src/bin/lttng-sessiond/kernel.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 <errno.h>
  21 #include <fcntl.h>
  22 #include <stdlib.h>
  23 #include <stdio.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <inttypes.h>
  27
  28 #include <common/common.h>
  29 #include <common/kernel-ctl/kernel-ctl.h>
  30 #include <common/kernel-ctl/kernel-ioctl.h>
  31 #include <common/sessiond-comm/sessiond-comm.h>
  32
  33 #include "consumer.h"
  34 #include "kernel.h"
  35 #include "kernel-consumer.h"
  36 #include "kern-modules.h"
  37 #include "utils.h"
  38
  39 /*
  40  * Add context on a kernel channel.
  41  */
  42 int kernel_add_channel_context(struct ltt_kernel_channel *chan,
  43                 struct ltt_kernel_context *ctx)
  44 {
  45         int ret;
  46
  47         assert(chan);
  48         assert(ctx);
  49
  50         DBG("Adding context to channel %s", chan->channel->name);
  51         ret = kernctl_add_context(chan->fd, &ctx->ctx);
  52         if (ret < 0) {
  53                 if (errno != EEXIST) {
  54                         PERROR("add context ioctl");
  55                 } else {
  56                         /* If EEXIST, we just ignore the error */
  57                         ret = 0;
  58                 }
  59                 goto error;
  60         }
  61
  62         cds_list_add_tail(&ctx->list, &chan->ctx_list);
  63
  64         return 0;
  65
  66 error:
  67         return ret;
  68 }
  69
  70 /*
  71  * Create a new kernel session, register it to the kernel tracer and add it to
  72  * the session daemon session.
  73  */
  74 int kernel_create_session(struct ltt_session *session, int tracer_fd)
  75 {
  76         int ret;
  77         struct ltt_kernel_session *lks;
  78
  79         assert(session);
  80
  81         /* Allocate data structure */
  82         lks = trace_kernel_create_session();
  83         if (lks == NULL) {
  84                 ret = -1;
  85                 goto error;
  86         }
  87
  88         /* Kernel tracer session creation */
  89         ret = kernctl_create_session(tracer_fd);
  90         if (ret < 0) {
  91                 PERROR("ioctl kernel create session");
  92                 goto error;
  93         }
  94
  95         lks->fd = ret;
  96         /* Prevent fd duplication after execlp() */
  97         ret = fcntl(lks->fd, F_SETFD, FD_CLOEXEC);
  98         if (ret < 0) {
  99                 PERROR("fcntl session fd");
 100         }
 101
 102         lks->id = session->id;
 103         lks->consumer_fds_sent = 0;
 104         session->kernel_session = lks;
 105
 106         DBG("Kernel session created (fd: %d)", lks->fd);
 107
 108         return 0;
 109
 110 error:
 111         if (lks) {
 112                 trace_kernel_destroy_session(lks);
 113         }
 114         return ret;
 115 }
 116
 117 /*
 118  * Create a kernel channel, register it to the kernel tracer and add it to the
 119  * kernel session.
 120  */
 121 int kernel_create_channel(struct ltt_kernel_session *session,
 122                 struct lttng_channel *chan)
 123 {
 124         int ret;
 125         struct ltt_kernel_channel *lkc;
 126
 127         assert(session);
 128         assert(chan);
 129
 130         /* Allocate kernel channel */
 131         lkc = trace_kernel_create_channel(chan);
 132         if (lkc == NULL) {
 133                 goto error;
 134         }
 135
 136         DBG3("Kernel create channel %s with attr: %d, %" PRIu64 ", %" PRIu64 ", %u, %u, %d, %d",
 137                         chan->name, lkc->channel->attr.overwrite,
 138                         lkc->channel->attr.subbuf_size, lkc->channel->attr.num_subbuf,
 139                         lkc->channel->attr.switch_timer_interval, lkc->channel->attr.read_timer_interval,
 140                         lkc->channel->attr.live_timer_interval, lkc->channel->attr.output);
 141
 142         /* Kernel tracer channel creation */
 143         ret = kernctl_create_channel(session->fd, &lkc->channel->attr);
 144         if (ret < 0) {
 145                 PERROR("ioctl kernel create channel");
 146                 goto error;
 147         }
 148
 149         /* Setup the channel fd */
 150         lkc->fd = ret;
 151         /* Prevent fd duplication after execlp() */
 152         ret = fcntl(lkc->fd, F_SETFD, FD_CLOEXEC);
 153         if (ret < 0) {
 154                 PERROR("fcntl session fd");
 155         }
 156
 157         /* Add channel to session */
 158         cds_list_add(&lkc->list, &session->channel_list.head);
 159         session->channel_count++;
 160         lkc->session = session;
 161
 162         DBG("Kernel channel %s created (fd: %d)", lkc->channel->name, lkc->fd);
 163
 164         return 0;
 165
 166 error:
 167         if (lkc) {
 168                 free(lkc->channel);
 169                 free(lkc);
 170         }
 171         return -1;
 172 }
 173
 174 /*
 175  * Create a kernel event, enable it to the kernel tracer and add it to the
 176  * channel event list of the kernel session.
