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 #define _GNU_SOURCE
  12 #include <stdio.h>
  13 #include <urcu/list.h>
  14 #include <urcu/hlist.h>
  15 #include <pthread.h>
  16 #include <urcu-bp.h>
  17 #include <urcu/compiler.h>
  18 #include <urcu/uatomic.h>
  19 #include <uuid/uuid.h>
  20 #include <ust/tracepoint.h>
  21 #include <errno.h>
  22 #include <sys/shm.h>
  23 #include <sys/ipc.h>
  24 #include <ust/lttng-events.h>
  25 #include <ust/usterr-signal-safe.h>
  26 #include "ust/core.h"
  27 #include "ltt-tracer.h"
  28 #include "ltt-tracer-core.h"
  29 #include "ust/wait.h"
  30 #include "../libringbuffer/shm.h"
  31
  32 typedef u32 uint32_t;
  33 #include <ust/kcompat/jhash.h>
  34
  35 /*
  36  * The sessions mutex is the centralized mutex across UST tracing
  37  * control and probe registration. All operations within this file are
  38  * called by the communication thread, under ust_lock protection.
  39  */
  40 static DEFINE_MUTEX(sessions_mutex);
  41
  42 void ust_lock(void)
  43 {
  44         pthread_mutex_lock(&sessions_mutex);
  45 }
  46
  47 void ust_unlock(void)
  48 {
  49         pthread_mutex_unlock(&sessions_mutex);
  50 }
  51
  52 static CDS_LIST_HEAD(sessions);
  53 static CDS_LIST_HEAD(ltt_transport_list);
  54
  55 /*
  56  * Pending probes hash table, containing the registered ltt events for
  57  * which tracepoint probes are still missing. Protected by the sessions
  58  * mutex.
  59  */
  60 #define PENDING_PROBE_HASH_BITS         6
  61 #define PENDING_PROBE_HASH_SIZE         (1 << PENDING_PROBE_HASH_BITS)
  62 static struct cds_hlist_head pending_probe_table[PENDING_PROBE_HASH_SIZE];
  63
  64 struct ust_pending_probe {
  65         struct ltt_event *event;
  66         struct cds_hlist_node node;
  67         char name[];
  68 };
  69
  70 static void _ltt_event_destroy(struct ltt_event *event);
  71 static void _ltt_channel_destroy(struct ltt_channel *chan);
  72 static int _ltt_event_unregister(struct ltt_event *event);
  73 static
  74 int _ltt_event_metadata_statedump(struct ltt_session *session,
  75                                   struct ltt_channel *chan,
  76                                   struct ltt_event *event);
  77 static
  78 int _ltt_session_metadata_statedump(struct ltt_session *session);
  79
  80 /*
  81  * called at event creation if probe is missing.
  82  * called with session mutex held.
  83  */
  84 static
  85 int add_pending_probe(struct ltt_event *event, const char *name)
  86 {
  87         struct cds_hlist_head *head;
  88         struct ust_pending_probe *e;
  89         size_t name_len = strlen(name) + 1;
  90         u32 hash = jhash(name, name_len - 1, 0);
  91
  92         head = &pending_probe_table[hash & (PENDING_PROBE_HASH_SIZE - 1)];
  93         e = zmalloc(sizeof(struct ust_pending_probe) + name_len);
  94         if (!e)
  95                 return -ENOMEM;
  96         memcpy(&e->name[0], name, name_len);
  97         cds_hlist_add_head(&e->node, head);
  98         e->event = event;
  99         event->pending_probe = e;
 100         return 0;
 101 }
 102
 103 /*
 104  * remove a pending probe. called when at event teardown and when an
 105  * event is fixed (probe is loaded).
 106  * called with session mutex held.
 107  */
 108 static
 109 void remove_pending_probe(struct ust_pending_probe *e)
 110 {
 111         if (!e)
 112                 return;
 113         cds_hlist_del(&e->node);
 114         free(e);
 115 }
 116
 117 /*
 118  * Called at library load: connect the probe on the events pending on
 119  * probe load.
 120  * called with session mutex held.
