liblttng-ust/lttng-ust-comm.c

   1 /*
   2  * lttng-ust-comm.c
   3  *
   4  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
   5  * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; only
  10  * version 2.1 of the License.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #define _LGPL_SOURCE
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25 #include <sys/mman.h>
  26 #include <sys/stat.h>
  27 #include <sys/types.h>
  28 #include <sys/wait.h>
  29 #include <fcntl.h>
  30 #include <unistd.h>
  31 #include <errno.h>
  32 #include <pthread.h>
  33 #include <semaphore.h>
  34 #include <time.h>
  35 #include <assert.h>
  36 #include <signal.h>
  37 #include <urcu/uatomic.h>
  38 #include <urcu/futex.h>
  39 #include <urcu/compiler.h>
  40
  41 #include <lttng/ust-events.h>
  42 #include <lttng/ust-abi.h>
  43 #include <lttng/ust.h>
  44 #include <lttng/ust-error.h>
  45 #include <lttng/ust-ctl.h>
  46 #include <urcu/tls-compat.h>
  47 #include <ust-comm.h>
  48 #include <usterr-signal-safe.h>
  49 #include <helper.h>
  50 #include "tracepoint-internal.h"
  51 #include "lttng-tracer-core.h"
  52 #include "compat.h"
  53 #include "../libringbuffer/tlsfixup.h"
  54
  55 /*
  56  * Has lttng ust comm constructor been called ?
  57  */
  58 static int initialized;
  59
  60 /*
  61  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  62  * Held when handling a command, also held by fork() to deal with
  63  * removal of threads, and by exit path.
  64  */
  65
  66 /* Should the ust comm thread quit ? */
  67 static int lttng_ust_comm_should_quit;
  68
  69 /*
  70  * Wait for either of these before continuing to the main
  71  * program:
  72  * - the register_done message from sessiond daemon
  73  *   (will let the sessiond daemon enable sessions before main
  74  *   starts.)
  75  * - sessiond daemon is not reachable.
  76  * - timeout (ensuring applications are resilient to session
  77  *   daemon problems).
  78  */
  79 static sem_t constructor_wait;
  80 /*
  81  * Doing this for both the global and local sessiond.
  82  */
  83 static int sem_count = { 2 };
  84
  85 /*
  86  * Counting nesting within lttng-ust. Used to ensure that calling fork()
  87  * from liblttng-ust does not execute the pre/post fork handlers.
  88  */
  89 static DEFINE_URCU_TLS(int, lttng_ust_nest_count);
  90
  91 /*
  92  * Info about socket and associated listener thread.
  93  */
  94 struct sock_info {
  95         const char *name;
  96         pthread_t ust_listener; /* listener thread */
  97         int root_handle;
  98         int constructor_sem_posted;
  99         int allowed;
 100         int global;
 101         int thread_active;
 102
 103         char sock_path[PATH_MAX];
 104         int socket;
 105         int notify_socket;
 106
 107         char wait_shm_path[PATH_MAX];
 108         char *wait_shm_mmap;
 109 };
 110
 111 /* Socket from app (connect) to session daemon (listen) for communication */
 112 struct sock_info global_apps = {
 113         .name = "global",
 114         .global = 1,
 115
 116         .root_handle = -1,
 117         .allowed = 1,
 118         .thread_active = 0,
 119
 120         .sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
 121         .socket = -1,
 122         .notify_socket = -1,
 123
 124         .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 125 };
 126
 127 /* TODO: allow global_apps_sock_path override */
 128
 129 struct sock_info local_apps = {
 130         .name = "local",
 131         .global = 0,
 132         .root_handle = -1,
 133         .allowed = 0,   /* Check setuid bit first */
 134         .thread_active = 0,
 135
 136         .socket = -1,
 137         .notify_socket = -1,
 138 };
 139
 140 static int wait_poll_fallback;
 141
 142 static const char *cmd_name_mapping[] = {
 143         [ LTTNG_UST_RELEASE ] = "Release",
 144         [ LTTNG_UST_SESSION ] = "Create Session",
 145         [ LTTNG_UST_TRACER_VERSION ] = "Get Tracer Version",
 146
 147         [ LTTNG_UST_TRACEPOINT_LIST ] = "Create Tracepoint List",
 148         [ LTTNG_UST_WAIT_QUIESCENT ] = "Wait for Quiescent State",
 149         [ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
 150         [ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
 151
 152         /* Session FD commands */
 153         [ LTTNG_UST_CHANNEL ] = "Create Channel",
 154         [ LTTNG_UST_SESSION_START ] = "Start Session",
 155         [ LTTNG_UST_SESSION_STOP ] = "Stop Session",
 156
 157         /* Channel FD commands */
 158         [ LTTNG_UST_STREAM ] = "Create Stream",
 159         [ LTTNG_UST_EVENT ] = "Create Event",
 160
 161         /* Event and Channel FD commands */
 162         [ LTTNG_UST_CONTEXT ] = "Create Context",
 163         [ LTTNG_UST_FLUSH_BUFFER ] = "Flush Buffer",
 164
 165         /* Event, Channel and Session commands */
 166         [ LTTNG_UST_ENABLE ] = "Enable",
 167         [ LTTNG_UST_DISABLE ] = "Disable",
 168
 169         /* Tracepoint list commands */
 170         [ LTTNG_UST_TRACEPOINT_LIST_GET ] = "List Next Tracepoint",
 171         [ LTTNG_UST_TRACEPOINT_FIELD_LIST_GET ] = "List Next Tracepoint Field",
 172
 173         /* Event FD commands */
 174         [ LTTNG_UST_FILTER ] = "Create Filter",
 175 };
 176
 177 static const char *str_timeout;
 178 static int got_timeout_env;
 179
 180 extern void lttng_ring_buffer_client_overwrite_init(void);
 181 extern void lttng_ring_buffer_client_overwrite_rt_init(void);
 182 extern void lttng_ring_buffer_client_discard_init(void);
 183 extern void lttng_ring_buffer_client_discard_rt_init(void);
 184 extern void lttng_ring_buffer_metadata_client_init(void);
 185 extern void lttng_ring_buffer_client_overwrite_exit(void);
 186 extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
 187 extern void lttng_ring_buffer_client_discard_exit(void);
 188 extern void lttng_ring_buffer_client_discard_rt_exit(void);
 189 extern void lttng_ring_buffer_metadata_client_exit(void);
 190
 191 /*
 192  * Returns the HOME directory path. Caller MUST NOT free(3) the returned
 193  * pointer.
