libust/ltt-events.c

   1 /*
   2  * ltt-events.c
   3  *
   4  * Copyright 2010 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Holds LTTng per-session event registry.
   7  *
   8  * Dual LGPL v2.1/GPL v2 license.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/list.h>
  13 #include <linux/mutex.h>
  14 #include <linux/sched.h>
  15 #include <linux/slab.h>
  16 #include <linux/jiffies.h>
  17 #include <linux/uuid.h>
  18 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  19 #include "ltt-events.h"
  20 #include "ltt-tracer.h"
  21
  22 static LIST_HEAD(sessions);
  23 static LIST_HEAD(ltt_transport_list);
  24 static DEFINE_MUTEX(sessions_mutex);
  25 static struct kmem_cache *event_cache;
  26
  27 static void _ltt_event_destroy(struct ltt_event *event);
  28 static void _ltt_channel_destroy(struct ltt_channel *chan);
  29 static int _ltt_event_unregister(struct ltt_event *event);
  30 static
  31 int _ltt_event_metadata_statedump(struct ltt_session *session,
  32                                   struct ltt_channel *chan,
  33                                   struct ltt_event *event);
  34 static
  35 int _ltt_session_metadata_statedump(struct ltt_session *session);
  36
  37
  38 static
  39 void synchronize_trace(void)
  40 {
  41         synchronize_sched();
  42 #ifdef CONFIG_PREEMPT_RT
  43         synchronize_rcu();
  44 #endif
  45 }
  46
  47 struct ltt_session *ltt_session_create(void)
  48 {
  49         struct ltt_session *session;
  50
  51         mutex_lock(&sessions_mutex);
  52         session = kzalloc(sizeof(struct ltt_session), GFP_KERNEL);
  53         if (!session)
  54                 return NULL;
  55         INIT_LIST_HEAD(&session->chan);
  56         INIT_LIST_HEAD(&session->events);
  57         uuid_le_gen(&session->uuid);
  58         list_add(&session->list, &sessions);
  59         mutex_unlock(&sessions_mutex);
  60         return session;
  61 }
  62
  63 void ltt_session_destroy(struct ltt_session *session)
  64 {
  65         struct ltt_channel *chan, *tmpchan;
  66         struct ltt_event *event, *tmpevent;
  67         int ret;
  68
  69         mutex_lock(&sessions_mutex);
  70         ACCESS_ONCE(session->active) = 0;
  71         list_for_each_entry(event, &session->events, list) {
  72                 ret = _ltt_event_unregister(event);
  73                 WARN_ON(ret);
  74         }
  75         synchronize_trace();    /* Wait for in-flight events to complete */
  76         list_for_each_entry_safe(event, tmpevent, &session->events, list)
  77                 _ltt_event_destroy(event);
  78         list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
  79                 _ltt_channel_destroy(chan);
  80         list_del(&session->list);
  81         mutex_unlock(&sessions_mutex);
  82         kfree(session);
  83 }
  84
  85 int ltt_session_enable(struct ltt_session *session)
  86 {
  87         int ret = 0;
  88         struct ltt_channel *chan;
  89
  90         mutex_lock(&sessions_mutex);
  91         if (session->active) {
  92                 ret = -EBUSY;
  93                 goto end;
  94         }
  95
  96         /*
  97          * Snapshot the number of events per channel to know the type of header
  98          * we need to use.
