/*      $NetBSD: ptyfs_vfsops.c,v 1.58 2020/03/16 21:20:10 pgoyette Exp $       */

/*
 * Copyright (c) 1992, 1993, 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software donated 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.
 *
 */

/*
 * Pseudo-tty Filesystem
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ptyfs_vfsops.c,v 1.58 2020/03/16 21:20:10 pgoyette Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/conf.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/stat.h>
#include <sys/dirent.h>
#include <sys/malloc.h>
#include <sys/syslog.h>
#include <sys/select.h>
#include <sys/filedesc.h>
#include <sys/tty.h>
#include <sys/pty.h>
#include <sys/kauth.h>
#include <sys/module.h>

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

MODULE(MODULE_CLASS_VFS, ptyfs, NULL);

MALLOC_JUSTDEFINE(M_PTYFSMNT, "ptyfs mount", "ptyfs mount structures");
MALLOC_JUSTDEFINE(M_PTYFSTMP, "ptyfs temp", "ptyfs temporary structures");

VFS_PROTOS(ptyfs);

static int ptyfs__allocvp(struct mount *, struct lwp *, struct vnode **,
    dev_t, char);
static int ptyfs__makename(struct mount *, struct lwp *, char *, size_t,
    dev_t, char);
static void ptyfs__getvattr(struct mount *, struct lwp *, struct vattr *);
static int ptyfs__getmp(struct lwp *, struct mount **);

/*
 * ptm glue: When we mount, we make ptm point to us.
 */
struct ptm_pty *ptyfs_save_ptm;
static int ptyfs_count;

static TAILQ_HEAD(, ptyfsmount) ptyfs_head;

struct ptm_pty ptm_ptyfspty = {
        ptyfs__allocvp,
        ptyfs__makename,
        ptyfs__getvattr,
        ptyfs__getmp,
};

static int
ptyfs__getmp(struct lwp *l, struct mount **mpp)
{
        struct cwdinfo *cwdi = l->l_proc->p_cwdi;
        struct mount *mp;
        struct ptyfsmount *pmnt;
 
        TAILQ_FOREACH(pmnt, &ptyfs_head, pmnt_le) {
                mp = pmnt->pmnt_mp;
                if (cwdi->cwdi_rdir == NULL)
                        goto ok;

                if (vn_isunder(mp->mnt_vnodecovered, cwdi->cwdi_rdir, l))
                        goto ok;
        }
        *mpp = NULL;
        return EOPNOTSUPP;
ok:
        *mpp = mp;
        return 0;
}

static const char *
ptyfs__getpath(struct lwp *l, const struct mount *mp)
{
#define MAXBUF (sizeof(mp->mnt_stat.f_mntonname) + 32)
        struct cwdinfo *cwdi = l->l_proc->p_cwdi;
        char *buf;
        const char *rv;
        size_t len;
        char *bp;
        int error;

        rv = mp->mnt_stat.f_mntonname;
        if (cwdi->cwdi_rdir == NULL)
                return rv;

        buf = malloc(MAXBUF, M_TEMP, M_WAITOK);
        bp = buf + MAXBUF;
        *--bp = '\0';
        error = getcwd_common(mp->mnt_vnodecovered, cwdi->cwdi_rdir, &bp,
            buf, MAXBUF / 2, 0, l);
        if (error) {    /* Mount point is out of rdir */
                rv = NULL;
                goto out;
        }

        len = strlen(bp);
        if (len < sizeof(mp->mnt_stat.f_mntonname))     /* XXX */
                rv += strlen(rv) - len;
out:
        free(buf, M_TEMP);
        return rv;
}

static int
ptyfs__makename(struct mount *mp, struct lwp *l, char *tbuf, size_t bufsiz,
    dev_t dev, char ms)
{
        size_t len;
        const char *np;
        int pty = minor(dev);

