lttng-events.c

   1 /*
   2  * lttng-events.c
   3  *
   4  * Holds LTTng per-session event registry.
   5  *
   6  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/list.h>
  25 #include <linux/mutex.h>
  26 #include <linux/sched.h>
  27 #include <linux/slab.h>
  28 #include <linux/jiffies.h>
  29 #include <linux/utsname.h>
  30 #include "wrapper/uuid.h"
  31 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  32 #include "wrapper/random.h"
  33 #include "wrapper/tracepoint.h"
  34 #include "lttng-events.h"
  35 #include "lttng-tracer.h"
  36
  37 static LIST_HEAD(sessions);
  38 static LIST_HEAD(lttng_transport_list);
  39 static DEFINE_MUTEX(sessions_mutex);
  40 static struct kmem_cache *event_cache;
  41
  42 static void _lttng_event_destroy(struct lttng_event *event);
  43 static void _lttng_channel_destroy(struct lttng_channel *chan);
  44 static int _lttng_event_unregister(struct lttng_event *event);
  45 static
  46 int _lttng_event_metadata_statedump(struct lttng_session *session,
  47                                   struct lttng_channel *chan,
  48                                   struct lttng_event *event);
  49 static
  50 int _lttng_session_metadata_statedump(struct lttng_session *session);
  51
  52 void synchronize_trace(void)
  53 {
  54         synchronize_sched();
  55 #ifdef CONFIG_PREEMPT_RT
  56         synchronize_rcu();
  57 #endif
  58 }
  59
  60 struct lttng_session *lttng_session_create(void)
  61 {
  62         struct lttng_session *session;
  63
  64         mutex_lock(&sessions_mutex);
  65         session = kzalloc(sizeof(struct lttng_session), GFP_KERNEL);
  66         if (!session)
  67                 return NULL;
  68         INIT_LIST_HEAD(&session->chan);
  69         INIT_LIST_HEAD(&session->events);
  70         uuid_le_gen(&session->uuid);
  71         list_add(&session->list, &sessions);
  72         mutex_unlock(&sessions_mutex);
  73         return session;
  74 }
  75
  76 void lttng_session_destroy(struct lttng_session *session)
  77 {
  78         struct lttng_channel *chan, *tmpchan;
  79         struct lttng_event *event, *tmpevent;
  80         int ret;
  81
  82         mutex_lock(&sessions_mutex);
  83         ACCESS_ONCE(session->active) = 0;
  84         list_for_each_entry(chan, &session->chan, list) {
  85                 ret = lttng_syscalls_unregister(chan);
  86                 WARN_ON(ret);
  87         }
  88         list_for_each_entry(event, &session->events, list) {
  89                 ret = _lttng_event_unregister(event);
  90                 WARN_ON(ret);
  91         }
  92         synchronize_trace();    /* Wait for in-flight events to complete */
  93         list_for_each_entry_safe(event, tmpevent, &session->events, list)
  94                 _lttng_event_destroy(event);
  95         list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
  96                 _lttng_channel_destroy(chan);
  97         list_del(&session->list);
  98         mutex_unlock(&sessions_mutex);
  99         kfree(session);
 100 }
 101
 102 int lttng_session_enable(struct lttng_session *session)
 103 {
 104         int ret = 0;
 105         struct lttng_channel *chan;
 106
 107         mutex_lock(&sessions_mutex);
 108         if (session->active) {
 109                 ret = -EBUSY;
 110                 goto end;
 111         }
 112
 113         /*
 114          * Snapshot the number of events per channel to know the type of header
 115          * we need to use.
