/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2017 by Delphix. All rights reserved.
 * Copyright 2023 Oxide Computer Company
 */

/*
 * vnode ops for the devfs
 *
 * For leaf vnode special files (VCHR|VBLK) specfs will always see the VOP
 * first because dv_find always performs leaf vnode substitution, returning
 * a specfs vnode with an s_realvp pointing to the devfs leaf vnode. This
 * means that the only leaf special file VOP operations that devfs will see
 * after VOP_LOOKUP are the ones that specfs forwards.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/t_lock.h>
#include <sys/systm.h>
#include <sys/sysmacros.h>
#include <sys/user.h>
#include <sys/time.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/vfs_opreg.h>
#include <sys/file.h>
#include <sys/fcntl.h>
#include <sys/flock.h>
#include <sys/kmem.h>
#include <sys/uio.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/cred.h>
#include <sys/dirent.h>
#include <sys/pathname.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/policy.h>
#include <sys/modctl.h>
#include <sys/sunndi.h>
#include <fs/fs_subr.h>
#include <sys/fs/dv_node.h>

extern struct vattr     dv_vattr_dir, dv_vattr_file;
extern dev_t rconsdev;

/*
 * Open of devices (leaf nodes) is handled by specfs.
 * There is nothing to do to open a directory
 */
/*ARGSUSED*/
static int
devfs_open(struct vnode **vpp, int flag, struct cred *cred,
    caller_context_t *ct)
{
        struct dv_node  *dv = VTODV(*vpp);

        dcmn_err2(("devfs_open %s\n", dv->dv_name));
        ASSERT((*vpp)->v_type == VDIR);
        return (0);
}

/*
 * Close of devices (leaf nodes) is handled by specfs.
 * There is nothing much to do inorder to close a directory.
 */
/*ARGSUSED1*/
static int
devfs_close(struct vnode *vp, int flag, int count,
    offset_t offset, struct cred *cred, caller_context_t *ct)
{
        struct dv_node  *dv = VTODV(vp);

        dcmn_err2(("devfs_close %s\n", dv->dv_name));
        ASSERT(vp->v_type == VDIR);

        cleanlocks(vp, ttoproc(curthread)->p_pid, 0);
        cleanshares(vp, ttoproc(curthread)->p_pid);
        return (0);
}

/*
 * Read of devices (leaf nodes) is handled by specfs.
 * Read of directories is not supported.
 */
/*ARGSUSED*/
static int
devfs_read(struct vnode *vp, struct uio *uiop, int ioflag, struct cred *cred,
    struct caller_context *ct)
{
        dcmn_err2(("devfs_read %s\n", VTODV(vp)->dv_name));
        ASSERT(vp->v_type == VDIR);
        ASSERT(RW_READ_HELD(&VTODV(vp)->dv_contents));
        return (EISDIR);
}

/*
 * Write of devices (leaf nodes) is handled by specfs.
 * Write of directories is not supported.
 */
/*ARGSUSED*/
static int
devfs_write(struct vnode *vp, struct uio *uiop, int ioflag, struct cred *cred,
    struct caller_context *ct)
{
        dcmn_err2(("devfs_write %s\n", VTODV(vp)->dv_name));
        ASSERT(vp->v_type == VDIR);
        ASSERT(RW_WRITE_HELD(&VTODV(vp)->dv_contents));
        return (EISDIR);
}

/*
 * Ioctls to device (leaf nodes) is handled by specfs.
 * Ioctl to directories is not supported.
 */
/*ARGSUSED*/
static int
devfs_ioctl(struct vnode *vp, int cmd, intptr_t arg, int flag,
    struct cred *cred, int *rvalp, caller_context_t *ct)
{
        dcmn_err2(("devfs_ioctl %s\n", VTODV(vp)->dv_name));
        ASSERT(vp->v_type == VDIR);

        return (ENOTTY);        /* no ioctls supported */
}

/*
 * We can be asked directly about the attributes of directories, or
 * (via sp->s_realvp) about the filesystem attributes of special files.
 *
 * For directories, we just believe the attribute store
 * though we mangle the nodeid, fsid, and rdev to convince userland we
 * really are a different filesystem.
 *
 * For special files, a little more fakery is required.
 *
 * If the attribute store is not there (read only root), we believe our
 * memory based attributes.
 */
static int
devfs_getattr(struct vnode *vp, struct vattr *vap, int flags, struct cred *cr,
    caller_context_t *ct)
{
        struct dv_node  *dv = VTODV(vp);
        int             error = 0;
        uint_t          mask;

        /*
         * Message goes to console only. Otherwise, the message
         * causes devfs_getattr to be invoked again... infinite loop
         */
        dcmn_err2(("?devfs_getattr %s\n", dv->dv_name));
        ASSERT(dv->dv_attr || dv->dv_attrvp);

        if (!(vp->v_type == VDIR || vp->v_type == VCHR || vp->v_type == VBLK)) {
                cmn_err(CE_WARN,        /* panic ? */
                    "?%s: getattr on vnode type %d", dvnm, vp->v_type);
                return (ENOENT);
        }

        rw_enter(&dv->dv_contents, RW_READER);
        if (dv->dv_attr) {
                /*
                 * obtain from the memory version of attribute.
                 * preserve mask for those that optimize.
                 * devfs specific fields are already merged on creation.
                 */
                mask = vap->va_mask;
                *vap = *dv->dv_attr;
                vap->va_mask = mask;
        } else {
                /* obtain from attribute store and merge */
                error = VOP_GETATTR(dv->dv_attrvp, vap, flags, cr, ct);
                dsysdebug(error, ("vop_getattr %s %d\n", dv->dv_name, error));
                dv_vattr_merge(dv, vap);
        }
        rw_exit(&dv->dv_contents);