  99          */
 100         list_for_each_entry(chan, &session->chan, list) {
 101                 if (chan->header_type)
 102                         continue;               /* don't change it if session stop/restart */
 103                 if (chan->free_event_id < 31)
 104                         chan->header_type = 1;  /* compact */
 105                 else
 106                         chan->header_type = 2;  /* large */
 107         }
 108
 109         ACCESS_ONCE(session->active) = 1;
 110         ACCESS_ONCE(session->been_active) = 1;
 111         synchronize_trace();    /* Wait for in-flight events to complete */
 112         ret = _ltt_session_metadata_statedump(session);
 113         if (ret) {
 114                 ACCESS_ONCE(session->active) = 0;
 115                 synchronize_trace();    /* Wait for in-flight events to complete */
 116         }
 117 end:
 118         mutex_unlock(&sessions_mutex);
 119         return ret;
 120 }
 121
 122 int ltt_session_disable(struct ltt_session *session)
 123 {
 124         int ret = 0;
 125
 126         mutex_lock(&sessions_mutex);
 127         if (!session->active) {
 128                 ret = -EBUSY;
 129                 goto end;
 130         }
 131         ACCESS_ONCE(session->active) = 0;
 132         synchronize_trace();    /* Wait for in-flight events to complete */
 133 end:
 134         mutex_unlock(&sessions_mutex);
 135         return ret;
 136 }
 137
 138 int ltt_channel_enable(struct ltt_channel *channel)
 139 {
 140         int old;
 141
 142         old = xchg(&channel->enabled, 1);
 143         if (old)
 144                 return -EEXIST;
 145         return 0;
 146 }
 147
 148 int ltt_channel_disable(struct ltt_channel *channel)
 149 {
 150         int old;
 151
 152         old = xchg(&channel->enabled, 0);
 153         if (!old)
 154                 return -EEXIST;
 155         return 0;
 156 }
 157
 158 int ltt_event_enable(struct ltt_event *event)
 159 {
 160         int old;
 161
 162         old = xchg(&event->enabled, 1);
 163         if (old)
 164                 return -EEXIST;
 165         return 0;
 166 }
 167
 168 int ltt_event_disable(struct ltt_event *event)
 169 {
 170         int old;
 171
 172         old = xchg(&event->enabled, 0);
 173         if (!old)
 174                 return -EEXIST;
 175         return 0;
 176 }
 177
 178 static struct ltt_transport *ltt_transport_find(const char *name)
 179 {
 180         struct ltt_transport *transport;
 181
 182         list_for_each_entry(transport, &ltt_transport_list, node) {
 183                 if (!strcmp(transport->name, name))
 184                         return transport;
 185         }
 186         return NULL;
 187 }
 188
 189 struct ltt_channel *ltt_channel_create(struct ltt_session *session,
 190                                        const char *transport_name,
 191                                        void *buf_addr,
 192                                        size_t subbuf_size, size_t num_subbuf,
 193                                        unsigned int switch_timer_interval,
 194                                        unsigned int read_timer_interval)
 195 {
 196         struct ltt_channel *chan;
 197         struct ltt_transport *transport;
 198
 199         mutex_lock(&sessions_mutex);
 200         if (session->been_active)
 201                 goto active;    /* Refuse to add channel to active session */
 202         transport = ltt_transport_find(transport_name);
 203         if (!transport) {
 204                 printk(KERN_WARNING "LTTng transport %s not found\n",
 205                        transport_name);
 206                 goto notransport;
 207         }
 208         chan = kzalloc(sizeof(struct ltt_channel), GFP_KERNEL);
 209         if (!chan)
 210                 goto nomem;
 211         chan->session = session;
 212         chan->id = session->free_chan_id++;
 213         /*
 214          * Note: the channel creation op already writes into the packet
 215          * headers. Therefore the "chan" information used as input
 216          * should be already accessible.
 217          */
 218         chan->chan = transport->ops.channel_create("[lttng]", chan, buf_addr,
 219                         subbuf_size, num_subbuf, switch_timer_interval,
 220                         read_timer_interval);
 221         if (!chan->chan)
 222                 goto create_error;
 223         chan->enabled = 1;
 224         chan->ops = &transport->ops;
 225         list_add(&chan->list, &session->chan);
 226         mutex_unlock(&sessions_mutex);
 227         return chan;
 228
 229 create_error:
 230         kfree(chan);
 231 nomem:
 232 notransport:
 233 active:
 234         mutex_unlock(&sessions_mutex);
 235         return NULL;
 236 }
 237
 238 /*
 239  * Only used internally at session destruction.
 240  */
 241 static
 242 void _ltt_channel_destroy(struct ltt_channel *chan)
 243 {
 244         chan->ops->channel_destroy(chan->chan);
 245         list_del(&chan->list);
 246         lttng_destroy_context(chan->ctx);
 247         kfree(chan);
 248 }
 249
 250 /*
 251  * Supports event creation while tracing session is active.