 177  * We own filter_expression and filter.
 178  */
 179 int kernel_create_event(struct lttng_event *ev,
 180                 struct ltt_kernel_channel *channel)
 181 {
 182         int ret;
 183         struct ltt_kernel_event *event;
 184
 185         assert(ev);
 186         assert(channel);
 187
 188         event = trace_kernel_create_event(ev);
 189         if (event == NULL) {
 190                 ret = -1;
 191                 goto error;
 192         }
 193
 194         ret = kernctl_create_event(channel->fd, event->event);
 195         if (ret < 0) {
 196                 switch (errno) {
 197                 case EEXIST:
 198                         break;
 199                 case ENOSYS:
 200                         WARN("Event type not implemented");
 201                         break;
 202                 case ENOENT:
 203                         WARN("Event %s not found!", ev->name);
 204                         break;
 205                 default:
 206                         PERROR("create event ioctl");
 207                 }
 208                 ret = -errno;
 209                 goto free_event;
 210         }
 211
 212         /*
 213          * LTTNG_KERNEL_SYSCALL event creation will return 0 on success.
 214          */
 215         if (ret == 0 && event->event->instrumentation == LTTNG_KERNEL_SYSCALL) {
 216                 DBG2("Kernel event syscall creation success");
 217                 /*
 218                  * We use fd == -1 to ensure that we never trigger a close of fd
 219                  * 0.
 220                  */
 221                 event->fd = -1;
 222                 goto add_list;
 223         }
 224
 225         event->fd = ret;
 226         /* Prevent fd duplication after execlp() */
 227         ret = fcntl(event->fd, F_SETFD, FD_CLOEXEC);
 228         if (ret < 0) {
 229                 PERROR("fcntl session fd");
 230         }
 231
 232 add_list:
 233         /* Add event to event list */
 234         cds_list_add(&event->list, &channel->events_list.head);
 235         channel->event_count++;
 236
 237         DBG("Event %s created (fd: %d)", ev->name, event->fd);
 238
 239         return 0;
 240
 241 free_event:
 242         free(event);
 243 error:
 244         return ret;
 245 }
 246
 247 /*
 248  * Disable a kernel channel.
 249  */
 250 int kernel_disable_channel(struct ltt_kernel_channel *chan)
 251 {
 252         int ret;
 253
 254         assert(chan);
 255
 256         ret = kernctl_disable(chan->fd);
 257         if (ret < 0) {
 258                 PERROR("disable chan ioctl");
 259                 ret = errno;
 260                 goto error;
 261         }
 262
 263         chan->enabled = 0;
 264         DBG("Kernel channel %s disabled (fd: %d)", chan->channel->name, chan->fd);
 265
 266         return 0;
 267
 268 error:
 269         return ret;
 270 }
 271
 272 /*
 273  * Enable a kernel channel.
 274  */
 275 int kernel_enable_channel(struct ltt_kernel_channel *chan)
 276 {
 277         int ret;
 278
 279         assert(chan);
 280
 281         ret = kernctl_enable(chan->fd);
 282         if (ret < 0 && errno != EEXIST) {
 283                 PERROR("Enable kernel chan");
 284                 goto error;
 285         }
 286
 287         chan->enabled = 1;
 288         DBG("Kernel channel %s enabled (fd: %d)", chan->channel->name, chan->fd);
 289
 290         return 0;
 291
 292 error:
 293         return ret;
 294 }
 295
 296 /*
 297  * Enable a kernel event.