 116          */
 117         list_for_each_entry(chan, &session->chan, list) {
 118                 if (chan->header_type)
 119                         continue;               /* don't change it if session stop/restart */
 120                 if (chan->free_event_id < 31)
 121                         chan->header_type = 1;  /* compact */
 122                 else
 123                         chan->header_type = 2;  /* large */
 124         }
 125
 126         ACCESS_ONCE(session->active) = 1;
 127         ACCESS_ONCE(session->been_active) = 1;
 128         ret = _lttng_session_metadata_statedump(session);
 129         if (ret) {
 130                 ACCESS_ONCE(session->active) = 0;
 131                 goto end;
 132         }
 133         ret = lttng_statedump_start(session);
 134         if (ret)
 135                 ACCESS_ONCE(session->active) = 0;
 136 end:
 137         mutex_unlock(&sessions_mutex);
 138         return ret;
 139 }
 140
 141 int lttng_session_disable(struct lttng_session *session)
 142 {
 143         int ret = 0;
 144
 145         mutex_lock(&sessions_mutex);
 146         if (!session->active) {
 147                 ret = -EBUSY;
 148                 goto end;
 149         }
 150         ACCESS_ONCE(session->active) = 0;
 151 end:
 152         mutex_unlock(&sessions_mutex);
 153         return ret;
 154 }
 155
 156 int lttng_channel_enable(struct lttng_channel *channel)
 157 {
 158         int old;
 159
 160         if (channel == channel->session->metadata)
 161                 return -EPERM;
 162         old = xchg(&channel->enabled, 1);
 163         if (old)
 164                 return -EEXIST;
 165         return 0;
 166 }
 167
 168 int lttng_channel_disable(struct lttng_channel *channel)
 169 {
 170         int old;
 171
 172         if (channel == channel->session->metadata)
 173                 return -EPERM;
 174         old = xchg(&channel->enabled, 0);
 175         if (!old)
 176                 return -EEXIST;
 177         return 0;
 178 }
 179
 180 int lttng_event_enable(struct lttng_event *event)
 181 {
 182         int old;
 183
 184         if (event->chan == event->chan->session->metadata)
 185                 return -EPERM;
 186         old = xchg(&event->enabled, 1);
 187         if (old)
 188                 return -EEXIST;
 189         return 0;
 190 }
 191
 192 int lttng_event_disable(struct lttng_event *event)
 193 {
 194         int old;
 195
 196         if (event->chan == event->chan->session->metadata)
 197                 return -EPERM;
 198         old = xchg(&event->enabled, 0);
 199         if (!old)
 200                 return -EEXIST;
 201         return 0;
 202 }
 203
 204 static struct lttng_transport *lttng_transport_find(const char *name)
 205 {
 206         struct lttng_transport *transport;
 207
 208         list_for_each_entry(transport, &lttng_transport_list, node) {
 209                 if (!strcmp(transport->name, name))
 210                         return transport;
 211         }
 212         return NULL;
 213 }
 214
 215 struct lttng_channel *lttng_channel_create(struct lttng_session *session,
 216                                        const char *transport_name,
 217                                        void *buf_addr,
 218                                        size_t subbuf_size, size_t num_subbuf,
 219                                        unsigned int switch_timer_interval,
 220                                        unsigned int read_timer_interval)
 221 {
 222         struct lttng_channel *chan;
 223         struct lttng_transport *transport = NULL;
 224
 225         mutex_lock(&sessions_mutex);
 226         if (session->been_active)
 227                 goto active;    /* Refuse to add channel to active session */
 228         transport = lttng_transport_find(transport_name);
 229         if (!transport) {
 230                 printk(KERN_WARNING "LTTng transport %s not found\n",
 231                        transport_name);
 232                 goto notransport;
 233         }
 234         if (!try_module_get(transport->owner)) {
 235                 printk(KERN_WARNING "LTT : Can't lock transport module.\n");
 236                 goto notransport;
 237         }
 238         chan = kzalloc(sizeof(struct lttng_channel), GFP_KERNEL);
 239         if (!chan)
 240                 goto nomem;
 241         chan->session = session;
 242         chan->id = session->free_chan_id++;
 243         /*
 244          * Note: the channel creation op already writes into the packet
 245          * headers. Therefore the "chan" information used as input
 246          * should be already accessible.
 247          */
 248         chan->chan = transport->ops.channel_create(transport_name,
 249                         chan, buf_addr, subbuf_size, num_subbuf,
 250                         switch_timer_interval, read_timer_interval);
 251         if (!chan->chan)
 252                 goto create_error;
 253         chan->enabled = 1;
 254         chan->ops = &transport->ops;
 255         chan->transport = transport;
 256         list_add(&chan->list, &session->chan);
 257         mutex_unlock(&sessions_mutex);
 258         return chan;
 259
 260 create_error:
 261         kfree(chan);
 262 nomem:
 263         if (transport)
 264                 module_put(transport->owner);
 265 notransport:
 266 active:
 267         mutex_unlock(&sessions_mutex);
 268         return NULL;
 269 }
 270
 271 /*
 272  * Only used internally at session destruction.
 273  */
 274 static
 275 void _lttng_channel_destroy(struct lttng_channel *chan)
 276 {
 277         chan->ops->channel_destroy(chan->chan);
 278         module_put(chan->transport->owner);
 279         list_del(&chan->list);
 280         lttng_destroy_context(chan->ctx);
 281         kfree(chan);
 282 }
 283
 284 /*
 285  * Supports event creation while tracing session is active.
 286  */
 287 struct lttng_event *lttng_event_create(struct lttng_channel *chan,
 288                                    struct lttng_kernel_event *event_param,
 289                                    void *filter,
 290                                    const struct lttng_event_desc *internal_desc)
 291 {
 292         struct lttng_event *event;
 293         int ret;
 294
 295         mutex_lock(&sessions_mutex);
 296         if (chan->free_event_id == -1U)
 297                 goto full;
 298         /*
 299          * This is O(n^2) (for each event, the loop is called at event
 300          * creation). Might require a hash if we have lots of events.