 121  */
 122 int pending_probe_fix_events(const struct lttng_event_desc *desc)
 123 {
 124         struct cds_hlist_head *head;
 125         struct cds_hlist_node *node, *p;
 126         struct ust_pending_probe *e;
 127         const char *name = desc->name;
 128         size_t name_len = strlen(name) + 1;
 129         u32 hash = jhash(name, name_len - 1, 0);
 130         int ret = 0;
 131
 132         head = &pending_probe_table[hash & (PENDING_PROBE_HASH_SIZE - 1)];
 133         cds_hlist_for_each_entry_safe(e, node, p, head, node) {
 134                 struct ltt_event *event;
 135                 struct ltt_channel *chan;
 136
 137                 if (strcmp(name, e->name))
 138                         continue;
 139                 event = e->event;
 140                 chan = event->chan;
 141                 assert(!event->desc);
 142                 event->desc = desc;
 143                 event->pending_probe = NULL;
 144                 remove_pending_probe(e);
 145                 ret |= __tracepoint_probe_register(name,
 146                                 event->desc->probe_callback,
 147                                 event);
 148                 ret |= _ltt_event_metadata_statedump(chan->session, chan,
 149                                 event);
 150         }
 151         return ret;
 152 }
 153
 154 void synchronize_trace(void)
 155 {
 156         synchronize_rcu();
 157 }
 158
 159 struct ltt_session *ltt_session_create(void)
 160 {
 161         struct ltt_session *session;
 162
 163         session = zmalloc(sizeof(struct ltt_session));
 164         if (!session)
 165                 return NULL;
 166         CDS_INIT_LIST_HEAD(&session->chan);
 167         CDS_INIT_LIST_HEAD(&session->events);
 168         uuid_generate(session->uuid);
 169         cds_list_add(&session->list, &sessions);
 170         return session;
 171 }
 172
 173 void ltt_session_destroy(struct ltt_session *session)
 174 {
 175         struct ltt_channel *chan, *tmpchan;
 176         struct ltt_event *event, *tmpevent;
 177         int ret;
 178
 179         CMM_ACCESS_ONCE(session->active) = 0;
 180         cds_list_for_each_entry(event, &session->events, list) {
 181                 ret = _ltt_event_unregister(event);
 182                 WARN_ON(ret);
 183         }
 184         synchronize_trace();    /* Wait for in-flight events to complete */
 185         cds_list_for_each_entry_safe(event, tmpevent, &session->events, list)
 186                 _ltt_event_destroy(event);
 187         cds_list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
 188                 _ltt_channel_destroy(chan);
 189         cds_list_del(&session->list);
 190         free(session);
 191 }
 192
 193 int ltt_session_enable(struct ltt_session *session)
 194 {
 195         int ret = 0;
 196         struct ltt_channel *chan;
 197
 198         if (session->active) {
 199                 ret = -EBUSY;
 200                 goto end;
 201         }
 202
 203         /*
 204          * Snapshot the number of events per channel to know the type of header
 205          * we need to use.
 206          */
 207         cds_list_for_each_entry(chan, &session->chan, list) {
 208                 if (chan->header_type)
 209                         continue;               /* don't change it if session stop/restart */
 210                 if (chan->free_event_id < 31)
 211                         chan->header_type = 1;  /* compact */
 212                 else
 213                         chan->header_type = 2;  /* large */
 214         }
 215
 216         CMM_ACCESS_ONCE(session->active) = 1;
 217         CMM_ACCESS_ONCE(session->been_active) = 1;
 218         ret = _ltt_session_metadata_statedump(session);
 219         if (ret)
 220                 CMM_ACCESS_ONCE(session->active) = 0;
 221 end:
 222         return ret;
 223 }
 224
 225 int ltt_session_disable(struct ltt_session *session)
 226 {
 227         int ret = 0;
 228
 229         if (!session->active) {
 230                 ret = -EBUSY;
 231                 goto end;
 232         }
 233         CMM_ACCESS_ONCE(session->active) = 0;
 234 end:
 235         return ret;
 236 }
 237
 238 int ltt_channel_enable(struct ltt_channel *channel)
 239 {
 240         int old;
 241
 242         if (channel == channel->session->metadata)
 243                 return -EPERM;
 244         old = uatomic_xchg(&channel->enabled, 1);
 245         if (old)
 246                 return -EEXIST;
 247         return 0;
 248 }
 249
 250 int ltt_channel_disable(struct ltt_channel *channel)
 251 {
 252         int old;
 253
