofp, "  -k, --kernel             Apply to the kernel tracer\n");
 103         fprintf(ofp, "  -u, --userspace          Apply to the user-space tracer\n");
 104         fprintf(ofp, "\n");
 105         fprintf(ofp, "Channel options:\n");
 106         fprintf(ofp, "      --discard            Discard event when buffers are full%s\n",
 107                 DEFAULT_CHANNEL_OVERWRITE ? "" : " (default)");
 108         fprintf(ofp, "      --overwrite          Flight recorder mode%s\n",
 109                 DEFAULT_CHANNEL_OVERWRITE ? " (default)" : "");
 110         fprintf(ofp, "      --subbuf-size SIZE   Subbuffer size in bytes {+k,+M,+G}\n");
 111         fprintf(ofp, "                               (default UST uid: %zu, UST pid: %zu, kernel: %zu, metadata: %zu)\n",
 112                 default_get_ust_uid_channel_subbuf_size(),
 113                 default_get_ust_pid_channel_subbuf_size(),
 114                 default_get_kernel_channel_subbuf_size(),
 115                 default_get_metadata_subbuf_size());
 116         fprintf(ofp, "                               Rounded up to the next power of 2.\n");
 117         fprintf(ofp, "      --num-subbuf NUM     Number of subbufers\n");
 118         fprintf(ofp, "                               (default UST uid: %u, UST pid: %u, kernel: %u, metadata: %u)\n",
 119                 DEFAULT_UST_UID_CHANNEL_SUBBUF_NUM, DEFAULT_UST_PID_CHANNEL_SUBBUF_NUM,
 120                 DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM, DEFAULT_METADATA_SUBBUF_NUM);
 121         fprintf(ofp, "                               Rounded up to the next power of 2.\n");
 122         fprintf(ofp, "      --switch-timer USEC  Switch timer interval in usec\n");
 123         fprintf(ofp, "                               (default UST uid: %u, UST pid: %u, kernel: %u, metadata: %u)\n",
 124                 DEFAULT_UST_UID_CHANNEL_SWITCH_TIMER, DEFAULT_UST_PID_CHANNEL_SWITCH_TIMER,
 125                 DEFAULT_KERNEL_CHANNEL_SWITCH_TIMER, DEFAULT_METADATA_SWITCH_TIMER);
 126         fprintf(ofp, "      --read-timer USEC    Read timer interval in usec.\n");
 127         fprintf(ofp, "                               (default UST uid: %u, UST pid: %u, kernel: %u, metadata: %u)\n",
 128                 DEFAULT_UST_UID_CHANNEL_READ_TIMER, DEFAULT_UST_UID_CHANNEL_READ_TIMER,
 129                 DEFAULT_KERNEL_CHANNEL_READ_TIMER, DEFAULT_METADATA_READ_TIMER);
 130         fprintf(ofp, "      --output TYPE        Channel output type (Values: %s, %s)\n",
 131                         output_mmap, output_splice);
 132         fprintf(ofp, "                               (default UST uid: %s, UST pid: %s, kernel: %s, metadata: %s)\n",
 133                         DEFAULT_UST_UID_CHANNEL_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice,
 134                         DEFAULT_UST_PID_CHANNEL_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice,
 135                         DEFAULT_KERNEL_CHANNEL_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice,
 136                         DEFAULT_METADATA_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice);
 137         fprintf(ofp, "      --buffers-uid        Use per UID buffer (-u only)\n");
 138         fprintf(ofp, "      --buffers-pid        Use per PID buffer (-u only)\n");
 139         fprintf(ofp, "      --buffers-global     Use shared buffer for the whole system (-k only)\n");
 140         fprintf(ofp, "  -C, --tracefile-size SIZE\n");
 141         fprintf(ofp, "                           Maximum size of each tracefile within a stream (in bytes). 0 means unlimited.\n");
 142         fprintf(ofp, "                               (default: %u)\n", DEFAULT_CHANNEL_TRACEFILE_SIZE);
 143         fprintf(ofp, "                           Note: traces generated with this option may inaccurately report\n");
 144         fprintf(ofp, "                           discarded events as per CTF 1.8.\n");
 145         fprintf(ofp, "  -W, --tracefile-count COUNT\n");
 146         fprintf(ofp, "                           Used in conjunction with -C option, this will limit the number\n");
 147         fprintf(ofp, "                           of files created to the specified count. 0 means unlimited.\n");
 148         fprintf(ofp, "                               (default: %u)\n", DEFAULT_CHANNEL_TRACEFILE_COUNT);
 149         fprintf(ofp, "\n");
 150 }
 151
 152 /*
 153  * Set default attributes depending on those already defined from the command
 154  * line.