 252  */
 253 struct ltt_event *ltt_event_create(struct ltt_channel *chan,
 254                                    struct lttng_kernel_event *event_param,
 255                                    void *filter)
 256 {
 257         struct ltt_event *event;
 258         int ret;
 259
 260         mutex_lock(&sessions_mutex);
 261         if (chan->free_event_id == -1UL)
 262                 goto full;
 263         /*
 264          * This is O(n^2) (for each event, the loop is called at event
 265          * creation). Might require a hash if we have lots of events.
 266          */
 267         list_for_each_entry(event, &chan->session->events, list)
 268                 if (!strcmp(event->desc->name, event_param->name))
 269                         goto exist;
 270         event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
 271         if (!event)
 272                 goto cache_error;
 273         event->chan = chan;
 274         event->filter = filter;
 275         event->id = chan->free_event_id++;
 276         event->enabled = 1;
 277         event->instrumentation = event_param->instrumentation;
 278         /* Populate ltt_event structure before tracepoint registration. */
 279         smp_wmb();
 280         switch (event_param->instrumentation) {
 281         case LTTNG_KERNEL_TRACEPOINT:
 282                 event->desc = ltt_event_get(event_param->name);
 283                 if (!event->desc)
 284                         goto register_error;
 285                 ret = tracepoint_probe_register(event_param->name,
 286                                 event->desc->probe_callback,
 287                                 event);
 288                 if (ret)
 289                         goto register_error;
 290                 break;
 291         case LTTNG_KERNEL_KPROBE:
 292                 ret = lttng_kprobes_register(event_param->name,
 293                                 event_param->u.kprobe.symbol_name,
 294                                 event_param->u.kprobe.offset,
 295                                 event_param->u.kprobe.addr,
 296                                 event);
 297                 if (ret)
 298                         goto register_error;
 299                 ret = try_module_get(event->desc->owner);
 300                 WARN_ON_ONCE(!ret);
 301                 break;
 302         case LTTNG_KERNEL_FUNCTION:
 303                 ret = lttng_ftrace_register(event_param->name,
 304                                 event_param->u.ftrace.symbol_name,
 305                                 event);
 306                 if (ret)
 307                         goto register_error;
 308                 ret = try_module_get(event->desc->owner);
 309                 WARN_ON_ONCE(!ret);
 310                 break;
 311         default:
 312                 WARN_ON_ONCE(1);
 313         }
 314         ret = _ltt_event_metadata_statedump(chan->session, chan, event);
 315         if (ret)
 316                 goto statedump_error;
 317         list_add(&event->list, &chan->session->events);
 318         mutex_unlock(&sessions_mutex);
 319         return event;
 320
 321 statedump_error:
 322         WARN_ON_ONCE(tracepoint_probe_unregister(event_param->name,
 323                                 event->desc->probe_callback,
 324                                 event));
 325         ltt_event_put(event->desc);
 326 register_error:
 327         kmem_cache_free(event_cache, event);
 328 cache_error:
 329 exist:
 330 full:
 331         mutex_unlock(&sessions_mutex);
 332         return NULL;
 333 }
 334
 335 /*
 336  * Only used internally at session destruction.
 337  */
 338 int _ltt_event_unregister(struct ltt_event *event)
 339 {
 340         int ret = -EINVAL;
 341
 342         switch (event->instrumentation) {
 343         case LTTNG_KERNEL_TRACEPOINT:
 344                 ret = tracepoint_probe_unregister(event->desc->name,
 345                                                   event->desc->probe_callback,
 346                                                   event);
 347                 if (ret)
 348                         return ret;
 349                 break;
 350         case LTTNG_KERNEL_KPROBE:
 351                 lttng_kprobes_unregister(event);
 352                 ret = 0;
 353                 break;
 354         case LTTNG_KERNEL_FUNCTION:
 355                 lttng_ftrace_unregister(event);
 356                 ret = 0;
 357                 break;
 358         default:
 359                 WARN_ON_ONCE(1);
 360         }
 361         return ret;
 362 }
 363
 364 /*
 365  * Only used internally at session destruction.