 254         if (channel == channel->session->metadata)
 255                 return -EPERM;
 256         old = uatomic_xchg(&channel->enabled, 0);
 257         if (!old)
 258                 return -EEXIST;
 259         return 0;
 260 }
 261
 262 int ltt_event_enable(struct ltt_event *event)
 263 {
 264         int old;
 265
 266         if (event->chan == event->chan->session->metadata)
 267                 return -EPERM;
 268         old = uatomic_xchg(&event->enabled, 1);
 269         if (old)
 270                 return -EEXIST;
 271         return 0;
 272 }
 273
 274 int ltt_event_disable(struct ltt_event *event)
 275 {
 276         int old;
 277
 278         if (event->chan == event->chan->session->metadata)
 279                 return -EPERM;
 280         old = uatomic_xchg(&event->enabled, 0);
 281         if (!old)
 282                 return -EEXIST;
 283         return 0;
 284 }
 285
 286 static struct ltt_transport *ltt_transport_find(const char *name)
 287 {
 288         struct ltt_transport *transport;
 289
 290         cds_list_for_each_entry(transport, &ltt_transport_list, node) {
 291                 if (!strcmp(transport->name, name))
 292                         return transport;
 293         }
 294         return NULL;
 295 }
 296
 297 struct ltt_channel *ltt_channel_create(struct ltt_session *session,
 298                                        const char *transport_name,
 299                                        void *buf_addr,
 300                                        size_t subbuf_size, size_t num_subbuf,
 301                                        unsigned int switch_timer_interval,
 302                                        unsigned int read_timer_interval)
 303 {
 304         struct ltt_channel *chan;
 305         struct ltt_transport *transport;
 306
 307         if (session->been_active)
 308                 goto active;    /* Refuse to add channel to active session */
 309         transport = ltt_transport_find(transport_name);
 310         if (!transport) {
 311                 DBG("LTTng transport %s not found\n",
 312                        transport_name);
 313                 goto notransport;
 314         }
 315         chan = zmalloc(sizeof(struct ltt_channel));
 316         if (!chan)
 317                 goto nomem;
 318         chan->session = session;
 319         chan->id = session->free_chan_id++;
 320         /*
 321          * Note: the channel creation op already writes into the packet
 322          * headers. Therefore the "chan" information used as input
 323          * should be already accessible.
 324          */
 325         transport->ops.channel_create("[lttng]", chan, buf_addr,
 326                         subbuf_size, num_subbuf, switch_timer_interval,
 327                         read_timer_interval);
 328         if (!chan->chan)
 329                 goto create_error;
 330         chan->enabled = 1;
 331         chan->ops = &transport->ops;
 332         cds_list_add(&chan->list, &session->chan);
 333         return chan;
 334
 335 create_error:
 336         free(chan);
 337 nomem:
 338 notransport:
 339 active:
 340         return NULL;
 341 }
 342
 343 /*
 344  * Only used internally at session destruction.
 345  */
 346 static
 347 void _ltt_channel_destroy(struct ltt_channel *chan)
 348 {
 349         chan->ops->channel_destroy(chan);
 350         cds_list_del(&chan->list);
 351         lttng_destroy_context(chan->ctx);
 352         free(chan);
 353 }
 354
 355 /*
 356  * Supports event creation while tracing session is active.
 357  */
 358 struct ltt_event *ltt_event_create(struct ltt_channel *chan,
 359                                    struct lttng_ust_event *event_param,
 360                                    void *filter)
 361 {
 362         struct ltt_event *event;
 363         int ret;
 364
 365         if (chan->used_event_id == -1UL)
 366                 goto full;
 367         /*
 368          * This is O(n^2) (for each event, the loop is called at event
 369          * creation). Might require a hash if we have lots of events.
 370          */
 371         cds_list_for_each_entry(event, &chan->session->events, list)
 372                 if (event->desc && !strcmp(event->desc->name, event_param->name))
 373                         goto exist;
 374         event = zmalloc(sizeof(struct ltt_event));
 375         if (!event)
 376                 goto cache_error;
 377         event->chan = chan;
 378         event->filter = filter;
 379         /*
 380          * used_event_id counts the maximum number of event IDs that can
 381          * register if all probes register.
