* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
+#define _LGPL_SOURCE
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/prctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include <assert.h>
#include <signal.h>
#include <urcu/uatomic.h>
+#include <urcu/futex.h>
#include <lttng-ust-comm.h>
#include <ust/usterr-signal-safe.h>
#include <ust/tracepoint.h>
#include <ust/tracepoint-internal.h>
#include <ust/ust.h>
+#include "ltt-tracer-core.h"
/*
* Has lttng ust comm constructor been called ?
*/
struct sock_info {
const char *name;
- char sock_path[PATH_MAX];
- int socket;
pthread_t ust_listener; /* listener thread */
int root_handle;
int constructor_sem_posted;
int allowed;
+ int global;
+
+ char sock_path[PATH_MAX];
+ int socket;
+
+ char wait_shm_path[PATH_MAX];
+ char *wait_shm_mmap;
};
/* Socket from app (connect) to session daemon (listen) for communication */
struct sock_info global_apps = {
.name = "global",
- .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
- .socket = -1,
+ .global = 1,
+
.root_handle = -1,
.allowed = 1,
+
+ .sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
+ .socket = -1,
+
+ .wait_shm_path = DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH,
};
/* TODO: allow global_apps_sock_path override */
struct sock_info local_apps = {
.name = "local",
- .socket = -1,
+ .global = 0,
.root_handle = -1,
.allowed = 0, /* Check setuid bit first */
+
+ .socket = -1,
};
extern void ltt_ring_buffer_client_overwrite_init(void);
int setup_local_apps(void)
{
const char *home_dir;
+ uid_t uid;
+ uid = getuid();
/*
* Disallow per-user tracing for setuid binaries.
*/
- if (getuid() != geteuid()) {
+ if (uid != geteuid()) {
local_apps.allowed = 0;
return 0;
} else {
return -ENOENT;
snprintf(local_apps.sock_path, PATH_MAX,
DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
+ snprintf(local_apps.wait_shm_path, PATH_MAX,
+ DEFAULT_HOME_APPS_WAIT_SHM_PATH, uid);
return 0;
}
if (sock_info->socket != -1) {
ret = close(sock_info->socket);
if (ret) {
- ERR("Error closing local apps socket");
+ ERR("Error closing apps socket");
}
sock_info->socket = -1;
}
}
sock_info->root_handle = -1;
}
+ sock_info->constructor_sem_posted = 0;
+ if (sock_info->wait_shm_mmap) {
+ ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
+ if (ret) {
+ ERR("Error unmapping wait shm");
+ }
+ sock_info->wait_shm_mmap = NULL;
+ }
+}
+
+/*
+ * Using fork to set umask in the child process (not multi-thread safe).
+ * We deal with the shm_open vs ftruncate race (happening when the
+ * sessiond owns the shm and does not let everybody modify it, to ensure
+ * safety against shm_unlink) by simply letting the mmap fail and
+ * retrying after a few seconds.
+ * For global shm, everybody has rw access to it until the sessiond
+ * starts.
+ */
+static
+int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
+{
+ int wait_shm_fd, ret;
+ pid_t pid;
+
+ /*
+ * Try to open read-only.
+ */
+ wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
+ if (wait_shm_fd >= 0) {
+ goto end;
+ } else if (wait_shm_fd < 0 && errno != ENOENT) {
+ /*
+ * Real-only open did not work, and it's not because the
+ * entry was not present. It's a failure that prohibits
+ * using shm.
+ */
+ ERR("Error opening shm %s", sock_info->wait_shm_path);
+ goto end;
+ }
+ /*
+ * If the open failed because the file did not exist, try
+ * creating it ourself.
+ */
+ pid = fork();
+ if (pid > 0) {
+ int status;
+
+ /*
+ * Parent: wait for child to return, in which case the
+ * shared memory map will have been created.
+ */
+ pid = wait(&status);
+ if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+ wait_shm_fd = -1;
+ goto end;
+ }
+ /*
+ * Try to open read-only again after creation.
+ */
+ wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
+ if (wait_shm_fd < 0) {
+ /*
+ * Real-only open did not work. It's a failure
+ * that prohibits using shm.
+ */
+ ERR("Error opening shm %s", sock_info->wait_shm_path);
+ goto end;
+ }
+ goto end;
+ } else if (pid == 0) {
+ int create_mode;
+
+ /* Child */
+ create_mode = S_IRUSR | S_IWUSR | S_IRGRP;
+ if (sock_info->global)
+ create_mode |= S_IROTH | S_IWGRP | S_IWOTH;
+ /*
+ * We're alone in a child process, so we can modify the
+ * process-wide umask.
+ */
+ umask(~create_mode);
+ /*
+ * Try creating shm (or get rw access).
+ * We don't do an exclusive open, because we allow other
+ * processes to create+ftruncate it concurrently.
