libust/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 #include <sys/types.h>
  23 #include <sys/socket.h>
  24 #include <sys/prctl.h>
  25 #include <unistd.h>
  26 #include <errno.h>
  27 #include <pthread.h>
  28 #include <semaphore.h>
  29 #include <time.h>
  30 #include <assert.h>
  31 #include <urcu/uatomic.h>
  32
  33 #include <lttng-ust-comm.h>
  34 #include <ust/usterr-signal-safe.h>
  35 #include <ust/lttng-ust-abi.h>
  36 #include <ust/tracepoint.h>
  37 #include <ust/tracepoint-internal.h>
  38
  39 /*
  40  * Has lttng ust comm constructor been called ?
  41  */
  42 static int initialized;
  43
  44 /*
  45  * communication thread mutex. Held when handling a command, also held
  46  * by fork() to deal with removal of threads, and by exit path.
  47  */
  48 static pthread_mutex_t lttng_ust_comm_mutex = PTHREAD_MUTEX_INITIALIZER;
  49
  50 /* Should the ust comm thread quit ? */
  51 static int lttng_ust_comm_should_quit;
  52
  53 /*
  54  * Wait for either of these before continuing to the main
  55  * program:
  56  * - the register_done message from sessiond daemon
  57  *   (will let the sessiond daemon enable sessions before main
  58  *   starts.)
  59  * - sessiond daemon is not reachable.
  60  * - timeout (ensuring applications are resilient to session
  61  *   daemon problems).
  62  */
  63 static sem_t constructor_wait;
  64 /*
  65  * Doing this for both the global and local sessiond.
  66  */
  67 static int sem_count = { 2 };
  68
  69 /*
  70  * Info about socket and associated listener thread.
  71  */
  72 struct sock_info {
  73         const char *name;
  74         char sock_path[PATH_MAX];
  75         int socket;
  76         pthread_t ust_listener; /* listener thread */
  77         int root_handle;
  78         int constructor_sem_posted;
  79         int allowed;
  80 };
  81
  82 /* Socket from app (connect) to session daemon (listen) for communication */
  83 struct sock_info global_apps = {
  84         .name = "global",
  85         .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
  86         .socket = -1,
  87         .root_handle = -1,
  88         .allowed = 1,
  89 };
  90
  91 /* TODO: allow global_apps_sock_path override */
  92
  93 struct sock_info local_apps = {
  94         .name = "local",
  95         .socket = -1,
  96         .root_handle = -1,
  97         .allowed = 0,   /* Check setuid bit first */
  98 };
  99
 100 extern void ltt_ring_buffer_client_overwrite_init(void);
 101 extern void ltt_ring_buffer_client_discard_init(void);
 102 extern void ltt_ring_buffer_metadata_client_init(void);
 103 extern void ltt_ring_buffer_client_overwrite_exit(void);
 104 extern void ltt_ring_buffer_client_discard_exit(void);
 105 extern void ltt_ring_buffer_metadata_client_exit(void);
 106
 107 static
 108 int setup_local_apps(void)
 109 {
 110         const char *home_dir;
 111
 112         /*
 113          * Disallow per-user tracing for setuid binaries.