 301          */
 302         list_for_each_entry(event, &chan->session->events, list)
 303                 if (!strcmp(event->desc->name, event_param->name))
 304                         goto exist;
 305         event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
 306         if (!event)
 307                 goto cache_error;
 308         event->chan = chan;
 309         event->filter = filter;
 310         event->id = chan->free_event_id++;
 311         event->enabled = 1;
 312         event->instrumentation = event_param->instrumentation;
 313         /* Populate lttng_event structure before tracepoint registration. */
 314         smp_wmb();
 315         switch (event_param->instrumentation) {
 316         case LTTNG_KERNEL_TRACEPOINT:
 317                 event->desc = lttng_event_get(event_param->name);
 318                 if (!event->desc)
 319                         goto register_error;
 320                 ret = kabi_2635_tracepoint_probe_register(event_param->name,
 321                                 event->desc->probe_callback,
 322                                 event);
 323                 if (ret)
 324                         goto register_error;
 325                 break;
 326         case LTTNG_KERNEL_KPROBE:
 327                 ret = lttng_kprobes_register(event_param->name,
 328                                 event_param->u.kprobe.symbol_name,
 329                                 event_param->u.kprobe.offset,
 330                                 event_param->u.kprobe.addr,
 331                                 event);
 332                 if (ret)
 333                         goto register_error;
 334                 ret = try_module_get(event->desc->owner);
 335                 WARN_ON_ONCE(!ret);
 336                 break;
 337         case LTTNG_KERNEL_KRETPROBE:
 338         {
 339                 struct lttng_event *event_return;
 340
 341                 /* kretprobe defines 2 events */
 342                 event_return =
 343                         kmem_cache_zalloc(event_cache, GFP_KERNEL);
 344                 if (!event_return)
 345                         goto register_error;
 346                 event_return->chan = chan;
 347                 event_return->filter = filter;
 348                 event_return->id = chan->free_event_id++;
 349                 event_return->enabled = 1;
 350                 event_return->instrumentation = event_param->instrumentation;
 351                 /*
 352                  * Populate lttng_event structure before kretprobe registration.
 353                  */
 354                 smp_wmb();
 355                 ret = lttng_kretprobes_register(event_param->name,
 356                                 event_param->u.kretprobe.symbol_name,
 357                                 event_param->u.kretprobe.offset,
 358                                 event_param->u.kretprobe.addr,
 359                                 event, event_return);
 360                 if (ret) {
 361                         kmem_cache_free(event_cache, event_return);
 362                         goto register_error;
 363                 }
 364                 /* Take 2 refs on the module: one per event. */
 365                 ret = try_module_get(event->desc->owner);
 366                 WARN_ON_ONCE(!ret);
 367                 ret = try_module_get(event->desc->owner);
 368                 WARN_ON_ONCE(!ret);
 369                 ret = _lttng_event_metadata_statedump(chan->session, chan,
 370                                                     event_return);
 371                 if (ret) {
 372                         kmem_cache_free(event_cache, event_return);
 373                         module_put(event->desc->owner);
 374                         module_put(event->desc->owner);
 375                         goto statedump_error;
 376                 }
 377                 list_add(&event_return->list, &chan->session->events);
 378                 break;
 379         }
 380         case LTTNG_KERNEL_FUNCTION:
 381                 ret = lttng_ftrace_register(event_param->name,
 382                                 event_param->u.ftrace.symbol_name,
 383                                 event);
 384                 if (ret)
 385                         goto register_error;
 386                 ret = try_module_get(event->desc->owner);
 387                 WARN_ON_ONCE(!ret);
 388                 break;
 389         case LTTNG_KERNEL_NOOP:
 390                 event->desc = internal_desc;
 391                 if (!event->desc)
 392                         goto register_error;
 393                 break;
 394         default:
 395                 WARN_ON_ONCE(1);
 396         }
 397         ret = _lttng_event_metadata_statedump(chan->session, chan, event);
 398         if (ret)
 399                 goto statedump_error;
 400         list_add(&event->list, &chan->session->events);
 401         mutex_unlock(&sessions_mutex);
 402         return event;
 403
 404 statedump_error:
 405         /* If a statedump error occurs, events will not be readable. */
 406 register_error:
 407         kmem_cache_free(event_cache, event);
 408 cache_error:
 409 exist:
 410 full:
 411         mutex_unlock(&sessions_mutex);
 412         return NULL;
 413 }
 414
 415 /*
 416  * Only used internally at session destruction.
 417  */
 418 int _lttng_event_unregister(struct lttng_event *event)
 419 {
 420         int ret = -EINVAL;
 421
 422         switch (event->instrumentation) {
 423         case LTTNG_KERNEL_TRACEPOINT:
 424                 ret = kabi_2635_tracepoint_probe_unregister(event->desc->name,
 425                                                   event->desc->probe_callback,
 426                                                   event);
 427                 if (ret)
 428                         return ret;
 429                 break;
 430         case LTTNG_KERNEL_KPROBE:
 431                 lttng_kprobes_unregister(event);
 432                 ret = 0;
 433                 break;
 434         case LTTNG_KERNEL_KRETPROBE:
 435                 lttng_kretprobes_unregister(event);
 436                 ret = 0;
 437                 break;
 438         case LTTNG_KERNEL_FUNCTION:
 439                 lttng_ftrace_unregister(event);
 440                 ret = 0;
 441                 break;
 442         case LTTNG_KERNEL_NOOP:
 443                 ret = 0;
 444                 break;
 445         default:
 446                 WARN_ON_ONCE(1);
 447         }
 448         return ret;
 449 }
 450
 451 /*
 452  * Only used internally at session destruction.