 298  */
 299 int kernel_enable_event(struct ltt_kernel_event *event)
 300 {
 301         int ret;
 302
 303         assert(event);
 304
 305         ret = kernctl_enable(event->fd);
 306         if (ret < 0) {
 307                 switch (errno) {
 308                 case EEXIST:
 309                         ret = LTTNG_ERR_KERN_EVENT_EXIST;
 310                         break;
 311                 default:
 312                         PERROR("enable kernel event");
 313                         break;
 314                 }
 315                 goto error;
 316         }
 317
 318         event->enabled = 1;
 319         DBG("Kernel event %s enabled (fd: %d)", event->event->name, event->fd);
 320
 321         return 0;
 322
 323 error:
 324         return ret;
 325 }
 326
 327 /*
 328  * Disable a kernel event.
 329  */
 330 int kernel_disable_event(struct ltt_kernel_event *event)
 331 {
 332         int ret;
 333
 334         assert(event);
 335
 336         ret = kernctl_disable(event->fd);
 337         if (ret < 0) {
 338                 switch (errno) {
 339                 case EEXIST:
 340                         ret = LTTNG_ERR_KERN_EVENT_EXIST;
 341                         break;
 342                 default:
 343                         PERROR("disable kernel event");
 344                         break;
 345                 }
 346                 goto error;
 347         }
 348
 349         event->enabled = 0;
 350         DBG("Kernel event %s disabled (fd: %d)", event->event->name, event->fd);
 351
 352         return 0;
 353
 354 error:
 355         return ret;
 356 }
 357
 358 int kernel_enable_syscall(const char *syscall_name,
 359                 struct ltt_kernel_channel *channel)
 360 {
 361         return kernctl_enable_syscall(channel->fd, syscall_name);
 362 }
 363
 364 int kernel_disable_syscall(const char *syscall_name,
 365                 struct ltt_kernel_channel *channel)
 366 {
 367         return kernctl_disable_syscall(channel->fd, syscall_name);
 368 }
 369
 370 /*
 371  * Create kernel metadata, open from the kernel tracer and add it to the
 372  * kernel session.
 373  */
 374 int kernel_open_metadata(struct ltt_kernel_session *session)
 375 {
 376         int ret;
 377         struct ltt_kernel_metadata *lkm = NULL;
 378
 379         assert(session);
 380
 381         /* Allocate kernel metadata */
 382         lkm = trace_kernel_create_metadata();
 383         if (lkm == NULL) {
 384                 goto error;
 385         }
 386
 387         /* Kernel tracer metadata creation */
 388         ret = kernctl_open_metadata(session->fd, &lkm->conf->attr);
 389         if (ret < 0) {
 390                 goto error_open;
 391         }
 392
 393         lkm->fd = ret;
 394         /* Prevent fd duplication after execlp() */
 395         ret = fcntl(lkm->fd, F_SETFD, FD_CLOEXEC);
 396         if (ret < 0) {
 397                 PERROR("fcntl session fd");
 398         }
 399
 400         session->metadata = lkm;
 401
 402         DBG("Kernel metadata opened (fd: %d)", lkm->fd);
 403
 404         return 0;
 405
 406 error_open:
 407         trace_kernel_destroy_metadata(lkm);
 408 error:
 409         return -1;
 410 }
 411
 412 /*
 413  * Start tracing session.
 414  */
 415 int kernel_start_session(struct ltt_kernel_session *session)
 416 {
 417         int ret;
 418
 419         assert(session);
 420
 421         ret = kernctl_start_session(session->fd);
 422         if (ret < 0) {
 423                 PERROR("ioctl start session");
 424                 goto error;
 425         }
 426
 427         DBG("Kernel session started");
 428
 429         return 0;
 430
 431 error:
 432         return ret;
 433 }
 434
 435 /*
 436  * Make a kernel wait to make sure in-flight probe have completed.
 437  */
 438 void kernel_wait_quiescent(int fd)
 439 {
 440         int ret;
 441
 442         DBG("Kernel quiescent wait on %d", fd);
 443
 444         ret = kernctl_wait_quiescent(fd);
 445         if (ret < 0) {
 446                 PERROR("wait quiescent ioctl");
 447                 ERR("Kernel quiescent wait failed");
 448         }
 449 }
 450
 451 /*
 452  * Kernel calibrate
 453  */
 454 int kernel_calibrate(int fd, struct lttng_kernel_calibrate *calibrate)
 455 {
 456         int ret;
 457
 458         assert(calibrate);
 459
 460         ret = kernctl_calibrate(fd, calibrate);
 461         if (ret < 0) {
 462                 PERROR("calibrate ioctl");
 463                 return -1;
 464         }
 465
 466         return 0;
 467 }
 468
 469
 470 /*
 471  *  Force flush buffer of metadata.