        /*
         * Restrict the permissions of the node fronting the console
         * to 0600 with root as the owner.  This prevents a non-root
         * user from gaining access to a serial terminal (like /dev/term/a)
         * which is in reality serving as the console device (/dev/console).
         */
        if (vp->v_rdev == rconsdev) {
                mode_t  rconsmask = S_IXUSR|S_IRWXG|S_IRWXO;
                vap->va_mode &= (~rconsmask);
                vap->va_uid = 0;
        }

        return (error);
}

static int devfs_unlocked_access(void *, int, struct cred *);

/*ARGSUSED4*/
static int
devfs_setattr_dir(
        struct dv_node *dv,
        struct vnode *vp,
        struct vattr *vap,
        int flags,
        struct cred *cr)
{
        struct vattr    *map;
        uint_t          mask;
        int             error = 0;
        struct vattr    vattr;

        ASSERT(dv->dv_attr || dv->dv_attrvp);

        ASSERT(vp->v_type == VDIR);
        ASSERT((dv->dv_flags & DV_NO_FSPERM) == 0);

        if (vap->va_mask & AT_NOSET)
                return (EINVAL);

        /* to ensure consistency, single thread setting of attributes */
        rw_enter(&dv->dv_contents, RW_WRITER);

again:  if (dv->dv_attr) {

                error = secpolicy_vnode_setattr(cr, vp, vap,
                    dv->dv_attr, flags, devfs_unlocked_access, dv);

                if (error)
                        goto out;

                /*
                 * Apply changes to the memory based attribute. This code
                 * is modeled after the tmpfs implementation of memory
                 * based vnodes
                 */
                map = dv->dv_attr;
                mask = vap->va_mask;

                /* Change file access modes. */
                if (mask & AT_MODE) {
                        map->va_mode &= S_IFMT;
                        map->va_mode |= vap->va_mode & ~S_IFMT;
                }
                if (mask & AT_UID)
                        map->va_uid = vap->va_uid;
                if (mask & AT_GID)
                        map->va_gid = vap->va_gid;
                if (mask & AT_ATIME)
                        map->va_atime = vap->va_atime;
                if (mask & AT_MTIME)
                        map->va_mtime = vap->va_mtime;

                if (mask & (AT_MODE | AT_UID | AT_GID | AT_MTIME))
                        gethrestime(&map->va_ctime);
        } else {
                /* use the backing attribute store */
                ASSERT(dv->dv_attrvp);

                /*
                 * See if we are changing something we care about
                 * the persistence of - return success if we don't care.
                 */
                if (vap->va_mask & (AT_MODE|AT_UID|AT_GID|AT_ATIME|AT_MTIME)) {
                        /* Set the attributes */
                        error = VOP_SETATTR(dv->dv_attrvp,
                            vap, flags, cr, NULL);
                        dsysdebug(error,
                            ("vop_setattr %s %d\n", dv->dv_name, error));

                        /*
                         * Some file systems may return EROFS for a setattr
                         * on a readonly file system.  In this case we create
                         * our own memory based attribute.
                         */
                        if (error == EROFS) {
                                /*
                                 * obtain attributes from existing file
                                 * that we will modify and switch to memory
                                 * based attribute until attribute store is
                                 * read/write.
                                 */
                                vattr = dv_vattr_dir;
                                if (VOP_GETATTR(dv->dv_attrvp,
                                    &vattr, flags, cr, NULL) == 0) {
                                        dv->dv_attr = kmem_alloc(
                                            sizeof (struct vattr), KM_SLEEP);
                                        *dv->dv_attr = vattr;
                                        dv_vattr_merge(dv, dv->dv_attr);
                                        goto again;
                                }
                        }
                }
        }
out:
        rw_exit(&dv->dv_contents);
        return (error);
}


/*
 * Compare the uid/gid/mode changes requested for a setattr
 * operation with the same details of a node's default minor
 * perm information.  Return 0 if identical.
 */
static int
dv_setattr_cmp(struct vattr *map, mperm_t *mp)
{
        if ((map->va_mode & S_IAMB) != (mp->mp_mode & S_IAMB))
                return (1);
        if (map->va_uid != mp->mp_uid)
                return (1);
        if (map->va_gid != mp->mp_gid)
                return (1);
        return (0);
}


/*ARGSUSED4*/
static int
devfs_setattr(
        struct vnode *vp,
        struct vattr *vap,
        int flags,
        struct cred *cr,
        caller_context_t *ct)
{
        struct dv_node  *dv = VTODV(vp);
        struct dv_node  *ddv;
        struct vnode    *dvp;
        struct vattr    *map;
        uint_t          mask;
        int             error = 0;
        struct vattr    *free_vattr = NULL;
        struct vattr    *vattrp = NULL;
        mperm_t         mp;
        int             persist;

