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 #define _LGPL_SOURCE
  20 #include <popt.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/stat.h>
  25 #include <sys/types.h>
  26 #include <unistd.h>
  27 #include <inttypes.h>
  28 #include <assert.h>
  29 #include <ctype.h>
  30
  31 #include <common/sessiond-comm/sessiond-comm.h>
  32 #include <common/utils.h>
  33 #include <common/mi-lttng.h>
  34
  35 #include "../command.h"
  36 #include "../utils.h"
  37
  38
  39 static char *opt_channels;
  40 static int opt_kernel;
  41 static char *opt_session_name;
  42 static int opt_userspace;
  43 static struct lttng_channel chan;
  44 static char *opt_output;
  45 static int opt_buffer_uid;
  46 static int opt_buffer_pid;
  47 static int opt_buffer_global;
  48
  49 static struct mi_writer *writer;
  50
  51 enum {
  52         OPT_HELP = 1,
  53         OPT_DISCARD,
  54         OPT_OVERWRITE,
  55         OPT_SUBBUF_SIZE,
  56         OPT_NUM_SUBBUF,
  57         OPT_SWITCH_TIMER,
  58         OPT_READ_TIMER,
  59         OPT_USERSPACE,
  60         OPT_LIST_OPTIONS,
  61         OPT_TRACEFILE_SIZE,
  62         OPT_TRACEFILE_COUNT,
  63 };
  64
  65 static struct lttng_handle *handle;
  66
  67 const char *output_mmap = "mmap";
  68 const char *output_splice = "splice";
  69
  70 static struct poptOption long_options[] = {
  71         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  72         {"help",           'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
  73         {"session",        's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
  74         {"kernel",         'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
  75         {"userspace",      'u', POPT_ARG_NONE, 0, OPT_USERSPACE, 0, 0},
  76         {"discard",        0,   POPT_ARG_NONE, 0, OPT_DISCARD, 0, 0},
  77         {"overwrite",      0,   POPT_ARG_NONE, 0, OPT_OVERWRITE, 0, 0},
  78         {"subbuf-size",    0,   POPT_ARG_STRING, 0, OPT_SUBBUF_SIZE, 0, 0},
  79         {"num-subbuf",     0,   POPT_ARG_INT, 0, OPT_NUM_SUBBUF, 0, 0},
  80         {"switch-timer",   0,   POPT_ARG_INT, 0, OPT_SWITCH_TIMER, 0, 0},
  81         {"read-timer",     0,   POPT_ARG_INT, 0, OPT_READ_TIMER, 0, 0},
  82         {"list-options",   0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  83         {"output",         0,   POPT_ARG_STRING, &opt_output, 0, 0, 0},
  84         {"buffers-uid",    0,   POPT_ARG_VAL, &opt_buffer_uid, 1, 0, 0},
  85         {"buffers-pid",    0,   POPT_ARG_VAL, &opt_buffer_pid, 1, 0, 0},
  86         {"buffers-global", 0,   POPT_ARG_VAL, &opt_buffer_global, 1, 0, 0},
  87         {"tracefile-size", 'C',   POPT_ARG_INT, 0, OPT_TRACEFILE_SIZE, 0, 0},
  88         {"tracefile-count", 'W',   POPT_ARG_INT, 0, OPT_TRACEFILE_COUNT, 0, 0},
  89         {0, 0, 0, 0, 0, 0, 0}
  90 };
  91
  92 /*
  93  * usage
  94  */
  95 static void usage(FILE *ofp)
  96 {
  97         fprintf(ofp, "usage: lttng enable-channel NAME[,NAME2,...] (-u | -k) [OPTIONS]\n");
  98         fprintf(ofp, "\n");
  99         fprintf(ofp, "Options:\n");
 100         fprintf(ofp, "  -h, --help               Show this help\n");
 101         fprintf(ofp, "      --list-options       Simple listing of options\n");
 102         fprintf(ofp, "  -s, --session NAME       Apply to session name\n");
 103         fprintf(ofp, "  -k, --kernel             Apply to the kernel tracer\n");
 104         fprintf(ofp, "  -u, --userspace          Apply to the user-space tracer\n");
 105         fprintf(ofp, "\n");
 106         fprintf(ofp, "Channel options:\n");
 107         fprintf(ofp, "      --discard            Discard event when buffers are full%s\n",
 108                 DEFAULT_CHANNEL_OVERWRITE ? "" : " (default)");
 109         fprintf(ofp, "      --overwrite          Flight recorder mode%s\n",
 110                 DEFAULT_CHANNEL_OVERWRITE ? " (default)" : "");