 194  */
 195 static
 196 const char *get_lttng_home_dir(void)
 197 {
 198        const char *val;
 199
 200        val = (const char *) getenv("LTTNG_HOME");
 201        if (val != NULL) {
 202                return val;
 203        }
 204        return (const char *) getenv("HOME");
 205 }
 206
 207 /*
 208  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 209  */
 210 static
 211 void lttng_fixup_nest_count_tls(void)
 212 {
 213         asm volatile ("" : : "m" (URCU_TLS(lttng_ust_nest_count)));
 214 }
 215
 216 int lttng_get_notify_socket(void *owner)
 217 {
 218         struct sock_info *info = owner;
 219
 220         return info->notify_socket;
 221 }
 222
 223 static
 224 void print_cmd(int cmd, int handle)
 225 {
 226         const char *cmd_name = "Unknown";
 227
 228         if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
 229                         && cmd_name_mapping[cmd]) {
 230                 cmd_name = cmd_name_mapping[cmd];
 231         }
 232         DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
 233                 cmd_name, cmd,
 234                 lttng_ust_obj_get_name(handle), handle);
 235 }
 236
 237 static
 238 int setup_local_apps(void)
 239 {
 240         const char *home_dir;
 241         uid_t uid;
 242
 243         uid = getuid();
 244         /*
 245          * Disallow per-user tracing for setuid binaries.
 246          */
 247         if (uid != geteuid()) {
 248                 assert(local_apps.allowed == 0);
 249                 return 0;
 250         }
 251         home_dir = get_lttng_home_dir();
 252         if (!home_dir) {
 253                 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
 254                 assert(local_apps.allowed == 0);
 255                 return -ENOENT;
 256         }
 257         local_apps.allowed = 1;
 258         snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
 259                 home_dir,
 260                 LTTNG_DEFAULT_HOME_RUNDIR,
 261                 LTTNG_UST_SOCK_FILENAME);
 262         snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
 263                 LTTNG_UST_WAIT_FILENAME,
 264                 uid);
 265         return 0;
 266 }
 267
 268 /*
 269  * Get notify_sock timeout, in ms.
 270  * -1: don't wait. 0: wait forever. >0: timeout, in ms.
 271  */
 272 static
 273 long get_timeout(void)
 274 {
 275         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 276
 277         if (!got_timeout_env) {
 278                 str_timeout = getenv("LTTNG_UST_REGISTER_TIMEOUT");
 279                 got_timeout_env = 1;
 280         }
 281         if (str_timeout)
 282                 constructor_delay_ms = strtol(str_timeout, NULL, 10);
 283         return constructor_delay_ms;
 284 }
 285
 286 static
 287 long get_notify_sock_timeout(void)
 288 {
 289         return get_timeout();
 290 }
 291
 292 /*
 293  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 294  */
 295 static
 296 int get_constructor_timeout(struct timespec *constructor_timeout)
 297 {
 298         long constructor_delay_ms;
 299         int ret;
 300
 301         constructor_delay_ms = get_timeout();
 302
 303         switch (constructor_delay_ms) {
 304         case -1:/* fall-through */
 305         case 0:
 306                 return constructor_delay_ms;
 307         default:
 308                 break;
 309         }
 310
 311         /*
 312          * If we are unable to find the current time, don't wait.
 313          */
 314         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 315         if (ret) {
 316                 return -1;
 317         }
 318         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 319         constructor_timeout->tv_nsec +=
 320                 (constructor_delay_ms % 1000UL) * 1000000UL;
 321         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 322                 constructor_timeout->tv_sec++;
 323                 constructor_timeout->tv_nsec -= 1000000000UL;
 324         }
 325         return 1;
 326 }
 327
 328 static
 329 int register_to_sessiond(int socket, enum ustctl_socket_type type)
 330 {
 331         return ustcomm_send_reg_msg(socket,
 332                 type,
 333                 CAA_BITS_PER_LONG,
 334                 lttng_alignof(uint8_t) * CHAR_BIT,
 335                 lttng_alignof(uint16_t) * CHAR_BIT,
 336                 lttng_alignof(uint32_t) * CHAR_BIT,
 337                 lttng_alignof(uint64_t) * CHAR_BIT,
 338                 lttng_alignof(unsigned long) * CHAR_BIT);
 339 }
 340
 341 static
 342 int send_reply(int sock, struct ustcomm_ust_reply *lur)
 343 {
 344         ssize_t len;
 345
 346         len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur));
 347         switch (len) {
 348         case sizeof(*lur):
 349                 DBG("message successfully sent");
 350                 return 0;
 351         default:
 352                 if (len == -ECONNRESET) {
 353                         DBG("remote end closed connection");
 354                         return 0;
 355                 }
 356                 if (len < 0)
 357                         return len;
 358                 DBG("incorrect message size: %zd", len);
 359                 return -EINVAL;
 360         }
 361 }
 362
 363 static
 364 int handle_register_done(struct sock_info *sock_info)
 365 {
 366         int ret;
 367
 368         if (sock_info->constructor_sem_posted)
 369                 return 0;
 370         sock_info->constructor_sem_posted = 1;
 371         if (uatomic_read(&sem_count) <= 0) {
 372                 return 0;
 373         }
 374         ret = uatomic_add_return(&sem_count, -1);
 375         if (ret == 0) {
 376                 ret = sem_post(&constructor_wait);
 377                 assert(!ret);
 378         }
 379         return 0;
 380 }
 381
 382 static
 383 int handle_message(struct sock_info *sock_info,
 384                 int sock, struct ustcomm_ust_msg *lum)
 385 {
 386         int ret = 0;
 387         const struct lttng_ust_objd_ops *ops;
 388         struct ustcomm_ust_reply lur;
 389         union ust_args args;
 390         ssize_t len;
 391
 392         ust_lock();
 393
 394         memset(&lur, 0, sizeof(lur));
 395
 396         if (lttng_ust_comm_should_quit) {
 397                 ret = -LTTNG_UST_ERR_EXITING;
 398                 goto end;
 399         }
 400
 401         ops = objd_ops(lum->handle);
 402         if (!ops) {
 403                 ret = -ENOENT;
 404                 goto end;
 405         }
 406
 407         switch (lum->cmd) {
 408         case LTTNG_UST_REGISTER_DONE:
 409                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 410                         ret = handle_register_done(sock_info);
 411                 else
 412                         ret = -EINVAL;
 413                 break;
 414         case LTTNG_UST_RELEASE:
 415                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 416                         ret = -EPERM;
 417                 else
 418                         ret = lttng_ust_objd_unref(lum->handle, 1);