        /*
         * Message goes to console only. Otherwise, the message
         * causes devfs_getattr to be invoked again... infinite loop
         */
        dcmn_err2(("?devfs_setattr %s\n", dv->dv_name));
        ASSERT(dv->dv_attr || dv->dv_attrvp);

        if (!(vp->v_type == VDIR || vp->v_type == VCHR || vp->v_type == VBLK)) {
                cmn_err(CE_WARN,        /* panic ? */
                    "?%s: getattr on vnode type %d", dvnm, vp->v_type);
                return (ENOENT);
        }

        if (vap->va_mask & AT_NOSET)
                return (EINVAL);

        /*
         * If we are changing something we don't care about
         * the persistence of, return success.
         */
        if ((vap->va_mask &
            (AT_MODE|AT_UID|AT_GID|AT_ATIME|AT_MTIME)) == 0)
                return (0);

        /*
         * If driver overrides fs perm, disallow chmod
         * and do not create attribute nodes.
         */
        if (dv->dv_flags & DV_NO_FSPERM) {
                ASSERT(dv->dv_attr);
                if (vap->va_mask & (AT_MODE | AT_UID | AT_GID))
                        return (EPERM);
                if ((vap->va_mask & (AT_ATIME|AT_MTIME)) == 0)
                        return (0);
                rw_enter(&dv->dv_contents, RW_WRITER);
                if (vap->va_mask & AT_ATIME)
                        dv->dv_attr->va_atime = vap->va_atime;
                if (vap->va_mask & AT_MTIME)
                        dv->dv_attr->va_mtime = vap->va_mtime;
                rw_exit(&dv->dv_contents);
                return (0);
        }

        /*
         * Directories are always created but device nodes are
         * only used to persist non-default permissions.
         */
        if (vp->v_type == VDIR) {
                ASSERT(dv->dv_attr || dv->dv_attrvp);
                return (devfs_setattr_dir(dv, vp, vap, flags, cr));
        }

        /*
         * Allocate now before we take any locks
         */
        vattrp = kmem_zalloc(sizeof (*vattrp), KM_SLEEP);

        /* to ensure consistency, single thread setting of attributes */
        rw_enter(&dv->dv_contents, RW_WRITER);

        /*
         * We don't need to create an attribute node
         * to persist access or modification times.
         */
        persist = (vap->va_mask & (AT_MODE | AT_UID | AT_GID));

        /*
         * If persisting something, get the default permissions
         * for this minor to compare against what the attributes
         * are now being set to.  Default ordering is:
         *      - minor_perm match for this minor
         *      - mode supplied by ddi_create_priv_minor_node
         *      - devfs defaults
         */
        if (persist) {
                if (dev_minorperm(dv->dv_devi, dv->dv_name, &mp) != 0) {
                        mp.mp_uid = dv_vattr_file.va_uid;
                        mp.mp_gid = dv_vattr_file.va_gid;
                        mp.mp_mode = dv_vattr_file.va_mode;
                        if (dv->dv_flags & DV_DFLT_MODE) {
                                ASSERT((dv->dv_dflt_mode & ~S_IAMB) == 0);
                                mp.mp_mode &= ~S_IAMB;
                                mp.mp_mode |= dv->dv_dflt_mode;
                                dcmn_err5(("%s: setattr priv default 0%o\n",
                                    dv->dv_name, mp.mp_mode));
                        } else {
                                dcmn_err5(("%s: setattr devfs default 0%o\n",
                                    dv->dv_name, mp.mp_mode));
                        }
                } else {
                        dcmn_err5(("%s: setattr minor perm default 0%o\n",
                            dv->dv_name, mp.mp_mode));
                }
        }

        /*
         * If we don't have a vattr for this node, construct one.
         */
        if (dv->dv_attr) {
                free_vattr = vattrp;
                vattrp = NULL;
        } else {
                ASSERT(dv->dv_attrvp);
                ASSERT(vp->v_type != VDIR);
                *vattrp = dv_vattr_file;
                error = VOP_GETATTR(dv->dv_attrvp, vattrp, 0, cr, ct);
                dsysdebug(error, ("vop_getattr %s %d\n", dv->dv_name, error));
                if (error)
                        goto out;
                dv->dv_attr = vattrp;
                dv_vattr_merge(dv, dv->dv_attr);
                vattrp = NULL;
        }

        error = secpolicy_vnode_setattr(cr, vp, vap, dv->dv_attr,
            flags, devfs_unlocked_access, dv);
        if (error) {
                dsysdebug(error, ("devfs_setattr %s secpolicy error %d\n",
                    dv->dv_name, error));
                goto out;
        }

        /*
         * Apply changes to the memory based attribute. This code
         * is modeled after the tmpfs implementation of memory
         * based vnodes
         */
        map = dv->dv_attr;
        mask = vap->va_mask;

