src/lttng-event-notifier-notification.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-event-notifier-notification.c
   4  *
   5  * Copyright (C) 2020 Francis Deslauriers <francis.deslauriers@efficios.com>
   6  */
   7
   8 #include <linux/bug.h>
   9
  10 #include <lttng/lttng-bytecode.h>
  11 #include <lttng/events.h>
  12 #include <lttng/msgpack.h>
  13 #include <lttng/event-notifier-notification.h>
  14 #include <lttng/events-internal.h>
  15 #include <lttng/probe-user.h>
  16 #include <wrapper/barrier.h>
  17
  18 /*
  19  * The capture buffer size needs to be below 1024 bytes to avoid the
  20  * frame to be larger than the 1024 limit enforced by the kernel. If we
  21  * ever need to increase it, we will need to use a memory allocation
  22  * scheme which allows allocating temporary memory chunks from the
  23  * instrumentation sites. This could be done by adapting lttng
  24  * tp-mempool to become nmi-safe and lock-free.
  25  */
  26 #define CAPTURE_BUFFER_SIZE 512
  27
  28 #define MSG_WRITE_NIL_LEN 1
  29
  30 struct lttng_event_notifier_notification {
  31         int notification_fd;
  32         uint64_t event_notifier_token;
  33         uint8_t capture_buf[CAPTURE_BUFFER_SIZE];
  34         struct lttng_msgpack_writer writer;
  35         bool has_captures;
  36 };
  37
  38 static
  39 int capture_enum(struct lttng_msgpack_writer *writer,
  40                 struct lttng_interpreter_output *output)
  41 {
  42         int ret;
  43
  44         /*
  45          * Enums are captured as a map containing 2 key-value pairs. Such as:
  46          * - type: enum
  47          *   value: 177
  48          */
  49         ret = lttng_msgpack_begin_map(writer, 2);
  50         if (ret) {
  51                 goto end;
  52         }
  53
  54         ret = lttng_msgpack_write_str(writer, "type");
  55         if (ret) {
  56                 goto end;
  57         }
  58
  59         ret = lttng_msgpack_write_str(writer, "enum");
  60         if (ret) {
  61                 goto end;
  62         }
  63
  64         ret = lttng_msgpack_write_str(writer, "value");
  65         if (ret) {
  66                 goto end;
  67         }
  68
  69         switch (output->type) {
  70         case LTTNG_INTERPRETER_TYPE_SIGNED_ENUM:
  71                 ret = lttng_msgpack_write_signed_integer(writer, output->u.s);
  72                 if (ret) {
  73                         goto end;
  74                 }
  75                 break;
  76         case LTTNG_INTERPRETER_TYPE_UNSIGNED_ENUM:
  77                 ret = lttng_msgpack_write_signed_integer(writer, output->u.u);
  78                 if (ret) {
  79                         goto end;
  80                 }
  81                 break;
  82         default:
  83                 WARN_ON_ONCE(1);
  84         }
  85
  86         ret = lttng_msgpack_end_map(writer);
  87 end:
  88         return ret;
  89 }
  90
  91 static
  92 int64_t capture_sequence_element_signed(uint8_t *ptr,
  93                 const struct lttng_kernel_type_integer *type)
  94 {
  95         int64_t value = 0;
  96         unsigned int size = type->size;
  97         bool user = type->user;
  98         bool byte_order_reversed = type->reverse_byte_order;
  99
 100         switch (size) {
 101         case 8:
 102         {
 103                 int8_t tmp;
 104
 105                 if (user) {
 106                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(int8_t)))
 107                                 tmp = 0;
 108                 } else {
 109                         tmp = *ptr;
 110                 }
 111                 value = tmp;
 112                 break;
 113         }
 114         case 16:
 115         {
 116                 int16_t tmp;
 117
 118                 if (user) {
 119                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(int16_t)))
 120                                 tmp = 0;
 121                 } else {
 122                         tmp = *(int16_t *) ptr;
 123                 }
 124                 if (byte_order_reversed)
 125                         __swab16s(&tmp);
 126                 value = tmp;
 127                 break;
 128         }
 129         case 32:
 130         {
 131                 int32_t tmp;
 132
 133                 if (user) {
 134                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(int32_t)))
 135                                 tmp = 0;
 136                 } else {
 137                         tmp = *(int32_t *) ptr;
 138                 }
 139                 if (byte_order_reversed)
 140                         __swab32s(&tmp);
 141                 value = tmp;
 142                 break;
 143         }
 144         case 64:
 145         {
 146                 int64_t tmp;
 147
 148                 if (user) {
 149                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(int64_t)))
 150                                 tmp = 0;
 151                 } else {
 152                         tmp = *(int64_t *) ptr;
 153                 }
 154                 if (byte_order_reversed)