 419                 break;
 420         case LTTNG_UST_FILTER:
 421         {
 422                 /* Receive filter data */
 423                 struct lttng_ust_filter_bytecode_node *bytecode;
 424
 425                 if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
 426                         ERR("Filter data size is too large: %u bytes",
 427                                 lum->u.filter.data_size);
 428                         ret = -EINVAL;
 429                         goto error;
 430                 }
 431
 432                 if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
 433                         ERR("Filter reloc offset %u is not within data",
 434                                 lum->u.filter.reloc_offset);
 435                         ret = -EINVAL;
 436                         goto error;
 437                 }
 438
 439                 bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
 440                 if (!bytecode) {
 441                         ret = -ENOMEM;
 442                         goto error;
 443                 }
 444                 len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
 445                                 lum->u.filter.data_size);
 446                 switch (len) {
 447                 case 0: /* orderly shutdown */
 448                         ret = 0;
 449                         free(bytecode);
 450                         goto error;
 451                 default:
 452                         if (len == lum->u.filter.data_size) {
 453                                 DBG("filter data received");
 454                                 break;
 455                         } else if (len < 0) {
 456                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 457                                 if (len == -ECONNRESET) {
 458                                         ERR("%s remote end closed connection", sock_info->name);
 459                                         ret = len;
 460                                         free(bytecode);
 461                                         goto error;
 462                                 }
 463                                 ret = len;
 464                                 free(bytecode);
 465                                 goto end;
 466                         } else {
 467                                 DBG("incorrect filter data message size: %zd", len);
 468                                 ret = -EINVAL;
 469                                 free(bytecode);
 470                                 goto end;
 471                         }
 472                 }
 473                 bytecode->bc.len = lum->u.filter.data_size;
 474                 bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
 475                 bytecode->bc.seqnum = lum->u.filter.seqnum;
 476                 if (ops->cmd) {
 477                         ret = ops->cmd(lum->handle, lum->cmd,
 478                                         (unsigned long) bytecode,
 479                                         &args, sock_info);
 480                         if (ret) {
 481                                 free(bytecode);
 482                         }
 483                         /* don't free bytecode if everything went fine. */
 484                 } else {
 485                         ret = -ENOSYS;
 486                         free(bytecode);
 487                 }
 488                 break;
 489         }
 490         case LTTNG_UST_CHANNEL:
 491         {
 492                 void *chan_data;
 493                 int wakeup_fd;
 494
 495                 len = ustcomm_recv_channel_from_sessiond(sock,
 496                                 &chan_data, lum->u.channel.len,
 497                                 &wakeup_fd);
 498                 switch (len) {
 499                 case 0: /* orderly shutdown */
 500                         ret = 0;
 501                         goto error;
 502                 default:
 503                         if (len == lum->u.channel.len) {
 504                                 DBG("channel data received");
 505                                 break;
 506                         } else if (len < 0) {
 507                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 508                                 if (len == -ECONNRESET) {
 509                                         ERR("%s remote end closed connection", sock_info->name);
 510                                         ret = len;
 511                                         goto error;
 512                                 }
 513                                 ret = len;
 514                                 goto end;
 515                         } else {
 516                                 DBG("incorrect channel data message size: %zd", len);
 517                                 ret = -EINVAL;
 518                                 goto end;
 519                         }
 520                 }
 521                 args.channel.chan_data = chan_data;
 522                 args.channel.wakeup_fd = wakeup_fd;
 523                 if (ops->cmd)
 524                         ret = ops->cmd(lum->handle, lum->cmd,
 525                                         (unsigned long) &lum->u,
 526                                         &args, sock_info);
 527                 else
 528                         ret = -ENOSYS;
 529                 break;
 530         }
 531         case LTTNG_UST_STREAM:
 532         {
 533                 /* Receive shm_fd, wakeup_fd */
 534                 ret = ustcomm_recv_stream_from_sessiond(sock,
 535                         &lum->u.stream.len,
 536                         &args.stream.shm_fd,
 537                         &args.stream.wakeup_fd);
 538                 if (ret) {
 539                         goto end;
 540                 }
 541                 if (ops->cmd)
 542                         ret = ops->cmd(lum->handle, lum->cmd,
 543                                         (unsigned long) &lum->u,
 544                                         &args, sock_info);
 545                 else
 546                         ret = -ENOSYS;
 547                 break;
 548         }
 549         default:
 550                 if (ops->cmd)
 551                         ret = ops->cmd(lum->handle, lum->cmd,
 552                                         (unsigned long) &lum->u,
 553                                         &args, sock_info);
 554                 else
 555                         ret = -ENOSYS;
 556                 break;
 557         }
 558
 559 end:
 560         lur.handle = lum->handle;
 561         lur.cmd = lum->cmd;
 562         lur.ret_val = ret;
 563         if (ret >= 0) {
 564                 lur.ret_code = LTTNG_UST_OK;
 565         } else {
 566                 /*
 567                  * Use -LTTNG_UST_ERR as wildcard for UST internal
 568                  * error that are not caused by the transport, except if
 569                  * we already have a more precise error message to
 570                  * report.