 472  */
 473 int kernel_metadata_flush_buffer(int fd)
 474 {
 475         int ret;
 476
 477         DBG("Kernel flushing metadata buffer on fd %d", fd);
 478
 479         ret = kernctl_buffer_flush(fd);
 480         if (ret < 0) {
 481                 ERR("Fail to flush metadata buffers %d (ret: %d)", fd, ret);
 482         }
 483
 484         return 0;
 485 }
 486
 487 /*
 488  * Force flush buffer for channel.
 489  */
 490 int kernel_flush_buffer(struct ltt_kernel_channel *channel)
 491 {
 492         int ret;
 493         struct ltt_kernel_stream *stream;
 494
 495         assert(channel);
 496
 497         DBG("Flush buffer for channel %s", channel->channel->name);
 498
 499         cds_list_for_each_entry(stream, &channel->stream_list.head, list) {
 500                 DBG("Flushing channel stream %d", stream->fd);
 501                 ret = kernctl_buffer_flush(stream->fd);
 502                 if (ret < 0) {
 503                         PERROR("ioctl");
 504                         ERR("Fail to flush buffer for stream %d (ret: %d)",
 505                                         stream->fd, ret);
 506                 }
 507         }
 508
 509         return 0;
 510 }
 511
 512 /*
 513  * Stop tracing session.
 514  */
 515 int kernel_stop_session(struct ltt_kernel_session *session)
 516 {
 517         int ret;
 518
 519         assert(session);
 520
 521         ret = kernctl_stop_session(session->fd);
 522         if (ret < 0) {
 523                 goto error;
 524         }
 525
 526         DBG("Kernel session stopped");
 527
 528         return 0;
 529
 530 error:
 531         return ret;
 532 }
 533
 534 /*
 535  * Open stream of channel, register it to the kernel tracer and add it
 536  * to the stream list of the channel.
 537  *
 538  * Return the number of created stream. Else, a negative value.
 539  */
 540 int kernel_open_channel_stream(struct ltt_kernel_channel *channel)
 541 {
 542         int ret, count = 0;
 543         struct ltt_kernel_stream *lks;
 544
 545         assert(channel);
 546
 547         while ((ret = kernctl_create_stream(channel->fd)) >= 0) {
 548                 lks = trace_kernel_create_stream(channel->channel->name, count);
 549                 if (lks == NULL) {
 550                         ret = close(ret);
 551                         if (ret) {
 552                                 PERROR("close");
 553                         }
 554                         goto error;
 555                 }
 556
 557                 lks->fd = ret;
 558                 /* Prevent fd duplication after execlp() */
 559                 ret = fcntl(lks->fd, F_SETFD, FD_CLOEXEC);
 560                 if (ret < 0) {
 561                         PERROR("fcntl session fd");
 562                 }
 563
 564                 lks->tracefile_size = channel->channel->attr.tracefile_size;
 565                 lks->tracefile_count = channel->channel->attr.tracefile_count;
 566
 567                 /* Add stream to channe stream list */
 568                 cds_list_add(&lks->list, &channel->stream_list.head);
 569                 channel->stream_count++;
 570
 571                 /* Increment counter which represent CPU number. */
 572                 count++;
 573
 574                 DBG("Kernel stream %s created (fd: %d, state: %d)", lks->name, lks->fd,
 575                                 lks->state);
 576         }
 577
 578         return channel->stream_count;
 579
 580 error:
 581         return -1;
 582 }
 583
 584 /*
 585  * Open the metadata stream and set it to the kernel session.
 586  */
 587 int kernel_open_metadata_stream(struct ltt_kernel_session *session)
 588 {
 589         int ret;
 590
 591         assert(session);
 592
 593         ret = kernctl_create_stream(session->metadata->fd);
 594         if (ret < 0) {
 595                 PERROR("kernel create metadata stream");
 596                 goto error;
 597         }
 598
 599         DBG("Kernel metadata stream created (fd: %d)", ret);
 600         session->metadata_stream_fd = ret;
 601         /* Prevent fd duplication after execlp() */
 602         ret = fcntl(session->metadata_stream_fd, F_SETFD, FD_CLOEXEC);
 603         if (ret < 0) {
 604                 PERROR("fcntl session fd");
 605         }
 606
 607         return 0;
 608
 609 error:
 610         return -1;
 611 }
 612
 613 /*
 614  * Get the event list from the kernel tracer and return the number of elements.
