liblttng-ust/event-notifier-notification.c

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2020 Francis Deslauriers <francis.deslauriers@efficios.com>
   5  */
   6
   7 #define _LGPL_SOURCE
   8
   9 #include <assert.h>
  10 #include <errno.h>
  11 #include <limits.h>
  12
  13 #include <lttng/ust-endian.h>
  14 #include <usterr-signal-safe.h>
  15 #include <urcu/rculist.h>
  16
  17 #include "ust-events-internal.h"
  18 #include "../libmsgpack/msgpack.h"
  19 #include "lttng-bytecode.h"
  20 #include "ust-share.h"
  21
  22 /*
  23  * We want this write to be atomic AND non-blocking, meaning that we
  24  * want to write either everything OR nothing.
  25  * According to `pipe(7)`, writes that are less than `PIPE_BUF` bytes must be
  26  * atomic, so we bound the capture buffer size to the `PIPE_BUF` minus the size
  27  * of the notification struct we are sending alongside the capture buffer.
  28  */
  29 #define CAPTURE_BUFFER_SIZE \
  30         (PIPE_BUF - sizeof(struct lttng_ust_abi_event_notifier_notification) - 1)
  31
  32 struct lttng_event_notifier_notification {
  33         int notification_fd;
  34         uint64_t event_notifier_token;
  35         uint8_t capture_buf[CAPTURE_BUFFER_SIZE];
  36         struct lttng_msgpack_writer writer;
  37         bool has_captures;
  38 };
  39
  40 static
  41 void capture_enum(struct lttng_msgpack_writer *writer,
  42                 struct lttng_interpreter_output *output)
  43 {
  44         lttng_msgpack_begin_map(writer, 2);
  45         lttng_msgpack_write_str(writer, "type");
  46         lttng_msgpack_write_str(writer, "enum");
  47
  48         lttng_msgpack_write_str(writer, "value");
  49
  50         switch (output->type) {
  51         case LTTNG_INTERPRETER_TYPE_SIGNED_ENUM:
  52                 lttng_msgpack_write_signed_integer(writer, output->u.s);
  53                 break;
  54         case LTTNG_INTERPRETER_TYPE_UNSIGNED_ENUM:
  55                 lttng_msgpack_write_signed_integer(writer, output->u.u);
  56                 break;
  57         default:
  58                 abort();
  59         }
  60
  61         lttng_msgpack_end_map(writer);
  62 }
  63
  64 static
  65 int64_t capture_sequence_element_signed(uint8_t *ptr,
  66                 struct lttng_ust_type_integer *integer_type)
  67 {
  68         int64_t value;
  69         unsigned int size = integer_type->size;
  70         bool byte_order_reversed = integer_type->reverse_byte_order;
  71
  72         switch (size) {
  73         case 8:
  74                 value = *ptr;
  75                 break;
  76         case 16:
  77         {
  78                 int16_t tmp;
  79                 tmp = *(int16_t *) ptr;
  80                 if (byte_order_reversed)
  81                         tmp = bswap_16(tmp);
  82
  83                 value = tmp;
  84                 break;
  85         }
  86         case 32:
  87         {
  88                 int32_t tmp;
  89                 tmp = *(int32_t *) ptr;
  90                 if (byte_order_reversed)
  91                         tmp = bswap_32(tmp);
  92
  93                 value = tmp;
  94                 break;
  95         }
  96         case 64:
  97         {
  98                 int64_t tmp;
  99                 tmp = *(int64_t *) ptr;
 100                 if (byte_order_reversed)
 101                         tmp = bswap_64(tmp);
 102
 103                 value = tmp;
 104                 break;
 105         }
 106         default:
 107                 abort();
 108         }
 109
 110         return value;
 111 }
 112
 113 static
 114 uint64_t capture_sequence_element_unsigned(uint8_t *ptr,
 115                 struct lttng_ust_type_integer *integer_type)
 116 {
 117         uint64_t value;
 118         unsigned int size = integer_type->size;
 119         bool byte_order_reversed = integer_type->reverse_byte_order;
 120
 121         switch (size) {
 122         case 8:
 123                 value = *ptr;
 124                 break;
 125         case 16:
 126         {
 127                 uint16_t tmp;
 128                 tmp = *(uint16_t *) ptr;
 129                 if (byte_order_reversed)
 130                         tmp = bswap_16(tmp);
 131
 132                 value = tmp;
 133                 break;
 134         }
 135         case 32:
 136         {
 137                 uint32_t tmp;
 138                 tmp = *(uint32_t *) ptr;
 139                 if (byte_order_reversed)
 140                         tmp = bswap_32(tmp);
 141
 142                 value = tmp;
 143                 break;
 144         }
 145         case 64:
 146         {
 147                 uint64_t tmp;
 148                 tmp = *(uint64_t *) ptr;
 149                 if (byte_order_reversed)
 150                         tmp = bswap_64(tmp);
 151
 152                 value = tmp;
 153                 break;
 154         }
 155         default:
 156                 abort();
 157         }
 158
 159         return value;
 160 }
 161
 162 static
 163 void capture_sequence(struct lttng_msgpack_writer *writer,
 164                 struct lttng_interpreter_output *output)
