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