/*      $NetBSD: ptyfs_vnops.c,v 1.69 2022/08/05 10:36:02 riastradh Exp $       */

/*
 * Copyright (c) 1993, 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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.
 *
 *      @(#)procfs_vnops.c      8.18 (Berkeley) 5/21/95
 */

/*
 * Copyright (c) 1993 Jan-Simon Pendry
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 *
 *      @(#)procfs_vnops.c      8.18 (Berkeley) 5/21/95
 */

/*
 * ptyfs vnode interface
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ptyfs_vnops.c,v 1.69 2022/08/05 10:36:02 riastradh Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/select.h>
#include <sys/dirent.h>
#include <sys/resourcevar.h>
#include <sys/stat.h>
#include <sys/conf.h>
#include <sys/tty.h>
#include <sys/pty.h>
#include <sys/kauth.h>

#include <uvm/uvm_extern.h>     /* for PAGE_SIZE */

#include <machine/reg.h>

#include <fs/ptyfs/ptyfs.h>
#include <miscfs/genfs/genfs.h>
#include <miscfs/specfs/specdev.h>

MALLOC_DECLARE(M_PTYFSTMP);

/*
 * Vnode Operations.
 *
 */

int     ptyfs_lookup    (void *);
int     ptyfs_open      (void *);
int     ptyfs_close     (void *);
int     ptyfs_access    (void *);
int     ptyfs_getattr   (void *);
int     ptyfs_setattr   (void *);
int     ptyfs_read      (void *);
int     ptyfs_write     (void *);
int     ptyfs_ioctl     (void *);
int     ptyfs_poll      (void *);
int     ptyfs_kqfilter  (void *);
int     ptyfs_readdir   (void *);
int     ptyfs_reclaim   (void *);
int     ptyfs_inactive  (void *);
int     ptyfs_print     (void *);
int     ptyfs_pathconf  (void *);
int     ptyfs_advlock   (void *);

static int ptyfs_update(struct vnode *, const struct timespec *,
    const struct timespec *, int);
static int ptyfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t,
    struct lwp *);
static int ptyfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct lwp *);
static int atoi(const char *, size_t);

