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 #include <linux/module.h>
  12 #include <linux/list.h>
  13 #include <linux/mutex.h>
  14 #include <linux/sched.h>
  15 #include <linux/slab.h>
  16 #include <linux/jiffies.h>
  17 #include "wrapper/uuid.h"
  18 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  19 #include "ltt-events.h"
  20 #include "ltt-tracer.h"
  21
  22 static LIST_HEAD(sessions);
  23 static LIST_HEAD(ltt_transport_list);
  24 static DEFINE_MUTEX(sessions_mutex);
  25 static struct kmem_cache *event_cache;
  26
  27 static void _ltt_event_destroy(struct ltt_event *event);
  28 static void _ltt_channel_destroy(struct ltt_channel *chan);
  29 static int _ltt_event_unregister(struct ltt_event *event);
  30 static
  31 int _ltt_event_metadata_statedump(struct ltt_session *session,
  32                                   struct ltt_channel *chan,
  33                                   struct ltt_event *event);
  34 static
  35 int _ltt_session_metadata_statedump(struct ltt_session *session);
  36
  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_enable(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         ret = _ltt_session_metadata_statedump(session);
 110         if (ret)
 111                 ACCESS_ONCE(session->active) = 0;
 112 end:
 113         mutex_unlock(&sessions_mutex);
 114         return ret;
 115 }
 116
 117 int ltt_session_disable(struct ltt_session *session)
 118 {
 119         int ret = 0;
 120
 121         mutex_lock(&sessions_mutex);
 122         if (!session->active) {
 123                 ret = -EBUSY;
 124                 goto end;
 125         }
 126         ACCESS_ONCE(session->active) = 0;
 127 end:
 128         mutex_unlock(&sessions_mutex);
 129         return ret;
 130 }
 131
 132 int ltt_channel_enable(struct ltt_channel *channel)
 133 {
 134         int old;
 135
 136         if (channel == channel->session->metadata)
 137                 return -EPERM;
 138         old = xchg(&channel->enabled, 1);
 139         if (old)
 140                 return -EEXIST;
 141         return 0;
 142 }
 143
 144 int ltt_channel_disable(struct ltt_channel *channel)
 145 {
 146         int old;
 147
 148         if (channel == channel->session->metadata)
 149                 return -EPERM;
 150         old = xchg(&channel->enabled, 0);
 151         if (!old)
 152                 return -EEXIST;
 153         return 0;
 154 }
 155
 156 int ltt_event_enable(struct ltt_event *event)
 157 {
 158         int old;
 159
 160         if (event->chan == event->chan->session->metadata)
 161                 return -EPERM;
 162         old = xchg(&event->enabled, 1);
 163         if (old)
 164                 return -EEXIST;
 165         return 0;
 166 }
 167
 168 int ltt_event_disable(struct ltt_event *event)
 169 {
 170         int old;
 171
 172         if (event->chan == event->chan->session->metadata)
 173                 return -EPERM;
 174         old = xchg(&event->enabled, 0);
 175         if (!old)
 176                 return -EEXIST;
 177         return 0;
 178 }
 179
 180 static struct ltt_transport *ltt_transport_find(const char *name)
 181 {
 182         struct ltt_transport *transport;
 183
 184         list_for_each_entry(transport, &ltt_transport_list, node) {
 185                 if (!strcmp(transport->name, name))
 186                         return transport;
 187         }
 188         return NULL;
 189 }
 190
 191 struct ltt_channel *ltt_channel_create(struct ltt_session *session,
 192                                        const char *transport_name,
 193                                        void *buf_addr,
 194                                        size_t subbuf_size, size_t num_subbuf,
 195                                        unsigned int switch_timer_interval,
 196                                        unsigned int read_timer_interval)
 197 {
 198         struct ltt_channel *chan;
 199         struct ltt_transport *transport = NULL;
 200
 201         mutex_lock(&sessions_mutex);
 202         if (session->been_active)
 203                 goto active;    /* Refuse to add channel to active session */
 204         transport = ltt_transport_find(transport_name);
 205         if (!transport) {
 206                 printk(KERN_WARNING "LTTng transport %s not found\n",
 207                        transport_name);
 208                 goto notransport;
 209         }
 210         if (!try_module_get(transport->owner)) {
 211                 printk(KERN_WARNING "LTT : Can't lock transport module.\n");
 212                 goto notransport;
 213         }
 214         chan = kzalloc(sizeof(struct ltt_channel), GFP_KERNEL);
 215         if (!chan)
 216                 goto nomem;
 217         chan->session = session;
 218         chan->id = session->free_chan_id++;
 219         /*
 220          * Note: the channel creation op already writes into the packet
 221          * headers. Therefore the "chan" information used as input
 222          * should be already accessible.
