4 * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
5 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
23 #include <sys/types.h>
24 #include <sys/socket.h>
25 #include <sys/prctl.h>
28 #include <sys/types.h>
34 #include <semaphore.h>
38 #include <urcu/uatomic.h>
39 #include <urcu/futex.h>
41 #include <lttng-ust-comm.h>
42 #include <ust/usterr-signal-safe.h>
43 #include <ust/lttng-ust-abi.h>
44 #include <ust/tracepoint.h>
45 #include <ust/tracepoint-internal.h>
47 #include "ltt-tracer-core.h"
50 * Has lttng ust comm constructor been called ?
52 static int initialized
;
55 * The ust_lock/ust_unlock lock is used as a communication thread mutex.
56 * Held when handling a command, also held by fork() to deal with
57 * removal of threads, and by exit path.
60 /* Should the ust comm thread quit ? */
61 static int lttng_ust_comm_should_quit
;
64 * Wait for either of these before continuing to the main
66 * - the register_done message from sessiond daemon
67 * (will let the sessiond daemon enable sessions before main
69 * - sessiond daemon is not reachable.
70 * - timeout (ensuring applications are resilient to session
73 static sem_t constructor_wait
;
75 * Doing this for both the global and local sessiond.
77 static int sem_count
= { 2 };
80 * Info about socket and associated listener thread.
84 pthread_t ust_listener
; /* listener thread */
86 int constructor_sem_posted
;
90 char sock_path
[PATH_MAX
];
93 char wait_shm_path
[PATH_MAX
];
97 /* Socket from app (connect) to session daemon (listen) for communication */
98 struct sock_info global_apps
= {
105 .sock_path
= DEFAULT_GLOBAL_APPS_UNIX_SOCK
,
108 .wait_shm_path
= DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH
,
111 /* TODO: allow global_apps_sock_path override */
113 struct sock_info local_apps
= {
117 .allowed
= 0, /* Check setuid bit first */
122 static int wait_poll_fallback
;
124 extern void ltt_ring_buffer_client_overwrite_init(void);
125 extern void ltt_ring_buffer_client_discard_init(void);
126 extern void ltt_ring_buffer_metadata_client_init(void);
127 extern void ltt_ring_buffer_client_overwrite_exit(void);
128 extern void ltt_ring_buffer_client_discard_exit(void);
129 extern void ltt_ring_buffer_metadata_client_exit(void);
132 int setup_local_apps(void)
134 const char *home_dir
;
139 * Disallow per-user tracing for setuid binaries.
141 if (uid
!= geteuid()) {
142 local_apps
.allowed
= 0;
145 local_apps
.allowed
= 1;
147 home_dir
= (const char *) getenv("HOME");
150 snprintf(local_apps
.sock_path
, PATH_MAX
,
151 DEFAULT_HOME_APPS_UNIX_SOCK
, home_dir
);
152 snprintf(local_apps
.wait_shm_path
, PATH_MAX
,
153 DEFAULT_HOME_APPS_WAIT_SHM_PATH
, uid
);
158 int register_app_to_sessiond(int socket
)
169 char name
[16]; /* process name */
172 reg_msg
.major
= LTTNG_UST_COMM_VERSION_MAJOR
;
173 reg_msg
.minor
= LTTNG_UST_COMM_VERSION_MINOR
;
174 reg_msg
.pid
= getpid();
175 reg_msg
.ppid
= getppid();
176 reg_msg
.uid
= getuid();
177 reg_msg
.gid
= getgid();
178 prctl_ret
= prctl(PR_GET_NAME
, (unsigned long) reg_msg
.name
, 0, 0, 0);
180 ERR("Error executing prctl");
184 ret
= lttcomm_send_unix_sock(socket
, ®_msg
, sizeof(reg_msg
));
185 if (ret
>= 0 && ret
!= sizeof(reg_msg
))
191 int send_reply(int sock
, struct lttcomm_ust_reply
*lur
)
195 len
= lttcomm_send_unix_sock(sock
, lur
, sizeof(*lur
));
198 DBG("message successfully sent");
