xref: /xnu-11417.140.69/bsd/vfs/vfs_xattr.c (revision 43a90889846e00bfb5cf1d255cdc0a701a1e05a4)

/*
 * Copyright (c) 2004-2012 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#include <sys/param.h>

#include <sys/fcntl.h>
#include <sys/file_internal.h>
#include <sys/fsevents.h>
#include <sys/kernel.h>
#include <sys/kauth.h>
#include <sys/mount_internal.h>
#include <sys/namei.h>
#include <sys/proc_internal.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <sys/utfconv.h>
#include <sys/vnode.h>
#include <sys/vnode_internal.h>
#include <sys/xattr.h>

#include <kern/kalloc.h>
#include <kern/kern_types.h>
#include <kern/host.h>
#include <kern/ipc_misc.h>

#include <mach/doubleagent_mig_server.h>
#include <mach/doubleagent_types.h>
#include <mach/host_priv.h>
#include <mach/host_special_ports.h>

#include <libkern/OSByteOrder.h>
#include <vm/vm_kern.h>
#include <vm/vm_protos.h>       /* XXX for ipc_port_release_send() */

#if CONFIG_MACF
#include <security/mac_framework.h>
#endif


#if NAMEDSTREAMS

static int shadow_sequence;

/*
 * We use %p to prevent loss of precision for pointers on varying architectures.
 */

#define SHADOW_NAME_FMT         ".vfs_rsrc_stream_%p%08x%p"
#define SHADOW_DIR_FMT          ".vfs_rsrc_streams_%p%x"
#define SHADOW_DIR_CONTAINER    "/private/var/run"

#define MAKE_SHADOW_NAME(VP, NAME)  \
	snprintf((NAME), sizeof((NAME)), (SHADOW_NAME_FMT), \
	                ((void*)(VM_KERNEL_ADDRPERM(VP))), \
	                (VP)->v_id, \
	                ((void*)(VM_KERNEL_ADDRPERM((VP)->v_data))))

/* The full path to the shadow directory */
#define MAKE_SHADOW_DIRNAME(VP, NAME)   \
	snprintf((NAME), sizeof((NAME)), (SHADOW_DIR_CONTAINER "/" SHADOW_DIR_FMT), \
	                ((void*)(VM_KERNEL_ADDRPERM(VP))), shadow_sequence)

/* The shadow directory as a 'leaf' entry */
#define MAKE_SHADOW_DIR_LEAF(VP, NAME)  \
	snprintf((NAME), sizeof((NAME)), (SHADOW_DIR_FMT), \
	                ((void*)(VM_KERNEL_ADDRPERM(VP))), shadow_sequence)

static int  default_getnamedstream(vnode_t vp, vnode_t *svpp, const char *name, enum nsoperation op, vfs_context_t context);

static int  default_makenamedstream(vnode_t vp, vnode_t *svpp, const char *name, vfs_context_t context);

static int  default_removenamedstream(vnode_t vp, const char *name, vfs_context_t context);

static int  getshadowfile(vnode_t vp, vnode_t *svpp, int makestream, size_t *rsrcsize, int *creator, vfs_context_t context);

static int  get_shadow_dir(vnode_t *sdvpp);

#endif /* NAMEDSTREAMS */

/*
 * Default xattr support routines.
 */

static int default_getxattr(vnode_t vp, const char *name, uio_t uio, size_t *size, int options,
    vfs_context_t context);
static int default_setxattr(vnode_t vp, const char *name, uio_t uio, int options,
    vfs_context_t context);
static int default_listxattr(vnode_t vp, uio_t uio, size_t *size, int options,
    vfs_context_t context);
static int default_removexattr(vnode_t vp, const char *name, int options,
    vfs_context_t context);

/*
 *  Retrieve the data of an extended attribute.
 */
int
vn_getxattr(vnode_t vp, const char *name, uio_t uio, size_t *size,
    int options, vfs_context_t context)
{
	int error;

	if (!XATTR_VNODE_SUPPORTED(vp)) {
		return EPERM;
	}
#if NAMEDSTREAMS
	/* getxattr calls are not allowed for streams. */
	if (vp->v_flag & VISNAMEDSTREAM) {
		error = EPERM;
		goto out;
	}
#endif
	/*
	 * Non-kernel request need extra checks performed.
	 *
	 * The XATTR_NOSECURITY flag implies a kernel request.
	 */
	if (!(options & XATTR_NOSECURITY)) {
#if CONFIG_MACF
		error = mac_vnode_check_getextattr(context, vp, name, uio);
		if (error) {
			goto out;
		}
#endif /* MAC */
		if ((error = xattr_validatename(name))) {
			goto out;
		}
		if ((error = vnode_authorize(vp, NULL, KAUTH_VNODE_READ_EXTATTRIBUTES, context))) {
			goto out;
		}
	}

	/* The offset can only be non-zero for resource forks. */
	if (uio_offset(uio) != 0 &&
	    strncmp(name, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME)) != 0) {
		error = EINVAL;
		goto out;
	}

	error = VNOP_GETXATTR(vp, name, uio, size, options, context);
	if (error == ENOTSUP && !(options & XATTR_NODEFAULT)) {
		/*
		 * A filesystem may keep some EAs natively and return ENOTSUP for others.
		 */
		error = default_getxattr(vp, name, uio, size, options, context);
	}
out:
	return error;
}

/*
 * Set the data of an extended attribute.
 */
int
vn_setxattr(vnode_t vp, const char *name, uio_t uio, int options, vfs_context_t context)
{
	int error;

	if (!XATTR_VNODE_SUPPORTED(vp)) {
		return EPERM;
	}
#if NAMEDSTREAMS
	/* setxattr calls are not allowed for streams. */
	if (vp->v_flag & VISNAMEDSTREAM) {
		error = EPERM;
		goto out;
	}
#endif
	if ((options & (XATTR_REPLACE | XATTR_CREATE)) == (XATTR_REPLACE | XATTR_CREATE)) {
		return EINVAL;
	}
	if ((error = xattr_validatename(name))) {
		return error;
	}
	if (!(options & XATTR_NOSECURITY)) {
#if CONFIG_MACF
		error = mac_vnode_check_setextattr(context, vp, name, uio);
		if (error) {
			goto out;
		}
#endif /* MAC */
		error = vnode_authorize(vp, NULL, KAUTH_VNODE_WRITE_EXTATTRIBUTES, context);
		if (error) {
			goto out;
		}
	}
	/* The offset can only be non-zero for resource forks. */
	if (uio_offset(uio) != 0 &&
	    strncmp(name, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME)) != 0) {
		error = EINVAL;
		goto out;
	}

	error = VNOP_SETXATTR(vp, name, uio, options, context);
#ifdef DUAL_EAS
	/*
	 * An EJUSTRETURN is from a filesystem which keeps this xattr
	 * natively as well as in a dot-underscore file.  In this case the
	 * EJUSTRETURN means the filesytem has done nothing, but identifies the
	 * EA as one which may be represented natively and/or in a DU, and
	 * since XATTR_CREATE or XATTR_REPLACE was specified, only up here in
	 * in vn_setxattr can we do the getxattrs needed to ascertain whether
	 * the XATTR_{CREATE,REPLACE} should yield an error.
	 */
	if (error == EJUSTRETURN) {
		int native = 0, dufile = 0;
		size_t sz;      /* not used */

		native = VNOP_GETXATTR(vp, name, NULL, &sz, 0, context) ? 0 : 1;
		dufile = default_getxattr(vp, name, NULL, &sz, 0, context) ? 0 : 1;
		if (options & XATTR_CREATE && (native || dufile)) {
			error = EEXIST;
			goto out;
		}
		if (options & XATTR_REPLACE && !(native || dufile)) {
			error = ENOATTR;
			goto out;
		}
		/*
		 * Having determined no CREATE/REPLACE error should result, we
		 * zero those bits, so both backing stores get written to.
		 */
		options &= ~(XATTR_CREATE | XATTR_REPLACE);
		error = VNOP_SETXATTR(vp, name, uio, options, context);
		/* the mainline path here is to have error==ENOTSUP ... */
	}
#endif /* DUAL_EAS */
	if (error == ENOTSUP && !(options & XATTR_NODEFAULT)) {
		/*
		 * A filesystem may keep some EAs natively and return ENOTSUP for others.
		 */
		error = default_setxattr(vp, name, uio, options, context);
	}
#if CONFIG_MACF
	if ((error == 0) && !(options & XATTR_NOSECURITY)) {
		mac_vnode_notify_setextattr(context, vp, name, uio);
		if (vfs_flags(vnode_mount(vp)) & MNT_MULTILABEL) {
			mac_vnode_label_update_extattr(vnode_mount(vp), vp, name);
		}
	}
#endif
out:
	return error;
}

/*
 * Remove an extended attribute.
 */
int
vn_removexattr(vnode_t vp, const char * name, int options, vfs_context_t context)
{
	int error;

	if (!XATTR_VNODE_SUPPORTED(vp)) {
		return EPERM;
	}
#if NAMEDSTREAMS
	/* removexattr calls are not allowed for streams. */
	if (vp->v_flag & VISNAMEDSTREAM) {
		error = EPERM;
		goto out;
	}
#endif
	if ((error = xattr_validatename(name))) {
		return error;
	}
	if (!(options & XATTR_NOSECURITY)) {
#if CONFIG_MACF
		error = mac_vnode_check_deleteextattr(context, vp, name);
		if (error) {
			goto out;
		}
#endif /* MAC */
		error = vnode_authorize(vp, NULL, KAUTH_VNODE_WRITE_EXTATTRIBUTES, context);
		if (error) {
			goto out;
		}
	}
	error = VNOP_REMOVEXATTR(vp, name, options, context);
	if (error == ENOTSUP && !(options & XATTR_NODEFAULT)) {
		/*
		 * A filesystem may keep some EAs natively and return ENOTSUP for others.
		 */
		error = default_removexattr(vp, name, options, context);
#ifdef DUAL_EAS
	} else if (error == EJUSTRETURN) {
		/*
		 * EJUSTRETURN is from a filesystem which keeps this xattr natively as well
		 * as in a dot-underscore file.  EJUSTRETURN means the filesytem did remove
		 * a native xattr, so failure to find it in a DU file during
		 * default_removexattr should not be considered an error.
		 */
		error = default_removexattr(vp, name, options, context);
		if (error == ENOATTR) {
			error = 0;
		}
#endif /* DUAL_EAS */
	}
#if CONFIG_MACF
	if ((error == 0) && !(options & XATTR_NOSECURITY)) {
		mac_vnode_notify_deleteextattr(context, vp, name);
		if (vfs_flags(vnode_mount(vp)) & MNT_MULTILABEL) {
			mac_vnode_label_update_extattr(vnode_mount(vp), vp, name);
		}
	}
#endif
out:
	return error;
}

