wlroots/xwayland/server.c

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C
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#define _POSIX_C_SOURCE 200809L
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>
#include <wayland-server-core.h>
#include <wlr/util/log.h>
#include <wlr/xwayland.h>
#include "sockets.h"
#include "util/signal.h"
#include "xwayland/config.h"
static void safe_close(int fd) {
if (fd >= 0) {
close(fd);
}
}
noreturn static void exec_xwayland(struct wlr_xwayland_server *server) {
if (!set_cloexec(server->x_fd[0], false) ||
!set_cloexec(server->x_fd[1], false) ||
!set_cloexec(server->wl_fd[1], false)) {
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wlr_log(WLR_ERROR, "Failed to unset CLOEXEC on FD");
_exit(EXIT_FAILURE);
}
if (server->options.enable_wm && !set_cloexec(server->wm_fd[1], false)) {
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wlr_log(WLR_ERROR, "Failed to unset CLOEXEC on FD");
_exit(EXIT_FAILURE);
}
/* Make Xwayland signal us when it's ready */
/* TODO: can we use -displayfd instead? */
signal(SIGUSR1, SIG_IGN);
char *argv[64] = {0};
size_t i = 0;
char listenfd0[16], listenfd1[16];
snprintf(listenfd0, sizeof(listenfd0), "%d", server->x_fd[0]);
snprintf(listenfd1, sizeof(listenfd1), "%d", server->x_fd[1]);
argv[i++] = "Xwayland";
argv[i++] = server->display_name;
argv[i++] = "-rootless";
argv[i++] = "-terminate";
argv[i++] = "-core";
#if HAVE_XWAYLAND_LISTENFD
argv[i++] = "-listenfd";
argv[i++] = listenfd0;
argv[i++] = "-listenfd";
argv[i++] = listenfd1;
#else
argv[i++] = "-listen";
argv[i++] = listenfd0;
argv[i++] = "-listen";
argv[i++] = listenfd1;
#endif
char wmfd[16];
if (server->options.enable_wm) {
snprintf(wmfd, sizeof(wmfd), "%d", server->wm_fd[1]);
argv[i++] = "-wm";
argv[i++] = wmfd;
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}
#if HAVE_XWAYLAND_NO_TOUCH_POINTER_EMULATION
if (server->options.no_touch_pointer_emulation) {
argv[i++] = "-noTouchPointerEmulation";
}
#else
server->options.no_touch_pointer_emulation = false;
#endif
argv[i++] = NULL;
assert(i < sizeof(argv) / sizeof(argv[0]));
char wayland_socket_str[16];
snprintf(wayland_socket_str, sizeof(wayland_socket_str), "%d", server->wl_fd[1]);
setenv("WAYLAND_SOCKET", wayland_socket_str, true);
wlr_log(WLR_INFO, "Starting Xwayland on :%d", server->display);
// Closes stdout/stderr depending on log verbosity
enum wlr_log_importance verbosity = wlr_log_get_verbosity();
int devnull = open("/dev/null", O_WRONLY | O_CREAT | O_CLOEXEC, 0666);
if (devnull < 0) {
wlr_log_errno(WLR_ERROR, "XWayland: failed to open /dev/null");
_exit(EXIT_FAILURE);
}
if (verbosity < WLR_INFO) {
dup2(devnull, STDOUT_FILENO);
}
if (verbosity < WLR_ERROR) {
dup2(devnull, STDERR_FILENO);
}
const char *xwayland_path = getenv("WLR_XWAYLAND");
if (xwayland_path) {
wlr_log(WLR_INFO, "Using Xwayland binary '%s' due to WLR_XWAYLAND",
xwayland_path);
} else {
xwayland_path = XWAYLAND_PATH;
}
// This returns if and only if the call fails
execvp(xwayland_path, argv);
wlr_log_errno(WLR_ERROR, "failed to exec %s", xwayland_path);
close(devnull);
_exit(EXIT_FAILURE);
}
static void server_finish_process(struct wlr_xwayland_server *server) {
if (!server || server->display == -1) {
return;
}
if (server->x_fd_read_event[0]) {
wl_event_source_remove(server->x_fd_read_event[0]);
wl_event_source_remove(server->x_fd_read_event[1]);
server->x_fd_read_event[0] = server->x_fd_read_event[1] = NULL;
}
if (server->client) {
wl_list_remove(&server->client_destroy.link);
wl_client_destroy(server->client);
}
if (server->pipe_source) {
wl_event_source_remove(server->pipe_source);
}
safe_close(server->wl_fd[0]);
safe_close(server->wl_fd[1]);
safe_close(server->wm_fd[0]);
safe_close(server->wm_fd[1]);
memset(server, 0, offsetof(struct wlr_xwayland_server, display));
server->wl_fd[0] = server->wl_fd[1] = -1;
server->wm_fd[0] = server->wm_fd[1] = -1;
/* We do not kill the Xwayland process, it dies to broken pipe
* after we close our side of the wm/wl fds. This is more reliable
* than trying to kill something that might no longer be Xwayland.