 165 {
 166         struct lttng_ust_type_integer *integer_type;
 167         struct lttng_ust_type_common *nested_type;
 168         uint8_t *ptr;
 169         bool signedness;
 170         int i;
 171
 172         lttng_msgpack_begin_array(writer, output->u.sequence.nr_elem);
 173
 174         ptr = (uint8_t *) output->u.sequence.ptr;
 175         nested_type = output->u.sequence.nested_type;
 176         switch (nested_type->type) {
 177         case lttng_ust_type_integer:
 178                 integer_type = lttng_ust_get_type_integer(nested_type);
 179                 break;
 180         case lttng_ust_type_enum:
 181                 /* Treat enumeration as an integer. */
 182                 integer_type = lttng_ust_get_type_integer(lttng_ust_get_type_enum(nested_type)->container_type);
 183                 break;
 184         default:
 185                 /* Capture of array of non-integer are not supported. */
 186                 abort();
 187         }
 188         signedness = integer_type->signedness;
 189         for (i = 0; i < output->u.sequence.nr_elem; i++) {
 190                 if (signedness) {
 191                         lttng_msgpack_write_signed_integer(writer,
 192                                 capture_sequence_element_signed(ptr, integer_type));
 193                 } else {
 194                         lttng_msgpack_write_unsigned_integer(writer,
 195                                 capture_sequence_element_unsigned(ptr, integer_type));
 196                 }
 197
 198                 /*
 199                  * We assume that alignment is smaller or equal to the size.
 200                  * This currently holds true but if it changes in the future,
 201                  * we will want to change the pointer arithmetics below to
 202                  * take into account that the next element might be further
 203                  * away.
 204                  */
 205                 assert(integer_type->alignment <= integer_type->size);
 206
 207                 /* Size is in number of bits. */
 208                 ptr += (integer_type->size / CHAR_BIT) ;
 209         }
 210
 211         lttng_msgpack_end_array(writer);
 212 }
 213
 214 static
 215 void notification_init(struct lttng_event_notifier_notification *notif,
 216                 struct lttng_ust_event_notifier *event_notifier)
 217 {
 218         struct lttng_msgpack_writer *writer = &notif->writer;
 219
 220         notif->event_notifier_token = event_notifier->priv->parent.user_token;
 221         notif->notification_fd = event_notifier->priv->group->notification_fd;
 222         notif->has_captures = false;
 223
 224         if (event_notifier->priv->num_captures > 0) {
 225                 lttng_msgpack_writer_init(writer, notif->capture_buf,
 226                                 CAPTURE_BUFFER_SIZE);
 227
 228                 lttng_msgpack_begin_array(writer, event_notifier->priv->num_captures);
 229                 notif->has_captures = true;
 230         }
 231 }
 232
 233 static
 234 void notification_append_capture(
 235                 struct lttng_event_notifier_notification *notif,
 236                 struct lttng_interpreter_output *output)
 237 {
 238         struct lttng_msgpack_writer *writer = &notif->writer;
 239
 240         switch (output->type) {
 241         case LTTNG_INTERPRETER_TYPE_S64:
 242                 lttng_msgpack_write_signed_integer(writer, output->u.s);
 243                 break;
 244         case LTTNG_INTERPRETER_TYPE_U64:
 245                 lttng_msgpack_write_unsigned_integer(writer, output->u.u);
 246                 break;
 247         case LTTNG_INTERPRETER_TYPE_DOUBLE:
 248                 lttng_msgpack_write_double(writer, output->u.d);
 249                 break;
 250         case LTTNG_INTERPRETER_TYPE_STRING:
 251                 lttng_msgpack_write_str(writer, output->u.str.str);
 252                 break;
 253         case LTTNG_INTERPRETER_TYPE_SEQUENCE:
 254                 capture_sequence(writer, output);
 255                 break;
 256         case LTTNG_INTERPRETER_TYPE_SIGNED_ENUM:
 257         case LTTNG_INTERPRETER_TYPE_UNSIGNED_ENUM:
 258                 capture_enum(writer, output);
 259                 break;
 260         default:
 261                 abort();
 262         }
 263 }
 264
 265 static
 266 void notification_append_empty_capture(
 267                 struct lttng_event_notifier_notification *notif)
 268 {
 269         lttng_msgpack_write_nil(&notif->writer);
 270 }
 271
 272 static void record_error(struct lttng_ust_event_notifier *event_notifier)
 273 {
 274         struct lttng_event_notifier_group *event_notifier_group =
 275                         event_notifier->priv->group;
 276         struct lttng_counter *error_counter;
 277         size_t dimension_index[1];
 278         int ret;
 279
 280         error_counter = CMM_LOAD_SHARED(event_notifier_group->error_counter);
 281         /*
 282          * load-acquire paired with store-release orders creation of the
 283          * error counter and setting error_counter_len before the
 284          * error_counter is used.
