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 #define _GNU_SOURCE
  24 #include <sys/types.h>
  25 #include <sys/socket.h>
  26 #include <sys/mman.h>
  27 #include <sys/stat.h>
  28 #include <sys/types.h>
  29 #include <sys/wait.h>
  30 #include <fcntl.h>
  31 #include <unistd.h>
  32 #include <errno.h>
  33 #include <pthread.h>
  34 #include <semaphore.h>
  35 #include <time.h>
  36 #include <assert.h>
  37 #include <signal.h>
  38 #include <urcu/uatomic.h>
  39 #include <urcu/futex.h>
  40 #include <urcu/compiler.h>
  41
  42 #include <lttng/ust-events.h>
  43 #include <lttng/ust-abi.h>
  44 #include <lttng/ust.h>
  45 #include <lttng/ust-error.h>
  46 #include <lttng/ust-ctl.h>
  47 #include <urcu/tls-compat.h>
  48 #include <ust-comm.h>
  49 #include <usterr-signal-safe.h>
  50 #include <helper.h>
  51 #include "tracepoint-internal.h"
  52 #include "lttng-tracer-core.h"
  53 #include "compat.h"
  54 #include "../libringbuffer/tlsfixup.h"
  55 #include "lttng-ust-statedump.h"
  56 #include "clock.h"
  57 #include "../libringbuffer/getcpu.h"
  58 #include "getenv.h"
  59
  60 /*
  61  * Has lttng ust comm constructor been called ?
  62  */
  63 static int initialized;
  64
  65 /*
  66  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  67  * Held when handling a command, also held by fork() to deal with
  68  * removal of threads, and by exit path.
  69  *
  70  * The UST lock is the centralized mutex across UST tracing control and
  71  * probe registration.
  72  *
  73  * ust_exit_mutex must never nest in ust_mutex.
  74  *
  75  * ust_fork_mutex must never nest in ust_mutex.
  76  *
  77  * ust_mutex_nest is a per-thread nesting counter, allowing the perf
  78  * counter lazy initialization called by events within the statedump,
  79  * which traces while the ust_mutex is held.
  80  *
  81  * ust_lock nests within the dynamic loader lock (within glibc) because
  82  * it is taken within the library constructor.
  83  */
  84 static pthread_mutex_t ust_mutex = PTHREAD_MUTEX_INITIALIZER;
  85
  86 /* Allow nesting the ust_mutex within the same thread. */
  87 static DEFINE_URCU_TLS(int, ust_mutex_nest);
  88
  89 /*
  90  * ust_exit_mutex protects thread_active variable wrt thread exit. It
  91  * cannot be done by ust_mutex because pthread_cancel(), which takes an
  92  * internal libc lock, cannot nest within ust_mutex.
  93  *
  94  * It never nests within a ust_mutex.
  95  */
  96 static pthread_mutex_t ust_exit_mutex = PTHREAD_MUTEX_INITIALIZER;
  97
  98 /*
  99  * ust_fork_mutex protects base address statedump tracing against forks. It
 100  * prevents the dynamic loader lock to be taken (by base address statedump
 101  * tracing) while a fork is happening, thus preventing deadlock issues with
 102  * the dynamic loader lock.
 103  */
 104 static pthread_mutex_t ust_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
 105
 106 /* Should the ust comm thread quit ? */
 107 static int lttng_ust_comm_should_quit;
 108
 109 /*
 110  * Return 0 on success, -1 if should quit.
 111  * The lock is taken in both cases.
 112  * Signal-safe.
 113  */
 114 int ust_lock(void)
 115 {
 116         sigset_t sig_all_blocked, orig_mask;
 117         int ret, oldstate;
 118
 119         ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
 120         if (ret) {
 121                 ERR("pthread_setcancelstate: %s", strerror(ret));
 122         }
 123         if (oldstate != PTHREAD_CANCEL_ENABLE) {
 124                 ERR("pthread_setcancelstate: unexpected oldstate");
 125         }
 126         sigfillset(&sig_all_blocked);
 127         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 128         if (ret) {
 129                 ERR("pthread_sigmask: %s", strerror(ret));
 130         }
 131         if (!URCU_TLS(ust_mutex_nest)++)
 132                 pthread_mutex_lock(&ust_mutex);
 133         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 134         if (ret) {
 135                 ERR("pthread_sigmask: %s", strerror(ret));
 136         }
 137         if (lttng_ust_comm_should_quit) {
 138                 return -1;
 139         } else {
 140                 return 0;
 141         }
 142 }
 143
 144 /*
 145  * ust_lock_nocheck() can be used in constructors/destructors, because
 146  * they are already nested within the dynamic loader lock, and therefore
 147  * have exclusive access against execution of liblttng-ust destructor.
 148  * Signal-safe.
 149  */
 150 void ust_lock_nocheck(void)
 151 {
 152         sigset_t sig_all_blocked, orig_mask;
 153         int ret, oldstate;
 154
 155         ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
 156         if (ret) {
 157                 ERR("pthread_setcancelstate: %s", strerror(ret));
 158         }
 159         if (oldstate != PTHREAD_CANCEL_ENABLE) {
 160                 ERR("pthread_setcancelstate: unexpected oldstate");
 161         }
 162         sigfillset(&sig_all_blocked);
 163         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 164         if (ret) {
 165                 ERR("pthread_sigmask: %s", strerror(ret));
 166         }
 167         if (!URCU_TLS(ust_mutex_nest)++)
 168                 pthread_mutex_lock(&ust_mutex);
 169         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 170         if (ret) {
 171                 ERR("pthread_sigmask: %s", strerror(ret));
 172         }
 173 }
 174
 175 /*
 176  * Signal-safe.
 177  */
 178 void ust_unlock(void)
 179 {
 180         sigset_t sig_all_blocked, orig_mask;
 181         int ret, oldstate;
 182
 183         sigfillset(&sig_all_blocked);
 184         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
 185         if (ret) {
 186                 ERR("pthread_sigmask: %s", strerror(ret));
 187         }
 188         if (!--URCU_TLS(ust_mutex_nest))
 189                 pthread_mutex_unlock(&ust_mutex);
 190         ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
 191         if (ret) {
 192                 ERR("pthread_sigmask: %s", strerror(ret));
 193         }
 194         ret = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
 195         if (ret) {
 196                 ERR("pthread_setcancelstate: %s", strerror(ret));
 197         }
 198         if (oldstate != PTHREAD_CANCEL_DISABLE) {
 199                 ERR("pthread_setcancelstate: unexpected oldstate");
 200         }
 201 }
 202
 203 /*
 204  * Wait for either of these before continuing to the main
 205  * program:
 206  * - the register_done message from sessiond daemon
 207  *   (will let the sessiond daemon enable sessions before main
 208  *   starts.)
 209  * - sessiond daemon is not reachable.
 210  * - timeout (ensuring applications are resilient to session
 211  *   daemon problems).
 212  */
 213 static sem_t constructor_wait;
 214 /*
 215  * Doing this for both the global and local sessiond.
 216  */
 217 static int sem_count = { 2 };
 218
 219 /*
 220  * Counting nesting within lttng-ust. Used to ensure that calling fork()
 221  * from liblttng-ust does not execute the pre/post fork handlers.
 222  */
 223 static DEFINE_URCU_TLS(int, lttng_ust_nest_count);
 224
 225 /*
 226  * Info about socket and associated listener thread.