 111         fprintf(ofp, "      --subbuf-size SIZE   Subbuffer size in bytes {+k,+M,+G}\n");
 112         fprintf(ofp, "                               (default UST uid: %zu, UST pid: %zu, kernel: %zu, metadata: %zu)\n",
 113                 default_get_ust_uid_channel_subbuf_size(),
 114                 default_get_ust_pid_channel_subbuf_size(),
 115                 default_get_kernel_channel_subbuf_size(),
 116                 default_get_metadata_subbuf_size());
 117         fprintf(ofp, "                               Rounded up to the next power of 2.\n");
 118         fprintf(ofp, "      --num-subbuf NUM     Number of subbufers\n");
 119         fprintf(ofp, "                               (default UST uid: %u, UST pid: %u, kernel: %u, metadata: %u)\n",
 120                 DEFAULT_UST_UID_CHANNEL_SUBBUF_NUM, DEFAULT_UST_PID_CHANNEL_SUBBUF_NUM,
 121                 DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM, DEFAULT_METADATA_SUBBUF_NUM);
 122         fprintf(ofp, "                               Rounded up to the next power of 2.\n");
 123         fprintf(ofp, "      --switch-timer USEC  Switch timer interval in usec\n");
 124         fprintf(ofp, "                               (default UST uid: %u, UST pid: %u, kernel: %u, metadata: %u)\n",
 125                 DEFAULT_UST_UID_CHANNEL_SWITCH_TIMER, DEFAULT_UST_PID_CHANNEL_SWITCH_TIMER,
 126                 DEFAULT_KERNEL_CHANNEL_SWITCH_TIMER, DEFAULT_METADATA_SWITCH_TIMER);
 127         fprintf(ofp, "      --read-timer USEC    Read timer interval in usec.\n");
 128         fprintf(ofp, "                               (default UST uid: %u, UST pid: %u, kernel: %u, metadata: %u)\n",
 129                 DEFAULT_UST_UID_CHANNEL_READ_TIMER, DEFAULT_UST_UID_CHANNEL_READ_TIMER,
 130                 DEFAULT_KERNEL_CHANNEL_READ_TIMER, DEFAULT_METADATA_READ_TIMER);
 131         fprintf(ofp, "      --output TYPE        Channel output type (Values: %s, %s)\n",
 132                         output_mmap, output_splice);
 133         fprintf(ofp, "                               (default UST uid: %s, UST pid: %s, kernel: %s, metadata: %s)\n",
 134                         DEFAULT_UST_UID_CHANNEL_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice,
 135                         DEFAULT_UST_PID_CHANNEL_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice,
 136                         DEFAULT_KERNEL_CHANNEL_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice,
 137                         DEFAULT_METADATA_OUTPUT == LTTNG_EVENT_MMAP ? output_mmap : output_splice);
 138         fprintf(ofp, "      --buffers-uid        Use per UID buffer (-u only)\n");
 139         fprintf(ofp, "      --buffers-pid        Use per PID buffer (-u only)\n");
 140         fprintf(ofp, "      --buffers-global     Use shared buffer for the whole system (-k only)\n");
 141         fprintf(ofp, "  -C, --tracefile-size SIZE\n");
 142         fprintf(ofp, "                           Maximum size of each tracefile within a stream (in bytes). 0 means unlimited.\n");
 143         fprintf(ofp, "                               (default: %u)\n", DEFAULT_CHANNEL_TRACEFILE_SIZE);
 144         fprintf(ofp, "                           Note: traces generated with this option may inaccurately report\n");
 145         fprintf(ofp, "                           discarded events as per CTF 1.8.\n");
 146         fprintf(ofp, "  -W, --tracefile-count COUNT\n");
 147         fprintf(ofp, "                           Used in conjunction with -C option, this will limit the number\n");
 148         fprintf(ofp, "                           of files created to the specified count. 0 means unlimited.\n");
 149         fprintf(ofp, "                               (default: %u)\n", DEFAULT_CHANNEL_TRACEFILE_COUNT);
 150         fprintf(ofp, "\n");
 151 }
 152
 153 /*
 154  * Set default attributes depending on those already defined from the command
 155  * line.