 223          */
 224         chan->chan = transport->ops.channel_create("[lttng]", chan, buf_addr,
 225                         subbuf_size, num_subbuf, switch_timer_interval,
 226                         read_timer_interval);
 227         if (!chan->chan)
 228                 goto create_error;
 229         chan->enabled = 1;
 230         chan->ops = &transport->ops;
 231         chan->transport = transport;
 232         list_add(&chan->list, &session->chan);
 233         mutex_unlock(&sessions_mutex);
 234         return chan;
 235
 236 create_error:
 237         kfree(chan);
 238 nomem:
 239         if (transport)
 240                 module_put(transport->owner);
 241 notransport:
 242 active:
 243         mutex_unlock(&sessions_mutex);
 244         return NULL;
 245 }
 246
 247 /*
 248  * Only used internally at session destruction.
 249  */
 250 static
 251 void _ltt_channel_destroy(struct ltt_channel *chan)
 252 {
 253         chan->ops->channel_destroy(chan->chan);
 254         module_put(chan->transport->owner);
 255         list_del(&chan->list);
 256         lttng_destroy_context(chan->ctx);
 257         kfree(chan);
 258 }
 259
 260 /*
 261  * Supports event creation while tracing session is active.
 262  */
 263 struct ltt_event *ltt_event_create(struct ltt_channel *chan,
 264                                    struct lttng_kernel_event *event_param,
 265                                    void *filter)
 266 {
 267         struct ltt_event *event;
 268         int ret;
 269
 270         mutex_lock(&sessions_mutex);
 271         if (chan->free_event_id == -1UL)
 272                 goto full;
 273         /*
 274          * This is O(n^2) (for each event, the loop is called at event
 275          * creation). Might require a hash if we have lots of events.
 276          */
 277         list_for_each_entry(event, &chan->session->events, list)
 278                 if (!strcmp(event->desc->name, event_param->name))
 279                         goto exist;
 280         event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
 281         if (!event)
 282                 goto cache_error;
 283         event->chan = chan;
 284         event->filter = filter;
 285         event->id = chan->free_event_id++;
 286         event->enabled = 1;
 287         event->instrumentation = event_param->instrumentation;
 288         /* Populate ltt_event structure before tracepoint registration. */
 289         smp_wmb();
 290         switch (event_param->instrumentation) {
 291         case LTTNG_KERNEL_TRACEPOINT:
 292                 event->desc = ltt_event_get(event_param->name);
 293                 if (!event->desc)
 294                         goto register_error;
 295                 ret = tracepoint_probe_register(event_param->name,
 296                                 event->desc->probe_callback,
 297                                 event);
 298                 if (ret)
 299                         goto register_error;
 300                 break;
 301         case LTTNG_KERNEL_KPROBE:
 302                 ret = lttng_kprobes_register(event_param->name,
 303                                 event_param->u.kprobe.symbol_name,
 304                                 event_param->u.kprobe.offset,
 305                                 event_param->u.kprobe.addr,
 306                                 event);
 307                 if (ret)
 308                         goto register_error;
 309                 ret = try_module_get(event->desc->owner);
 310                 WARN_ON_ONCE(!ret);
 311                 break;
 312         case LTTNG_KERNEL_KRETPROBE:
 313         {
 314                 struct ltt_event *event_return;
 315
 316                 /* kretprobe defines 2 events */
 317                 event_return =
 318                         kmem_cache_zalloc(event_cache, GFP_KERNEL);
 319                 if (!event_return)
 320                         goto register_error;
 321                 event_return->chan = chan;
 322                 event_return->filter = filter;
 323                 event_return->id = chan->free_event_id++;
 324                 event_return->enabled = 1;
 325                 event_return->instrumentation = event_param->instrumentation;
 326                 /*
 327                  * Populate ltt_event structure before kretprobe registration.