 227  */
 228 struct sock_info {
 229         const char *name;
 230         pthread_t ust_listener; /* listener thread */
 231         int root_handle;
 232         int constructor_sem_posted;
 233         int allowed;
 234         int global;
 235         int thread_active;
 236
 237         char sock_path[PATH_MAX];
 238         int socket;
 239         int notify_socket;
 240
 241         char wait_shm_path[PATH_MAX];
 242         char *wait_shm_mmap;
 243         /* Keep track of lazy state dump not performed yet. */
 244         int statedump_pending;
 245 };
 246
 247 /* Socket from app (connect) to session daemon (listen) for communication */
 248 struct sock_info global_apps = {
 249         .name = "global",
 250         .global = 1,
 251
 252         .root_handle = -1,
 253         .allowed = 1,
 254         .thread_active = 0,
 255
 256         .sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
 257         .socket = -1,
 258         .notify_socket = -1,
 259
 260         .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 261
 262         .statedump_pending = 0,
 263 };
 264
 265 /* TODO: allow global_apps_sock_path override */
 266
 267 struct sock_info local_apps = {
 268         .name = "local",
 269         .global = 0,
 270         .root_handle = -1,
 271         .allowed = 0,   /* Check setuid bit first */
 272         .thread_active = 0,
 273
 274         .socket = -1,
 275         .notify_socket = -1,
 276
 277         .statedump_pending = 0,
 278 };
 279
 280 static int wait_poll_fallback;
 281
 282 static const char *cmd_name_mapping[] = {
 283         [ LTTNG_UST_RELEASE ] = "Release",
 284         [ LTTNG_UST_SESSION ] = "Create Session",
 285         [ LTTNG_UST_TRACER_VERSION ] = "Get Tracer Version",
 286
 287         [ LTTNG_UST_TRACEPOINT_LIST ] = "Create Tracepoint List",
 288         [ LTTNG_UST_WAIT_QUIESCENT ] = "Wait for Quiescent State",
 289         [ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
 290         [ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
 291
 292         /* Session FD commands */
 293         [ LTTNG_UST_CHANNEL ] = "Create Channel",
 294         [ LTTNG_UST_SESSION_START ] = "Start Session",
 295         [ LTTNG_UST_SESSION_STOP ] = "Stop Session",
 296
 297         /* Channel FD commands */
 298         [ LTTNG_UST_STREAM ] = "Create Stream",
 299         [ LTTNG_UST_EVENT ] = "Create Event",
 300
 301         /* Event and Channel FD commands */
 302         [ LTTNG_UST_CONTEXT ] = "Create Context",
 303         [ LTTNG_UST_FLUSH_BUFFER ] = "Flush Buffer",
 304
 305         /* Event, Channel and Session commands */
 306         [ LTTNG_UST_ENABLE ] = "Enable",
 307         [ LTTNG_UST_DISABLE ] = "Disable",
 308
 309         /* Tracepoint list commands */
 310         [ LTTNG_UST_TRACEPOINT_LIST_GET ] = "List Next Tracepoint",
 311         [ LTTNG_UST_TRACEPOINT_FIELD_LIST_GET ] = "List Next Tracepoint Field",
 312
 313         /* Event FD commands */
 314         [ LTTNG_UST_FILTER ] = "Create Filter",
 315         [ LTTNG_UST_EXCLUSION ] = "Add exclusions to event",
 316 };
 317
 318 static const char *str_timeout;
 319 static int got_timeout_env;
 320
 321 extern void lttng_ring_buffer_client_overwrite_init(void);
 322 extern void lttng_ring_buffer_client_overwrite_rt_init(void);
 323 extern void lttng_ring_buffer_client_discard_init(void);
 324 extern void lttng_ring_buffer_client_discard_rt_init(void);
 325 extern void lttng_ring_buffer_metadata_client_init(void);
 326 extern void lttng_ring_buffer_client_overwrite_exit(void);
 327 extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
 328 extern void lttng_ring_buffer_client_discard_exit(void);
 329 extern void lttng_ring_buffer_client_discard_rt_exit(void);
 330 extern void lttng_ring_buffer_metadata_client_exit(void);
 331
 332 /*
 333  * Returns the HOME directory path. Caller MUST NOT free(3) the returned
 334  * pointer.
 335  */
 336 static
 337 const char *get_lttng_home_dir(void)
 338 {
 339        const char *val;
 340
 341        val = (const char *) lttng_secure_getenv("LTTNG_HOME");
 342        if (val != NULL) {
 343                return val;
 344        }
 345        return (const char *) lttng_secure_getenv("HOME");
 346 }
 347
 348 /*
 349  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 350  */
 351 static
 352 void lttng_fixup_nest_count_tls(void)
 353 {
 354         asm volatile ("" : : "m" (URCU_TLS(lttng_ust_nest_count)));
 355 }
 356
 357 static
 358 void lttng_fixup_ust_mutex_nest_tls(void)
 359 {
 360         asm volatile ("" : : "m" (URCU_TLS(ust_mutex_nest)));
 361 }
 362
 363 /*
 364  * Fixup urcu bp TLS.
 365  */
 366 static
 367 void lttng_fixup_urcu_bp_tls(void)
 368 {
 369         rcu_read_lock();
 370         rcu_read_unlock();
 371 }
 372
 373 int lttng_get_notify_socket(void *owner)
 374 {
 375         struct sock_info *info = owner;
 376
 377         return info->notify_socket;
 378 }
 379
 380 static
 381 void print_cmd(int cmd, int handle)
 382 {
 383         const char *cmd_name = "Unknown";
 384
 385         if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
 386                         && cmd_name_mapping[cmd]) {
 387                 cmd_name = cmd_name_mapping[cmd];
 388         }
 389         DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
 390                 cmd_name, cmd,
 391                 lttng_ust_obj_get_name(handle), handle);
 392 }
 393
 394 static
 395 int setup_local_apps(void)
 396 {
 397         const char *home_dir;
 398         uid_t uid;
 399
 400         uid = getuid();
 401         /*
 402          * Disallow per-user tracing for setuid binaries.
 403          */
 404         if (uid != geteuid()) {
 405                 assert(local_apps.allowed == 0);
 406                 return 0;
 407         }
 408         home_dir = get_lttng_home_dir();
 409         if (!home_dir) {
 410                 WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
 411                 assert(local_apps.allowed == 0);
 412                 return -ENOENT;
 413         }
 414         local_apps.allowed = 1;
 415         snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
 416                 home_dir,
 417                 LTTNG_DEFAULT_HOME_RUNDIR,
 418                 LTTNG_UST_SOCK_FILENAME);
 419         snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
 420                 LTTNG_UST_WAIT_FILENAME,
 421                 uid);
 422         return 0;
 423 }
 424
 425 /*
 426  * Get notify_sock timeout, in ms.
 427  * -1: wait forever. 0: don't wait. >0: timeout, in ms.
 428  */
 429 static
 430 long get_timeout(void)
 431 {
 432         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 433
 434         if (!got_timeout_env) {
 435                 str_timeout = getenv("LTTNG_UST_REGISTER_TIMEOUT");
 436                 got_timeout_env = 1;
 437         }
 438         if (str_timeout)
 439                 constructor_delay_ms = strtol(str_timeout, NULL, 10);
 440         return constructor_delay_ms;
 441 }
 442
 443 static
 444 long get_notify_sock_timeout(void)
 445 {
 446         return get_timeout();
 447 }
 448
 449 /*
 450  * Return values: -1: wait forever. 0: don't wait. 1: timeout wait.