 156  */
 157 static void set_default_attr(struct lttng_domain *dom)
 158 {
 159         struct lttng_channel_attr default_attr;
 160
 161         /* Set attributes */
 162         lttng_channel_set_default_attr(dom, &default_attr);
 163
 164         if (chan.attr.overwrite == -1) {
 165                 chan.attr.overwrite = default_attr.overwrite;
 166         }
 167         if (chan.attr.subbuf_size == -1) {
 168                 chan.attr.subbuf_size = default_attr.subbuf_size;
 169         }
 170         if (chan.attr.num_subbuf == -1) {
 171                 chan.attr.num_subbuf = default_attr.num_subbuf;
 172         }
 173         if (chan.attr.switch_timer_interval == -1) {
 174                 chan.attr.switch_timer_interval = default_attr.switch_timer_interval;
 175         }
 176         if (chan.attr.read_timer_interval == -1) {
 177                 chan.attr.read_timer_interval = default_attr.read_timer_interval;
 178         }
 179         if ((int) chan.attr.output == -1) {
 180                 chan.attr.output = default_attr.output;
 181         }
 182         if (chan.attr.tracefile_count == -1) {
 183                 chan.attr.tracefile_count = default_attr.tracefile_count;
 184         }
 185         if (chan.attr.tracefile_size == -1) {
 186                 chan.attr.tracefile_size = default_attr.tracefile_size;
 187         }
 188 }
 189
 190 /*
 191  * Adding channel using the lttng API.
 192  */
 193 static int enable_channel(char *session_name)
 194 {
 195         int ret = CMD_SUCCESS, warn = 0, error = 0, success = 0;
 196         char *channel_name;
 197         struct lttng_domain dom;
 198
 199         memset(&dom, 0, sizeof(dom));
 200
 201         /* Create lttng domain */
 202         if (opt_kernel) {
 203                 dom.type = LTTNG_DOMAIN_KERNEL;
 204                 dom.buf_type = LTTNG_BUFFER_GLOBAL;
 205                 if (opt_buffer_uid || opt_buffer_pid) {
 206                         ERR("Buffer type not supported for domain -k");
 207                         ret = CMD_ERROR;
 208                         goto error;
 209                 }
 210         } else if (opt_userspace) {
 211                 dom.type = LTTNG_DOMAIN_UST;
 212                 if (opt_buffer_pid) {
 213                         dom.buf_type = LTTNG_BUFFER_PER_PID;
 214                 } else {
 215                         if (opt_buffer_global) {
 216                                 ERR("Buffer type not supported for domain -u");
 217                                 ret = CMD_ERROR;
 218                                 goto error;
 219                         }
 220                         dom.buf_type = LTTNG_BUFFER_PER_UID;
 221                 }
 222         } else {
 223                 print_missing_domain();
 224                 ret = CMD_ERROR;
 225                 goto error;
 226         }
 227
 228         set_default_attr(&dom);
 229
 230         if (chan.attr.tracefile_size == 0 && chan.attr.tracefile_count) {
 231                 ERR("Missing option --tracefile-size. "
 232                                 "A file count without a size won't do anything.");
 233                 ret = CMD_ERROR;
 234                 goto error;
 235         }
 236
 237         if ((chan.attr.tracefile_size > 0) &&
 238                         (chan.attr.tracefile_size < chan.attr.subbuf_size)) {
 239                 WARN("Tracefile size rounded up from (%" PRIu64 ") to subbuffer size (%" PRIu64 ")",
 240                                 chan.attr.tracefile_size, chan.attr.subbuf_size);
 241                 chan.attr.tracefile_size = chan.attr.subbuf_size;
 242         }
 243
 244         /* Setting channel output */
 245         if (opt_output) {
 246                 if (!strncmp(output_mmap, opt_output, strlen(output_mmap))) {
 247                         chan.attr.output = LTTNG_EVENT_MMAP;
 248                 } else if (!strncmp(output_splice, opt_output, strlen(output_splice))) {
 249                         chan.attr.output = LTTNG_EVENT_SPLICE;
 250                 } else {
 251                         ERR("Unknown output type %s. Possible values are: %s, %s\n",
 252                                         opt_output, output_mmap, output_splice);
 253                         usage(stderr);
 254                         ret = CMD_ERROR;