/*
 * ptyfs vnode operations.
 */
int (**ptyfs_vnodeop_p)(void *);
const struct vnodeopv_entry_desc ptyfs_vnodeop_entries[] = {
        { &vop_default_desc, vn_default_error },
        { &vop_parsepath_desc, genfs_parsepath },       /* parsepath */
        { &vop_lookup_desc, ptyfs_lookup },             /* lookup */
        { &vop_create_desc, genfs_eopnotsupp },         /* create */
        { &vop_mknod_desc, genfs_eopnotsupp },          /* mknod */
        { &vop_open_desc, ptyfs_open },                 /* open */
        { &vop_close_desc, ptyfs_close },               /* close */
        { &vop_access_desc, ptyfs_access },             /* access */
        { &vop_accessx_desc, genfs_accessx },           /* accessx */
        { &vop_getattr_desc, ptyfs_getattr },           /* getattr */
        { &vop_setattr_desc, ptyfs_setattr },           /* setattr */
        { &vop_read_desc, ptyfs_read },                 /* read */
        { &vop_write_desc, ptyfs_write },               /* write */
        { &vop_fallocate_desc, genfs_eopnotsupp },      /* fallocate */
        { &vop_fdiscard_desc, genfs_eopnotsupp },       /* fdiscard */
        { &vop_ioctl_desc, ptyfs_ioctl },               /* ioctl */
        { &vop_fcntl_desc, genfs_fcntl },               /* fcntl */
        { &vop_poll_desc, ptyfs_poll },                 /* poll */
        { &vop_kqfilter_desc, ptyfs_kqfilter },         /* kqfilter */
        { &vop_revoke_desc, genfs_revoke },             /* revoke */
        { &vop_mmap_desc, genfs_eopnotsupp },           /* mmap */
        { &vop_fsync_desc, genfs_nullop },              /* fsync */
        { &vop_seek_desc, genfs_nullop },               /* seek */
        { &vop_remove_desc, genfs_eopnotsupp },         /* remove */
        { &vop_link_desc, genfs_eopnotsupp },           /* link */
        { &vop_rename_desc, genfs_eopnotsupp },         /* rename */
        { &vop_mkdir_desc, genfs_eopnotsupp },          /* mkdir */
        { &vop_rmdir_desc, genfs_eopnotsupp },          /* rmdir */
        { &vop_symlink_desc, genfs_eopnotsupp },        /* symlink */
        { &vop_readdir_desc, ptyfs_readdir },           /* readdir */
        { &vop_readlink_desc, genfs_eopnotsupp },       /* readlink */
        { &vop_abortop_desc, genfs_abortop },           /* abortop */
        { &vop_inactive_desc, ptyfs_inactive },         /* inactive */
        { &vop_reclaim_desc, ptyfs_reclaim },           /* reclaim */
        { &vop_lock_desc, genfs_lock },                 /* lock */
        { &vop_unlock_desc, genfs_unlock },             /* unlock */
        { &vop_bmap_desc, genfs_eopnotsupp },           /* bmap */
        { &vop_strategy_desc, genfs_badop },            /* strategy */
        { &vop_print_desc, ptyfs_print },               /* print */
        { &vop_islocked_desc, genfs_islocked },         /* islocked */
        { &vop_pathconf_desc, ptyfs_pathconf },         /* pathconf */
        { &vop_advlock_desc, ptyfs_advlock },           /* advlock */
        { &vop_bwrite_desc, genfs_eopnotsupp },         /* bwrite */
        { &vop_putpages_desc, genfs_null_putpages },    /* putpages */
        { NULL, NULL }
};
const struct vnodeopv_desc ptyfs_vnodeop_opv_desc =
        { &ptyfs_vnodeop_p, ptyfs_vnodeop_entries };

/*
 * free any private data and remove the node
 * from any private lists.
 */
int
ptyfs_reclaim(void *v)
{
        struct vop_reclaim_v2_args /* {
                struct vnode *a_vp;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;

        VOP_UNLOCK(vp);

        vp->v_data = NULL;
        return 0;
}

int
ptyfs_inactive(void *v)
{
        struct vop_inactive_v2_args /* {
                struct vnode *a_vp;
                bool *a_recycle;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);

        if (ptyfs->ptyfs_type == PTYFSptc)
                ptyfs_clr_active(vp->v_mount, ptyfs->ptyfs_pty);

        return 0;
}

/*
 * Return POSIX pathconf information applicable to special devices.
 */
int
ptyfs_pathconf(void *v)
{
        struct vop_pathconf_args /* {
                struct vnode *a_vp;
                int a_name;
                register_t *a_retval;
        } */ *ap = v;

        switch (ap->a_name) {
        case _PC_LINK_MAX:
                *ap->a_retval = LINK_MAX;
                return 0;
        case _PC_MAX_CANON:
                *ap->a_retval = MAX_CANON;
                return 0;
        case _PC_MAX_INPUT:
                *ap->a_retval = MAX_INPUT;
                return 0;
        case _PC_PIPE_BUF:
                *ap->a_retval = PIPE_BUF;
                return 0;
        case _PC_CHOWN_RESTRICTED:
                *ap->a_retval = 1;
                return 0;
        case _PC_VDISABLE:
                *ap->a_retval = _POSIX_VDISABLE;
                return 0;
        case _PC_SYNC_IO:
                *ap->a_retval = 1;
                return 0;
        default:
                return genfs_pathconf(ap);
        }
}

/*
 * _print is used for debugging.
 * just print a readable description
 * of (vp).
 */
int
ptyfs_print(void *v)
{
        struct vop_print_args /* {
                struct vnode *a_vp;
        } */ *ap = v;
        struct ptyfsnode *ptyfs = VTOPTYFS(ap->a_vp);

        printf("tag VT_PTYFS, type %d, pty %d\n",
            ptyfs->ptyfs_type, ptyfs->ptyfs_pty);
        return 0;
}

