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