*/
}
static void server_finish_display(struct wlr_xwayland_server *server) {
if (!server) {
return;
}
wl_list_remove(&server->display_destroy.link);
wl_list_init(&server->display_destroy.link);
if (server->display == -1) {
return;
}
safe_close(server->x_fd[0]);
safe_close(server->x_fd[1]);
server->x_fd[0] = server->x_fd[1] = -1;
unlink_display_sockets(server->display);
server->display = -1;
server->display_name[0] = '\0';
}
static bool server_start(struct wlr_xwayland_server *server);
static bool server_start_lazy(struct wlr_xwayland_server *server);
static void handle_client_destroy(struct wl_listener *listener, void *data) {
struct wlr_xwayland_server *server =
wl_container_of(listener, server, client_destroy);
if (server->pipe_source) {
// Xwayland failed to start, let the readiness handler deal with it
return;
}
// Don't call client destroy: it's being destroyed already
server->client = NULL;
wl_list_remove(&server->client_destroy.link);
server_finish_process(server);
if (time(NULL) - server->server_start > 5) {
if (server->options.lazy) {
wlr_log(WLR_INFO, "Restarting Xwayland (lazy)");
server_start_lazy(server);
} else {
wlr_log(WLR_INFO, "Restarting Xwayland");
server_start(server);
}
}
}
static void handle_display_destroy(struct wl_listener *listener, void *data) {
struct wlr_xwayland_server *server =
wl_container_of(listener, server, display_destroy);
// Don't call client destroy: the display is being destroyed, it's too late
if (server->client) {
server->client = NULL;
wl_list_remove(&server->client_destroy.link);
}
wlr_xwayland_server_destroy(server);
}
static int xserver_handle_ready(int fd, uint32_t mask, void *data) {
// There are three ways in which we can end up here, from server_start:
// 1. the second fork failed
// 2. the exec failed
// 3. Xwayland sent a SIGUSR1
//
// All three cases result in a write to the pipe, which triggers us.
//
// For the first two cases, the first fork will exit with
// EXIT_FAILURE, notifying us that startup failed.
//
// For the third case, the first fork will exit with EXIT_SUCCESS
// and we'll know that Xwayland started successfully.
close(fd);
struct wlr_xwayland_server *server = data;
int stat_val = -1;
while (waitpid(server->pid, &stat_val, 0) < 0) {
if (errno == EINTR) {
continue;
}
wlr_log_errno(WLR_ERROR, "waitpid for Xwayland fork failed");
goto error;
}
if (stat_val) {
wlr_log(WLR_ERROR, "Xwayland startup failed, not setting up xwm");
goto error;
}
wlr_log(WLR_DEBUG, "Xserver is ready");
wl_event_source_remove(server->pipe_source);
server->pipe_source = NULL;
struct wlr_xwayland_server_ready_event event = {
.server = server,
.wm_fd = server->wm_fd[0],
};
wlr_signal_emit_safe(&server->events.ready, &event);
return 1; /* wayland event loop dispatcher's count */
error:
/* clean up */
server_finish_process(server);
server_finish_display(server);
return 1;
}
static bool server_start_display(struct wlr_xwayland_server *server,
struct wl_display *wl_display) {
server->display_destroy.notify = handle_display_destroy;
wl_display_add_destroy_listener(wl_display, &server->display_destroy);
server->display = open_display_sockets(server->x_fd);
if (server->display < 0) {
server_finish_display(server);
return false;
}
snprintf(server->display_name, sizeof(server->display_name),
":%d", server->display);
return true;
}
static bool server_start(struct wlr_xwayland_server *server) {
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if (socketpair(AF_UNIX, SOCK_STREAM, 0, server->wl_fd) != 0) {
wlr_log_errno(WLR_ERROR, "socketpair failed");
server_finish_process(server);
return false;
}
if (!set_cloexec(server->wl_fd[0], true) ||
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!set_cloexec(server->wl_fd[1], true)) {
wlr_log(WLR_ERROR, "Failed to set O_CLOEXEC on socket");
server_finish_process(server);
return false;
}
if (server->options.enable_wm) {
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if (socketpair(AF_UNIX, SOCK_STREAM, 0, server->wm_fd) != 0) {
wlr_log_errno(WLR_ERROR, "socketpair failed");
server_finish_process(server);
return false;
}
if (!set_cloexec(server->wm_fd[0], true) ||
!set_cloexec(server->wm_fd[1], true)) {
wlr_log(WLR_ERROR, "Failed to set O_CLOEXEC on socket");
server_finish_process(server);
return false;
}
}
server->server_start = time(NULL);
server->client = wl_client_create(server->wl_display, server->wl_fd[0]);