/*
 * support advisory locking on pty nodes
 */
int
ptyfs_advlock(void *v)
{
        struct vop_print_args /* {
                struct vnode *a_vp;
        } */ *ap = v;
        struct ptyfsnode *ptyfs = VTOPTYFS(ap->a_vp);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                return spec_advlock(v);
        default:
                return EOPNOTSUPP;
        }
}

/*
 * Invent attributes for ptyfsnode (vp) and store
 * them in (vap).
 * Directories lengths are returned as zero since
 * any real length would require the genuine size
 * to be computed, and nothing cares anyway.
 *
 * this is relatively minimal for ptyfs.
 */
int
ptyfs_getattr(void *v)
{
        struct vop_getattr_args /* {
                struct vnode *a_vp;
                struct vattr *a_vap;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct ptyfsnode *ptyfs = VTOPTYFS(ap->a_vp);
        struct vattr *vap = ap->a_vap;

        PTYFS_ITIMES(ptyfs, NULL, NULL, NULL);

        /* start by zeroing out the attributes */
        vattr_null(vap);

        /* next do all the common fields */
        vap->va_type = ap->a_vp->v_type;
        vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsidx.__fsid_val[0];
        vap->va_fileid = ptyfs->ptyfs_fileno;
        vap->va_gen = 0;
        vap->va_flags = 0;
        vap->va_blocksize = PAGE_SIZE;

        vap->va_atime = ptyfs->ptyfs_atime;
        vap->va_mtime = ptyfs->ptyfs_mtime;
        vap->va_ctime = ptyfs->ptyfs_ctime;
        vap->va_birthtime = ptyfs->ptyfs_birthtime;
        vap->va_mode = ptyfs->ptyfs_mode;
        vap->va_flags = ptyfs->ptyfs_flags;
        vap->va_uid = ptyfs->ptyfs_uid;
        vap->va_gid = ptyfs->ptyfs_gid;

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                if (pty_isfree(ptyfs->ptyfs_pty, 1))
                        return ENOENT;
                vap->va_bytes = vap->va_size = 0;
                vap->va_rdev = ap->a_vp->v_rdev;
                vap->va_nlink = 1;
                break;
        case PTYFSroot:
                vap->va_rdev = 0;
                vap->va_bytes = vap->va_size = DEV_BSIZE;
                vap->va_nlink = 2;
                break;
        default:
                return EOPNOTSUPP;
        }

        return 0;
}

/*ARGSUSED*/
int
ptyfs_setattr(void *v)
{
        struct vop_setattr_args /* {
                struct vnodeop_desc *a_desc;
                struct vnode *a_vp;
                struct vattr *a_vap;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);
        struct vattr *vap = ap->a_vap;
        kauth_cred_t cred = ap->a_cred;
        struct lwp *l = curlwp;
        int error;
        kauth_action_t action = KAUTH_VNODE_WRITE_FLAGS;
        bool changing_sysflags = false;

        if (vap->va_size != VNOVALSIZE) {
                switch (ptyfs->ptyfs_type) {
                case PTYFSroot:
                        return EISDIR;
                case PTYFSpts:
                case PTYFSptc:
                        break;
                default:
                        return EINVAL;
                }
        }

        if (vap->va_flags != VNOVALFLAGS) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return EROFS;

                /* Immutable and append-only flags are not supported on ptyfs. */
                if (vap->va_flags & (IMMUTABLE | APPEND))
                        return EINVAL;