 571                  */
 572                 if (ret > -LTTNG_UST_ERR) {
 573                         /* Translate code to UST error. */
 574                         switch (ret) {
 575                         case -EEXIST:
 576                                 lur.ret_code = -LTTNG_UST_ERR_EXIST;
 577                                 break;
 578                         case -EINVAL:
 579                                 lur.ret_code = -LTTNG_UST_ERR_INVAL;
 580                                 break;
 581                         case -ENOENT:
 582                                 lur.ret_code = -LTTNG_UST_ERR_NOENT;
 583                                 break;
 584                         case -EPERM:
 585                                 lur.ret_code = -LTTNG_UST_ERR_PERM;
 586                                 break;
 587                         case -ENOSYS:
 588                                 lur.ret_code = -LTTNG_UST_ERR_NOSYS;
 589                                 break;
 590                         default:
 591                                 lur.ret_code = -LTTNG_UST_ERR;
 592                                 break;
 593                         }
 594                 } else {
 595                         lur.ret_code = ret;
 596                 }
 597         }
 598         if (ret >= 0) {
 599                 switch (lum->cmd) {
 600                 case LTTNG_UST_TRACER_VERSION:
 601                         lur.u.version = lum->u.version;
 602                         break;
 603                 case LTTNG_UST_TRACEPOINT_LIST_GET:
 604                         memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
 605                         break;
 606                 }
 607         }
 608         DBG("Return value: %d", lur.ret_val);
 609         ret = send_reply(sock, &lur);
 610         if (ret < 0) {
 611                 DBG("error sending reply");
 612                 goto error;
 613         }
 614
 615         /*
 616          * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
 617          * after the reply.
 618          */
 619         if (lur.ret_code == LTTNG_UST_OK) {
 620                 switch (lum->cmd) {
 621                 case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
 622                         len = ustcomm_send_unix_sock(sock,
 623                                 &args.field_list.entry,
 624                                 sizeof(args.field_list.entry));
 625                         if (len < 0) {
 626                                 ret = len;
 627                                 goto error;
 628                         }
 629                         if (len != sizeof(args.field_list.entry)) {
 630                                 ret = -EINVAL;
 631                                 goto error;
 632                         }
 633                 }
 634         }
 635
 636 error:
 637         ust_unlock();
 638         return ret;
 639 }
 640
 641 static
 642 void cleanup_sock_info(struct sock_info *sock_info, int exiting)
 643 {
 644         int ret;
 645
 646         if (sock_info->root_handle != -1) {
 647                 ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
 648                 if (ret) {
 649                         ERR("Error unref root handle");
 650                 }
 651                 sock_info->root_handle = -1;
 652         }
 653         sock_info->constructor_sem_posted = 0;
 654
 655         /*
 656          * wait_shm_mmap, socket and notify socket are used by listener
 657          * threads outside of the ust lock, so we cannot tear them down
 658          * ourselves, because we cannot join on these threads. Leave
 659          * responsibility of cleaning up these resources to the OS
 660          * process exit.
 661          */
 662         if (exiting)
 663                 return;
 664
 665         if (sock_info->socket != -1) {
 666                 ret = ustcomm_close_unix_sock(sock_info->socket);
 667                 if (ret) {
 668                         ERR("Error closing ust cmd socket");
 669                 }
 670                 sock_info->socket = -1;
 671         }
 672         if (sock_info->notify_socket != -1) {
 673                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 674                 if (ret) {
 675                         ERR("Error closing ust notify socket");
 676                 }
 677                 sock_info->notify_socket = -1;
 678         }
 679         if (sock_info->wait_shm_mmap) {
 680                 ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
 681                 if (ret) {
 682                         ERR("Error unmapping wait shm");
 683                 }
 684                 sock_info->wait_shm_mmap = NULL;
 685         }
 686 }
 687
 688 /*
 689  * Using fork to set umask in the child process (not multi-thread safe).
 690  * We deal with the shm_open vs ftruncate race (happening when the
 691  * sessiond owns the shm and does not let everybody modify it, to ensure
 692  * safety against shm_unlink) by simply letting the mmap fail and
 693  * retrying after a few seconds.
 694  * For global shm, everybody has rw access to it until the sessiond
 695  * starts.
 696  */
 697 static
 698 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 699 {
 700         int wait_shm_fd, ret;
 701         pid_t pid;
 702
 703         /*
 704          * Try to open read-only.
 705          */
 706         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 707         if (wait_shm_fd >= 0) {
 708                 int32_t tmp_read;
 709                 ssize_t len;
 710                 size_t bytes_read = 0;
 711
 712                 /*
 713                  * Try to read the fd. If unable to do so, try opening
 714                  * it in write mode.
 715                  */
 716                 do {
 717                         len = read(wait_shm_fd,
 718                                 &((char *) &tmp_read)[bytes_read],
 719                                 sizeof(tmp_read) - bytes_read);
 720                         if (len > 0) {
 721                                 bytes_read += len;
 722                         }
 723                 } while ((len < 0 && errno == EINTR)
 724                         || (len > 0 && bytes_read < sizeof(tmp_read)));
 725                 if (bytes_read != sizeof(tmp_read)) {
 726                         ret = close(wait_shm_fd);
 727                         if (ret) {
 728                                 ERR("close wait_shm_fd");
 729                         }
 730                         goto open_write;
 731                 }
 732                 goto end;
 733         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 734                 /*
 735                  * Real-only open did not work, and it's not because the
 736                  * entry was not present. It's a failure that prohibits
 737                  * using shm.