        switch (ms) {
        case 'p':
                /* We don't provide access to the master, should we? */
                len = snprintf(tbuf, bufsiz, "/dev/null");
                break;
        case 't':
                /*
                 * We support traditional ptys, so we can get here,
                 * if pty had been opened before PTYFS was mounted,
                 * or was opened through /dev/ptyXX devices.
                 * Return it only outside chroot for more security .
                 */
                if (l->l_proc->p_cwdi->cwdi_rdir == NULL
                    && ptyfs_save_ptm != NULL 
                    && ptyfs_next_active(mp, pty) != pty)
                        return (*ptyfs_save_ptm->makename)(mp, l,
                            tbuf, bufsiz, dev, ms);

                np = ptyfs__getpath(l, mp);
                if (np == NULL)
                        return EOPNOTSUPP;
                len = snprintf(tbuf, bufsiz, "%s/%llu", np,
                        (unsigned long long)minor(dev));
                break;
        default:
                return EINVAL;
        }

        return len >= bufsiz ? ENOSPC : 0;
}


static int
/*ARGSUSED*/
ptyfs__allocvp(struct mount *mp, struct lwp *l, struct vnode **vpp,
    dev_t dev, char ms)
{
        int error;
        ptyfstype type;

        switch (ms) {
        case 'p':
                type = PTYFSptc;
                break;
        case 't':
                type = PTYFSpts;
                break;
        default:
                return EINVAL;
        }

        error = ptyfs_allocvp(mp, vpp, type, minor(dev));
        if (error)
                return error;
        error = vn_lock(*vpp, LK_EXCLUSIVE);
        if (error) {
                vrele(*vpp);
                *vpp = NULL;
                return error;
        }
        if (type == PTYFSptc)
                ptyfs_set_active(mp, minor(dev));
        return 0;
}


static void
ptyfs__getvattr(struct mount *mp, struct lwp *l, struct vattr *vattr)
{
        struct ptyfsmount *pmnt = VFSTOPTY(mp);
        vattr_null(vattr);
        /* get real uid */
        vattr->va_uid = kauth_cred_getuid(l->l_cred);
        vattr->va_gid = pmnt->pmnt_gid;
        vattr->va_mode = pmnt->pmnt_mode;
}


void
ptyfs_init(void)
{

        TAILQ_INIT(&ptyfs_head);
        malloc_type_attach(M_PTYFSMNT);
        malloc_type_attach(M_PTYFSTMP);
        ptyfs_hashinit();
}

void
ptyfs_reinit(void)
{

}

void
ptyfs_done(void)
{

        ptyfs_hashdone();
        malloc_type_detach(M_PTYFSTMP);
        malloc_type_detach(M_PTYFSMNT);
}

#define OSIZE sizeof(struct { int f; gid_t g; mode_t m; })
/*
 * Mount the Pseudo tty params filesystem
 */
int
ptyfs_mount(struct mount *mp, const char *path, void *data, size_t *data_len)
{
        struct lwp *l = curlwp;
        int error = 0;
        struct ptyfsmount *pmnt;
        struct ptyfs_args *args = data;

        if (args == NULL)
                return EINVAL;
        if (*data_len != sizeof *args) {
                if (*data_len != OSIZE || args->version >= PTYFS_ARGSVERSION)
                        return EINVAL;
        }

        if (UIO_MX & (UIO_MX - 1)) {
                log(LOG_ERR, "ptyfs: invalid directory entry size");
                return EINVAL;
        }

        if (mp->mnt_flag & MNT_GETARGS) {
                pmnt = VFSTOPTY(mp);
                if (pmnt == NULL)
                        return EIO;
                args->mode = pmnt->pmnt_mode;
                args->gid = pmnt->pmnt_gid;
                if (args->version >= PTYFS_ARGSVERSION) {
                        args->flags = pmnt->pmnt_flags;
                        *data_len = sizeof *args;
                } else {
                        *data_len = OSIZE;
                }
                return 0;
        }