        /* Change file access modes. */
        if (mask & AT_MODE) {
                map->va_mode &= S_IFMT;
                map->va_mode |= vap->va_mode & ~S_IFMT;
        }
        if (mask & AT_UID)
                map->va_uid = vap->va_uid;
        if (mask & AT_GID)
                map->va_gid = vap->va_gid;
        if (mask & AT_ATIME)
                map->va_atime = vap->va_atime;
        if (mask & AT_MTIME)
                map->va_mtime = vap->va_mtime;

        if (mask & (AT_MODE | AT_UID | AT_GID | AT_MTIME)) {
                gethrestime(&map->va_ctime);
        }

        /*
         * A setattr to defaults means we no longer need the
         * shadow node as a persistent store, unless there
         * are ACLs.  Otherwise create a shadow node if one
         * doesn't exist yet.
         */
        if (persist) {
                if ((dv_setattr_cmp(map, &mp) == 0) &&
                    ((dv->dv_flags & DV_ACL) == 0)) {

                        if (dv->dv_attrvp) {
                                ddv = dv->dv_dotdot;
                                ASSERT(ddv->dv_attrvp);
                                error = VOP_REMOVE(ddv->dv_attrvp,
                                    dv->dv_name, cr, ct, 0);
                                dsysdebug(error,
                                    ("vop_remove %s %s %d\n",
                                    ddv->dv_name, dv->dv_name, error));

                                if (error == EROFS)
                                        error = 0;
                                VN_RELE(dv->dv_attrvp);
                                dv->dv_attrvp = NULL;
                        }
                        ASSERT(dv->dv_attr);
                } else {
                        if (mask & AT_MODE)
                                dcmn_err5(("%s persisting mode 0%o\n",
                                    dv->dv_name, vap->va_mode));
                        if (mask & AT_UID)
                                dcmn_err5(("%s persisting uid %d\n",
                                    dv->dv_name, vap->va_uid));
                        if (mask & AT_GID)
                                dcmn_err5(("%s persisting gid %d\n",
                                    dv->dv_name, vap->va_gid));

                        if (dv->dv_attrvp == NULL) {
                                dvp = DVTOV(dv->dv_dotdot);
                                dv_shadow_node(dvp, dv->dv_name, vp,
                                    NULL, NULLVP, cr,
                                    DV_SHADOW_CREATE | DV_SHADOW_WRITE_HELD);
                        }
                        if (dv->dv_attrvp) {
                                /* If map still valid do TIME for free. */
                                if (dv->dv_attr == map) {
                                        mask = map->va_mask;
                                        map->va_mask =
                                            vap->va_mask | AT_ATIME | AT_MTIME;
                                        error = VOP_SETATTR(dv->dv_attrvp, map,
                                            flags, cr, NULL);
                                        map->va_mask = mask;
                                } else {
                                        error = VOP_SETATTR(dv->dv_attrvp,
                                            vap, flags, cr, NULL);
                                }
                                dsysdebug(error, ("vop_setattr %s %d\n",
                                    dv->dv_name, error));
                        }
                        /*
                         * Some file systems may return EROFS for a setattr
                         * on a readonly file system.  In this case save
                         * as our own memory based attribute.
                         * NOTE: ufs is NOT one of these (see ufs_iupdat).
                         */
                        if (dv->dv_attr && dv->dv_attrvp && error == 0) {
                                vattrp = dv->dv_attr;
                                dv->dv_attr = NULL;
                        } else if (error == EROFS)
                                error = 0;
                }
        }

out:
        rw_exit(&dv->dv_contents);

        if (vattrp)
                kmem_free(vattrp, sizeof (*vattrp));
        if (free_vattr)
                kmem_free(free_vattr, sizeof (*free_vattr));
        return (error);
}

static int
devfs_pathconf(vnode_t *vp, int cmd, ulong_t *valp, cred_t *cr,
    caller_context_t *ct)
{
        switch (cmd) {
        case _PC_ACL_ENABLED:
                /*
                 * We rely on the underlying filesystem for ACLs,
                 * so direct the query for ACL support there.
                 * ACL support isn't relative to the file
                 * and we can't guarantee that the dv node
                 * has an attribute node, so any valid
                 * attribute node will suffice.
                 */
                ASSERT(dvroot);
                ASSERT(dvroot->dv_attrvp);
                return (VOP_PATHCONF(dvroot->dv_attrvp, cmd, valp, cr, ct));
                /*NOTREACHED*/
        }

        return (fs_pathconf(vp, cmd, valp, cr, ct));
}

/*
 * Let avp handle security attributes (acl's).
 */
static int
devfs_getsecattr(struct vnode *vp, struct vsecattr *vsap, int flags,
    struct cred *cr, caller_context_t *ct)
{
        dvnode_t *dv = VTODV(vp);
        struct vnode *avp;
        int     error;

        dcmn_err2(("devfs_getsecattr %s\n", dv->dv_name));
        ASSERT(vp->v_type == VDIR || vp->v_type == VCHR || vp->v_type == VBLK);

        rw_enter(&dv->dv_contents, RW_READER);

        avp = dv->dv_attrvp;

        /* fabricate the acl */
        if (avp == NULL) {
                error = fs_fab_acl(vp, vsap, flags, cr, ct);
                rw_exit(&dv->dv_contents);
                return (error);
        }

        error = VOP_GETSECATTR(avp, vsap, flags, cr, ct);
        dsysdebug(error, ("vop_getsecattr %s %d\n", VTODV(vp)->dv_name, error));
        rw_exit(&dv->dv_contents);
        return (error);
}