 451  */
 452 static
 453 int get_constructor_timeout(struct timespec *constructor_timeout)
 454 {
 455         long constructor_delay_ms;
 456         int ret;
 457
 458         constructor_delay_ms = get_timeout();
 459
 460         switch (constructor_delay_ms) {
 461         case -1:/* fall-through */
 462         case 0:
 463                 return constructor_delay_ms;
 464         default:
 465                 break;
 466         }
 467
 468         /*
 469          * If we are unable to find the current time, don't wait.
 470          */
 471         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 472         if (ret) {
 473                 /* Don't wait. */
 474                 return 0;
 475         }
 476         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 477         constructor_timeout->tv_nsec +=
 478                 (constructor_delay_ms % 1000UL) * 1000000UL;
 479         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 480                 constructor_timeout->tv_sec++;
 481                 constructor_timeout->tv_nsec -= 1000000000UL;
 482         }
 483         /* Timeout wait (constructor_delay_ms). */
 484         return 1;
 485 }
 486
 487 static
 488 int register_to_sessiond(int socket, enum ustctl_socket_type type)
 489 {
 490         return ustcomm_send_reg_msg(socket,
 491                 type,
 492                 CAA_BITS_PER_LONG,
 493                 lttng_alignof(uint8_t) * CHAR_BIT,
 494                 lttng_alignof(uint16_t) * CHAR_BIT,
 495                 lttng_alignof(uint32_t) * CHAR_BIT,
 496                 lttng_alignof(uint64_t) * CHAR_BIT,
 497                 lttng_alignof(unsigned long) * CHAR_BIT);
 498 }
 499
 500 static
 501 int send_reply(int sock, struct ustcomm_ust_reply *lur)
 502 {
 503         ssize_t len;
 504
 505         len = ustcomm_send_unix_sock(sock, lur, sizeof(*lur));
 506         switch (len) {
 507         case sizeof(*lur):
 508                 DBG("message successfully sent");
 509                 return 0;
 510         default:
 511                 if (len == -ECONNRESET) {
 512                         DBG("remote end closed connection");
 513                         return 0;
 514                 }
 515                 if (len < 0)
 516                         return len;
 517                 DBG("incorrect message size: %zd", len);
 518                 return -EINVAL;
 519         }
 520 }
 521
 522 static
 523 int handle_register_done(struct sock_info *sock_info)
 524 {
 525         int ret;
 526
 527         if (sock_info->constructor_sem_posted)
 528                 return 0;
 529         sock_info->constructor_sem_posted = 1;
 530         if (uatomic_read(&sem_count) <= 0) {
 531                 return 0;
 532         }
 533         ret = uatomic_add_return(&sem_count, -1);
 534         if (ret == 0) {
 535                 ret = sem_post(&constructor_wait);
 536                 assert(!ret);
 537         }
 538         return 0;
 539 }
 540
 541 /*
 542  * Only execute pending statedump after the constructor semaphore has
 543  * been posted by each listener thread. This means statedump will only
 544  * be performed after the "registration done" command is received from
 545  * each session daemon the application is connected to.
 546  *
 547  * This ensures we don't run into deadlock issues with the dynamic
 548  * loader mutex, which is held while the constructor is called and
 549  * waiting on the constructor semaphore. All operations requiring this
 550  * dynamic loader lock need to be postponed using this mechanism.
 551  */
 552 static
 553 void handle_pending_statedump(struct sock_info *sock_info)
 554 {
 555         int ctor_passed = sock_info->constructor_sem_posted;
 556
 557         if (ctor_passed && sock_info->statedump_pending) {
 558                 sock_info->statedump_pending = 0;
 559                 pthread_mutex_lock(&ust_fork_mutex);
 560                 lttng_handle_pending_statedump(sock_info);
 561                 pthread_mutex_unlock(&ust_fork_mutex);
 562         }
 563 }
 564
 565 static
 566 int handle_message(struct sock_info *sock_info,
 567                 int sock, struct ustcomm_ust_msg *lum)
 568 {
 569         int ret = 0;
 570         const struct lttng_ust_objd_ops *ops;
 571         struct ustcomm_ust_reply lur;
 572         union ust_args args;
 573         ssize_t len;
 574
 575         memset(&lur, 0, sizeof(lur));
 576
 577         if (ust_lock()) {
 578                 ret = -LTTNG_UST_ERR_EXITING;
 579                 goto error;
 580         }
 581
 582         ops = objd_ops(lum->handle);
 583         if (!ops) {
 584                 ret = -ENOENT;
 585                 goto error;
 586         }
 587
 588         switch (lum->cmd) {
 589         case LTTNG_UST_REGISTER_DONE:
 590                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 591                         ret = handle_register_done(sock_info);
 592                 else
 593                         ret = -EINVAL;
 594                 break;
 595         case LTTNG_UST_RELEASE:
 596                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 597                         ret = -EPERM;
 598                 else
 599                         ret = lttng_ust_objd_unref(lum->handle, 1);
 600                 break;
 601         case LTTNG_UST_FILTER:
 602         {
 603                 /* Receive filter data */
 604                 struct lttng_ust_filter_bytecode_node *bytecode;
 605
 606                 if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
 607                         ERR("Filter data size is too large: %u bytes",
 608                                 lum->u.filter.data_size);
 609                         ret = -EINVAL;
 610                         goto error;
 611                 }
 612
 613                 if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
 614                         ERR("Filter reloc offset %u is not within data",
 615                                 lum->u.filter.reloc_offset);
 616                         ret = -EINVAL;
 617                         goto error;
 618                 }
 619
 620                 bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
 621                 if (!bytecode) {
 622                         ret = -ENOMEM;
 623                         goto error;
 624                 }
 625                 len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
 626                                 lum->u.filter.data_size);
 627                 switch (len) {
 628                 case 0: /* orderly shutdown */
 629                         ret = 0;
 630                         free(bytecode);
 631                         goto error;
 632                 default:
 633                         if (len == lum->u.filter.data_size) {
 634                                 DBG("filter data received");
 635                                 break;
 636                         } else if (len < 0) {
 637                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 638                                 if (len == -ECONNRESET) {
 639                                         ERR("%s remote end closed connection", sock_info->name);
 640                                         ret = len;
 641                                         free(bytecode);
 642                                         goto error;
 643                                 }
 644                                 ret = len;
 645                                 free(bytecode);
 646                                 goto error;
 647                         } else {
 648                                 DBG("incorrect filter data message size: %zd", len);
 649                                 ret = -EINVAL;
 650                                 free(bytecode);
 651                                 goto error;
 652                         }
 653                 }
 654                 bytecode->bc.len = lum->u.filter.data_size;
 655                 bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
 656                 bytecode->bc.seqnum = lum->u.filter.seqnum;
 657                 if (ops->cmd) {
 658                         ret = ops->cmd(lum->handle, lum->cmd,
 659                                         (unsigned long) bytecode,
 660                                         &args, sock_info);
 661                         if (ret) {
 662                                 free(bytecode);
 663                         }
 664                         /* don't free bytecode if everything went fine. */
 665                 } else {
 666                         ret = -ENOSYS;
 667                         free(bytecode);
 668                 }
 669                 break;
 670         }
 671         case LTTNG_UST_EXCLUSION:
 672         {
 673                 /* Receive exclusion names */
 674                 struct lttng_ust_excluder_node *node;
 675                 unsigned int count;
 676
 677                 count = lum->u.exclusion.count;
 678                 if (count == 0) {
 679                         /* There are no names to read */
 680                         ret = 0;
 681                         goto error;
 682                 }