 328                  */
 329                 smp_wmb();
 330                 ret = lttng_kretprobes_register(event_param->name,
 331                                 event_param->u.kretprobe.symbol_name,
 332                                 event_param->u.kretprobe.offset,
 333                                 event_param->u.kretprobe.addr,
 334                                 event, event_return);
 335                 if (ret) {
 336                         kmem_cache_free(event_cache, event_return);
 337                         goto register_error;
 338                 }
 339                 /* Take 2 refs on the module: one per event. */
 340                 ret = try_module_get(event->desc->owner);
 341                 WARN_ON_ONCE(!ret);
 342                 ret = try_module_get(event->desc->owner);
 343                 WARN_ON_ONCE(!ret);
 344                 ret = _ltt_event_metadata_statedump(chan->session, chan,
 345                                                     event_return);
 346                 if (ret) {
 347                         kmem_cache_free(event_cache, event_return);
 348                         module_put(event->desc->owner);
 349                         module_put(event->desc->owner);
 350                         goto statedump_error;
 351                 }
 352                 list_add(&event_return->list, &chan->session->events);
 353                 break;
 354         }
 355         case LTTNG_KERNEL_FUNCTION:
 356                 ret = lttng_ftrace_register(event_param->name,
 357                                 event_param->u.ftrace.symbol_name,
 358                                 event);
 359                 if (ret)
 360                         goto register_error;
 361                 ret = try_module_get(event->desc->owner);
 362                 WARN_ON_ONCE(!ret);
 363                 break;
 364         default:
 365                 WARN_ON_ONCE(1);
 366         }
 367         ret = _ltt_event_metadata_statedump(chan->session, chan, event);
 368         if (ret)
 369                 goto statedump_error;
 370         list_add(&event->list, &chan->session->events);
 371         mutex_unlock(&sessions_mutex);
 372         return event;
 373
 374 statedump_error:
 375         WARN_ON_ONCE(tracepoint_probe_unregister(event_param->name,
 376                                 event->desc->probe_callback,
 377                                 event));
 378         ltt_event_put(event->desc);
 379 register_error:
 380         kmem_cache_free(event_cache, event);
 381 cache_error:
 382 exist:
 383 full:
 384         mutex_unlock(&sessions_mutex);
 385         return NULL;
 386 }
 387
 388 /*
 389  * Only used internally at session destruction.
 390  */
 391 int _ltt_event_unregister(struct ltt_event *event)
 392 {
 393         int ret = -EINVAL;
 394
 395         switch (event->instrumentation) {
 396         case LTTNG_KERNEL_TRACEPOINT:
 397                 ret = tracepoint_probe_unregister(event->desc->name,
 398                                                   event->desc->probe_callback,
 399                                                   event);
 400                 if (ret)
 401                         return ret;
 402                 break;
 403         case LTTNG_KERNEL_KPROBE:
 404                 lttng_kprobes_unregister(event);
 405                 ret = 0;
 406                 break;
 407         case LTTNG_KERNEL_KRETPROBE:
 408                 lttng_kretprobes_unregister(event);
 409                 ret = 0;
 410                 break;
 411         case LTTNG_KERNEL_FUNCTION:
 412                 lttng_ftrace_unregister(event);
 413                 ret = 0;
 414                 break;
 415         default:
 416                 WARN_ON_ONCE(1);
 417         }
 418         return ret;
 419 }
 420
 421 /*
 422  * Only used internally at session destruction.