 738                  */
 739                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 740                 goto end;
 741         }
 742
 743 open_write:
 744         /*
 745          * If the open failed because the file did not exist, or because
 746          * the file was not truncated yet, try creating it ourself.
 747          */
 748         URCU_TLS(lttng_ust_nest_count)++;
 749         pid = fork();
 750         URCU_TLS(lttng_ust_nest_count)--;
 751         if (pid > 0) {
 752                 int status;
 753
 754                 /*
 755                  * Parent: wait for child to return, in which case the
 756                  * shared memory map will have been created.
 757                  */
 758                 pid = wait(&status);
 759                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 760                         wait_shm_fd = -1;
 761                         goto end;
 762                 }
 763                 /*
 764                  * Try to open read-only again after creation.
 765                  */
 766                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 767                 if (wait_shm_fd < 0) {
 768                         /*
 769                          * Real-only open did not work. It's a failure
 770                          * that prohibits using shm.
 771                          */
 772                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 773                         goto end;
 774                 }
 775                 goto end;
 776         } else if (pid == 0) {
 777                 int create_mode;
 778
 779                 /* Child */
 780                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
 781                 if (sock_info->global)
 782                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
 783                 /*
 784                  * We're alone in a child process, so we can modify the
 785                  * process-wide umask.
 786                  */
 787                 umask(~create_mode);
 788                 /*
 789                  * Try creating shm (or get rw access).
 790                  * We don't do an exclusive open, because we allow other
 791                  * processes to create+ftruncate it concurrently.
 792                  */
 793                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
 794                                 O_RDWR | O_CREAT, create_mode);
 795                 if (wait_shm_fd >= 0) {
 796                         ret = ftruncate(wait_shm_fd, mmap_size);
 797                         if (ret) {
 798                                 PERROR("ftruncate");
 799                                 _exit(EXIT_FAILURE);
 800                         }
 801                         _exit(EXIT_SUCCESS);
 802                 }
 803                 /*
 804                  * For local shm, we need to have rw access to accept
 805                  * opening it: this means the local sessiond will be
 806                  * able to wake us up. For global shm, we open it even
 807                  * if rw access is not granted, because the root.root
 808                  * sessiond will be able to override all rights and wake
 809                  * us up.
 810                  */
 811                 if (!sock_info->global && errno != EACCES) {
 812                         ERR("Error opening shm %s", sock_info->wait_shm_path);
 813                         _exit(EXIT_FAILURE);
 814                 }
 815                 /*
 816                  * The shm exists, but we cannot open it RW. Report
 817                  * success.
 818                  */
 819                 _exit(EXIT_SUCCESS);
 820         } else {
 821                 return -1;
 822         }
 823 end:
 824         if (wait_shm_fd >= 0 && !sock_info->global) {
 825                 struct stat statbuf;
 826
 827                 /*
 828                  * Ensure that our user is the owner of the shm file for
 829                  * local shm. If we do not own the file, it means our
 830                  * sessiond will not have access to wake us up (there is
 831                  * probably a rogue process trying to fake our
 832                  * sessiond). Fallback to polling method in this case.
 833                  */
 834                 ret = fstat(wait_shm_fd, &statbuf);
 835                 if (ret) {
 836                         PERROR("fstat");
 837                         goto error_close;
 838                 }
 839                 if (statbuf.st_uid != getuid())
 840                         goto error_close;
 841         }
 842         return wait_shm_fd;
 843
 844 error_close:
 845         ret = close(wait_shm_fd);
 846         if (ret) {
 847                 PERROR("Error closing fd");
 848         }
 849         return -1;
 850 }
 851
 852 static
 853 char *get_map_shm(struct sock_info *sock_info)
 854 {
 855         size_t mmap_size = sysconf(_SC_PAGE_SIZE);
 856         int wait_shm_fd, ret;
 857         char *wait_shm_mmap;
 858
 859         wait_shm_fd = get_wait_shm(sock_info, mmap_size);
 860         if (wait_shm_fd < 0) {
 861                 goto error;
 862         }
 863         wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
 864                   MAP_SHARED, wait_shm_fd, 0);
 865         /* close shm fd immediately after taking the mmap reference */
 866         ret = close(wait_shm_fd);
 867         if (ret) {
 868                 PERROR("Error closing fd");
 869         }
 870         if (wait_shm_mmap == MAP_FAILED) {
 871                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
 872                 goto error;
 873         }
 874         return wait_shm_mmap;
 875
 876 error:
 877         return NULL;
 878 }
 879
 880 static
 881 void wait_for_sessiond(struct sock_info *sock_info)
 882 {
 883         int ret;
 884
 885         ust_lock();
 886         if (lttng_ust_comm_should_quit) {
 887                 goto quit;
 888         }
 889         if (wait_poll_fallback) {
 890                 goto error;
 891         }
 892         if (!sock_info->wait_shm_mmap) {
 893                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
 894                 if (!sock_info->wait_shm_mmap)
 895                         goto error;
 896         }
 897         ust_unlock();
 898
 899         DBG("Waiting for %s apps sessiond", sock_info->name);
 900         /* Wait for futex wakeup */
 901         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
 902                 ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
 903                         FUTEX_WAIT, 0, NULL, NULL, 0);
 904                 if (ret < 0) {
 905                         if (errno == EFAULT) {
 906                                 wait_poll_fallback = 1;
 907                                 DBG(
 908 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 909 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 910 "Please upgrade your kernel "
 911 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 912 "mainline). LTTng-UST will use polling mode fallback.");
 913                                 if (ust_debug())
 914                                         PERROR("futex");
 915                         }
 916                 }
 917         }
 918         return;
 919
 920 quit:
 921         ust_unlock();
 922         return;
 923
 924 error:
 925         ust_unlock();
 926         return;
 927 }
 928
 929 /*
 930  * This thread does not allocate any resource, except within
 931  * handle_message, within mutex protection. This mutex protects against
 932  * fork and exit.
