Moved session/ into backend/

backend/session/direct-ipc.c

@@ -0,0 +1,241 @@
+#define _POSIX_C_SOURCE 200809L
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/sysmacros.h>
+#include <sys/wait.h>
+#include <xf86drm.h>
+#include <linux/major.h>
+#include <wlr/util/log.h>
+#include "session/direct-ipc.h"
+
+enum { DRM_MAJOR = 226 };
+
+#ifdef HAS_LIBCAP
+#include <sys/capability.h>
+
+static bool have_permissions(void) {
+	cap_t cap = cap_get_proc();
+	cap_flag_value_t val;
+
+	if (!cap || cap_get_flag(cap, CAP_SYS_ADMIN, CAP_PERMITTED, &val) || val != CAP_SET) {
+		wlr_log(L_ERROR, "Do not have CAP_SYS_ADMIN; cannot become DRM master");
+		cap_free(cap);
+		return false;
+	}
+
+	cap_free(cap);
+	return true;
+}
+#else
+static bool have_permissions(void) {
+	if (geteuid() != 0) {
+		wlr_log(L_ERROR, "Do not have root privileges; cannot become DRM master");
+		return false;
+	}
+
+	return true;
+}
+#endif
+
+static void send_msg(int sock, int fd, void *buf, size_t buf_len) {
+	char control[CMSG_SPACE(sizeof(fd))] = {0};
+	struct iovec iovec = { .iov_base = buf, .iov_len = buf_len };
+	struct msghdr msghdr = {0};
+
+	if (buf) {
+		msghdr.msg_iov = &iovec;
+		msghdr.msg_iovlen = 1;
+	}
+
+	if (fd >= 0) {
+		msghdr.msg_control = &control;
+		msghdr.msg_controllen = sizeof(control);
+
+		struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr);
+		*cmsg = (struct cmsghdr) {
+			.cmsg_level = SOL_SOCKET,
+			.cmsg_type = SCM_RIGHTS,
+			.cmsg_len = CMSG_LEN(sizeof(fd)),
+		};
+		memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
+	}
+
+	ssize_t ret;
+	do {
+		ret = sendmsg(sock, &msghdr, 0);
+	} while (ret < 0 && errno == EINTR);
+}
+
+static ssize_t recv_msg(int sock, int *fd_out, void *buf, size_t buf_len) {
+	char control[CMSG_SPACE(sizeof(*fd_out))] = {0};
+	struct iovec iovec = { .iov_base = buf, .iov_len = buf_len };
+	struct msghdr msghdr = {0};
+
+	if (buf) {
+		msghdr.msg_iov = &iovec;
+		msghdr.msg_iovlen = 1;
+	}
+
+	if (fd_out) {
+		msghdr.msg_control = &control;
+		msghdr.msg_controllen = sizeof(control);
+	}
+
+	ssize_t ret;
+	do {
+		ret = recvmsg(sock, &msghdr, MSG_CMSG_CLOEXEC);
+	} while (ret < 0 && errno == EINTR);
+
+	if (fd_out) {
+		struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr);
+		if (cmsg) {
+			memcpy(fd_out, CMSG_DATA(cmsg), sizeof(*fd_out));
+		} else {
+			*fd_out = -1;
+		}
+	}
+
+	return ret;
+}
+
+enum msg_type {
+	MSG_OPEN,
+	MSG_SETMASTER,
+	MSG_DROPMASTER,
+	MSG_END,
+};
+
+struct msg {
+	enum msg_type type;
+	char path[256];
+};
+
+static void communicate(int sock) {
+	struct msg msg;
+	int drm_fd = -1;
+	bool running = true;
+
+	while (running && recv_msg(sock, &drm_fd, &msg, sizeof(msg)) >= 0) {
+		switch (msg.type) {
+		case MSG_OPEN:
+			errno = 0;
+
+			// These are the same flags that logind opens files with
+			int fd = open(msg.path, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
+			int ret = errno;
+			if (fd == -1) {
+				goto error;
+			}
+
+			struct stat st;
+			if (fstat(fd, &st) < 0) {
+				ret = errno;
+				goto error;
+			}
+
+			uint32_t maj = major(st.st_rdev);
+			if (maj != INPUT_MAJOR && maj != DRM_MAJOR) {
+				ret = ENOTSUP;
+				goto error;
+			}
+
+			if (maj == DRM_MAJOR && drmSetMaster(fd)) {
+				ret = errno;
+			}
+error:
+			send_msg(sock, ret ? -1 : fd, &ret, sizeof(ret));
+			close(fd);
+
+			break;
+
+		case MSG_SETMASTER:
+			drmSetMaster(drm_fd);
+			close(drm_fd);