201 if (errno
== ECONNRESET
) {
202 printf("remote end closed connection\n");
207 printf("incorrect message size: %zd\n", len
);
213 int handle_register_done(struct sock_info
*sock_info
)
217 if (sock_info
->constructor_sem_posted
)
219 sock_info
->constructor_sem_posted
= 1;
220 if (uatomic_read(&sem_count
) <= 0) {
223 ret
= uatomic_add_return(&sem_count
, -1);
225 ret
= sem_post(&constructor_wait
);
232 int handle_message(struct sock_info
*sock_info
,
233 int sock
, struct lttcomm_ust_msg
*lum
)
236 const struct objd_ops
*ops
;
237 struct lttcomm_ust_reply lur
;
241 memset(&lur
, 0, sizeof(lur
));
243 if (lttng_ust_comm_should_quit
) {
248 ops
= objd_ops(lum
->handle
);
255 case LTTNG_UST_REGISTER_DONE
:
256 if (lum
->handle
== LTTNG_UST_ROOT_HANDLE
)
257 ret
= handle_register_done(sock_info
);
261 case LTTNG_UST_RELEASE
:
262 if (lum
->handle
== LTTNG_UST_ROOT_HANDLE
)
265 ret
= objd_unref(lum
->handle
);
269 ret
= ops
->cmd(lum
->handle
, lum
->cmd
,
270 (unsigned long) &lum
->u
);
277 lur
.handle
= lum
->handle
;
281 lur
.ret_code
= LTTCOMM_OK
;
283 lur
.ret_code
= LTTCOMM_SESSION_FAIL
;
285 ret
= send_reply(sock
, &lur
);
292 void cleanup_sock_info(struct sock_info
*sock_info
)
296 if (sock_info
->socket
!= -1) {
297 ret
= close(sock_info
->socket
);
299 ERR("Error closing apps socket");
301 sock_info
->socket
= -1;
303 if (sock_info
->root_handle
!= -1) {
304 ret
= objd_unref(sock_info
->root_handle
);
306 ERR("Error unref root handle");
308 sock_info
->root_handle
= -1;
310 sock_info
->constructor_sem_posted
= 0;
311 if (sock_info
->wait_shm_mmap
) {
312 ret
= munmap(sock_info
->wait_shm_mmap
, sysconf(_SC_PAGE_SIZE
));
314 ERR("Error unmapping wait shm");
316 sock_info
->wait_shm_mmap
= NULL
;
321 * Using fork to set umask in the child process (not multi-thread safe).
322 * We deal with the shm_open vs ftruncate race (happening when the
323 * sessiond owns the shm and does not let everybody modify it, to ensure
324 * safety against shm_unlink) by simply letting the mmap fail and
325 * retrying after a few seconds.
326 * For global shm, everybody has rw access to it until the sessiond
330 int get_wait_shm(struct sock_info
*sock_info
, size_t mmap_size
)
332 int wait_shm_fd
, ret
;
336 * Try to open read-only.
338 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
, O_RDONLY
, 0);
339 if (wait_shm_fd
>= 0) {
341 } else if (wait_shm_fd
< 0 && errno
!= ENOENT
) {
343 * Real-only open did not work, and it's not because the
344 * entry was not present. It's a failure that prohibits
347 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
351 * If the open failed because the file did not exist, try
352 * creating it ourself.
359 * Parent: wait for child to return, in which case the
360 * shared memory map will have been created.
363 if (!WIFEXITED(status
) || WEXITSTATUS(status
) != 0) {
368 * Try to open read-only again after creation.
370 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
, O_RDONLY
, 0);
371 if (wait_shm_fd
< 0) {
373 * Real-only open did not work. It's a failure
374 * that prohibits using shm.
376 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
380 } else if (pid
== 0) {
384 create_mode
= S_IRUSR
| S_IWUSR
| S_IRGRP
;
385 if (sock_info
->global
)
386 create_mode
|= S_IROTH
| S_IWGRP
| S_IWOTH
;
388 * We're alone in a child process, so we can modify the
389 * process-wide umask.
