liblttng-ust/event-notifier-notification.c

   1 /*
   2  * event-notifier-notification.c
   3  *
   4  * Copyright (C) 2020 Francis Deslauriers <francis.deslauriers@efficios.com>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; only
   9  * version 2.1 of the License.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #define _LGPL_SOURCE
  22
  23 #include <assert.h>
  24 #include <errno.h>
  25 #include <lttng/ust-events.h>
  26 #include <lttng/ust-endian.h>
  27 #include <usterr-signal-safe.h>
  28
  29 #include "../libmsgpack/msgpack.h"
  30 #include "lttng-bytecode.h"
  31 #include "share.h"
  32
  33 /*
  34  * We want this write to be atomic AND non-blocking, meaning that we
  35  * want to write either everything OR nothing.
  36  * According to `pipe(7)`, writes that are less than `PIPE_BUF` bytes must be
  37  * atomic, so we bound the capture buffer size to the `PIPE_BUF` minus the size
  38  * of the notification struct we are sending alongside the capture buffer.
  39  */
  40 #define CAPTURE_BUFFER_SIZE \
  41         (PIPE_BUF - sizeof(struct lttng_ust_event_notifier_notification) - 1)
  42
  43 struct lttng_event_notifier_notification {
  44         int notification_fd;
  45         uint64_t event_notifier_token;
  46         uint8_t capture_buf[CAPTURE_BUFFER_SIZE];
  47         struct lttng_msgpack_writer writer;
  48         bool has_captures;
  49 };
  50
  51 static
  52 void capture_enum(struct lttng_msgpack_writer *writer,
  53                 struct lttng_interpreter_output *output)
  54 {
  55         lttng_msgpack_begin_map(writer, 2);
  56         lttng_msgpack_write_str(writer, "type");
  57         lttng_msgpack_write_str(writer, "enum");
  58
  59         lttng_msgpack_write_str(writer, "value");
  60
  61         switch (output->type) {
  62         case LTTNG_INTERPRETER_TYPE_SIGNED_ENUM:
  63                 lttng_msgpack_write_signed_integer(writer, output->u.s);
  64                 break;
  65         case LTTNG_INTERPRETER_TYPE_UNSIGNED_ENUM:
  66                 lttng_msgpack_write_signed_integer(writer, output->u.u);
  67                 break;
  68         default:
  69                 abort();
  70         }
  71
  72         lttng_msgpack_end_map(writer);
  73 }
  74
  75 static
  76 int64_t capture_sequence_element_signed(uint8_t *ptr,
  77                 const struct lttng_integer_type *type)
  78 {
  79         int64_t value;
  80         unsigned int size = type->size;
  81         bool byte_order_reversed = type->reverse_byte_order;
  82
  83         switch (size) {
  84         case 8:
  85                 value = *ptr;
  86                 break;
  87         case 16:
  88         {
  89                 int16_t tmp;
  90                 tmp = *(int16_t *) ptr;
  91                 if (byte_order_reversed)
  92                         tmp = bswap_16(tmp);
  93
  94                 value = tmp;
  95                 break;
  96         }
  97         case 32:
  98         {
  99                 int32_t tmp;
 100                 tmp = *(int32_t *) ptr;
 101                 if (byte_order_reversed)
 102                         tmp = bswap_32(tmp);
 103
 104                 value = tmp;
 105                 break;
 106         }
 107         case 64:
 108         {
 109                 int64_t tmp;
 110                 tmp = *(int64_t *) ptr;
 111                 if (byte_order_reversed)
 112                         tmp = bswap_64(tmp);
 113
 114                 value = tmp;
 115                 break;
 116         }
 117         default:
 118                 abort();
 119         }
 120
 121         return value;
 122 }
 123
 124 static
 125 uint64_t capture_sequence_element_unsigned(uint8_t *ptr,
 126                 const struct lttng_integer_type *type)
 127 {
 128         uint64_t value;
 129         unsigned int size = type->size;
 130         bool byte_order_reversed = type->reverse_byte_order;
 131
 132         switch (size) {
 133         case 8:
 134                 value = *ptr;
 135                 break;
 136         case 16:
 137         {
 138                 uint16_t tmp;
 139                 tmp = *(uint16_t *) ptr;
 140                 if (byte_order_reversed)
 141                         tmp = bswap_16(tmp);
 142
 143                 value = tmp;
 144                 break;
 145         }
 146         case 32:
 147         {
 148                 uint32_t tmp;
 149                 tmp = *(uint32_t *) ptr;
 150                 if (byte_order_reversed)
 151                         tmp = bswap_32(tmp);
 152
 153                 value = tmp;
 154                 break;
 155         }
 156         case 64:
 157         {
 158                 uint64_t tmp;
 159                 tmp = *(uint64_t *) ptr;
 160                 if (byte_order_reversed)
 161                         tmp = bswap_64(tmp);
 162
 163                 value = tmp;
 164                 break;
 165         }
 166         default:
 167                 abort();
 168         }
 169
 170         return value;
 171 }
 172
 173 static
 174 void capture_sequence(struct lttng_msgpack_writer *writer,
