X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=liblttng-ust-comm%2Flttng-ust-fd-tracker.c;h=9659f349e54ac85a3afad50b2cfc2055abcfacfc;hb=793d29c9367a58c2a368bc1ccb11b01c2d2bdac2;hp=5a763ff2960550c094306d9d7d90de3d2bf9d037;hpb=6548fca464f68be5ded73be6b9a479daf08e62d6;p=lttng-ust.git diff --git a/liblttng-ust-comm/lttng-ust-fd-tracker.c b/liblttng-ust-comm/lttng-ust-fd-tracker.c index 5a763ff2..9659f349 100644 --- a/liblttng-ust-comm/lttng-ust-fd-tracker.c +++ b/liblttng-ust-comm/lttng-ust-fd-tracker.c @@ -32,8 +32,11 @@ #include #include #include +#include +#include #include #include +#include #include #include @@ -46,6 +49,7 @@ #define IS_FD_VALID(fd) ((fd) >= 0 && (fd) < lttng_ust_max_fd) #define GET_FD_SET_FOR_FD(fd, fd_sets) (&((fd_sets)[(fd) / FD_SETSIZE])) #define CALC_INDEX_TO_SET(fd) ((fd) % FD_SETSIZE) +#define IS_FD_STD(fd) (IS_FD_VALID(fd) && (fd) <= STDERR_FILENO) /* Check fd validity before calling these. */ #define ADD_FD_TO_SET(fd, fd_sets) \ @@ -59,25 +63,38 @@ * Protect the lttng_fd_set. Nests within the ust_lock, and therefore * within the libc dl lock. Therefore, we need to fixup the TLS before * nesting into this lock. + * + * The ust_safe_guard_fd_mutex nests within the ust_mutex. This mutex + * is also held across fork. */ static pthread_mutex_t ust_safe_guard_fd_mutex = PTHREAD_MUTEX_INITIALIZER; + +/* + * Cancel state when grabbing the ust_safe_guard_fd_mutex. Saved when + * locking, restored on unlock. Protected by ust_safe_guard_fd_mutex. + */ +static int ust_safe_guard_saved_cancelstate; + /* * Track whether we are within lttng-ust or application, for close - * system call override by LD_PRELOAD library. + * system call override by LD_PRELOAD library. This also tracks whether + * we are invoking close() from a signal handler nested on an + * application thread. */ -static DEFINE_URCU_TLS(int, thread_fd_tracking); +static DEFINE_URCU_TLS(int, ust_fd_mutex_nest); /* fd_set used to book keep fd being used by lttng-ust. */ static fd_set *lttng_fd_set; static int lttng_ust_max_fd; static int num_fd_sets; +static int init_done; /* * Force a read (imply TLS fixup for dlopen) of TLS variables. */ void lttng_ust_fixup_fd_tracker_tls(void) { - asm volatile ("" : : "m" (URCU_TLS(thread_fd_tracking))); + asm volatile ("" : : "m" (URCU_TLS(ust_fd_mutex_nest))); } /* @@ -90,6 +107,9 @@ void lttng_ust_init_fd_tracker(void) struct rlimit rlim; int i; + if (CMM_LOAD_SHARED(init_done)) + return; + memset(&rlim, 0, sizeof(rlim)); /* Get the current possible max number of fd for this process. */ if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) @@ -113,43 +133,177 @@ void lttng_ust_init_fd_tracker(void) abort(); for (i = 0; i < num_fd_sets; i++) FD_ZERO((<tng_fd_set[i])); + CMM_STORE_SHARED(init_done, 1); } void lttng_ust_lock_fd_tracker(void) { - URCU_TLS(thread_fd_tracking) = 1; - /* - * Ensure the compiler don't move the store after the close() - * call in case close() would be marked as leaf. - */ - cmm_barrier(); - pthread_mutex_lock(&ust_safe_guard_fd_mutex); + sigset_t sig_all_blocked, orig_mask; + int ret, oldstate; + + ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate); + if (ret) { + ERR("pthread_setcancelstate: %s", strerror(ret)); + } + sigfillset(&sig_all_blocked); + ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask); + if (ret) { + ERR("pthread_sigmask: %s", strerror(ret)); + } + if (!URCU_TLS(ust_fd_mutex_nest)++) { + /* + * Ensure the compiler don't move the store after the close() + * call in case close() would be marked as leaf. + */ + cmm_barrier(); + pthread_mutex_lock(&ust_safe_guard_fd_mutex); + ust_safe_guard_saved_cancelstate = oldstate; + } + ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL); + if (ret) { + ERR("pthread_sigmask: %s", strerror(ret)); + } } void lttng_ust_unlock_fd_tracker(void) { - pthread_mutex_unlock(&ust_safe_guard_fd_mutex); + sigset_t sig_all_blocked, orig_mask; + int ret, newstate, oldstate; + bool restore_cancel = false; + + sigfillset(&sig_all_blocked); + ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask); + if (ret) { + ERR("pthread_sigmask: %s", strerror(ret)); + } /* * Ensure the compiler don't move the store before the close() * call, in case close() would be marked as leaf. */ cmm_barrier(); - URCU_TLS(thread_fd_tracking) = 0; + if (!--URCU_TLS(ust_fd_mutex_nest)) { + newstate = ust_safe_guard_saved_cancelstate; + restore_cancel = true; + pthread_mutex_unlock(&ust_safe_guard_fd_mutex); + } + ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL); + if (ret) { + ERR("pthread_sigmask: %s", strerror(ret)); + } + if (restore_cancel) { + ret = pthread_setcancelstate(newstate, &oldstate); + if (ret) { + ERR("pthread_setcancelstate: %s", strerror(ret)); + } + } +} + +static int dup_std_fd(int fd) +{ + int ret, i; + int fd_to_close[STDERR_FILENO + 1]; + int fd_to_close_count = 0; + int dup_cmd = F_DUPFD; /* Default command */ + int fd_valid = -1; + + if (!(IS_FD_STD(fd))) { + /* Should not be here */ + ret = -1; + goto error; + } + + /* Check for FD_CLOEXEC flag */ + ret = fcntl(fd, F_GETFD); + if (ret < 0) { + PERROR("fcntl on f_getfd"); + ret = -1; + goto error; + } + + if (ret & FD_CLOEXEC) { + dup_cmd = F_DUPFD_CLOEXEC; + } + + /* Perform dup */ + for (i = 0; i < STDERR_FILENO + 1; i++) { + ret = fcntl(fd, dup_cmd, 0); + if (ret < 0) { + PERROR("fcntl dup fd"); + goto error; + } + + if (!(IS_FD_STD(ret))) { + /* fd is outside of STD range, use it. */ + fd_valid = ret; + /* Close fd received as argument. */ + fd_to_close[i] = fd; + fd_to_close_count++; + break; + } + + fd_to_close[i] = ret; + fd_to_close_count++; + } + + /* Close intermediary fds */ + for (i = 0; i < fd_to_close_count; i++) { + ret = close(fd_to_close[i]); + if (ret) { + PERROR("close on temporary fd: %d.", fd_to_close[i]); + /* + * Not using an abort here would yield a complicated + * error handling for the caller. If a failure occurs + * here, the system is already in a bad state. + */ + abort(); + } + } + + ret = fd_valid; +error: + return ret; } /* * Needs to be called with ust_safe_guard_fd_mutex held when opening the fd. * Has strict checking of fd validity. + * + * If fd <= 2, dup the fd until fd > 2. This enables us to bypass + * problems that can be encountered if UST uses stdin, stdout, stderr + * fds for internal use (daemon etc.). This can happen if the + * application closes either of those file descriptors. Intermediary fds + * are closed as