 453  */
 454 static
 455 void _lttng_event_destroy(struct lttng_event *event)
 456 {
 457         switch (event->instrumentation) {
 458         case LTTNG_KERNEL_TRACEPOINT:
 459                 lttng_event_put(event->desc);
 460                 break;
 461         case LTTNG_KERNEL_KPROBE:
 462                 module_put(event->desc->owner);
 463                 lttng_kprobes_destroy_private(event);
 464                 break;
 465         case LTTNG_KERNEL_KRETPROBE:
 466                 module_put(event->desc->owner);
 467                 lttng_kretprobes_destroy_private(event);
 468                 break;
 469         case LTTNG_KERNEL_FUNCTION:
 470                 module_put(event->desc->owner);
 471                 lttng_ftrace_destroy_private(event);
 472                 break;
 473         case LTTNG_KERNEL_NOOP:
 474                 break;
 475         default:
 476                 WARN_ON_ONCE(1);
 477         }
 478         list_del(&event->list);
 479         lttng_destroy_context(event->ctx);
 480         kmem_cache_free(event_cache, event);
 481 }
 482
 483 /*
 484  * We have exclusive access to our metadata buffer (protected by the
 485  * sessions_mutex), so we can do racy operations such as looking for
 486  * remaining space left in packet and write, since mutual exclusion
 487  * protects us from concurrent writes.
 488  */
 489 int lttng_metadata_printf(struct lttng_session *session,
 490                           const char *fmt, ...)
 491 {
 492         struct lib_ring_buffer_ctx ctx;
 493         struct lttng_channel *chan = session->metadata;
 494         char *str;
 495         int ret = 0, waitret;
 496         size_t len, reserve_len, pos;
 497         va_list ap;
 498
 499         WARN_ON_ONCE(!ACCESS_ONCE(session->active));
 500
 501         va_start(ap, fmt);
 502         str = kvasprintf(GFP_KERNEL, fmt, ap);
 503         va_end(ap);
 504         if (!str)
 505                 return -ENOMEM;
 506
 507         len = strlen(str);
 508         pos = 0;
 509
 510         for (pos = 0; pos < len; pos += reserve_len) {
 511                 reserve_len = min_t(size_t,
 512                                 chan->ops->packet_avail_size(chan->chan),
 513                                 len - pos);
 514                 lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL, reserve_len,
 515                                          sizeof(char), -1);
 516                 /*
 517                  * We don't care about metadata buffer's records lost
 518                  * count, because we always retry here. Report error if
 519                  * we need to bail out after timeout or being
 520                  * interrupted.
 521                  */
 522                 waitret = wait_event_interruptible_timeout(*chan->ops->get_writer_buf_wait_queue(chan->chan, -1),
 523                         ({
 524                                 ret = chan->ops->event_reserve(&ctx, 0);
 525                                 ret != -ENOBUFS || !ret;
 526                         }),
 527                         msecs_to_jiffies(LTTNG_METADATA_TIMEOUT_MSEC));
 528                 if (!waitret || waitret == -ERESTARTSYS || ret) {
 529                         printk(KERN_WARNING "LTTng: Failure to write metadata to buffers (%s)\n",
 530                                 waitret == -ERESTARTSYS ? "interrupted" :
 531                                         (ret == -ENOBUFS ? "timeout" : "I/O error"));
 532                         if (waitret == -ERESTARTSYS)
 533                                 ret = waitret;
 534                         goto end;
 535                 }
 536                 chan->ops->event_write(&ctx, &str[pos], reserve_len);
 537                 chan->ops->event_commit(&ctx);
 538         }
 539 end:
 540         kfree(str);
 541         return ret;
 542 }
 543
 544 static
 545 int _lttng_field_statedump(struct lttng_session *session,
 546                          const struct lttng_event_field *field)
 547 {
 548         int ret = 0;
 549
 550         switch (field->type.atype) {
 551         case atype_integer:
 552                 ret = lttng_metadata_printf(session,
 553                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s;\n",
 554                         field->type.u.basic.integer.size,
 555                         field->type.u.basic.integer.alignment,
 556                         field->type.u.basic.integer.signedness,
 557                         (field->type.u.basic.integer.encoding == lttng_encode_none)
 558                                 ? "none"
 559                                 : (field->type.u.basic.integer.encoding == lttng_encode_UTF8)
 560                                         ? "UTF8"
 561                                         : "ASCII",
 562                         field->type.u.basic.integer.base,
 563 #ifdef __BIG_ENDIAN
 564                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 565 #else
 566                         field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 567 #endif
 568                         field->name);
 569                 break;
 570         case atype_enum:
 571                 ret = lttng_metadata_printf(session,
 572                         "               %s _%s;\n",
 573                         field->type.u.basic.enumeration.name,
 574                         field->name);
 575                 break;
 576         case atype_array:
 577         {
 578                 const struct lttng_basic_type *elem_type;
 579
 580                 elem_type = &field->type.u.array.elem_type;
 581                 ret = lttng_metadata_printf(session,
 582                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[%u];\n",
 583                         elem_type->u.basic.integer.size,
 584                         elem_type->u.basic.integer.alignment,
 585                         elem_type->u.basic.integer.signedness,
 586                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 587                                 ? "none"
 588                                 : (elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 589                                         ? "UTF8"
 590                                         : "ASCII",
 591                         elem_type->u.basic.integer.base,
 592 #ifdef __BIG_ENDIAN