/*
 * Retrieve the list of extended attribute names.
 */
int
vn_listxattr(vnode_t vp, uio_t uio, size_t *size, int options, vfs_context_t context)
{
	int error;

	if (!XATTR_VNODE_SUPPORTED(vp)) {
		return EPERM;
	}
#if NAMEDSTREAMS
	/* listxattr calls are not allowed for streams. */
	if (vp->v_flag & VISNAMEDSTREAM) {
		return EPERM;
	}
#endif

	if (!(options & XATTR_NOSECURITY)) {
#if CONFIG_MACF
		error = mac_vnode_check_listextattr(context, vp);
		if (error) {
			goto out;
		}
#endif /* MAC */

		error = vnode_authorize(vp, NULL, KAUTH_VNODE_READ_EXTATTRIBUTES, context);
		if (error) {
			goto out;
		}
	}

	error = VNOP_LISTXATTR(vp, uio, size, options, context);
	if (error == ENOTSUP && !(options & XATTR_NODEFAULT)) {
		/*
		 * A filesystem may keep some but not all EAs natively, in which case
		 * the native EA names will have been uiomove-d out (or *size updated)
		 * and the default_listxattr here will finish the job.
		 */
		error = default_listxattr(vp, uio, size, options, context);
	}
out:
	return error;
}

int
xattr_validatename(const char *name)
{
	size_t namelen;

	if (name == NULL || name[0] == '\0') {
		return EINVAL;
	}
	namelen = strlen(name);

	if (utf8_validatestr((const unsigned char *)name, namelen) != 0) {
		return EINVAL;
	}

	return 0;
}


/*
 * Determine whether an EA is a protected system attribute.
 */
int
xattr_protected(const char *attrname)
{
	return !strncmp(attrname, "com.apple.system.", 17);
}


static void
vnode_setasnamedstream_internal(vnode_t vp, vnode_t svp)
{
	uint32_t streamflags = VISNAMEDSTREAM;

	if ((vp->v_mount->mnt_kern_flag & MNTK_NAMED_STREAMS) == 0) {
		streamflags |= VISSHADOW;
	}

	/* Tag the vnode. */
	vnode_lock_spin(svp);
	svp->v_flag |= streamflags;
	vnode_unlock(svp);

	/* Tag the parent so we know to flush credentials for streams on setattr */
	vnode_lock_spin(vp);
	vp->v_lflag |= VL_HASSTREAMS;
	vnode_unlock(vp);

	/* Make the file it's parent.
	 * Note:  This parent link helps us distinguish vnodes for
	 * shadow stream files from vnodes for resource fork on file
	 * systems that support namedstream natively (both have
	 * VISNAMEDSTREAM set) by allowing access to mount structure
	 * for checking MNTK_NAMED_STREAMS bit at many places in the
	 * code.
	 */
	vnode_update_identity(svp, vp, NULL, 0, 0, (VNODE_UPDATE_NAMEDSTREAM_PARENT | VNODE_UPDATE_FORCE_PARENT_REF));

	if (vnode_isdyldsharedcache(vp)) {
		vnode_lock_spin(svp);
		svp->v_flag |= VSHARED_DYLD;
		vnode_unlock(svp);
	}

	return;
}

errno_t
vnode_setasnamedstream(vnode_t vp, vnode_t svp)
{
	if ((vp->v_mount->mnt_kern_flag & MNTK_NAMED_STREAMS) == 0) {
		return EINVAL;
	}

	vnode_setasnamedstream_internal(vp, svp);
	return 0;
}

#if NAMEDSTREAMS

/*
 * Obtain a named stream from vnode vp.
 */
errno_t
vnode_getnamedstream(vnode_t vp, vnode_t *svpp, const char *name, enum nsoperation op, int flags, vfs_context_t context)
{
	int error;

	if (vp->v_mount->mnt_kern_flag & MNTK_NAMED_STREAMS) {
		error = VNOP_GETNAMEDSTREAM(vp, svpp, name, op, flags, context);
	} else {
		if (flags) {
			error = ENOTSUP;
		} else {
			error = default_getnamedstream(vp, svpp, name, op, context);
		}
	}

	if (error == 0) {
		vnode_setasnamedstream_internal(vp, *svpp);
	}

	return error;
}

/*
 * Make a named stream for vnode vp.
 */
errno_t
vnode_makenamedstream(vnode_t vp, vnode_t *svpp, const char *name, int flags, vfs_context_t context)
{
	int error;

	if (vp->v_mount->mnt_kern_flag & MNTK_NAMED_STREAMS) {
		error = VNOP_MAKENAMEDSTREAM(vp, svpp, name, flags, context);
	} else {
		error = default_makenamedstream(vp, svpp, name, context);
	}

	if (error == 0) {
		vnode_setasnamedstream_internal(vp, *svpp);
	}

	return error;
}

/*
 * Remove a named stream from vnode vp.
 */
errno_t
vnode_removenamedstream(vnode_t vp, vnode_t svp, const char *name, int flags, vfs_context_t context)
{
	int error;

	if (vp->v_mount->mnt_kern_flag & MNTK_NAMED_STREAMS) {
		error = VNOP_REMOVENAMEDSTREAM(vp, svp, name, flags, context);
	} else {
		error = default_removenamedstream(vp, name, context);
	}

	return error;
}

#define NS_IOBUFSIZE  (128 * 1024)

/*
 * Release a named stream shadow file.
 *
 * Note: This function is called from two places where we do not need
 * to check if the vnode has any references held before deleting the
 * shadow file.  Once from vclean() when the vnode is being reclaimed
 * and we do not hold any references on the vnode.  Second time from
 * default_getnamedstream() when we get an error during shadow stream
 * file initialization so that other processes who are waiting for the
 * shadow stream file initialization by the creator will get opportunity
 * to create and initialize the file again.
 */
errno_t
vnode_relenamedstream(vnode_t vp, vnode_t svp)
{
	vnode_t dvp;
	struct componentname cn;
	char tmpname[80];
	errno_t err;

	/*
	 * We need to use the kernel context here.  If we used the supplied
	 * VFS context we have no clue whether or not it originated from userland
	 * where it could be subject to a chroot jail.  We need to ensure that all
	 * filesystem access to shadow files is done on the same FS regardless of
	 * userland process restrictions.
	 */
	vfs_context_t kernelctx = vfs_context_kernel();

	cache_purge(svp);

	vnode_lock(svp);
	MAKE_SHADOW_NAME(vp, tmpname);
	vnode_unlock(svp);

	cn.cn_nameiop = DELETE;
	cn.cn_flags = ISLASTCN;
	cn.cn_context = kernelctx;
	cn.cn_pnbuf = tmpname;
	cn.cn_pnlen = sizeof(tmpname);
	cn.cn_nameptr = cn.cn_pnbuf;
	cn.cn_namelen = (int)strlen(tmpname);

	/*
	 * Obtain the vnode for the shadow files directory.  Make sure to
	 * use the kernel ctx as described above.
	 */
	err = get_shadow_dir(&dvp);
	if (err != 0) {
		return err;
	}

	(void) VNOP_REMOVE(dvp, svp, &cn, 0, kernelctx);
	vnode_put(dvp);

	return 0;
}

/*
 * Flush a named stream shadow file.
 *
 * 'vp' represents the AppleDouble file.
 * 'svp' represents the shadow file.
 */
errno_t
vnode_flushnamedstream(vnode_t vp, vnode_t svp, vfs_context_t context)
{
	struct vnode_attr va;
	uio_t auio = NULL;
	caddr_t  bufptr = NULL;
	size_t  bufsize = 0;
	size_t  offset;
	size_t  iosize;
	size_t datasize;
	int error;
	/*
	 * The kernel context must be used for all I/O to the shadow file
	 * and its namespace operations
	 */
	vfs_context_t kernelctx = vfs_context_kernel();

	/* The supplied context is used for access to the AD file itself */

	VATTR_INIT(&va);
	VATTR_WANTED(&va, va_data_size);
	if (VNOP_GETATTR(svp, &va, context) != 0 ||
	    !VATTR_IS_SUPPORTED(&va, va_data_size)) {
		return 0;
	}
	if (va.va_data_size > UINT32_MAX) {
		return EINVAL;
	}
	datasize = (size_t)va.va_data_size;
	if (datasize == 0) {
		(void) default_removexattr(vp, XATTR_RESOURCEFORK_NAME, 0, context);
		return 0;
	}

	iosize = bufsize = MIN(datasize, NS_IOBUFSIZE);
	bufptr = kalloc_data(bufsize, Z_WAITOK);
	if (bufptr == NULL) {
		return ENOMEM;
	}
	auio = uio_create(1, 0, UIO_SYSSPACE, UIO_READ);
	offset = 0;

	/*
	 * Copy the shadow stream file data into the resource fork.
	 */
	error = VNOP_OPEN(svp, 0, kernelctx);
	if (error) {
		printf("vnode_flushnamedstream: err %d opening file\n", error);
		goto out;
	}
	while (offset < datasize) {
		iosize = MIN(datasize - offset, iosize);

		uio_reset(auio, offset, UIO_SYSSPACE, UIO_READ);
		uio_addiov(auio, (uintptr_t)bufptr, iosize);
		error = VNOP_READ(svp, auio, 0, kernelctx);
		if (error) {
			break;
		}
		/* Since there's no truncate xattr we must remove the resource fork. */
		if (offset == 0) {
			error = default_removexattr(vp, XATTR_RESOURCEFORK_NAME, 0, context);
			if ((error != 0) && (error != ENOATTR)) {
				break;
			}
		}
		uio_reset(auio, offset, UIO_SYSSPACE, UIO_WRITE);
		uio_addiov(auio, (uintptr_t)bufptr, iosize);
		error = vn_setxattr(vp, XATTR_RESOURCEFORK_NAME, auio, XATTR_NOSECURITY, context);
		if (error) {
			break;
		}
		offset += iosize;
	}

	/* close shadowfile */
	(void) VNOP_CLOSE(svp, 0, kernelctx);
out:
	kfree_data(bufptr, bufsize);
	if (auio) {
		uio_free(auio);
	}
	return error;
}


/*
 * Verify that the vnode 'vp' is a vnode that lives in the shadow
 * directory.  We can't just query the parent pointer directly since
 * the shadowfile is hooked up to the actual file it's a stream for.
 */
errno_t
vnode_verifynamedstream(vnode_t vp)
{
	int error;
	struct vnode *shadow_dvp = NULL;
	struct vnode *shadowfile = NULL;
	struct componentname cn;

	/*
	 * We need to use the kernel context here.  If we used the supplied
	 * VFS context we have no clue whether or not it originated from userland
	 * where it could be subject to a chroot jail.  We need to ensure that all
	 * filesystem access to shadow files is done on the same FS regardless of
	 * userland process restrictions.
	 */
	vfs_context_t kernelctx = vfs_context_kernel();
	char tmpname[80];


	/* Get the shadow directory vnode */
	error = get_shadow_dir(&shadow_dvp);
	if (error) {
		return error;
	}

	/* Re-generate the shadow name in the buffer */
	MAKE_SHADOW_NAME(vp, tmpname);