 382          */
 383         chan->used_event_id++;
 384         event->enabled = 1;
 385         event->instrumentation = event_param->instrumentation;
 386         /* Populate ltt_event structure before tracepoint registration. */
 387         cmm_smp_wmb();
 388         switch (event_param->instrumentation) {
 389         case LTTNG_UST_TRACEPOINT:
 390                 event->desc = ltt_event_get(event_param->name);
 391                 if (event->desc) {
 392                         ret = __tracepoint_probe_register(event_param->name,
 393                                         event->desc->probe_callback,
 394                                         event);
 395                         if (ret)
 396                                 goto register_error;
 397                         event->id = chan->free_event_id++;
 398                 } else {
 399                         /*
 400                          * If the probe is not present, event->desc stays NULL,
 401                          * waiting for the probe to register, and the event->id
 402                          * stays unallocated.
 403                          */
 404                         ret = add_pending_probe(event, event_param->name);
 405                         if (ret)
 406                                 goto add_pending_error;
 407                 }
 408                 break;
 409         default:
 410                 WARN_ON_ONCE(1);
 411         }
 412         if (event->desc) {
 413                 ret = _ltt_event_metadata_statedump(chan->session, chan, event);
 414                 if (ret)
 415                         goto statedump_error;
 416         }
 417         cds_list_add(&event->list, &chan->session->events);
 418         return event;
 419
 420 statedump_error:
 421         if (event->desc) {
 422                 WARN_ON_ONCE(__tracepoint_probe_unregister(event_param->name,
 423                                         event->desc->probe_callback,
 424                                         event));
 425                 ltt_event_put(event->desc);
 426         }
 427 add_pending_error:
 428 register_error:
 429         free(event);
 430 cache_error:
 431 exist:
 432 full:
 433         return NULL;
 434 }
 435
 436 /*
 437  * Only used internally at session destruction.
 438  */
 439 int _ltt_event_unregister(struct ltt_event *event)
 440 {
 441         int ret = -EINVAL;
 442
 443         switch (event->instrumentation) {
 444         case LTTNG_UST_TRACEPOINT:
 445                 if (event->desc) {
 446                         ret = __tracepoint_probe_unregister(event->desc->name,
 447                                                           event->desc->probe_callback,
 448                                                           event);
 449                         if (ret)
 450                                 return ret;
 451                 } else {
 452                         remove_pending_probe(event->pending_probe);
 453                         ret = 0;
 454                 }
 455                 break;
 456         default:
 457                 WARN_ON_ONCE(1);
 458         }
 459         return ret;
 460 }
 461
 462 /*
 463  * Only used internally at session destruction.
 464  */
 465 static
 466 void _ltt_event_destroy(struct ltt_event *event)
 467 {
 468         switch (event->instrumentation) {
 469         case LTTNG_UST_TRACEPOINT:
 470                 if (event->desc) {
 471                         ltt_event_put(event->desc);
 472                 }
 473                 break;
 474         default:
 475                 WARN_ON_ONCE(1);
 476         }
 477         cds_list_del(&event->list);
 478         lttng_destroy_context(event->ctx);
 479         free(event);
 480 }
 481
 482 /*
 483  * We have exclusive access to our metadata buffer (protected by the
 484  * ust_lock), so we can do racy operations such as looking for
 485  * remaining space left in packet and write, since mutual exclusion
 486  * protects us from concurrent writes.
 487  */
 488 int lttng_metadata_printf(struct ltt_session *session,
 489                           const char *fmt, ...)
 490 {
 491         struct lib_ring_buffer_ctx ctx;
 492         struct ltt_channel *chan = session->metadata;
 493         char *str = NULL;
 494         int ret = 0, waitret;
 495         size_t len, reserve_len, pos;
 496         va_list ap;
 497
 498         WARN_ON_ONCE(!CMM_ACCESS_ONCE(session->active));
 499
 500         va_start(ap, fmt);
 501         ret = vasprintf(&str, fmt, ap);
 502         va_end(ap);
 503         if (ret < 0)
 504                 return -ENOMEM;
 505
 506         len = strlen(str);
 507         pos = 0;
 508
 509         for (pos = 0; pos < len; pos += reserve_len) {
 510                 reserve_len = min_t(size_t,
 511                                 chan->ops->packet_avail_size(chan->chan, chan->handle),
 512                                 len - pos);
 513                 lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL, reserve_len,
 514                                          sizeof(char), -1, chan->handle);
 515                 /*
 516                  * We don't care about metadata buffer's records lost
 517                  * count, because we always retry here. Report error if
 518                  * we need to bail out after timeout or being
 519                  * interrupted.