 933  * The other moment it allocates resources is at socket connection, which
 934  * is also protected by the mutex.
 935  */
 936 static
 937 void *ust_listener_thread(void *arg)
 938 {
 939         struct sock_info *sock_info = arg;
 940         int sock, ret, prev_connect_failed = 0, has_waited = 0;
 941         long timeout;
 942
 943         /* Restart trying to connect to the session daemon */
 944 restart:
 945         if (prev_connect_failed) {
 946                 /* Wait for sessiond availability with pipe */
 947                 wait_for_sessiond(sock_info);
 948                 if (has_waited) {
 949                         has_waited = 0;
 950                         /*
 951                          * Sleep for 5 seconds before retrying after a
 952                          * sequence of failure / wait / failure. This
 953                          * deals with a killed or broken session daemon.
 954                          */
 955                         sleep(5);
 956                 }
 957                 has_waited = 1;
 958                 prev_connect_failed = 0;
 959         }
 960
 961         if (sock_info->socket != -1) {
 962                 ret = ustcomm_close_unix_sock(sock_info->socket);
 963                 if (ret) {
 964                         ERR("Error closing %s ust cmd socket",
 965                                 sock_info->name);
 966                 }
 967                 sock_info->socket = -1;
 968         }
 969         if (sock_info->notify_socket != -1) {
 970                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 971                 if (ret) {
 972                         ERR("Error closing %s ust notify socket",
 973                                 sock_info->name);
 974                 }
 975                 sock_info->notify_socket = -1;
 976         }
 977
 978         /*
 979          * Register. We need to perform both connect and sending
 980          * registration message before doing the next connect otherwise
 981          * we may reach unix socket connect queue max limits and block
 982          * on the 2nd connect while the session daemon is awaiting the
 983          * first connect registration message.
 984          */
 985         /* Connect cmd socket */
 986         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
 987         if (ret < 0) {
 988                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
 989                 prev_connect_failed = 1;
 990
 991                 ust_lock();
 992
 993                 if (lttng_ust_comm_should_quit) {
 994                         goto quit;
 995                 }
 996
 997                 /*
 998                  * If we cannot find the sessiond daemon, don't delay
 999                  * constructor execution.
1000                  */
1001                 ret = handle_register_done(sock_info);
1002                 assert(!ret);
1003                 ust_unlock();
1004                 goto restart;
1005         }
1006         sock_info->socket = ret;
1007
1008         ust_lock();
1009
1010         if (lttng_ust_comm_should_quit) {
1011                 goto quit;
1012         }
1013
1014         /*
1015          * Create only one root handle per listener thread for the whole
1016          * process lifetime, so we ensure we get ID which is statically
1017          * assigned to the root handle.
1018          */
1019         if (sock_info->root_handle == -1) {
1020                 ret = lttng_abi_create_root_handle();
1021                 if (ret < 0) {
1022                         ERR("Error creating root handle");
1023                         goto quit;
1024                 }
1025                 sock_info->root_handle = ret;
1026         }
1027
1028         ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
1029         if (ret < 0) {
1030                 ERR("Error registering to %s ust cmd socket",
1031                         sock_info->name);
1032                 prev_connect_failed = 1;
1033                 /*
1034                  * If we cannot register to the sessiond daemon, don't
1035                  * delay constructor execution.
1036                  */
1037                 ret = handle_register_done(sock_info);
1038                 assert(!ret);
1039                 ust_unlock();
1040                 goto restart;
1041         }
1042
1043         ust_unlock();
1044
1045         /* Connect notify socket */
1046         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
1047         if (ret < 0) {
1048                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1049                 prev_connect_failed = 1;
1050
1051                 ust_lock();
1052
1053                 if (lttng_ust_comm_should_quit) {
1054                         goto quit;
1055                 }
1056
1057                 /*
1058                  * If we cannot find the sessiond daemon, don't delay
1059                  * constructor execution.
1060                  */
1061                 ret = handle_register_done(sock_info);
1062                 assert(!ret);
1063                 ust_unlock();
1064                 goto restart;
1065         }
1066         sock_info->notify_socket = ret;
1067
1068         timeout = get_notify_sock_timeout();
1069         if (timeout >= 0) {
1070                 /*
1071                  * Give at least 10ms to sessiond to reply to
1072                  * notifications.
1073                  */
1074                 if (timeout < 10)
1075                         timeout = 10;
1076                 ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
1077                                 timeout);
1078                 if (ret < 0) {
1079                         WARN("Error setting socket receive timeout");
1080                 }
1081                 ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
1082                                 timeout);
1083                 if (ret < 0) {
1084                         WARN("Error setting socket send timeout");
1085                 }
1086         } else if (timeout < -1) {
1087                 WARN("Unsupported timeout value %ld", timeout);
1088         }
1089
1090         ust_lock();
1091
1092         if (lttng_ust_comm_should_quit) {
1093                 goto quit;
1094         }
1095
1096         ret = register_to_sessiond(sock_info->notify_socket,
1097                         USTCTL_SOCKET_NOTIFY);
1098         if (ret < 0) {
1099                 ERR("Error registering to %s ust notify socket",
1100                         sock_info->name);
1101                 prev_connect_failed = 1;
1102                 /*
1103                  * If we cannot register to the sessiond daemon, don't
1104                  * delay constructor execution.
1105                  */
1106                 ret = handle_register_done(sock_info);
1107                 assert(!ret);
1108                 ust_unlock();
1109                 goto restart;
1110         }
1111         sock = sock_info->socket;
1112
1113         ust_unlock();
1114
1115         for (;;) {
1116                 ssize_t len;
1117                 struct ustcomm_ust_msg lum;
1118
1119                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
1120                 switch (len) {
1121                 case 0: /* orderly shutdown */
1122                         DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
1123                         ust_lock();
1124                         if (lttng_ust_comm_should_quit) {
1125                                 goto quit;
1126                         }
1127                         /*
1128                          * Either sessiond has shutdown or refused us by closing the socket.
