src/lib/lttng-ctl/lttng-ctl.c

   1 /*
   2  * liblttngctl.c
   3  *
   4  * Linux Trace Toolkit Control Library
   5  *
   6  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define _GNU_SOURCE
  24 #include <grp.h>
  25 #include <errno.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <unistd.h>
  30
  31 #include <common/common.h>
  32 #include <common/defaults.h>
  33 #include <common/sessiond-comm/sessiond-comm.h>
  34 #include <lttng/lttng.h>
  35
  36 /* Socket to session daemon for communication */
  37 static int sessiond_socket;
  38 static char sessiond_sock_path[PATH_MAX];
  39
  40 /* Variables */
  41 static char *tracing_group;
  42 static int connected;
  43
  44 /*
  45  * Copy string from src to dst and enforce null terminated byte.
  46  */
  47 static void copy_string(char *dst, const char *src, size_t len)
  48 {
  49         if (src && dst) {
  50                 strncpy(dst, src, len);
  51                 /* Enforce the NULL terminated byte */
  52                 dst[len - 1] = '\0';
  53         } else if (dst) {
  54                 dst[0] = '\0';
  55         }
  56 }
  57
  58 /*
  59  * Copy domain to lttcomm_session_msg domain.
  60  *
  61  * If domain is unknown, default domain will be the kernel.
  62  */
  63 static void copy_lttng_domain(struct lttng_domain *dst, struct lttng_domain *src)
  64 {
  65         if (src && dst) {
  66                 switch (src->type) {
  67                         case LTTNG_DOMAIN_KERNEL:
  68                         case LTTNG_DOMAIN_UST:
  69                         /*
  70                         case LTTNG_DOMAIN_UST_EXEC_NAME:
  71                         case LTTNG_DOMAIN_UST_PID:
  72                         case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
  73                         */
  74                                 memcpy(dst, src, sizeof(struct lttng_domain));
  75                                 break;
  76                         default:
  77                                 dst->type = LTTNG_DOMAIN_KERNEL;
  78                                 break;
  79                 }
  80         }
  81 }
  82
  83 /*
  84  * Send lttcomm_session_msg to the session daemon.
  85  *
  86  * On success, returns the number of bytes sent (>=0)
  87  * On error, returns -1
  88  */
  89 static int send_session_msg(struct lttcomm_session_msg *lsm)
  90 {
  91         int ret;
  92
  93         if (!connected) {
  94                 ret = -ENOTCONN;
  95                 goto end;
  96         }
  97
  98         ret = lttcomm_send_creds_unix_sock(sessiond_socket, lsm,
  99                         sizeof(struct lttcomm_session_msg));
 100
 101 end:
 102         return ret;
 103 }
 104
 105 /*
 106  * Receive data from the sessiond socket.
 107  *
 108  * On success, returns the number of bytes received (>=0)
 109  * On error, returns -1 (recvmsg() error) or -ENOTCONN
 110  */
 111 static int recv_data_sessiond(void *buf, size_t len)
 112 {
 113         int ret;
 114
 115         if (!connected) {
 116                 ret = -ENOTCONN;
 117                 goto end;
 118         }
 119
 120         ret = lttcomm_recv_unix_sock(sessiond_socket, buf, len);
 121
 122 end:
 123         return ret;
 124 }
 125
 126 /*
 127  *  Check if we are in the specified group.
 128  *
 129  *  If yes return 1, else return -1.
 130  */
 131 static int check_tracing_group(const char *grp_name)
 132 {
 133         struct group *grp_tracing;      /* no free(). See getgrnam(3) */
 134         gid_t *grp_list;
 135         int grp_list_size, grp_id, i;
 136         int ret = -1;
 137
 138         /* Get GID of group 'tracing' */
 139         grp_tracing = getgrnam(grp_name);
 140         if (grp_tracing == NULL) {
 141                 /* NULL means not found also. getgrnam(3) */
 142                 if (errno != 0) {
 143                         perror("getgrnam");
 144                 }
 145                 goto end;
 146         }
 147
 148         /* Get number of supplementary group IDs */
 149         grp_list_size = getgroups(0, NULL);
 150         if (grp_list_size < 0) {
 151                 perror("getgroups");
 152                 goto end;
 153         }
 154
 155         /* Alloc group list of the right size */
 156         grp_list = malloc(grp_list_size * sizeof(gid_t));
 157         if (!grp_list) {
 158                 perror("malloc");
 159                 goto end;
 160         }
 161         grp_id = getgroups(grp_list_size, grp_list);
 162         if (grp_id < 0) {
 163                 perror("getgroups");
 164                 goto free_list;
 165         }
 166
 167         for (i = 0; i < grp_list_size; i++) {
 168                 if (grp_list[i] == grp_tracing->gr_gid) {
 169                         ret = 1;
 170                         break;
 171                 }
 172         }
 173
 174 free_list:
 175         free(grp_list);
 176
 177 end:
 178         return ret;
 179 }
 180
 181 /*
 182  * Try connect to session daemon with sock_path.