 114          */
 115         if (getuid() != geteuid()) {
 116                 local_apps.allowed = 0;
 117                 return 0;
 118         } else {
 119                 local_apps.allowed = 1;
 120         }
 121         home_dir = (const char *) getenv("HOME");
 122         if (!home_dir)
 123                 return -ENOENT;
 124         snprintf(local_apps.sock_path, PATH_MAX,
 125                  DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
 126         return 0;
 127 }
 128
 129 static
 130 int register_app_to_sessiond(int socket)
 131 {
 132         ssize_t ret;
 133         int prctl_ret;
 134         struct {
 135                 uint32_t major;
 136                 uint32_t minor;
 137                 pid_t pid;
 138                 pid_t ppid;
 139                 uid_t uid;
 140                 gid_t gid;
 141                 char name[16];  /* process name */
 142         } reg_msg;
 143
 144         reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
 145         reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
 146         reg_msg.pid = getpid();
 147         reg_msg.ppid = getppid();
 148         reg_msg.uid = getuid();
 149         reg_msg.gid = getgid();
 150         prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
 151         if (prctl_ret) {
 152                 ERR("Error executing prctl");
 153                 return -errno;
 154         }
 155
 156         ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
 157         if (ret >= 0 && ret != sizeof(reg_msg))
 158                 return -EIO;
 159         return ret;
 160 }
 161
 162 static
 163 int send_reply(int sock, struct lttcomm_ust_reply *lur)
 164 {
 165         ssize_t len;
 166
 167         len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
 168         switch (len) {
 169         case sizeof(*lur):
 170                 DBG("message successfully sent");
 171                 return 0;
 172         case -1:
 173                 if (errno == ECONNRESET) {
 174                         printf("remote end closed connection\n");
 175                         return 0;
 176                 }
 177                 return -1;
 178         default:
 179                 printf("incorrect message size: %zd\n", len);
 180                 return -1;
 181         }
 182 }
 183
 184 static
 185 int handle_register_done(struct sock_info *sock_info)
 186 {
 187         int ret;
 188
 189         if (sock_info->constructor_sem_posted)
 190                 return 0;
 191         sock_info->constructor_sem_posted = 1;
 192         ret = uatomic_add_return(&sem_count, -1);
 193         if (ret == 0) {
 194                 ret = sem_post(&constructor_wait);
 195                 assert(!ret);
 196         }
 197         return 0;
 198 }
 199
 200 static
 201 int handle_message(struct sock_info *sock_info,
 202                 int sock, struct lttcomm_ust_msg *lum)
 203 {
 204         int ret = 0;
 205         const struct objd_ops *ops;
 206         struct lttcomm_ust_reply lur;
 207
 208         pthread_mutex_lock(&lttng_ust_comm_mutex);
 209
 210         memset(&lur, 0, sizeof(lur));
 211
 212         if (lttng_ust_comm_should_quit) {
 213                 ret = -EPERM;
 214                 goto end;
 215         }
 216
 217         ops = objd_ops(lum->handle);
 218         if (!ops) {
 219                 ret = -ENOENT;
 220                 goto end;
 221         }
 222
 223         switch (lum->cmd) {
 224         case LTTNG_UST_REGISTER_DONE:
 225                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 226                         ret = handle_register_done(sock_info);
 227                 else
 228                         ret = -EINVAL;
 229                 break;
 230         case LTTNG_UST_RELEASE:
 231                 if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 232                         ret = -EPERM;
 233                 else
 234                         ret = objd_unref(lum->handle);
 235                 break;
 236         default:
 237                 if (ops->cmd)
 238                         ret = ops->cmd(lum->handle, lum->cmd,
 239                                         (unsigned long) &lum->u);
 240                 else
 241                         ret = -ENOSYS;
 242                 break;
 243         }
 244
 245 end:
 246         lur.handle = lum->handle;
 247         lur.cmd = lum->cmd;
 248         lur.ret_val = ret;
 249         if (ret >= 0) {
 250                 lur.ret_code = LTTCOMM_OK;
 251         } else {
 252                 lur.ret_code = LTTCOMM_SESSION_FAIL;
 253         }
 254         ret = send_reply(sock, &lur);
 255
 256         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 257         return ret;
 258 }
 259
 260 static
 261 void cleanup_sock_info(struct sock_info *sock_info)
 262 {
 263         int ret;
 264
 265         if (sock_info->socket != -1) {
 266                 ret = close(sock_info->socket);
 267                 if (ret) {
 268                         ERR("Error closing local apps socket");
 269                 }
 270                 sock_info->socket = -1;
 271         }
 272         if (sock_info->root_handle != -1) {
 273                 ret = objd_unref(sock_info->root_handle);
 274                 if (ret) {
 275                         ERR("Error unref root handle");
 276                 }
 277                 sock_info->root_handle = -1;
 278         }
 279 }
 280
 281 /*
 282  * This thread does not allocate any resource, except within
 283  * handle_message, within mutex protection. This mutex protects against
 284  * fork and exit.
 285  * The other moment it allocates resources is at socket connexion, which
 286  * is also protected by the mutex.
