--- /dev/null
+/*
+ * Copyright (C) 2016 - Aravind HT <aravind.ht@gmail.com>
+ * 2016 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#define _GNU_SOURCE
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/select.h>
+#include <sys/resource.h>
+#include <sys/time.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <urcu/compiler.h>
+#include <urcu/tls-compat.h>
+
+#include <ust-fd.h>
+#include <helper.h>
+#include <lttng/ust-error.h>
+#include <usterr-signal-safe.h>
+
+#include "../liblttng-ust/compat.h"
+
+/* Operations on the fd set. */
+#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)
+
+/* Check fd validity before calling these. */
+#define ADD_FD_TO_SET(fd, fd_sets) \
+ FD_SET(CALC_INDEX_TO_SET(fd), GET_FD_SET_FOR_FD(fd, fd_sets))
+#define IS_FD_SET(fd, fd_sets) \
+ FD_ISSET(CALC_INDEX_TO_SET(fd), GET_FD_SET_FOR_FD(fd, fd_sets))
+#define DEL_FD_FROM_SET(fd, fd_sets) \
+ FD_CLR(CALC_INDEX_TO_SET(fd), GET_FD_SET_FOR_FD(fd, fd_sets))
+
+/*
+ * 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.
+ */
+static pthread_mutex_t ust_safe_guard_fd_mutex = PTHREAD_MUTEX_INITIALIZER;
+/*
+ * Track whether we are within lttng-ust or application, for close
+ * system call override by LD_PRELOAD library.
+ */
+static DEFINE_URCU_TLS(int, thread_fd_tracking);
+
+/* 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;
+
+/*
+ * 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)));
+}
+
+/*
+ * Allocate the fd set array based on the hard limit set for this
+ * process. This will be called during the constructor execution
+ * and will also be called in the child after fork via lttng_ust_init.
+ */
+void lttng_ust_init_fd_tracker(void)
+{
+ struct rlimit rlim;
+ int i;
+
+ memset(&rlim, 0, sizeof(rlim));
+ /* Get the current possible max number of fd for this process. */
+ if (getrlimit(RLIMIT_NOFILE, &rlim) < 0)
+ abort();
+ /*
+ * FD set array size determined using the hard limit. Even if
+ * the process wishes to increase its limit using setrlimit, it
+ * can only do so with the softlimit which will be less than the
+ * hard limit.
+ */
+ lttng_ust_max_fd = rlim.rlim_max;
+ num_fd_sets = lttng_ust_max_fd / FD_SETSIZE;
+ if (lttng_ust_max_fd % FD_SETSIZE)
+ ++num_fd_sets;
+ if (lttng_fd_set != NULL) {
+ free(lttng_fd_set);
+ lttng_fd_set = NULL;
+ }
+ lttng_fd_set = malloc(num_fd_sets * (sizeof(fd_set)));
+ if (!lttng_fd_set)
+ abort();
+ for (i = 0; i < num_fd_sets; i++)
+ FD_ZERO((<tng_fd_set[i]));
+}
+
+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);
+}
+
+void lttng_ust_unlock_fd_tracker(void)
+{
+ pthread_mutex_unlock(&ust_safe_guard_fd_mutex);
+ /*
+ * 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;
+}
+
+/*
+ * Needs to be called with ust_safe_guard_fd_mutex held when opening the fd.
+ * Has strict checking of fd validity.
+ */
+void lttng_ust_add_fd_to_tracker(int fd)
+{
+ assert(URCU_TLS(thread_fd_tracking));
+ /* 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);
+}
+
+/*
+ * Needs to be called with ust_safe_guard_fd_mutex held when opening the fd.
+ * Has strict checking for fd validity.
+ */
+void lttng_ust_delete_fd_from_tracker(int fd)
+{
+ assert(URCU_TLS(thread_fd_tracking));
+ /* Not a valid fd. */
+ assert(IS_FD_VALID(fd));
+ /* Deleting an fd which was not set. */
+ assert(IS_FD_SET(fd, lttng_fd_set));
+
+ DEL_FD_FROM_SET(fd, lttng_fd_set);
+}
+
+/*
+ * Interface allowing applications to close arbitrary file descriptors.
+ * 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_close_fd(int fd, int (*close_cb)(int fd))
+{
+ int ret = 0;
+
+ lttng_ust_fixup_fd_tracker_tls();
+
+ /*
+ * 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))
+ return close_cb(fd);
+
+ lttng_ust_lock_fd_tracker();
+ if (IS_FD_VALID(fd) && IS_FD_SET(fd, lttng_fd_set)) {
+ ret = -1;
+ errno = EBADF;
+ } else {
+ ret = close_cb(fd);
+ }
+ lttng_ust_unlock_fd_tracker();
+
+ return ret;
+}
+
+#ifdef __OpenBSD__
+static void set_close_success(int *p)
+{
+ *p = 1;
+}
+static int test_close_success(const int *p)
+{
+ return *p;
+}
+#else
+static void set_close_success(int *p __attribute__((unused)))
+{
+}
+static int test_close_success(const int *p __attribute__((unused)))
+{
+ return 1;
+}
+#endif
+
+/*
+ * Implement helper for closefrom() override.
+ */
+int lttng_ust_safe_closefrom_fd(int lowfd, int (*close_cb)(int fd))
+{
+ int ret = 0, close_success = 0, i;
+
+ lttng_ust_fixup_fd_tracker_tls();
+
+ if (lowfd < 0) {
+ /*
+ * NetBSD return EBADF if fd is invalid.
+ */
+ errno = EBADF;
+ ret = -1;
+ goto end;
+ }
+ /*
+ * 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)) {
+ for (i = lowfd; i < lttng_ust_max_fd; i++) {
+ if (close_cb(i) < 0) {
+ switch (errno) {
+ case EBADF:
+ continue;
+ case EINTR:
+ default:
+ ret = -1;
+ goto end;
+ }
+ }
+ set_close_success(&close_success);
+ }
+ } else {
+ lttng_ust_lock_fd_tracker();
+ for (i = lowfd; i < lttng_ust_max_fd; i++) {
+ if (IS_FD_VALID(i) && IS_FD_SET(i, lttng_fd_set))
+ continue;
+ if (close_cb(i) < 0) {
+ switch (errno) {
+ case EBADF:
+ continue;
+ case EINTR:
+ default:
+ ret = -1;
+ lttng_ust_unlock_fd_tracker();
+ goto end;
+ }
+ }
+ set_close_success(&close_success);
+ }
+ lttng_ust_unlock_fd_tracker();
+ }
+ if (!test_close_success(&close_success)) {
+ /*
+ * OpenBSD return EBADF if fd is greater than all open
+ * file descriptors.
+ */
+ ret = -1;
+ errno = EBADF;
+ }
+end:
+ return ret;
+}
projects / lttng-ust.git / blobdiff