/*
 * Set security attributes (acl's)
 *
 * Note that the dv_contents lock has already been acquired
 * by the caller's VOP_RWLOCK.
 */
static int
devfs_setsecattr(struct vnode *vp, struct vsecattr *vsap, int flags,
    struct cred *cr, caller_context_t *ct)
{
        dvnode_t *dv = VTODV(vp);
        struct vnode *avp;
        int     error;

        dcmn_err2(("devfs_setsecattr %s\n", dv->dv_name));
        ASSERT(vp->v_type == VDIR || vp->v_type == VCHR || vp->v_type == VBLK);
        ASSERT(RW_LOCK_HELD(&dv->dv_contents));

        /*
         * Not a supported operation on drivers not providing
         * file system based permissions.
         */
        if (dv->dv_flags & DV_NO_FSPERM)
                return (ENOTSUP);

        /*
         * To complete, the setsecattr requires an underlying attribute node.
         */
        if (dv->dv_attrvp == NULL) {
                ASSERT(vp->v_type == VCHR || vp->v_type == VBLK);
                dv_shadow_node(DVTOV(dv->dv_dotdot), dv->dv_name, vp,
                    NULL, NULLVP, cr, DV_SHADOW_CREATE | DV_SHADOW_WRITE_HELD);
        }

        if ((avp = dv->dv_attrvp) == NULL) {
                dcmn_err2(("devfs_setsecattr %s: "
                    "cannot construct attribute node\n", dv->dv_name));
                return (fs_nosys());
        }

        /*
         * The acl(2) system call issues a VOP_RWLOCK before setting an ACL.
         * Since backing file systems expect the lock to be held before seeing
         * a VOP_SETSECATTR ACL, we need to issue the VOP_RWLOCK to the backing
         * store before forwarding the ACL.
         */
        (void) VOP_RWLOCK(avp, V_WRITELOCK_TRUE, NULL);
        error = VOP_SETSECATTR(avp, vsap, flags, cr, ct);
        dsysdebug(error, ("vop_setsecattr %s %d\n", VTODV(vp)->dv_name, error));
        VOP_RWUNLOCK(avp, V_WRITELOCK_TRUE, NULL);

        /*
         * Set DV_ACL if we have a non-trivial set of ACLs.  It is not
         * necessary to hold VOP_RWLOCK since fs_acl_nontrivial only does
         * VOP_GETSECATTR calls.
         */
        if (fs_acl_nontrivial(avp, cr))
                dv->dv_flags |= DV_ACL;
        return (error);
}

/*
 * This function is used for secpolicy_setattr().  It must call an
 * access() like function while it is already holding the
 * dv_contents lock.  We only care about this when dv_attr != NULL;
 * so the unlocked access call only concerns itself with that
 * particular branch of devfs_access().
 */
static int
devfs_unlocked_access(void *vdv, int mode, struct cred *cr)
{
        struct dv_node *dv = vdv;
        int shift = 0;
        uid_t owner = dv->dv_attr->va_uid;

        /* Check access based on owner, group and public permissions. */
        if (crgetuid(cr) != owner) {
                shift += 3;
                if (groupmember(dv->dv_attr->va_gid, cr) == 0)
                        shift += 3;
        }

        return (secpolicy_vnode_access2(cr, DVTOV(dv), owner,
            dv->dv_attr->va_mode << shift, mode));
}

static int
devfs_access(struct vnode *vp, int mode, int flags, struct cred *cr,
    caller_context_t *ct)
{
        struct dv_node  *dv = VTODV(vp);
        int             res;

        dcmn_err2(("devfs_access %s\n", dv->dv_name));
        ASSERT(dv->dv_attr || dv->dv_attrvp);

        /* restrict console access to privileged processes */
        if ((vp->v_rdev == rconsdev) && secpolicy_console(cr) != 0) {
                return (EACCES);
        }

        rw_enter(&dv->dv_contents, RW_READER);
        if (dv->dv_attr && ((dv->dv_flags & DV_ACL) == 0)) {
                res = devfs_unlocked_access(dv, mode, cr);
        } else {
                res = VOP_ACCESS(dv->dv_attrvp, mode, flags, cr, ct);
        }
        rw_exit(&dv->dv_contents);
        return (res);
}