 287  */
 288 static
 289 void *ust_listener_thread(void *arg)
 290 {
 291         struct sock_info *sock_info = arg;
 292         int sock, ret;
 293
 294         /* Restart trying to connect to the session daemon */
 295 restart:
 296         pthread_mutex_lock(&lttng_ust_comm_mutex);
 297
 298         if (lttng_ust_comm_should_quit) {
 299                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 300                 goto quit;
 301         }
 302
 303         if (sock_info->socket != -1) {
 304                 ret = close(sock_info->socket);
 305                 if (ret) {
 306                         ERR("Error closing %s apps socket", sock_info->name);
 307                 }
 308                 sock_info->socket = -1;
 309         }
 310
 311         /* Check for sessiond availability with pipe TODO */
 312
 313         /* Register */
 314         ret = lttcomm_connect_unix_sock(sock_info->sock_path);
 315         if (ret < 0) {
 316                 ERR("Error connecting to %s apps socket", sock_info->name);
 317                 /*
 318                  * If we cannot find the sessiond daemon, don't delay
 319                  * constructor execution.
 320                  */
 321                 ret = handle_register_done(sock_info);
 322                 assert(!ret);
 323                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 324                 sleep(5);
 325                 goto restart;
 326         }
 327
 328         sock_info->socket = sock = ret;
 329
 330         /*
 331          * Create only one root handle per listener thread for the whole
 332          * process lifetime.
 333          */
 334         if (sock_info->root_handle == -1) {
 335                 ret = lttng_abi_create_root_handle();
 336                 if (ret) {
 337                         ERR("Error creating root handle");
 338                         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 339                         goto quit;
 340                 }
 341                 sock_info->root_handle = ret;
 342         }
 343
 344         ret = register_app_to_sessiond(sock);
 345         if (ret < 0) {
 346                 ERR("Error registering to %s apps socket", sock_info->name);
 347                 /*
 348                  * If we cannot register to the sessiond daemon, don't
 349                  * delay constructor execution.
 350                  */
 351                 ret = handle_register_done(sock_info);
 352                 assert(!ret);
 353                 pthread_mutex_unlock(&lttng_ust_comm_mutex);
 354                 sleep(5);
 355                 goto restart;
 356         }
 357         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 358
 359         for (;;) {
 360                 ssize_t len;
 361                 struct lttcomm_ust_msg lum;
 362
 363                 len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
 364                 switch (len) {
 365                 case 0: /* orderly shutdown */
 366                         DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
 367                         goto end;
 368                 case sizeof(lum):
 369                         DBG("message received\n");
 370                         ret = handle_message(sock_info, sock, &lum);
 371                         if (ret < 0) {
 372                                 ERR("Error handling message for %s socket", sock_info->name);
 373                         }
 374                         continue;
 375                 case -1:
 376                         if (errno == ECONNRESET) {
 377                                 ERR("%s remote end closed connection\n", sock_info->name);
 378                                 goto end;
 379                         }
 380                         goto end;
 381                 default:
 382                         ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
 383                         continue;
 384                 }
 385
 386         }
 387 end:
 388         goto restart;   /* try to reconnect */
 389 quit:
 390         return NULL;
 391 }
 392
 393 /*
 394  * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 395  */
 396 static
 397 int get_timeout(struct timespec *constructor_timeout)
 398 {
 399         long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
 400         char *str_delay;
 401         int ret;
 402
 403         str_delay = getenv("UST_REGISTER_TIMEOUT");
 404         if (str_delay) {
 405                 constructor_delay_ms = strtol(str_delay, NULL, 10);
 406         }
 407
 408         switch (constructor_delay_ms) {
 409         case -1:/* fall-through */
 410         case 0:
 411                 return constructor_delay_ms;
 412         default:
 413                 break;
 414         }
 415
 416         /*
 417          * If we are unable to find the current time, don't wait.
