src/lttng-ring-buffer-client.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-ring-buffer-client.h
   4  *
   5  * LTTng lib ring buffer client template.
   6  *
   7  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/types.h>
  12 #include <lttng/bitfield.h>
  13 #include <wrapper/vmalloc.h>    /* for wrapper_vmalloc_sync_mappings() */
  14 #include <wrapper/trace-clock.h>
  15 #include <lttng/events.h>
  16 #include <lttng/events-internal.h>
  17 #include <lttng/tracer.h>
  18 #include <ringbuffer/frontend_types.h>
  19
  20 #define LTTNG_COMPACT_EVENT_BITS        5
  21 #define LTTNG_COMPACT_TSC_BITS          27
  22
  23 static struct lttng_transport lttng_relay_transport;
  24
  25 /*
  26  * Keep the natural field alignment for _each field_ within this structure if
  27  * you ever add/remove a field from this header. Packed attribute is not used
  28  * because gcc generates poor code on at least powerpc and mips. Don't ever
  29  * let gcc add padding between the structure elements.
  30  *
  31  * The guarantee we have with timestamps is that all the events in a
  32  * packet are included (inclusive) within the begin/end timestamps of
  33  * the packet. Another guarantee we have is that the "timestamp begin",
  34  * as well as the event timestamps, are monotonically increasing (never
  35  * decrease) when moving forward in a stream (physically). But this
  36  * guarantee does not apply to "timestamp end", because it is sampled at
  37  * commit time, which is not ordered with respect to space reservation.
  38  */
  39
  40 struct packet_header {
  41         /* Trace packet header */
  42         uint32_t magic;                 /*
  43                                          * Trace magic number.
  44                                          * contains endianness information.
  45                                          */
  46         uint8_t uuid[16];
  47         uint32_t stream_id;
  48         uint64_t stream_instance_id;
  49
  50         struct {
  51                 /* Stream packet context */
  52                 uint64_t timestamp_begin;       /* Cycle count at subbuffer start */
  53                 uint64_t timestamp_end;         /* Cycle count at subbuffer end */
  54                 uint64_t content_size;          /* Size of data in subbuffer */
  55                 uint64_t packet_size;           /* Subbuffer size (include padding) */
  56                 uint64_t packet_seq_num;        /* Packet sequence number */
  57                 unsigned long events_discarded; /*
  58                                                  * Events lost in this subbuffer since
  59                                                  * the beginning of the trace.
  60                                                  * (may overflow)
  61                                                  */
  62                 uint32_t cpu_id;                /* CPU id associated with stream */
  63                 uint8_t header_end;             /* End of header */
  64         } ctx;
  65 };
  66
  67 struct lttng_client_ctx {
  68         size_t packet_context_len;
  69         size_t event_context_len;
  70 };
  71
  72 static inline notrace u64 lib_ring_buffer_clock_read(struct lttng_kernel_ring_buffer_channel *chan)
  73 {
  74         return trace_clock_read64();
  75 }
  76
  77 static inline
  78 size_t ctx_get_aligned_size(size_t offset, struct lttng_kernel_ctx *ctx,
  79                 size_t ctx_len)
  80 {
  81         size_t orig_offset = offset;
  82
  83         if (likely(!ctx))
  84                 return 0;
  85         offset += lib_ring_buffer_align(offset, ctx->largest_align);
  86         offset += ctx_len;
  87         return offset - orig_offset;
  88 }
  89
  90 static inline
  91 void ctx_get_struct_size(struct lttng_kernel_ctx *ctx, size_t *ctx_len,
  92                 struct lttng_kernel_channel_buffer *lttng_chan,
  93                 struct lttng_kernel_ring_buffer_ctx *bufctx)
  94 {
  95         int i;
  96         size_t offset = 0;
  97
  98         if (likely(!ctx)) {
  99                 *ctx_len = 0;
 100                 return;
 101         }
 102         for (i = 0; i < ctx->nr_fields; i++) {
 103                 offset += ctx->fields[i].get_size(ctx->fields[i].priv,
 104                                 bufctx->probe_ctx, offset);
 105         }
 106         *ctx_len = offset;
 107 }
 108
 109 static inline
 110 void ctx_record(struct lttng_kernel_ring_buffer_ctx *bufctx,
 111                 struct lttng_kernel_channel_buffer *lttng_chan,
 112                 struct lttng_kernel_ctx *ctx)
 113 {
 114         int i;
 115
 116         if (likely(!ctx))
 117                 return;
 118         lib_ring_buffer_align_ctx(bufctx, ctx->largest_align);
 119         for (i = 0; i < ctx->nr_fields; i++)
 120                 ctx->fields[i].record(ctx->fields[i].priv, bufctx->probe_ctx,
 121                                 bufctx, lttng_chan);
 122 }
 123
 124 /*
 125  * record_header_size - Calculate the header size and padding necessary.