+			send_msg(sock, -1, NULL, 0);
+			break;
+
+		case MSG_DROPMASTER:
+			drmDropMaster(drm_fd);
+			close(drm_fd);
+			send_msg(sock, -1, NULL, 0);
+			break;
+
+		case MSG_END:
+			running = false;
+			send_msg(sock, -1, NULL, 0);
+			break;
+		}
+	}
+
+	close(sock);
+}
+
+int direct_ipc_open(int sock, const char *path) {
+	struct msg msg = { .type = MSG_OPEN };
+	snprintf(msg.path, sizeof(msg.path), "%s", path);
+
+	send_msg(sock, -1, &msg, sizeof(msg));
+
+	int fd, err;
+	recv_msg(sock, &fd, &err, sizeof(err));
+
+	return err ? -err : fd;
+}
+
+void direct_ipc_setmaster(int sock, int fd) {
+	struct msg msg = { .type = MSG_SETMASTER };
+
+	send_msg(sock, fd, &msg, sizeof(msg));
+	recv_msg(sock, NULL, NULL, 0);
+}
+
+void direct_ipc_dropmaster(int sock, int fd) {
+	struct msg msg = { .type = MSG_DROPMASTER };
+
+	send_msg(sock, fd, &msg, sizeof(msg));
+	recv_msg(sock, NULL, NULL, 0);
+}
+
+void direct_ipc_finish(int sock, pid_t pid) {
+	struct msg msg = { .type = MSG_END };
+
+	send_msg(sock, -1, &msg, sizeof(msg));
+	recv_msg(sock, NULL, NULL, 0);
+
+	waitpid(pid, NULL, 0);
+}
+
+int direct_ipc_start(pid_t *pid_out) {
+	if (!have_permissions()) {
+		return -1;
+	}
+
+	int sock[2];
+	if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sock) < 0) {
+		wlr_log_errno(L_ERROR, "Failed to create socket pair");
+		return -1;
+	}
+
+	pid_t pid = fork();
+	if (pid < 0) {
+		wlr_log_errno(L_ERROR, "Fork failed");
+		close(sock[0]);
+		close(sock[1]);
+		return -1;
+	} else if (pid == 0) {
+		close(sock[0]);
+		communicate(sock[1]);
+		_Exit(0);
+	}
+
+	close(sock[1]);
+	*pid_out = pid;
+	return sock[0];
+}

backend/session/direct.c

@@ -0,0 +1,244 @@
+#define _POSIX_C_SOURCE 200809L
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <signal.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <linux/kd.h>
+#include <linux/major.h>
+#include <linux/input.h>
+#include <linux/vt.h>
+#include <wayland-server.h>
+#include <wlr/session/interface.h>
+#include <wlr/util/log.h>
+#include "session/direct-ipc.h"
+
+enum { DRM_MAJOR = 226 };
+
+const struct session_impl session_direct;
+
+struct direct_session {
+	struct wlr_session base;
+	int tty_fd;
+	int old_kbmode;
+	int sock;
+	pid_t child;
+
+	struct wl_event_source *vt_source;
+};
+
+static int direct_session_open(struct wlr_session *base, const char *path) {
+	struct direct_session *session = wl_container_of(base, session, base);
+
+	int fd = direct_ipc_open(session->sock, path);
+	if (fd < 0) {
+		wlr_log(L_ERROR, "Failed to open %s: %s%s", path, strerror(-fd),
+			fd == -EINVAL ? "; is another display server running?" : "");
+		return fd;
+	}
+
+	struct stat st;
+	if (fstat(fd, &st) < 0) {
+		close(fd);
+		return -errno;
+	}
+
+	if (major(st.st_rdev) == DRM_MAJOR) {
+		session->base.drm_fd = fd;
+	}
+
+	return fd;
+}
+
+static void direct_session_close(struct wlr_session *base, int fd) {
+	struct direct_session *session = wl_container_of(base, session, base);
+
+	struct stat st;
+	if (fstat(fd, &st) < 0) {
+		wlr_log_errno(L_ERROR, "Stat failed");
+		close(fd);
+		return;
+	}
+
+	if (major(st.st_rdev) == DRM_MAJOR) {
+		direct_ipc_dropmaster(session->sock, session->base.drm_fd);
+		session->base.drm_fd = -1;
+	} else if (major(st.st_rdev) == INPUT_MAJOR) {
+		ioctl(fd, EVIOCREVOKE, 0);
+	}
+
+	close(fd);
+}
+
+static bool direct_change_vt(struct wlr_session *base, unsigned vt) {
+	struct direct_session *session = wl_container_of(base, session, base);