 520                  */
 521                 waitret = wait_cond_interruptible_timeout(
 522                         ({
 523                                 ret = chan->ops->event_reserve(&ctx, 0);
 524                                 ret != -ENOBUFS || !ret;
 525                         }),
 526                         LTTNG_METADATA_TIMEOUT_MSEC);
 527                 if (waitret == -ETIMEDOUT || waitret == -EINTR || ret) {
 528                         DBG("LTTng: Failure to write metadata to buffers (%s)\n",
 529                                 waitret == -EINTR ? "interrupted" :
 530                                         (ret == -ENOBUFS ? "timeout" : "I/O error"));
 531                         if (waitret == -EINTR)
 532                                 ret = waitret;
 533                         goto end;
 534                 }
 535                 chan->ops->event_write(&ctx, &str[pos], reserve_len);
 536                 chan->ops->event_commit(&ctx);
 537         }
 538 end:
 539         free(str);
 540         return ret;
 541 }
 542
 543 static
 544 int _ltt_field_statedump(struct ltt_session *session,
 545                          const struct lttng_event_field *field)
 546 {
 547         int ret = 0;
 548
 549         switch (field->type.atype) {
 550         case atype_integer:
 551                 ret = lttng_metadata_printf(session,
 552                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s;\n",
 553                         field->type.u.basic.integer.size,
 554                         field->type.u.basic.integer.alignment,
 555                         field->type.u.basic.integer.signedness,
 556                         (field->type.u.basic.integer.encoding == lttng_encode_none)
 557                                 ? "none"
 558                                 : (field->type.u.basic.integer.encoding == lttng_encode_UTF8)
 559                                         ? "UTF8"
 560                                         : "ASCII",
 561                         field->type.u.basic.integer.base,
 562 #ifdef __BIG_ENDIAN
 563                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 564 #else
 565                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 566 #endif
 567                         field->name);
 568                 break;
 569         case atype_float:
 570                 ret = lttng_metadata_printf(session,
 571                         "               floating_point { exp_dig = %u; mant_dig = %u; align = %u; } %s;\n",
 572                         field->type.u.basic._float.exp_dig,
 573                         field->type.u.basic._float.mant_dig,
 574                         field->type.u.basic._float.alignment,
 575 #ifdef __BIG_ENDIAN
 576                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 577 #else
 578                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 579 #endif
 580                         field->name);
 581                 break;
 582         case atype_enum:
 583                 ret = lttng_metadata_printf(session,
 584                         "               %s %s;\n",
 585                         field->type.u.basic.enumeration.name,
 586                         field->name);
 587                 break;
 588         case atype_array:
 589         {
 590                 const struct lttng_basic_type *elem_type;
 591
 592                 elem_type = &field->type.u.array.elem_type;
 593                 ret = lttng_metadata_printf(session,
 594                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s[%u];\n",
 595                         elem_type->u.basic.integer.size,
 596                         elem_type->u.basic.integer.alignment,
 597                         elem_type->u.basic.integer.signedness,
 598                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 599                                 ? "none"
 600                                 : (elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 601                                         ? "UTF8"
 602                                         : "ASCII",
 603                         elem_type->u.basic.integer.base,
 604 #ifdef __BIG_ENDIAN
 605                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 606 #else
 607                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 608 #endif
 609                         field->name, field->type.u.array.length);
 610                 break;
 611         }
 612         case atype_sequence:
 613         {
 614                 const struct lttng_basic_type *elem_type;
 615                 const struct lttng_basic_type *length_type;
 616
 617                 elem_type = &field->type.u.sequence.elem_type;
 618                 length_type = &field->type.u.sequence.length_type;
 619                 ret = lttng_metadata_printf(session,
 620                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
 621                         length_type->u.basic.integer.size,
 622                         (unsigned int) length_type->u.basic.integer.alignment,
 623                         length_type->u.basic.integer.signedness,
 624                         (length_type->u.basic.integer.encoding == lttng_encode_none)
 625                                 ? "none"
 626                                 : ((length_type->u.basic.integer.encoding == lttng_encode_UTF8)
 627                                         ? "UTF8"
 628                                         : "ASCII"),
 629                         length_type->u.basic.integer.base,
 630 #ifdef __BIG_ENDIAN
 631                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 632 #else
 633                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 634 #endif
 635                         field->name);
 636                 if (ret)
 637                         return ret;
 638
 639                 ret = lttng_metadata_printf(session,
 640                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s[ __%s_length ];\n",
 641                         elem_type->u.basic.integer.size,
 642                         (unsigned int) elem_type->u.basic.integer.alignment,
 643                         elem_type->u.basic.integer.signedness,
 644                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 645                                 ? "none"
 646                                 : ((elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 647                                         ? "UTF8"
 648                                         : "ASCII"),
 649                         elem_type->u.basic.integer.base,
 650 #ifdef __BIG_ENDIAN
 651                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 652 #else
 653                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 654 #endif
 655                         field->name,
 656                         field->name);
 657                 break;
 658         }
 659
 660         case atype_string:
 661                 /* Default encoding is UTF8 */
 662                 ret = lttng_metadata_printf(session,
 663                         "               string%s %s;\n",
 664                         field->type.u.basic.string.encoding == lttng_encode_ASCII ?