                /* Snapshot flag cannot be set or cleared */
                if ((vap->va_flags & SF_SNAPSHOT) != (ptyfs->ptyfs_flags & SF_SNAPSHOT))
                        return EPERM;

                if ((ptyfs->ptyfs_flags & SF_SETTABLE) != (vap->va_flags & SF_SETTABLE)) {
                        changing_sysflags = true;
                        action |= KAUTH_VNODE_WRITE_SYSFLAGS;
                }

                error = kauth_authorize_vnode(cred, action, vp, NULL,
                    genfs_can_chflags(vp, cred, ptyfs->ptyfs_uid,
                    changing_sysflags));
                if (error)
                        return error;

                if (changing_sysflags) {
                        ptyfs->ptyfs_flags = vap->va_flags;
                } else {
                        ptyfs->ptyfs_flags &= SF_SETTABLE;
                        ptyfs->ptyfs_flags |= (vap->va_flags & UF_SETTABLE);
                }
                ptyfs->ptyfs_status |= PTYFS_CHANGE;
        }

        /*
         * Go through the fields and update iff not VNOVAL.
         */
        if (vap->va_uid != (uid_t)VNOVAL || vap->va_gid != (gid_t)VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return EROFS;
                error = ptyfs_chown(vp, vap->va_uid, vap->va_gid, cred, l);
                if (error)
                        return error;
        }

        if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL ||
            vap->va_birthtime.tv_sec != VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return EROFS;
                if ((ptyfs->ptyfs_flags & SF_SNAPSHOT) != 0)
                        return EPERM;
                error = kauth_authorize_vnode(cred, KAUTH_VNODE_WRITE_TIMES, vp,
                    NULL, genfs_can_chtimes(vp, cred, ptyfs->ptyfs_uid,
                    vap->va_vaflags));
                if (error)
                        return (error);
                if (vap->va_atime.tv_sec != VNOVAL)
                        if (!(vp->v_mount->mnt_flag & MNT_NOATIME))
                                ptyfs->ptyfs_status |= PTYFS_ACCESS;
                if (vap->va_mtime.tv_sec != VNOVAL) {
                        ptyfs->ptyfs_status |= PTYFS_CHANGE | PTYFS_MODIFY;
                        if (vp->v_mount->mnt_flag & MNT_RELATIME)
                                ptyfs->ptyfs_status |= PTYFS_ACCESS;
                }
                if (vap->va_birthtime.tv_sec != VNOVAL)
                        ptyfs->ptyfs_birthtime = vap->va_birthtime;
                ptyfs->ptyfs_status |= PTYFS_CHANGE;
                error = ptyfs_update(vp, &vap->va_atime, &vap->va_mtime, 0);
                if (error)
                        return error;
        }
        if (vap->va_mode != (mode_t)VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return EROFS;
                if ((ptyfs->ptyfs_flags & SF_SNAPSHOT) != 0 &&
                    (vap->va_mode &
                    (S_IXUSR|S_IWUSR|S_IXGRP|S_IWGRP|S_IXOTH|S_IWOTH)))
                        return EPERM;
                error = ptyfs_chmod(vp, vap->va_mode, cred, l);
                if (error)
                        return error;
        }
        return 0;
}

/*
 * Change the mode on a file.
 * Inode must be locked before calling.
 */
static int
ptyfs_chmod(struct vnode *vp, mode_t mode, kauth_cred_t cred, struct lwp *l)
{
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);
        int error;

        error = kauth_authorize_vnode(cred, KAUTH_VNODE_WRITE_SECURITY, vp,
            NULL, genfs_can_chmod(vp, cred, ptyfs->ptyfs_uid, ptyfs->ptyfs_gid,
            mode));
        if (error)
                return (error);

        ptyfs->ptyfs_mode &= ~ALLPERMS;
        ptyfs->ptyfs_mode |= (mode & ALLPERMS);
        return 0;
}