 183  *
 184  * Return 0 on success, else -1
 185  */
 186 static int try_connect_sessiond(const char *sock_path)
 187 {
 188         int ret;
 189
 190         /* If socket exist, we check if the daemon listens for connect. */
 191         ret = access(sock_path, F_OK);
 192         if (ret < 0) {
 193                 /* Not alive */
 194                 return -1;
 195         }
 196
 197         ret = lttcomm_connect_unix_sock(sock_path);
 198         if (ret < 0) {
 199                 /* Not alive */
 200                 return -1;
 201         }
 202
 203         ret = lttcomm_close_unix_sock(ret);
 204         if (ret < 0) {
 205                 perror("lttcomm_close_unix_sock");
 206         }
 207
 208         return 0;
 209 }
 210
 211 /*
 212  * Set sessiond socket path by putting it in the global
 213  * sessiond_sock_path variable.
 214  * Returns 0 on success,
 215  * -ENOMEM on failure (the sessiond socket path is somehow too long)
 216  */
 217 static int set_session_daemon_path(void)
 218 {
 219         int ret;
 220         int in_tgroup = 0;      /* In tracing group */
 221         uid_t uid;
 222
 223         uid = getuid();
 224
 225         if (uid != 0) {
 226                 /* Are we in the tracing group ? */
 227                 in_tgroup = check_tracing_group(tracing_group);
 228         }
 229
 230         if ((uid == 0) || in_tgroup) {
 231                 copy_string(sessiond_sock_path, DEFAULT_GLOBAL_CLIENT_UNIX_SOCK,
 232                                 sizeof(sessiond_sock_path));
 233         }
 234
 235         if (uid != 0) {
 236                 if (in_tgroup) {
 237                         /* Tracing group */
 238                         ret = try_connect_sessiond(sessiond_sock_path);
 239                         if (ret >= 0) {
 240                                 goto end;
 241                         }
 242                         /* Global session daemon not available... */
 243                 }
 244                 /* ...or not in tracing group (and not root), default */
 245
 246                 /*
 247                  * With GNU C <  2.1, snprintf returns -1 if the target buffer is too small;
 248                  * With GNU C >= 2.1, snprintf returns the required size (excluding closing null)
 249                  */
 250                 ret = snprintf(sessiond_sock_path, sizeof(sessiond_sock_path),
 251                                 DEFAULT_HOME_CLIENT_UNIX_SOCK, getenv("HOME"));
 252                 if ((ret < 0) || (ret >= sizeof(sessiond_sock_path))) {
 253                         return -ENOMEM;
 254                 }
 255         }
 256 end:
 257         return 0;
 258 }
 259
 260 /*
 261  *  Connect to the LTTng session daemon.
 262  *
 263  *  On success, return 0. On error, return -1.
 264  */
 265 static int connect_sessiond(void)
 266 {
 267         int ret;
 268
 269         ret = set_session_daemon_path();
 270         if (ret < 0) {
 271                 return -1; /* set_session_daemon_path() returns -ENOMEM */
 272         }
 273
 274         /* Connect to the sesssion daemon */
 275         ret = lttcomm_connect_unix_sock(sessiond_sock_path);
 276         if (ret < 0) {
 277                 return ret;
 278         }
 279
 280         sessiond_socket = ret;
 281         connected = 1;
 282
 283         return 0;
 284 }
 285
 286 /*
 287  *  Clean disconnect from the session daemon.
 288  *  On success, return 0. On error, return -1.