 665                                 " { encoding = ASCII; }" : "",
 666                         field->name);
 667                 break;
 668         default:
 669                 WARN_ON_ONCE(1);
 670                 return -EINVAL;
 671         }
 672         return ret;
 673 }
 674
 675 static
 676 int _ltt_context_metadata_statedump(struct ltt_session *session,
 677                                     struct lttng_ctx *ctx)
 678 {
 679         int ret = 0;
 680         int i;
 681
 682         if (!ctx)
 683                 return 0;
 684         for (i = 0; i < ctx->nr_fields; i++) {
 685                 const struct lttng_ctx_field *field = &ctx->fields[i];
 686
 687                 ret = _ltt_field_statedump(session, &field->event_field);
 688                 if (ret)
 689                         return ret;
 690         }
 691         return ret;
 692 }
 693
 694 static
 695 int _ltt_fields_metadata_statedump(struct ltt_session *session,
 696                                    struct ltt_event *event)
 697 {
 698         const struct lttng_event_desc *desc = event->desc;
 699         int ret = 0;
 700         int i;
 701
 702         for (i = 0; i < desc->nr_fields; i++) {
 703                 const struct lttng_event_field *field = &desc->fields[i];
 704
 705                 ret = _ltt_field_statedump(session, field);
 706                 if (ret)
 707                         return ret;
 708         }
 709         return ret;
 710 }
 711
 712 static
 713 int _ltt_event_metadata_statedump(struct ltt_session *session,
 714                                   struct ltt_channel *chan,
 715                                   struct ltt_event *event)
 716 {
 717         int ret = 0;
 718
 719         if (event->metadata_dumped || !CMM_ACCESS_ONCE(session->active))
 720                 return 0;
 721         if (chan == session->metadata)
 722                 return 0;
 723         /*
 724          * Don't print events for which probe load is pending.
 725          */
 726         if (!event->desc)
 727                 return 0;
 728
 729         ret = lttng_metadata_printf(session,
 730                 "event {\n"
 731                 "       name = %s;\n"
 732                 "       id = %u;\n"
 733                 "       stream_id = %u;\n",
 734                 event->desc->name,
 735                 event->id,
 736                 event->chan->id);
 737         if (ret)
 738                 goto end;
 739
 740         if (event->ctx) {
 741                 ret = lttng_metadata_printf(session,
 742                         "       context := struct {\n");
 743                 if (ret)
 744                         goto end;
 745         }
 746         ret = _ltt_context_metadata_statedump(session, event->ctx);
 747         if (ret)
 748                 goto end;
 749         if (event->ctx) {
 750                 ret = lttng_metadata_printf(session,
 751                         "       };\n");
 752                 if (ret)
 753                         goto end;
 754         }
 755
 756         ret = lttng_metadata_printf(session,
 757                 "       fields := struct {\n"
 758                 );
 759         if (ret)
 760                 goto end;
 761
 762         ret = _ltt_fields_metadata_statedump(session, event);
 763         if (ret)
 764                 goto end;
 765
 766         /*
 767          * LTTng space reservation can only reserve multiples of the
 768          * byte size.