 155  */
 156 static void set_default_attr(struct lttng_domain *dom)
 157 {
 158         struct lttng_channel_attr default_attr;
 159
 160         /* Set attributes */
 161         lttng_channel_set_default_attr(dom, &default_attr);
 162
 163         if (chan.attr.overwrite == -1) {
 164                 chan.attr.overwrite = default_attr.overwrite;
 165         }
 166         if (chan.attr.subbuf_size == -1) {
 167                 chan.attr.subbuf_size = default_attr.subbuf_size;
 168         }
 169         if (chan.attr.num_subbuf == -1) {
 170                 chan.attr.num_subbuf = default_attr.num_subbuf;
 171         }
 172         if (chan.attr.switch_timer_interval == -1) {
 173                 chan.attr.switch_timer_interval = default_attr.switch_timer_interval;
 174         }
 175         if (chan.attr.read_timer_interval == -1) {
 176                 chan.attr.read_timer_interval = default_attr.read_timer_interval;
 177         }
 178         if ((int) chan.attr.output == -1) {
 179                 chan.attr.output = default_attr.output;
 180         }
 181         if (chan.attr.tracefile_count == -1) {
 182                 chan.attr.tracefile_count = default_attr.tracefile_count;
 183         }
 184         if (chan.attr.tracefile_size == -1) {
 185                 chan.attr.tracefile_size = default_attr.tracefile_size;
 186         }
 187 }
 188
 189 /*
 190  * Adding channel using the lttng API.
 191  */
 192 static int enable_channel(char *session_name)
 193 {
 194         int ret = CMD_SUCCESS, warn = 0, error = 0, success = 0;
 195         char *channel_name;
 196         struct lttng_domain dom;
 197
 198         memset(&dom, 0, sizeof(dom));
 199
 200         /* Create lttng domain */
 201         if (opt_kernel) {
 202                 dom.type = LTTNG_DOMAIN_KERNEL;
 203                 dom.buf_type = LTTNG_BUFFER_GLOBAL;
 204                 if (opt_buffer_uid || opt_buffer_pid) {
 205                         ERR("Buffer type not supported for domain -k");
 206                         ret = CMD_ERROR;
 207                         goto error;
 208                 }
 209         } else if (opt_userspace) {
 210                 dom.type = LTTNG_DOMAIN_UST;
 211                 if (opt_buffer_pid) {
 212                         dom.buf_type = LTTNG_BUFFER_PER_PID;
 213                 } else {
 214                         if (opt_buffer_global) {
 215                                 ERR("Buffer type not supported for domain -u");
 216                                 ret = CMD_ERROR;
 217                                 goto error;
 218                         }
 219                         dom.buf_type = LTTNG_BUFFER_PER_UID;
 220                 }
 221         } else {
 222                 print_missing_domain();
 223                 ret = CMD_ERROR;
 224                 goto error;
 225         }
 226
 227         set_default_attr(&dom);
 228
 229         if (chan.attr.tracefile_size == 0 && chan.attr.tracefile_count) {
 230                 ERR("Missing option --tracefile-size. "
 231                                 "A file count without a size won't do anything.");
 232                 ret = CMD_ERROR;
 233                 goto error;
 234         }
 235
 236         if ((chan.attr.tracefile_size > 0) &&
 237                         (chan.attr.tracefile_size < chan.attr.subbuf_size)) {
 238                 WARN("Tracefile size rounded up from (%" PRIu64 ") to subbuffer size (%" PRIu64 ")",
 239                                 chan.attr.tracefile_size, chan.attr.subbuf_size);
 240                 chan.attr.tracefile_size = chan.attr.subbuf_size;
 241         }
 242
 243         /* Setting channel output */
 244         if (opt_output) {
 245                 if (!strncmp(output_mmap, opt_output, strlen(output_mmap))) {
 246                         chan.attr.output = LTTNG_EVENT_MMAP;
 247                 } else if (!strncmp(output_splice, opt_output, strlen(output_splice))) {
 248                         chan.attr.output = LTTNG_EVENT_SPLICE;
 249                 } else {
 250                         ERR("Unknown output type %s. Possible values are: %s, %s\n",
 251                                         opt_output, output_mmap, output_splice);
 252                         usage(stderr);
 253                         ret = CMD_ERROR;
 254                         goto error;
 255                 }
 256         }
 257
 258         handle = lttng_create_handle(session_name, &dom);
 259         if (handle == NULL) {
 260                 ret = -1;
 261                 goto error;
 262         }
 263
 264         /* Mi open channels element */
 265         if (lttng_opt_mi) {
 266                 assert(writer);
 267                 ret = mi_lttng_channels_open(writer);
 268                 if (ret) {
 269                         ret = CMD_ERROR;
 270                         goto error;
 271                 }
 272         }
 273
 274         /* Strip channel list (format: chan1,chan2,...) */
 275         channel_name = strtok(opt_channels, ",");
 276         while (channel_name != NULL) {
 277                 /* Copy channel name and normalize it */
 278                 strncpy(chan.name, channel_name, NAME_MAX);