 593                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 594 #else
 595                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 596 #endif
 597                         field->name, field->type.u.array.length);
 598                 break;
 599         }
 600         case atype_sequence:
 601         {
 602                 const struct lttng_basic_type *elem_type;
 603                 const struct lttng_basic_type *length_type;
 604
 605                 elem_type = &field->type.u.sequence.elem_type;
 606                 length_type = &field->type.u.sequence.length_type;
 607                 ret = lttng_metadata_printf(session,
 608                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
 609                         length_type->u.basic.integer.size,
 610                         (unsigned int) length_type->u.basic.integer.alignment,
 611                         length_type->u.basic.integer.signedness,
 612                         (length_type->u.basic.integer.encoding == lttng_encode_none)
 613                                 ? "none"
 614                                 : ((length_type->u.basic.integer.encoding == lttng_encode_UTF8)
 615                                         ? "UTF8"
 616                                         : "ASCII"),
 617                         length_type->u.basic.integer.base,
 618 #ifdef __BIG_ENDIAN
 619                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 620 #else
 621                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 622 #endif
 623                         field->name);
 624                 if (ret)
 625                         return ret;
 626
 627                 ret = lttng_metadata_printf(session,
 628                         "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[ __%s_length ];\n",
 629                         elem_type->u.basic.integer.size,
 630                         (unsigned int) elem_type->u.basic.integer.alignment,
 631                         elem_type->u.basic.integer.signedness,
 632                         (elem_type->u.basic.integer.encoding == lttng_encode_none)
 633                                 ? "none"
 634                                 : ((elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
 635                                         ? "UTF8"
 636                                         : "ASCII"),
 637                         elem_type->u.basic.integer.base,
 638 #ifdef __BIG_ENDIAN
 639                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 640 #else
 641                         elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 642 #endif
 643                         field->name,
 644                         field->name);
 645                 break;
 646         }
 647
 648         case atype_string:
 649                 /* Default encoding is UTF8 */
 650                 ret = lttng_metadata_printf(session,
 651                         "               string%s _%s;\n",
 652                         field->type.u.basic.string.encoding == lttng_encode_ASCII ?
 653                                 " { encoding = ASCII; }" : "",
 654                         field->name);
 655                 break;
 656         default:
 657                 WARN_ON_ONCE(1);
 658                 return -EINVAL;
 659         }
 660         return ret;
 661 }
 662
 663 static
 664 int _lttng_context_metadata_statedump(struct lttng_session *session,
 665                                     struct lttng_ctx *ctx)
 666 {
 667         int ret = 0;
 668         int i;
 669
 670         if (!ctx)
 671                 return 0;
 672         for (i = 0; i < ctx->nr_fields; i++) {
 673                 const struct lttng_ctx_field *field = &ctx->fields[i];
 674
 675                 ret = _lttng_field_statedump(session, &field->event_field);
 676                 if (ret)
 677                         return ret;
 678         }
 679         return ret;
 680 }
 681
 682 static
 683 int _lttng_fields_metadata_statedump(struct lttng_session *session,
 684                                    struct lttng_event *event)
 685 {
 686         const struct lttng_event_desc *desc = event->desc;
 687         int ret = 0;
 688         int i;
 689
 690         for (i = 0; i < desc->nr_fields; i++) {
 691                 const struct lttng_event_field *field = &desc->fields[i];
 692
 693                 ret = _lttng_field_statedump(session, field);
 694                 if (ret)
 695                         return ret;
 696         }
 697         return ret;
 698 }
 699
 700 static
 701 int _lttng_event_metadata_statedump(struct lttng_session *session,
 702                                   struct lttng_channel *chan,
 703                                   struct lttng_event *event)
 704 {
 705         int ret = 0;
 706
 707         if (event->metadata_dumped || !ACCESS_ONCE(session->active))
 708                 return 0;
 709         if (chan == session->metadata)
 710                 return 0;
 711
 712         ret = lttng_metadata_printf(session,
 713                 "event {\n"
 714                 "       name = %s;\n"
 715                 "       id = %u;\n"
 716                 "       stream_id = %u;\n",
 717                 event->desc->name,
 718                 event->id,
 719                 event->chan->id);
 720         if (ret)
 721                 goto end;
 722
 723         if (event->ctx) {
 724                 ret = lttng_metadata_printf(session,
 725                         "       context := struct {\n");
 726                 if (ret)
 727                         goto end;
 728         }
 729         ret = _lttng_context_metadata_statedump(session, event->ctx);
 730         if (ret)
 731                 goto end;
 732         if (event->ctx) {
 733                 ret = lttng_metadata_printf(session,
 734                         "       };\n");
 735                 if (ret)
 736                         goto end;
 737         }
 738
 739         ret = lttng_metadata_printf(session,
 740                 "       fields := struct {\n"
 741                 );
 742         if (ret)
 743                 goto end;
 744
 745         ret = _lttng_fields_metadata_statedump(session, event);
 746         if (ret)
 747                 goto end;
 748
 749         /*
 750          * LTTng space reservation can only reserve multiples of the
 751          * byte size.