 769          */
 770         ret = lttng_metadata_printf(session,
 771                 "       };\n"
 772                 "};\n\n");
 773         if (ret)
 774                 goto end;
 775
 776         event->metadata_dumped = 1;
 777 end:
 778         return ret;
 779
 780 }
 781
 782 static
 783 int _ltt_channel_metadata_statedump(struct ltt_session *session,
 784                                     struct ltt_channel *chan)
 785 {
 786         int ret = 0;
 787
 788         if (chan->metadata_dumped || !CMM_ACCESS_ONCE(session->active))
 789                 return 0;
 790         if (chan == session->metadata)
 791                 return 0;
 792
 793         WARN_ON_ONCE(!chan->header_type);
 794         ret = lttng_metadata_printf(session,
 795                 "stream {\n"
 796                 "       id = %u;\n"
 797                 "       event.header := %s;\n"
 798                 "       packet.context := struct packet_context;\n",
 799                 chan->id,
 800                 chan->header_type == 1 ? "struct event_header_compact" :
 801                         "struct event_header_large");
 802         if (ret)
 803                 goto end;
 804
 805         if (chan->ctx) {
 806                 ret = lttng_metadata_printf(session,
 807                         "       event.context := struct {\n");
 808                 if (ret)
 809                         goto end;
 810         }
 811         ret = _ltt_context_metadata_statedump(session, chan->ctx);
 812         if (ret)
 813                 goto end;
 814         if (chan->ctx) {
 815                 ret = lttng_metadata_printf(session,
 816                         "       };\n");
 817                 if (ret)
 818                         goto end;
 819         }
 820
 821         ret = lttng_metadata_printf(session,
 822                 "};\n\n");
 823
 824         chan->metadata_dumped = 1;
 825 end:
 826         return ret;
 827 }
 828
 829 static
 830 int _ltt_stream_packet_context_declare(struct ltt_session *session)
 831 {
 832         return lttng_metadata_printf(session,
 833                 "struct packet_context {\n"
 834                 "       uint64_t timestamp_begin;\n"
 835                 "       uint64_t timestamp_end;\n"
 836                 "       uint32_t events_discarded;\n"
 837                 "       uint32_t content_size;\n"
 838                 "       uint32_t packet_size;\n"
 839                 "       uint32_t cpu_id;\n"
 840                 "};\n\n"
 841                 );
 842 }
 843
 844 /*
 845  * Compact header:
 846  * id: range: 0 - 30.
 847  * id 31 is reserved to indicate an extended header.
 848  *
 849  * Large header:
 850  * id: range: 0 - 65534.
 851  * id 65535 is reserved to indicate an extended header.
 852  */
 853 static
 854 int _ltt_event_header_declare(struct ltt_session *session)
 855 {
 856         return lttng_metadata_printf(session,
 857         "struct event_header_compact {\n"
 858         "       enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
 859         "       variant <id> {\n"
 860         "               struct {\n"
 861         "                       uint27_t timestamp;\n"
 862         "               } compact;\n"
 863         "               struct {\n"
 864         "                       uint32_t id;\n"
 865         "                       uint64_t timestamp;\n"
 866         "               } extended;\n"
 867         "       } v;\n"
 868         "} align(%u);\n"
 869         "\n"
 870         "struct event_header_large {\n"
 871         "       enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
 872         "       variant <id> {\n"
 873         "               struct {\n"
 874         "                       uint32_t timestamp;\n"
 875         "               } compact;\n"
 876         "               struct {\n"
 877         "                       uint32_t id;\n"
 878         "                       uint64_t timestamp;\n"
 879         "               } extended;\n"
 880         "       } v;\n"
 881         "} align(%u);\n\n",
 882         lttng_alignof(uint32_t) * CHAR_BIT,
 883         lttng_alignof(uint16_t) * CHAR_BIT
 884         );
 885 }
 886
 887 /*
 888  * Output metadata into this session's metadata buffers.