 279                 chan.name[NAME_MAX - 1] = '\0';
 280
 281                 DBG("Enabling channel %s", channel_name);
 282
 283                 ret = lttng_enable_channel(handle, &chan);
 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                         default:
 295                                 ERR("Channel %s: %s (session %s)", channel_name,
 296                                                 lttng_strerror(ret), session_name);
 297                                 error = 1;
 298                                 break;
 299                         }
 300                 } else {
 301                         MSG("%s channel %s enabled for session %s",
 302                                         get_domain_str(dom.type), channel_name, session_name);
 303                         success = 1;
 304                 }
 305
 306                 if (lttng_opt_mi) {
 307                         /* Mi print the channel element and leave it open */
 308                         ret = mi_lttng_channel(writer, &chan, 1);
 309                         if (ret) {
 310                                 ret = CMD_ERROR;
 311                                 goto error;
 312                         }
 313
 314                         /* Individual Success ? */
 315                         ret = mi_lttng_writer_write_element_bool(writer,
 316                                         mi_lttng_element_command_success, success);
 317                         if (ret) {
 318                                 ret = CMD_ERROR;
 319                                 goto error;
 320                         }
 321
 322                         /* Close channel element */
 323                         ret = mi_lttng_writer_close_element(writer);
 324                         if (ret) {
 325                                 ret = CMD_ERROR;
 326                                 goto error;
 327                         }
 328                 }
 329
 330                 /* Next channel */
 331                 channel_name = strtok(NULL, ",");
 332         }
 333
 334         if (lttng_opt_mi) {
 335                 /* Close channels element */
 336                 ret = mi_lttng_writer_close_element(writer);
 337                 if (ret) {
 338                         ret = CMD_ERROR;
 339                         goto error;
 340                 }
 341         }
 342
 343         ret = CMD_SUCCESS;
 344
 345 error:
 346         /* If more important error happen bypass the warning */
 347         if (!ret && warn) {
 348                 ret = CMD_WARNING;
 349         }
 350         /* If more important error happen bypass the warning */
 351         if (!ret && error) {
 352                 ret = CMD_ERROR;
 353         }
 354
 355         lttng_destroy_handle(handle);
 356
 357         return ret;
 358 }
 359
 360 /*
 361  * Default value for channel configuration.
 362  */
 363 static void init_channel_config(void)
 364 {
 365         /*
 366          * Put -1 everywhere so we can identify those set by the command line and
 367          * those needed to be set by the default values.
 368          */
 369         memset(&chan.attr, -1, sizeof(chan.attr));
 370 }
 371
 372 /*
 373  * Add channel to trace session
 374  */
 375 int cmd_enable_channels(int argc, const char **argv)
 376 {
 377         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 378         static poptContext pc;
 379         char *session_name = NULL;
 380         char *opt_arg = NULL;
 381
 382         init_channel_config();
 383
 384         pc = poptGetContext(NULL, argc, argv, long_options, 0);
 385         poptReadDefaultConfig(pc, 0);
 386
 387         while ((opt = poptGetNextOpt(pc)) != -1) {
 388                 switch (opt) {
 389                 case OPT_HELP:
 390                         usage(stdout);
 391                         goto end;
 392                 case OPT_DISCARD:
 393                         chan.attr.overwrite = 0;
 394                         DBG("Channel set to discard");
 395                         break;
 396                 case OPT_OVERWRITE:
 397                         chan.attr.overwrite = 1;
 398                         DBG("Channel set to overwrite");
 399                         break;
 400                 case OPT_SUBBUF_SIZE:
 401                 {
 402                         uint64_t rounded_size;
 403                         int order;
 404
 405                         /* Parse the size */
 406                         opt_arg = poptGetOptArg(pc);
 407                         if (utils_parse_size_suffix(opt_arg, &chan.attr.subbuf_size) < 0 || !chan.attr.subbuf_size) {
 408                                 ERR("Wrong value in --subbuf-size parameter: %s", opt_arg);
 409                                 ret = CMD_ERROR;
 410                                 goto end;
 411                         }
 412
 413                         order = get_count_order_u64(chan.attr.subbuf_size);
 414                         assert(order >= 0);
 415                         rounded_size = 1ULL << order;
 416                         if (rounded_size < chan.attr.subbuf_size) {
 417                                 ERR("The subbuf size (%" PRIu64 ") is rounded and overflows!",