 752          */
 753         ret = lttng_metadata_printf(session,
 754                 "       };\n"
 755                 "};\n\n");
 756         if (ret)
 757                 goto end;
 758
 759         event->metadata_dumped = 1;
 760 end:
 761         return ret;
 762
 763 }
 764
 765 static
 766 int _lttng_channel_metadata_statedump(struct lttng_session *session,
 767                                     struct lttng_channel *chan)
 768 {
 769         int ret = 0;
 770
 771         if (chan->metadata_dumped || !ACCESS_ONCE(session->active))
 772                 return 0;
 773         if (chan == session->metadata)
 774                 return 0;
 775
 776         WARN_ON_ONCE(!chan->header_type);
 777         ret = lttng_metadata_printf(session,
 778                 "stream {\n"
 779                 "       id = %u;\n"
 780                 "       event.header := %s;\n"
 781                 "       packet.context := struct packet_context;\n",
 782                 chan->id,
 783                 chan->header_type == 1 ? "struct event_header_compact" :
 784                         "struct event_header_large");
 785         if (ret)
 786                 goto end;
 787
 788         if (chan->ctx) {
 789                 ret = lttng_metadata_printf(session,
 790                         "       event.context := struct {\n");
 791                 if (ret)
 792                         goto end;
 793         }
 794         ret = _lttng_context_metadata_statedump(session, chan->ctx);
 795         if (ret)
 796                 goto end;
 797         if (chan->ctx) {
 798                 ret = lttng_metadata_printf(session,
 799                         "       };\n");
 800                 if (ret)
 801                         goto end;
 802         }
 803
 804         ret = lttng_metadata_printf(session,
 805                 "};\n\n");
 806
 807         chan->metadata_dumped = 1;
 808 end:
 809         return ret;
 810 }
 811
 812 static
 813 int _lttng_stream_packet_context_declare(struct lttng_session *session)
 814 {
 815         return lttng_metadata_printf(session,
 816                 "struct packet_context {\n"
 817                 "       uint64_clock_monotonic_t timestamp_begin;\n"
 818                 "       uint64_clock_monotonic_t timestamp_end;\n"
 819                 "       unsigned long events_discarded;\n"
 820                 "       uint32_t content_size;\n"
 821                 "       uint32_t packet_size;\n"
 822                 "       uint32_t cpu_id;\n"
 823                 "};\n\n"
 824                 );
 825 }
 826
 827 /*
 828  * Compact header:
 829  * id: range: 0 - 30.
 830  * id 31 is reserved to indicate an extended header.
 831  *
 832  * Large header:
 833  * id: range: 0 - 65534.
 834  * id 65535 is reserved to indicate an extended header.
 835  */
 836 static
 837 int _lttng_event_header_declare(struct lttng_session *session)
 838 {
 839         return lttng_metadata_printf(session,
 840         "struct event_header_compact {\n"
 841         "       enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
 842         "       variant <id> {\n"
 843         "               struct {\n"
 844         "                       uint27_clock_monotonic_t timestamp;\n"
 845         "               } compact;\n"
 846         "               struct {\n"
 847         "                       uint32_t id;\n"
 848         "                       uint64_clock_monotonic_t timestamp;\n"
 849         "               } extended;\n"
 850         "       } v;\n"
 851         "} align(%u);\n"
 852         "\n"
 853         "struct event_header_large {\n"
 854         "       enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
 855         "       variant <id> {\n"
 856         "               struct {\n"
 857         "                       uint32_clock_monotonic_t timestamp;\n"
 858         "               } compact;\n"
 859         "               struct {\n"
 860         "                       uint32_t id;\n"
 861         "                       uint64_clock_monotonic_t timestamp;\n"
 862         "               } extended;\n"
 863         "       } v;\n"
 864         "} align(%u);\n\n",
 865         lttng_alignof(uint32_t) * CHAR_BIT,
 866         lttng_alignof(uint16_t) * CHAR_BIT
 867         );
 868 }
 869
 870  /*
 871  * Approximation of NTP time of day to clock monotonic correlation,
 872  * taken at start of trace.
 873  * Yes, this is only an approximation. Yes, we can (and will) do better
 874  * in future versions.