+ */
+ wait_shm_fd = shm_open(sock_info->wait_shm_path,
+ O_RDWR | O_CREAT, create_mode);
+ if (wait_shm_fd >= 0) {
+ ret = ftruncate(wait_shm_fd, mmap_size);
+ if (ret) {
+ PERROR("ftruncate");
+ exit(EXIT_FAILURE);
+ }
+ exit(EXIT_SUCCESS);
+ }
+ /*
+ * For local shm, we need to have rw access to accept
+ * opening it: this means the local sessiond will be
+ * able to wake us up. For global shm, we open it even
+ * if rw access is not granted, because the root.root
+ * sessiond will be able to override all rights and wake
+ * us up.
+ */
+ if (!sock_info->global && errno != EACCES) {
+ ERR("Error opening shm %s", sock_info->wait_shm_path);
+ exit(EXIT_FAILURE);
+ }
+ /*
+ * The shm exists, but we cannot open it RW. Report
+ * success.
+ */
+ exit(EXIT_SUCCESS);
+ } else {
+ return -1;
+ }
+end:
+ if (wait_shm_fd >= 0 && !sock_info->global) {
+ struct stat statbuf;
+
+ /*
+ * Ensure that our user is the owner of the shm file for
+ * local shm. If we do not own the file, it means our
+ * sessiond will not have access to wake us up (there is
+ * probably a rogue process trying to fake our
+ * sessiond). Fallback to polling method in this case.
+ */
+ ret = fstat(wait_shm_fd, &statbuf);
+ if (ret) {
+ PERROR("fstat");
+ goto error_close;
+ }
+ if (statbuf.st_uid != getuid())
+ goto error_close;
+ }
+ return wait_shm_fd;
+
+error_close:
+ ret = close(wait_shm_fd);
+ if (ret) {
+ PERROR("Error closing fd");
+ }
+ return -1;
+}
+
+static
+char *get_map_shm(struct sock_info *sock_info)
+{
+ size_t mmap_size = sysconf(_SC_PAGE_SIZE);
+ int wait_shm_fd, ret;
+ char *wait_shm_mmap;
+
+ wait_shm_fd = get_wait_shm(sock_info, mmap_size);
+ if (wait_shm_fd < 0) {
+ goto error;
+ }
+ wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
+ MAP_SHARED, wait_shm_fd, 0);
+ /* close shm fd immediately after taking the mmap reference */
+ ret = close(wait_shm_fd);
+ if (ret) {
+ PERROR("Error closing fd");
+ }
+ if (wait_shm_mmap == MAP_FAILED) {
+ DBG("mmap error (can be caused by race with sessiond). Fallback to poll mode.");
+ goto error;
+ }
+ return wait_shm_mmap;
+
+error:
+ return NULL;
+}
+
+static
+void wait_for_sessiond(struct sock_info *sock_info)
+{
+ int ret;
+
+ ust_lock();
+ if (lttng_ust_comm_should_quit) {
+ goto quit;
+ }
+ if (!sock_info->wait_shm_mmap) {
+ sock_info->wait_shm_mmap = get_map_shm(sock_info);
+ if (!sock_info->wait_shm_mmap)
+ goto error;
+ }
+ ust_unlock();
+
+ DBG("Waiting for %s apps sessiond", sock_info->name);
+ /* Wait for futex wakeup */
+ if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
+ ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
+ FUTEX_WAIT, 0, NULL, NULL, 0);
+ /*
+ * FIXME: Currently, futexes on read-only shm seems to
+ * EFAULT.
+ */
+ if (ret < 0) {
+ PERROR("futex");
+ sleep(5);
+ }
+ }
+ return;
+
+quit:
+ ust_unlock();
+ return;
+
+error:
+ ust_unlock();
+ /* Error handling: fallback on a 5 seconds sleep. */
+ sleep(5);
+ return;
}
/*
sock_info->socket = -1;
}
- /* Check for sessiond availability with pipe TODO */
-
/* Register */
ret = lttcomm_connect_unix_sock(sock_info->sock_path);
if (ret < 0) {
ret = handle_register_done(sock_info);
assert(!ret);
ust_unlock();
- sleep(5);
+
+ /* Wait for sessiond availability with pipe */
+ wait_for_sessiond(sock_info);
goto restart;
}
ret = handle_register_done(sock_info);
assert(!ret);
ust_unlock();
- sleep(5);
+ wait_for_sessiond(sock_info);
goto restart;
}
ust_unlock();
/* Release urcu mutexes */
rcu_bp_after_fork_child();
lttng_ust_cleanup(0);
- lttng_ust_init();
/* Release mutexes and reenable signals */
ust_after_fork_common(fork_info);
+ lttng_ust_init();
}
projects / lttng-ust.git / blobdiff