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