+	return ioctl(session->tty_fd, VT_ACTIVATE, (int)vt) == 0;
+}
+
+static void direct_session_finish(struct wlr_session *base) {
+	struct direct_session *session = wl_container_of(base, session, base);
+	struct vt_mode mode = {
+		.mode = VT_AUTO,
+	};
+
+	errno = 0;
+
+	ioctl(session->tty_fd, KDSKBMODE, session->old_kbmode);
+	ioctl(session->tty_fd, KDSETMODE, KD_TEXT);
+	ioctl(session->tty_fd, VT_SETMODE, &mode);
+
+	if (errno) {
+		wlr_log(L_ERROR, "Failed to restore tty");
+	}
+
+	direct_ipc_finish(session->sock, session->child);
+	close(session->sock);
+
+	wl_event_source_remove(session->vt_source);
+	close(session->tty_fd);
+	free(session);
+}
+
+static int vt_handler(int signo, void *data) {
+	struct direct_session *session = data;
+
+	if (session->base.active) {
+		session->base.active = false;
+		wl_signal_emit(&session->base.session_signal, session);
+		direct_ipc_dropmaster(session->sock, session->base.drm_fd);
+		ioctl(session->tty_fd, VT_RELDISP, 1);
+	} else {
+		ioctl(session->tty_fd, VT_RELDISP, VT_ACKACQ);
+		direct_ipc_setmaster(session->sock, session->base.drm_fd);
+		session->base.active = true;
+		wl_signal_emit(&session->base.session_signal, session);
+	}
+
+	return 1;
+}
+
+static bool setup_tty(struct direct_session *session, struct wl_display *display) {
+	int fd = dup(STDIN_FILENO);
+	if (fd == -1) {
+		wlr_log_errno(L_ERROR, "Cannot open tty");
+		return false;
+	}
+
+	struct stat st;
+	if (fstat(fd, &st) == -1 || major(st.st_rdev) != TTY_MAJOR || minor(st.st_rdev) == 0) {
+		wlr_log(L_ERROR, "Not running from a virtual terminal");
+		goto error;
+	}
+
+	int tty = minor(st.st_rdev);
+	int ret, kd_mode, old_kbmode;
+
+	ret = ioctl(fd, KDGETMODE, &kd_mode);
+	if (ret) {
+		wlr_log_errno(L_ERROR, "Failed to get tty mode");
+		goto error;
+	}
+
+	if (kd_mode != KD_TEXT) {
+		wlr_log(L_ERROR,
+			"tty already in graphics mode; is another display server running?");
+		goto error;
+	}
+
+	ioctl(fd, VT_ACTIVATE, tty);
+	ioctl(fd, VT_WAITACTIVE, tty);
+
+	if (ioctl(fd, KDGKBMODE, &old_kbmode)) {
+		wlr_log_errno(L_ERROR, "Failed to read keyboard mode");
+		goto error;
+	}
+
+	if (ioctl(fd, KDSKBMODE, K_OFF)) {
+		wlr_log_errno(L_ERROR, "Failed to set keyboard mode");
+		goto error;
+	}
+
+	if (ioctl(fd, KDSETMODE, KD_GRAPHICS)) {
+		wlr_log_errno(L_ERROR, "Failed to set graphics mode on tty");
+		goto error;
+	}
+
+	struct vt_mode mode = {
+		.mode = VT_PROCESS,
+		.relsig = SIGUSR1,
+		.acqsig = SIGUSR1,
+	};
+
+	if (ioctl(fd, VT_SETMODE, &mode) < 0) {
+		wlr_log(L_ERROR, "Failed to take control of tty");
+		goto error;
+	}
+
+	struct wl_event_loop *loop = wl_display_get_event_loop(display);
+	session->vt_source = wl_event_loop_add_signal(loop, SIGUSR1,
+		vt_handler, session);
+	if (!session->vt_source) {
+		goto error;
+	}
+
+	session->base.vtnr = tty;
+	session->tty_fd = fd;
+	session->old_kbmode = old_kbmode;
+
+	return true;
+
+error:
+	close(fd);
+	return false;
+}
+
+static struct wlr_session *direct_session_start(struct wl_display *disp) {
+	struct direct_session *session = calloc(1, sizeof(*session));
+	if (!session) {
+		wlr_log_errno(L_ERROR, "Allocation failed");
+		return NULL;
+	}
+
+	session->sock = direct_ipc_start(&session->child);
+	if (session->sock == -1) {
+		goto error_session;
+	}
+
+	if (!setup_tty(session, disp)) {
+		goto error_ipc;
+	}
+
+	// XXX: Is it okay to trust the environment like this?