393 * Try creating shm (or get rw access).
394 * We don't do an exclusive open, because we allow other
395 * processes to create+ftruncate it concurrently.
397 wait_shm_fd
= shm_open(sock_info
->wait_shm_path
,
398 O_RDWR
| O_CREAT
, create_mode
);
399 if (wait_shm_fd
>= 0) {
400 ret
= ftruncate(wait_shm_fd
, mmap_size
);
408 * For local shm, we need to have rw access to accept
409 * opening it: this means the local sessiond will be
410 * able to wake us up. For global shm, we open it even
411 * if rw access is not granted, because the root.root
412 * sessiond will be able to override all rights and wake
415 if (!sock_info
->global
&& errno
!= EACCES
) {
416 ERR("Error opening shm %s", sock_info
->wait_shm_path
);
420 * The shm exists, but we cannot open it RW. Report
428 if (wait_shm_fd
>= 0 && !sock_info
->global
) {
432 * Ensure that our user is the owner of the shm file for
433 * local shm. If we do not own the file, it means our
434 * sessiond will not have access to wake us up (there is
435 * probably a rogue process trying to fake our
436 * sessiond). Fallback to polling method in this case.
438 ret
= fstat(wait_shm_fd
, &statbuf
);
443 if (statbuf
.st_uid
!= getuid())
449 ret
= close(wait_shm_fd
);
451 PERROR("Error closing fd");
457 char *get_map_shm(struct sock_info
*sock_info
)
459 size_t mmap_size
= sysconf(_SC_PAGE_SIZE
);
460 int wait_shm_fd
, ret
;
463 wait_shm_fd
= get_wait_shm(sock_info
, mmap_size
);
464 if (wait_shm_fd
< 0) {
467 wait_shm_mmap
= mmap(NULL
, mmap_size
, PROT_READ
,
468 MAP_SHARED
, wait_shm_fd
, 0);
469 /* close shm fd immediately after taking the mmap reference */
470 ret
= close(wait_shm_fd
);
472 PERROR("Error closing fd");
474 if (wait_shm_mmap
== MAP_FAILED
) {
475 DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
478 return wait_shm_mmap
;
485 void wait_for_sessiond(struct sock_info
*sock_info
)
490 if (lttng_ust_comm_should_quit
) {
493 if (wait_poll_fallback
) {
496 if (!sock_info
->wait_shm_mmap
) {
497 sock_info
->wait_shm_mmap
= get_map_shm(sock_info
);
498 if (!sock_info
->wait_shm_mmap
)
503 DBG("Waiting for %s apps sessiond", sock_info
->name
);
504 /* Wait for futex wakeup */
505 if (uatomic_read((int32_t *) sock_info
->wait_shm_mmap
) == 0) {
506 ret
= futex_async((int32_t *) sock_info
->wait_shm_mmap
,
507 FUTEX_WAIT
, 0, NULL
, NULL
, 0);
509 if (errno
== EFAULT
) {
510 wait_poll_fallback
= 1;
512 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
513 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
514 "Please upgrade your kernel "
515 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
516 "mainline). LTTng-UST will use polling mode fallback.");
533 * This thread does not allocate any resource, except within
534 * handle_message, within mutex protection. This mutex protects against
536 * The other moment it allocates resources is at socket connexion, which
537 * is also protected by the mutex.
540 void *ust_listener_thread(void *arg
)
542 struct sock_info
*sock_info
= arg
;
543 int sock
, ret
, prev_connect_failed
= 0, has_waited
= 0;
545 /* Restart trying to connect to the session daemon */
547 if (prev_connect_failed
) {
548 /* Wait for sessiond availability with pipe */
549 wait_for_sessiond(sock_info
);
553 * Sleep for 5 seconds before retrying after a
554 * sequence of failure / wait / failure. This
555 * deals with a killed or broken session daemon.