 418          */
 419         ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
 420         if (ret) {
 421                 return -1;
 422         }
 423         constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
 424         constructor_timeout->tv_nsec +=
 425                 (constructor_delay_ms % 1000UL) * 1000000UL;
 426         if (constructor_timeout->tv_nsec >= 1000000000UL) {
 427                 constructor_timeout->tv_sec++;
 428                 constructor_timeout->tv_nsec -= 1000000000UL;
 429         }
 430         return 1;
 431 }
 432
 433 /*
 434  * sessiond monitoring thread: monitor presence of global and per-user
 435  * sessiond by polling the application common named pipe.
 436  */
 437 /* TODO */
 438
 439 void __attribute__((constructor)) lttng_ust_init(void)
 440 {
 441         struct timespec constructor_timeout;
 442         int timeout_mode;
 443         int ret;
 444
 445         if (uatomic_xchg(&initialized, 1) == 1)
 446                 return;
 447
 448         /*
 449          * We want precise control over the order in which we construct
 450          * our sub-libraries vs starting to receive commands from
 451          * sessiond (otherwise leading to errors when trying to create
 452          * sessiond before the init functions are completed).
 453          */
 454         init_usterr();
 455         init_tracepoint();
 456         ltt_ring_buffer_metadata_client_init();
 457         ltt_ring_buffer_client_overwrite_init();
 458         ltt_ring_buffer_client_discard_init();
 459
 460         timeout_mode = get_timeout(&constructor_timeout);
 461
 462         ret = sem_init(&constructor_wait, 0, 0);
 463         assert(!ret);
 464
 465         ret = setup_local_apps();
 466         if (ret) {
 467                 ERR("Error setting up to local apps");
 468         }
 469         ret = pthread_create(&local_apps.ust_listener, NULL,
 470                         ust_listener_thread, &local_apps);
 471
 472         if (local_apps.allowed) {
 473                 ret = pthread_create(&global_apps.ust_listener, NULL,
 474                                 ust_listener_thread, &global_apps);
 475         } else {
 476                 handle_register_done(&local_apps);
 477         }
 478
 479         switch (timeout_mode) {
 480         case 1: /* timeout wait */
 481                 do {
 482                         ret = sem_timedwait(&constructor_wait,
 483                                         &constructor_timeout);
 484                 } while (ret < 0 && errno == EINTR);
 485                 if (ret < 0 && errno == ETIMEDOUT) {
 486                         ERR("Timed out waiting for ltt-sessiond");
 487                 } else {
 488                         assert(!ret);
 489                 }
 490                 break;
 491         case -1:/* wait forever */
 492                 do {
 493                         ret = sem_wait(&constructor_wait);
 494                 } while (ret < 0 && errno == EINTR);
 495                 assert(!ret);
 496                 break;
 497         case 0: /* no timeout */
 498                 break;
 499         }
 500 }
 501
 502 void __attribute__((destructor)) lttng_ust_exit(void)
 503 {
 504         int ret;
 505
 506         /*
 507          * Using pthread_cancel here because:
 508          * A) we don't want to hang application teardown.
 509          * B) the thread is not allocating any resource.
 510          */
 511
 512         /*
 513          * Require the communication thread to quit. Synchronize with
 514          * mutexes to ensure it is not in a mutex critical section when
 515          * pthread_cancel is later called.
 516          */
 517         pthread_mutex_lock(&lttng_ust_comm_mutex);
 518         lttng_ust_comm_should_quit = 1;
 519         pthread_mutex_unlock(&lttng_ust_comm_mutex);
 520
 521         ret = pthread_cancel(global_apps.ust_listener);
 522         if (ret) {
 523                 ERR("Error cancelling global ust listener thread");
 524         }
 525
 526         cleanup_sock_info(&global_apps);
 527
 528         if (local_apps.allowed) {
 529                 ret = pthread_cancel(local_apps.ust_listener);
 530                 if (ret) {
 531                         ERR("Error cancelling local ust listener thread");
 532                 }
 533
 534                 cleanup_sock_info(&local_apps);
 535         }
 536
 537         lttng_ust_abi_exit();
 538         ltt_events_exit();
 539         ltt_ring_buffer_client_discard_exit();
 540         ltt_ring_buffer_client_overwrite_exit();
 541         ltt_ring_buffer_metadata_client_exit();
 542         exit_tracepoint();
 543 }