+	const char *seat = getenv("XDG_SEAT");
+	if (!seat) {
+		seat = "seat0";
+	}
+
+	wlr_log(L_INFO, "Successfully loaded direct session");
+
+	snprintf(session->base.seat, sizeof(session->base.seat), "%s", seat);
+	session->base.drm_fd = -1;
+	session->base.impl = &session_direct;
+	session->base.active = true;
+	wl_signal_init(&session->base.session_signal);
+	return &session->base;
+
+error_ipc:
+	direct_ipc_finish(session->sock, session->child);
+	close(session->sock);
+error_session:
+	free(session);
+	return NULL;
+}
+
+const struct session_impl session_direct = {
+	.start = direct_session_start,
+	.finish = direct_session_finish,
+	.open = direct_session_open,
+	.close = direct_session_close,
+	.change_vt = direct_change_vt,
+};

backend/session/logind.c

@@ -0,0 +1,398 @@
+#define _POSIX_C_SOURCE 200809L
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <systemd/sd-bus.h>
+#include <systemd/sd-login.h>
+#include <unistd.h>
+#include <sys/sysmacros.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <wayland-server.h>
+#include <wlr/session/interface.h>
+#include <wlr/util/log.h>
+
+enum { DRM_MAJOR = 226 };
+
+const struct session_impl session_logind;
+
+struct logind_session {
+	struct wlr_session base;
+
+	sd_bus *bus;
+	struct wl_event_source *event;
+
+	char *id;
+	char *path;
+};
+
+static int logind_take_device(struct wlr_session *base, const char *path) {
+	struct logind_session *session = wl_container_of(base, session, base);
+
+	int ret;
+	int fd = -1;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	struct stat st;
+	if (stat(path, &st) < 0) {
+		wlr_log(L_ERROR, "Failed to stat '%s'", path);
+		return -1;
+	}
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "TakeDevice",
+		&error, &msg, "uu", major(st.st_rdev), minor(st.st_rdev));
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to take device '%s': %s", path, error.message);
+		goto error;
+	}
+
+	int paused = 0;
+	ret = sd_bus_message_read(msg, "hb", &fd, &paused);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to parse D-Bus response for '%s': %s",
+			path, strerror(-ret));
+		goto error;
+	}
+
+	// The original fd seems to be closed when the message is freed
+	// so we just clone it.