#if 0
        /* Don't allow more than one mount */
        if (ptyfs_count)
                return EBUSY;
#endif

        if (mp->mnt_flag & MNT_UPDATE)
                return EOPNOTSUPP;

        if (args->version > PTYFS_ARGSVERSION)
                return EINVAL;

        pmnt = malloc(sizeof(struct ptyfsmount), M_PTYFSMNT, M_WAITOK);

        mp->mnt_data = pmnt;
        mutex_init(&pmnt->pmnt_lock, MUTEX_DEFAULT, IPL_NONE);
        pmnt->pmnt_gid = args->gid;
        pmnt->pmnt_mode = args->mode;
        if (args->version >= PTYFS_ARGSVERSION)
                pmnt->pmnt_flags = args->flags;
        else
                pmnt->pmnt_flags = 0;
        pmnt->pmnt_bitmap_size = 0;
        pmnt->pmnt_bitmap = NULL;
        mp->mnt_flag |= MNT_LOCAL;
        vfs_getnewfsid(mp);

        if ((error = set_statvfs_info(path, UIO_USERSPACE, "ptyfs",
            UIO_SYSSPACE, mp->mnt_op->vfs_name, mp, l)) != 0) {
                free(pmnt, M_PTYFSMNT);
                return error;
        }

        pmnt->pmnt_mp = mp;
        TAILQ_INSERT_TAIL(&ptyfs_head, pmnt, pmnt_le);
        if (ptyfs_count++ == 0) {
                /* Point pty access to us */
                ptyfs_save_ptm = pty_sethandler(&ptm_ptyfspty);
        }
        return 0;
}

/*ARGSUSED*/
int
ptyfs_start(struct mount *mp, int flags)
{
        return 0;
}

/*ARGSUSED*/
int
ptyfs_unmount(struct mount *mp, int mntflags)
{
        int error;
        int flags = 0;
        struct ptyfsmount *pmnt;

        if (mntflags & MNT_FORCE)
                flags |= FORCECLOSE;

        if ((error = vflush(mp, 0, flags)) != 0)
                return error;

        ptyfs_count--;
        if (ptyfs_count == 0) {
                /* Restore where pty access was pointing */
                (void)pty_sethandler(ptyfs_save_ptm);
                ptyfs_save_ptm = NULL;
        }
        TAILQ_FOREACH(pmnt, &ptyfs_head, pmnt_le) {
                if (pmnt->pmnt_mp == mp) {
                        TAILQ_REMOVE(&ptyfs_head, pmnt, pmnt_le);
                        break;
                }
        }

        /*
         * Finally, throw away the ptyfsmount structure
         */
        if (pmnt->pmnt_bitmap_size > 0)
                kmem_free(pmnt->pmnt_bitmap, pmnt->pmnt_bitmap_size);
        mutex_destroy(&pmnt->pmnt_lock);
        free(mp->mnt_data, M_PTYFSMNT);
        mp->mnt_data = NULL;

        return 0;
}

int
ptyfs_root(struct mount *mp, int lktype, struct vnode **vpp)
{
        int error;

        /* setup "." */
        error = ptyfs_allocvp(mp, vpp, PTYFSroot, 0);
        if (error)
                return error;
        error = vn_lock(*vpp, lktype);
        if (error) {
                vrele(*vpp);
                *vpp = NULL;
                return error;
        }
        return 0;
}

/*ARGSUSED*/
int
ptyfs_sync(struct mount *mp, int waitfor,
    kauth_cred_t uc)
{
        return 0;
}

/*
 * Initialize this vnode / ptynode pair.
 * Only for the slave side of a pty, caller assures
 * no other thread will try to load this node.
 */
int
ptyfs_loadvnode(struct mount *mp, struct vnode *vp,
    const void *key, size_t key_len, const void **new_key)
{
        struct ptyfskey pkey;
        struct ptyfsnode *ptyfs;