 366  */
 367 static
 368 void _ltt_event_destroy(struct ltt_event *event)
 369 {
 370         switch (event->instrumentation) {
 371         case LTTNG_KERNEL_TRACEPOINT:
 372                 ltt_event_put(event->desc);
 373                 break;
 374         case LTTNG_KERNEL_KPROBE:
 375                 module_put(event->desc->owner);
 376                 lttng_kprobes_destroy_private(event);
 377                 break;
 378         case LTTNG_KERNEL_FUNCTION:
 379                 module_put(event->desc->owner);
 380                 lttng_ftrace_destroy_private(event);
 381                 break;
 382         default:
 383                 WARN_ON_ONCE(1);
 384         }
 385         list_del(&event->list);
 386         lttng_destroy_context(event->ctx);
 387         kmem_cache_free(event_cache, event);
 388 }
 389
 390 /*
 391  * We have exclusive access to our metadata buffer (protected by the
 392  * sessions_mutex), so we can do racy operations such as looking for
 393  * remaining space left in packet and write, since mutual exclusion
 394  * protects us from concurrent writes.
 395  */
 396 int lttng_metadata_printf(struct ltt_session *session,
 397                           const char *fmt, ...)
 398 {
 399         struct lib_ring_buffer_ctx ctx;
 400         struct ltt_channel *chan = session->metadata;
 401         char *str;
 402         int ret = 0, waitret;
 403         size_t len, reserve_len, pos;
 404         va_list ap;
 405
 406         WARN_ON_ONCE(!ACCESS_ONCE(session->active));
 407
 408         va_start(ap, fmt);
 409         str = kvasprintf(GFP_KERNEL, fmt, ap);
 410         va_end(ap);
 411         if (!str)
 412                 return -ENOMEM;
 413
 414         len = strlen(str);
 415         pos = 0;
 416
 417         for (pos = 0; pos < len; pos += reserve_len) {
 418                 reserve_len = min_t(size_t,
 419                                 chan->ops->packet_avail_size(chan->chan),
 420                                 len - pos);
 421                 lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL, reserve_len,
 422                                          sizeof(char), -1);
 423                 /*
 424                  * We don't care about metadata buffer's records lost
 425                  * count, because we always retry here. Report error if
 426                  * we need to bail out after timeout or being
 427                  * interrupted.
 428                  */
 429                 waitret = wait_event_interruptible_timeout(*chan->ops->get_reader_wait_queue(chan->chan),
 430                         ({
 431                                 ret = chan->ops->event_reserve(&ctx, 0);
 432                                 ret != -ENOBUFS || !ret;
 433                         }),
 434                         msecs_to_jiffies(LTTNG_METADATA_TIMEOUT_MSEC));
 435                 if (!waitret || waitret == -ERESTARTSYS || ret) {
 436                         printk(KERN_WARNING "LTTng: Failure to write metadata to buffers (%s)\n",
 437                                 waitret == -ERESTARTSYS ? "interrupted" :
 438                                         (ret == -ENOBUFS ? "timeout" : "I/O error"));
 439                         if (waitret == -ERESTARTSYS)
 440                                 ret = waitret;
 441                         goto end;
 442                 }
 443                 chan->ops->event_write(&ctx, &str[pos], reserve_len);
 444                 chan->ops->event_commit(&ctx);
 445         }
 446 end:
 447         kfree(str);
 448         return ret;
 449 }
 450
 451 static
 452 int _ltt_field_statedump(struct ltt_session *session,
 453                          const struct lttng_event_field *field)
 454 {
 455         int ret = 0;
 456
 457         switch (field->type.atype) {
 458         case atype_integer:
 459                 ret = lttng_metadata_printf(session,
 460                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s;\n",
 461                         field->type.u.basic.integer.size,
 462                         field->type.u.basic.integer.alignment,
 463                         field->type.u.basic.integer.signedness,
 464                         (field->type.u.basic.integer.encoding == lttng_encode_none)
 465                                 ? "none"
 466                                 : (field->type.u.basic.integer.encoding == lttng_encode_UTF8)
 467                                         ? "UTF8"
 468                                         : "ASCII",
 469                         field->type.u.basic.integer.base,
