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