 289  */
 290 static int disconnect_sessiond(void)
 291 {
 292         int ret = 0;
 293
 294         if (connected) {
 295                 ret = lttcomm_close_unix_sock(sessiond_socket);
 296                 sessiond_socket = 0;
 297                 connected = 0;
 298         }
 299
 300         return ret;
 301 }
 302
 303 /*
 304  * Ask the session daemon a specific command and put the data into buf.
 305  *
 306  * Return size of data (only payload, not header) or a negative error code.
 307  */
 308 static int ask_sessiond(struct lttcomm_session_msg *lsm, void **buf)
 309 {
 310         int ret;
 311         size_t size;
 312         void *data = NULL;
 313         struct lttcomm_lttng_msg llm;
 314
 315         ret = connect_sessiond();
 316         if (ret < 0) {
 317                 goto end;
 318         }
 319
 320         /* Send command to session daemon */
 321         ret = send_session_msg(lsm);
 322         if (ret < 0) {
 323                 goto end;
 324         }
 325
 326         /* Get header from data transmission */
 327         ret = recv_data_sessiond(&llm, sizeof(llm));
 328         if (ret < 0) {
 329                 goto end;
 330         }
 331
 332         /* Check error code if OK */
 333         if (llm.ret_code != LTTCOMM_OK) {
 334                 ret = -llm.ret_code;
 335                 goto end;
 336         }
 337
 338         size = llm.data_size;
 339         if (size == 0) {
 340                 /* If client free with size 0 */
 341                 if (buf != NULL) {
 342                         *buf = NULL;
 343                 }
 344                 ret = 0;
 345                 goto end;
 346         }
 347
 348         data = (void*) malloc(size);
 349
 350         /* Get payload data */
 351         ret = recv_data_sessiond(data, size);
 352         if (ret < 0) {
 353                 free(data);
 354                 goto end;
 355         }
 356
 357         /*
 358          * Extra protection not to dereference a NULL pointer. If buf is NULL at
 359          * this point, an error is returned and data is freed.
 360          */
 361         if (buf == NULL) {
 362                 ret = -1;
 363                 free(data);
 364                 goto end;
 365         }
 366
 367         *buf = data;
 368         ret = size;
 369
 370 end:
 371         disconnect_sessiond();
 372         return ret;
 373 }
 374
 375 /*
 376  * Create lttng handle and return pointer.
 377  * The returned pointer will be NULL in case of malloc() error.
 378  */
 379 struct lttng_handle *lttng_create_handle(const char *session_name,
 380                 struct lttng_domain *domain)
 381 {
 382         struct lttng_handle *handle;
 383
 384         handle = malloc(sizeof(struct lttng_handle));
 385         if (handle == NULL) {
 386                 perror("malloc handle");
 387                 goto end;
 388         }
 389
 390         /* Copy session name */
 391         copy_string(handle->session_name, session_name,
 392                         sizeof(handle->session_name));
 393
 394         /* Copy lttng domain */
 395         copy_lttng_domain(&handle->domain, domain);
 396
 397 end:
 398         return handle;
 399 }
 400
 401 /*
 402  * Destroy handle by free(3) the pointer.
 403  */
 404 void lttng_destroy_handle(struct lttng_handle *handle)
 405 {
 406         if (handle) {
 407                 free(handle);
 408         }
 409 }
 410
 411 /*
 412  * Register an outside consumer.
 413  * Returns size of returned session payload data or a negative error code.
 414  */
 415 int lttng_register_consumer(struct lttng_handle *handle,
 416                 const char *socket_path)
 417 {
 418         struct lttcomm_session_msg lsm;
 419
 420         lsm.cmd_type = LTTNG_REGISTER_CONSUMER;
 421         copy_string(lsm.session.name, handle->session_name,
 422                         sizeof(lsm.session.name));
 423         copy_lttng_domain(&lsm.domain, &handle->domain);
 424
 425         copy_string(lsm.u.reg.path, socket_path, sizeof(lsm.u.reg.path));
 426
 427         return ask_sessiond(&lsm, NULL);
 428 }
 429
 430 /*
 431  *  Start tracing for all traces of the session.
 432  *  Returns size of returned session payload data or a negative error code.
