xwayland: Reuse weston_client_launch

Now that our process-launching internals are identical between the
(still-misnamed) weston_client_launch and the frontend's Xwayland
launcher, we can reuse the internals instead of open-coding it.

As a result, we now additionally prevent Xwayland from inheriting
Weston's signal mask, by clearing SIG_UNBLOCK on all signals. This
should have no observable effect as we do not depend on signal handling
within Xwayland, instead using the displayfd readiness mechanism since
c2f4201ed2.

Signed-off-by: Daniel Stone <daniels@collabora.com>

compositor/xwayland.c

@@ -91,11 +91,20 @@ out:
 	return 0;
 }
 
+static void
+xserver_cleanup(struct weston_process *process, int status)
+{
+	struct wet_xwayland *wxw =
+		container_of(process, struct wet_xwayland, process);
+
+	wxw->api->xserver_exited(wxw->xwayland, status);
+	wxw->client = NULL;
+}
+
 static pid_t
 spawn_xserver(void *user_data, const char *display, int abstract_fd, int unix_fd)
 {
 	struct wet_xwayland *wxw = user_data;
-	pid_t pid;
 	struct fdstr wayland_socket = FDSTR_INIT;
 	struct fdstr x11_abstract_socket = FDSTR_INIT;
 	struct fdstr x11_unix_socket = FDSTR_INIT;
@@ -105,34 +114,29 @@ spawn_xserver(void *user_data, const char *display, int abstract_fd, int unix_fd
 	struct weston_config *config = wet_get_config(wxw->compositor);
 	struct weston_config_section *section;
 	struct wl_event_loop *loop;
-	char *exec_failure_msg;
-	const char *cloexec_failure_msg = "Couldn't unset CLOEXEC on child FDs";
 	struct custom_env child_env;
 	int no_cloexec_fds[5];
 	size_t num_no_cloexec_fds = 0;
-	size_t i;
-	char *const *envp;
-	char *const *argp;
 	int ret;
 	size_t written __attribute__ ((unused));
 
 	if (os_socketpair_cloexec(AF_UNIX, SOCK_STREAM, 0, wayland_socket.fds) < 0) {
 		weston_log("wl connection socketpair failed\n");
-		return -1;
+		goto err;
 	}
 	fdstr_update_str1(&wayland_socket);
 	no_cloexec_fds[num_no_cloexec_fds++] = wayland_socket.fds[1];
 
 	if (os_socketpair_cloexec(AF_UNIX, SOCK_STREAM, 0, x11_wm_socket.fds) < 0) {
 		weston_log("X wm connection socketpair failed\n");
-		goto err_wayland_socket;
+		goto err;
 	}
 	fdstr_update_str1(&x11_wm_socket);
 	no_cloexec_fds[num_no_cloexec_fds++] = x11_wm_socket.fds[1];
 
 	if (pipe2(display_pipe.fds, O_CLOEXEC) < 0) {
 		weston_log("pipe creation for displayfd failed\n");
-		goto err_x11_wm_socket;
+		goto err;
 	}
 	fdstr_update_str1(&display_pipe);
 	no_cloexec_fds[num_no_cloexec_fds++] = display_pipe.fds[1];
@@ -148,8 +152,6 @@ spawn_xserver(void *user_data, const char *display, int abstract_fd, int unix_fd
 	section = weston_config_get_section(config, "xwayland", NULL, NULL);
 	weston_config_section_get_string(section, "path",
 					 &xserver, XSERVER_PATH);
-	str_printf(&exec_failure_msg,
-		   "Error: executing Xwayland as '%s' failed.\n", xserver);
 	custom_env_init_from_environ(&child_env);
 	custom_env_set_env_var(&child_env, "WAYLAND_SOCKET", wayland_socket.str1);
 
@@ -166,87 +168,50 @@ spawn_xserver(void *user_data, const char *display, int abstract_fd, int unix_fd
 	custom_env_add_arg(&child_env, x11_wm_socket.str1);
 	custom_env_add_arg(&child_env, "-terminate");
 