needed. + * + * Return -1 on error. + * */ -void lttng_ust_add_fd_to_tracker(int fd) +int lttng_ust_add_fd_to_tracker(int fd) { - assert(URCU_TLS(thread_fd_tracking)); + int ret; + /* + * Ensure the tracker is initialized when called from + * constructors. + */ + lttng_ust_init_fd_tracker(); + assert(URCU_TLS(ust_fd_mutex_nest)); + + if (IS_FD_STD(fd)) { + ret = dup_std_fd(fd); + if (ret < 0) { + goto error; + } + fd = ret; + } + /* Trying to add an fd which we can not accommodate. */ assert(IS_FD_VALID(fd)); /* Setting an fd thats already set. */ assert(!IS_FD_SET(fd, lttng_fd_set)); ADD_FD_TO_SET(fd, lttng_fd_set); + return fd; +error: + return ret; } /* @@ -158,7 +312,13 @@ void lttng_ust_add_fd_to_tracker(int fd) */ void lttng_ust_delete_fd_from_tracker(int fd) { - assert(URCU_TLS(thread_fd_tracking)); + /* + * Ensure the tracker is initialized when called from + * constructors. + */ + lttng_ust_init_fd_tracker(); + + assert(URCU_TLS(ust_fd_mutex_nest)); /* Not a valid fd. */ assert(IS_FD_VALID(fd)); /* Deleting an fd which was not set. */ @@ -178,11 +338,17 @@ int lttng_ust_safe_close_fd(int fd, int (*close_cb)(int fd)) lttng_ust_fixup_fd_tracker_tls(); + /* + * Ensure the tracker is initialized when called from + * constructors. + */ + lttng_ust_init_fd_tracker(); + /* * If called from lttng-ust, we directly call close without * validating whether the FD is part of the tracked set. */ - if (URCU_TLS(thread_fd_tracking)) + if (URCU_TLS(ust_fd_mutex_nest)) return close_cb(fd); lttng_ust_lock_fd_tracker(); @@ -197,6 +363,44 @@ int lttng_ust_safe_close_fd(int fd, int (*close_cb)(int fd)) return ret; } +/* + * Interface allowing applications to close arbitrary streams. + * We check if it is owned by lttng-ust, and return -1, errno=EBADF + * instead of closing it if it is the case. + */ +int lttng_ust_safe_fclose_stream(FILE *stream, int (*fclose_cb)(FILE *stream)) +{ + int ret = 0, fd; + + lttng_ust_fixup_fd_tracker_tls(); + + /* + * Ensure the tracker is initialized when called from + * constructors. + */ + lttng_ust_init_fd_tracker(); + + /* + * If called from lttng-ust, we directly call fclose without + * validating whether the FD is part of the tracked set. + */ + if (URCU_TLS(ust_fd_mutex_nest)) + return fclose_cb(stream); + + fd = fileno(stream); + + lttng_ust_lock_fd_tracker(); + if (IS_FD_VALID(fd) && IS_FD_SET(fd, lttng_fd_set)) { + ret = -1; + errno = EBADF; + } else { + ret = fclose_cb(stream); + } + lttng_ust_unlock_fd_tracker(); + + return ret; +} + #ifdef __OpenBSD__ static void set_close_success(int *p) { @@ -225,6 +429,12 @@ int lttng_ust_safe_closefrom_fd(int lowfd, int (*close_cb)(int fd)) lttng_ust_fixup_fd_tracker_tls(); + /* + * Ensure the tracker is initialized when called from + * constructors. + */ + lttng_ust_init_fd_tracker(); + if (lowfd < 0) { /* * NetBSD return EBADF if fd is invalid. @@ -237,7 +447,7 @@ int lttng_ust_safe_closefrom_fd(int lowfd, int (*close_cb)(int fd)) * If called from lttng-ust, we directly call close without * validating whether the FD is part of the tracked set. */ - if (URCU_TLS(thread_fd_tracking)) { + if (URCU_TLS(ust_fd_mutex_nest)) { for (i = lowfd; i < lttng_ust_max_fd; i++) { if (close_cb(i) < 0) { switch (errno) {