 615  */
 616 ssize_t kernel_list_events(int tracer_fd, struct lttng_event **events)
 617 {
 618         int fd, ret;
 619         char *event;
 620         size_t nbmem, count = 0;
 621         FILE *fp;
 622         struct lttng_event *elist;
 623
 624         assert(events);
 625
 626         fd = kernctl_tracepoint_list(tracer_fd);
 627         if (fd < 0) {
 628                 PERROR("kernel tracepoint list");
 629                 goto error;
 630         }
 631
 632         fp = fdopen(fd, "r");
 633         if (fp == NULL) {
 634                 PERROR("kernel tracepoint list fdopen");
 635                 goto error_fp;
 636         }
 637
 638         /*
 639          * Init memory size counter
 640          * See kernel-ctl.h for explanation of this value
 641          */
 642         nbmem = KERNEL_EVENT_INIT_LIST_SIZE;
 643         elist = zmalloc(sizeof(struct lttng_event) * nbmem);
 644         if (elist == NULL) {
 645                 PERROR("alloc list events");
 646                 count = -ENOMEM;
 647                 goto end;
 648         }
 649
 650         while (fscanf(fp, "event { name = %m[^;]; };\n", &event) == 1) {
 651                 if (count >= nbmem) {
 652                         struct lttng_event *new_elist;
 653                         size_t new_nbmem;
 654
 655                         new_nbmem = nbmem << 1;
 656                         DBG("Reallocating event list from %zu to %zu bytes",
 657                                         nbmem, new_nbmem);
 658                         new_elist = realloc(elist, new_nbmem * sizeof(struct lttng_event));
 659                         if (new_elist == NULL) {
 660                                 PERROR("realloc list events");
 661                                 free(event);
 662                                 free(elist);
 663                                 count = -ENOMEM;
 664                                 goto end;
 665                         }
 666                         /* Zero the new memory */
 667                         memset(new_elist + nbmem, 0,
 668                                 (new_nbmem - nbmem) * sizeof(struct lttng_event));
 669                         nbmem = new_nbmem;
 670                         elist = new_elist;
 671                 }
 672                 strncpy(elist[count].name, event, LTTNG_SYMBOL_NAME_LEN);
 673                 elist[count].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
 674                 elist[count].enabled = -1;
 675                 count++;
 676                 free(event);
 677         }
 678
 679         *events = elist;
 680         DBG("Kernel list events done (%zu events)", count);
 681 end:
 682         ret = fclose(fp);       /* closes both fp and fd */
 683         if (ret) {
 684                 PERROR("fclose");
 685         }
 686         return count;
 687
 688 error_fp:
 689         ret = close(fd);
 690         if (ret) {
 691                 PERROR("close");
 692         }
 693 error:
 694         return -1;
 695 }
 696
 697 /*
 698  * Get kernel version and validate it.
 699  */
 700 int kernel_validate_version(int tracer_fd)
 701 {
 702         int ret;
 703         struct lttng_kernel_tracer_version version;
 704         struct lttng_kernel_tracer_abi_version abi_version;
 705
 706         ret = kernctl_tracer_version(tracer_fd, &version);
 707         if (ret < 0) {
 708                 ERR("Failed at getting the lttng-modules version");
 709                 goto error;
 710         }
 711
 712         /* Validate version */
 713         if (version.major != VERSION_MAJOR) {
 714                 ERR("Kernel tracer major version (%d) is not compatible with lttng-tools major version (%d)",
 715                         version.major, VERSION_MAJOR);
 716                 goto error_version;
 717         }
 718         ret = kernctl_tracer_abi_version(tracer_fd, &abi_version);
 719         if (ret < 0) {
 720                 ERR("Failed at getting lttng-modules ABI version");
 721                 goto error;
 722         }
 723         if (abi_version.major != LTTNG_MODULES_ABI_MAJOR_VERSION) {
 724                 ERR("Kernel tracer ABI version (%d.%d) is not compatible with expected ABI major version (%d.*)",
 725                         abi_version.major, abi_version.minor,
 726                         LTTNG_MODULES_ABI_MAJOR_VERSION);
 727                 goto error;
 728         }
 729         DBG2("Kernel tracer version validated (%d.%d, ABI %d.%d)",
 730                         version.major, version.minor,
 731                         abi_version.major, abi_version.minor);
 732         return 0;
 733
 734 error_version:
 735         ret = -1;
 736
 737 error:
 738         return ret;
 739 }
 740
 741 /*
 742  * Kernel work-arounds called at the start of sessiond main().