+	fd = fcntl(fd, F_DUPFD_CLOEXEC, 0);
+	if (fd == -1) {
+		wlr_log(L_ERROR, "Failed to clone file descriptor for '%s': %s",
+			path, strerror(errno));
+		goto error;
+	}
+
+	if (major(st.st_rdev) == DRM_MAJOR) {
+		session->base.drm_fd = fd;
+	}
+
+error:
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+	return fd;
+}
+
+static void logind_release_device(struct wlr_session *base, int fd) {
+	struct logind_session *session = wl_container_of(base, session, base);
+
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	struct stat st;
+	if (fstat(fd, &st) < 0) {
+		wlr_log(L_ERROR, "Failed to stat device '%d'", fd);
+		return;
+	}
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "ReleaseDevice",
+		&error, &msg, "uu", major(st.st_rdev), minor(st.st_rdev));
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to release device '%d'", fd);
+	}
+
+	if (major(st.st_rdev) == DRM_MAJOR) {
+		session->base.drm_fd = -1;
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+}
+
+static bool logind_change_vt(struct wlr_session *base, unsigned vt) {
+	struct logind_session *session = wl_container_of(base, session, base);
+
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		"/org/freedesktop/login1/seat/self", "org.freedesktop.login1.Seat", "SwitchTo",
+		&error, &msg, "u", (uint32_t)vt);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to change to vt '%d'", vt);
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+	return ret >= 0;
+}
+
+static bool find_sesion_path(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+			"/org/freedesktop/login1", "org.freedesktop.login1.Manager",
+			"GetSession", &error, &msg, "s", session->id);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to get session path: %s", strerror(-ret));
+		goto out;
+	}
+
+	const char *path;
+
+	ret = sd_bus_message_read(msg, "o", &path);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Could not parse session path: %s", strerror(-ret));
+		goto out;
+	}
+
+	session->path = strdup(path);
+
+out:
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+
+	return ret >= 0;
+}
+
+static bool session_activate(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "Activate",
+		&error, &msg, "");
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to activate session");
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+	return ret >= 0;
+}
+
+static bool take_control(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "TakeControl",
+		&error, &msg, "b", false);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to take control of session");
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+	return ret >= 0;
+}
+
+static void release_control(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "ReleaseControl",
+		&error, &msg, "");
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to release control of session");
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+}
+
+static void logind_session_finish(struct wlr_session *base) {
+	struct logind_session *session = wl_container_of(base, session, base);
+
+	release_control(session);
+
+	wl_event_source_remove(session->event);
+	sd_bus_unref(session->bus);
+	free(session->id);
+	free(session->path);
+	free(session);
+}
+
+static int session_removed(sd_bus_message *msg, void *userdata, sd_bus_error *ret_error) {
+	wlr_log(L_INFO, "SessionRemoved signal received");
+	return 0;
+}
+
+static int pause_device(sd_bus_message *msg, void *userdata, sd_bus_error *ret_error) {
+	struct logind_session *session = userdata;
+	int ret;
+
+	uint32_t major, minor;
+	const char *type;
+	ret = sd_bus_message_read(msg, "uus", &major, &minor, &type);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to parse D-Bus response for PauseDevice: %s",
+			strerror(-ret));
+		goto error;
+	}
+
+	if (major == DRM_MAJOR) {
+		session->base.active = false;
+		wl_signal_emit(&session->base.session_signal, session);
+	}
+
+	if (strcmp(type, "pause") == 0) {
+		ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+			session->path, "org.freedesktop.login1.Session", "PauseDeviceComplete",
+			ret_error, &msg, "uu", major, minor);
+		if (ret < 0) {
+			wlr_log(L_ERROR, "Failed to send PauseDeviceComplete signal: %s",
+				strerror(-ret));
+		}
+	}
+
+error:
+	return 0;
+}
+
+static int resume_device(sd_bus_message *msg, void *userdata, sd_bus_error *ret_error) {
+	struct logind_session *session = userdata;
+	int ret;
+
+	int fd;
+	uint32_t major, minor;
+	ret = sd_bus_message_read(msg, "uuh", &major, &minor, &fd);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to parse D-Bus response for ResumeDevice: %s",
+			strerror(-ret));
+		goto error;
+	}
+
+	if (major == DRM_MAJOR) {
