tty: Open a new vt if not running on a VT

This is typically when launcing from a pty such as an X (or Wayland)
terminal or from an ssh session.  Opening a new vt typically requires root
priviledges, so weston must be setuid root or laucnhed as root for this
to work.

diff --git a/src/tty.c b/src/tty.c
index 7b68ff1..6fdc781 100644 (file)
--- a/src/tty.c
+++ b/src/tty.c
@@ -80,6 +80,41 @@ on_tty_input(int fd, uint32_t mask, void *data)
        return 1;
 }
 
+static int
+try_open_vt(void)
+{
+       int tty0, vt, fd;
+       char filename[16];
+
+       tty0 = open("/dev/tty0", O_WRONLY | O_CLOEXEC);
+       if (tty0 < 0) {
+               fprintf(stderr, "could not open tty0: %m\n");
+               return -1;
+       }
+
+       if (ioctl(tty0, VT_OPENQRY, &vt) < 0 || vt == -1) {
+               fprintf(stderr, "could not open tty0: %m\n");
+               close(tty0);
+               return -1;
+       }
+
+       close(tty0);
+       snprintf(filename, sizeof filename, "/dev/tty%d", vt);
+       fprintf(stderr, "compositor: using new vt %s\n", filename);
+       fd = open(filename, O_RDWR | O_NOCTTY | O_CLOEXEC);
+       if (fd < 0)
+               return fd;
+
+       if (ioctl(fd, VT_ACTIVATE, vt) < 0 ||
+           ioctl(fd, VT_WAITACTIVE, vt) < 0) {
+               fprintf(stderr, "failed to swtich to new vt\n");
+               close(fd);
+               return -1;
+       }
+
+       return fd;
+}
+
 struct tty *
 tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
            int tty_nr)
@@ -103,8 +138,14 @@ tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
                snprintf(filename, sizeof filename, "/dev/tty%d", tty_nr);
                fprintf(stderr, "compositor: using %s\n", filename);
                tty->fd = open(filename, O_RDWR | O_NOCTTY | O_CLOEXEC);
-       } else {
+       } else if (fstat(tty->fd, &buf) == 0 &&
+                  major(buf.st_rdev) == TTY_MAJOR &&
+                  minor(buf.st_rdev) > 0) {
                tty->fd = fcntl(0, F_DUPFD_CLOEXEC, 0);
+       } else {
+               /* Fall back to try opening a new VT.  This typically
+                * requires root. */
+               tty->fd = try_open_vt();
        }
 
        if (tty->fd <= 0) {
@@ -112,13 +153,6 @@ tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
                return NULL;
        }
 
-       if (fstat(tty->fd, &buf) < 0 ||
-           major(buf.st_rdev) != TTY_MAJOR || minor(buf.st_rdev) == 0) {
-               fprintf(stderr, "stdin not a vt (%d, %d)\n",
-                       major(buf.st_dev), minor(buf.st_dev));
-               return NULL;
-       }
-
        if (tcgetattr(tty->fd, &tty->terminal_attributes) < 0) {
                fprintf(stderr, "could not get terminal attributes: %m\n");
                return NULL;