 743  */
 744 int init_kernel_workarounds(void)
 745 {
 746         int ret;
 747         FILE *fp;
 748
 749         /*
 750          * boot_id needs to be read once before being used concurrently
 751          * to deal with a Linux kernel race. A fix is proposed for
 752          * upstream, but the work-around is needed for older kernels.
 753          */
 754         fp = fopen("/proc/sys/kernel/random/boot_id", "r");
 755         if (!fp) {
 756                 goto end_boot_id;
 757         }
 758         while (!feof(fp)) {
 759                 char buf[37] = "";
 760
 761                 ret = fread(buf, 1, sizeof(buf), fp);
 762                 if (ret < 0) {
 763                         /* Ignore error, we don't really care */
 764                 }
 765         }
 766         ret = fclose(fp);
 767         if (ret) {
 768                 PERROR("fclose");
 769         }
 770 end_boot_id:
 771         return 0;
 772 }
 773
 774 /*
 775  * Complete teardown of a kernel session.
 776  */
 777 void kernel_destroy_session(struct ltt_kernel_session *ksess)
 778 {
 779         if (ksess == NULL) {
 780                 DBG3("No kernel session when tearing down session");
 781                 return;
 782         }
 783
 784         DBG("Tearing down kernel session");
 785
 786         /*
 787          * Destroy channels on the consumer if at least one FD has been sent and we
 788          * are in no output mode because the streams are in *no* monitor mode so we
 789          * have to send a command to clean them up or else they leaked.
 790          */
 791         if (!ksess->output_traces && ksess->consumer_fds_sent) {
 792                 int ret;
 793                 struct consumer_socket *socket;
 794                 struct lttng_ht_iter iter;
 795
 796                 /* For each consumer socket. */
 797                 rcu_read_lock();
 798                 cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
 799                                 socket, node.node) {
 800                         struct ltt_kernel_channel *chan;
 801
 802                         /* For each channel, ask the consumer to destroy it. */
 803                         cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
 804                                 ret = kernel_consumer_destroy_channel(socket, chan);
 805                                 if (ret < 0) {
 806                                         /* Consumer is probably dead. Use next socket. */
 807                                         continue;
 808                                 }
 809                         }
 810                 }
 811                 rcu_read_unlock();
 812         }
 813
 814         /* Close any relayd session */
 815         consumer_output_send_destroy_relayd(ksess->consumer);
 816
 817         trace_kernel_destroy_session(ksess);
 818 }
 819
 820 /*
 821  * Destroy a kernel channel object. It does not do anything on the tracer side.
 822  */
 823 void kernel_destroy_channel(struct ltt_kernel_channel *kchan)
 824 {
 825         struct ltt_kernel_session *ksess = NULL;
 826
 827         assert(kchan);
 828         assert(kchan->channel);
 829
 830         DBG3("Kernel destroy channel %s", kchan->channel->name);
 831
 832         /* Update channel count of associated session. */
 833         if (kchan->session) {
 834                 /* Keep pointer reference so we can update it after the destroy. */
 835                 ksess = kchan->session;
 836         }
 837
 838         trace_kernel_destroy_channel(kchan);
 839
 840         /*
 841          * At this point the kernel channel is not visible anymore. This is safe
 842          * since in order to work on a visible kernel session, the tracing session
 843          * lock (ltt_session.lock) MUST be acquired.
 844          */
 845         if (ksess) {
 846                 ksess->channel_count--;
 847         }
 848 }
 849
 850 /*
 851  * Take a snapshot for a given kernel session.
 852  *
 853  * Return 0 on success or else return a LTTNG_ERR code.