 423  */
 424 static
 425 void _ltt_event_destroy(struct ltt_event *event)
 426 {
 427         switch (event->instrumentation) {
 428         case LTTNG_KERNEL_TRACEPOINT:
 429                 ltt_event_put(event->desc);
 430                 break;
 431         case LTTNG_KERNEL_KPROBE:
 432                 module_put(event->desc->owner);
 433                 lttng_kprobes_destroy_private(event);
 434                 break;
 435         case LTTNG_KERNEL_KRETPROBE:
 436                 module_put(event->desc->owner);
 437                 lttng_kretprobes_destroy_private(event);
 438                 break;
 439         case LTTNG_KERNEL_FUNCTION:
 440                 module_put(event->desc->owner);
 441                 lttng_ftrace_destroy_private(event);
 442                 break;
 443         default:
 444                 WARN_ON_ONCE(1);
 445         }
 446         list_del(&event->list);
 447         lttng_destroy_context(event->ctx);
 448         kmem_cache_free(event_cache, event);
 449 }
 450
 451 /*
 452  * We have exclusive access to our metadata buffer (protected by the
 453  * sessions_mutex), so we can do racy operations such as looking for
 454  * remaining space left in packet and write, since mutual exclusion
 455  * protects us from concurrent writes.
 456  */
 457 int lttng_metadata_printf(struct ltt_session *session,
 458                           const char *fmt, ...)
 459 {
 460         struct lib_ring_buffer_ctx ctx;
 461         struct ltt_channel *chan = session->metadata;
 462         char *str;
 463         int ret = 0, waitret;
 464         size_t len, reserve_len, pos;
 465         va_list ap;
 466
 467         WARN_ON_ONCE(!ACCESS_ONCE(session->active));
 468
 469         va_start(ap, fmt);
 470         str = kvasprintf(GFP_KERNEL, fmt, ap);
 471         va_end(ap);
 472         if (!str)
 473                 return -ENOMEM;
 474
 475         len = strlen(str);
 476         pos = 0;
 477
 478         for (pos = 0; pos < len; pos += reserve_len) {
 479                 reserve_len = min_t(size_t,
 480                                 chan->ops->packet_avail_size(chan->chan),
 481                                 len - pos);
 482                 lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL, reserve_len,
 483                                          sizeof(char), -1);
 484                 /*
 485                  * We don't care about metadata buffer's records lost
 486                  * count, because we always retry here. Report error if
 487                  * we need to bail out after timeout or being
 488                  * interrupted.
 489                  */
 490                 waitret = wait_event_interruptible_timeout(*chan->ops->get_writer_buf_wait_queue(chan->chan, -1),
 491                         ({
 492                                 ret = chan->ops->event_reserve(&ctx, 0);
 493                                 ret != -ENOBUFS || !ret;
 494                         }),
 495                         msecs_to_jiffies(LTTNG_METADATA_TIMEOUT_MSEC));
 496                 if (!waitret || waitret == -ERESTARTSYS || ret) {
 497                         printk(KERN_WARNING "LTTng: Failure to write metadata to buffers (%s)\n",
 498                                 waitret == -ERESTARTSYS ? "interrupted" :
 499                                         (ret == -ENOBUFS ? "timeout" : "I/O error"));
 500                         if (waitret == -ERESTARTSYS)
 501                                 ret = waitret;
 502                         goto end;
 503                 }
 504                 chan->ops->event_write(&ctx, &str[pos], reserve_len);
 505                 chan->ops->event_commit(&ctx);
 506         }
 507 end:
 508         kfree(str);
 509         return ret;
 510 }
 511
 512 static
 513 int _ltt_field_statedump(struct ltt_session *session,
 514                          const struct lttng_event_field *field)
 515 {
 516         int ret = 0;
 517
 518         switch (field->type.atype) {
 519         case atype_integer:
 520                 ret = lttng_metadata_printf(session,
 521                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s;\n",
 522                         field->type.u.basic.integer.size,
 523                         field->type.u.basic.integer.alignment,
 524                         field->type.u.basic.integer.signedness,
 525                         (field->type.u.basic.integer.encoding == lttng_encode_none)
 526                                 ? "none"
 527                                 : (field->type.u.basic.integer.encoding == lttng_encode_UTF8)
 528                                         ? "UTF8"