	/* Look up item in shadow dir */
	bzero(&cn, sizeof(cn));
	cn.cn_nameiop = LOOKUP;
	cn.cn_flags = ISLASTCN | CN_ALLOWRSRCFORK;
	cn.cn_context = kernelctx;
	cn.cn_pnbuf = tmpname;
	cn.cn_pnlen = sizeof(tmpname);
	cn.cn_nameptr = cn.cn_pnbuf;
	cn.cn_namelen = (int)strlen(tmpname);

	if (VNOP_LOOKUP(shadow_dvp, &shadowfile, &cn, kernelctx) == 0) {
		/* is the pointer the same? */
		if (shadowfile == vp) {
			error = 0;
		} else {
			error = EPERM;
		}
		/* drop the iocount acquired */
		vnode_put(shadowfile);
	}

	/* Drop iocount on shadow dir */
	vnode_put(shadow_dvp);
	return error;
}

/*
 * Access or create the shadow file as needed.
 *
 * 'makestream' with non-zero value means that we need to guarantee we were the
 * creator of the shadow file.
 *
 * 'context' is the user supplied context for the original VFS operation that
 * caused us to need a shadow file.
 *
 * int pointed to by 'creator' is nonzero if we created the shadowfile.
 */
static int
getshadowfile(vnode_t vp, vnode_t *svpp, int makestream, size_t *rsrcsize,
    int *creator, vfs_context_t context)
{
	vnode_t  dvp = NULLVP;
	vnode_t  svp = NULLVP;
	struct componentname cn;
	struct vnode_attr va;
	char tmpname[80];
	size_t datasize = 0;
	int  error = 0;
	int retries = 0;
	vfs_context_t kernelctx = vfs_context_kernel();

retry_create:
	*creator = 0;
	/* Establish a unique file name. */
	MAKE_SHADOW_NAME(vp, tmpname);
	bzero(&cn, sizeof(cn));
	cn.cn_nameiop = LOOKUP;
	cn.cn_flags = ISLASTCN;
	cn.cn_context = context;
	cn.cn_pnbuf = tmpname;
	cn.cn_pnlen = sizeof(tmpname);
	cn.cn_nameptr = cn.cn_pnbuf;
	cn.cn_namelen = (int)strlen(tmpname);

	/* Pick up uid, gid, mode and date from original file. */
	VATTR_INIT(&va);
	VATTR_WANTED(&va, va_uid);
	VATTR_WANTED(&va, va_gid);
	VATTR_WANTED(&va, va_mode);
	VATTR_WANTED(&va, va_create_time);
	VATTR_WANTED(&va, va_modify_time);
	if (VNOP_GETATTR(vp, &va, context) != 0 ||
	    !VATTR_IS_SUPPORTED(&va, va_uid) ||
	    !VATTR_IS_SUPPORTED(&va, va_gid) ||
	    !VATTR_IS_SUPPORTED(&va, va_mode)) {
		va.va_uid = KAUTH_UID_NONE;
		va.va_gid = KAUTH_GID_NONE;
		va.va_mode = S_IRUSR | S_IWUSR;
	}
	va.va_vaflags = VA_EXCLUSIVE;
	VATTR_SET(&va, va_type, VREG);
	/* We no longer change the access, but we still hide it. */
	VATTR_SET(&va, va_flags, UF_HIDDEN);

	/* Obtain the vnode for the shadow files directory. */
	if (get_shadow_dir(&dvp) != 0) {
		error = ENOTDIR;
		goto out;
	}
	if (!makestream) {
		/* See if someone else already has it open. */
		if (VNOP_LOOKUP(dvp, &svp, &cn, kernelctx) == 0) {
			/* Double check existence by asking for size. */
			VATTR_INIT(&va);
			VATTR_WANTED(&va, va_data_size);
			if (VNOP_GETATTR(svp, &va, context) == 0 &&
			    VATTR_IS_SUPPORTED(&va, va_data_size)) {
				goto out;  /* OK to use. */
			}
		}

		/*
		 * Otherwise make sure the resource fork data exists.
		 * Use the supplied context for accessing the AD file.
		 */
		error = vn_getxattr(vp, XATTR_RESOURCEFORK_NAME, NULL, &datasize,
		    XATTR_NOSECURITY, context);
		/*
		 * To maintain binary compatibility with legacy Carbon
		 * emulated resource fork support, if the resource fork
		 * doesn't exist but the Finder Info does,  then act as
		 * if an empty resource fork is present (see 4724359).
		 */
		if ((error == ENOATTR) &&
		    (vn_getxattr(vp, XATTR_FINDERINFO_NAME, NULL, &datasize,
		    XATTR_NOSECURITY, context) == 0)) {
			datasize = 0;
			error = 0;
		} else {
			if (error) {
				goto out;
			}

			/* If the resource fork exists, its size is expected to be non-zero. */
			if (datasize == 0) {
				error = ENOATTR;
				goto out;
			}
		}
	}
	/* Create the shadow stream file. */
	error = VNOP_CREATE(dvp, &svp, &cn, &va, kernelctx);
	if (error == 0) {
		vnode_recycle(svp);
		*creator = 1;
	} else if ((error == EEXIST) && !makestream) {
		error = VNOP_LOOKUP(dvp, &svp, &cn, kernelctx);
	} else if ((error == ENOENT) && !makestream) {
		/*
		 * We could have raced with a rmdir on the shadow directory
		 * post-lookup.  Retry from the beginning, 1x only, to
		 * try and see if we need to re-create the shadow directory
		 * in get_shadow_dir.
		 */
		if (retries == 0) {
			retries++;
			if (dvp) {
				vnode_put(dvp);
				dvp = NULLVP;
			}
			if (svp) {
				vnode_put(svp);
				svp = NULLVP;
			}
			goto retry_create;
		}
		/* Otherwise, just error out normally below */
	}

out:
	if (dvp) {
		vnode_put(dvp);
	}
	if (error) {
		/* On errors, clean up shadow stream file. */
		if (svp) {
			vnode_put(svp);
			svp = NULLVP;
		}
	}
	*svpp = svp;
	if (rsrcsize) {
		*rsrcsize = datasize;
	}
	return error;
}


static int
default_getnamedstream(vnode_t vp, vnode_t *svpp, const char *name, enum nsoperation op, vfs_context_t context)
{
	vnode_t  svp = NULLVP;
	uio_t auio = NULL;
	caddr_t  bufptr = NULL;
	size_t  bufsize = 0;
	size_t  datasize = 0;
	int  creator;
	int  error;

	/* need the kernel context for accessing the shadowfile */
	vfs_context_t kernelctx = vfs_context_kernel();

	/*
	 * Only the "com.apple.ResourceFork" stream is supported here.
	 */
	if (strncmp(name, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME)) != 0) {
		*svpp = NULLVP;
		return ENOATTR;
	}
retry:
	/*
	 * Obtain a shadow file for the resource fork I/O.
	 *
	 * Need to pass along the supplied context so that getshadowfile
	 * can access the AD file as needed, using it.
	 */
	error = getshadowfile(vp, &svp, 0, &datasize, &creator, context);
	if (error) {
		*svpp = NULLVP;
		return error;
	}

	/*
	 * The creator of the shadow file provides its file data,
	 * all other threads should wait until its ready.  In order to
	 * prevent a deadlock during error codepaths, we need to check if the
	 * vnode is being created, or if it has failed out. Regardless of success or
	 * failure, we set the VISSHADOW bit on the vnode, so we check that
	 * if the vnode's flags don't have VISNAMEDSTREAM set.  If it doesn't,
	 * then we can infer the creator isn't done yet.  If it's there, but
	 * VISNAMEDSTREAM is not set, then we can infer it errored out and we should
	 * try again.
	 */
	if (!creator) {
		vnode_lock(svp);
		if (svp->v_flag & VISNAMEDSTREAM) {
			/* data is ready, go use it */
			vnode_unlock(svp);
			goto out;
		} else {
			/* It's not ready, wait for it (sleep using v_parent as channel) */
			if ((svp->v_flag & VISSHADOW)) {
				/*
				 * No VISNAMEDSTREAM, but we did see VISSHADOW, indicating that the other
				 * thread is done with this vnode. Just unlock the vnode and try again
				 */
				vnode_unlock(svp);
			} else {
				/* Otherwise, sleep if the shadow file is not created yet */
				msleep((caddr_t)&svp->v_parent, &svp->v_lock, PINOD | PDROP,
				    "getnamedstream", NULL);
			}
			vnode_put(svp);
			svp = NULLVP;
			goto retry;
		}
	}

	/*
	 * Copy the real resource fork data into shadow stream file.
	 */
	if (op == NS_OPEN && datasize != 0) {
		size_t  offset;
		size_t  iosize;

		iosize = bufsize = MIN(datasize, NS_IOBUFSIZE);
		bufptr = kalloc_data(bufsize, Z_WAITOK);
		if (bufptr == NULL) {
			error = ENOMEM;
			goto out;
		}

		auio = uio_create(1, 0, UIO_SYSSPACE, UIO_READ);
		offset = 0;

		/* open the shadow file */
		error = VNOP_OPEN(svp, 0, kernelctx);
		if (error) {
			goto out;
		}
		while (offset < datasize) {
			size_t  tmpsize;

			iosize = MIN(datasize - offset, iosize);

			uio_reset(auio, offset, UIO_SYSSPACE, UIO_READ);
			uio_addiov(auio, (uintptr_t)bufptr, iosize);
			/* use supplied ctx for AD file */
			error = vn_getxattr(vp, XATTR_RESOURCEFORK_NAME, auio, &tmpsize,
			    XATTR_NOSECURITY, context);
			if (error) {
				break;
			}

			uio_reset(auio, offset, UIO_SYSSPACE, UIO_WRITE);
			uio_addiov(auio, (uintptr_t)bufptr, iosize);
			/* kernel context for writing shadowfile */
			error = VNOP_WRITE(svp, auio, 0, kernelctx);
			if (error) {
				break;
			}
			offset += iosize;
		}

		/* close shadow file */
		(void) VNOP_CLOSE(svp, 0, kernelctx);
	}
out:
	/* Wake up anyone waiting for svp file content */
	if (creator) {
		if (error == 0) {
			vnode_lock(svp);
			/* VISSHADOW would be set later on anyway, so we set it now */
			svp->v_flag |= (VISNAMEDSTREAM | VISSHADOW);
			wakeup((caddr_t)&svp->v_parent);
			vnode_unlock(svp);
		} else {
			/* On post create errors, get rid of the shadow file.  This
			 * way if there is another process waiting for initialization
			 * of the shadowfile by the current process will wake up and
			 * retry by creating and initializing the shadow file again.
			 * Also add the VISSHADOW bit here to indicate we're done operating
			 * on this vnode.
			 */
			(void)vnode_relenamedstream(vp, svp);
			vnode_lock(svp);
			svp->v_flag |= VISSHADOW;
			wakeup((caddr_t)&svp->v_parent);
			vnode_unlock(svp);
		}
	}

	kfree_data(bufptr, bufsize);
	if (auio) {
		uio_free(auio);
	}
	if (error) {
		/* On errors, clean up shadow stream file. */
		if (svp) {
			vnode_put(svp);
			svp = NULLVP;
		}
	}
	*svpp = svp;
	return error;
}

static int
default_makenamedstream(vnode_t vp, vnode_t *svpp, const char *name, vfs_context_t context)
{
	int creator;
	int error;