 126  * @config: ring buffer instance configuration
 127  * @chan: channel
 128  * @offset: offset in the write buffer
 129  * @pre_header_padding: padding to add before the header (output)
 130  * @ctx: reservation context
 131  *
 132  * Returns the event header size (including padding).
 133  *
 134  * The payload must itself determine its own alignment from the biggest type it
 135  * contains.
 136  */
 137 static __inline__
 138 size_t record_header_size(const struct lttng_kernel_ring_buffer_config *config,
 139                                  struct lttng_kernel_ring_buffer_channel *chan, size_t offset,
 140                                  size_t *pre_header_padding,
 141                                  struct lttng_kernel_ring_buffer_ctx *ctx,
 142                                  struct lttng_client_ctx *client_ctx)
 143 {
 144         struct lttng_kernel_channel_buffer *lttng_chan = channel_get_private(chan);
 145         size_t orig_offset = offset;
 146         size_t padding;
 147
 148         switch (lttng_chan->priv->header_type) {
 149         case 1: /* compact */
 150                 padding = lib_ring_buffer_align(offset, lttng_alignof(uint32_t));
 151                 offset += padding;
 152                 if (!(ctx->priv.rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 153                         offset += sizeof(uint32_t);     /* id and timestamp */
 154                 } else {
 155                         /* Minimum space taken by LTTNG_COMPACT_EVENT_BITS id */
 156                         offset += (LTTNG_COMPACT_EVENT_BITS + CHAR_BIT - 1) / CHAR_BIT;
 157                         /* Align extended struct on largest member */
 158                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 159                         offset += sizeof(uint32_t);     /* id */
 160                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 161                         offset += sizeof(uint64_t);     /* timestamp */
 162                 }
 163                 break;
 164         case 2: /* large */
 165                 padding = lib_ring_buffer_align(offset, lttng_alignof(uint16_t));
 166                 offset += padding;
 167                 offset += sizeof(uint16_t);
 168                 if (!(ctx->priv.rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 169                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint32_t));
 170                         offset += sizeof(uint32_t);     /* timestamp */
 171                 } else {
 172                         /* Align extended struct on largest member */
 173                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 174                         offset += sizeof(uint32_t);     /* id */
 175                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 176                         offset += sizeof(uint64_t);     /* timestamp */
 177                 }
 178                 break;
 179         default:
 180                 padding = 0;
 181                 WARN_ON_ONCE(1);
 182         }
 183         offset += ctx_get_aligned_size(offset, lttng_chan->priv->ctx,
 184                         client_ctx->packet_context_len);
 185         *pre_header_padding = padding;
 186         return offset - orig_offset;
 187 }
 188
 189 #include <ringbuffer/api.h>
 190
 191 static
 192 void lttng_write_event_header_slow(const struct lttng_kernel_ring_buffer_config *config,
 193                                  struct lttng_kernel_ring_buffer_ctx *ctx,
 194                                  uint32_t event_id);
 195
 196 /*
 197  * lttng_write_event_header
 198  *
 199  * Writes the event header to the offset (already aligned on 32-bits).