 433  */
 434 int lttng_start_tracing(const char *session_name)
 435 {
 436         struct lttcomm_session_msg lsm;
 437
 438         if (session_name == NULL) {
 439                 return -1;
 440         }
 441
 442         lsm.cmd_type = LTTNG_START_TRACE;
 443
 444         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 445
 446         return ask_sessiond(&lsm, NULL);
 447 }
 448
 449 /*
 450  *  Stop tracing for all traces of the session.
 451  *  Returns size of returned session payload data or a negative error code.
 452  */
 453 int lttng_stop_tracing(const char *session_name)
 454 {
 455         struct lttcomm_session_msg lsm;
 456
 457         if (session_name == NULL) {
 458                 return -1;
 459         }
 460
 461         lsm.cmd_type = LTTNG_STOP_TRACE;
 462
 463         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 464
 465         return ask_sessiond(&lsm, NULL);
 466 }
 467
 468 /*
 469  * Add context to event or/and channel.
 470  *
 471  * Returns the size of the returned payload data or a negative error code.
 472  */
 473 int lttng_add_context(struct lttng_handle *handle,
 474                 struct lttng_event_context *ctx, const char *event_name,
 475                 const char *channel_name)
 476 {
 477         struct lttcomm_session_msg lsm;
 478
 479         /* Safety check. Both are mandatory */
 480         if (handle == NULL || ctx == NULL) {
 481                 return -1;
 482         }
 483
 484         lsm.cmd_type = LTTNG_ADD_CONTEXT;
 485
 486         /* Copy channel name */
 487         copy_string(lsm.u.context.channel_name, channel_name,
 488                         sizeof(lsm.u.context.channel_name));
 489         /* Copy event name */
 490         copy_string(lsm.u.context.event_name, event_name,
 491                         sizeof(lsm.u.context.event_name));
 492
 493         copy_lttng_domain(&lsm.domain, &handle->domain);
 494
 495         memcpy(&lsm.u.context.ctx, ctx, sizeof(struct lttng_event_context));
 496
 497         copy_string(lsm.session.name, handle->session_name,
 498                         sizeof(lsm.session.name));
 499
 500         return ask_sessiond(&lsm, NULL);
 501 }
 502
 503 /*
 504  *  Enable event(s) for a channel.
 505  *  If no event name is specified, all events are enabled.
 506  *  If no channel name is specified, the default 'channel0' is used.
 507  *  Returns size of returned session payload data or a negative error code.
 508  */
 509 int lttng_enable_event(struct lttng_handle *handle,
 510                 struct lttng_event *ev, const char *channel_name)
 511 {
 512         struct lttcomm_session_msg lsm;
 513
 514         if (handle == NULL || ev == NULL) {
 515                 return -1;
 516         }
 517
 518         /* If no channel name, we put the default name */
 519         if (channel_name == NULL) {
 520                 copy_string(lsm.u.enable.channel_name, DEFAULT_CHANNEL_NAME,
 521                                 sizeof(lsm.u.enable.channel_name));
 522         } else {
 523                 copy_string(lsm.u.enable.channel_name, channel_name,
 524                                 sizeof(lsm.u.enable.channel_name));
 525         }
 526
 527         copy_lttng_domain(&lsm.domain, &handle->domain);
 528
 529         if (ev->name[0] != '\0') {
 530                 lsm.cmd_type = LTTNG_ENABLE_EVENT;
 531         } else {
 532                 lsm.cmd_type = LTTNG_ENABLE_ALL_EVENT;
 533         }
 534         memcpy(&lsm.u.enable.event, ev, sizeof(lsm.u.enable.event));
 535
 536         copy_string(lsm.session.name, handle->session_name,
 537                         sizeof(lsm.session.name));
 538
 539         return ask_sessiond(&lsm, NULL);
 540 }
 541
 542 /*
 543  *  Disable event(s) of a channel and domain.
 544  *  If no event name is specified, all events are disabled.
 545  *  If no channel name is specified, the default 'channel0' is used.
 546  *  Returns size of returned session payload data or a negative error code.