	/*
	 * Only the "com.apple.ResourceFork" stream is supported here.
	 */
	if (strncmp(name, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME)) != 0) {
		*svpp = NULLVP;
		return ENOATTR;
	}

	/* Supply the context to getshadowfile so it can manipulate the AD file */
	error = getshadowfile(vp, svpp, 1, NULL, &creator, context);

	/*
	 * Wake up any waiters over in default_getnamedstream().
	 */
	if ((error == 0) && (*svpp != NULL) && creator) {
		vnode_t svp = *svpp;

		vnode_lock(svp);
		/* If we're the creator, mark it as a named stream */
		svp->v_flag |= (VISNAMEDSTREAM | VISSHADOW);
		/* Wakeup any waiters on the v_parent channel */
		wakeup((caddr_t)&svp->v_parent);
		vnode_unlock(svp);
	}

	return error;
}

static int
default_removenamedstream(vnode_t vp, const char *name, vfs_context_t context)
{
	/*
	 * Only the "com.apple.ResourceFork" stream is supported here.
	 */
	if (strncmp(name, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME)) != 0) {
		return ENOATTR;
	}
	/*
	 * XXX - what about other opened instances?
	 */
	return default_removexattr(vp, XATTR_RESOURCEFORK_NAME, 0, context);
}

static bool
is_shadow_dir_valid(vnode_t parent_sdvp, vnode_t sdvp, vfs_context_t kernelctx)
{
	struct vnode_attr va;
	uint32_t tmp_fsid;
	bool is_valid = false;

	/* Make sure it's in fact a directory */
	if (sdvp->v_type != VDIR) {
		goto out;
	}

	/* Obtain the fsid for what should be the /private/var/run directory. */
	VATTR_INIT(&va);
	VATTR_WANTED(&va, va_fsid);
	if (VNOP_GETATTR(parent_sdvp, &va, kernelctx) != 0 ||
	    !VATTR_IS_SUPPORTED(&va, va_fsid)) {
		goto out;
	}

	tmp_fsid = va.va_fsid;

	VATTR_INIT(&va);
	VATTR_WANTED(&va, va_uid);
	VATTR_WANTED(&va, va_gid);
	VATTR_WANTED(&va, va_mode);
	VATTR_WANTED(&va, va_fsid);
	VATTR_WANTED(&va, va_dirlinkcount);
	VATTR_WANTED(&va, va_acl);
	/* Provide defaults for attrs that may not be supported */
	va.va_dirlinkcount = 1;
	va.va_acl = (kauth_acl_t) KAUTH_FILESEC_NONE;

	if (VNOP_GETATTR(sdvp, &va, kernelctx) != 0 ||
	    !VATTR_IS_SUPPORTED(&va, va_uid) ||
	    !VATTR_IS_SUPPORTED(&va, va_gid) ||
	    !VATTR_IS_SUPPORTED(&va, va_mode) ||
	    !VATTR_IS_SUPPORTED(&va, va_fsid)) {
		goto out;
	}

	/*
	 * Make sure its what we want:
	 *      - owned by root
	 *	- not writable by anyone
	 *	- on same file system as /private/var/run
	 *	- not a hard-linked directory
	 *	- no ACLs (they might grant write access)
	 */
	if ((va.va_uid != 0) || (va.va_gid != 0) ||
	    (va.va_mode & (S_IWUSR | S_IRWXG | S_IRWXO)) ||
	    (va.va_fsid != tmp_fsid) ||
	    (va.va_dirlinkcount != 1) ||
	    (va.va_acl != (kauth_acl_t) KAUTH_FILESEC_NONE)) {
		goto out;
	}

	/* If we get here, then the shadow dir is valid. */
	is_valid = true;

out:
	return is_valid;
}

static int
get_shadow_dir(vnode_t *sdvpp)
{
	vnode_t  dvp = NULLVP;
	vnode_t  sdvp = NULLVP;
	struct componentname  cn;
	struct vnode_attr  va;
	char tmpname[80];
	int  error;
	vfs_context_t kernelctx = vfs_context_kernel();

	/*
	 * Make sure to use the kernel context.  We want a singular view of
	 * the shadow dir regardless of chrooted processes.
	 */

	/*
	 * Obtain the vnode for "/private/var/run" directory using the kernel
	 * context.
	 *
	 * This is defined in the SHADOW_DIR_CONTAINER macro
	 */
	error = vnode_lookup(SHADOW_DIR_CONTAINER, VNODE_LOOKUP_NOFOLLOW_ANY, &dvp,
	    kernelctx);
	if (error) {
		error = ENOTSUP;
		goto out;
	}

	/*
	 * Create the shadow stream directory.
	 * 'dvp' below suggests the parent directory so
	 * we only need to provide the leaf entry name
	 */
	bzero(tmpname, sizeof(tmpname));
	MAKE_SHADOW_DIR_LEAF(rootvnode, tmpname);

	/*
	 * Look up the shadow directory to ensure that it still exists.
	 * By looking it up, we get an iocounted sdvp to use, and avoid some
	 * coherency issues in caching it when multiple threads may be trying to
	 * manipulate the pointers.
	 */
	error = vnode_lookupat(tmpname, VNODE_LOOKUP_NOFOLLOW, &sdvp, kernelctx, dvp);
	if (error == 0) {
		if (is_shadow_dir_valid(dvp, sdvp, kernelctx)) {
			/*
			 * If we get here, then we have successfully looked up the shadow
			 * dir, and it has an iocount from the lookup. Return the vp in the
			 * output argument.
			 */
			goto out;
		}

		/*
		 * Lookup returned us something that is not a valid shadow dir.
		 * Remove it and proceed with recreating the shadow dir.
		 */
		bzero(&cn, sizeof(cn));
		cn.cn_nameiop = DELETE;
		cn.cn_flags = ISLASTCN;
		cn.cn_context = kernelctx;
		cn.cn_pnbuf = tmpname;
		cn.cn_pnlen = sizeof(tmpname);
		cn.cn_nameptr = cn.cn_pnbuf;
		cn.cn_namelen = (int)strlen(tmpname);

		error = VNOP_REMOVE(dvp, sdvp, &cn, 0, kernelctx);
		if (error) {
			error = ENOTSUP;
			goto out;
		}

		vnode_put(sdvp);
	}

	/* In the failure case, no iocount is acquired */
	sdvp = NULLVP;
	bzero(&cn, sizeof(cn));
	cn.cn_nameiop = LOOKUP;
	cn.cn_flags = ISLASTCN;
	cn.cn_context = kernelctx;
	cn.cn_pnbuf = tmpname;
	cn.cn_pnlen = sizeof(tmpname);
	cn.cn_nameptr = cn.cn_pnbuf;
	cn.cn_namelen = (int)strlen(tmpname);

	/*
	 * owned by root, only readable by root, hidden
	 */
	VATTR_INIT(&va);
	VATTR_SET(&va, va_uid, 0);
	VATTR_SET(&va, va_gid, 0);
	VATTR_SET(&va, va_mode, S_IRUSR | S_IXUSR);
	VATTR_SET(&va, va_type, VDIR);
	VATTR_SET(&va, va_flags, UF_HIDDEN);
	va.va_vaflags = VA_EXCLUSIVE;

	error = VNOP_MKDIR(dvp, &sdvp, &cn, &va, kernelctx);

	/*
	 * There can be only one winner for an exclusive create.
	 */
	if (error == EEXIST) {
		/* loser has to look up directory */
		error = VNOP_LOOKUP(dvp, &sdvp, &cn, kernelctx);
		if (error == 0 && is_shadow_dir_valid(dvp, sdvp, kernelctx) == false) {
			goto baddir;
		}
	}
out:
	if (dvp) {
		vnode_put(dvp);
	}
	if (error) {
		/* On errors, clean up shadow stream directory. */
		if (sdvp) {
			vnode_put(sdvp);
			sdvp = NULLVP;
		}
	}
	*sdvpp = sdvp;
	return error;

baddir:
	/* This is not the dir we're looking for, move along */
	++shadow_sequence;  /* try something else next time */
	error = ENOTDIR;
	goto out;
}
#endif /* NAMEDSTREAMS */


#if CONFIG_APPLEDOUBLE
/*
 * Default Implementation (Non-native EA)
 */


/*
 *  Typical "._" AppleDouble Header File layout:
 * ------------------------------------------------------------
 *        MAGIC          0x00051607
 *        VERSION        0x00020000
 *        FILLER         0
 *        COUNT          2
 *    .-- AD ENTRY[0]    Finder Info Entry (must be first)
 * .--+-- AD ENTRY[1]    Resource Fork Entry (must be last)
 * |  '-> FINDER INFO
 * |      /////////////  Fixed Size Data (32 bytes)
 * |      EXT ATTR HDR
 * |      /////////////
 * |      ATTR ENTRY[0] --.
 * |      ATTR ENTRY[1] --+--.
 * |      ATTR ENTRY[2] --+--+--.
 * |         ...          |  |  |
 * |      ATTR ENTRY[N] --+--+--+--.
 * |      ATTR DATA 0   <-'  |  |  |
 * |      ////////////       |  |  |
 * |      ATTR DATA 1   <----'  |  |
 * |      /////////////         |  |
 * |      ATTR DATA 2   <-------'  |
 * |      /////////////            |
 * |         ...                   |
 * |      ATTR DATA N   <----------'
 * |      /////////////
 * |                      Attribute Free Space
 * |
 * '----> RESOURCE FORK
 *        /////////////   Variable Sized Data
 *        /////////////
 *        /////////////
 *        /////////////
 *        /////////////
 *        /////////////
 *           ...
 *        /////////////
 *
 * ------------------------------------------------------------
 *
 *  NOTE: The EXT ATTR HDR, ATTR ENTRY's and ATTR DATA's are
 *  stored as part of the Finder Info.  The length in the Finder
 *  Info AppleDouble entry includes the length of the extended
 *  attribute header, attribute entries, and attribute data.
 */

/*
 * On Disk Data Structures
 *
 * Note: Motorola 68K alignment and big-endian.
 *
 * See RFC 1740 for additional information about the AppleDouble file format.
 *
 */

#define ADH_MAGIC     0x00051607
#define ADH_VERSION   0x00020000
#define ADH_MACOSX    "Mac OS X        "

/*
 * AppleDouble Entry ID's
 */
#define AD_DATA          1   /* Data fork */
#define AD_RESOURCE      2   /* Resource fork */
#define AD_REALNAME      3   /* File's name on home file system */
#define AD_COMMENT       4   /* Standard Mac comment */
#define AD_ICONBW        5   /* Mac black & white icon */
#define AD_ICONCOLOR     6   /* Mac color icon */
#define AD_UNUSED        7   /* Not used */
#define AD_FILEDATES     8   /* File dates; create, modify, etc */
#define AD_FINDERINFO    9   /* Mac Finder info & extended info */
#define AD_MACINFO      10   /* Mac file info, attributes, etc */
#define AD_PRODOSINFO   11   /* Pro-DOS file info, attrib., etc */
#define AD_MSDOSINFO    12   /* MS-DOS file info, attributes, etc */
#define AD_AFPNAME      13   /* Short name on AFP server */
#define AD_AFPINFO      14   /* AFP file info, attrib., etc */
#define AD_AFPDIRID     15   /* AFP directory ID */
#define AD_ATTRIBUTES   AD_FINDERINFO


