/*      $NetBSD: tty_ptm.c,v 1.47 2025/08/05 23:56:21 gutteridge Exp $  */

/*-
 * Copyright (c) 2004, 2020 The NetBSD Foundation, Inc.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tty_ptm.c,v 1.47 2025/08/05 23:56:21 gutteridge Exp $");

#ifdef _KERNEL_OPT
#include "opt_compat_netbsd.h"
#include "opt_ptm.h"
#endif

/* pty multiplexor driver /dev/ptm{,x} */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/proc.h>
#include <sys/tty.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/uio.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/signalvar.h>
#include <sys/filedesc.h>
#include <sys/conf.h>
#include <sys/poll.h>
#include <sys/pty.h>
#include <sys/kauth.h>
#include <sys/compat_stub.h>

#include <miscfs/specfs/specdev.h>

#include <compat/sys/ttycom.h>

#include "ioconf.h"

#ifdef DEBUG_PTM
#define DPRINTF(a)      printf a
#else
#define DPRINTF(a)
#endif

#ifdef NO_DEV_PTM
const struct cdevsw ptm_cdevsw = {
        .d_open = noopen,
        .d_close = noclose,
        .d_read = noread,
        .d_write = nowrite,
        .d_ioctl = noioctl,
        .d_stop = nostop,
        .d_tty = notty,
        .d_poll = nopoll,
        .d_mmap = nommap,
        .d_kqfilter = nokqfilter,
        .d_discard = nodiscard,
        .d_flag = D_TTY
};
#else

int pts_major, ptc_major;

static dev_t pty_getfree(void);
static int pty_alloc_master(struct lwp *, int *, dev_t *, struct mount *, int);
static int pty_alloc_slave(struct lwp *, int *, dev_t, struct mount *);
static int pty_vn_open(struct vnode *, struct lwp *);

int
pty_getmp(struct lwp *l, struct mount **mpp)
{
        if (ptm == NULL)
                return EOPNOTSUPP;

        return (*ptm->getmp)(l, mpp);
}

dev_t
pty_makedev(char ms, int minor)
{
        return makedev(ms == 't' ? pts_major : ptc_major, minor);
}


static dev_t
pty_getfree(void)
{
        extern kmutex_t pt_softc_mutex;
        int i;

        mutex_enter(&pt_softc_mutex);
        for (i = 0; i < npty; i++) {
                if (pty_isfree(i, 0))
                        break;
        }
        mutex_exit(&pt_softc_mutex);
        return pty_makedev('t', i);
}

/*
 * Hacked up version of vn_open. We _only_ handle ptys and only open
 * them with FREAD|FWRITE and never deal with creat or stuff like that.
 *
 * We need it because we have to fake up root credentials to open the pty.
 */
int
pty_vn_open(struct vnode *vp, struct lwp *l)
{
        int error;

        if (vp->v_type != VCHR) {
                vput(vp);
                return EINVAL;
        }

        error = VOP_OPEN(vp, FREAD|FWRITE, lwp0.l_cred);

        if (error) {
                /* only ptys mean we can't get these */
                KASSERT(error != EDUPFD);
                KASSERT(error != EMOVEFD);
                vput(vp);
                return error;
        }

        mutex_enter(vp->v_interlock);
        vp->v_writecount++;
        mutex_exit(vp->v_interlock);

        return 0;
}

static int
pty_alloc_master(struct lwp *l, int *fd, dev_t *dev, struct mount *mp,
    int flags)
{
        int error;
        struct file *fp;
        struct vnode *vp;
        int md;

        if ((error = fd_allocfile(&fp, fd)) != 0) {
                DPRINTF(("fd_allocfile %d\n", error));
                return error;
        }
retry:
        /* Find and open a free master pty. */
        *dev = pty_getfree();
        md = minor(*dev);
        if ((error = pty_check(md)) != 0) {
                DPRINTF(("pty_check %d\n", error));
                goto bad;
        }
        if (ptm == NULL) {
                DPRINTF(("no ptm\n"));
                error = EOPNOTSUPP;
                goto bad;
        }
        if ((error = (*ptm->allocvp)(mp, l, &vp, *dev, 'p')) != 0) {
                DPRINTF(("pty_allocvp %d\n", error));
                goto bad;
        }

        if ((error = pty_vn_open(vp, l)) != 0) {
                DPRINTF(("pty_vn_open %d\n", error));
                /*
                 * Check if the master open failed because we lost
                 * the race to grab it.
                 */
                if (error != EIO)
                        goto bad;
                error = !pty_isfree(md, 1);
                DPRINTF(("pty_isfree %d\n", error));
                if (error)
                        goto retry;
                else
                        goto bad;
        }
        fp->f_flag = FREAD|FWRITE|(flags&FMASK);
        fp->f_type = DTYPE_VNODE;
        fp->f_ops = &vnops;
        fp->f_vnode = vp;

        VOP_UNLOCK(vp);
        fd_set_exclose(l, *fd, (flags & O_CLOEXEC) != 0);
        fd_set_foclose(l, *fd, (flags & O_CLOFORK) != 0);
        fd_affix(curproc, fp, *fd);
        return 0;
bad:
        fd_abort(curproc, fp, *fd);
        return error;
}

int
pty_grant_slave(struct lwp *l, dev_t dev, struct mount *mp)
{
        int error;
        struct vnode *vp;

