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