if (!server->client) {
wlr_log_errno(WLR_ERROR, "wl_client_create failed");
server_finish_process(server);
return false;
}
server->wl_fd[0] = -1; /* not ours anymore */
server->client_destroy.notify = handle_client_destroy;
wl_client_add_destroy_listener(server->client, &server->client_destroy);
int p[2];
if (pipe(p) == -1) {
wlr_log_errno(WLR_ERROR, "pipe failed");
server_finish_process(server);
return false;
}
if (!set_cloexec(p[1], true) || !set_cloexec(p[0], true)) {
wlr_log(WLR_ERROR, "Failed to set CLOEXEC on FD");
server_finish_process(server);
return false;
}
struct wl_event_loop *loop = wl_display_get_event_loop(server->wl_display);
server->pipe_source = wl_event_loop_add_fd(loop, p[0],
WL_EVENT_READABLE, xserver_handle_ready, server);
server->pid = fork();
if (server->pid < 0) {
wlr_log_errno(WLR_ERROR, "fork failed");
close(p[0]);
close(p[1]);
server_finish_process(server);
return false;
} else if (server->pid == 0) {
/* Double-fork, but we need to forward SIGUSR1 once Xserver(1)
* is ready, or error if there was one. */
close(p[0]);
sigset_t sigset;
sigemptyset(&sigset);
sigaddset(&sigset, SIGUSR1);
sigaddset(&sigset, SIGCHLD);
sigprocmask(SIG_BLOCK, &sigset, NULL);
pid_t pid = fork();
if (pid < 0) {
wlr_log_errno(WLR_ERROR, "second fork failed");
(void)!write(p[1], "\n", 1);
_exit(EXIT_FAILURE);
} else if (pid == 0) {
exec_xwayland(server);
}
int sig;
sigwait(&sigset, &sig);
if (write(p[1], "\n", 1) < 1) {
// Note: if this write failed and we've leaked the write
// end of the pipe (due to a race between another thread
// exec'ing and our call to fcntl), then our handler will
// never wake up and never notice this failure. Hopefully
// that combination of events is extremely unlikely. This
// applies to the other write, too.
wlr_log_errno(WLR_ERROR, "write to pipe failed");
_exit(EXIT_FAILURE);
}
if (sig == SIGCHLD) {
waitpid(pid, NULL, 0);
_exit(EXIT_FAILURE);
}
_exit(EXIT_SUCCESS);
}
/* close child fds */
/* remain managing x sockets for lazy start */
close(p[1]);
close(server->wl_fd[1]);
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safe_close(server->wm_fd[1]);
server->wl_fd[1] = server->wm_fd[1] = -1;
return true;
}
static int xwayland_socket_connected(int fd, uint32_t mask, void *data) {
struct wlr_xwayland_server *server = data;
wl_event_source_remove(server->x_fd_read_event[0]);
wl_event_source_remove(server->x_fd_read_event[1]);
server->x_fd_read_event[0] = server->x_fd_read_event[1] = NULL;
server_start(server);
return 0;
}
static bool server_start_lazy(struct wlr_xwayland_server *server) {
struct wl_event_loop *loop = wl_display_get_event_loop(server->wl_display);
if (!(server->x_fd_read_event[0] = wl_event_loop_add_fd(loop, server->x_fd[0],
WL_EVENT_READABLE, xwayland_socket_connected, server))) {
return false;
}
if (!(server->x_fd_read_event[1] = wl_event_loop_add_fd(loop, server->x_fd[1],
WL_EVENT_READABLE, xwayland_socket_connected, server))) {
wl_event_source_remove(server->x_fd_read_event[0]);
server->x_fd_read_event[0] = NULL;
return false;
}
return true;
}
void wlr_xwayland_server_destroy(struct wlr_xwayland_server *server) {
if (!server) {
return;
}
server_finish_process(server);
server_finish_display(server);
wlr_signal_emit_safe(&server->events.destroy, NULL);
free(server);
}
struct wlr_xwayland_server *wlr_xwayland_server_create(
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struct wl_display *wl_display,
struct wlr_xwayland_server_options *options) {
if (!getenv("WLR_XWAYLAND") && access(XWAYLAND_PATH, X_OK) != 0) {
wlr_log(WLR_ERROR, "Cannot find Xwayland binary \"%s\"", XWAYLAND_PATH);
return NULL;
}
struct wlr_xwayland_server *server =
calloc(1, sizeof(struct wlr_xwayland_server));
if (!server) {
return NULL;
}
server->wl_display = wl_display;
server->options = *options;
server->x_fd[0] = server->x_fd[1] = -1;
server->wl_fd[0] = server->wl_fd[1] = -1;
server->wm_fd[0] = server->wm_fd[1] = -1;
wl_signal_init(&server->events.ready);
wl_signal_init(&server->events.destroy);
if (!server_start_display(server, wl_display)) {
goto error_alloc;
}
if (server->options.lazy) {
if (!server_start_lazy(server)) {
goto error_display;
}
} else {
if (!server_start(server)) {
goto error_display;
}
}
return server;
error_display:
server_finish_display(server);
error_alloc:
free(server);
return NULL;
}