 255                         goto error;
 256                 }
 257         }
 258
 259         handle = lttng_create_handle(session_name, &dom);
 260         if (handle == NULL) {
 261                 ret = -1;
 262                 goto error;
 263         }
 264
 265         /* Mi open channels element */
 266         if (lttng_opt_mi) {
 267                 assert(writer);
 268                 ret = mi_lttng_channels_open(writer);
 269                 if (ret) {
 270                         ret = CMD_ERROR;
 271                         goto error;
 272                 }
 273         }
 274
 275         /* Strip channel list (format: chan1,chan2,...) */
 276         channel_name = strtok(opt_channels, ",");
 277         while (channel_name != NULL) {
 278                 /* Copy channel name and normalize it */
 279                 strncpy(chan.name, channel_name, NAME_MAX);
 280                 chan.name[NAME_MAX - 1] = '\0';
 281
 282                 DBG("Enabling channel %s", channel_name);
 283
 284                 ret = lttng_enable_channel(handle, &chan);
 285                 if (ret < 0) {
 286                         success = 0;
 287                         switch (-ret) {
 288                         case LTTNG_ERR_KERN_CHAN_EXIST:
 289                         case LTTNG_ERR_UST_CHAN_EXIST:
 290                         case LTTNG_ERR_CHAN_EXIST:
 291                                 WARN("Channel %s: %s (session %s)", channel_name,
 292                                                 lttng_strerror(ret), session_name);
 293                                 warn = 1;
 294                                 break;
 295                         default:
 296                                 ERR("Channel %s: %s (session %s)", channel_name,
 297                                                 lttng_strerror(ret), session_name);
 298                                 error = 1;
 299                                 break;
 300                         }
 301                 } else {
 302                         MSG("%s channel %s enabled for session %s",
 303                                         get_domain_str(dom.type), channel_name, session_name);
 304                         success = 1;
 305                 }
 306
 307                 if (lttng_opt_mi) {
 308                         /* Mi print the channel element and leave it open */
 309                         ret = mi_lttng_channel(writer, &chan, 1);
 310                         if (ret) {
 311                                 ret = CMD_ERROR;
 312                                 goto error;
 313                         }
 314
 315                         /* Individual Success ? */
 316                         ret = mi_lttng_writer_write_element_bool(writer,
 317                                         mi_lttng_element_command_success, success);
 318                         if (ret) {
 319                                 ret = CMD_ERROR;
 320                                 goto error;
 321                         }
 322
 323                         /* Close channel element */
 324                         ret = mi_lttng_writer_close_element(writer);
 325                         if (ret) {
 326                                 ret = CMD_ERROR;
 327                                 goto error;
 328                         }
 329                 }
 330
 331                 /* Next channel */
 332                 channel_name = strtok(NULL, ",");
 333         }
 334
 335         if (lttng_opt_mi) {
 336                 /* Close channels element */
 337                 ret = mi_lttng_writer_close_element(writer);
 338                 if (ret) {
 339                         ret = CMD_ERROR;
 340                         goto error;
 341                 }
 342         }
 343
 344         ret = CMD_SUCCESS;
 345
 346 error:
 347         /* If more important error happen bypass the warning */
 348         if (!ret && warn) {
 349                 ret = CMD_WARNING;
 350         }
 351         /* If more important error happen bypass the warning */
 352         if (!ret && error) {
 353                 ret = CMD_ERROR;
 354         }
 355
 356         lttng_destroy_handle(handle);
 357
 358         return ret;
 359 }
 360
 361 /*
 362  * Default value for channel configuration.