 155                         __swab64s(&tmp);
 156                 value = tmp;
 157                 break;
 158         }
 159         default:
 160                 WARN_ON_ONCE(1);
 161         }
 162
 163         return value;
 164 }
 165
 166 static
 167 uint64_t capture_sequence_element_unsigned(uint8_t *ptr,
 168                 const struct lttng_kernel_type_integer *type)
 169 {
 170         uint64_t value = 0;
 171         unsigned int size = type->size;
 172         bool user = type->user;
 173         bool byte_order_reversed = type->reverse_byte_order;
 174
 175         switch (size) {
 176         case 8:
 177         {
 178                 uint8_t tmp;
 179
 180                 if (user) {
 181                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(uint8_t)))
 182                                 tmp = 0;
 183                 } else {
 184                         tmp = *ptr;
 185                 }
 186                 value = tmp;
 187                 break;
 188         }
 189         case 16:
 190         {
 191                 uint16_t tmp;
 192
 193                 if (user) {
 194                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(uint16_t)))
 195                                 tmp = 0;
 196                 } else {
 197                         tmp = *(uint16_t *) ptr;
 198                 }
 199                 if (byte_order_reversed)
 200                         __swab16s(&tmp);
 201                 value = tmp;
 202                 break;
 203         }
 204         case 32:
 205         {
 206                 uint32_t tmp;
 207
 208                 if (user) {
 209                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(uint32_t)))
 210                                 tmp = 0;
 211                 } else {
 212                         tmp = *(uint32_t *) ptr;
 213                 }
 214                 if (byte_order_reversed)
 215                         __swab32s(&tmp);
 216                 value = tmp;
 217                 break;
 218         }
 219         case 64:
 220         {
 221                 uint64_t tmp;
 222
 223                 if (user) {
 224                         if (lttng_copy_from_user_check_nofault(&tmp, ptr, sizeof(uint64_t)))
 225                                 tmp = 0;
 226                 } else {
 227                         tmp = *(uint64_t *) ptr;
 228                 }
 229                 if (byte_order_reversed)
 230                         __swab64s(&tmp);
 231                 value = tmp;
 232                 break;
 233         }
 234         default:
 235                 WARN_ON_ONCE(1);
 236         }
 237
 238         return value;
 239 }
 240
 241 int capture_sequence(struct lttng_msgpack_writer *writer,
 242                 struct lttng_interpreter_output *output)
 243 {
 244         const struct lttng_kernel_type_integer *integer_type = NULL;
 245         const struct lttng_kernel_type_common *nested_type;
 246         uint8_t *ptr;
 247         bool signedness;
 248         int ret, i;
 249
 250         ret = lttng_msgpack_begin_array(writer, output->u.sequence.nr_elem);
 251         if (ret) {
 252                 goto end;
 253         }
 254
 255         ptr = (uint8_t *) output->u.sequence.ptr;
 256         nested_type = output->u.sequence.nested_type;
 257         switch (nested_type->type) {
 258         case lttng_kernel_type_integer:
 259                 integer_type = lttng_kernel_get_type_integer(nested_type);
 260                 break;
 261         case lttng_kernel_type_enum:
 262                 /* Treat enumeration as an integer. */
 263                 integer_type = lttng_kernel_get_type_integer(lttng_kernel_get_type_enum(nested_type)->container_type);
 264                 break;
 265         default:
 266                 /* Capture of array of non-integer are not supported. */
 267                 WARN_ON_ONCE(1);
 268                 ret = -1;
 269                 goto end;
 270         }
 271         signedness = integer_type->signedness;
 272         for (i = 0; i < output->u.sequence.nr_elem; i++) {
 273                 if (signedness) {
 274                         ret = lttng_msgpack_write_signed_integer(writer,
 275                                 capture_sequence_element_signed(ptr, integer_type));
 276                         if (ret) {
 277                                 goto end;
 278                         }
 279                 } else {
 280                         ret = lttng_msgpack_write_unsigned_integer(writer,
 281                                 capture_sequence_element_unsigned(ptr, integer_type));
 282                         if (ret) {
 283                                 goto end;
 284                         }
 285                 }
 286
 287                 /*
 288                  * We assume that alignment is smaller or equal to the size.
 289                  * This currently holds true but if it changes in the future,
 290                  * we will want to change the pointer arithmetics below to
 291                  * take into account that the next element might be further
 292                  * away.