/*
 * Perform chown operation on inode ip;
 * inode must be locked prior to call.
 */
static int
ptyfs_chown(struct vnode *vp, uid_t uid, gid_t gid, kauth_cred_t cred,
    struct lwp *l)
{
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);
        int error;

        if (uid == (uid_t)VNOVAL)
                uid = ptyfs->ptyfs_uid;
        if (gid == (gid_t)VNOVAL)
                gid = ptyfs->ptyfs_gid;

        error = kauth_authorize_vnode(cred, KAUTH_VNODE_CHANGE_OWNERSHIP, vp,
            NULL, genfs_can_chown(vp, cred, ptyfs->ptyfs_uid, ptyfs->ptyfs_gid,
            uid, gid));
        if (error)
                return (error);

        ptyfs->ptyfs_gid = gid;
        ptyfs->ptyfs_uid = uid;
        return 0;
}

/*
 * implement access checking.
 *
 * actually, the check for super-user is slightly
 * broken since it will allow read access to write-only
 * objects.  this doesn't cause any particular trouble
 * but does mean that the i/o entry points need to check
 * that the operation really does make sense.
 */
int
ptyfs_access(void *v)
{
        struct vop_access_args /* {
                struct vnode *a_vp;
                accmode_t a_accmode;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct vattr va;
        int error;

        if ((error = VOP_GETATTR(ap->a_vp, &va, ap->a_cred)) != 0)
                return error;

        return kauth_authorize_vnode(ap->a_cred,
            KAUTH_ACCESS_ACTION(ap->a_accmode, ap->a_vp->v_type, va.va_mode),
            ap->a_vp, NULL, genfs_can_access(ap->a_vp, ap->a_cred, va.va_uid,
            va.va_gid, va.va_mode, NULL, ap->a_accmode));
}

/*
 * lookup.  this is incredibly complicated in the
 * general case, however for most pseudo-filesystems
 * very little needs to be done.
 *
 * Locking isn't hard here, just poorly documented.
 *
 * If we're looking up ".", just vref the parent & return it.
 *
 * If we're looking up "..", unlock the parent, and lock "..". If everything
 * went ok, try to re-lock the parent. We do this to prevent lock races.
 *
 * For anything else, get the needed node.
 *
 * We try to exit with the parent locked in error cases.
 */
int
ptyfs_lookup(void *v)
{
        struct vop_lookup_v2_args /* {
                struct vnode * a_dvp;
                struct vnode ** a_vpp;
                struct componentname * a_cnp;
        } */ *ap = v;
        struct componentname *cnp = ap->a_cnp;
        struct vnode **vpp = ap->a_vpp;
        struct vnode *dvp = ap->a_dvp;
        const char *pname = cnp->cn_nameptr;
        struct ptyfsnode *ptyfs;
        int pty, error;

        *vpp = NULL;

        if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)
                return EROFS;

        if (cnp->cn_namelen == 1 && *pname == '.') {
                *vpp = dvp;
                vref(dvp);
                return 0;
        }

        ptyfs = VTOPTYFS(dvp);
        switch (ptyfs->ptyfs_type) {
        case PTYFSroot:
                /*
                 * Shouldn't get here with .. in the root node.
                 */
                if (cnp->cn_flags & ISDOTDOT)
                        return EIO;

                pty = atoi(pname, cnp->cn_namelen);
                if (pty < 0 || ptyfs_next_active(dvp->v_mount, pty) != pty)
                        break;
                error = ptyfs_allocvp(dvp->v_mount, vpp, PTYFSpts, pty);
                if (error)
                        return error;
                if (ptyfs_next_active(dvp->v_mount, pty) != pty) {
                        vrele(*vpp);
                        *vpp = NULL;
                        return ENOENT;
                }
                return 0;