 683                 node = zmalloc(sizeof(*node) +
 684                                 count * LTTNG_UST_SYM_NAME_LEN);
 685                 if (!node) {
 686                         ret = -ENOMEM;
 687                         goto error;
 688                 }
 689                 node->excluder.count = count;
 690                 len = ustcomm_recv_unix_sock(sock, node->excluder.names,
 691                                 count * LTTNG_UST_SYM_NAME_LEN);
 692                 switch (len) {
 693                 case 0: /* orderly shutdown */
 694                         ret = 0;
 695                         free(node);
 696                         goto error;
 697                 default:
 698                         if (len == count * LTTNG_UST_SYM_NAME_LEN) {
 699                                 DBG("Exclusion data received");
 700                                 break;
 701                         } else if (len < 0) {
 702                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 703                                 if (len == -ECONNRESET) {
 704                                         ERR("%s remote end closed connection", sock_info->name);
 705                                         ret = len;
 706                                         free(node);
 707                                         goto error;
 708                                 }
 709                                 ret = len;
 710                                 free(node);
 711                                 goto error;
 712                         } else {
 713                                 DBG("Incorrect exclusion data message size: %zd", len);
 714                                 ret = -EINVAL;
 715                                 free(node);
 716                                 goto error;
 717                         }
 718                 }
 719                 if (ops->cmd) {
 720                         ret = ops->cmd(lum->handle, lum->cmd,
 721                                         (unsigned long) node,
 722                                         &args, sock_info);
 723                         if (ret) {
 724                                 free(node);
 725                         }
 726                         /* Don't free exclusion data if everything went fine. */
 727                 } else {
 728                         ret = -ENOSYS;
 729                         free(node);
 730                 }
 731                 break;
 732         }
 733         case LTTNG_UST_CHANNEL:
 734         {
 735                 void *chan_data;
 736                 int wakeup_fd;
 737
 738                 len = ustcomm_recv_channel_from_sessiond(sock,
 739                                 &chan_data, lum->u.channel.len,
 740                                 &wakeup_fd);
 741                 switch (len) {
 742                 case 0: /* orderly shutdown */
 743                         ret = 0;
 744                         goto error;
 745                 default:
 746                         if (len == lum->u.channel.len) {
 747                                 DBG("channel data received");
 748                                 break;
 749                         } else if (len < 0) {
 750                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
 751                                 if (len == -ECONNRESET) {
 752                                         ERR("%s remote end closed connection", sock_info->name);
 753                                         ret = len;
 754                                         goto error;
 755                                 }
 756                                 ret = len;
 757                                 goto error;
 758                         } else {
 759                                 DBG("incorrect channel data message size: %zd", len);
 760                                 ret = -EINVAL;
 761                                 goto error;
 762                         }
 763                 }
 764                 args.channel.chan_data = chan_data;
 765                 args.channel.wakeup_fd = wakeup_fd;
 766                 if (ops->cmd)
 767                         ret = ops->cmd(lum->handle, lum->cmd,
 768                                         (unsigned long) &lum->u,
 769                                         &args, sock_info);
 770                 else
 771                         ret = -ENOSYS;
 772                 break;
 773         }
 774         case LTTNG_UST_STREAM:
 775         {
 776                 /* Receive shm_fd, wakeup_fd */
 777                 ret = ustcomm_recv_stream_from_sessiond(sock,
 778                         &lum->u.stream.len,
 779                         &args.stream.shm_fd,
 780                         &args.stream.wakeup_fd);
 781                 if (ret) {
 782                         goto error;
 783                 }
 784                 if (ops->cmd)
 785                         ret = ops->cmd(lum->handle, lum->cmd,
 786                                         (unsigned long) &lum->u,
 787                                         &args, sock_info);
 788                 else
 789                         ret = -ENOSYS;
 790                 break;
 791         }
 792         default:
 793                 if (ops->cmd)
 794                         ret = ops->cmd(lum->handle, lum->cmd,
 795                                         (unsigned long) &lum->u,
 796                                         &args, sock_info);
 797                 else
 798                         ret = -ENOSYS;
 799                 break;
 800         }
 801
 802         lur.handle = lum->handle;
 803         lur.cmd = lum->cmd;
 804         lur.ret_val = ret;
 805         if (ret >= 0) {
 806                 lur.ret_code = LTTNG_UST_OK;
 807         } else {
 808                 /*
 809                  * Use -LTTNG_UST_ERR as wildcard for UST internal
 810                  * error that are not caused by the transport, except if
 811                  * we already have a more precise error message to
 812                  * report.
 813                  */
 814                 if (ret > -LTTNG_UST_ERR) {
 815                         /* Translate code to UST error. */
 816                         switch (ret) {
 817                         case -EEXIST:
 818                                 lur.ret_code = -LTTNG_UST_ERR_EXIST;
 819                                 break;
 820                         case -EINVAL:
 821                                 lur.ret_code = -LTTNG_UST_ERR_INVAL;
 822                                 break;
 823                         case -ENOENT:
 824                                 lur.ret_code = -LTTNG_UST_ERR_NOENT;
 825                                 break;
 826                         case -EPERM:
 827                                 lur.ret_code = -LTTNG_UST_ERR_PERM;
 828                                 break;
 829                         case -ENOSYS:
 830                                 lur.ret_code = -LTTNG_UST_ERR_NOSYS;
 831                                 break;
 832                         default:
 833                                 lur.ret_code = -LTTNG_UST_ERR;
 834                                 break;
 835                         }
 836                 } else {
 837                         lur.ret_code = ret;
 838                 }
 839         }
 840         if (ret >= 0) {
 841                 switch (lum->cmd) {
 842                 case LTTNG_UST_TRACER_VERSION:
 843                         lur.u.version = lum->u.version;
 844                         break;
 845                 case LTTNG_UST_TRACEPOINT_LIST_GET:
 846                         memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
 847                         break;
 848                 }
 849         }
 850         DBG("Return value: %d", lur.ret_val);
 851         ret = send_reply(sock, &lur);
 852         if (ret < 0) {
 853                 DBG("error sending reply");
 854                 goto error;
 855         }
 856
 857         /*
 858          * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
 859          * after the reply.
 860          */
 861         if (lur.ret_code == LTTNG_UST_OK) {
 862                 switch (lum->cmd) {
 863                 case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
 864                         len = ustcomm_send_unix_sock(sock,
 865                                 &args.field_list.entry,
 866                                 sizeof(args.field_list.entry));
 867                         if (len < 0) {
 868                                 ret = len;
 869                                 goto error;
 870                         }
 871                         if (len != sizeof(args.field_list.entry)) {
 872                                 ret = -EINVAL;
 873                                 goto error;
 874                         }
 875                 }
 876         }
 877
 878 error:
 879         ust_unlock();
 880
 881         /*
 882          * Performed delayed statedump operations outside of the UST
 883          * lock. We need to take the dynamic loader lock before we take
 884          * the UST lock internally within handle_pending_statedump().