 285          * Currently a full memory barrier is used, which could be
 286          * turned into acquire-release barriers.
 287          */
 288         cmm_smp_mb();
 289         /* This group may not have an error counter attached to it. */
 290         if (!error_counter)
 291                 return;
 292
 293         dimension_index[0] = event_notifier->priv->error_counter_index;
 294         ret = event_notifier_group->error_counter->ops->counter_add(
 295                         error_counter->counter, dimension_index, 1);
 296         if (ret)
 297                 WARN_ON_ONCE(1);
 298 }
 299
 300 static
 301 void notification_send(struct lttng_event_notifier_notification *notif,
 302                 struct lttng_ust_event_notifier *event_notifier)
 303 {
 304         ssize_t ret;
 305         size_t content_len;
 306         int iovec_count = 1;
 307         struct lttng_ust_abi_event_notifier_notification ust_notif = {0};
 308         struct iovec iov[2];
 309
 310         assert(notif);
 311
 312         ust_notif.token = event_notifier->priv->parent.user_token;
 313
 314         /*
 315          * Prepare sending the notification from multiple buffers using an
 316          * array of `struct iovec`. The first buffer of the vector is
 317          * notification structure itself and is always present.
 318          */
 319         iov[0].iov_base = &ust_notif;
 320         iov[0].iov_len = sizeof(ust_notif);
 321
 322         if (notif->has_captures) {
 323                 /*
 324                  * If captures were requested, the second buffer of the array
 325                  * is the capture buffer.
 326                  */
 327                 assert(notif->writer.buffer);
 328                 content_len = notif->writer.write_pos - notif->writer.buffer;
 329
 330                 assert(content_len > 0 && content_len <= CAPTURE_BUFFER_SIZE);
 331
 332                 iov[1].iov_base = notif->capture_buf;
 333                 iov[1].iov_len = content_len;
 334
 335                 iovec_count++;
 336         } else {
 337                 content_len = 0;
 338         }
 339
 340         /*
 341          * Update the capture buffer size so that receiver of the buffer will
 342          * know how much to expect.
 343          */
 344         ust_notif.capture_buf_size = content_len;
 345
 346         /* Send all the buffers. */
 347         ret = ust_patient_writev(notif->notification_fd, iov, iovec_count);
 348         if (ret == -1) {
 349                 if (errno == EAGAIN) {
 350                         record_error(event_notifier);
 351                         DBG("Cannot send event_notifier notification without blocking: %s",
 352                                 strerror(errno));
 353                 } else {
 354                         DBG("Error to sending event notifier notification: %s",
 355                                 strerror(errno));
 356                         abort();
 357                 }
 358         }
 359 }
 360
 361 void lttng_event_notifier_notification_send(
 362                 struct lttng_ust_event_notifier *event_notifier,
 363                 const char *stack_data,
 364                 struct lttng_ust_notification_ctx *notif_ctx)
 365 {
 366         /*
 367          * This function is called from the probe, we must do dynamic
 368          * allocation in this context.
 369          */
 370         struct lttng_event_notifier_notification notif = {0};
 371
 372         notification_init(&notif, event_notifier);
 373
 374         if (caa_unlikely(notif_ctx->eval_capture)) {
 375                 struct lttng_ust_bytecode_runtime *capture_bc_runtime;
 376
 377                 /*
 378                  * Iterate over all the capture bytecodes. If the interpreter
 379                  * functions returns successfully, append the value of the
 380                  * `output` parameter to the capture buffer. If the interpreter
 381                  * fails, append an empty capture to the buffer.
 382                  */
 383                 cds_list_for_each_entry_rcu(capture_bc_runtime,
 384                                 &event_notifier->priv->capture_bytecode_runtime_head, node) {
 385                         struct lttng_interpreter_output output;
 386
 387                         if (capture_bc_runtime->interpreter_func(capture_bc_runtime,
 388                                         stack_data, &output) == LTTNG_UST_BYTECODE_INTERPRETER_OK)
 389                                 notification_append_capture(&notif, &output);
 390                         else
 391                                 notification_append_empty_capture(&notif);
 392                 }
 393         }
 394
 395         /*
 396          * Send the notification (including the capture buffer) to the
 397          * sessiond.
 398          */
 399         notification_send(&notif, event_notifier);
 400 }