#define ATTR_FILE_PREFIX   "._"
#define ATTR_HDR_MAGIC     0x41545452   /* 'ATTR' */

#define ATTR_BUF_SIZE      4096        /* default size of the attr file and how much we'll grow by */

/* Implementation Limits */
#define ATTR_MAX_SIZE      AD_XATTR_MAXSIZE
#define ATTR_MAX_HDR_SIZE  65536
/*
 * Note: ATTR_MAX_HDR_SIZE is the largest attribute header
 * size supported (including the attribute entries). All of
 * the attribute entries must reside within this limit.  If
 * any of the attribute data crosses the ATTR_MAX_HDR_SIZE
 * boundry, then all of the attribute data I/O is performed
 * separately from the attribute header I/O.
 *
 * In particular, all of the attr_entry structures must lie
 * completely within the first ATTR_MAX_HDR_SIZE bytes of the
 * AppleDouble file.  However, the attribute data (i.e. the
 * contents of the extended attributes) may extend beyond the
 * first ATTR_MAX_HDR_SIZE bytes of the file.  Note that this
 * limit is to allow the implementation to optimize by reading
 * the first ATTR_MAX_HDR_SIZE bytes of the file.
 */


#define FINDERINFOSIZE  32

typedef struct apple_double_entry {
	u_int32_t   type;     /* entry type: see list, 0 invalid */
	u_int32_t   offset;   /* entry data offset from the beginning of the file. */
	u_int32_t   length;   /* entry data length in bytes. */
} __attribute__((aligned(2), packed)) apple_double_entry_t;


typedef struct apple_double_header {
	u_int32_t   magic;         /* == ADH_MAGIC */
	u_int32_t   version;       /* format version: 2 = 0x00020000 */
	u_int32_t   filler[4];
	u_int16_t   numEntries;    /* number of entries which follow */
	apple_double_entry_t   entries[2];  /* 'finfo' & 'rsrc' always exist */
	u_int8_t    finfo[FINDERINFOSIZE];  /* Must start with Finder Info (32 bytes) */
	u_int8_t    pad[2];        /* get better alignment inside attr_header */
} __attribute__((aligned(2), packed)) apple_double_header_t;

#define ADHDRSIZE  (4+4+16+2)

/* Entries are aligned on 4 byte boundaries */
typedef struct attr_entry {
	u_int32_t   offset;     /* file offset to data */
	u_int32_t   length;     /* size of attribute data */
	u_int16_t   flags;
	u_int8_t    namelen;
	u_int8_t    name[1];    /* NULL-terminated UTF-8 name (up to 128 bytes max) */
} __attribute__((aligned(2), packed)) attr_entry_t;


/* Header + entries must fit into 64K.  Data may extend beyond 64K. */
typedef struct attr_header {
	apple_double_header_t  appledouble;
	u_int32_t   magic;        /* == ATTR_HDR_MAGIC */
	u_int32_t   debug_tag;    /* for debugging == file id of owning file */
	u_int32_t   total_size;   /* file offset of end of attribute header + entries + data */
	u_int32_t   data_start;   /* file offset to attribute data area */
	u_int32_t   data_length;  /* length of attribute data area */
	u_int32_t   reserved[3];
	u_int16_t   flags;
	u_int16_t   num_attrs;
} __attribute__((aligned(2), packed)) attr_header_t;


/* Empty Resource Fork Header */
typedef struct rsrcfork_header {
	u_int32_t    fh_DataOffset;
	u_int32_t    fh_MapOffset;
	u_int32_t    fh_DataLength;
	u_int32_t    fh_MapLength;
	u_int8_t     systemData[112];
	u_int8_t     appData[128];
	u_int32_t    mh_DataOffset;
	u_int32_t    mh_MapOffset;
	u_int32_t    mh_DataLength;
	u_int32_t    mh_MapLength;
	u_int32_t    mh_Next;
	u_int16_t    mh_RefNum;
	u_int8_t     mh_Attr;
	u_int8_t     mh_InMemoryAttr;
	u_int16_t    mh_Types;
	u_int16_t    mh_Names;
	u_int16_t    typeCount;
} __attribute__((aligned(2), packed)) rsrcfork_header_t;

#define RF_FIRST_RESOURCE    256
#define RF_NULL_MAP_LENGTH    30
#define RF_EMPTY_TAG  "This resource fork intentionally left blank   "

/* Runtime information about the attribute file. */
typedef struct attr_info {
	vfs_context_t          context;
	vnode_t                filevp;
	size_t                 filesize;
	size_t                 iosize;
	u_int8_t               *rawdata;
	size_t                 rawsize;  /* minimum of filesize or ATTR_MAX_HDR_SIZE */
	apple_double_header_t  *filehdr;
	apple_double_entry_t   *finderinfo;
	apple_double_entry_t   *rsrcfork;
	attr_header_t          *attrhdr;
	attr_entry_t           *attr_entry;
	u_int8_t               readonly;
	u_int8_t               emptyfinderinfo;
} attr_info_t;


#define ATTR_SETTING  1

#define ATTR_ALIGN 3L  /* Use four-byte alignment */

#define ATTR_ENTRY_LENGTH(namelen)  \
	((sizeof(attr_entry_t) - 1 + (namelen) + ATTR_ALIGN) & (~ATTR_ALIGN))

#define ATTR_NEXT(ae)  \
	 (attr_entry_t *)((u_int8_t *)(ae) + ATTR_ENTRY_LENGTH((ae)->namelen))

#define ATTR_VALID(ae, ai)  \
	((&(ae)->namelen < ((ai).rawdata + (ai).rawsize)) && \
	 (u_int8_t *)ATTR_NEXT(ae) <= ((ai).rawdata + (ai).rawsize))

#define SWAP16(x)  OSSwapBigToHostInt16((x))
#define SWAP32(x)  OSSwapBigToHostInt32((x))
#define SWAP64(x)  OSSwapBigToHostInt64((x))


/*
 * sysctl stuff
 */
static int vfs_xattr_doubleagent_enabled = 1;
SYSCTL_DECL(_vfs_generic);
SYSCTL_INT(_vfs_generic, OID_AUTO, xattr_doubleagent_enabled, CTLFLAG_RW | CTLFLAG_LOCKED, &vfs_xattr_doubleagent_enabled, 0, "");

static int get_doubleagentd_port(mach_port_t *doubleagentd_port);

/*
 * VFS default xattr functions
 */
static int default_getxattr_vfs(vnode_t vp, const char *name, uio_t uio, size_t *size, int options,
    vfs_context_t context);
static int default_setxattr_vfs(vnode_t vp, const char *name, uio_t uio, int options,
    vfs_context_t context);
static int default_listxattr_vfs(vnode_t vp, uio_t uio, size_t *size, int options,
    vfs_context_t context);
static int default_removexattr_vfs(vnode_t vp, const char *name, int options,
    vfs_context_t context);

/*
 * DoubleAgent default xattr functions
 */
static int default_getxattr_doubleagent(vnode_t vp, const char *name,
    uio_t uio, size_t *size, int options, vfs_context_t context,
    mach_port_t);
static int default_setxattr_doubleagent(vnode_t vp, const char *name,
    uio_t uio, int options, vfs_context_t context, mach_port_t);
static int default_listxattr_doubleagent(vnode_t vp, uio_t uio, size_t *size,
    int options, vfs_context_t context, mach_port_t);
static int default_removexattr_doubleagent(vnode_t vp, const char *name,
    int options, vfs_context_t context, mach_port_t);


static u_int32_t emptyfinfo[8] = {0};


/*
 * Local support routines
 */
static void  close_xattrfile(struct fileglob *xfg, bool have_iocount, bool drop_iocount, vfs_context_t context);

static int  open_xattrfile(vnode_t vp, int fileflags, struct fileglob **xfgp,
    int64_t *file_sizep, vfs_context_t context);

static int  create_xattrfile(vnode_t xvp, u_int32_t fileid, vfs_context_t context);

static void  remove_xattrfile(struct fileglob *xfg, vnode_t xvp, vfs_context_t context);

static int  get_xattrinfo(vnode_t xvp, int setting, attr_info_t *ainfop, vfs_context_t context);

static void  rel_xattrinfo(attr_info_t *ainfop);

static int  write_xattrinfo(attr_info_t *ainfop);

static void  init_empty_resource_fork(rsrcfork_header_t * rsrcforkhdr);

static int make_xattrfile_port(struct fileglob *xfg, ipc_port_t *portp);

#if BYTE_ORDER == LITTLE_ENDIAN
static void  swap_adhdr(apple_double_header_t *adh);
static void  swap_attrhdr(attr_header_t *ah, attr_info_t* info);

#else
#define swap_adhdr(x)
#define swap_attrhdr(x, y)
#endif

static int  check_and_swap_attrhdr(attr_header_t *ah, attr_info_t* ainfop);
static int  shift_data_down(vnode_t xvp, off_t start, size_t len, off_t delta, vfs_context_t context);
static int  shift_data_up(vnode_t xvp, off_t start, size_t len, off_t delta, vfs_context_t context);


/*
 * Sanity check and swap the header of an AppleDouble file.  Assumes the buffer
 * is in big endian (as it would exist on disk).  Verifies the following:
 * - magic field
 * - version field
 * - number of entries
 * - that each entry fits within the file size
 *
 * If the header is invalid, ENOATTR is returned.
 *
 * NOTE: Does not attempt to validate the extended attributes header that
 * may be embedded in the Finder Info entry.
 */
static int
check_and_swap_apple_double_header(attr_info_t *ainfop)
{
	int i, j;
	u_int32_t header_end;
	u_int32_t entry_end;
	size_t rawsize;
	apple_double_header_t *header;

	rawsize = ainfop->rawsize;
	header = (apple_double_header_t *) ainfop->rawdata;

	/* Is the file big enough to contain an AppleDouble header? */
	if (rawsize < offsetof(apple_double_header_t, entries)) {
		return ENOATTR;
	}

	/* Swap the AppleDouble header fields to native order */
	header->magic = SWAP32(header->magic);
	header->version = SWAP32(header->version);
	header->numEntries = SWAP16(header->numEntries);

	/* Sanity check the AppleDouble header fields */
	if (header->magic != ADH_MAGIC ||
	    header->version != ADH_VERSION ||
	    header->numEntries < 1 ||
	    header->numEntries > 15) {
		return ENOATTR;
	}

	/* Calculate where the entries[] array ends */
	header_end = offsetof(apple_double_header_t, entries) +
	    header->numEntries * sizeof(apple_double_entry_t);

	/* Is the file big enough to contain the AppleDouble entries? */
	if (rawsize < header_end) {
		return ENOATTR;
	}

	/* Swap and sanity check each AppleDouble entry */
	for (i = 0; i < header->numEntries; i++) {
		/* Swap the per-entry fields to native order */
		header->entries[i].type   = SWAP32(header->entries[i].type);
		header->entries[i].offset = SWAP32(header->entries[i].offset);
		header->entries[i].length = SWAP32(header->entries[i].length);

		entry_end = header->entries[i].offset + header->entries[i].length;