560 prev_connect_failed
= 0;
564 if (lttng_ust_comm_should_quit
) {
569 if (sock_info
->socket
!= -1) {
570 ret
= close(sock_info
->socket
);
572 ERR("Error closing %s apps socket", sock_info
->name
);
574 sock_info
->socket
= -1;
578 ret
= lttcomm_connect_unix_sock(sock_info
->sock_path
);
580 ERR("Error connecting to %s apps socket", sock_info
->name
);
581 prev_connect_failed
= 1;
583 * If we cannot find the sessiond daemon, don't delay
584 * constructor execution.
586 ret
= handle_register_done(sock_info
);
592 sock_info
->socket
= sock
= ret
;
595 * Create only one root handle per listener thread for the whole
598 if (sock_info
->root_handle
== -1) {
599 ret
= lttng_abi_create_root_handle();
601 ERR("Error creating root handle");
605 sock_info
->root_handle
= ret
;
608 ret
= register_app_to_sessiond(sock
);
610 ERR("Error registering to %s apps socket", sock_info
->name
);
611 prev_connect_failed
= 1;
613 * If we cannot register to the sessiond daemon, don't
614 * delay constructor execution.
616 ret
= handle_register_done(sock_info
);
625 struct lttcomm_ust_msg lum
;
627 len
= lttcomm_recv_unix_sock(sock
, &lum
, sizeof(lum
));
629 case 0: /* orderly shutdown */
630 DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info
->name
);
633 DBG("message received\n");
634 ret
= handle_message(sock_info
, sock
, &lum
);
636 ERR("Error handling message for %s socket", sock_info
->name
);
640 if (errno
== ECONNRESET
) {
641 ERR("%s remote end closed connection\n", sock_info
->name
);
646 ERR("incorrect message size (%s socket): %zd\n", sock_info
->name
, len
);
652 goto restart
; /* try to reconnect */
658 * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
661 int get_timeout(struct timespec
*constructor_timeout
)
663 long constructor_delay_ms
= LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS
;
667 str_delay
= getenv("UST_REGISTER_TIMEOUT");
669 constructor_delay_ms
= strtol(str_delay
, NULL
, 10);
672 switch (constructor_delay_ms
) {
673 case -1:/* fall-through */
675 return constructor_delay_ms
;
681 * If we are unable to find the current time, don't wait.
683 ret
= clock_gettime(CLOCK_REALTIME
, constructor_timeout
);
687 constructor_timeout
->tv_sec
+= constructor_delay_ms
/ 1000UL;
688 constructor_timeout
->tv_nsec
+=
689 (constructor_delay_ms
% 1000UL) * 1000000UL;
690 if (constructor_timeout
->tv_nsec
>= 1000000000UL) {
691 constructor_timeout
->tv_sec
++;
692 constructor_timeout
->tv_nsec
-= 1000000000UL;
698 * sessiond monitoring thread: monitor presence of global and per-user
699 * sessiond by polling the application common named pipe.
703 void __attribute__((constructor
)) lttng_ust_init(void)
705 struct timespec constructor_timeout
;
709 if (uatomic_xchg(&initialized
, 1) == 1)
713 * We want precise control over the order in which we construct
714 * our sub-libraries vs starting to receive commands from
715 * sessiond (otherwise leading to errors when trying to create
716 * sessiond before the init functions are completed).