1129                          * In either case, we don't want to delay construction execution,
1130                          * and we need to wait before retry.
1131                          */
1132                         prev_connect_failed = 1;
1133                         /*
1134                          * If we cannot register to the sessiond daemon, don't
1135                          * delay constructor execution.
1136                          */
1137                         ret = handle_register_done(sock_info);
1138                         assert(!ret);
1139                         ust_unlock();
1140                         goto end;
1141                 case sizeof(lum):
1142                         print_cmd(lum.cmd, lum.handle);
1143                         ret = handle_message(sock_info, sock, &lum);
1144                         if (ret) {
1145                                 ERR("Error handling message for %s socket", sock_info->name);
1146                         }
1147                         continue;
1148                 default:
1149                         if (len < 0) {
1150                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
1151                         } else {
1152                                 DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
1153                         }
1154                         if (len == -ECONNRESET) {
1155                                 DBG("%s remote end closed connection", sock_info->name);
1156                                 goto end;
1157                         }
1158                         goto end;
1159                 }
1160
1161         }
1162 end:
1163         ust_lock();
1164         if (lttng_ust_comm_should_quit) {
1165                 goto quit;
1166         }
1167         /* Cleanup socket handles before trying to reconnect */
1168         lttng_ust_objd_table_owner_cleanup(sock_info);
1169         ust_unlock();
1170         goto restart;   /* try to reconnect */
1171
1172 quit:
1173         sock_info->thread_active = 0;
1174         ust_unlock();
1175         return NULL;
1176 }
1177
1178 /*
1179  * sessiond monitoring thread: monitor presence of global and per-user
1180  * sessiond by polling the application common named pipe.
1181  */
1182 void __attribute__((constructor)) lttng_ust_init(void)
1183 {
1184         struct timespec constructor_timeout;
1185         sigset_t sig_all_blocked, orig_parent_mask;
1186         pthread_attr_t thread_attr;
1187         int timeout_mode;
1188         int ret;
1189
1190         if (uatomic_xchg(&initialized, 1) == 1)
1191                 return;
1192
1193         /*
1194          * Fixup interdependency between TLS fixup mutex (which happens
1195          * to be the dynamic linker mutex) and ust_lock, taken within
1196          * the ust lock.
1197          */
1198         lttng_fixup_ringbuffer_tls();
1199         lttng_fixup_vtid_tls();
1200         lttng_fixup_nest_count_tls();
1201         lttng_fixup_procname_tls();
1202
1203         /*
1204          * We want precise control over the order in which we construct
1205          * our sub-libraries vs starting to receive commands from
1206          * sessiond (otherwise leading to errors when trying to create
1207          * sessiond before the init functions are completed).
1208          */
1209         init_usterr();
1210         init_tracepoint();
1211         lttng_ring_buffer_metadata_client_init();
1212         lttng_ring_buffer_client_overwrite_init();
1213         lttng_ring_buffer_client_overwrite_rt_init();
1214         lttng_ring_buffer_client_discard_init();
1215         lttng_ring_buffer_client_discard_rt_init();
1216         lttng_context_init();
1217
1218         timeout_mode = get_constructor_timeout(&constructor_timeout);
1219
1220         ret = sem_init(&constructor_wait, 0, 0);
1221         assert(!ret);
1222
1223         ret = setup_local_apps();
1224         if (ret) {
1225                 DBG("local apps setup returned %d", ret);
1226         }
1227
1228         /* A new thread created by pthread_create inherits the signal mask
1229          * from the parent. To avoid any signal being received by the
1230          * listener thread, we block all signals temporarily in the parent,
1231          * while we create the listener thread.
1232          */
1233         sigfillset(&sig_all_blocked);
1234         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
1235         if (ret) {
1236                 ERR("pthread_sigmask: %s", strerror(ret));
1237         }
1238
1239         ret = pthread_attr_init(&thread_attr);
1240         if (ret) {
1241                 ERR("pthread_attr_init: %s", strerror(ret));
1242         }
1243         ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
1244         if (ret) {
1245                 ERR("pthread_attr_setdetachstate: %s", strerror(ret));
1246         }
1247
1248         ust_lock();
1249         ret = pthread_create(&global_apps.ust_listener, &thread_attr,
1250                         ust_listener_thread, &global_apps);
1251         if (ret) {
1252                 ERR("pthread_create global: %s", strerror(ret));
1253         }
1254         global_apps.thread_active = 1;
1255         ust_unlock();
1256
1257         if (local_apps.allowed) {
1258                 ust_lock();
1259                 ret = pthread_create(&local_apps.ust_listener, &thread_attr,
1260                                 ust_listener_thread, &local_apps);
1261                 if (ret) {
1262                         ERR("pthread_create local: %s", strerror(ret));
1263                 }
1264                 local_apps.thread_active = 1;
1265                 ust_unlock();
1266         } else {
1267                 handle_register_done(&local_apps);
1268         }
1269         ret = pthread_attr_destroy(&thread_attr);
1270         if (ret) {
1271                 ERR("pthread_attr_destroy: %s", strerror(ret));
1272         }
1273
1274         /* Restore original signal mask in parent */
1275         ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
1276         if (ret) {
1277                 ERR("pthread_sigmask: %s", strerror(ret));
1278         }
1279
1280         switch (timeout_mode) {
1281         case 1: /* timeout wait */
1282                 do {
1283                         ret = sem_timedwait(&constructor_wait,
1284                                         &constructor_timeout);
1285                 } while (ret < 0 && errno == EINTR);
1286                 if (ret < 0 && errno == ETIMEDOUT) {
1287                         ERR("Timed out waiting for lttng-sessiond");
1288                 } else {
1289                         assert(!ret);
1290                 }
1291                 break;
1292         case -1:/* wait forever */
1293                 do {
1294                         ret = sem_wait(&constructor_wait);
1295                 } while (ret < 0 && errno == EINTR);
1296                 assert(!ret);
1297                 break;
1298         case 0: /* no timeout */
1299                 break;
1300         }
1301 }
1302
1303 static
1304 void lttng_ust_cleanup(int exiting)
1305 {
1306         cleanup_sock_info(&global_apps, exiting);
1307         if (local_apps.allowed) {
1308                 cleanup_sock_info(&local_apps, exiting);
1309         }
1310         /*
1311          * The teardown in this function all affect data structures
1312          * accessed under the UST lock by the listener thread. This
1313          * lock, along with the lttng_ust_comm_should_quit flag, ensure
1314          * that none of these threads are accessing this data at this
1315          * point.