		/*
		 * Does the entry's content start within the header itself,
		 * did the addition overflow, or does the entry's content
		 * extend past the end of the file?
		 */
		if (header->entries[i].offset < header_end ||
		    entry_end < header->entries[i].offset ||
		    entry_end > ainfop->filesize) {
			return ENOATTR;
		}

		/*
		 * Does the current entry's content overlap with a previous
		 * entry's content?
		 *
		 * Yes, this is O(N**2), and there are more efficient algorithms
		 * for testing pairwise overlap of N ranges when N is large.
		 * But we have already ensured N < 16, and N is almost always 2.
		 * So there's no point in using a more complex algorithm.
		 */

		for (j = 0; j < i; j++) {
			if (entry_end > header->entries[j].offset &&
			    header->entries[j].offset + header->entries[j].length > header->entries[i].offset) {
				return ENOATTR;
			}
		}
	}

	return 0;
}

/*
 * Retrieve the data of an extended attribute.
 */
static int
default_getxattr(vnode_t vp, const char *name, uio_t uio, size_t *size,
    __unused int options, vfs_context_t context)
{
	mach_port_t port;
	int error;

	if (vfs_xattr_doubleagent_enabled &&
	    get_doubleagentd_port(&port) == 0) {
		error = default_getxattr_doubleagent(vp, name, uio, size,
		    options, context, port);
		ipc_port_release_send(port);
	} else {
		error = default_getxattr_vfs(vp, name, uio, size, options,
		    context);
	}
	return error;
}

/*
 * Set the data of an extended attribute.
 */
static int __attribute__((noinline))
default_setxattr(vnode_t vp, const char *name, uio_t uio, int options,
    vfs_context_t context)
{
	mach_port_t port;
	int error;

	if (vfs_xattr_doubleagent_enabled &&
	    get_doubleagentd_port(&port) == 0) {
		error = default_setxattr_doubleagent(vp, name, uio, options,
		    context, port);
		ipc_port_release_send(port);
	} else {
		error = default_setxattr_vfs(vp, name, uio, options, context);
	}
	return error;
}

/*
 * Remove an extended attribute.
 */
static int
default_removexattr(vnode_t vp, const char *name, __unused int options,
    vfs_context_t context)
{
	mach_port_t port;
	int error;

	if (vfs_xattr_doubleagent_enabled &&
	    get_doubleagentd_port(&port) == 0) {
		error = default_removexattr_doubleagent(vp, name, options,
		    context, port);
		ipc_port_release_send(port);
	} else {
		error = default_removexattr_vfs(vp, name, options, context);
	}
	return error;
}

/*
 * Retrieve the list of extended attribute names.
 */
static int
default_listxattr(vnode_t vp, uio_t uio, size_t *size, __unused int options,
    vfs_context_t context)
{
	mach_port_t port;
	int error;

	if (vfs_xattr_doubleagent_enabled &&
	    get_doubleagentd_port(&port) == 0) {
		error = default_listxattr_doubleagent(vp, uio, size, options,
		    context, port);
		ipc_port_release_send(port);
	} else {
		error = default_listxattr_vfs(vp, uio, size, options, context);
	}
	return error;
}

/*
 * Retrieve the data of an extended attribute.
 * (VFS implementation).
 */
static int
default_getxattr_vfs(vnode_t vp, const char *name, uio_t uio, size_t *size,
    __unused int options, vfs_context_t context)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	attr_info_t ainfo;
	attr_header_t *header;
	attr_entry_t *entry;
	u_int8_t *attrdata;
	u_int32_t datalen;
	size_t namelen;
	int isrsrcfork;
	int fileflags;
	int i;
	int error;

	fileflags = FREAD | O_SHLOCK;
	isrsrcfork = strncmp(name, XATTR_RESOURCEFORK_NAME,
	    sizeof(XATTR_RESOURCEFORK_NAME)) == 0;

	if ((error = open_xattrfile(vp, fileflags, &xfg, NULL, context))) {
		return error;
	}
	xvp = fg_get_data(xfg);

	if ((error = get_xattrinfo(xvp, 0, &ainfo, context))) {
		close_xattrfile(xfg, true, true, context);
		return error;
	}

	/* Get the Finder Info. */
	if (strncmp(name, XATTR_FINDERINFO_NAME, sizeof(XATTR_FINDERINFO_NAME)) == 0) {
		if (ainfo.finderinfo == NULL || ainfo.emptyfinderinfo) {
			error = ENOATTR;
		} else if (uio == NULL) {
			*size = FINDERINFOSIZE;
			error = 0;
		} else if (uio_offset(uio) != 0) {
			error = EINVAL;
		} else if (uio_resid(uio) < FINDERINFOSIZE) {
			error = ERANGE;
		} else {
			attrdata = (u_int8_t*)ainfo.filehdr + ainfo.finderinfo->offset;
			error = uiomove((caddr_t)attrdata, FINDERINFOSIZE, uio);
		}
		goto out;
	}

	/* Read the Resource Fork. */
	if (isrsrcfork) {
		if (!vnode_isreg(vp)) {
			error = EPERM;
		} else if (ainfo.rsrcfork == NULL) {
			error = ENOATTR;
		} else if (uio == NULL) {
			*size = (size_t)ainfo.rsrcfork->length;
		} else {
			uio_setoffset(uio, uio_offset(uio) + ainfo.rsrcfork->offset);
			error = VNOP_READ(xvp, uio, 0, context);
			if (error == 0) {
				uio_setoffset(uio, uio_offset(uio) - ainfo.rsrcfork->offset);
			}
		}
		goto out;
	}

	if (ainfo.attrhdr == NULL || ainfo.attr_entry == NULL) {
		error = ENOATTR;
		goto out;
	}
	if (uio_offset(uio) != 0) {
		error = EINVAL;
		goto out;
	}
	error = ENOATTR;
	namelen = strlen(name) + 1;
	header = ainfo.attrhdr;
	entry = ainfo.attr_entry;
	/*
	 * Search for attribute name in the header.
	 */
	for (i = 0; i < header->num_attrs && ATTR_VALID(entry, ainfo); i++) {
		if (strncmp((const char *)entry->name, name, namelen) == 0) {
			datalen = entry->length;
			if (uio == NULL) {
				*size = datalen;
				error = 0;
				break;
			}
			if (uio_resid(uio) < (user_ssize_t)datalen) {
				error = ERANGE;
				break;
			}
			if (entry->offset + datalen < ATTR_MAX_HDR_SIZE) {
				attrdata = ((u_int8_t *)header + entry->offset);
				error = uiomove((caddr_t)attrdata, datalen, uio);
			} else {
				uio_setoffset(uio, entry->offset);
				error = VNOP_READ(xvp, uio, 0, context);
				uio_setoffset(uio, 0);
			}
			break;
		}
		entry = ATTR_NEXT(entry);
	}
out:
	rel_xattrinfo(&ainfo);
	close_xattrfile(xfg, true, true, context);

	return error;
}

/*
 * Set the data of an extended attribute.
 * (VFS implementation).
 */
static int __attribute__((noinline))
default_setxattr_vfs(vnode_t vp, const char *name, uio_t uio, int options, vfs_context_t context)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	attr_info_t ainfo;
	attr_header_t *header;
	attr_entry_t *entry;
	attr_entry_t *lastentry;
	u_int8_t *attrdata;
	size_t datalen;
	size_t entrylen;
	size_t datafreespace;
	int namelen;
	int found = 0;
	int i;
	int splitdata;
	int fileflags;
	int error;
	char finfo[FINDERINFOSIZE];

	datalen = uio_resid(uio);
	if (datalen > XATTR_MAXSIZE) {
		return E2BIG;
	}
	namelen = (int)strlen(name) + 1;
	if (namelen > UINT8_MAX) {
		return EINVAL;
	}
	entrylen = ATTR_ENTRY_LENGTH(namelen);

	/*
	 * By convention, Finder Info that is all zeroes is equivalent to not
	 * having a Finder Info EA.  So if we're trying to set the Finder Info
	 * to all zeroes, then delete it instead.  If a file didn't have an
	 * AppleDouble file before, this prevents creating an AppleDouble file
	 * with no useful content.
	 *
	 * If neither XATTR_CREATE nor XATTR_REPLACE were specified, we check
	 * for all zeroes Finder Info before opening the AppleDouble file.
	 * But if either of those options were specified, we need to open the
	 * AppleDouble file to see whether there was already Finder Info (so we
	 * can return an error if needed); this case is handled further below.
	 *
	 * NOTE: this copies the Finder Info data into the "finfo" local.
	 */
	if (strncmp(name, XATTR_FINDERINFO_NAME, sizeof(XATTR_FINDERINFO_NAME)) == 0) {
		/*
		 * TODO: check the XATTR_CREATE and XATTR_REPLACE flags.
		 * That means we probably have to open_xattrfile and get_xattrinfo.
		 */
		if (uio_offset(uio) != 0) {
			return EINVAL;
		}

		if (datalen != FINDERINFOSIZE) {
			return ERANGE;
		}

		error = uiomove(finfo, (int)datalen, uio);
		if (error) {
			return error;
		}
		if ((options & (XATTR_CREATE | XATTR_REPLACE)) == 0 &&
		    bcmp(finfo, emptyfinfo, FINDERINFOSIZE) == 0) {
			error = default_removexattr(vp, name, 0, context);
			if (error == ENOATTR) {
				error = 0;
			}
			return error;
		}
	}

start:
	/*
	 * Open the file locked since setting an attribute
	 * can change the layout of the Apple Double file.
	 */
	fileflags = FREAD | FWRITE | O_EXLOCK;
	if ((error = open_xattrfile(vp, O_CREAT | fileflags, &xfg, NULL, context))) {
		return error;
	}
	xvp = fg_get_data(xfg);

	if ((error = get_xattrinfo(xvp, ATTR_SETTING, &ainfo, context))) {
		close_xattrfile(xfg, true, true, context);
		return error;
	}

	/* Set the Finder Info. */
	if (strncmp(name, XATTR_FINDERINFO_NAME, sizeof(XATTR_FINDERINFO_NAME)) == 0) {
		if (ainfo.finderinfo && !ainfo.emptyfinderinfo) {
			/* attr exists and "create" was specified? */
			if (options & XATTR_CREATE) {
				error = EEXIST;
				goto out;
			}
		} else {
			/* attr doesn't exists and "replace" was specified? */
			if (options & XATTR_REPLACE) {
				error = ENOATTR;
				goto out;
			}
		}
		if (options != 0 && bcmp(finfo, emptyfinfo, FINDERINFOSIZE) == 0) {
			/*
			 * Setting the Finder Info to all zeroes is equivalent to
			 * removing it.  Close the xattr file and let
			 * default_removexattr do the work (including deleting
			 * the xattr file if there are no other xattrs).
			 *
			 * Note that we have to handle the case where the
			 * Finder Info was already all zeroes, and we ignore
			 * ENOATTR.
			 *
			 * The common case where options == 0 was handled above.
			 */
			rel_xattrinfo(&ainfo);
			close_xattrfile(xfg, true, true, context);
			error = default_removexattr(vp, name, 0, context);
			if (error == ENOATTR) {
				error = 0;
			}
			return error;
		}
		if (ainfo.finderinfo) {
			attrdata = (u_int8_t *)ainfo.filehdr + ainfo.finderinfo->offset;
			bcopy(finfo, attrdata, datalen);
			ainfo.iosize = sizeof(attr_header_t);
			error = write_xattrinfo(&ainfo);
			goto out;
		}
		error = ENOATTR;
		goto out;
	}