 200  *
 201  * @config: ring buffer instance configuration
 202  * @ctx: reservation context
 203  * @event_id: event ID
 204  */
 205 static __inline__
 206 void lttng_write_event_header(const struct lttng_kernel_ring_buffer_config *config,
 207                             struct lttng_kernel_ring_buffer_ctx *ctx,
 208                             uint32_t event_id)
 209 {
 210         struct lttng_kernel_channel_buffer *lttng_chan = channel_get_private(ctx->priv.chan);
 211
 212         if (unlikely(ctx->priv.rflags))
 213                 goto slow_path;
 214
 215         switch (lttng_chan->priv->header_type) {
 216         case 1: /* compact */
 217         {
 218                 uint32_t id_time = 0;
 219
 220                 bt_bitfield_write(&id_time, uint32_t,
 221                                 0,
 222                                 LTTNG_COMPACT_EVENT_BITS,
 223                                 event_id);
 224                 bt_bitfield_write(&id_time, uint32_t,
 225                                 LTTNG_COMPACT_EVENT_BITS,
 226                                 LTTNG_COMPACT_TSC_BITS,
 227                                 ctx->priv.tsc);
 228                 lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
 229                 break;
 230         }
 231         case 2: /* large */
 232         {
 233                 uint32_t timestamp = (uint32_t) ctx->priv.tsc;
 234                 uint16_t id = event_id;
 235
 236                 lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 237                 lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint32_t));
 238                 lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 239                 break;
 240         }
 241         default:
 242                 WARN_ON_ONCE(1);
 243         }
 244
 245         ctx_record(ctx, lttng_chan, lttng_chan->priv->ctx);
 246         lib_ring_buffer_align_ctx(ctx, ctx->largest_align);
 247
 248         return;
 249
 250 slow_path:
 251         lttng_write_event_header_slow(config, ctx, event_id);
 252 }
 253
 254 static
 255 void lttng_write_event_header_slow(const struct lttng_kernel_ring_buffer_config *config,
 256                                  struct lttng_kernel_ring_buffer_ctx *ctx,
 257                                  uint32_t event_id)
 258 {
 259         struct lttng_kernel_channel_buffer *lttng_chan = channel_get_private(ctx->priv.chan);
 260
 261         switch (lttng_chan->priv->header_type) {
 262         case 1: /* compact */
 263                 if (!(ctx->priv.rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 264                         uint32_t id_time = 0;
 265
 266                         bt_bitfield_write(&id_time, uint32_t,
 267                                         0,
 268                                         LTTNG_COMPACT_EVENT_BITS,
 269                                         event_id);
 270                         bt_bitfield_write(&id_time, uint32_t,
 271                                         LTTNG_COMPACT_EVENT_BITS,
 272                                         LTTNG_COMPACT_TSC_BITS, ctx->priv.tsc);
 273                         lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
 274                 } else {
 275                         uint8_t id = 0;
 276                         uint64_t timestamp = ctx->priv.tsc;
 277
 278                         bt_bitfield_write(&id, uint8_t,
 279                                         0,
 280                                         LTTNG_COMPACT_EVENT_BITS,
 281                                         31);
 282                         lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 283                         /* Align extended struct on largest member */
 284                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 285                         lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
 286                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 287                         lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 288                 }
 289                 break;
 290         case 2: /* large */
 291         {
 292                 if (!(ctx->priv.rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 293                         uint32_t timestamp = (uint32_t) ctx->priv.tsc;
 294                         uint16_t id = event_id;
 295
 296                         lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 297                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint32_t));
 298                         lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 299                 } else {
 300                         uint16_t id = 65535;
 301                         uint64_t timestamp = ctx->priv.tsc;
 302
 303                         lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 304                         /* Align extended struct on largest member */
 305                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 306                         lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
 307                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 308                         lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 309                 }
 310                 break;
 311         }
 312         default:
 313                 WARN_ON_ONCE(1);
 314         }
 315         ctx_record(ctx, lttng_chan, lttng_chan->priv->ctx);
 316         lib_ring_buffer_align_ctx(ctx, ctx->largest_align);
 317 }
 318
 319 static const struct lttng_kernel_ring_buffer_config client_config;
 320
 321 static u64 client_ring_buffer_clock_read(struct lttng_kernel_ring_buffer_channel *chan)
 322 {
 323         return lib_ring_buffer_clock_read(chan);
 324 }
 325
 326 static
 327 size_t client_record_header_size(const struct lttng_kernel_ring_buffer_config *config,
 328                                  struct lttng_kernel_ring_buffer_channel *chan, size_t offset,
 329                                  size_t *pre_header_padding,
 330                                  struct lttng_kernel_ring_buffer_ctx *ctx,
 331                                  void *client_ctx)
 332 {
 333         return record_header_size(config, chan, offset,
 334                                   pre_header_padding, ctx, client_ctx);
 335 }
 336
 337 /**
 338  * client_packet_header_size - called on buffer-switch to a new sub-buffer
 339  *
 340  * Return header size without padding after the structure. Don't use packed
 341  * structure because gcc generates inefficient code on some architectures
 342  * (powerpc, mips..)