/*
 * Lookup
 *
 * Given the directory vnode and the name of the component, return
 * the corresponding held vnode for that component.
 *
 * Of course in these fictional filesystems, nothing's ever quite
 * -that- simple.
 *
 * devfs name   type            shadow (fs attributes)  type    comments
 * -------------------------------------------------------------------------
 * drv[@addr]   VDIR            drv[@addr]              VDIR    nexus driver
 * drv[@addr]:m VCHR/VBLK       drv[@addr]:m            VREG    leaf driver
 * drv[@addr]   VCHR/VBLK       drv[@addr]:.default     VREG    leaf driver
 * -------------------------------------------------------------------------
 *
 * The following names are reserved for the attribute filesystem (which
 * could easily be another layer on top of this one - we simply need to
 * hold the vnode of the thing we're looking at)
 *
 * attr name    type            shadow (fs attributes)  type    comments
 * -------------------------------------------------------------------------
 * drv[@addr]   VDIR            -                       -       attribute dir
 * minorname    VDIR            -                       -       minorname
 * attribute    VREG            -                       -       attribute
 * -------------------------------------------------------------------------
 *
 * Examples:
 *
 *      devfs:/devices/.../mm@0:zero            VCHR
 *      shadow:/.devices/.../mm@0:zero          VREG, fs attrs
 *      devfs:/devices/.../mm@0:/zero/attr      VREG, driver attribute
 *
 *      devfs:/devices/.../sd@0,0:a             VBLK
 *      shadow:/.devices/.../sd@0,0:a           VREG, fs attrs
 *      devfs:/devices/.../sd@0,0:/a/.type      VREG, "ddi_block:chan"
 *
 *      devfs:/devices/.../mm@0                 VCHR
 *      shadow:/.devices/.../mm@0:.default      VREG, fs attrs
 *      devfs:/devices/.../mm@0:/.default/attr  VREG, driver attribute
 *      devfs:/devices/.../mm@0:/.default/.type VREG, "ddi_pseudo"
 *
 *      devfs:/devices/.../obio                 VDIR
 *      shadow:/devices/.../obio                VDIR, needed for fs attrs.
 *      devfs:/devices/.../obio:/.default/attr  VDIR, driver attribute
 *
 * We also need to be able deal with "old" devices that have gone away,
 * though I think that provided we return them with readdir, they can
 * be removed (i.e. they don't have to respond to lookup, though it might
 * be weird if they didn't ;-)
 *
 * Lookup has side-effects.
 *
 * - It will create directories and fs attribute files in the shadow hierarchy.
 * - It should cause non-SID devices to be probed (ask the parent nexi).
 */
/*ARGSUSED3*/
static int
devfs_lookup(struct vnode *dvp, char *nm, struct vnode **vpp,
    struct pathname *pnp, int flags, struct vnode *rdir, struct cred *cred,
    caller_context_t *ct, int *direntflags, pathname_t *realpnp)
{
        ASSERT(dvp->v_type == VDIR);
        dcmn_err2(("devfs_lookup: %s\n", nm));
        return (dv_find(VTODV(dvp), nm, vpp, pnp, rdir, cred, 0));
}

/*
 * devfs nodes can't really be created directly by userland - however,
 * we do allow creates to find existing nodes:
 *
 * - any create fails if the node doesn't exist - EROFS.
 * - creating an existing directory read-only succeeds, otherwise EISDIR.
 * - exclusive creates fail if the node already exists - EEXIST.
 * - failure to create the snode for an existing device - ENOSYS.
 */
/*ARGSUSED2*/
static int
devfs_create(struct vnode *dvp, char *nm, struct vattr *vap, vcexcl_t excl,
    int mode, struct vnode **vpp, struct cred *cred, int flag,
    caller_context_t *ct, vsecattr_t *vsecp)
{
        int error;
        struct vnode *vp;

        dcmn_err2(("devfs_create %s\n", nm));
        error = dv_find(VTODV(dvp), nm, &vp, NULL, NULLVP, cred, 0);
        if (error == 0) {
                if (excl == EXCL)
                        error = EEXIST;
                else if (vp->v_type == VDIR && (mode & VWRITE))
                        error = EISDIR;
                else
                        error = VOP_ACCESS(vp, mode, 0, cred, ct);

                if (error) {
                        VN_RELE(vp);
                } else
                        *vpp = vp;
        } else if (error == ENOENT)
                error = EROFS;

        return (error);
}

/*
 * If DV_BUILD is set, we call into nexus driver to do a BUS_CONFIG_ALL.
 * Otherwise, simply return cached dv_node's. Hotplug code always call
 * devfs_clean() to invalid the dv_node cache.
 */
/*ARGSUSED5*/
static int
devfs_readdir(struct vnode *dvp, struct uio *uiop, struct cred *cred, int *eofp,
    caller_context_t *ct, int flags)
{
        struct dv_node *ddv, *dv;
        struct dirent64 *de, *bufp;
        offset_t diroff;
        offset_t        soff;
        size_t reclen, movesz;
        int error;
        struct vattr va;
        size_t bufsz;

        ddv = VTODV(dvp);
        dcmn_err2(("devfs_readdir %s: offset %lld len %ld\n",
            ddv->dv_name, uiop->uio_loffset, uiop->uio_iov->iov_len));
        ASSERT(ddv->dv_attr || ddv->dv_attrvp);
        ASSERT(RW_READ_HELD(&ddv->dv_contents));

        if (uiop->uio_loffset >= MAXOFF_T) {
                if (eofp)
                        *eofp = 1;
                return (0);
        }

        if (uiop->uio_iovcnt != 1)
                return (EINVAL);

        if (dvp->v_type != VDIR)
                return (ENOTDIR);

        /* Load the initial contents */
        if (ddv->dv_flags & DV_BUILD) {
                if (!rw_tryupgrade(&ddv->dv_contents)) {
                        rw_exit(&ddv->dv_contents);
                        rw_enter(&ddv->dv_contents, RW_WRITER);
                }