1316          */
1317         lttng_ust_abi_exit();
1318         lttng_ust_events_exit();
1319         lttng_context_exit();
1320         lttng_ring_buffer_client_discard_rt_exit();
1321         lttng_ring_buffer_client_discard_exit();
1322         lttng_ring_buffer_client_overwrite_rt_exit();
1323         lttng_ring_buffer_client_overwrite_exit();
1324         lttng_ring_buffer_metadata_client_exit();
1325         exit_tracepoint();
1326         if (!exiting) {
1327                 /* Reinitialize values for fork */
1328                 sem_count = 2;
1329                 lttng_ust_comm_should_quit = 0;
1330                 initialized = 0;
1331         }
1332 }
1333
1334 void __attribute__((destructor)) lttng_ust_exit(void)
1335 {
1336         int ret;
1337
1338         /*
1339          * Using pthread_cancel here because:
1340          * A) we don't want to hang application teardown.
1341          * B) the thread is not allocating any resource.
1342          */
1343
1344         /*
1345          * Require the communication thread to quit. Synchronize with
1346          * mutexes to ensure it is not in a mutex critical section when
1347          * pthread_cancel is later called.
1348          */
1349         ust_lock();
1350         lttng_ust_comm_should_quit = 1;
1351
1352         /* cancel threads */
1353         if (global_apps.thread_active) {
1354                 ret = pthread_cancel(global_apps.ust_listener);
1355                 if (ret) {
1356                         ERR("Error cancelling global ust listener thread: %s",
1357                                 strerror(ret));
1358                 } else {
1359                         global_apps.thread_active = 0;
1360                 }
1361         }
1362         if (local_apps.thread_active) {
1363                 ret = pthread_cancel(local_apps.ust_listener);
1364                 if (ret) {
1365                         ERR("Error cancelling local ust listener thread: %s",
1366                                 strerror(ret));
1367                 } else {
1368                         local_apps.thread_active = 0;
1369                 }
1370         }
1371         ust_unlock();
1372
1373         /*
1374          * Do NOT join threads: use of sys_futex makes it impossible to
1375          * join the threads without using async-cancel, but async-cancel
1376          * is delivered by a signal, which could hit the target thread
1377          * anywhere in its code path, including while the ust_lock() is
1378          * held, causing a deadlock for the other thread. Let the OS
1379          * cleanup the threads if there are stalled in a syscall.
1380          */
1381         lttng_ust_cleanup(1);
1382 }
1383
1384 /*
1385  * We exclude the worker threads across fork and clone (except
1386  * CLONE_VM), because these system calls only keep the forking thread
1387  * running in the child.  Therefore, we don't want to call fork or clone
1388  * in the middle of an tracepoint or ust tracing state modification.
1389  * Holding this mutex protects these structures across fork and clone.
1390  */
1391 void ust_before_fork(sigset_t *save_sigset)
1392 {
1393         /*
1394          * Disable signals. This is to avoid that the child intervenes
1395          * before it is properly setup for tracing. It is safer to
1396          * disable all signals, because then we know we are not breaking
1397          * anything by restoring the original mask.
1398          */
1399         sigset_t all_sigs;
1400         int ret;
1401
1402         if (URCU_TLS(lttng_ust_nest_count))
1403                 return;
1404         /* Disable signals */
1405         sigfillset(&all_sigs);
1406         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
1407         if (ret == -1) {
1408                 PERROR("sigprocmask");
1409         }
1410         ust_lock();
1411         rcu_bp_before_fork();
1412 }
1413
1414 static void ust_after_fork_common(sigset_t *restore_sigset)
1415 {
1416         int ret;
1417
1418         DBG("process %d", getpid());
1419         ust_unlock();
1420         /* Restore signals */
1421         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
1422         if (ret == -1) {
1423                 PERROR("sigprocmask");
1424         }
1425 }
1426
1427 void ust_after_fork_parent(sigset_t *restore_sigset)
1428 {
1429         if (URCU_TLS(lttng_ust_nest_count))
1430                 return;
1431         DBG("process %d", getpid());
1432         rcu_bp_after_fork_parent();
1433         /* Release mutexes and reenable signals */
1434         ust_after_fork_common(restore_sigset);
1435 }
1436
1437 /*
1438  * After fork, in the child, we need to cleanup all the leftover state,
1439  * except the worker thread which already magically disappeared thanks
1440  * to the weird Linux fork semantics. After tyding up, we call
1441  * lttng_ust_init() again to start over as a new PID.
1442  *
1443  * This is meant for forks() that have tracing in the child between the
1444  * fork and following exec call (if there is any).
1445  */
1446 void ust_after_fork_child(sigset_t *restore_sigset)
1447 {
1448         if (URCU_TLS(lttng_ust_nest_count))
1449                 return;
1450         DBG("process %d", getpid());
1451         /* Release urcu mutexes */
1452         rcu_bp_after_fork_child();
1453         lttng_ust_cleanup(0);
1454         lttng_context_vtid_reset();
1455         /* Release mutexes and reenable signals */
1456         ust_after_fork_common(restore_sigset);
1457         lttng_ust_init();
1458 }