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