        /*
         * Open the slave.
         * namei -> setattr -> unlock -> revoke -> vrele ->
         * namei -> open -> unlock
         * Three stage rocket:
         * 1. Change the owner and permissions on the slave.
         * 2. Revoke all the users of the slave.
         * 3. open the slave.
         */
        if (ptm == NULL)
                return EOPNOTSUPP;
        if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
                return error;

        if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
                struct vattr vattr;
                (*ptm->getvattr)(mp, l, &vattr);
                /* Do the VOP_SETATTR() as root. */
                error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
                if (error) {
                        DPRINTF(("setattr %d\n", error));
                        vput(vp);
                        return error;
                }
        }
        VOP_UNLOCK(vp);
        VOP_REVOKE(vp, REVOKEALL);

        /*
         * The vnode is useless after the revoke, we need to get it again.
         */
        vrele(vp);
        return 0;
}

static int
pty_alloc_slave(struct lwp *l, int *fd, dev_t dev, struct mount *mp)
{
        int error;
        struct file *fp;
        struct vnode *vp;

        /* Grab a filedescriptor for the slave */
        if ((error = fd_allocfile(&fp, fd)) != 0) {
                DPRINTF(("fd_allocfile %d\n", error));
                return error;
        }

        if (ptm == NULL) {
                error = EOPNOTSUPP;
                goto bad;
        }

        if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
                goto bad;
        if ((error = pty_vn_open(vp, l)) != 0)
                goto bad;

        fp->f_flag = FREAD|FWRITE;
        fp->f_type = DTYPE_VNODE;
        fp->f_ops = &vnops;
        fp->f_vnode = vp;
        VOP_UNLOCK(vp);
        fd_affix(curproc, fp, *fd);
        return 0;
bad:
        fd_abort(curproc, fp, *fd);
        return error;
}

struct ptm_pty *
pty_sethandler(struct ptm_pty *nptm)
{
        struct ptm_pty *optm = ptm;
        ptm = nptm;
        return optm;
}

int
pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data, struct mount *mp)
{
        struct ptmget *ptmg = data;
        int error;

        if (ptm == NULL)
                return EOPNOTSUPP;

        ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
        ptmg->sfd = sfd == -1 ? minor(dev) : sfd;

        error = (*ptm->makename)(mp, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
        if (error)
                return error;

        return (*ptm->makename)(mp, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
}

void
/*ARGSUSED*/
ptmattach(int n)
{
        extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
        /* find the major and minor of the pty devices */
        if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
                panic("%s: Can't find pty slave in cdevsw", __func__);
        if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
                panic("%s: Can't find pty master in cdevsw", __func__);
#ifdef COMPAT_BSDPTY
        ptm = &ptm_bsdpty;
#endif
}

static int
/*ARGSUSED*/
ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
{
        int error;
        int fd;
        dev_t ttydev;
        struct mount *mp;

        switch(minor(dev)) {
        case 0:         /* /dev/ptmx */
        case 2:         /* /emul/linux/dev/ptmx */
                if ((error = pty_getmp(l, &mp)) != 0)
                        return error;
                if ((error = pty_alloc_master(l, &fd, &ttydev, mp, flag)) != 0)
                        return error;
                if (minor(dev) == 2) {
                        /*
                         * Linux ptyfs grants the pty right here.
                         * Handle this case here, instead of writing
                         * a new linux module.
                         */
                        if ((error = pty_grant_slave(l, ttydev, mp)) != 0) {
                                file_t *fp = fd_getfile(fd);
                                if (fp != NULL) {
                                        fd_close(fd);
                                }
                                return error;
                        }
                }
                curlwp->l_dupfd = fd;
                return EMOVEFD;
        case 1:         /* /dev/ptm */
                return 0;
        default:
                return ENODEV;
        }
}

static int
/*ARGSUSED*/
ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
{

        return (0);
}

static int
/*ARGSUSED*/
ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
{
        int error;
        dev_t newdev;
        int cfd, sfd;
        file_t *fp;
        struct mount *mp;

        error = 0;
        switch (cmd) {
        case TIOCPTMGET:
                if ((error = pty_getmp(l, &mp)) != 0)
                        return error;

                if ((error = pty_alloc_master(l, &cfd, &newdev, mp, 0)) != 0)
                        return error;

                if ((error = pty_grant_slave(l, newdev, mp)) != 0)
                        goto bad;

                if ((error = pty_alloc_slave(l, &sfd, newdev, mp)) != 0)
                        goto bad;

                /* now, put the indices and names into struct ptmget */
                if ((error = pty_fill_ptmget(l, newdev, cfd, sfd, data, mp)) != 0)
                        goto bad2;
                return 0;
        default:
                MODULE_HOOK_CALL(tty_ptmioctl_60_hook,
                    (dev, cmd, data, flag, l), EPASSTHROUGH, error);
                if (error != EPASSTHROUGH)
                        return error;
                DPRINTF(("ptmioctl EINVAL\n"));
                return EINVAL;
        }
bad2:
        fp = fd_getfile(sfd);
        if (fp != NULL) {
                fd_close(sfd);
        }
 bad:
        fp = fd_getfile(cfd);
        if (fp != NULL) {
                fd_close(cfd);
        }
        return error;
}

const struct cdevsw ptm_cdevsw = {
        .d_open = ptmopen,
        .d_close = ptmclose,
        .d_read = noread,
        .d_write = nowrite,
        .d_ioctl = ptmioctl,
        .d_stop = nullstop,
        .d_tty = notty,
        .d_poll = nopoll,
        .d_mmap = nommap,
        .d_kqfilter = nokqfilter,
        .d_discard = nodiscard,
        .d_flag = D_TTY
};
#endif