 529                                         : "ASCII",
 530                         field->type.u.basic.integer.base,
 531 #ifdef __BIG_ENDIAN
 532                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 533 #else
 534                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 535 #endif
 536                         field->name);
 537                 break;
 538         case atype_enum:
 539                 ret = lttng_metadata_printf(session,
 540                         "               %s %s;\n",
 541                         field->type.u.basic.enumeration.name,
 542                         field->name);
 543                 break;
 544         case atype_array:
 545         {
 546                 const struct lttng_basic_type *elem_type;
 547
 548                 elem_type = &field->type.u.array.elem_type;
 549                 ret = lttng_metadata_printf(session,
 550                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s[%u];\n",
 551                         elem_type->u.basic.integer.size,
 552                         elem_type->u.basic.integer.alignment,
 553                         elem_type->u.basic.integer.signedness,
 554                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 555                                 ? "none"
 556                                 : (elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 557                                         ? "UTF8"
 558                                         : "ASCII",
 559                         elem_type->u.basic.integer.base,
 560 #ifdef __BIG_ENDIAN
 561                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 562 #else
 563                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 564 #endif
 565                         field->name, field->type.u.array.length);
 566                 break;
 567         }
 568         case atype_sequence:
 569         {
 570                 const struct lttng_basic_type *elem_type;
 571                 const struct lttng_basic_type *length_type;
 572
 573                 elem_type = &field->type.u.sequence.elem_type;
 574                 length_type = &field->type.u.sequence.length_type;
 575                 ret = lttng_metadata_printf(session,
 576                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
 577                         length_type->u.basic.integer.size,
 578                         (unsigned int) length_type->u.basic.integer.alignment,
 579                         length_type->u.basic.integer.signedness,
 580                         (length_type->u.basic.integer.encoding == lttng_encode_none)
 581                                 ? "none"
 582                                 : ((length_type->u.basic.integer.encoding == lttng_encode_UTF8)
 583                                         ? "UTF8"
 584                                         : "ASCII"),
 585                         length_type->u.basic.integer.base,
 586 #ifdef __BIG_ENDIAN
 587                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 588 #else
 589                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 590 #endif
 591                         field->name);
 592                 if (ret)
 593                         return ret;
 594
 595                 ret = lttng_metadata_printf(session,
 596                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } %s[ __%s_length ];\n",
 597                         elem_type->u.basic.integer.size,
 598                         (unsigned int) elem_type->u.basic.integer.alignment,
 599                         elem_type->u.basic.integer.signedness,
 600                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 601                                 ? "none"
 602                                 : ((elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 603                                         ? "UTF8"
 604                                         : "ASCII"),
 605                         elem_type->u.basic.integer.base,
 606 #ifdef __BIG_ENDIAN
 607                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 608 #else
 609                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 610 #endif
 611                         field->name,
 612                         field->name);
 613                 break;
 614         }
 615
 616         case atype_string:
 617                 /* Default encoding is UTF8 */
 618                 ret = lttng_metadata_printf(session,
 619                         "               string%s %s;\n",
 620                         field->type.u.basic.string.encoding == lttng_encode_ASCII ?