        default:
                return ENOTDIR;
        }

        return cnp->cn_nameiop == LOOKUP ? ENOENT : EROFS;
}

/*
 * readdir returns directory entries from ptyfsnode (vp).
 *
 * the strategy here with ptyfs is to generate a single
 * directory entry at a time (struct dirent) and then
 * copy that out to userland using uiomove.  a more efficient
 * though more complex implementation, would try to minimize
 * the number of calls to uiomove().  for ptyfs, this is
 * hardly worth the added code complexity.
 *
 * this should just be done through read()
 */
int
ptyfs_readdir(void *v)
{
        struct vop_readdir_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                kauth_cred_t a_cred;
                int *a_eofflag;
                off_t **a_cookies;
                int *a_ncookies;
        } */ *ap = v;
        struct uio *uio = ap->a_uio;
        struct dirent *dp;
        struct ptyfsnode *ptyfs;
        off_t i;
        int error;
        off_t *cookies = NULL;
        int ncookies;
        struct vnode *vp;
        int n, nc = 0;

        vp = ap->a_vp;
        ptyfs = VTOPTYFS(vp);

        if (uio->uio_resid < UIO_MX)
                return EINVAL;
        if (uio->uio_offset < 0)
                return EINVAL;

        dp = malloc(sizeof(struct dirent), M_PTYFSTMP, M_WAITOK | M_ZERO);

        error = 0;
        i = uio->uio_offset;
        dp->d_reclen = UIO_MX;
        ncookies = uio->uio_resid / UIO_MX;

        if (ptyfs->ptyfs_type != PTYFSroot) {
                error = ENOTDIR;
                goto out;
        }

        if (i >= npty)
                goto out;

        if (ap->a_ncookies) {
                ncookies = uimin(ncookies, (npty + 2 - i));
                cookies = malloc(ncookies * sizeof (off_t),
                    M_TEMP, M_WAITOK);
                *ap->a_cookies = cookies;
        }

        for (; i < 2 && uio->uio_resid >= UIO_MX; i++) {
                /* `.' and/or `..' */
                dp->d_fileno = PTYFS_FILENO(PTYFSroot, 0);
                dp->d_namlen = i + 1;
                (void)memcpy(dp->d_name, "..", dp->d_namlen);
                dp->d_name[i + 1] = '\0';
                dp->d_type = DT_DIR;
                if ((error = uiomove(dp, UIO_MX, uio)) != 0)
                        goto out;
                if (cookies)
                        *cookies++ = i + 1;
                nc++;
        }
        while (uio->uio_resid >= UIO_MX) {
                /* check for used ptys */
                n = ptyfs_next_active(vp->v_mount, i - 2);
                if (n < 0)
                        break;
                dp->d_fileno = PTYFS_FILENO(PTYFSpts, n);
                dp->d_namlen = snprintf(dp->d_name, sizeof(dp->d_name),
                    "%lld", (long long)(n));
                dp->d_type = DT_CHR;
                if ((error = uiomove(dp, UIO_MX, uio)) != 0)
                        goto out;
                i = n + 3;
                if (cookies)
                        *cookies++ = i;
                nc++;
        }

out:
        /* not pertinent in error cases */
        ncookies = nc;

        if (ap->a_ncookies) {
                if (error) {
                        if (cookies)
                                free(*ap->a_cookies, M_TEMP);
                        *ap->a_ncookies = 0;
                        *ap->a_cookies = NULL;
                } else
                        *ap->a_ncookies = ncookies;
        }
        uio->uio_offset = i;
        free(dp, M_PTYFSTMP);
        return error;
}

int
ptyfs_open(void *v)
{
        struct vop_open_args /* {
                struct vnode *a_vp;
                int  a_mode;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                return spec_open(v);
        case PTYFSroot:
                return 0;
        default:
                return EINVAL;
        }
}

int
ptyfs_close(void *v)
{
        struct vop_close_args /* {
                struct vnode *a_vp;
                int  a_fflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);

        mutex_enter(vp->v_interlock);
        if (vrefcnt(vp) > 1)
                PTYFS_ITIMES(ptyfs, NULL, NULL, NULL);
        mutex_exit(vp->v_interlock);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                return spec_close(v);
        case PTYFSroot:
                return 0;
        default:
                return EINVAL;
        }
}