 293                  */
 294                 WARN_ON_ONCE(integer_type->alignment > integer_type->size);
 295
 296                 /* Size is in number of bits. */
 297                 ptr += (integer_type->size / CHAR_BIT) ;
 298         }
 299
 300         ret = lttng_msgpack_end_array(writer);
 301 end:
 302         return ret;
 303 }
 304
 305 static
 306 int notification_append_capture(
 307                 struct lttng_event_notifier_notification *notif,
 308                 struct lttng_interpreter_output *output)
 309 {
 310         struct lttng_msgpack_writer *writer = &notif->writer;
 311         int ret = 0;
 312
 313         switch (output->type) {
 314         case LTTNG_INTERPRETER_TYPE_S64:
 315                 ret = lttng_msgpack_write_signed_integer(writer, output->u.s);
 316                 break;
 317         case LTTNG_INTERPRETER_TYPE_U64:
 318                 ret = lttng_msgpack_write_unsigned_integer(writer, output->u.u);
 319                 break;
 320         case LTTNG_INTERPRETER_TYPE_STRING:
 321                 if (output->u.str.user) {
 322                         ret = lttng_msgpack_write_user_str(writer, output->u.str.user_str);
 323                 } else {
 324                         ret = lttng_msgpack_write_str(writer, output->u.str.str);
 325                 }
 326                 break;
 327         case LTTNG_INTERPRETER_TYPE_SEQUENCE:
 328                 ret = capture_sequence(writer, output);
 329                 break;
 330         case LTTNG_INTERPRETER_TYPE_SIGNED_ENUM:
 331         case LTTNG_INTERPRETER_TYPE_UNSIGNED_ENUM:
 332                 ret = capture_enum(writer, output);
 333                 break;
 334         default:
 335                 ret = -1;
 336                 WARN_ON_ONCE(1);
 337         }
 338         return ret;
 339 }
 340
 341 static
 342 int notification_append_empty_capture(
 343                 struct lttng_event_notifier_notification *notif)
 344 {
 345         return lttng_msgpack_write_nil(&notif->writer);
 346 }
 347
 348 static
 349 int notification_init(struct lttng_event_notifier_notification *notif,
 350                 struct lttng_kernel_event_notifier *event_notifier)
 351 {
 352         struct lttng_msgpack_writer *writer = &notif->writer;
 353         int ret = 0;
 354
 355         notif->has_captures = false;
 356
 357         if (event_notifier->priv->num_captures > 0) {
 358                 lttng_msgpack_writer_init(writer, notif->capture_buf,
 359                                 CAPTURE_BUFFER_SIZE);
 360
 361                 ret = lttng_msgpack_begin_array(writer, event_notifier->priv->num_captures);
 362                 if (ret) {
 363                         goto end;
 364                 }
 365
 366                 notif->has_captures = true;
 367         }
 368
 369 end:
 370         return ret;
 371 }
 372
 373 static
 374 void record_error(struct lttng_kernel_event_notifier *event_notifier)
 375 {
 376
 377         struct lttng_event_notifier_group *event_notifier_group = event_notifier->priv->group;
 378         struct lttng_counter *error_counter;
 379         size_t dimension_index[1];
 380         int ret;
 381
 382         /*
 383          * lttng_smp_load_acquire paired with lttng_smp_store_release orders
 384          * creation of the error counter and setting error_counter_len
 385          * before the error_counter is used.
 386          */
 387         error_counter = lttng_smp_load_acquire(&event_notifier_group->error_counter);
 388         /* This group may not have an error counter attached to it. */
 389         if (!error_counter)
 390                 return;
 391
 392         dimension_index[0] = event_notifier->priv->error_counter_index;
 393
 394         ret = error_counter->ops->counter_add(error_counter->counter,
 395                         dimension_index, 1);
 396         if (ret)
 397                 WARN_ON_ONCE(1);
 398 }
 399
 400 static
 401 void notification_send(struct lttng_event_notifier_notification *notif,
 402                 struct lttng_kernel_event_notifier *event_notifier)
 403 {
 404         struct lttng_event_notifier_group *event_notifier_group = event_notifier->priv->group;
 405         struct lttng_kernel_ring_buffer_ctx ctx;
 406         struct lttng_kernel_abi_event_notifier_notification kernel_notif;
 407         size_t capture_buffer_content_len, reserve_size;
 408         int ret;
 409
 410         reserve_size = sizeof(kernel_notif);
 411         kernel_notif.token = event_notifier->priv->parent.user_token;
 412
 413         if (notif->has_captures) {
 414                 capture_buffer_content_len = notif->writer.write_pos - notif->writer.buffer;
 415         } else {
 416                 capture_buffer_content_len = 0;
 417         }
 418
 419         WARN_ON_ONCE(capture_buffer_content_len > CAPTURE_BUFFER_SIZE);
 420
 421         reserve_size += capture_buffer_content_len;
 422         kernel_notif.capture_buf_size = capture_buffer_content_len;
 423
 424         lib_ring_buffer_ctx_init(&ctx, event_notifier_group->chan, reserve_size,
 425                         lttng_alignof(kernel_notif), NULL);
 426         ret = event_notifier_group->ops->event_reserve(&ctx);
 427         if (ret < 0) {
 428                 record_error(event_notifier);
 429                 return;
 430         }
 431
 432         /* Write the notif structure. */
 433         event_notifier_group->ops->event_write(&ctx, &kernel_notif,
 434                         sizeof(kernel_notif), lttng_alignof(kernel_notif));
 435
 436         /*
 437          * Write the capture buffer. No need to realigned as the below is a raw
 438          * char* buffer.