 621                                 " { encoding = ASCII; }" : "",
 622                         field->name);
 623                 break;
 624         default:
 625                 WARN_ON_ONCE(1);
 626                 return -EINVAL;
 627         }
 628         return ret;
 629 }
 630
 631 static
 632 int _ltt_context_metadata_statedump(struct ltt_session *session,
 633                                     struct lttng_ctx *ctx)
 634 {
 635         int ret = 0;
 636         int i;
 637
 638         if (!ctx)
 639                 return 0;
 640         for (i = 0; i < ctx->nr_fields; i++) {
 641                 const struct lttng_ctx_field *field = &ctx->fields[i];
 642
 643                 ret = _ltt_field_statedump(session, &field->event_field);
 644                 if (ret)
 645                         return ret;
 646         }
 647         return ret;
 648 }
 649
 650 static
 651 int _ltt_fields_metadata_statedump(struct ltt_session *session,
 652                                    struct ltt_event *event)
 653 {
 654         const struct lttng_event_desc *desc = event->desc;
 655         int ret = 0;
 656         int i;
 657
 658         for (i = 0; i < desc->nr_fields; i++) {
 659                 const struct lttng_event_field *field = &desc->fields[i];
 660
 661                 ret = _ltt_field_statedump(session, field);
 662                 if (ret)
 663                         return ret;
 664         }
 665         return ret;
 666 }
 667
 668 static
 669 int _ltt_event_metadata_statedump(struct ltt_session *session,
 670                                   struct ltt_channel *chan,
 671                                   struct ltt_event *event)
 672 {
 673         int ret = 0;
 674
 675         if (event->metadata_dumped || !ACCESS_ONCE(session->active))
 676                 return 0;
 677         if (chan == session->metadata)
 678                 return 0;
 679
 680         ret = lttng_metadata_printf(session,
 681                 "event {\n"
 682                 "       name = %s;\n"
 683                 "       id = %u;\n"
 684                 "       stream_id = %u;\n",
 685                 event->desc->name,
 686                 event->id,
 687                 event->chan->id);
 688         if (ret)
 689                 goto end;
 690
 691         if (event->ctx) {
 692                 ret = lttng_metadata_printf(session,
 693                         "       context := struct {\n");
 694                 if (ret)
 695                         goto end;
 696         }
 697         ret = _ltt_context_metadata_statedump(session, event->ctx);
 698         if (ret)
 699                 goto end;
 700         if (event->ctx) {
 701                 ret = lttng_metadata_printf(session,
 702                         "       };\n");
 703                 if (ret)
 704                         goto end;
 705         }
 706
 707         ret = lttng_metadata_printf(session,
 708                 "       fields := struct {\n"
 709                 );
 710         if (ret)
 711                 goto end;
 712
 713         ret = _ltt_fields_metadata_statedump(session, event);
 714         if (ret)
 715                 goto end;
 716
 717         /*
 718          * LTTng space reservation can only reserve multiples of the
 719          * byte size.
 720          */
 721         ret = lttng_metadata_printf(session,
 722                 "       };\n"
 723                 "};\n\n");
 724         if (ret)
 725                 goto end;
 726
 727         event->metadata_dumped = 1;
 728 end:
 729         return ret;
 730
 731 }
 732
 733 static
 734 int _ltt_channel_metadata_statedump(struct ltt_session *session,
 735                                     struct ltt_channel *chan)
 736 {
 737         int ret = 0;
 738
 739         if (chan->metadata_dumped || !ACCESS_ONCE(session->active))
 740                 return 0;
 741         if (chan == session->metadata)
 742                 return 0;
 743
 744         WARN_ON_ONCE(!chan->header_type);
 745         ret = lttng_metadata_printf(session,
 746                 "stream {\n"
 747                 "       id = %u;\n"
 748                 "       event.header := %s;\n"
 749                 "       packet.context := struct packet_context;\n",
 750                 chan->id,
 751                 chan->header_type == 1 ? "struct event_header_compact" :
 752                         "struct event_header_large");
 753         if (ret)
 754                 goto end;
 755
 756         if (chan->ctx) {
 757                 ret = lttng_metadata_printf(session,
 758                         "       event.context := struct {\n");
 759                 if (ret)
 760                         goto end;
 761         }
 762         ret = _ltt_context_metadata_statedump(session, chan->ctx);
 763         if (ret)
 764                 goto end;
 765         if (chan->ctx) {
 766                 ret = lttng_metadata_printf(session,
 767                         "       };\n");
 768                 if (ret)
 769                         goto end;
 770         }
 771
 772         ret = lttng_metadata_printf(session,
 773                 "};\n\n");
 774
 775         chan->metadata_dumped = 1;
 776 end:
 777         return ret;
 778 }
 779
 780 static
 781 int _ltt_stream_packet_context_declare(struct ltt_session *session)
 782 {
 783         return lttng_metadata_printf(session,
 784                 "struct packet_context {\n"
 785                 "       uint64_t timestamp_begin;\n"
 786                 "       uint64_t timestamp_end;\n"
 787                 "       uint32_t events_discarded;\n"
 788                 "       uint32_t content_size;\n"
 789                 "       uint32_t packet_size;\n"
 790                 "       uint32_t cpu_id;\n"
 791                 "};\n\n"
 792                 );
 793 }
 794
 795 /*
 796  * Compact header:
 797  * id: range: 0 - 30.