 885           */
 886         handle_pending_statedump(sock_info);
 887
 888         return ret;
 889 }
 890
 891 static
 892 void cleanup_sock_info(struct sock_info *sock_info, int exiting)
 893 {
 894         int ret;
 895
 896         if (sock_info->root_handle != -1) {
 897                 ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
 898                 if (ret) {
 899                         ERR("Error unref root handle");
 900                 }
 901                 sock_info->root_handle = -1;
 902         }
 903         sock_info->constructor_sem_posted = 0;
 904
 905         /*
 906          * wait_shm_mmap, socket and notify socket are used by listener
 907          * threads outside of the ust lock, so we cannot tear them down
 908          * ourselves, because we cannot join on these threads. Leave
 909          * responsibility of cleaning up these resources to the OS
 910          * process exit.
 911          */
 912         if (exiting)
 913                 return;
 914
 915         if (sock_info->socket != -1) {
 916                 ret = ustcomm_close_unix_sock(sock_info->socket);
 917                 if (ret) {
 918                         ERR("Error closing ust cmd socket");
 919                 }
 920                 sock_info->socket = -1;
 921         }
 922         if (sock_info->notify_socket != -1) {
 923                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 924                 if (ret) {
 925                         ERR("Error closing ust notify socket");
 926                 }
 927                 sock_info->notify_socket = -1;
 928         }
 929         if (sock_info->wait_shm_mmap) {
 930                 long page_size;
 931
 932                 page_size = sysconf(_SC_PAGE_SIZE);
 933                 if (page_size > 0) {
 934                         ret = munmap(sock_info->wait_shm_mmap, page_size);
 935                         if (ret) {
 936                                 ERR("Error unmapping wait shm");
 937                         }
 938                 }
 939                 sock_info->wait_shm_mmap = NULL;
 940         }
 941 }
 942
 943 /*
 944  * Using fork to set umask in the child process (not multi-thread safe).
 945  * We deal with the shm_open vs ftruncate race (happening when the
 946  * sessiond owns the shm and does not let everybody modify it, to ensure
 947  * safety against shm_unlink) by simply letting the mmap fail and
 948  * retrying after a few seconds.
 949  * For global shm, everybody has rw access to it until the sessiond
 950  * starts.
 951  */
 952 static
 953 int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 954 {
 955         int wait_shm_fd, ret;
 956         pid_t pid;
 957
 958         /*
 959          * Try to open read-only.
 960          */
 961         wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 962         if (wait_shm_fd >= 0) {
 963                 int32_t tmp_read;
 964                 ssize_t len;
 965                 size_t bytes_read = 0;
 966
 967                 /*
 968                  * Try to read the fd. If unable to do so, try opening
 969                  * it in write mode.
 970                  */
 971                 do {
 972                         len = read(wait_shm_fd,
 973                                 &((char *) &tmp_read)[bytes_read],
 974                                 sizeof(tmp_read) - bytes_read);
 975                         if (len > 0) {
 976                                 bytes_read += len;
 977                         }
 978                 } while ((len < 0 && errno == EINTR)
 979                         || (len > 0 && bytes_read < sizeof(tmp_read)));
 980                 if (bytes_read != sizeof(tmp_read)) {
 981                         ret = close(wait_shm_fd);
 982                         if (ret) {
 983                                 ERR("close wait_shm_fd");
 984                         }
 985                         goto open_write;
 986                 }
 987                 goto end;
 988         } else if (wait_shm_fd < 0 && errno != ENOENT) {
 989                 /*
 990                  * Real-only open did not work, and it's not because the
 991                  * entry was not present. It's a failure that prohibits
 992                  * using shm.
 993                  */
 994                 ERR("Error opening shm %s", sock_info->wait_shm_path);
 995                 goto end;
 996         }
 997
 998 open_write:
 999         /*
1000          * If the open failed because the file did not exist, or because
1001          * the file was not truncated yet, try creating it ourself.
1002          */
1003         URCU_TLS(lttng_ust_nest_count)++;
1004         pid = fork();
1005         URCU_TLS(lttng_ust_nest_count)--;
1006         if (pid > 0) {
1007                 int status;
1008
1009                 /*
1010                  * Parent: wait for child to return, in which case the
1011                  * shared memory map will have been created.
1012                  */
1013                 pid = wait(&status);
1014                 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
1015                         wait_shm_fd = -1;
1016                         goto end;
1017                 }
1018                 /*
1019                  * Try to open read-only again after creation.
1020                  */
1021                 wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
1022                 if (wait_shm_fd < 0) {
1023                         /*
1024                          * Real-only open did not work. It's a failure
1025                          * that prohibits using shm.
1026                          */
1027                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1028                         goto end;
1029                 }
1030                 goto end;
1031         } else if (pid == 0) {
1032                 int create_mode;
1033
1034                 /* Child */
1035                 create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
1036                 if (sock_info->global)
1037                         create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
1038                 /*
1039                  * We're alone in a child process, so we can modify the
1040                  * process-wide umask.
1041                  */
1042                 umask(~create_mode);
1043                 /*
1044                  * Try creating shm (or get rw access).
1045                  * We don't do an exclusive open, because we allow other
1046                  * processes to create+ftruncate it concurrently.
1047                  */
1048                 wait_shm_fd = shm_open(sock_info->wait_shm_path,
1049                                 O_RDWR | O_CREAT, create_mode);
1050                 if (wait_shm_fd >= 0) {
1051                         ret = ftruncate(wait_shm_fd, mmap_size);
1052                         if (ret) {
1053                                 PERROR("ftruncate");
1054                                 _exit(EXIT_FAILURE);
1055                         }
1056                         _exit(EXIT_SUCCESS);
1057                 }
1058                 /*
1059                  * For local shm, we need to have rw access to accept
1060                  * opening it: this means the local sessiond will be
1061                  * able to wake us up. For global shm, we open it even
1062                  * if rw access is not granted, because the root.root
1063                  * sessiond will be able to override all rights and wake
1064                  * us up.
1065                  */
1066                 if (!sock_info->global && errno != EACCES) {
1067                         ERR("Error opening shm %s", sock_info->wait_shm_path);
1068                         _exit(EXIT_FAILURE);
1069                 }
1070                 /*
1071                  * The shm exists, but we cannot open it RW. Report
1072                  * success.
1073                  */
1074                 _exit(EXIT_SUCCESS);
1075         } else {
1076                 return -1;
1077         }
1078 end:
1079         if (wait_shm_fd >= 0 && !sock_info->global) {
1080                 struct stat statbuf;
1081
1082                 /*
1083                  * Ensure that our user is the owner of the shm file for
1084                  * local shm. If we do not own the file, it means our
1085                  * sessiond will not have access to wake us up (there is
1086                  * probably a rogue process trying to fake our
1087                  * sessiond). Fallback to polling method in this case.