 854  */
 855 int kernel_snapshot_record(struct ltt_kernel_session *ksess,
 856                 struct snapshot_output *output, int wait, uint64_t max_size_per_stream)
 857 {
 858         int err, ret, saved_metadata_fd;
 859         struct consumer_socket *socket;
 860         struct lttng_ht_iter iter;
 861         struct ltt_kernel_metadata *saved_metadata;
 862
 863         assert(ksess);
 864         assert(ksess->consumer);
 865         assert(output);
 866
 867         DBG("Kernel snapshot record started");
 868
 869         /* Save current metadata since the following calls will change it. */
 870         saved_metadata = ksess->metadata;
 871         saved_metadata_fd = ksess->metadata_stream_fd;
 872
 873         rcu_read_lock();
 874
 875         ret = kernel_open_metadata(ksess);
 876         if (ret < 0) {
 877                 ret = LTTNG_ERR_KERN_META_FAIL;
 878                 goto error;
 879         }
 880
 881         ret = kernel_open_metadata_stream(ksess);
 882         if (ret < 0) {
 883                 ret = LTTNG_ERR_KERN_META_FAIL;
 884                 goto error_open_stream;
 885         }
 886
 887         /* Send metadata to consumer and snapshot everything. */
 888         cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
 889                         socket, node.node) {
 890                 struct consumer_output *saved_output;
 891                 struct ltt_kernel_channel *chan;
 892
 893                 /*
 894                  * Temporarly switch consumer output for our snapshot output. As long
 895                  * as the session lock is taken, this is safe.
 896                  */
 897                 saved_output = ksess->consumer;
 898                 ksess->consumer = output->consumer;
 899
 900                 pthread_mutex_lock(socket->lock);
 901                 /* This stream must not be monitored by the consumer. */
 902                 ret = kernel_consumer_add_metadata(socket, ksess, 0);
 903                 pthread_mutex_unlock(socket->lock);
 904                 /* Put back the saved consumer output into the session. */
 905                 ksess->consumer = saved_output;
 906                 if (ret < 0) {
 907                         ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
 908                         goto error_consumer;
 909                 }
 910
 911                 /* For each channel, ask the consumer to snapshot it. */
 912                 cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
 913                         pthread_mutex_lock(socket->lock);
 914                         ret = consumer_snapshot_channel(socket, chan->fd, output, 0,
 915                                         ksess->uid, ksess->gid,
 916                                         DEFAULT_KERNEL_TRACE_DIR, wait,
 917                                         max_size_per_stream);
 918                         pthread_mutex_unlock(socket->lock);
 919                         if (ret < 0) {
 920                                 ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
 921                                 (void) kernel_consumer_destroy_metadata(socket,
 922                                                 ksess->metadata);
 923                                 goto error_consumer;
 924                         }
 925                 }
 926
 927                 /* Snapshot metadata, */
 928                 pthread_mutex_lock(socket->lock);
 929                 ret = consumer_snapshot_channel(socket, ksess->metadata->fd, output,
 930                                 1, ksess->uid, ksess->gid,
 931                                 DEFAULT_KERNEL_TRACE_DIR, wait, max_size_per_stream);
 932                 pthread_mutex_unlock(socket->lock);
 933                 if (ret < 0) {
 934                         ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
 935                         goto error_consumer;
 936                 }
 937
 938                 /*
 939                  * The metadata snapshot is done, ask the consumer to destroy it since
 940                  * it's not monitored on the consumer side.
 941                  */
 942                 (void) kernel_consumer_destroy_metadata(socket, ksess->metadata);
 943         }
 944
 945         ret = LTTNG_OK;
 946
 947 error_consumer:
 948         /* Close newly opened metadata stream. It's now on the consumer side. */
 949         err = close(ksess->metadata_stream_fd);
 950         if (err < 0) {
 951                 PERROR("close snapshot kernel");
 952         }
 953
 954 error_open_stream:
 955         trace_kernel_destroy_metadata(ksess->metadata);
 956 error:
 957         /* Restore metadata state.*/
 958         ksess->metadata = saved_metadata;
 959         ksess->metadata_stream_fd = saved_metadata_fd;
 960
 961         rcu_read_unlock();
 962         return ret;
 963 }
 964
 965 /*
 966  * Get the syscall mask array from the kernel tracer.
 967  *
 968  * Return 0 on success else a negative value. In both case, syscall_mask should
 969  * be freed.
 970  */
 971 int kernel_syscall_mask(int chan_fd, char **syscall_mask, uint32_t *nr_bits)
 972 {
 973         assert(syscall_mask);
 974         assert(nr_bits);
 975
 976         return kernctl_syscall_mask(chan_fd, syscall_mask, nr_bits);
 977 }