 343  */
 344 static size_t client_packet_header_size(void)
 345 {
 346         return offsetof(struct packet_header, ctx.header_end);
 347 }
 348
 349 static void client_buffer_begin(struct lttng_kernel_ring_buffer *buf, u64 tsc,
 350                                 unsigned int subbuf_idx)
 351 {
 352         struct lttng_kernel_ring_buffer_channel *chan = buf->backend.chan;
 353         struct packet_header *header =
 354                 (struct packet_header *)
 355                         lib_ring_buffer_offset_address(&buf->backend,
 356                                 subbuf_idx * chan->backend.subbuf_size);
 357         struct lttng_kernel_channel_buffer *lttng_chan = channel_get_private(chan);
 358         struct lttng_kernel_session *session = lttng_chan->parent.session;
 359
 360         header->magic = CTF_MAGIC_NUMBER;
 361         memcpy(header->uuid, session->priv->uuid.b, sizeof(session->priv->uuid));
 362         header->stream_id = lttng_chan->priv->id;
 363         header->stream_instance_id = buf->backend.cpu;
 364         header->ctx.timestamp_begin = tsc;
 365         header->ctx.timestamp_end = 0;
 366         header->ctx.content_size = ~0ULL; /* for debugging */
 367         header->ctx.packet_size = ~0ULL;
 368         header->ctx.packet_seq_num = chan->backend.num_subbuf * \
 369                                      buf->backend.buf_cnt[subbuf_idx].seq_cnt + \
 370                                      subbuf_idx;
 371         header->ctx.events_discarded = 0;
 372         header->ctx.cpu_id = buf->backend.cpu;
 373 }
 374
 375 /*
 376  * offset is assumed to never be 0 here : never deliver a completely empty
 377  * subbuffer. data_size is between 1 and subbuf_size.
 378  */
 379 static void client_buffer_end(struct lttng_kernel_ring_buffer *buf, u64 tsc,
 380                               unsigned int subbuf_idx, unsigned long data_size)
 381 {
 382         struct lttng_kernel_ring_buffer_channel *chan = buf->backend.chan;
 383         struct packet_header *header =
 384                 (struct packet_header *)
 385                         lib_ring_buffer_offset_address(&buf->backend,
 386                                 subbuf_idx * chan->backend.subbuf_size);
 387         unsigned long records_lost = 0;
 388
 389         header->ctx.timestamp_end = tsc;
 390         header->ctx.content_size =
 391                 (uint64_t) data_size * CHAR_BIT;                /* in bits */
 392         header->ctx.packet_size =
 393                 (uint64_t) PAGE_ALIGN(data_size) * CHAR_BIT;    /* in bits */
 394         records_lost += lib_ring_buffer_get_records_lost_full(&client_config, buf);
 395         records_lost += lib_ring_buffer_get_records_lost_wrap(&client_config, buf);
 396         records_lost += lib_ring_buffer_get_records_lost_big(&client_config, buf);
 397         header->ctx.events_discarded = records_lost;
 398 }
 399
 400 static int client_buffer_create(struct lttng_kernel_ring_buffer *buf, void *priv,
 401                                 int cpu, const char *name)
 402 {
 403         return 0;
 404 }
 405
 406 static void client_buffer_finalize(struct lttng_kernel_ring_buffer *buf, void *priv, int cpu)
 407 {
 408 }
 409
 410 static struct packet_header *client_packet_header(
 411                 const struct lttng_kernel_ring_buffer_config *config,
 412                 struct lttng_kernel_ring_buffer *buf)
 413 {
 414         return lib_ring_buffer_read_offset_address(&buf->backend, 0);
 415 }
 416
 417 static int client_timestamp_begin(const struct lttng_kernel_ring_buffer_config *config,
 418                 struct lttng_kernel_ring_buffer *buf,
 419                 uint64_t *timestamp_begin)
