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