720 ltt_ring_buffer_metadata_client_init();
721 ltt_ring_buffer_client_overwrite_init();
722 ltt_ring_buffer_client_discard_init();
724 timeout_mode
= get_timeout(&constructor_timeout
);
726 ret
= sem_init(&constructor_wait
, 0, 0);
729 ret
= setup_local_apps();
731 ERR("Error setting up to local apps");
733 ret
= pthread_create(&local_apps
.ust_listener
, NULL
,
734 ust_listener_thread
, &local_apps
);
736 if (local_apps
.allowed
) {
737 ret
= pthread_create(&global_apps
.ust_listener
, NULL
,
738 ust_listener_thread
, &global_apps
);
740 handle_register_done(&local_apps
);
743 switch (timeout_mode
) {
744 case 1: /* timeout wait */
746 ret
= sem_timedwait(&constructor_wait
,
747 &constructor_timeout
);
748 } while (ret
< 0 && errno
== EINTR
);
749 if (ret
< 0 && errno
== ETIMEDOUT
) {
750 ERR("Timed out waiting for ltt-sessiond");
755 case -1:/* wait forever */
757 ret
= sem_wait(&constructor_wait
);
758 } while (ret
< 0 && errno
== EINTR
);
761 case 0: /* no timeout */
767 void lttng_ust_cleanup(int exiting
)
769 cleanup_sock_info(&global_apps
);
770 if (local_apps
.allowed
) {
771 cleanup_sock_info(&local_apps
);
773 lttng_ust_abi_exit();
775 ltt_ring_buffer_client_discard_exit();
776 ltt_ring_buffer_client_overwrite_exit();
777 ltt_ring_buffer_metadata_client_exit();
780 /* Reinitialize values for fork */
782 lttng_ust_comm_should_quit
= 0;
787 void __attribute__((destructor
)) lttng_ust_exit(void)
792 * Using pthread_cancel here because:
793 * A) we don't want to hang application teardown.
794 * B) the thread is not allocating any resource.
798 * Require the communication thread to quit. Synchronize with
799 * mutexes to ensure it is not in a mutex critical section when
800 * pthread_cancel is later called.
803 lttng_ust_comm_should_quit
= 1;
806 ret
= pthread_cancel(global_apps
.ust_listener
);
808 ERR("Error cancelling global ust listener thread");
810 if (local_apps
.allowed
) {
811 ret
= pthread_cancel(local_apps
.ust_listener
);
813 ERR("Error cancelling local ust listener thread");
816 lttng_ust_cleanup(1);
820 * We exclude the worker threads across fork and clone (except
821 * CLONE_VM), because these system calls only keep the forking thread
822 * running in the child. Therefore, we don't want to call fork or clone
823 * in the middle of an tracepoint or ust tracing state modification.
824 * Holding this mutex protects these structures across fork and clone.
826 void ust_before_fork(ust_fork_info_t
*fork_info
)
829 * Disable signals. This is to avoid that the child intervenes
830 * before it is properly setup for tracing. It is safer to
831 * disable all signals, because then we know we are not breaking
832 * anything by restoring the original mask.
837 /* Disable signals */
838 sigfillset(&all_sigs
);
839 ret
= sigprocmask(SIG_BLOCK
, &all_sigs
, &fork_info
->orig_sigs
);
841 PERROR("sigprocmask");
844 rcu_bp_before_fork();
847 static void ust_after_fork_common(ust_fork_info_t
*fork_info
)
851 DBG("process %d", getpid());
853 /* Restore signals */
854 ret
= sigprocmask(SIG_SETMASK
, &fork_info
->orig_sigs
, NULL
);
856 PERROR("sigprocmask");
860 void ust_after_fork_parent(ust_fork_info_t
*fork_info
)
862 DBG("process %d", getpid());
863 rcu_bp_after_fork_parent();
864 /* Release mutexes and reenable signals */
865 ust_after_fork_common(fork_info
);
869 * After fork, in the child, we need to cleanup all the leftover state,
870 * except the worker thread which already magically disappeared thanks
871 * to the weird Linux fork semantics. After tyding up, we call
872 * lttng_ust_init() again to start over as a new PID.
874 * This is meant for forks() that have tracing in the child between the
875 * fork and following exec call (if there is any).
877 void ust_after_fork_child(ust_fork_info_t
*fork_info
)
879 DBG("process %d", getpid());
880 /* Release urcu mutexes */
881 rcu_bp_after_fork_child();
882 lttng_ust_cleanup(0);
883 /* Release mutexes and reenable signals */
884 ust_after_fork_common(fork_info
);