 363  */
 364 static void init_channel_config(void)
 365 {
 366         /*
 367          * Put -1 everywhere so we can identify those set by the command line and
 368          * those needed to be set by the default values.
 369          */
 370         memset(&chan.attr, -1, sizeof(chan.attr));
 371 }
 372
 373 /*
 374  * Add channel to trace session
 375  */
 376 int cmd_enable_channels(int argc, const char **argv)
 377 {
 378         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 379         static poptContext pc;
 380         char *session_name = NULL;
 381         char *opt_arg = NULL;
 382
 383         init_channel_config();
 384
 385         pc = poptGetContext(NULL, argc, argv, long_options, 0);
 386         poptReadDefaultConfig(pc, 0);
 387
 388         while ((opt = poptGetNextOpt(pc)) != -1) {
 389                 switch (opt) {
 390                 case OPT_HELP:
 391                         usage(stdout);
 392                         goto end;
 393                 case OPT_DISCARD:
 394                         chan.attr.overwrite = 0;
 395                         DBG("Channel set to discard");
 396                         break;
 397                 case OPT_OVERWRITE:
 398                         chan.attr.overwrite = 1;
 399                         DBG("Channel set to overwrite");
 400                         break;
 401                 case OPT_SUBBUF_SIZE:
 402                 {
 403                         uint64_t rounded_size;
 404                         int order;
 405
 406                         /* Parse the size */
 407                         opt_arg = poptGetOptArg(pc);
 408                         if (utils_parse_size_suffix(opt_arg, &chan.attr.subbuf_size) < 0 || !chan.attr.subbuf_size) {
 409                                 ERR("Wrong value in --subbuf-size parameter: %s", opt_arg);
 410                                 ret = CMD_ERROR;
 411                                 goto end;
 412                         }
 413
 414                         order = get_count_order_u64(chan.attr.subbuf_size);
 415                         assert(order >= 0);
 416                         rounded_size = 1ULL << order;
 417                         if (rounded_size < chan.attr.subbuf_size) {
 418                                 ERR("The subbuf size (%" PRIu64 ") is rounded and overflows!",
 419                                                 chan.attr.subbuf_size);
 420                                 ret = CMD_ERROR;
 421                                 goto end;
 422                         }
 423
 424                         if (rounded_size != chan.attr.subbuf_size) {
 425                                 WARN("The subbuf size (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 426                                                 chan.attr.subbuf_size, rounded_size);
 427                                 chan.attr.subbuf_size = rounded_size;
 428                         }
 429
 430                         /* Should now be power of 2 */
 431                         assert(!((chan.attr.subbuf_size - 1) & chan.attr.subbuf_size));
 432
 433                         DBG("Channel subbuf size set to %" PRIu64, chan.attr.subbuf_size);
 434                         break;
 435                 }
 436                 case OPT_NUM_SUBBUF:
 437                 {
 438                         uint64_t rounded_size;
 439                         int order;
 440
 441                         errno = 0;
 442                         opt_arg = poptGetOptArg(pc);
 443                         chan.attr.num_subbuf = strtoull(opt_arg, NULL, 0);
 444                         if (errno != 0 || !chan.attr.num_subbuf || !isdigit(opt_arg[0])) {
 445                                 ERR("Wrong value in --num-subbuf parameter: %s", opt_arg);
 446                                 ret = CMD_ERROR;
 447                                 goto end;
 448                         }
 449
 450                         order = get_count_order_u64(chan.attr.num_subbuf);
 451                         assert(order >= 0);
 452                         rounded_size = 1ULL << order;
 453                         if (rounded_size < chan.attr.num_subbuf) {
 454                                 ERR("The number of subbuffers (%" PRIu64 ") is rounded and overflows!",