 418                                                 chan.attr.subbuf_size);
 419                                 ret = CMD_ERROR;
 420                                 goto end;
 421                         }
 422
 423                         if (rounded_size != chan.attr.subbuf_size) {
 424                                 WARN("The subbuf size (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 425                                                 chan.attr.subbuf_size, rounded_size);
 426                                 chan.attr.subbuf_size = rounded_size;
 427                         }
 428
 429                         /* Should now be power of 2 */
 430                         assert(!((chan.attr.subbuf_size - 1) & chan.attr.subbuf_size));
 431
 432                         DBG("Channel subbuf size set to %" PRIu64, chan.attr.subbuf_size);
 433                         break;
 434                 }
 435                 case OPT_NUM_SUBBUF:
 436                 {
 437                         uint64_t rounded_size;
 438                         int order;
 439
 440                         errno = 0;
 441                         opt_arg = poptGetOptArg(pc);
 442                         chan.attr.num_subbuf = strtoull(opt_arg, NULL, 0);
 443                         if (errno != 0 || !chan.attr.num_subbuf || !isdigit(opt_arg[0])) {
 444                                 ERR("Wrong value in --num-subbuf parameter: %s", opt_arg);
 445                                 ret = CMD_ERROR;
 446                                 goto end;
 447                         }
 448
 449                         order = get_count_order_u64(chan.attr.num_subbuf);
 450                         assert(order >= 0);
 451                         rounded_size = 1ULL << order;
 452                         if (rounded_size < chan.attr.num_subbuf) {
 453                                 ERR("The number of subbuffers (%" PRIu64 ") is rounded and overflows!",
 454                                                 chan.attr.num_subbuf);
 455                                 ret = CMD_ERROR;
 456                                 goto end;
 457                         }
 458
 459                         if (rounded_size != chan.attr.num_subbuf) {
 460                                 WARN("The number of subbuffers (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 461                                                 chan.attr.num_subbuf, rounded_size);
 462                                 chan.attr.num_subbuf = rounded_size;
 463                         }
 464
 465                         /* Should now be power of 2 */
 466                         assert(!((chan.attr.num_subbuf - 1) & chan.attr.num_subbuf));
 467
 468                         DBG("Channel subbuf num set to %" PRIu64, chan.attr.num_subbuf);
 469                         break;
 470                 }
 471                 case OPT_SWITCH_TIMER:
 472                 {
 473                         unsigned long v;
 474
 475                         errno = 0;
 476                         opt_arg = poptGetOptArg(pc);
 477                         v = strtoul(opt_arg, NULL, 0);
 478                         if (errno != 0 || !isdigit(opt_arg[0])) {
 479                                 ERR("Wrong value in --switch-timer parameter: %s", opt_arg);
 480                                 ret = CMD_ERROR;
 481                                 goto end;
 482                         }
 483                         if (v != (uint32_t) v) {
 484                                 ERR("32-bit overflow in --switch-timer parameter: %s", opt_arg);
 485                                 ret = CMD_ERROR;
 486                                 goto end;
 487                         }
 488                         chan.attr.switch_timer_interval = (uint32_t) v;
 489                         DBG("Channel switch timer interval set to %d", chan.attr.switch_timer_interval);
 490                         break;
 491                 }
 492                 case OPT_READ_TIMER:
 493                 {
 494                         unsigned long v;
 495
 496                         errno = 0;
 497                         opt_arg = poptGetOptArg(pc);
 498                         v = strtoul(opt_arg, NULL, 0);
 499                         if (errno != 0 || !isdigit(opt_arg[0])) {
 500                                 ERR("Wrong value in --read-timer parameter: %s", opt_arg);
 501                                 ret = CMD_ERROR;
 502                                 goto end;
 503                         }
 504                         if (v != (uint32_t) v) {
 505                                 ERR("32-bit overflow in --read-timer parameter: %s", opt_arg);
 506                                 ret = CMD_ERROR;
 507                                 goto end;
 508                         }
 509                         chan.attr.read_timer_interval = (uint32_t) v;
 510                         DBG("Channel read timer interval set to %d", chan.attr.read_timer_interval);
 511                         break;
 512                 }
 513                 case OPT_USERSPACE:
 514                         opt_userspace = 1;
 515                         break;
 516                 case OPT_TRACEFILE_SIZE:
 517                         opt_arg = poptGetOptArg(pc);
 518                         if (utils_parse_size_suffix(opt_arg, &chan.attr.tracefile_size) < 0) {
 519                                 ERR("Wrong value in --tracefile-size parameter: %s", opt_arg);
 520                                 ret = CMD_ERROR;
 521                                 goto end;
 522                         }
 523                         DBG("Maximum tracefile size set to %" PRIu64,
 524                                         chan.attr.tracefile_size);
 525                         break;
 526                 case OPT_TRACEFILE_COUNT:
 527                 {
 528                         unsigned long v;
 529
 530                         errno = 0;
 531                         opt_arg = poptGetOptArg(pc);
 532                         v = strtoul(opt_arg, NULL, 0);
 533                         if (errno != 0 || !isdigit(opt_arg[0])) {
 534                                 ERR("Wrong value in --tracefile-count parameter: %s", opt_arg);
 535                                 ret = CMD_ERROR;
 536                                 goto end;
 537                         }
 538                         if (v != (uint32_t) v) {
 539                                 ERR("32-bit overflow in --tracefile-count parameter: %s", opt_arg);
 540                                 ret = CMD_ERROR;
 541                                 goto end;
 542                         }
 543                         chan.attr.tracefile_count = (uint32_t) v;
 544                         DBG("Maximum tracefile count set to %" PRIu64,
 545                                         chan.attr.tracefile_count);
 546                         break;
 547                 }
 548                 case OPT_LIST_OPTIONS:
 549                         list_cmd_options(stdout, long_options);
 550                         goto end;
 551                 default:
 552                         usage(stderr);
 553                         ret = CMD_UNDEFINED;
 554                         goto end;
 555                 }
 556         }
 557
 558         /* Mi check */
 559         if (lttng_opt_mi) {
 560                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 561                 if (!writer) {
 562                         ret = -LTTNG_ERR_NOMEM;
 563                         goto end;
 564                 }
 565
 566                 /* Open command element */
 567                 ret = mi_lttng_writer_command_open(writer,
 568                                 mi_lttng_element_command_enable_channels);
 569                 if (ret) {
 570                         ret = CMD_ERROR;
 571                         goto end;
 572                 }
 573
 574                 /* Open output element */
 575                 ret = mi_lttng_writer_open_element(writer,
 576                                 mi_lttng_element_command_output);
 577                 if (ret) {
 578                         ret = CMD_ERROR;
 579                         goto end;
 580                 }
 581         }
 582
 583         opt_channels = (char*) poptGetArg(pc);
 584         if (opt_channels == NULL) {
 585                 ERR("Missing channel name.\n");
 586                 usage(stderr);
 587                 ret = CMD_ERROR;
 588                 success = 0;
 589                 goto mi_closing;
 590         }
 591
 592         if (!opt_session_name) {
 593                 session_name = get_session_name();
 594                 if (session_name == NULL) {
 595                         command_ret = CMD_ERROR;
 596                         success = 0;
 597                         goto mi_closing;
 598                 }
 599         } else {
 600                 session_name = opt_session_name;
 601         }
 602
 603         command_ret = enable_channel(session_name);
 604         if (command_ret) {
 605                 success = 0;
 606         }
 607
 608 mi_closing:
 609         /* Mi closing */
 610         if (lttng_opt_mi) {
 611                 /* Close  output element */
 612                 ret = mi_lttng_writer_close_element(writer);
 613                 if (ret) {
 614                         goto end;
 615                 }
 616
 617                 /* Success ? */
 618                 ret = mi_lttng_writer_write_element_bool(writer,
 619                                 mi_lttng_element_command_success, success);
 620                 if (ret) {
 621                         goto end;
 622                 }
 623
 624                 /* Command element close */
 625                 ret = mi_lttng_writer_command_close(writer);
 626                 if (ret) {
 627                         goto end;
 628                 }
 629         }
 630
 631 end:
 632         /* Mi clean-up */
 633         if (writer && mi_lttng_writer_destroy(writer)) {
 634                 /* Preserve original error code */
 635                 ret = ret ? ret : LTTNG_ERR_MI_IO_FAIL;
 636         }
 637
 638         if (!opt_session_name && session_name) {
 639                 free(session_name);
 640         }
 641
 642         /* Overwrite ret if an error occurred when enable_channel */
 643         ret = command_ret ? command_ret : ret;
 644         poptFreeContext(pc);
 645         return ret;
 646 }