 798  * id 31 is reserved to indicate an extended header.
 799  *
 800  * Large header:
 801  * id: range: 0 - 65534.
 802  * id 65535 is reserved to indicate an extended header.
 803  */
 804 static
 805 int _ltt_event_header_declare(struct ltt_session *session)
 806 {
 807         return lttng_metadata_printf(session,
 808         "struct event_header_compact {\n"
 809         "       enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
 810         "       variant <id> {\n"
 811         "               struct {\n"
 812         "                       uint27_t timestamp;\n"
 813         "               } compact;\n"
 814         "               struct {\n"
 815         "                       uint32_t id;\n"
 816         "                       uint64_t timestamp;\n"
 817         "               } extended;\n"
 818         "       } v;\n"
 819         "} align(%u);\n"
 820         "\n"
 821         "struct event_header_large {\n"
 822         "       enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
 823         "       variant <id> {\n"
 824         "               struct {\n"
 825         "                       uint32_t timestamp;\n"
 826         "               } compact;\n"
 827         "               struct {\n"
 828         "                       uint32_t id;\n"
 829         "                       uint64_t timestamp;\n"
 830         "               } extended;\n"
 831         "       } v;\n"
 832         "} align(%u);\n\n",
 833         ltt_alignof(uint32_t) * CHAR_BIT,
 834         ltt_alignof(uint16_t) * CHAR_BIT
 835         );
 836 }
 837
 838 /*
 839  * Output metadata into this session's metadata buffers.
 840  */
 841 static
 842 int _ltt_session_metadata_statedump(struct ltt_session *session)
 843 {
 844         unsigned char *uuid_c = session->uuid.b;
 845         unsigned char uuid_s[37];
 846         struct ltt_channel *chan;
 847         struct ltt_event *event;
 848         int ret = 0;
 849
 850         if (!ACCESS_ONCE(session->active))
 851                 return 0;
 852         if (session->metadata_dumped)
 853                 goto skip_session;
 854         if (!session->metadata) {
 855                 printk(KERN_WARNING "LTTng: attempt to start tracing, but metadata channel is not found. Operation abort.\n");
 856                 return -EPERM;
 857         }
 858
 859         snprintf(uuid_s, sizeof(uuid_s),
 860                 "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
 861                 uuid_c[0], uuid_c[1], uuid_c[2], uuid_c[3],
 862                 uuid_c[4], uuid_c[5], uuid_c[6], uuid_c[7],
 863                 uuid_c[8], uuid_c[9], uuid_c[10], uuid_c[11],
 864                 uuid_c[12], uuid_c[13], uuid_c[14], uuid_c[15]);
 865
 866         ret = lttng_metadata_printf(session,
 867                 "typealias integer { size = 8; align = %u; signed = false; } := uint8_t;\n"
 868                 "typealias integer { size = 16; align = %u; signed = false; } := uint16_t;\n"
 869                 "typealias integer { size = 32; align = %u; signed = false; } := uint32_t;\n"
 870                 "typealias integer { size = 64; align = %u; signed = false; } := uint64_t;\n"
 871                 "typealias integer { size = 5; align = 1; signed = false; } := uint5_t;\n"
 872                 "typealias integer { size = 27; align = 1; signed = false; } := uint27_t;\n"
 873                 "\n"
 874                 "trace {\n"
 875                 "       major = %u;\n"
 876                 "       minor = %u;\n"
 877                 "       uuid = \"%s\";\n"
 878                 "       byte_order = %s;\n"
 879                 "       packet.header := struct {\n"
 880                 "               uint32_t magic;\n"
 881                 "               uint8_t  uuid[16];\n"
 882                 "               uint32_t stream_id;\n"
 883                 "       };\n"
 884                 "};\n\n",