 455                                                 chan.attr.num_subbuf);
 456                                 ret = CMD_ERROR;
 457                                 goto end;
 458                         }
 459
 460                         if (rounded_size != chan.attr.num_subbuf) {
 461                                 WARN("The number of subbuffers (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 462                                                 chan.attr.num_subbuf, rounded_size);
 463                                 chan.attr.num_subbuf = rounded_size;
 464                         }
 465
 466                         /* Should now be power of 2 */
 467                         assert(!((chan.attr.num_subbuf - 1) & chan.attr.num_subbuf));
 468
 469                         DBG("Channel subbuf num set to %" PRIu64, chan.attr.num_subbuf);
 470                         break;
 471                 }
 472                 case OPT_SWITCH_TIMER:
 473                 {
 474                         unsigned long v;
 475
 476                         errno = 0;
 477                         opt_arg = poptGetOptArg(pc);
 478                         v = strtoul(opt_arg, NULL, 0);
 479                         if (errno != 0 || !isdigit(opt_arg[0])) {
 480                                 ERR("Wrong value in --switch-timer parameter: %s", opt_arg);
 481                                 ret = CMD_ERROR;
 482                                 goto end;
 483                         }
 484                         if (v != (uint32_t) v) {
 485                                 ERR("32-bit overflow in --switch-timer parameter: %s", opt_arg);
 486                                 ret = CMD_ERROR;
 487                                 goto end;
 488                         }
 489                         chan.attr.switch_timer_interval = (uint32_t) v;
 490                         DBG("Channel switch timer interval set to %d", chan.attr.switch_timer_interval);
 491                         break;
 492                 }
 493                 case OPT_READ_TIMER:
 494                 {
 495                         unsigned long v;
 496
 497                         errno = 0;
 498                         opt_arg = poptGetOptArg(pc);
 499                         v = strtoul(opt_arg, NULL, 0);
 500                         if (errno != 0 || !isdigit(opt_arg[0])) {
 501                                 ERR("Wrong value in --read-timer parameter: %s", opt_arg);
 502                                 ret = CMD_ERROR;
 503                                 goto end;
 504                         }
 505                         if (v != (uint32_t) v) {
 506                                 ERR("32-bit overflow in --read-timer parameter: %s", opt_arg);
 507                                 ret = CMD_ERROR;
 508                                 goto end;
 509                         }
 510                         chan.attr.read_timer_interval = (uint32_t) v;
 511                         DBG("Channel read timer interval set to %d", chan.attr.read_timer_interval);
 512                         break;
 513                 }
 514                 case OPT_USERSPACE:
 515                         opt_userspace = 1;
 516                         break;
 517                 case OPT_TRACEFILE_SIZE:
 518                         opt_arg = poptGetOptArg(pc);
 519                         if (utils_parse_size_suffix(opt_arg, &chan.attr.tracefile_size) < 0) {
 520                                 ERR("Wrong value in --tracefile-size parameter: %s", opt_arg);
 521                                 ret = CMD_ERROR;
 522                                 goto end;
 523                         }
 524                         DBG("Maximum tracefile size set to %" PRIu64,
 525                                         chan.attr.tracefile_size);
 526                         break;
 527                 case OPT_TRACEFILE_COUNT:
 528                 {
 529                         unsigned long v;
 530
 531                         errno = 0;
 532                         opt_arg = poptGetOptArg(pc);
 533                         v = strtoul(opt_arg, NULL, 0);
 534                         if (errno != 0 || !isdigit(opt_arg[0])) {
 535                                 ERR("Wrong value in --tracefile-count parameter: %s", opt_arg);