 547  */
 548 int lttng_disable_event(struct lttng_handle *handle, const char *name,
 549                 const char *channel_name)
 550 {
 551         struct lttcomm_session_msg lsm;
 552
 553         if (handle == NULL) {
 554                 return -1;
 555         }
 556
 557         if (channel_name) {
 558                 copy_string(lsm.u.disable.channel_name, channel_name,
 559                                 sizeof(lsm.u.disable.channel_name));
 560         } else {
 561                 copy_string(lsm.u.disable.channel_name, DEFAULT_CHANNEL_NAME,
 562                                 sizeof(lsm.u.disable.channel_name));
 563         }
 564
 565         copy_lttng_domain(&lsm.domain, &handle->domain);
 566
 567         if (name != NULL) {
 568                 copy_string(lsm.u.disable.name, name, sizeof(lsm.u.disable.name));
 569                 lsm.cmd_type = LTTNG_DISABLE_EVENT;
 570         } else {
 571                 lsm.cmd_type = LTTNG_DISABLE_ALL_EVENT;
 572         }
 573
 574         copy_string(lsm.session.name, handle->session_name,
 575                         sizeof(lsm.session.name));
 576
 577         return ask_sessiond(&lsm, NULL);
 578 }
 579
 580 /*
 581  *  Enable channel per domain
 582  *  Returns size of returned session payload data or a negative error code.
 583  */
 584 int lttng_enable_channel(struct lttng_handle *handle,
 585                 struct lttng_channel *chan)
 586 {
 587         struct lttcomm_session_msg lsm;
 588
 589         /*
 590          * NULL arguments are forbidden. No default values.
 591          */
 592         if (handle == NULL || chan == NULL) {
 593                 return -1;
 594         }
 595
 596         memcpy(&lsm.u.channel.chan, chan, sizeof(lsm.u.channel.chan));
 597
 598         lsm.cmd_type = LTTNG_ENABLE_CHANNEL;
 599
 600         copy_lttng_domain(&lsm.domain, &handle->domain);
 601
 602         copy_string(lsm.session.name, handle->session_name,
 603                         sizeof(lsm.session.name));
 604
 605         return ask_sessiond(&lsm, NULL);
 606 }
 607
 608 /*
 609  *  All tracing will be stopped for registered events of the channel.
 610  *  Returns size of returned session payload data or a negative error code.
 611  */
 612 int lttng_disable_channel(struct lttng_handle *handle, const char *name)
 613 {
 614         struct lttcomm_session_msg lsm;
 615
 616         /* Safety check. Both are mandatory */
 617         if (handle == NULL || name == NULL) {
 618                 return -1;
 619         }
 620
 621         lsm.cmd_type = LTTNG_DISABLE_CHANNEL;
 622
 623         copy_string(lsm.u.disable.channel_name, name,
 624                         sizeof(lsm.u.disable.channel_name));
 625
 626         copy_lttng_domain(&lsm.domain, &handle->domain);
 627
 628         copy_string(lsm.session.name, handle->session_name,
 629                         sizeof(lsm.session.name));
 630
 631         return ask_sessiond(&lsm, NULL);
 632 }
 633
 634 /*
 635  *  Lists all available tracepoints of domain.
 636  *  Sets the contents of the events array.
 637  *  Returns the number of lttng_event entries in events;
 638  *  on error, returns a negative value.
 639  */
 640 int lttng_list_tracepoints(struct lttng_handle *handle,
 641                 struct lttng_event **events)
 642 {
 643         int ret;
 644         struct lttcomm_session_msg lsm;
 645
 646         if (handle == NULL) {
 647                 return -1;
 648         }
 649
 650         lsm.cmd_type = LTTNG_LIST_TRACEPOINTS;
 651         copy_lttng_domain(&lsm.domain, &handle->domain);
 652
 653         ret = ask_sessiond(&lsm, (void **) events);
 654         if (ret < 0) {
 655                 return ret;
 656         }
 657
 658         return ret / sizeof(struct lttng_event);
 659 }
 660
 661 /*
 662  *  Returns a human readable string describing
 663  *  the error code (a negative value).
 664  */
 665 const char *lttng_strerror(int code)
 666 {
 667         /* lttcomm error codes range from -LTTCOMM_OK down to -LTTCOMM_NR */
 668         if (code > -LTTCOMM_OK) {
 669                 return "Ended with errors";
 670         }
 671
 672         return lttcomm_get_readable_code(code);
 673 }
 674
 675 /*
 676  *  Create a brand new session using name and path.
 677  *  Returns size of returned session payload data or a negative error code.