                /* recheck and fill */
                if (ddv->dv_flags & DV_BUILD)
                        dv_filldir(ddv);

                rw_downgrade(&ddv->dv_contents);
        }

        /*
         * Even if the dv node was not stale at entry to this function, it may
         * be stale now if another process got in between the rw_exit/rw_enter
         * calls above and unlinked it.
         */
        if (DV_STALE(ddv))
                return (ESTALE);

        soff = uiop->uio_loffset;
        bufsz = uiop->uio_iov->iov_len;
        de = bufp = kmem_alloc(bufsz, KM_SLEEP);
        movesz = 0;
        dv = (struct dv_node *)-1;

        /*
         * Move as many entries into the uio structure as it will take.
         * Special case "." and "..".
         */
        diroff = 0;
        if (soff == 0) {                                /* . */
                reclen = DIRENT64_RECLEN(strlen("."));
                if ((movesz + reclen) > bufsz)
                        goto full;
                de->d_ino = (ino64_t)ddv->dv_ino;
                de->d_off = (off64_t)diroff + 1;
                de->d_reclen = (ushort_t)reclen;

                /* use strncpy(9f) to zero out uninitialized bytes */

                (void) strncpy(de->d_name, ".", DIRENT64_NAMELEN(reclen));
                movesz += reclen;
                de = (dirent64_t *)(intptr_t)((char *)de + reclen);
                dcmn_err3(("devfs_readdir: A: diroff %lld, soff %lld: '%s' "
                    "reclen %lu\n", diroff, soff, ".", reclen));
        }

        diroff++;
        if (soff <= 1) {                                /* .. */
                reclen = DIRENT64_RECLEN(strlen(".."));
                if ((movesz + reclen) > bufsz)
                        goto full;
                de->d_ino = (ino64_t)ddv->dv_dotdot->dv_ino;
                de->d_off = (off64_t)diroff + 1;
                de->d_reclen = (ushort_t)reclen;

                /* use strncpy(9f) to zero out uninitialized bytes */

                (void) strncpy(de->d_name, "..", DIRENT64_NAMELEN(reclen));
                movesz += reclen;
                de = (dirent64_t *)(intptr_t)((char *)de + reclen);
                dcmn_err3(("devfs_readdir: B: diroff %lld, soff %lld: '%s' "
                    "reclen %lu\n", diroff, soff, "..", reclen));
        }

        diroff++;
        for (dv = DV_FIRST_ENTRY(ddv); dv;
            dv = DV_NEXT_ENTRY(ddv, dv), diroff++) {
                /* skip entries until at correct directory offset */
                if (diroff < soff)
                        continue;

                /*
                 * hidden nodes are skipped (but they still occupy a
                 * directory offset).
                 */
                if (dv->dv_devi && ndi_dev_is_hidden_node(dv->dv_devi))
                        continue;

                /*
                 * DDM_INTERNAL_PATH minor nodes are skipped for readdirs
                 * outside the kernel (but they still occupy a directory
                 * offset).
                 */
                if ((dv->dv_flags & DV_INTERNAL) && (cred != kcred))
                        continue;

                reclen = DIRENT64_RECLEN(strlen(dv->dv_name));
                if ((movesz + reclen) > bufsz) {
                        dcmn_err3(("devfs_readdir: C: diroff "
                            "%lld, soff %lld: '%s' reclen %lu\n",
                            diroff, soff, dv->dv_name, reclen));
                        goto full;
                }
                de->d_ino = (ino64_t)dv->dv_ino;
                de->d_off = (off64_t)diroff + 1;
                de->d_reclen = (ushort_t)reclen;

                /* use strncpy(9f) to zero out uninitialized bytes */

                ASSERT(strlen(dv->dv_name) + 1 <=
                    DIRENT64_NAMELEN(reclen));
                (void) strncpy(de->d_name, dv->dv_name,
                    DIRENT64_NAMELEN(reclen));

                movesz += reclen;
                de = (dirent64_t *)(intptr_t)((char *)de + reclen);
                dcmn_err4(("devfs_readdir: D: diroff "
                    "%lld, soff %lld: '%s' reclen %lu\n", diroff, soff,
                    dv->dv_name, reclen));
        }

        /* the buffer is full, or we exhausted everything */
full:   dcmn_err3(("devfs_readdir: moving %lu bytes: "
            "diroff %lld, soff %lld, dv %p\n",
            movesz, diroff, soff, (void *)dv));

        if ((movesz == 0) && dv)
                error = EINVAL;         /* cannot be represented */
        else {
                error = uiomove(bufp, movesz, UIO_READ, uiop);
                if (error == 0) {
                        if (eofp)
                                *eofp = dv ? 0 : 1;
                        uiop->uio_loffset = diroff;
                }

                va.va_mask = AT_ATIME;
                gethrestime(&va.va_atime);
                rw_exit(&ddv->dv_contents);
                (void) devfs_setattr(dvp, &va, 0, cred, ct);
                rw_enter(&ddv->dv_contents, RW_READER);
        }

        kmem_free(bufp, bufsz);
        return (error);
}

/*ARGSUSED*/
static int
devfs_fsync(struct vnode *vp, int syncflag, struct cred *cred,
    caller_context_t *ct)
{
        /*
         * Message goes to console only. Otherwise, the message
         * causes devfs_fsync to be invoked again... infinite loop
         */
        dcmn_err2(("devfs_fsync %s\n", VTODV(vp)->dv_name));
        return (0);
}