 470 #ifdef __BIG_ENDIAN
 471                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 472 #else
 473                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 474 #endif
 475                         field->name);
 476                 break;
 477         case atype_enum:
 478                 ret = lttng_metadata_printf(session,
 479                         "               %s %s;\n",
 480                         field->type.u.basic.enumeration.name,
 481                         field->name);
 482                 break;
 483         case atype_array:
 484         {
 485                 const struct lttng_basic_type *elem_type;
 486
 487                 elem_type = &field->type.u.array.elem_type;
 488                 ret = lttng_metadata_printf(session,
 489                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s[%u];\n",
 490                         elem_type->u.basic.integer.size,
 491                         elem_type->u.basic.integer.alignment,
 492                         elem_type->u.basic.integer.signedness,
 493                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 494                                 ? "none"
 495                                 : (elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 496                                         ? "UTF8"
 497                                         : "ASCII",
 498                         elem_type->u.basic.integer.base,
 499 #ifdef __BIG_ENDIAN
 500                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 501 #else
 502                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 503 #endif
 504                         field->name, field->type.u.array.length);
 505                 break;
 506         }
 507         case atype_sequence:
 508         {
 509                 const struct lttng_basic_type *elem_type;
 510                 const struct lttng_basic_type *length_type;
 511
 512                 elem_type = &field->type.u.sequence.elem_type;
 513                 length_type = &field->type.u.sequence.length_type;
 514                 ret = lttng_metadata_printf(session,
 515                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
 516                         length_type->u.basic.integer.size,
 517                         (unsigned int) length_type->u.basic.integer.alignment,
 518                         length_type->u.basic.integer.signedness,
 519                         (length_type->u.basic.integer.encoding == lttng_encode_none)
 520                                 ? "none"
 521                                 : ((length_type->u.basic.integer.encoding == lttng_encode_UTF8)
 522                                         ? "UTF8"
 523                                         : "ASCII"),
 524                         length_type->u.basic.integer.base,
 525 #ifdef __BIG_ENDIAN
 526                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 527 #else
 528                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 529 #endif
 530                         field->name);
 531                 if (ret)
 532                         return ret;
 533
 534                 ret = lttng_metadata_printf(session,
 535                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s[ __%s_length ];\n",
 536                         elem_type->u.basic.integer.size,
 537                         (unsigned int) elem_type->u.basic.integer.alignment,
 538                         elem_type->u.basic.integer.signedness,
 539                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 540                                 ? "none"
 541                                 : ((elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 542                                         ? "UTF8"
 543                                         : "ASCII"),
 544                         elem_type->u.basic.integer.base,
 545 #ifdef __BIG_ENDIAN
 546                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 547 #else
 548                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 549 #endif
 550                         field->name,
 551                         field->name);
 552                 break;
 553         }
 554
 555         case atype_string:
 556                 /* Default encoding is UTF8 */
 557                 ret = lttng_metadata_printf(session,
 558                         "               string%s %s;\n",
 559                         field->type.u.basic.string.encoding == lttng_encode_ASCII ?