1088                  */
1089                 ret = fstat(wait_shm_fd, &statbuf);
1090                 if (ret) {
1091                         PERROR("fstat");
1092                         goto error_close;
1093                 }
1094                 if (statbuf.st_uid != getuid())
1095                         goto error_close;
1096         }
1097         return wait_shm_fd;
1098
1099 error_close:
1100         ret = close(wait_shm_fd);
1101         if (ret) {
1102                 PERROR("Error closing fd");
1103         }
1104         return -1;
1105 }
1106
1107 static
1108 char *get_map_shm(struct sock_info *sock_info)
1109 {
1110         long page_size;
1111         int wait_shm_fd, ret;
1112         char *wait_shm_mmap;
1113
1114         page_size = sysconf(_SC_PAGE_SIZE);
1115         if (page_size < 0) {
1116                 goto error;
1117         }
1118
1119         wait_shm_fd = get_wait_shm(sock_info, page_size);
1120         if (wait_shm_fd < 0) {
1121                 goto error;
1122         }
1123         wait_shm_mmap = mmap(NULL, page_size, PROT_READ,
1124                   MAP_SHARED, wait_shm_fd, 0);
1125         /* close shm fd immediately after taking the mmap reference */
1126         ret = close(wait_shm_fd);
1127         if (ret) {
1128                 PERROR("Error closing fd");
1129         }
1130         if (wait_shm_mmap == MAP_FAILED) {
1131                 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
1132                 goto error;
1133         }
1134         return wait_shm_mmap;
1135
1136 error:
1137         return NULL;
1138 }
1139
1140 static
1141 void wait_for_sessiond(struct sock_info *sock_info)
1142 {
1143         if (ust_lock()) {
1144                 goto quit;
1145         }
1146         if (wait_poll_fallback) {
1147                 goto error;
1148         }
1149         if (!sock_info->wait_shm_mmap) {
1150                 sock_info->wait_shm_mmap = get_map_shm(sock_info);
1151                 if (!sock_info->wait_shm_mmap)
1152                         goto error;
1153         }
1154         ust_unlock();
1155
1156         DBG("Waiting for %s apps sessiond", sock_info->name);
1157         /* Wait for futex wakeup */
1158         if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
1159                 goto end_wait;
1160
1161         while (futex_async((int32_t *) sock_info->wait_shm_mmap,
1162                         FUTEX_WAIT, 0, NULL, NULL, 0)) {
1163                 switch (errno) {
1164                 case EWOULDBLOCK:
1165                         /* Value already changed. */
1166                         goto end_wait;
1167                 case EINTR:
1168                         /* Retry if interrupted by signal. */
1169                         break;  /* Get out of switch. */
1170                 case EFAULT:
1171                         wait_poll_fallback = 1;
1172                         DBG(
1173 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
1174 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
1175 "Please upgrade your kernel "
1176 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
1177 "mainline). LTTng-UST will use polling mode fallback.");
1178                         if (ust_debug())
1179                                 PERROR("futex");
1180                         goto end_wait;
1181                 }
1182         }
1183 end_wait:
1184         return;
1185
1186 quit:
1187         ust_unlock();
1188         return;
1189
1190 error:
1191         ust_unlock();
1192         return;
1193 }
1194
1195 /*
1196  * This thread does not allocate any resource, except within
1197  * handle_message, within mutex protection. This mutex protects against
1198  * fork and exit.
1199  * The other moment it allocates resources is at socket connection, which
1200  * is also protected by the mutex.
1201  */
1202 static
1203 void *ust_listener_thread(void *arg)
1204 {
1205         struct sock_info *sock_info = arg;
1206         int sock, ret, prev_connect_failed = 0, has_waited = 0;
1207         long timeout;
1208
1209         /* Restart trying to connect to the session daemon */
1210 restart:
1211         if (prev_connect_failed) {
1212                 /* Wait for sessiond availability with pipe */
1213                 wait_for_sessiond(sock_info);
1214                 if (has_waited) {
1215                         has_waited = 0;
1216                         /*
1217                          * Sleep for 5 seconds before retrying after a
1218                          * sequence of failure / wait / failure. This
1219                          * deals with a killed or broken session daemon.
1220                          */
1221                         sleep(5);
1222                 }
1223                 has_waited = 1;
1224                 prev_connect_failed = 0;
1225         }
1226
1227         if (sock_info->socket != -1) {
1228                 ret = ustcomm_close_unix_sock(sock_info->socket);
1229                 if (ret) {
1230                         ERR("Error closing %s ust cmd socket",
1231                                 sock_info->name);
1232                 }
1233                 sock_info->socket = -1;
1234         }
1235         if (sock_info->notify_socket != -1) {
1236                 ret = ustcomm_close_unix_sock(sock_info->notify_socket);
1237                 if (ret) {
1238                         ERR("Error closing %s ust notify socket",
1239                                 sock_info->name);
1240                 }
1241                 sock_info->notify_socket = -1;
1242         }
1243
1244         /*
1245          * Register. We need to perform both connect and sending
1246          * registration message before doing the next connect otherwise
1247          * we may reach unix socket connect queue max limits and block
1248          * on the 2nd connect while the session daemon is awaiting the
1249          * first connect registration message.
1250          */
1251         /* Connect cmd socket */
1252         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
1253         if (ret < 0) {
1254                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1255                 prev_connect_failed = 1;
1256
1257                 if (ust_lock()) {
1258                         goto quit;
1259                 }
1260
1261                 /*
1262                  * If we cannot find the sessiond daemon, don't delay
1263                  * constructor execution.
1264                  */
1265                 ret = handle_register_done(sock_info);
1266                 assert(!ret);
1267                 ust_unlock();
1268                 goto restart;
1269         }
1270         sock_info->socket = ret;
1271
1272         if (ust_lock()) {
1273                 goto quit;
1274         }
1275
1276         /*
1277          * Create only one root handle per listener thread for the whole
1278          * process lifetime, so we ensure we get ID which is statically
1279          * assigned to the root handle.
1280          */
1281         if (sock_info->root_handle == -1) {
1282                 ret = lttng_abi_create_root_handle();
1283                 if (ret < 0) {
1284                         ERR("Error creating root handle");
1285                         goto quit;
1286                 }
1287                 sock_info->root_handle = ret;
1288         }
1289
1290         ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
1291         if (ret < 0) {
1292                 ERR("Error registering to %s ust cmd socket",
1293                         sock_info->name);
1294                 prev_connect_failed = 1;
1295                 /*
1296                  * If we cannot register to the sessiond daemon, don't
1297                  * delay constructor execution.
1298                  */
1299                 ret = handle_register_done(sock_info);
1300                 assert(!ret);
1301                 ust_unlock();
1302                 goto restart;
1303         }
1304
1305         ust_unlock();
1306
1307         /* Connect notify socket */
1308         ret = ustcomm_connect_unix_sock(sock_info->sock_path);
1309         if (ret < 0) {
1310                 DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
1311                 prev_connect_failed = 1;
1312
1313                 if (ust_lock()) {
1314                         goto quit;
1315                 }
1316
1317                 /*
1318                  * If we cannot find the sessiond daemon, don't delay
1319                  * constructor execution.
1320                  */
1321                 ret = handle_register_done(sock_info);
1322                 assert(!ret);
1323                 ust_unlock();
1324                 goto restart;
1325         }
1326         sock_info->notify_socket = ret;
1327
1328         timeout = get_notify_sock_timeout();
1329         if (timeout >= 0) {
1330                 /*
1331                  * Give at least 10ms to sessiond to reply to
1332                  * notifications.