 175                 struct lttng_interpreter_output *output)
 176 {
 177         const struct lttng_integer_type *integer_type;
 178         const struct lttng_type *nested_type;
 179         uint8_t *ptr;
 180         bool signedness;
 181         int i;
 182
 183         lttng_msgpack_begin_array(writer, output->u.sequence.nr_elem);
 184
 185         ptr = (uint8_t *) output->u.sequence.ptr;
 186         nested_type = output->u.sequence.nested_type;
 187         switch (nested_type->atype) {
 188         case atype_integer:
 189                 integer_type = &nested_type->u.integer;
 190                 break;
 191         case atype_enum:
 192                 /* Treat enumeration as an integer. */
 193                 integer_type = &nested_type->u.enum_nestable.container_type->u.integer;
 194                 break;
 195         default:
 196                 /* Capture of array of non-integer are not supported. */
 197                 abort();
 198         }
 199         signedness = integer_type->signedness;
 200         for (i = 0; i < output->u.sequence.nr_elem; i++) {
 201                 if (signedness) {
 202                         lttng_msgpack_write_signed_integer(writer,
 203                                 capture_sequence_element_signed(ptr, integer_type));
 204                 } else {
 205                         lttng_msgpack_write_unsigned_integer(writer,
 206                                 capture_sequence_element_unsigned(ptr, integer_type));
 207                 }
 208
 209                 /*
 210                  * We assume that alignment is smaller or equal to the size.
 211                  * This currently holds true but if it changes in the future,
 212                  * we will want to change the pointer arithmetics below to
 213                  * take into account that the next element might be further
 214                  * away.
 215                  */
 216                 assert(integer_type->alignment <= integer_type->size);
 217
 218                 /* Size is in number of bits. */
 219                 ptr += (integer_type->size / CHAR_BIT) ;
 220         }
 221
 222         lttng_msgpack_end_array(writer);
 223 }
 224
 225 static
 226 void notification_init(struct lttng_event_notifier_notification *notif,
 227                 struct lttng_event_notifier *event_notifier)
 228 {
 229         struct lttng_msgpack_writer *writer = &notif->writer;
 230
 231         notif->event_notifier_token = event_notifier->user_token;
 232         notif->notification_fd = event_notifier->group->notification_fd;
 233         notif->has_captures = false;
 234
 235         if (event_notifier->num_captures > 0) {
 236                 lttng_msgpack_writer_init(writer, notif->capture_buf,
 237                                 CAPTURE_BUFFER_SIZE);
 238
 239                 lttng_msgpack_begin_array(writer, event_notifier->num_captures);
 240                 notif->has_captures = true;
 241         }
 242 }
 243
 244 static
 245 void notification_append_capture(
 246                 struct lttng_event_notifier_notification *notif,
 247                 struct lttng_interpreter_output *output)
 248 {
 249         struct lttng_msgpack_writer *writer = &notif->writer;
 250
 251         switch (output->type) {
 252         case LTTNG_INTERPRETER_TYPE_S64:
 253                 lttng_msgpack_write_signed_integer(writer, output->u.s);
 254                 break;
 255         case LTTNG_INTERPRETER_TYPE_U64:
 256                 lttng_msgpack_write_unsigned_integer(writer, output->u.u);
 257                 break;
 258         case LTTNG_INTERPRETER_TYPE_DOUBLE:
 259                 lttng_msgpack_write_double(writer, output->u.d);
 260                 break;
 261         case LTTNG_INTERPRETER_TYPE_STRING:
 262                 lttng_msgpack_write_str(writer, output->u.str.str);
 263                 break;
 264         case LTTNG_INTERPRETER_TYPE_SEQUENCE:
 265                 capture_sequence(writer, output);
 266                 break;
 267         case LTTNG_INTERPRETER_TYPE_SIGNED_ENUM:
 268         case LTTNG_INTERPRETER_TYPE_UNSIGNED_ENUM:
 269                 capture_enum(writer, output);
 270                 break;
 271         default:
 272                 abort();
 273         }
 274 }
 275
 276 static
 277 void notification_append_empty_capture(
 278                 struct lttng_event_notifier_notification *notif)
 279 {
 280         lttng_msgpack_write_nil(&notif->writer);
 281 }
 282
 283 static void record_error(struct lttng_event_notifier *event_notifier)
 284 {
 285         struct lttng_event_notifier_group *event_notifier_group =
 286                         event_notifier->group;
 287         struct lttng_counter *error_counter;
 288         size_t dimension_index[1];
 289         int ret;
 290
 291         error_counter = CMM_LOAD_SHARED(event_notifier_group->error_counter);
 292         /*
 293          * load-acquire paired with store-release orders creation of the
 294          * error counter and setting error_counter_len before the
 295          * error_counter is used.