 885                 ltt_alignof(uint8_t) * CHAR_BIT,
 886                 ltt_alignof(uint16_t) * CHAR_BIT,
 887                 ltt_alignof(uint32_t) * CHAR_BIT,
 888                 ltt_alignof(uint64_t) * CHAR_BIT,
 889                 CTF_VERSION_MAJOR,
 890                 CTF_VERSION_MINOR,
 891                 uuid_s,
 892 #ifdef __BIG_ENDIAN
 893                 "be"
 894 #else
 895                 "le"
 896 #endif
 897                 );
 898         if (ret)
 899                 goto end;
 900
 901         ret = _ltt_stream_packet_context_declare(session);
 902         if (ret)
 903                 goto end;
 904
 905         ret = _ltt_event_header_declare(session);
 906         if (ret)
 907                 goto end;
 908
 909 skip_session:
 910         list_for_each_entry(chan, &session->chan, list) {
 911                 ret = _ltt_channel_metadata_statedump(session, chan);
 912                 if (ret)
 913                         goto end;
 914         }
 915
 916         list_for_each_entry(event, &session->events, list) {
 917                 ret = _ltt_event_metadata_statedump(session, event->chan, event);
 918                 if (ret)
 919                         goto end;
 920         }
 921         session->metadata_dumped = 1;
 922 end:
 923         return ret;
 924 }
 925
 926 /**
 927  * ltt_transport_register - LTT transport registration
 928  * @transport: transport structure
 929  *
 930  * Registers a transport which can be used as output to extract the data out of
 931  * LTTng. The module calling this registration function must ensure that no
 932  * trap-inducing code will be executed by the transport functions. E.g.
 933  * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
 934  * is made visible to the transport function. This registration acts as a
 935  * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
 936  * after its registration must it synchronize the TLBs.
 937  */
 938 void ltt_transport_register(struct ltt_transport *transport)
 939 {
 940         /*
 941          * Make sure no page fault can be triggered by the module about to be
 942          * registered. We deal with this here so we don't have to call
 943          * vmalloc_sync_all() in each module's init.
 944          */
 945         wrapper_vmalloc_sync_all();
 946
 947         mutex_lock(&sessions_mutex);
 948         list_add_tail(&transport->node, &ltt_transport_list);
 949         mutex_unlock(&sessions_mutex);
 950 }
 951 EXPORT_SYMBOL_GPL(ltt_transport_register);
 952
 953 /**
 954  * ltt_transport_unregister - LTT transport unregistration
 955  * @transport: transport structure
 956  */
 957 void ltt_transport_unregister(struct ltt_transport *transport)
 958 {
 959         mutex_lock(&sessions_mutex);
 960         list_del(&transport->node);
 961         mutex_unlock(&sessions_mutex);
 962 }
 963 EXPORT_SYMBOL_GPL(ltt_transport_unregister);
 964
 965 static int __init ltt_events_init(void)
 966 {
 967         int ret;
 968
 969         event_cache = KMEM_CACHE(ltt_event, 0);
 970         if (!event_cache)
 971                 return -ENOMEM;
 972         ret = ltt_debugfs_abi_init();
 973         if (ret)
 974                 goto error_abi;
 975         return 0;
 976 error_abi:
 977         kmem_cache_destroy(event_cache);
 978         return ret;
 979 }
 980
 981 module_init(ltt_events_init);
 982
 983 static void __exit ltt_events_exit(void)
 984 {
 985         struct ltt_session *session, *tmpsession;
 986
 987         ltt_debugfs_abi_exit();
 988         list_for_each_entry_safe(session, tmpsession, &sessions, list)
 989                 ltt_session_destroy(session);
 990         kmem_cache_destroy(event_cache);
 991 }
 992
 993 module_exit(ltt_events_exit);
 994
 995 MODULE_LICENSE("GPL and additional rights");
 996 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 997 MODULE_DESCRIPTION("LTTng Events");