 889  */
 890 static
 891 int _ltt_session_metadata_statedump(struct ltt_session *session)
 892 {
 893         unsigned char *uuid_c = session->uuid;
 894         char uuid_s[37];
 895         struct ltt_channel *chan;
 896         struct ltt_event *event;
 897         int ret = 0;
 898
 899         if (!CMM_ACCESS_ONCE(session->active))
 900                 return 0;
 901         if (session->metadata_dumped)
 902                 goto skip_session;
 903         if (!session->metadata) {
 904                 DBG("LTTng: attempt to start tracing, but metadata channel is not found. Operation abort.\n");
 905                 return -EPERM;
 906         }
 907
 908         snprintf(uuid_s, sizeof(uuid_s),
 909                 "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
 910                 uuid_c[0], uuid_c[1], uuid_c[2], uuid_c[3],
 911                 uuid_c[4], uuid_c[5], uuid_c[6], uuid_c[7],
 912                 uuid_c[8], uuid_c[9], uuid_c[10], uuid_c[11],
 913                 uuid_c[12], uuid_c[13], uuid_c[14], uuid_c[15]);
 914
 915         ret = lttng_metadata_printf(session,
 916                 "typealias integer { size = 8; align = %u; signed = false; } := uint8_t;\n"
 917                 "typealias integer { size = 16; align = %u; signed = false; } := uint16_t;\n"
 918                 "typealias integer { size = 32; align = %u; signed = false; } := uint32_t;\n"
 919                 "typealias integer { size = 64; align = %u; signed = false; } := uint64_t;\n"
 920                 "typealias integer { size = 5; align = 1; signed = false; } := uint5_t;\n"
 921                 "typealias integer { size = 27; align = 1; signed = false; } := uint27_t;\n"
 922                 "\n"
 923                 "trace {\n"
 924                 "       major = %u;\n"
 925                 "       minor = %u;\n"
 926                 "       uuid = \"%s\";\n"
 927                 "       byte_order = %s;\n"
 928                 "       packet.header := struct {\n"
 929                 "               uint32_t magic;\n"
 930                 "               uint8_t  uuid[16];\n"
 931                 "               uint32_t stream_id;\n"
 932                 "       };\n"
 933                 "};\n\n",
 934                 lttng_alignof(uint8_t) * CHAR_BIT,
 935                 lttng_alignof(uint16_t) * CHAR_BIT,
 936                 lttng_alignof(uint32_t) * CHAR_BIT,
 937                 lttng_alignof(uint64_t) * CHAR_BIT,
 938                 CTF_VERSION_MAJOR,
 939                 CTF_VERSION_MINOR,
 940                 uuid_s,
 941 #ifdef __BIG_ENDIAN
 942                 "be"
 943 #else
 944                 "le"
 945 #endif
 946                 );
 947         if (ret)
 948                 goto end;
 949
 950         ret = _ltt_stream_packet_context_declare(session);
 951         if (ret)
 952                 goto end;
 953
 954         ret = _ltt_event_header_declare(session);
 955         if (ret)
 956                 goto end;
 957
 958 skip_session:
 959         cds_list_for_each_entry(chan, &session->chan, list) {
 960                 ret = _ltt_channel_metadata_statedump(session, chan);
 961                 if (ret)
 962                         goto end;
 963         }
 964
 965         cds_list_for_each_entry(event, &session->events, list) {
 966                 ret = _ltt_event_metadata_statedump(session, event->chan, event);
 967                 if (ret)
 968                         goto end;
 969         }
 970         session->metadata_dumped = 1;
 971 end:
 972         return ret;
 973 }
 974
 975 /**
 976  * ltt_transport_register - LTT transport registration
 977  * @transport: transport structure
 978  *
 979  * Registers a transport which can be used as output to extract the data out of
 980  * LTTng. Called with ust_lock held.
 981  */
 982 void ltt_transport_register(struct ltt_transport *transport)
 983 {
 984         cds_list_add_tail(&transport->node, &ltt_transport_list);
 985 }
 986
 987 /**
 988  * ltt_transport_unregister - LTT transport unregistration
 989  * @transport: transport structure
 990  * Called with ust_lock held.
 991  */
 992 void ltt_transport_unregister(struct ltt_transport *transport)
 993 {
 994         cds_list_del(&transport->node);
 995 }
 996
 997 void ltt_events_exit(void)
 998 {
 999         struct ltt_session *session, *tmpsession;
1000
1001         cds_list_for_each_entry_safe(session, tmpsession, &sessions, list)
1002                 ltt_session_destroy(session);
1003 }