 420 {
 421         struct packet_header *header = client_packet_header(config, buf);
 422         *timestamp_begin = header->ctx.timestamp_begin;
 423
 424         return 0;
 425 }
 426
 427 static int client_timestamp_end(const struct lttng_kernel_ring_buffer_config *config,
 428                         struct lttng_kernel_ring_buffer *buf,
 429                         uint64_t *timestamp_end)
 430 {
 431         struct packet_header *header = client_packet_header(config, buf);
 432         *timestamp_end = header->ctx.timestamp_end;
 433
 434         return 0;
 435 }
 436
 437 static int client_events_discarded(const struct lttng_kernel_ring_buffer_config *config,
 438                         struct lttng_kernel_ring_buffer *buf,
 439                         uint64_t *events_discarded)
 440 {
 441         struct packet_header *header = client_packet_header(config, buf);
 442         *events_discarded = header->ctx.events_discarded;
 443
 444         return 0;
 445 }
 446
 447 static int client_content_size(const struct lttng_kernel_ring_buffer_config *config,
 448                         struct lttng_kernel_ring_buffer *buf,
 449                         uint64_t *content_size)
 450 {
 451         struct packet_header *header = client_packet_header(config, buf);
 452         *content_size = header->ctx.content_size;
 453
 454         return 0;
 455 }
 456
 457 static int client_packet_size(const struct lttng_kernel_ring_buffer_config *config,
 458                         struct lttng_kernel_ring_buffer *buf,
 459                         uint64_t *packet_size)
 460 {
 461         struct packet_header *header = client_packet_header(config, buf);
 462         *packet_size = header->ctx.packet_size;
 463
 464         return 0;
 465 }
 466
 467 static int client_stream_id(const struct lttng_kernel_ring_buffer_config *config,
 468                         struct lttng_kernel_ring_buffer *buf,
 469                         uint64_t *stream_id)
 470 {
 471         struct lttng_kernel_ring_buffer_channel *chan = buf->backend.chan;
 472         struct lttng_kernel_channel_buffer *lttng_chan = channel_get_private(chan);
 473
 474         *stream_id = lttng_chan->priv->id;
 475         return 0;
 476 }
 477
 478 static int client_current_timestamp(const struct lttng_kernel_ring_buffer_config *config,
 479                 struct lttng_kernel_ring_buffer *bufb,
 480                 uint64_t *ts)
 481 {
 482         *ts = config->cb.ring_buffer_clock_read(bufb->backend.chan);
 483
 484         return 0;
 485 }
 486
 487 static int client_sequence_number(const struct lttng_kernel_ring_buffer_config *config,
 488                         struct lttng_kernel_ring_buffer *buf,
 489                         uint64_t *seq)
 490 {
 491         struct packet_header *header = client_packet_header(config, buf);
 492
 493         *seq = header->ctx.packet_seq_num;
 494
 495         return 0;
 496 }
 497
 498 static
 499 int client_instance_id(const struct lttng_kernel_ring_buffer_config *config,
 500                 struct lttng_kernel_ring_buffer *buf,
 501                 uint64_t *id)
 502 {
 503         *id = buf->backend.cpu;
 504
 505         return 0;
 506 }
 507
 508 static const struct lttng_kernel_ring_buffer_config client_config = {
 509         .cb.ring_buffer_clock_read = client_ring_buffer_clock_read,
 510         .cb.record_header_size = client_record_header_size,
 511         .cb.subbuffer_header_size = client_packet_header_size,
 512         .cb.buffer_begin = client_buffer_begin,
 513         .cb.buffer_end = client_buffer_end,
 514         .cb.buffer_create = client_buffer_create,