 875  */
 876 static
 877 uint64_t measure_clock_offset(void)
 878 {
 879         uint64_t offset, monotonic[2], realtime;
 880         struct timespec rts = { 0, 0 };
 881         unsigned long flags;
 882
 883         /* Disable interrupts to increase correlation precision. */
 884         local_irq_save(flags);
 885         monotonic[0] = trace_clock_read64();
 886         getnstimeofday(&rts);
 887         monotonic[1] = trace_clock_read64();
 888         local_irq_restore(flags);
 889
 890         offset = (monotonic[0] + monotonic[1]) >> 1;
 891         realtime = (uint64_t) rts.tv_sec * NSEC_PER_SEC;
 892         realtime += rts.tv_nsec;
 893         offset = realtime - offset;
 894         return offset;
 895 }
 896
 897 /*
 898  * Output metadata into this session's metadata buffers.
 899  */
 900 static
 901 int _lttng_session_metadata_statedump(struct lttng_session *session)
 902 {
 903         unsigned char *uuid_c = session->uuid.b;
 904         unsigned char uuid_s[37], clock_uuid_s[BOOT_ID_LEN];
 905         struct lttng_channel *chan;
 906         struct lttng_event *event;
 907         int ret = 0;
 908
 909         if (!ACCESS_ONCE(session->active))
 910                 return 0;
 911         if (session->metadata_dumped)
 912                 goto skip_session;
 913         if (!session->metadata) {
 914                 printk(KERN_WARNING "LTTng: attempt to start tracing, but metadata channel is not found. Operation abort.\n");
 915                 return -EPERM;
 916         }
 917
 918         snprintf(uuid_s, sizeof(uuid_s),
 919                 "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
 920                 uuid_c[0], uuid_c[1], uuid_c[2], uuid_c[3],
 921                 uuid_c[4], uuid_c[5], uuid_c[6], uuid_c[7],
 922                 uuid_c[8], uuid_c[9], uuid_c[10], uuid_c[11],
 923                 uuid_c[12], uuid_c[13], uuid_c[14], uuid_c[15]);
 924
 925         ret = lttng_metadata_printf(session,
 926                 "typealias integer { size = 8; align = %u; signed = false; } := uint8_t;\n"
 927                 "typealias integer { size = 16; align = %u; signed = false; } := uint16_t;\n"
 928                 "typealias integer { size = 32; align = %u; signed = false; } := uint32_t;\n"
 929                 "typealias integer { size = 64; align = %u; signed = false; } := uint64_t;\n"
 930                 "typealias integer { size = %u; align = %u; signed = false; } := unsigned long;\n"
 931                 "typealias integer { size = 5; align = 1; signed = false; } := uint5_t;\n"
 932                 "typealias integer { size = 27; align = 1; signed = false; } := uint27_t;\n"
 933                 "\n"
 934                 "trace {\n"
 935                 "       major = %u;\n"
 936                 "       minor = %u;\n"
 937                 "       uuid = \"%s\";\n"
 938                 "       byte_order = %s;\n"
 939                 "       packet.header := struct {\n"
 940                 "               uint32_t magic;\n"
 941                 "               uint8_t  uuid[16];\n"
 942                 "               uint32_t stream_id;\n"
 943                 "       };\n"
 944                 "};\n\n",
 945                 lttng_alignof(uint8_t) * CHAR_BIT,
 946                 lttng_alignof(uint16_t) * CHAR_BIT,
 947                 lttng_alignof(uint32_t) * CHAR_BIT,
 948                 lttng_alignof(uint64_t) * CHAR_BIT,
 949                 sizeof(unsigned long) * CHAR_BIT,
 950                 lttng_alignof(unsigned long) * CHAR_BIT,
 951                 CTF_SPEC_MAJOR,
 952                 CTF_SPEC_MINOR,
 953                 uuid_s,
 954 #ifdef __BIG_ENDIAN
 955                 "be"
 956 #else
 957                 "le"
 958 #endif
 959                 );
 960         if (ret)
 961                 goto end;
 962
 963         ret = lttng_metadata_printf(session,
 964                 "env {\n"
 965                 "       hostname = \"%s\";\n"
 966                 "       domain = \"kernel\";\n"
 967                 "       sysname = \"%s\";\n"
 968                 "       kernel_release = \"%s\";\n"
 969                 "       kernel_version = \"%s\";\n"
 970                 "       tracer_name = \"lttng-modules\";\n"
 971                 "       tracer_major = %d;\n"
 972                 "       tracer_minor = %d;\n"
 973                 "       tracer_patchlevel = %d;\n"
 974                 "};\n\n",
 975                 current->nsproxy->uts_ns->name.nodename,
 976                 utsname()->sysname,
 977                 utsname()->release,
 978                 utsname()->version,
 979                 LTTNG_MODULES_MAJOR_VERSION,
 980                 LTTNG_MODULES_MINOR_VERSION,
 981                 LTTNG_MODULES_PATCHLEVEL_VERSION
 982                 );
 983         if (ret)
 984                 goto end;
 985
 986         ret = lttng_metadata_printf(session,
 987                 "clock {\n"
 988                 "       name = %s;\n",
 989                 "monotonic"
 990                 );
 991         if (ret)
 992                 goto end;
 993
 994         if (!trace_clock_uuid(clock_uuid_s)) {
 995                 ret = lttng_metadata_printf(session,