 439          */
 440         event_notifier_group->ops->event_write(&ctx, &notif->capture_buf,
 441                         capture_buffer_content_len, 1);
 442
 443         event_notifier_group->ops->event_commit(&ctx);
 444         irq_work_queue(&event_notifier_group->wakeup_pending);
 445 }
 446
 447 /*
 448  * Validate that the buffer has enough room to hold empty capture fields.
 449  */
 450 static
 451 bool validate_buffer_len(struct lttng_event_notifier_notification *notif, size_t captures_left)
 452 {
 453         if (notif->writer.end_write_pos - notif->writer.write_pos < MSG_WRITE_NIL_LEN * captures_left)
 454                 return false;
 455         return true;
 456 }
 457
 458 void lttng_event_notifier_notification_send(struct lttng_kernel_event_notifier *event_notifier,
 459                 const char *stack_data,
 460                 struct lttng_kernel_probe_ctx *probe_ctx,
 461                 struct lttng_kernel_notification_ctx *notif_ctx)
 462 {
 463         struct lttng_event_notifier_notification notif = { 0 };
 464         size_t captures_left;
 465
 466         if (notification_init(&notif, event_notifier))
 467                 goto error;
 468
 469         captures_left = event_notifier->priv->num_captures;
 470         if (!validate_buffer_len(&notif, captures_left))
 471                 goto error;
 472
 473         if (unlikely(notif_ctx->eval_capture)) {
 474                 struct lttng_kernel_bytecode_runtime *capture_bc_runtime;
 475
 476                 /*
 477                  * Iterate over all the capture bytecodes. If the interpreter
 478                  * functions returns successfully, append the value of the
 479                  * `output` parameter to the capture buffer. If the interpreter
 480                  * fails, append an empty capture to the buffer.
 481                  */
 482                 list_for_each_entry_rcu(capture_bc_runtime,
 483                                 &event_notifier->priv->capture_bytecode_runtime_head, node) {
 484                         struct lttng_interpreter_output output;
 485                         uint8_t *save_pos;
 486                         int ret = -1;
 487
 488                         lttng_msgpack_save_writer_pos(&notif.writer, &save_pos);
 489                         captures_left--;
 490                         if (capture_bc_runtime->interpreter_func(capture_bc_runtime,
 491                                         stack_data, probe_ctx, &output) == LTTNG_KERNEL_BYTECODE_INTERPRETER_OK)
 492                                 ret = notification_append_capture(&notif, &output);
 493                         if (ret || !validate_buffer_len(&notif, captures_left)) {
 494                                 /*
 495                                  * On append capture error or if the generated
 496                                  * buffer data would not leave enough room to
 497                                  * write empty capture fields for the remaining
 498                                  * fields, skip the field capture by restoring
 499                                  * the msgpack writer position and writing an
 500                                  * empty capture field.
 501                                  */
 502                                 lttng_msgpack_restore_writer_pos(&notif.writer, save_pos);
 503                                 ret = notification_append_empty_capture(&notif);
 504                                 WARN_ON_ONCE(ret);
 505                         }
 506                 }
 507         }
 508
 509         if (notif.has_captures && lttng_msgpack_end_array(&notif.writer))
 510                 goto error;
 511
 512         /*
 513          * Send the notification (including the capture buffer) to the
 514          * sessiond.
 515          */
 516         notification_send(&notif, event_notifier);
 517         return;
 518
 519 error:
 520         record_error(event_notifier);
 521         return;
 522 }