 560                                 " { encoding = ASCII; }" : "",
 561                         field->name);
 562                 break;
 563         default:
 564                 WARN_ON_ONCE(1);
 565                 return -EINVAL;
 566         }
 567         return ret;
 568 }
 569
 570 static
 571 int _ltt_context_metadata_statedump(struct ltt_session *session,
 572                                     struct lttng_ctx *ctx)
 573 {
 574         int ret = 0;
 575         int i;
 576
 577         if (!ctx)
 578                 return 0;
 579         for (i = 0; i < ctx->nr_fields; i++) {
 580                 const struct lttng_ctx_field *field = &ctx->fields[i];
 581
 582                 ret = _ltt_field_statedump(session, &field->event_field);
 583                 if (ret)
 584                         return ret;
 585         }
 586         return ret;
 587 }
 588
 589 static
 590 int _ltt_fields_metadata_statedump(struct ltt_session *session,
 591                                    struct ltt_event *event)
 592 {
 593         const struct lttng_event_desc *desc = event->desc;
 594         int ret = 0;
 595         int i;
 596
 597         for (i = 0; i < desc->nr_fields; i++) {
 598                 const struct lttng_event_field *field = &desc->fields[i];
 599
 600                 ret = _ltt_field_statedump(session, field);
 601                 if (ret)
 602                         return ret;
 603         }
 604         return ret;
 605 }
 606
 607 static
 608 int _ltt_event_metadata_statedump(struct ltt_session *session,
 609                                   struct ltt_channel *chan,
 610                                   struct ltt_event *event)
 611 {
 612         int ret = 0;
 613
 614         if (event->metadata_dumped || !ACCESS_ONCE(session->active))
 615                 return 0;
 616         if (chan == session->metadata)
 617                 return 0;
 618
 619         ret = lttng_metadata_printf(session,
 620                 "event {\n"
 621                 "       name = %s;\n"
 622                 "       id = %u;\n"
 623                 "       stream_id = %u;\n",
 624                 event->desc->name,
 625                 event->id,
 626                 event->chan->id);
 627         if (ret)
 628                 goto end;
 629
 630         if (event->ctx) {
 631                 ret = lttng_metadata_printf(session,
 632                         "       context := struct {\n");
 633                 if (ret)
 634                         goto end;
 635         }
 636         ret = _ltt_context_metadata_statedump(session, event->ctx);
 637         if (ret)
 638                 goto end;
 639         if (event->ctx) {
 640                 ret = lttng_metadata_printf(session,
 641                         "       };\n");
 642                 if (ret)
 643                         goto end;
 644         }
 645
 646         ret = lttng_metadata_printf(session,
 647                 "       fields := struct {\n"
 648                 );
 649         if (ret)
 650                 goto end;
 651
 652         ret = _ltt_fields_metadata_statedump(session, event);
 653         if (ret)
 654                 goto end;
 655
 656         /*
 657          * LTTng space reservation can only reserve multiples of the
 658          * byte size.
 659          */
 660         ret = lttng_metadata_printf(session,
 661                 "       };\n"
 662                 "};\n\n");
 663         if (ret)
 664                 goto end;
 665
 666         event->metadata_dumped = 1;
 667 end:
 668         return ret;
 669
 670 }
 671
 672 static
 673 int _ltt_channel_metadata_statedump(struct ltt_session *session,
 674                                     struct ltt_channel *chan)
 675 {
 676         int ret = 0;
 677
 678         if (chan->metadata_dumped || !ACCESS_ONCE(session->active))
 679                 return 0;
 680         if (chan == session->metadata)
 681                 return 0;
 682
 683         WARN_ON_ONCE(!chan->header_type);
 684         ret = lttng_metadata_printf(session,
 685                 "stream {\n"
 686                 "       id = %u;\n"
 687                 "       event.header := %s;\n"
 688                 "       packet.context := struct packet_context;\n",
 689                 chan->id,
 690                 chan->header_type == 1 ? "struct event_header_compact" :
 691                         "struct event_header_large");
 692         if (ret)
 693                 goto end;
 694
 695         if (chan->ctx) {
 696                 ret = lttng_metadata_printf(session,
 697                         "       event.context := struct {\n");
 698                 if (ret)
 699                         goto end;
 700         }
 701         ret = _ltt_context_metadata_statedump(session, chan->ctx);
 702         if (ret)
 703                 goto end;
 704         if (chan->ctx) {
 705                 ret = lttng_metadata_printf(session,
 706                         "       };\n");
 707                 if (ret)
 708                         goto end;
 709         }
 710
 711         ret = lttng_metadata_printf(session,
 712                 "};\n\n");
 713
 714         chan->metadata_dumped = 1;
 715 end:
 716         return ret;
 717 }
 718
 719 static
 720 int _ltt_stream_packet_context_declare(struct ltt_session *session)
 721 {
 722         return lttng_metadata_printf(session,
 723                 "struct packet_context {\n"
 724                 "       uint64_t timestamp_begin;\n"
 725                 "       uint64_t timestamp_end;\n"
 726                 "       uint32_t events_discarded;\n"
 727                 "       uint32_t content_size;\n"
 728                 "       uint32_t packet_size;\n"
 729                 "       uint32_t cpu_id;\n"
 730                 "};\n\n"
 731                 );
 732 }
 733
 734 /*
 735  * Compact header:
 736  * id: range: 0 - 30.