 996                         "       uuid = \"%s\";\n",
 997                         clock_uuid_s
 998                         );
 999                 if (ret)
1000                         goto end;
1001         }
1002
1003         ret = lttng_metadata_printf(session,
1004                 "       description = \"Monotonic Clock\";\n"
1005                 "       freq = %llu; /* Frequency, in Hz */\n"
1006                 "       /* clock value offset from Epoch is: offset * (1/freq) */\n"
1007                 "       offset = %llu;\n"
1008                 "};\n\n",
1009                 (unsigned long long) trace_clock_freq(),
1010                 (unsigned long long) measure_clock_offset()
1011                 );
1012         if (ret)
1013                 goto end;
1014
1015         ret = lttng_metadata_printf(session,
1016                 "typealias integer {\n"
1017                 "       size = 27; align = 1; signed = false;\n"
1018                 "       map = clock.monotonic.value;\n"
1019                 "} := uint27_clock_monotonic_t;\n"
1020                 "\n"
1021                 "typealias integer {\n"
1022                 "       size = 32; align = %u; signed = false;\n"
1023                 "       map = clock.monotonic.value;\n"
1024                 "} := uint32_clock_monotonic_t;\n"
1025                 "\n"
1026                 "typealias integer {\n"
1027                 "       size = 64; align = %u; signed = false;\n"
1028                 "       map = clock.monotonic.value;\n"
1029                 "} := uint64_clock_monotonic_t;\n\n",
1030                 lttng_alignof(uint32_t) * CHAR_BIT,
1031                 lttng_alignof(uint64_t) * CHAR_BIT
1032                 );
1033         if (ret)
1034                 goto end;
1035
1036         ret = _lttng_stream_packet_context_declare(session);
1037         if (ret)
1038                 goto end;
1039
1040         ret = _lttng_event_header_declare(session);
1041         if (ret)
1042                 goto end;
1043
1044 skip_session:
1045         list_for_each_entry(chan, &session->chan, list) {
1046                 ret = _lttng_channel_metadata_statedump(session, chan);
1047                 if (ret)
1048                         goto end;
1049         }
1050
1051         list_for_each_entry(event, &session->events, list) {
1052                 ret = _lttng_event_metadata_statedump(session, event->chan, event);
1053                 if (ret)
1054                         goto end;
1055         }
1056         session->metadata_dumped = 1;
1057 end:
1058         return ret;
1059 }
1060
1061 /**
1062  * lttng_transport_register - LTT transport registration
1063  * @transport: transport structure
1064  *
1065  * Registers a transport which can be used as output to extract the data out of
1066  * LTTng. The module calling this registration function must ensure that no
1067  * trap-inducing code will be executed by the transport functions. E.g.
1068  * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
1069  * is made visible to the transport function. This registration acts as a
1070  * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
1071  * after its registration must it synchronize the TLBs.
1072  */
1073 void lttng_transport_register(struct lttng_transport *transport)
1074 {
1075         /*
1076          * Make sure no page fault can be triggered by the module about to be
1077          * registered. We deal with this here so we don't have to call
1078          * vmalloc_sync_all() in each module's init.
1079          */
1080         wrapper_vmalloc_sync_all();
1081
1082         mutex_lock(&sessions_mutex);
1083         list_add_tail(&transport->node, &lttng_transport_list);
1084         mutex_unlock(&sessions_mutex);
1085 }
1086 EXPORT_SYMBOL_GPL(lttng_transport_register);
1087
1088 /**
1089  * lttng_transport_unregister - LTT transport unregistration
1090  * @transport: transport structure
1091  */
1092 void lttng_transport_unregister(struct lttng_transport *transport)
1093 {
1094         mutex_lock(&sessions_mutex);
1095         list_del(&transport->node);
1096         mutex_unlock(&sessions_mutex);
1097 }
1098 EXPORT_SYMBOL_GPL(lttng_transport_unregister);
1099
1100 static int __init lttng_events_init(void)
1101 {
1102         int ret;
1103
1104         event_cache = KMEM_CACHE(lttng_event, 0);
1105         if (!event_cache)
1106                 return -ENOMEM;
1107         ret = lttng_abi_init();
1108         if (ret)
1109                 goto error_abi;
1110         return 0;
1111 error_abi:
1112         kmem_cache_destroy(event_cache);
1113         return ret;
1114 }
1115
1116 module_init(lttng_events_init);
1117
1118 static void __exit lttng_events_exit(void)
1119 {
1120         struct lttng_session *session, *tmpsession;
1121
1122         lttng_abi_exit();
1123         list_for_each_entry_safe(session, tmpsession, &sessions, list)
1124                 lttng_session_destroy(session);
1125         kmem_cache_destroy(event_cache);
1126 }
1127
1128 module_exit(lttng_events_exit);
1129
1130 MODULE_LICENSE("GPL and additional rights");
1131 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
1132 MODULE_DESCRIPTION("LTTng Events");