+		dup2(fd, session->base.drm_fd);
+		session->base.active = true;
+		wl_signal_emit(&session->base.session_signal, session);
+	}
+
+error:
+	return 0;
+}
+
+static bool add_signal_matches(struct logind_session *session) {
+	int ret;
+
+	char str[256];
+	const char *fmt = "type='signal',"
+		"sender='org.freedesktop.login1',"
+		"interface='org.freedesktop.login1.%s',"
+		"member='%s',"
+		"path='%s'";
+
+	snprintf(str, sizeof(str), fmt, "Manager", "SesssionRemoved", "/org/freedesktop/login1");
+	ret = sd_bus_add_match(session->bus, NULL, str, session_removed, session);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to add D-Bus match: %s", strerror(-ret));
+		return false;
+	}
+
+	snprintf(str, sizeof(str), fmt, "Session", "PauseDevice", session->path);
+	ret = sd_bus_add_match(session->bus, NULL, str, pause_device, session);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to add D-Bus match: %s", strerror(-ret));
+		return false;
+	}
+
+	snprintf(str, sizeof(str), fmt, "Session", "ResumeDevice", session->path);
+	ret = sd_bus_add_match(session->bus, NULL, str, resume_device, session);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to add D-Bus match: %s", strerror(-ret));
+		return false;
+	}
+
+	return true;
+}
+
+static int dbus_event(int fd, uint32_t mask, void *data) {
+	sd_bus *bus = data;
+	while (sd_bus_process(bus, NULL) > 0);
+	return 1;
+}
+
+static struct wlr_session *logind_session_start(struct wl_display *disp) {
+	int ret;
+	struct logind_session *session = calloc(1, sizeof(*session));
+	if (!session) {
+		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		return NULL;
+	}
+
+	ret = sd_pid_get_session(getpid(), &session->id);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to get session id: %s", strerror(-ret));
+		goto error;
+	}
+
+	ret = sd_session_get_vt(session->id, &session->base.vtnr);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Session not running in virtual terminal");
+		goto error;
+	}
+
+	char *seat;
+	ret = sd_session_get_seat(session->id, &seat);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to get seat id: %s", strerror(-ret));
+		goto error;
+	}
+	snprintf(session->base.seat, sizeof(session->base.seat), "%s", seat);
+	free(seat);
+
+	ret = sd_bus_default_system(&session->bus);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to open D-Bus connection: %s", strerror(-ret));
+		goto error;
+	}
+
+	if (!find_sesion_path(session)) {
+		sd_bus_unref(session->bus);
+		goto error;
+	}
+
+	if (!add_signal_matches(session)) {
+		goto error_bus;
+	}
+
+	struct wl_event_loop *event_loop = wl_display_get_event_loop(disp);
+	session->event = wl_event_loop_add_fd(event_loop, sd_bus_get_fd(session->bus),
+		WL_EVENT_READABLE, dbus_event, session->bus);
+
+	if (!session_activate(session)) {
+		goto error_bus;
+	}
+
+	if (!take_control(session)) {
+		goto error_bus;
+	}
+
+	wlr_log(L_INFO, "Successfully loaded logind session");
+
+	session->base.drm_fd = -1;
+	session->base.impl = &session_logind;
+	session->base.active = true;
+	wl_signal_init(&session->base.session_signal);
+	return &session->base;
+
+error_bus:
+	sd_bus_unref(session->bus);
+	free(session->path);
+
+error:
+	free(session->id);
+	return NULL;
+}
+
+const struct session_impl session_logind = {
+	.start = logind_session_start,
+	.finish = logind_session_finish,
+	.open = logind_take_device,
+	.close = logind_release_device,
+	.change_vt = logind_change_vt,
+};

backend/session/session.c

@@ -0,0 +1,54 @@
+#include <stddef.h>
+#include <stdarg.h>
+#include <wlr/session.h>
+#include <wlr/session/interface.h>
+#include <wlr/util/log.h>
+
+extern const struct session_impl session_logind;
+extern const struct session_impl session_direct;
+
+static const struct session_impl *impls[] = {
+#ifdef HAS_SYSTEMD
+	&session_logind,
+#endif
+	&session_direct,
+	NULL,
+};
+
+struct wlr_session *wlr_session_start(struct wl_display *disp) {
+	const struct session_impl **iter;
+
+	for (iter = impls; *iter; ++iter) {
+		struct wlr_session *session = (*iter)->start(disp);
+		if (session) {
+			return session;
+		}
+	}
+
+	wlr_log(L_ERROR, "Failed to load session backend");
+	return NULL;
+}
+
+void wlr_session_finish(struct wlr_session *session) {
+	if (!session) {
+		return;
+	}
+
+	session->impl->finish(session);
+};
+
+int wlr_session_open_file(struct wlr_session *session, const char *path) {
+	return session->impl->open(session, path);
+}
+
+void wlr_session_close_file(struct wlr_session *session, int fd) {
+	session->impl->close(session, fd);
+}
+
+bool wlr_session_change_vt(struct wlr_session *session, unsigned vt) {
+	if (!session) {
+		return false;
+	}
+
+	return session->impl->change_vt(session, vt);
+}