 678  */
 679 int lttng_create_session(const char *name, const char *path)
 680 {
 681         struct lttcomm_session_msg lsm;
 682
 683         lsm.cmd_type = LTTNG_CREATE_SESSION;
 684         copy_string(lsm.session.name, name, sizeof(lsm.session.name));
 685         copy_string(lsm.session.path, path, sizeof(lsm.session.path));
 686
 687         return ask_sessiond(&lsm, NULL);
 688 }
 689
 690 /*
 691  *  Destroy session using name.
 692  *  Returns size of returned session payload data or a negative error code.
 693  */
 694 int lttng_destroy_session(const char *session_name)
 695 {
 696         struct lttcomm_session_msg lsm;
 697
 698         if (session_name == NULL) {
 699                 return -1;
 700         }
 701
 702         lsm.cmd_type = LTTNG_DESTROY_SESSION;
 703
 704         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 705
 706         return ask_sessiond(&lsm, NULL);
 707 }
 708
 709 /*
 710  *  Ask the session daemon for all available sessions.
 711  *  Sets the contents of the sessions array.
 712  *  Returns the number of lttng_session entries in sessions;
 713  *  on error, returns a negative value.
 714  */
 715 int lttng_list_sessions(struct lttng_session **sessions)
 716 {
 717         int ret;
 718         struct lttcomm_session_msg lsm;
 719
 720         lsm.cmd_type = LTTNG_LIST_SESSIONS;
 721         ret = ask_sessiond(&lsm, (void**) sessions);
 722         if (ret < 0) {
 723                 return ret;
 724         }
 725
 726         return ret / sizeof(struct lttng_session);
 727 }
 728
 729 /*
 730  *  Ask the session daemon for all available domains of a session.
 731  *  Sets the contents of the domains array.
 732  *  Returns the number of lttng_domain entries in domains;
 733  *  on error, returns a negative value.
 734  */
 735 int lttng_list_domains(const char *session_name,
 736                 struct lttng_domain **domains)
 737 {
 738         int ret;
 739         struct lttcomm_session_msg lsm;
 740
 741         if (session_name == NULL) {
 742                 return -1;
 743         }
 744
 745         lsm.cmd_type = LTTNG_LIST_DOMAINS;
 746
 747         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 748
 749         ret = ask_sessiond(&lsm, (void**) domains);
 750         if (ret < 0) {
 751                 return ret;
 752         }
 753
 754         return ret / sizeof(struct lttng_domain);
 755 }
 756
 757 /*
 758  *  Ask the session daemon for all available channels of a session.
 759  *  Sets the contents of the channels array.
 760  *  Returns the number of lttng_channel entries in channels;
 761  *  on error, returns a negative value.
 762  */
 763 int lttng_list_channels(struct lttng_handle *handle,
 764                 struct lttng_channel **channels)
 765 {
 766         int ret;
 767         struct lttcomm_session_msg lsm;
 768
 769         if (handle == NULL) {
 770                 return -1;
 771         }
 772
 773         lsm.cmd_type = LTTNG_LIST_CHANNELS;
 774         copy_string(lsm.session.name, handle->session_name,
 775                         sizeof(lsm.session.name));
 776
 777         copy_lttng_domain(&lsm.domain, &handle->domain);
 778
 779         ret = ask_sessiond(&lsm, (void**) channels);
 780         if (ret < 0) {
 781                 return ret;
 782         }
 783
 784         return ret / sizeof(struct lttng_channel);
 785 }
 786
 787 /*
 788  *  Ask the session daemon for all available events of a session channel.
 789  *  Sets the contents of the events array.
 790  *  Returns the number of lttng_event entries in events;
 791  *  on error, returns a negative value.
 792  */
 793 int lttng_list_events(struct lttng_handle *handle,
 794                 const char *channel_name, struct lttng_event **events)
 795 {
 796         int ret;
 797         struct lttcomm_session_msg lsm;
 798
 799         /* Safety check. An handle and channel name are mandatory */
 800         if (handle == NULL || channel_name == NULL) {
 801                 return -1;
 802         }
 803
 804         lsm.cmd_type = LTTNG_LIST_EVENTS;
 805         copy_string(lsm.session.name, handle->session_name,
 806                         sizeof(lsm.session.name));
 807         copy_string(lsm.u.list.channel_name, channel_name,
 808                         sizeof(lsm.u.list.channel_name));
 809
 810         copy_lttng_domain(&lsm.domain, &handle->domain);
 811
 812         ret = ask_sessiond(&lsm, (void**) events);
 813         if (ret < 0) {
 814                 return ret;
 815         }
 816
 817         return ret / sizeof(struct lttng_event);
 818 }
 819
 820 /*
 821  * Sets the tracing_group variable with name.