 737  * id 31 is reserved to indicate an extended header.
 738  *
 739  * Large header:
 740  * id: range: 0 - 65534.
 741  * id 65535 is reserved to indicate an extended header.
 742  */
 743 static
 744 int _ltt_event_header_declare(struct ltt_session *session)
 745 {
 746         return lttng_metadata_printf(session,
 747         "struct event_header_compact {\n"
 748         "       enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
 749         "       variant <id> {\n"
 750         "               struct {\n"
 751         "                       uint27_t timestamp;\n"
 752         "               } compact;\n"
 753         "               struct {\n"
 754         "                       uint32_t id;\n"
 755         "                       uint64_t timestamp;\n"
 756         "               } extended;\n"
 757         "       } v;\n"
 758         "} align(%u);\n"
 759         "\n"
 760         "struct event_header_large {\n"
 761         "       enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
 762         "       variant <id> {\n"
 763         "               struct {\n"
 764         "                       uint32_t timestamp;\n"
 765         "               } compact;\n"
 766         "               struct {\n"
 767         "                       uint32_t id;\n"
 768         "                       uint64_t timestamp;\n"
 769         "               } extended;\n"
 770         "       } v;\n"
 771         "} align(%u);\n\n",
 772         ltt_alignof(uint32_t) * CHAR_BIT,
 773         ltt_alignof(uint16_t) * CHAR_BIT
 774         );
 775 }
 776
 777 /*
 778  * Output metadata into this session's metadata buffers.
 779  */
 780 static
 781 int _ltt_session_metadata_statedump(struct ltt_session *session)
 782 {
 783         unsigned char *uuid_c = session->uuid.b;
 784         unsigned char uuid_s[37];
 785         struct ltt_channel *chan;
 786         struct ltt_event *event;
 787         int ret = 0;
 788
 789         if (!ACCESS_ONCE(session->active))
 790                 return 0;
 791         if (session->metadata_dumped)
 792                 goto skip_session;
 793         if (!session->metadata) {
 794                 printk(KERN_WARNING "LTTng: attempt to start tracing, but metadata channel is not found. Operation abort.\n");
 795                 return -EPERM;
 796         }
 797
 798         snprintf(uuid_s, sizeof(uuid_s),
 799                 "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
 800                 uuid_c[0], uuid_c[1], uuid_c[2], uuid_c[3],
 801                 uuid_c[4], uuid_c[5], uuid_c[6], uuid_c[7],
 802                 uuid_c[8], uuid_c[9], uuid_c[10], uuid_c[11],
 803                 uuid_c[12], uuid_c[13], uuid_c[14], uuid_c[15]);
 804
 805         ret = lttng_metadata_printf(session,
 806                 "typealias integer { size = 8; align = %u; signed = false; } := uint8_t;\n"
 807                 "typealias integer { size = 16; align = %u; signed = false; } := uint16_t;\n"
 808                 "typealias integer { size = 32; align = %u; signed = false; } := uint32_t;\n"
 809                 "typealias integer { size = 64; align = %u; signed = false; } := uint64_t;\n"
 810                 "typealias integer { size = 5; align = 1; signed = false; } := uint5_t;\n"
 811                 "typealias integer { size = 27; align = 1; signed = false; } := uint27_t;\n"
 812                 "\n"
 813                 "trace {\n"
 814                 "       major = %u;\n"
 815                 "       minor = %u;\n"
 816                 "       uuid = \"%s\";\n"
 817                 "       byte_order = %s;\n"
 818                 "       packet.header := struct {\n"
 819                 "               uint32_t magic;\n"
 820                 "               uint8_t  uuid[16];\n"
 821                 "               uint32_t stream_id;\n"
 822                 "       };\n"
 823                 "};\n\n",