-	envp = custom_env_get_envp(&child_env);
+	ret = weston_client_launch(wxw->compositor, &wxw->process, &child_env,
-	argp = custom_env_get_argp(&child_env);
+				   no_cloexec_fds, num_no_cloexec_fds,
-
+				   xserver_cleanup);
-	pid = fork();
+	if (!ret) {
-	switch (pid) {
+		weston_log("Couldn't start Xwayland\n");
-	case 0:
+		goto err;
-		setsid();
-
-		for (i = 0; i < num_no_cloexec_fds; i++) {
-			ret = os_fd_clear_cloexec(no_cloexec_fds[i]);
-			if (ret < 0) {
-				write(STDERR_FILENO, cloexec_failure_msg,
-				      strlen(cloexec_failure_msg));
-				_exit(EXIT_FAILURE);
-			}
-		}
-
-		execve(xserver, argp, envp);
-		/* execve does not return on success, so it failed */
-
-		if (exec_failure_msg) {
-			written = write(STDERR_FILENO, exec_failure_msg,
-					strlen(exec_failure_msg));
-		}
-
-		_exit(EXIT_FAILURE);
-
-	default:
-		close(wayland_socket.fds[1]);
-		wxw->client = wl_client_create(wxw->compositor->wl_display,
-					       wayland_socket.fds[0]);
-
-		close(x11_wm_socket.fds[1]);
-		wxw->wm_fd = x11_wm_socket.fds[0];
-
-		/* During initialization the X server will round trip
-		 * and block on the wayland compositor, so avoid making
-		 * blocking requests (like xcb_connect_to_fd) until
-		 * it's done with that. */
-		close(display_pipe.fds[1]);
-		loop = wl_display_get_event_loop(wxw->compositor->wl_display);
-		wxw->display_fd_source =
-			wl_event_loop_add_fd(loop, display_pipe.fds[0],
-					     WL_EVENT_READABLE,
-					     handle_display_fd, wxw);
-
-		wxw->process.pid = pid;
-		wet_watch_process(wxw->compositor, &wxw->process);
-		break;
-
-	case -1:
-		weston_log("Failed to fork to spawn xserver process\n");
-		fdstr_close_all(&wayland_socket);
-		fdstr_close_all(&x11_wm_socket);
-		fdstr_close_all(&display_pipe);
-		break;
 	}
 
-	custom_env_fini(&child_env);
+	wxw->client = wl_client_create(wxw->compositor->wl_display,
-	free(exec_failure_msg);
+				       wayland_socket.fds[0]);
+	if (!wxw->client) {
+		weston_log("Couldn't create client for Xwayland\n");
+		goto err;
+	}
+
+	wxw->wm_fd = x11_wm_socket.fds[0];
+
+	/* Now we can no longer fail, close the child end of our sockets */
+	close(wayland_socket.fds[1]);
+	close(x11_wm_socket.fds[1]);
+	close(display_pipe.fds[1]);
+
+	/* During initialization the X server will round trip
+	 * and block on the wayland compositor, so avoid making
+	 * blocking requests (like xcb_connect_to_fd) until
+	 * it's done with that. */
+	loop = wl_display_get_event_loop(wxw->compositor->wl_display);
+	wxw->display_fd_source =
+		wl_event_loop_add_fd(loop, display_pipe.fds[0],
+				     WL_EVENT_READABLE,
+				     handle_display_fd, wxw);
+
 	free(xserver);
 
-	return pid;
+	return wxw->process.pid;
 
-err_x11_wm_socket:
+err:
+	free(xserver);
+	fdstr_close_all(&display_pipe);
 	fdstr_close_all(&x11_wm_socket);
-err_wayland_socket:
 	fdstr_close_all(&wayland_socket);
 	return -1;
 }
 
-static void
-xserver_cleanup(struct weston_process *process, int status)
-{
-	struct wet_xwayland *wxw =
-		container_of(process, struct wet_xwayland, process);
-
-	wxw->api->xserver_exited(wxw->xwayland, status);
-	wxw->client = NULL;
-}
-
 static void
 wxw_compositor_destroy(struct wl_listener *listener, void *data)
 {