 296          * Currently a full memory barrier is used, which could be
 297          * turned into acquire-release barriers.
 298          */
 299         cmm_smp_mb();
 300         /* This group may not have an error counter attached to it. */
 301         if (!error_counter)
 302                 return;
 303
 304         dimension_index[0] = event_notifier->error_counter_index;
 305         ret = event_notifier_group->error_counter->ops->counter_add(
 306                         error_counter->counter, dimension_index, 1);
 307         if (ret)
 308                 WARN_ON_ONCE(1);
 309 }
 310
 311 static
 312 void notification_send(struct lttng_event_notifier_notification *notif,
 313                 struct lttng_event_notifier *event_notifier)
 314 {
 315         ssize_t ret;
 316         size_t content_len;
 317         int iovec_count = 1;
 318         struct lttng_ust_event_notifier_notification ust_notif = {0};
 319         struct iovec iov[2];
 320
 321         assert(notif);
 322
 323         ust_notif.token = event_notifier->user_token;
 324
 325         /*
 326          * Prepare sending the notification from multiple buffers using an
 327          * array of `struct iovec`. The first buffer of the vector is
 328          * notification structure itself and is always present.
 329          */
 330         iov[0].iov_base = &ust_notif;
 331         iov[0].iov_len = sizeof(ust_notif);
 332
 333         if (notif->has_captures) {
 334                 /*
 335                  * If captures were requested, the second buffer of the array
 336                  * is the capture buffer.
 337                  */
 338                 assert(notif->writer.buffer);
 339                 content_len = notif->writer.write_pos - notif->writer.buffer;
 340
 341                 assert(content_len > 0 && content_len <= CAPTURE_BUFFER_SIZE);
 342
 343                 iov[1].iov_base = notif->capture_buf;
 344                 iov[1].iov_len = content_len;
 345
 346                 iovec_count++;
 347         } else {
 348                 content_len = 0;
 349         }
 350
 351         /*
 352          * Update the capture buffer size so that receiver of the buffer will
 353          * know how much to expect.
 354          */
 355         ust_notif.capture_buf_size = content_len;
 356
 357         /* Send all the buffers. */
 358         ret = patient_writev(notif->notification_fd, iov, iovec_count);
 359         if (ret == -1) {
 360                 if (errno == EAGAIN) {
 361                         record_error(event_notifier);
 362                         DBG("Cannot send event_notifier notification without blocking: %s",
 363                                 strerror(errno));
 364                 } else {
 365                         DBG("Error to sending event notifier notification: %s",
 366                                 strerror(errno));
 367                         abort();
 368                 }
 369         }
 370 }
 371
 372 void lttng_event_notifier_notification_send(
 373                 struct lttng_event_notifier *event_notifier,
 374                 const char *stack_data)
 375 {
 376         /*
 377          * This function is called from the probe, we must do dynamic
 378          * allocation in this context.
 379          */
 380         struct lttng_event_notifier_notification notif = {0};
 381
 382         notification_init(&notif, event_notifier);
 383
 384         if (caa_unlikely(!cds_list_empty(&event_notifier->capture_bytecode_runtime_head))) {
 385                 struct lttng_bytecode_runtime *capture_bc_runtime;
 386
 387                 /*
 388                  * Iterate over all the capture bytecodes. If the interpreter
 389                  * functions returns successfully, append the value of the
 390                  * `output` parameter to the capture buffer. If the interpreter
 391                  * fails, append an empty capture to the buffer.
 392                  */
 393                 cds_list_for_each_entry(capture_bc_runtime,
 394                                 &event_notifier->capture_bytecode_runtime_head, node) {
 395                         struct lttng_interpreter_output output;
 396
 397                         if (capture_bc_runtime->interpreter_funcs.capture(capture_bc_runtime,
 398                                         stack_data, &output) & LTTNG_INTERPRETER_RECORD_FLAG)
 399                                 notification_append_capture(&notif, &output);
 400                         else
 401                                 notification_append_empty_capture(&notif);
 402                 }
 403         }
 404
 405         /*
 406          * Send the notification (including the capture buffer) to the
 407          * sessiond.
 408          */
 409         notification_send(&notif, event_notifier);
 410 }