1333                  */
1334                 if (timeout < 10)
1335                         timeout = 10;
1336                 ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
1337                                 timeout);
1338                 if (ret < 0) {
1339                         WARN("Error setting socket receive timeout");
1340                 }
1341                 ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
1342                                 timeout);
1343                 if (ret < 0) {
1344                         WARN("Error setting socket send timeout");
1345                 }
1346         } else if (timeout < -1) {
1347                 WARN("Unsupported timeout value %ld", timeout);
1348         }
1349
1350         if (ust_lock()) {
1351                 goto quit;
1352         }
1353
1354         ret = register_to_sessiond(sock_info->notify_socket,
1355                         USTCTL_SOCKET_NOTIFY);
1356         if (ret < 0) {
1357                 ERR("Error registering to %s ust notify socket",
1358                         sock_info->name);
1359                 prev_connect_failed = 1;
1360                 /*
1361                  * If we cannot register to the sessiond daemon, don't
1362                  * delay constructor execution.
1363                  */
1364                 ret = handle_register_done(sock_info);
1365                 assert(!ret);
1366                 ust_unlock();
1367                 goto restart;
1368         }
1369         sock = sock_info->socket;
1370
1371         ust_unlock();
1372
1373         for (;;) {
1374                 ssize_t len;
1375                 struct ustcomm_ust_msg lum;
1376
1377                 len = ustcomm_recv_unix_sock(sock, &lum, sizeof(lum));
1378                 switch (len) {
1379                 case 0: /* orderly shutdown */
1380                         DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
1381                         if (ust_lock()) {
1382                                 goto quit;
1383                         }
1384                         /*
1385                          * Either sessiond has shutdown or refused us by closing the socket.
1386                          * In either case, we don't want to delay construction execution,
1387                          * and we need to wait before retry.
1388                          */
1389                         prev_connect_failed = 1;
1390                         /*
1391                          * If we cannot register to the sessiond daemon, don't
1392                          * delay constructor execution.
1393                          */
1394                         ret = handle_register_done(sock_info);
1395                         assert(!ret);
1396                         ust_unlock();
1397                         goto end;
1398                 case sizeof(lum):
1399                         print_cmd(lum.cmd, lum.handle);
1400                         ret = handle_message(sock_info, sock, &lum);
1401                         if (ret) {
1402                                 ERR("Error handling message for %s socket",
1403                                         sock_info->name);
1404                                 /*
1405                                  * Close socket if protocol error is
1406                                  * detected.
1407                                  */
1408                                 goto end;
1409                         }
1410                         continue;
1411                 default:
1412                         if (len < 0) {
1413                                 DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
1414                         } else {
1415                                 DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
1416                         }
1417                         if (len == -ECONNRESET) {
1418                                 DBG("%s remote end closed connection", sock_info->name);
1419                                 goto end;
1420                         }
1421                         goto end;
1422                 }
1423
1424         }
1425 end:
1426         if (ust_lock()) {
1427                 goto quit;
1428         }
1429         /* Cleanup socket handles before trying to reconnect */
1430         lttng_ust_objd_table_owner_cleanup(sock_info);
1431         ust_unlock();
1432         goto restart;   /* try to reconnect */
1433
1434 quit:
1435         ust_unlock();
1436
1437         pthread_mutex_lock(&ust_exit_mutex);
1438         sock_info->thread_active = 0;
1439         pthread_mutex_unlock(&ust_exit_mutex);
1440         return NULL;
1441 }
1442
1443 /*
1444  * Weak symbol to call when the ust malloc wrapper is not loaded.
1445  */
1446 __attribute__((weak))
1447 void lttng_ust_malloc_wrapper_init(void)
1448 {
1449 }
1450
1451 /*
1452  * sessiond monitoring thread: monitor presence of global and per-user
1453  * sessiond by polling the application common named pipe.
1454  */
1455 void __attribute__((constructor)) lttng_ust_init(void)
1456 {
1457         struct timespec constructor_timeout;
1458         sigset_t sig_all_blocked, orig_parent_mask;
1459         pthread_attr_t thread_attr;
1460         int timeout_mode;
1461         int ret;
1462
1463         if (uatomic_xchg(&initialized, 1) == 1)
1464                 return;
1465
1466         /*
1467          * Fixup interdependency between TLS fixup mutex (which happens
1468          * to be the dynamic linker mutex) and ust_lock, taken within
1469          * the ust lock.
1470          */
1471         lttng_fixup_urcu_bp_tls();
1472         lttng_fixup_ringbuffer_tls();
1473         lttng_fixup_vtid_tls();
1474         lttng_fixup_nest_count_tls();
1475         lttng_fixup_procname_tls();
1476         lttng_fixup_ust_mutex_nest_tls();
1477
1478         /*
1479          * We want precise control over the order in which we construct
1480          * our sub-libraries vs starting to receive commands from
1481          * sessiond (otherwise leading to errors when trying to create
1482          * sessiond before the init functions are completed).
1483          */
1484         init_usterr();
1485         init_tracepoint();
1486         lttng_ust_clock_init();
1487         lttng_ust_getcpu_init();
1488         lttng_ust_statedump_init();
1489         lttng_ring_buffer_metadata_client_init();
1490         lttng_ring_buffer_client_overwrite_init();
1491         lttng_ring_buffer_client_overwrite_rt_init();
1492         lttng_ring_buffer_client_discard_init();
1493         lttng_ring_buffer_client_discard_rt_init();
1494         lttng_perf_counter_init();
1495         lttng_context_init();
1496         /*
1497          * Invoke ust malloc wrapper init before starting other threads.
1498          */
1499         lttng_ust_malloc_wrapper_init();
1500
1501         timeout_mode = get_constructor_timeout(&constructor_timeout);
1502
1503         ret = sem_init(&constructor_wait, 0, 0);
1504         assert(!ret);
1505
1506         ret = setup_local_apps();
1507         if (ret) {
1508                 DBG("local apps setup returned %d", ret);
1509         }
1510
1511         /* A new thread created by pthread_create inherits the signal mask
1512          * from the parent. To avoid any signal being received by the
1513          * listener thread, we block all signals temporarily in the parent,
1514          * while we create the listener thread.