 822  * This function allocates memory pointed to by tracing_group.
 823  * On success, returns 0, on error, returns -1 (null name) or -ENOMEM.
 824  */
 825 int lttng_set_tracing_group(const char *name)
 826 {
 827         if (name == NULL) {
 828                 return -1;
 829         }
 830
 831         if (asprintf(&tracing_group, "%s", name) < 0) {
 832                 return -ENOMEM;
 833         }
 834
 835         return 0;
 836 }
 837
 838 /*
 839  * Returns size of returned session payload data or a negative error code.
 840  */
 841 int lttng_calibrate(struct lttng_handle *handle,
 842                 struct lttng_calibrate *calibrate)
 843 {
 844         struct lttcomm_session_msg lsm;
 845
 846         /* Safety check. NULL pointer are forbidden */
 847         if (handle == NULL || calibrate == NULL) {
 848                 return -1;
 849         }
 850
 851         lsm.cmd_type = LTTNG_CALIBRATE;
 852         copy_lttng_domain(&lsm.domain, &handle->domain);
 853
 854         memcpy(&lsm.u.calibrate, calibrate, sizeof(lsm.u.calibrate));
 855
 856         return ask_sessiond(&lsm, NULL);
 857 }
 858
 859 /*
 860  * Set default channel attributes.
 861  * If either or both of the arguments are null, nothing happens.
 862  */
 863 void lttng_channel_set_default_attr(struct lttng_domain *domain,
 864                 struct lttng_channel_attr *attr)
 865 {
 866         /* Safety check */
 867         if (attr == NULL || domain == NULL) {
 868                 return;
 869         }
 870
 871         switch (domain->type) {
 872         case LTTNG_DOMAIN_KERNEL:
 873                 attr->overwrite = DEFAULT_CHANNEL_OVERWRITE;
 874                 attr->switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
 875                 attr->read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
 876
 877                 attr->subbuf_size = DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE;
 878                 attr->num_subbuf = DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM;
 879                 attr->output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
 880                 break;
 881         case LTTNG_DOMAIN_UST:
 882 #if 0
 883         case LTTNG_DOMAIN_UST_EXEC_NAME:
 884         case LTTNG_DOMAIN_UST_PID:
 885         case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
 886 #endif
 887                 attr->overwrite = DEFAULT_CHANNEL_OVERWRITE;
 888                 attr->switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
 889                 attr->read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
 890
 891                 attr->subbuf_size = DEFAULT_UST_CHANNEL_SUBBUF_SIZE;
 892                 attr->num_subbuf = DEFAULT_UST_CHANNEL_SUBBUF_NUM;
 893                 attr->output = DEFAULT_UST_CHANNEL_OUTPUT;
 894                 break;
 895         default:
 896                 /* Default behavior */
 897                 memset(attr, 0, sizeof(struct lttng_channel_attr));
 898                 break;
 899         }
 900 }
 901
 902 /*
 903  * Check if session daemon is alive.
 904  *
 905  * Return 1 if alive or 0 if not.
 906  * On error returns a negative value.
 907  */
 908 int lttng_session_daemon_alive(void)
 909 {
 910         int ret;
 911
 912         ret = set_session_daemon_path();
 913         if (ret < 0) {
 914                 /* Error */
 915                 return ret;
 916         }
 917
 918         if (strlen(sessiond_sock_path) == 0) {
 919                 /* No socket path set. Weird error */
 920                 return -1;
 921         }
 922
 923         ret = try_connect_sessiond(sessiond_sock_path);
 924         if (ret < 0) {
 925                 /* Not alive */
 926                 return 0;
 927         }
 928
 929         /* Is alive */
 930         return 1;
 931 }
 932
 933 /*
 934  * lib constructor
 935  */
 936 static void __attribute__((constructor)) init()
 937 {
 938         /* Set default session group */
 939         lttng_set_tracing_group(DEFAULT_TRACING_GROUP);
 940 }