 536                                 ret = CMD_ERROR;
 537                                 goto end;
 538                         }
 539                         if (v != (uint32_t) v) {
 540                                 ERR("32-bit overflow in --tracefile-count parameter: %s", opt_arg);
 541                                 ret = CMD_ERROR;
 542                                 goto end;
 543                         }
 544                         chan.attr.tracefile_count = (uint32_t) v;
 545                         DBG("Maximum tracefile count set to %" PRIu64,
 546                                         chan.attr.tracefile_count);
 547                         break;
 548                 }
 549                 case OPT_LIST_OPTIONS:
 550                         list_cmd_options(stdout, long_options);
 551                         goto end;
 552                 default:
 553                         usage(stderr);
 554                         ret = CMD_UNDEFINED;
 555                         goto end;
 556                 }
 557         }
 558
 559         /* Mi check */
 560         if (lttng_opt_mi) {
 561                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 562                 if (!writer) {
 563                         ret = -LTTNG_ERR_NOMEM;
 564                         goto end;
 565                 }
 566
 567                 /* Open command element */
 568                 ret = mi_lttng_writer_command_open(writer,
 569                                 mi_lttng_element_command_enable_channels);
 570                 if (ret) {
 571                         ret = CMD_ERROR;
 572                         goto end;
 573                 }
 574
 575                 /* Open output element */
 576                 ret = mi_lttng_writer_open_element(writer,
 577                                 mi_lttng_element_command_output);
 578                 if (ret) {
 579                         ret = CMD_ERROR;
 580                         goto end;
 581                 }
 582         }
 583
 584         opt_channels = (char*) poptGetArg(pc);
 585         if (opt_channels == NULL) {
 586                 ERR("Missing channel name.\n");
 587                 usage(stderr);
 588                 ret = CMD_ERROR;
 589                 success = 0;
 590                 goto mi_closing;
 591         }
 592
 593         if (!opt_session_name) {
 594                 session_name = get_session_name();
 595                 if (session_name == NULL) {
 596                         command_ret = CMD_ERROR;
 597                         success = 0;
 598                         goto mi_closing;
 599                 }
 600         } else {
 601                 session_name = opt_session_name;
 602         }
 603
 604         command_ret = enable_channel(session_name);
 605         if (command_ret) {
 606                 success = 0;
 607         }
 608
 609 mi_closing:
 610         /* Mi closing */
 611         if (lttng_opt_mi) {
 612                 /* Close  output element */
 613                 ret = mi_lttng_writer_close_element(writer);
 614                 if (ret) {
 615                         goto end;
 616                 }
 617
 618                 /* Success ? */
 619                 ret = mi_lttng_writer_write_element_bool(writer,
 620                                 mi_lttng_element_command_success, success);
 621                 if (ret) {
 622                         goto end;
 623                 }
 624
 625                 /* Command element close */
 626                 ret = mi_lttng_writer_command_close(writer);
 627                 if (ret) {
 628                         goto end;
 629                 }
 630         }
 631
 632 end:
 633         /* Mi clean-up */
 634         if (writer && mi_lttng_writer_destroy(writer)) {
 635                 /* Preserve original error code */
 636                 ret = ret ? ret : LTTNG_ERR_MI_IO_FAIL;
 637         }
 638
 639         if (!opt_session_name && session_name) {
 640                 free(session_name);
 641         }
 642
 643         /* Overwrite ret if an error occurred when enable_channel */
 644         ret = command_ret ? command_ret : ret;
 645         poptFreeContext(pc);
 646         return ret;
 647 }