 824                 ltt_alignof(uint8_t) * CHAR_BIT,
 825                 ltt_alignof(uint16_t) * CHAR_BIT,
 826                 ltt_alignof(uint32_t) * CHAR_BIT,
 827                 ltt_alignof(uint64_t) * CHAR_BIT,
 828                 CTF_VERSION_MAJOR,
 829                 CTF_VERSION_MINOR,
 830                 uuid_s,
 831 #ifdef __BIG_ENDIAN
 832                 "be"
 833 #else
 834                 "le"
 835 #endif
 836                 );
 837         if (ret)
 838                 goto end;
 839
 840         ret = _ltt_stream_packet_context_declare(session);
 841         if (ret)
 842                 goto end;
 843
 844         ret = _ltt_event_header_declare(session);
 845         if (ret)
 846                 goto end;
 847
 848 skip_session:
 849         list_for_each_entry(chan, &session->chan, list) {
 850                 ret = _ltt_channel_metadata_statedump(session, chan);
 851                 if (ret)
 852                         goto end;
 853         }
 854
 855         list_for_each_entry(event, &session->events, list) {
 856                 ret = _ltt_event_metadata_statedump(session, event->chan, event);
 857                 if (ret)
 858                         goto end;
 859         }
 860         session->metadata_dumped = 1;
 861 end:
 862         return ret;
 863 }
 864
 865 /**
 866  * ltt_transport_register - LTT transport registration
 867  * @transport: transport structure
 868  *
 869  * Registers a transport which can be used as output to extract the data out of
 870  * LTTng. The module calling this registration function must ensure that no
 871  * trap-inducing code will be executed by the transport functions. E.g.
 872  * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
 873  * is made visible to the transport function. This registration acts as a
 874  * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
 875  * after its registration must it synchronize the TLBs.
 876  */
 877 void ltt_transport_register(struct ltt_transport *transport)
 878 {
 879         /*
 880          * Make sure no page fault can be triggered by the module about to be
 881          * registered. We deal with this here so we don't have to call
 882          * vmalloc_sync_all() in each module's init.
 883          */
 884         wrapper_vmalloc_sync_all();
 885
 886         mutex_lock(&sessions_mutex);
 887         list_add_tail(&transport->node, &ltt_transport_list);
 888         mutex_unlock(&sessions_mutex);
 889 }
 890 EXPORT_SYMBOL_GPL(ltt_transport_register);
 891
 892 /**
 893  * ltt_transport_unregister - LTT transport unregistration
 894  * @transport: transport structure
 895  */
 896 void ltt_transport_unregister(struct ltt_transport *transport)
 897 {
 898         mutex_lock(&sessions_mutex);
 899         list_del(&transport->node);
 900         mutex_unlock(&sessions_mutex);
 901 }
 902 EXPORT_SYMBOL_GPL(ltt_transport_unregister);
 903
 904 static int __init ltt_events_init(void)
 905 {
 906         int ret;
 907
 908         event_cache = KMEM_CACHE(ltt_event, 0);
 909         if (!event_cache)
 910                 return -ENOMEM;
 911         ret = ltt_debugfs_abi_init();
 912         if (ret)
 913                 goto error_abi;
 914         return 0;
 915 error_abi:
 916         kmem_cache_destroy(event_cache);
 917         return ret;
 918 }
 919
 920 module_init(ltt_events_init);
 921
 922 static void __exit ltt_events_exit(void)
 923 {
 924         struct ltt_session *session, *tmpsession;
 925
 926         ltt_debugfs_abi_exit();
 927         list_for_each_entry_safe(session, tmpsession, &sessions, list)
 928                 ltt_session_destroy(session);
 929         kmem_cache_destroy(event_cache);
 930 }
 931
 932 module_exit(ltt_events_exit);
 933
 934 MODULE_LICENSE("GPL and additional rights");
 935 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 936 MODULE_DESCRIPTION("LTTng Events");