 515         .cb.buffer_finalize = client_buffer_finalize,
 516
 517         .tsc_bits = LTTNG_COMPACT_TSC_BITS,
 518         .alloc = RING_BUFFER_ALLOC_PER_CPU,
 519         .sync = RING_BUFFER_SYNC_PER_CPU,
 520         .mode = RING_BUFFER_MODE_TEMPLATE,
 521         .backend = RING_BUFFER_PAGE,
 522         .output = RING_BUFFER_OUTPUT_TEMPLATE,
 523         .oops = RING_BUFFER_OOPS_CONSISTENCY,
 524         .ipi = RING_BUFFER_IPI_BARRIER,
 525         .wakeup = RING_BUFFER_WAKEUP_BY_TIMER,
 526 };
 527
 528 static
 529 void release_priv_ops(void *priv_ops)
 530 {
 531         module_put(THIS_MODULE);
 532 }
 533
 534 static
 535 void lttng_channel_destroy(struct lttng_kernel_ring_buffer_channel *chan)
 536 {
 537         channel_destroy(chan);
 538 }
 539
 540 static
 541 struct lttng_kernel_ring_buffer_channel *_channel_create(const char *name,
 542                                 void *priv, void *buf_addr,
 543                                 size_t subbuf_size, size_t num_subbuf,
 544                                 unsigned int switch_timer_interval,
 545                                 unsigned int read_timer_interval)
 546 {
 547         struct lttng_kernel_channel_buffer *lttng_chan = priv;
 548         struct lttng_kernel_ring_buffer_channel *chan;
 549
 550         chan = channel_create(&client_config, name, lttng_chan, buf_addr,
 551                               subbuf_size, num_subbuf, switch_timer_interval,
 552                               read_timer_interval);
 553         if (chan) {
 554                 /*
 555                  * Ensure this module is not unloaded before we finish
 556                  * using lttng_relay_transport.ops.
 557                  */
 558                 if (!try_module_get(THIS_MODULE)) {
 559                         printk(KERN_WARNING "LTTng: Can't lock transport module.\n");
 560                         goto error;
 561                 }
 562                 chan->backend.priv_ops = &lttng_relay_transport.ops;
 563                 chan->backend.release_priv_ops = release_priv_ops;
 564         }
 565         return chan;
 566
 567 error:
 568         lttng_channel_destroy(chan);
 569         return NULL;
 570 }
 571
 572 static
 573 struct lttng_kernel_ring_buffer *lttng_buffer_read_open(struct lttng_kernel_ring_buffer_channel *chan)
 574 {
 575         struct lttng_kernel_ring_buffer *buf;
 576         int cpu;
 577
 578         for_each_channel_cpu(cpu, chan) {
 579                 buf = channel_get_ring_buffer(&client_config, chan, cpu);
 580                 if (!lib_ring_buffer_open_read(buf))
 581                         return buf;
 582         }
 583         return NULL;
 584 }
 585
 586 static
 587 int lttng_buffer_has_read_closed_stream(struct lttng_kernel_ring_buffer_channel *chan)
 588 {
 589         struct lttng_kernel_ring_buffer *buf;
 590         int cpu;
 591
 592         for_each_channel_cpu(cpu, chan) {
 593                 buf = channel_get_ring_buffer(&client_config, chan, cpu);
 594                 if (!atomic_long_read(&buf->active_readers))
 595                         return 1;
 596         }
 597         return 0;
 598 }
 599
 600 static
 601 void lttng_buffer_read_close(struct lttng_kernel_ring_buffer *buf)
 602 {
 603         lib_ring_buffer_release_read(buf);
 604 }
 605
 606 static
 607 int lttng_event_reserve(struct lttng_kernel_ring_buffer_ctx *ctx)
 608 {
 609         struct lttng_kernel_event_recorder *event_recorder = ctx->client_priv;
 610         struct lttng_kernel_channel_buffer *lttng_chan = event_recorder->chan;
 611         struct lttng_client_ctx client_ctx;
 612         int ret, cpu;
 613         uint32_t event_id;
 614