	/* Write the Resource Fork. */
	if (strncmp(name, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME)) == 0) {
		off_t endoffset;

		if (!vnode_isreg(vp)) {
			error = EPERM;
			goto out;
		}
		/* Make sure we have a rsrc fork pointer.. */
		if (ainfo.rsrcfork == NULL) {
			error = ENOATTR;
			goto out;
		}
		if (ainfo.rsrcfork) {
			if (ainfo.rsrcfork->length != 0) {
				if (options & XATTR_CREATE) {
					/* attr exists, and create specified ? */
					error = EEXIST;
					goto out;
				}
			} else {
				/* Zero length AD rsrc fork */
				if (options & XATTR_REPLACE) {
					/* attr doesn't exist (0-length), but replace specified ? */
					error = ENOATTR;
					goto out;
				}
			}
		} else {
			/* We can't do much if we somehow didn't get an AD rsrc pointer */
			error = ENOATTR;
			goto out;
		}

		endoffset = uio_resid(uio) + uio_offset(uio); /* new size */
		if (endoffset > UINT32_MAX || endoffset < 0) {
			error = EINVAL;
			goto out;
		}
		uio_setoffset(uio, uio_offset(uio) + ainfo.rsrcfork->offset);
		error = VNOP_WRITE(xvp, uio, 0, context);
		if (error) {
			goto out;
		}
		uio_setoffset(uio, uio_offset(uio) - ainfo.rsrcfork->offset);
		if (endoffset > ainfo.rsrcfork->length) {
			ainfo.rsrcfork->length = (u_int32_t)endoffset;
			ainfo.iosize = sizeof(attr_header_t);
			error = write_xattrinfo(&ainfo);
			goto out;
		}
		goto out;
	}

	if (datalen > ATTR_MAX_SIZE) {
		return E2BIG;  /* EINVAL instead ? */
	}

	if (ainfo.attrhdr == NULL) {
		error = ENOATTR;
		goto out;
	}
	header = ainfo.attrhdr;
	entry = ainfo.attr_entry;

	/* Check if data area crosses the maximum header size. */
	if ((header->data_start + header->data_length + entrylen + datalen) > ATTR_MAX_HDR_SIZE) {
		splitdata = 1;  /* do data I/O separately */
	} else {
		splitdata = 0;
	}

	/*
	 * See if attribute already exists.
	 */
	for (i = 0; i < header->num_attrs && ATTR_VALID(entry, ainfo); i++) {
		if (strncmp((const char *)entry->name, name, namelen) == 0) {
			found = 1;
			break;
		}
		entry = ATTR_NEXT(entry);
	}

	if (found) {
		if (options & XATTR_CREATE) {
			error = EEXIST;
			goto out;
		}
		if (datalen == entry->length) {
			if (splitdata) {
				uio_setoffset(uio, entry->offset);
				error = VNOP_WRITE(xvp, uio, 0, context);
				uio_setoffset(uio, 0);
				if (error) {
					printf("setxattr: VNOP_WRITE error %d\n", error);
				}
			} else {
				attrdata = (u_int8_t *)header + entry->offset;
				error = uiomove((caddr_t)attrdata, (int)datalen, uio);
				if (error) {
					goto out;
				}
				ainfo.iosize = ainfo.attrhdr->data_start + ainfo.attrhdr->data_length;
				error = write_xattrinfo(&ainfo);
				if (error) {
					printf("setxattr: write_xattrinfo error %d\n", error);
				}
			}
			goto out;
		} else {
			/*
			 * Brute force approach - just remove old entry and set new entry.
			 */
			found = 0;
			rel_xattrinfo(&ainfo);
			close_xattrfile(xfg, true, true, context);
			error = default_removexattr(vp, name, options, context);
			if (error) {
				return error;
			}
			/* Clear XATTR_REPLACE option since we just removed the attribute. */
			options &= ~XATTR_REPLACE;
			goto start; /* start over */
		}
	} else {
		if (!ATTR_VALID(entry, ainfo)) {
			error = ENOSPC;
			goto out;
		}
	}

	if (options & XATTR_REPLACE) {
		error = ENOATTR;  /* nothing there to replace */
		goto out;
	}
	/* Check if header size limit has been reached. */
	if ((header->data_start + entrylen) > ATTR_MAX_HDR_SIZE) {
		error = ENOSPC;
		goto out;
	}

	datafreespace = header->total_size - (header->data_start + header->data_length);

	/* Check if we need more space. */
	if ((datalen + entrylen) > datafreespace) {
		size_t growsize;

		growsize = roundup((datalen + entrylen) - datafreespace, ATTR_BUF_SIZE);

		/* Clip roundup size when we can still fit in ATTR_MAX_HDR_SIZE. */
		if (!splitdata && (header->total_size + growsize) > ATTR_MAX_HDR_SIZE) {
			growsize = ATTR_MAX_HDR_SIZE - header->total_size;
		}

		ainfo.filesize += growsize;
		error = vnode_setsize(xvp, ainfo.filesize, 0, context);
		if (error) {
			printf("setxattr: VNOP_TRUNCATE error %d\n", error);
		}
		if (error) {
			goto out;
		}

		/*
		 * Move the resource fork out of the way.
		 */
		if (ainfo.rsrcfork) {
			if (ainfo.rsrcfork->length != 0) {
				shift_data_down(xvp,
				    ainfo.rsrcfork->offset,
				    ainfo.rsrcfork->length,
				    growsize, context);
			}
			ainfo.rsrcfork->offset += growsize;
		}
		ainfo.finderinfo->length += growsize;
		header->total_size += growsize;
	}

	/* Make space for a new entry. */
	if (splitdata) {
		shift_data_down(xvp,
		    header->data_start,
		    header->data_length,
		    entrylen, context);
	} else {
		bcopy((u_int8_t *)header + header->data_start,
		    (u_int8_t *)header + header->data_start + entrylen,
		    header->data_length);
	}
	header->data_start += entrylen;

	/* Fix up entry data offsets. */
	lastentry = entry;
	for (entry = ainfo.attr_entry; entry != lastentry && ATTR_VALID(entry, ainfo); entry = ATTR_NEXT(entry)) {
		entry->offset += entrylen;
	}

	/*
	 * If the attribute data area is entirely within
	 * the header buffer, then just update the buffer,
	 * otherwise we'll write it separately to the file.
	 */
	if (splitdata) {
		off_t offset;

		/* Write new attribute data after the end of existing data. */
		offset = header->data_start + header->data_length;
		uio_setoffset(uio, offset);
		error = VNOP_WRITE(xvp, uio, 0, context);
		uio_setoffset(uio, 0);
		if (error) {
			printf("setxattr: VNOP_WRITE error %d\n", error);
			goto out;
		}
	} else {
		attrdata = (u_int8_t *)header + header->data_start + header->data_length;

		error = uiomove((caddr_t)attrdata, (int)datalen, uio);
		if (error) {
			printf("setxattr: uiomove error %d\n", error);
			goto out;
		}
	}

	/* Create the attribute entry. */
	lastentry->length = (u_int32_t)datalen;
	lastentry->offset = header->data_start + header->data_length;
	lastentry->namelen = (u_int8_t)namelen;
	lastentry->flags = 0;
	bcopy(name, &lastentry->name[0], namelen);

	/* Update the attributes header. */
	header->num_attrs++;
	header->data_length += datalen;

	if (splitdata) {
		/* Only write the entries, since the data was written separately. */
		ainfo.iosize = ainfo.attrhdr->data_start;
	} else {
		/* The entry and data are both in the header; write them together. */
		ainfo.iosize = ainfo.attrhdr->data_start + ainfo.attrhdr->data_length;
	}
	error = write_xattrinfo(&ainfo);
	if (error) {
		printf("setxattr: write_xattrinfo error %d\n", error);
	}

out:
	rel_xattrinfo(&ainfo);
	close_xattrfile(xfg, true, true, context);

	/* Touch the change time if we changed an attribute. */
	if (error == 0) {
		struct vnode_attr va;

		/* Re-write the mtime to cause a ctime change. */
		VATTR_INIT(&va);
		VATTR_WANTED(&va, va_modify_time);
		if (vnode_getattr(vp, &va, context) == 0) {
			VATTR_INIT(&va);
			VATTR_SET(&va, va_modify_time, va.va_modify_time);
			(void) vnode_setattr(vp, &va, context);
		}
	}

	post_event_if_success(vp, error, NOTE_ATTRIB);

	return error;
}


/*
 * Remove an extended attribute.
 * (VFS implementation).
 */
static int
default_removexattr_vfs(vnode_t vp, const char *name, __unused int options, vfs_context_t context)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	attr_info_t ainfo;
	attr_header_t *header;
	attr_entry_t *entry;
	attr_entry_t *oldslot;
	u_int8_t *attrdata;
	u_int32_t dataoff;
	size_t datalen;
	size_t entrylen;
	int namelen;
	int found = 0, lastone = 0;
	int i;
	int splitdata;
	int attrcount = 0;
	int isrsrcfork;
	int fileflags;
	int error;

	fileflags = FREAD | FWRITE | O_EXLOCK;
	isrsrcfork = strncmp(name, XATTR_RESOURCEFORK_NAME,
	    sizeof(XATTR_RESOURCEFORK_NAME)) == 0;

	if ((error = open_xattrfile(vp, fileflags, &xfg, NULL, context))) {
		return error;
	}
	xvp = fg_get_data(xfg);

	if ((error = get_xattrinfo(xvp, 0, &ainfo, context))) {
		close_xattrfile(xfg, true, true, context);
		return error;
	}
	if (ainfo.attrhdr) {
		attrcount += ainfo.attrhdr->num_attrs;
	}
	if (ainfo.rsrcfork) {
		++attrcount;
	}
	if (ainfo.finderinfo && !ainfo.emptyfinderinfo) {
		++attrcount;
	}

	/* Clear the Finder Info. */
	if (strncmp(name, XATTR_FINDERINFO_NAME, sizeof(XATTR_FINDERINFO_NAME)) == 0) {
		if (ainfo.finderinfo == NULL || ainfo.emptyfinderinfo) {
			error = ENOATTR;
			goto out;
		}
		/* On removal of last attribute the ._ file is removed. */
		if (--attrcount == 0) {
			goto out;
		}
		attrdata = (u_int8_t *)ainfo.filehdr + ainfo.finderinfo->offset;
		bzero((caddr_t)attrdata, FINDERINFOSIZE);
		error = write_xattrinfo(&ainfo);
		goto out;
	}