/*
 * Normally, we leave the dv_node here at count of 0.
 * The node will be destroyed when dv_cleandir() is called.
 *
 * Stale dv_node's are already unlinked from the fs tree,
 * so dv_cleandir() won't find them. We destroy such nodes
 * immediately.
 */
/*ARGSUSED1*/
static void
devfs_inactive(struct vnode *vp, struct cred *cred, caller_context_t *ct)
{
        int destroy;
        struct dv_node *dv = VTODV(vp);

        dcmn_err2(("devfs_inactive: %s\n", dv->dv_name));
        mutex_enter(&vp->v_lock);
        ASSERT(vp->v_count >= 1);
        VN_RELE_LOCKED(vp);
        destroy = (DV_STALE(dv) && vp->v_count == 0);
        mutex_exit(&vp->v_lock);

        /* stale nodes cannot be rediscovered, destroy it here */
        if (destroy)
                dv_destroy(dv, 0);
}

/*
 * XXX Why do we need this?  NFS mounted /dev directories?
 * XXX Talk to peter staubach about this.
 */
/*ARGSUSED2*/
static int
devfs_fid(struct vnode *vp, struct fid *fidp, caller_context_t *ct)
{
        struct dv_node  *dv = VTODV(vp);
        struct dv_fid   *dv_fid;

        if (fidp->fid_len < (sizeof (struct dv_fid) - sizeof (ushort_t))) {
                fidp->fid_len = sizeof (struct dv_fid) - sizeof (ushort_t);
                return (ENOSPC);
        }

        dv_fid = (struct dv_fid *)fidp;
        bzero(dv_fid, sizeof (struct dv_fid));
        dv_fid->dvfid_len = (int)sizeof (struct dv_fid) - sizeof (ushort_t);
        dv_fid->dvfid_ino = dv->dv_ino;
        /* dv_fid->dvfid_gen = dv->tn_gen; XXX ? */

        return (0);
}

/*
 * This pair of routines bracket all VOP_READ, VOP_WRITE
 * and VOP_READDIR requests.  The contents lock stops things
 * moving around while we're looking at them.
 *
 * Also used by file and record locking.
 */
/*ARGSUSED2*/
static int
devfs_rwlock(struct vnode *vp, int write_flag, caller_context_t *ct)
{
        dcmn_err2(("devfs_rwlock %s\n", VTODV(vp)->dv_name));
        rw_enter(&VTODV(vp)->dv_contents, write_flag ? RW_WRITER : RW_READER);
        return (write_flag);
}

/*ARGSUSED1*/
static void
devfs_rwunlock(struct vnode *vp, int write_flag, caller_context_t *ct)
{
        dcmn_err2(("devfs_rwunlock %s\n", VTODV(vp)->dv_name));
        rw_exit(&VTODV(vp)->dv_contents);
}

/*
 * XXX  Should probably do a better job of computing the maximum
 *      offset available in the directory.
 */
/*ARGSUSED1*/
static int
devfs_seek(struct vnode *vp, offset_t ooff, offset_t *noffp,
    caller_context_t *ct)
{
        ASSERT(vp->v_type == VDIR);
        dcmn_err2(("devfs_seek %s\n", VTODV(vp)->dv_name));
        return (*noffp < 0 ? EINVAL : 0);
}

vnodeops_t *dv_vnodeops;

const fs_operation_def_t dv_vnodeops_template[] = {
        VOPNAME_OPEN,           { .vop_open = devfs_open },
        VOPNAME_CLOSE,          { .vop_close = devfs_close },
        VOPNAME_READ,           { .vop_read = devfs_read },
        VOPNAME_WRITE,          { .vop_write = devfs_write },
        VOPNAME_IOCTL,          { .vop_ioctl = devfs_ioctl },
        VOPNAME_GETATTR,        { .vop_getattr = devfs_getattr },
        VOPNAME_SETATTR,        { .vop_setattr = devfs_setattr },
        VOPNAME_ACCESS,         { .vop_access = devfs_access },
        VOPNAME_LOOKUP,         { .vop_lookup = devfs_lookup },
        VOPNAME_CREATE,         { .vop_create = devfs_create },
        VOPNAME_READDIR,        { .vop_readdir = devfs_readdir },
        VOPNAME_FSYNC,          { .vop_fsync = devfs_fsync },
        VOPNAME_INACTIVE,       { .vop_inactive = devfs_inactive },
        VOPNAME_FID,            { .vop_fid = devfs_fid },
        VOPNAME_RWLOCK,         { .vop_rwlock = devfs_rwlock },
        VOPNAME_RWUNLOCK,       { .vop_rwunlock = devfs_rwunlock },
        VOPNAME_SEEK,           { .vop_seek = devfs_seek },
        VOPNAME_PATHCONF,       { .vop_pathconf = devfs_pathconf },
        VOPNAME_DISPOSE,        { .error = fs_error },
        VOPNAME_SETSECATTR,     { .vop_setsecattr = devfs_setsecattr },
        VOPNAME_GETSECATTR,     { .vop_getsecattr = devfs_getsecattr },
        NULL,                   NULL
};