 615         cpu = lib_ring_buffer_get_cpu(&client_config);
 616         if (unlikely(cpu < 0))
 617                 return -EPERM;
 618         event_id = event_recorder->priv->id;
 619         memset(&ctx->priv, 0, sizeof(ctx->priv));
 620         ctx->priv.chan = lttng_chan->priv->rb_chan;
 621         ctx->priv.reserve_cpu = cpu;
 622
 623         /* Compute internal size of context structures. */
 624         ctx_get_struct_size(lttng_chan->priv->ctx, &client_ctx.packet_context_len, lttng_chan, ctx);
 625
 626         switch (lttng_chan->priv->header_type) {
 627         case 1: /* compact */
 628                 if (event_id > 30)
 629                         ctx->priv.rflags |= LTTNG_RFLAG_EXTENDED;
 630                 break;
 631         case 2: /* large */
 632                 if (event_id > 65534)
 633                         ctx->priv.rflags |= LTTNG_RFLAG_EXTENDED;
 634                 break;
 635         default:
 636                 WARN_ON_ONCE(1);
 637         }
 638
 639         ret = lib_ring_buffer_reserve(&client_config, ctx, &client_ctx);
 640         if (unlikely(ret))
 641                 goto put;
 642         lib_ring_buffer_backend_get_pages(&client_config, ctx,
 643                         &ctx->priv.backend_pages);
 644         lttng_write_event_header(&client_config, ctx, event_id);
 645         return 0;
 646 put:
 647         lib_ring_buffer_put_cpu(&client_config);
 648         return ret;
 649 }
 650
 651 static
 652 void lttng_event_commit(struct lttng_kernel_ring_buffer_ctx *ctx)
 653 {
 654         lib_ring_buffer_commit(&client_config, ctx);
 655         lib_ring_buffer_put_cpu(&client_config);
 656 }
 657
 658 static
 659 void lttng_event_write(struct lttng_kernel_ring_buffer_ctx *ctx, const void *src,
 660                      size_t len)
 661 {
 662         lib_ring_buffer_write(&client_config, ctx, src, len);
 663 }
 664
 665 static
 666 void lttng_event_write_from_user(struct lttng_kernel_ring_buffer_ctx *ctx,
 667                                const void __user *src, size_t len)
 668 {
 669         lib_ring_buffer_copy_from_user_inatomic(&client_config, ctx, src, len);
 670 }
 671
 672 static
 673 void lttng_event_memset(struct lttng_kernel_ring_buffer_ctx *ctx,
 674                 int c, size_t len)
 675 {
 676         lib_ring_buffer_memset(&client_config, ctx, c, len);
 677 }
 678
 679 static
 680 void lttng_event_strcpy(struct lttng_kernel_ring_buffer_ctx *ctx, const char *src,
 681                 size_t len)
 682 {
 683         lib_ring_buffer_strcpy(&client_config, ctx, src, len, '#');
 684 }
 685
 686 static
 687 void lttng_event_strcpy_from_user(struct lttng_kernel_ring_buffer_ctx *ctx,
 688                 const char __user *src, size_t len)
 689 {
 690         lib_ring_buffer_strcpy_from_user_inatomic(&client_config, ctx, src,
 691                         len, '#');
 692 }
 693
 694 static
 695 void lttng_channel_buffer_lost_event_too_big(struct lttng_kernel_channel_buffer *lttng_chan)
 696 {
 697         lib_ring_buffer_lost_event_too_big(lttng_chan->priv->rb_chan);
 698 }
 699
 700 static
 701 wait_queue_head_t *lttng_get_writer_buf_wait_queue(struct lttng_kernel_ring_buffer_channel *chan, int cpu)
 702 {
 703         struct lttng_kernel_ring_buffer *buf = channel_get_ring_buffer(&client_config,
 704                                         chan, cpu);
 705         return &buf->write_wait;
 706 }
 707
 708 static
 709 wait_queue_head_t *lttng_get_hp_wait_queue(struct lttng_kernel_ring_buffer_channel *chan)
 710 {
 711         return &chan->hp_wait;
 712 }
 713
 714 static
 715 int lttng_is_finalized(struct lttng_kernel_ring_buffer_channel *chan)
 716 {
