/*      $NetBSD: tty_tty.c,v 1.41 2020/05/23 23:42:43 ad Exp $  */

/*-
* Copyright (c) 1982, 1986, 1991, 1993, 1995
*      The Regents of the University of California.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*      @(#)tty_tty.c   8.2 (Berkeley) 9/23/93
*/

/*
* Indirect driver for controlling tty.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tty_tty.c,v 1.41 2020/05/23 23:42:43 ad Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/proc.h>
#include <sys/tty.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/conf.h>
#include <sys/kauth.h>

/* XXXSMP */
#define cttyvp(p) ((p)->p_lflag & PL_CONTROLT ? (p)->p_session->s_ttyvp : NULL)

/*ARGSUSED*/
static int
cttyopen(dev_t dev, int flag, int mode, struct lwp *l)
{
       struct vnode *ttyvp = cttyvp(l->l_proc);
       int error;

       if (ttyvp == NULL)
               return (ENXIO);
       vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY);
#ifdef PARANOID
       /*
        * Since group is tty and mode is 620 on most terminal lines
        * and since sessions protect terminals from processes outside
        * your session, this check is probably no longer necessary.
        * Since it inhibits setuid root programs that later switch
        * to another user from accessing /dev/tty, we have decided
        * to delete this test. (mckusick 5/93)
        */
       error = VOP_ACCESS(ttyvp,
         (flag&FREAD ? VREAD : 0) | (flag&FWRITE ? VWRITE : 0), l->l_cred, l);
       if (!error)
#endif /* PARANOID */
               error = VOP_OPEN(ttyvp, flag, NOCRED);
       VOP_UNLOCK(ttyvp);
       return (error);
}

/*ARGSUSED*/
static int
cttyread(dev_t dev, struct uio *uio, int flag)
{
       struct vnode *ttyvp = cttyvp(curproc);
       int error;

       if (ttyvp == NULL)
               return (EIO);
       vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY);
       error = VOP_READ(ttyvp, uio, flag, NOCRED);
       VOP_UNLOCK(ttyvp);
       return (error);
}

/*ARGSUSED*/
static int
cttywrite(dev_t dev, struct uio *uio, int flag)
{
       struct vnode *ttyvp = cttyvp(curproc);
       int error;

       if (ttyvp == NULL)
               return (EIO);
       vn_lock(ttyvp, LK_EXCLUSIVE | LK_RETRY);
       error = VOP_WRITE(ttyvp, uio, flag, NOCRED);
       VOP_UNLOCK(ttyvp);
       return (error);
}

/*ARGSUSED*/
static int
cttyioctl(dev_t dev, u_long cmd, void *addr, int flag, struct lwp *l)
{
       struct vnode *ttyvp = cttyvp(l->l_proc);
       int rv;

       if (ttyvp == NULL)
               return (EIO);
       if (cmd == TIOCSCTTY)           /* XXX */
               return (EINVAL);
       if (cmd == TIOCNOTTY) {
               mutex_enter(&proc_lock);
               if (!SESS_LEADER(l->l_proc)) {
                       l->l_proc->p_lflag &= ~PL_CONTROLT;
                       rv = 0;
               } else
                       rv = EINVAL;
               mutex_exit(&proc_lock);
               return (rv);
       }
       return (VOP_IOCTL(ttyvp, cmd, addr, flag, NOCRED));
}

/*ARGSUSED*/
static int
cttypoll(dev_t dev, int events, struct lwp *l)
{
       struct vnode *ttyvp = cttyvp(l->l_proc);

       if (ttyvp == NULL)
               return (seltrue(dev, events, l));
       return (VOP_POLL(ttyvp, events));
}

static int
cttykqfilter(dev_t dev, struct knote *kn)
{
       /* This is called from filt_fileattach() by the attaching process. */
       struct proc *p = curproc;
       struct vnode *ttyvp = cttyvp(p);

       if (ttyvp == NULL)
               return (1);
       return (VOP_KQFILTER(ttyvp, kn));
}

const struct cdevsw ctty_cdevsw = {
       .d_open = cttyopen,
       .d_close = nullclose,
       .d_read = cttyread,
       .d_write = cttywrite,
       .d_ioctl = cttyioctl,
       .d_stop = nullstop,
       .d_tty = notty,
       .d_poll = cttypoll,
       .d_mmap = nommap,
       .d_kqfilter = cttykqfilter,
       .d_discard = nodiscard,
       .d_flag = D_TTY
};