        KASSERT(key_len == sizeof(pkey));
        memcpy(&pkey, key, key_len);

        ptyfs = ptyfs_get_node(pkey.ptk_type, pkey.ptk_pty);
        KASSERT(memcmp(&ptyfs->ptyfs_key, &pkey, sizeof(pkey)) == 0);

        switch (pkey.ptk_type) {
        case PTYFSroot: /* /pts = dr-xr-xr-x */
                vp->v_type = VDIR;
                vp->v_vflag = VV_ROOT;
                break;

        case PTYFSpts:  /* /pts/N = cxxxxxxxxx */
        case PTYFSptc:  /* controlling side = cxxxxxxxxx */
                vp->v_type = VCHR;
                spec_node_init(vp, PTYFS_MAKEDEV(ptyfs));
                break;
        default:
                panic("ptyfs_loadvnode");
        }

        vp->v_tag = VT_PTYFS;
        vp->v_op = ptyfs_vnodeop_p;
        vp->v_data = ptyfs;
        uvm_vnp_setsize(vp, 0);
        *new_key = &ptyfs->ptyfs_key;
        return 0;
}

/*
 * Kernfs flat namespace lookup.
 * Currently unsupported.
 */
/*ARGSUSED*/
int
ptyfs_vget(struct mount *mp, ino_t ino, int lktype,
    struct vnode **vpp)
{
        return EOPNOTSUPP;
}

extern const struct vnodeopv_desc ptyfs_vnodeop_opv_desc;

const struct vnodeopv_desc * const ptyfs_vnodeopv_descs[] = {
        &ptyfs_vnodeop_opv_desc,
        NULL,
};

struct vfsops ptyfs_vfsops = {
        .vfs_name = MOUNT_PTYFS,
        .vfs_min_mount_data = sizeof (struct ptyfs_args),
        .vfs_mount = ptyfs_mount,
        .vfs_start = ptyfs_start,
        .vfs_unmount = ptyfs_unmount,
        .vfs_root = ptyfs_root,
        .vfs_quotactl = (void *)eopnotsupp,
        .vfs_statvfs = genfs_statvfs,
        .vfs_sync = ptyfs_sync,
        .vfs_vget = ptyfs_vget,
        .vfs_loadvnode = ptyfs_loadvnode,
        .vfs_fhtovp = (void *)eopnotsupp,
        .vfs_vptofh = (void *)eopnotsupp,
        .vfs_init = ptyfs_init,
        .vfs_reinit = ptyfs_reinit,
        .vfs_done = ptyfs_done,
        .vfs_snapshot = (void *)eopnotsupp,
        .vfs_extattrctl = (void *)eopnotsupp,
        .vfs_suspendctl = genfs_suspendctl,
        .vfs_renamelock_enter = genfs_renamelock_enter,
        .vfs_renamelock_exit = genfs_renamelock_exit,
        .vfs_fsync = (void *)eopnotsupp,
        .vfs_opv_descs = ptyfs_vnodeopv_descs
};

SYSCTL_SETUP(ptyfs_sysctl_setup, "ptyfs sysctl")
{

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "ptyfs",
                       SYSCTL_DESCR("Pty file system"),
                       NULL, 0, NULL, 0,
                       CTL_VFS, 23, CTL_EOL);
        /*
         * XXX the "23" above could be dynamic, thereby eliminating
         * one more instance of the "number to vfs" mapping problem,
         * but "23" is the order as taken from sys/mount.h
         */
}

static int
ptyfs_modcmd(modcmd_t cmd, void *arg)
{
        int error;

        switch (cmd) {
        case MODULE_CMD_INIT:
                error = vfs_attach(&ptyfs_vfsops);
                if (error != 0)
                        break;
                break;
        case MODULE_CMD_FINI:
                error = vfs_detach(&ptyfs_vfsops);
                if (error != 0)
                        break;
                break;
        default:
                error = ENOTTY;
                break;
        }

        return (error);
}