 717         return lib_ring_buffer_channel_is_finalized(chan);
 718 }
 719
 720 static
 721 int lttng_is_disabled(struct lttng_kernel_ring_buffer_channel *chan)
 722 {
 723         return lib_ring_buffer_channel_is_disabled(chan);
 724 }
 725
 726 static struct lttng_transport lttng_relay_transport = {
 727         .name = "relay-" RING_BUFFER_MODE_TEMPLATE_STRING,
 728         .owner = THIS_MODULE,
 729         .ops = {
 730                 .priv = __LTTNG_COMPOUND_LITERAL(struct lttng_kernel_channel_buffer_ops_private, {
 731                         .pub = &lttng_relay_transport.ops,
 732                         .channel_create = _channel_create,
 733                         .channel_destroy = lttng_channel_destroy,
 734                         .buffer_read_open = lttng_buffer_read_open,
 735                         .buffer_has_read_closed_stream =
 736                                 lttng_buffer_has_read_closed_stream,
 737                         .buffer_read_close = lttng_buffer_read_close,
 738                         .packet_avail_size = NULL,      /* Would be racy anyway */
 739                         .get_writer_buf_wait_queue = lttng_get_writer_buf_wait_queue,
 740                         .get_hp_wait_queue = lttng_get_hp_wait_queue,
 741                         .is_finalized = lttng_is_finalized,
 742                         .is_disabled = lttng_is_disabled,
 743                         .timestamp_begin = client_timestamp_begin,
 744                         .timestamp_end = client_timestamp_end,
 745                         .events_discarded = client_events_discarded,
 746                         .content_size = client_content_size,
 747                         .packet_size = client_packet_size,
 748                         .stream_id = client_stream_id,
 749                         .current_timestamp = client_current_timestamp,
 750                         .sequence_number = client_sequence_number,
 751                         .instance_id = client_instance_id,
 752                 }),
 753                 .event_reserve = lttng_event_reserve,
 754                 .event_commit = lttng_event_commit,
 755                 .event_write = lttng_event_write,
 756                 .event_write_from_user = lttng_event_write_from_user,
 757                 .event_memset = lttng_event_memset,
 758                 .event_strcpy = lttng_event_strcpy,
 759                 .event_strcpy_from_user = lttng_event_strcpy_from_user,
 760                 .lost_event_too_big = lttng_channel_buffer_lost_event_too_big,
 761         },
 762 };
 763
 764 static int __init lttng_ring_buffer_client_init(void)
 765 {
 766         /*
 767          * This vmalloc sync all also takes care of the lib ring buffer
 768          * vmalloc'd module pages when it is built as a module into LTTng.
 769          */
 770         wrapper_vmalloc_sync_mappings();
 771         lttng_transport_register(&lttng_relay_transport);
 772         return 0;
 773 }
 774
 775 module_init(lttng_ring_buffer_client_init);
 776
 777 static void __exit lttng_ring_buffer_client_exit(void)
 778 {
 779         lttng_transport_unregister(&lttng_relay_transport);
 780 }
 781
 782 module_exit(lttng_ring_buffer_client_exit);
 783
 784 MODULE_LICENSE("GPL and additional rights");
 785 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 786 MODULE_DESCRIPTION("LTTng ring buffer " RING_BUFFER_MODE_TEMPLATE_STRING
 787                    " client");
 788 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 789         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 790         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 791         LTTNG_MODULES_EXTRAVERSION);