1515          */
1516         sigfillset(&sig_all_blocked);
1517         ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
1518         if (ret) {
1519                 ERR("pthread_sigmask: %s", strerror(ret));
1520         }
1521
1522         ret = pthread_attr_init(&thread_attr);
1523         if (ret) {
1524                 ERR("pthread_attr_init: %s", strerror(ret));
1525         }
1526         ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
1527         if (ret) {
1528                 ERR("pthread_attr_setdetachstate: %s", strerror(ret));
1529         }
1530
1531         pthread_mutex_lock(&ust_exit_mutex);
1532         ret = pthread_create(&global_apps.ust_listener, &thread_attr,
1533                         ust_listener_thread, &global_apps);
1534         if (ret) {
1535                 ERR("pthread_create global: %s", strerror(ret));
1536         }
1537         global_apps.thread_active = 1;
1538         pthread_mutex_unlock(&ust_exit_mutex);
1539
1540         if (local_apps.allowed) {
1541                 pthread_mutex_lock(&ust_exit_mutex);
1542                 ret = pthread_create(&local_apps.ust_listener, &thread_attr,
1543                                 ust_listener_thread, &local_apps);
1544                 if (ret) {
1545                         ERR("pthread_create local: %s", strerror(ret));
1546                 }
1547                 local_apps.thread_active = 1;
1548                 pthread_mutex_unlock(&ust_exit_mutex);
1549         } else {
1550                 handle_register_done(&local_apps);
1551         }
1552         ret = pthread_attr_destroy(&thread_attr);
1553         if (ret) {
1554                 ERR("pthread_attr_destroy: %s", strerror(ret));
1555         }
1556
1557         /* Restore original signal mask in parent */
1558         ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
1559         if (ret) {
1560                 ERR("pthread_sigmask: %s", strerror(ret));
1561         }
1562
1563         switch (timeout_mode) {
1564         case 1: /* timeout wait */
1565                 do {
1566                         ret = sem_timedwait(&constructor_wait,
1567                                         &constructor_timeout);
1568                 } while (ret < 0 && errno == EINTR);
1569                 if (ret < 0 && errno == ETIMEDOUT) {
1570                         ERR("Timed out waiting for lttng-sessiond");
1571                 } else {
1572                         assert(!ret);
1573                 }
1574                 break;
1575         case -1:/* wait forever */
1576                 do {
1577                         ret = sem_wait(&constructor_wait);
1578                 } while (ret < 0 && errno == EINTR);
1579                 assert(!ret);
1580                 break;
1581         case 0: /* no timeout */
1582                 break;
1583         }
1584 }
1585
1586 static
1587 void lttng_ust_cleanup(int exiting)
1588 {
1589         cleanup_sock_info(&global_apps, exiting);
1590         cleanup_sock_info(&local_apps, exiting);
1591         /*
1592          * The teardown in this function all affect data structures
1593          * accessed under the UST lock by the listener thread. This
1594          * lock, along with the lttng_ust_comm_should_quit flag, ensure
1595          * that none of these threads are accessing this data at this
1596          * point.
1597          */
1598         lttng_ust_abi_exit();
1599         lttng_ust_events_exit();
1600         lttng_context_exit();
1601         lttng_perf_counter_exit();
1602         lttng_ring_buffer_client_discard_rt_exit();
1603         lttng_ring_buffer_client_discard_exit();
1604         lttng_ring_buffer_client_overwrite_rt_exit();
1605         lttng_ring_buffer_client_overwrite_exit();
1606         lttng_ring_buffer_metadata_client_exit();
1607         lttng_ust_statedump_destroy();
1608         exit_tracepoint();
1609         if (!exiting) {
1610                 /* Reinitialize values for fork */
1611                 sem_count = 2;
1612                 lttng_ust_comm_should_quit = 0;
1613                 initialized = 0;
1614         }
1615 }
1616
1617 void __attribute__((destructor)) lttng_ust_exit(void)
1618 {
1619         int ret;
1620
1621         /*
1622          * Using pthread_cancel here because:
1623          * A) we don't want to hang application teardown.
1624          * B) the thread is not allocating any resource.
1625          */
1626
1627         /*
1628          * Require the communication thread to quit. Synchronize with
1629          * mutexes to ensure it is not in a mutex critical section when
1630          * pthread_cancel is later called.
1631          */
1632         ust_lock_nocheck();
1633         lttng_ust_comm_should_quit = 1;
1634         ust_unlock();
1635
1636         pthread_mutex_lock(&ust_exit_mutex);
1637         /* cancel threads */
1638         if (global_apps.thread_active) {
1639                 ret = pthread_cancel(global_apps.ust_listener);
1640                 if (ret) {
1641                         ERR("Error cancelling global ust listener thread: %s",
1642                                 strerror(ret));
1643                 } else {
1644                         global_apps.thread_active = 0;
1645                 }
1646         }
1647         if (local_apps.thread_active) {
1648                 ret = pthread_cancel(local_apps.ust_listener);
1649                 if (ret) {
1650                         ERR("Error cancelling local ust listener thread: %s",
1651                                 strerror(ret));
1652                 } else {
1653                         local_apps.thread_active = 0;
1654                 }
1655         }
1656         pthread_mutex_unlock(&ust_exit_mutex);
1657
1658         /*
1659          * Do NOT join threads: use of sys_futex makes it impossible to
1660          * join the threads without using async-cancel, but async-cancel
1661          * is delivered by a signal, which could hit the target thread
1662          * anywhere in its code path, including while the ust_lock() is
1663          * held, causing a deadlock for the other thread. Let the OS
1664          * cleanup the threads if there are stalled in a syscall.
1665          */
1666         lttng_ust_cleanup(1);
1667 }
1668
1669 /*
1670  * We exclude the worker threads across fork and clone (except
1671  * CLONE_VM), because these system calls only keep the forking thread
1672  * running in the child.  Therefore, we don't want to call fork or clone
1673  * in the middle of an tracepoint or ust tracing state modification.
1674  * Holding this mutex protects these structures across fork and clone.
1675  */
1676 void ust_before_fork(sigset_t *save_sigset)
1677 {
1678         /*
1679          * Disable signals. This is to avoid that the child intervenes
1680          * before it is properly setup for tracing. It is safer to
1681          * disable all signals, because then we know we are not breaking
1682          * anything by restoring the original mask.
1683          */
1684         sigset_t all_sigs;
1685         int ret;
1686
1687         if (URCU_TLS(lttng_ust_nest_count))
1688                 return;
1689         /* Disable signals */
1690         sigfillset(&all_sigs);
1691         ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
1692         if (ret == -1) {
1693                 PERROR("sigprocmask");
1694         }
1695
1696         pthread_mutex_lock(&ust_fork_mutex);
1697
1698         ust_lock_nocheck();
1699         rcu_bp_before_fork();
1700 }
1701
1702 static void ust_after_fork_common(sigset_t *restore_sigset)
1703 {
1704         int ret;
1705
1706         DBG("process %d", getpid());
1707         ust_unlock();
1708
1709         pthread_mutex_unlock(&ust_fork_mutex);
1710
1711         /* Restore signals */
1712         ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
1713         if (ret == -1) {
1714                 PERROR("sigprocmask");
1715         }
1716 }
1717
1718 void ust_after_fork_parent(sigset_t *restore_sigset)
1719 {
1720         if (URCU_TLS(lttng_ust_nest_count))
1721                 return;
1722         DBG("process %d", getpid());
1723         rcu_bp_after_fork_parent();
1724         /* Release mutexes and reenable signals */
1725         ust_after_fork_common(restore_sigset);
1726 }
1727
1728 /*
1729  * After fork, in the child, we need to cleanup all the leftover state,
1730  * except the worker thread which already magically disappeared thanks
1731  * to the weird Linux fork semantics. After tyding up, we call
1732  * lttng_ust_init() again to start over as a new PID.
1733  *
1734  * This is meant for forks() that have tracing in the child between the
1735  * fork and following exec call (if there is any).
1736  */
1737 void ust_after_fork_child(sigset_t *restore_sigset)
1738 {
1739         if (URCU_TLS(lttng_ust_nest_count))
1740                 return;
1741         DBG("process %d", getpid());
1742         /* Release urcu mutexes */
1743         rcu_bp_after_fork_child();
1744         lttng_ust_cleanup(0);
1745         lttng_context_vtid_reset();
1746         /* Release mutexes and reenable signals */
1747         ust_after_fork_common(restore_sigset);
1748         lttng_ust_init();
1749 }
1750
1751 void lttng_ust_sockinfo_session_enabled(void *owner)
1752 {
1753         struct sock_info *sock_info = owner;
1754         sock_info->statedump_pending = 1;
1755 }