int
ptyfs_read(void *v)
{
        struct vop_read_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct timespec ts;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);
        int error;

        if (vp->v_type == VDIR)
                return EISDIR;

        ptyfs->ptyfs_status |= PTYFS_ACCESS;
        /* hardclock() resolution is good enough for ptyfs */
        getnanotime(&ts);
        (void)ptyfs_update(vp, &ts, &ts, 0);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                VOP_UNLOCK(vp);
                error = cdev_read(vp->v_rdev, ap->a_uio, ap->a_ioflag);
                vn_lock(vp, LK_RETRY|LK_EXCLUSIVE);
                return error;
        default:
                return EOPNOTSUPP;
        }
}

int
ptyfs_write(void *v)
{
        struct vop_write_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct timespec ts;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);
        int error;

        ptyfs->ptyfs_status |= PTYFS_MODIFY;
        getnanotime(&ts);
        (void)ptyfs_update(vp, &ts, &ts, 0);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                VOP_UNLOCK(vp);
                error = cdev_write(vp->v_rdev, ap->a_uio, ap->a_ioflag);
                vn_lock(vp, LK_RETRY|LK_EXCLUSIVE);
                return error;
        default:
                return EOPNOTSUPP;
        }
}

int
ptyfs_ioctl(void *v)
{
        struct vop_ioctl_args /* {
                struct vnode *a_vp;
                u_long a_command;
                void *a_data;
                int  a_fflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                return cdev_ioctl(vp->v_rdev, ap->a_command,
                    ap->a_data, ap->a_fflag, curlwp);
        default:
                return EOPNOTSUPP;
        }
}

int
ptyfs_poll(void *v)
{
        struct vop_poll_args /* {
                struct vnode *a_vp;
                int a_events;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                return cdev_poll(vp->v_rdev, ap->a_events, curlwp);
        default:
                return genfs_poll(v);
        }
}

int
ptyfs_kqfilter(void *v)
{
        struct vop_kqfilter_args /* {
                struct vnode *a_vp;
                struct knote *a_kn;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);

        switch (ptyfs->ptyfs_type) {
        case PTYFSpts:
        case PTYFSptc:
                return cdev_kqfilter(vp->v_rdev, ap->a_kn);
        default:
                return genfs_kqfilter(v);
        }
}

static int
ptyfs_update(struct vnode *vp, const struct timespec *acc,
    const struct timespec *mod, int flags)
{
        struct ptyfsnode *ptyfs = VTOPTYFS(vp);

        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                return 0;

        PTYFS_ITIMES(ptyfs, acc, mod, NULL);
        return 0;
}

void
ptyfs_itimes(struct ptyfsnode *ptyfs, const struct timespec *acc,
    const struct timespec *mod, const struct timespec *cre)
{
        struct timespec now;
 
        KASSERT(ptyfs->ptyfs_status & (PTYFS_ACCESS|PTYFS_CHANGE|PTYFS_MODIFY));

        getnanotime(&now);
        if (ptyfs->ptyfs_status & PTYFS_ACCESS) {
                if (acc == NULL)
                        acc = &now;
                ptyfs->ptyfs_atime = *acc;
        }
        if (ptyfs->ptyfs_status & PTYFS_MODIFY) {
                if (mod == NULL)
                        mod = &now;
                ptyfs->ptyfs_mtime = *mod;
        }
        if (ptyfs->ptyfs_status & PTYFS_CHANGE) {
                if (cre == NULL)
                        cre = &now;
                ptyfs->ptyfs_ctime = *cre;
        }
        ptyfs->ptyfs_status &= ~(PTYFS_ACCESS|PTYFS_CHANGE|PTYFS_MODIFY);
}

/*
 * convert decimal ascii to int
 */
static int
atoi(const char *b, size_t len)
{
        int p = 0;

        while (len--) {
                char c = *b++;
                if (c < '0' || c > '9')
                        return -1;
                p = 10 * p + (c - '0');
        }

        return p;
}