	/* Clear the Resource Fork. */
	if (isrsrcfork) {
		if (!vnode_isreg(vp)) {
			error = EPERM;
			goto out;
		}
		if (ainfo.rsrcfork == NULL || ainfo.rsrcfork->length == 0) {
			error = ENOATTR;
			goto out;
		}
		/* On removal of last attribute the ._ file is removed. */
		if (--attrcount == 0) {
			goto out;
		}
		/*
		 * XXX
		 * If the resource fork isn't the last AppleDouble
		 * entry then the space needs to be reclaimed by
		 * shifting the entries after the resource fork.
		 */
		if ((ainfo.rsrcfork->offset + ainfo.rsrcfork->length) == ainfo.filesize) {
			ainfo.filesize -= ainfo.rsrcfork->length;
			error = vnode_setsize(xvp, ainfo.filesize, 0, context);
		}
		if (error == 0) {
			ainfo.rsrcfork->length = 0;
			ainfo.iosize = sizeof(attr_header_t);
			error = write_xattrinfo(&ainfo);
		}
		goto out;
	}

	if (ainfo.attrhdr == NULL) {
		error = ENOATTR;
		goto out;
	}
	namelen = (int)strlen(name) + 1;
	header = ainfo.attrhdr;
	entry = ainfo.attr_entry;

	/*
	 * See if this attribute exists.
	 */
	for (i = 0; i < header->num_attrs && ATTR_VALID(entry, ainfo); i++) {
		if (strncmp((const char *)entry->name, name, namelen) == 0) {
			found = 1;
			if ((i + 1) == header->num_attrs) {
				lastone = 1;
			}
			break;
		}
		entry = ATTR_NEXT(entry);
	}
	if (!found) {
		error = ENOATTR;
		goto out;
	}
	/* On removal of last attribute the ._ file is removed. */
	if (--attrcount == 0) {
		goto out;
	}

	datalen = entry->length;
	dataoff = entry->offset;
	entrylen = ATTR_ENTRY_LENGTH(namelen);
	if ((header->data_start + header->data_length) > ATTR_MAX_HDR_SIZE) {
		splitdata = 1;
	} else {
		splitdata = 0;
	}

	/* Remove the attribute entry. */
	if (!lastone) {
		bcopy((u_int8_t *)entry + entrylen, (u_int8_t *)entry,
		    ((size_t)header + header->data_start) - ((size_t)entry + entrylen));
	}

	/* Adjust the attribute data. */
	if (splitdata) {
		shift_data_up(xvp,
		    header->data_start,
		    dataoff - header->data_start,
		    entrylen,
		    context);
		if (!lastone) {
			shift_data_up(xvp,
			    dataoff + datalen,
			    (header->data_start + header->data_length) - (dataoff + datalen),
			    datalen + entrylen,
			    context);
		}
		/* XXX write zeros to freed space ? */
		ainfo.iosize = ainfo.attrhdr->data_start - entrylen;
	} else {
		bcopy((u_int8_t *)header + header->data_start,
		    (u_int8_t *)header + header->data_start - entrylen,
		    dataoff - header->data_start);
		if (!lastone) {
			bcopy((u_int8_t *)header + dataoff + datalen,
			    (u_int8_t *)header + dataoff - entrylen,
			    (header->data_start + header->data_length) - (dataoff + datalen));
		}
		bzero(((u_int8_t *)header + header->data_start + header->data_length) - (datalen + entrylen), (datalen + entrylen));
		ainfo.iosize = ainfo.attrhdr->data_start + ainfo.attrhdr->data_length;
	}

	/* Adjust the header values and entry offsets. */
	header->num_attrs--;
	header->data_start -= entrylen;
	header->data_length -= datalen;

	oldslot = entry;
	entry = ainfo.attr_entry;
	for (i = 0; i < header->num_attrs && ATTR_VALID(entry, ainfo); i++) {
		entry->offset -= entrylen;
		if (entry >= oldslot) {
			entry->offset -= datalen;
		}
		entry = ATTR_NEXT(entry);
	}
	error = write_xattrinfo(&ainfo);
	if (error) {
		printf("removexattr: write_xattrinfo error %d\n", error);
	}
out:
	rel_xattrinfo(&ainfo);

	/* When there are no more attributes remove the ._ file. */
	if (attrcount == 0) {
		remove_xattrfile(xfg, xvp, context);
	} else {
		close_xattrfile(xfg, true, true, context);
	}
	/* Touch the change time if we changed an attribute. */
	if (error == 0) {
		struct vnode_attr va;

		/* Re-write the mtime to cause a ctime change. */
		VATTR_INIT(&va);
		VATTR_WANTED(&va, va_modify_time);
		if (vnode_getattr(vp, &va, context) == 0) {
			VATTR_INIT(&va);
			VATTR_SET(&va, va_modify_time, va.va_modify_time);
			(void) vnode_setattr(vp, &va, context);
		}
	}

	post_event_if_success(vp, error, NOTE_ATTRIB);

	return error;
}


/*
 * Retrieve the list of extended attribute names.
 * (VFS implementation).
 */
static int
default_listxattr_vfs(vnode_t vp, uio_t uio, size_t *size, __unused int options, vfs_context_t context)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	attr_info_t ainfo;
	attr_entry_t *entry;
	int i, count;
	int error;

	/*
	 * We do not zero "*size" here as we don't want to stomp a size set when
	 * VNOP_LISTXATTR processed any native EAs.  That size is initially zeroed by the
	 * system call layer, up in listxattr or flistxattr.
	 */

	if ((error = open_xattrfile(vp, FREAD | O_SHLOCK, &xfg, NULL, context))) {
		if (error == ENOATTR) {
			error = 0;
		}
		return error;
	}
	xvp = fg_get_data(xfg);

	if ((error = get_xattrinfo(xvp, 0, &ainfo, context))) {
		if (error == ENOATTR) {
			error = 0;
		}
		close_xattrfile(xfg, true, true, context);
		return error;
	}

	/* Check for Finder Info. */
	if (ainfo.finderinfo && !ainfo.emptyfinderinfo) {
		if (uio == NULL) {
			*size += sizeof(XATTR_FINDERINFO_NAME);
		} else if (uio_resid(uio) < (user_ssize_t)sizeof(XATTR_FINDERINFO_NAME)) {
			error = ERANGE;
			goto out;
		} else {
			error = uiomove(XATTR_FINDERINFO_NAME,
			    sizeof(XATTR_FINDERINFO_NAME), uio);
			if (error) {
				error = ERANGE;
				goto out;
			}
		}
	}

	/* Check for Resource Fork. */
	if (vnode_isreg(vp) && ainfo.rsrcfork) {
		if (uio == NULL) {
			*size += sizeof(XATTR_RESOURCEFORK_NAME);
		} else if (uio_resid(uio) < (user_ssize_t)sizeof(XATTR_RESOURCEFORK_NAME)) {
			error = ERANGE;
			goto out;
		} else {
			error = uiomove(XATTR_RESOURCEFORK_NAME,
			    sizeof(XATTR_RESOURCEFORK_NAME), uio);
			if (error) {
				error = ERANGE;
				goto out;
			}
		}
	}

	/* Check for attributes. */
	if (ainfo.attrhdr) {
		count = ainfo.attrhdr->num_attrs;
		for (i = 0, entry = ainfo.attr_entry; i < count && ATTR_VALID(entry, ainfo); i++) {
			if (xattr_protected((const char *)entry->name) ||
			    ((entry->namelen < XATTR_MAXNAMELEN) &&
			    (entry->name[entry->namelen] == '\0') &&
			    (xattr_validatename((const char *)entry->name) != 0))) {
				entry = ATTR_NEXT(entry);
				continue;
			}
			if (uio == NULL) {
				*size += entry->namelen;
				entry = ATTR_NEXT(entry);
				continue;
			}
			if (uio_resid(uio) < entry->namelen) {
				error = ERANGE;
				break;
			}
			error = uiomove((caddr_t) entry->name, entry->namelen, uio);
			if (error) {
				if (error != EFAULT) {
					error = ERANGE;
				}
				break;
			}
			entry = ATTR_NEXT(entry);
		}
	}
out:
	rel_xattrinfo(&ainfo);
	close_xattrfile(xfg, true, true, context);

	return error;
}

static int
get_doubleagentd_port(mach_port_t *doubleagentd_port)
{
	kern_return_t ret;

	*doubleagentd_port = MACH_PORT_NULL;
	ret = host_get_doubleagentd_port(host_priv_self(), doubleagentd_port);
	if (ret != KERN_SUCCESS) {
		printf("vfs_xattr: can't get doubleagentd port, status 0x%08x\n", ret);
		return EIO;
	}
	if (!IPC_PORT_VALID(*doubleagentd_port)) {
		printf("vfs_xattr: doubleagentd port not valid\n");
		return EIO;
	}
	return 0;
}

/*
 * Retrieve the data of an extended attribute.
 * (Using DoubleAgent to parse the AD file).
 */
static int
default_getxattr_doubleagent(vnode_t vp, const char *name, uio_t uio,
    size_t *size, __unused int options, vfs_context_t context,
    mach_port_t doubleagentd_port)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	mach_port_t fileport = MACH_PORT_NULL;
	uint64_t value_offset = 0;
	uint64_t value_length = 0;
	int64_t fsize;
	int isrsrcfork;
	int fileflags;
	int error;
	kern_return_t kr;
	char cName[XATTR_MAXNAMELEN] = {0};
	bool have_iocount = true;

	fileflags = FREAD | O_SHLOCK;
	isrsrcfork = strncmp(name, XATTR_RESOURCEFORK_NAME,
	    sizeof(XATTR_RESOURCEFORK_NAME)) == 0;

	if ((error = open_xattrfile(vp, fileflags, &xfg, &fsize, context))) {
		goto out;
	}
	xvp = fg_get_data(xfg);
	if ((error = make_xattrfile_port(xfg, &fileport))) {
		goto out;
	}

	/* Drop the iocount before upcalling to doubleagentd. */
	vnode_put(xvp);
	have_iocount = false;

	strncpy(cName, name, XATTR_MAXNAMELEN);

	/*
	 * Call doubleagentd to look up the xattr.  The fileport argument
	 * is declared move-send, so the Mig stub consumes it.
	 */
	kr = doubleagent_lookup_xattr(doubleagentd_port, fileport, fsize, cName,
	    &error, &value_offset, &value_length);
	if (kr != KERN_SUCCESS) {
		error = EIO;
	}
	if (error == 0) {
		error = vnode_getwithref(xvp);
	}
	if (error) {
		goto out;
	}
	have_iocount = true;
	if (uio != NULL) {
		if (isrsrcfork) {
			// Resource Fork case is a bit different,
			// as we can have a non-zero uio offset.
			uio_setoffset(uio, uio_offset(uio) + value_offset);
			error = VNOP_READ(xvp, uio, 0, context);
			if (error == 0) {
				uio_setoffset(uio, uio_offset(uio) - value_offset);
			}
		} else {
			if (uio_resid(uio) < value_length) {
				error = ERANGE;
				goto out;
			}

			// Read from the relevant offset in the AD file into the uio.
			user_ssize_t orig_resid = uio_resid(uio);
			uio_setoffset(uio, value_offset);
			uio_setresid(uio, value_length);

			error = VNOP_READ(xvp, uio, 0, context);

			uio_setoffset(uio, 0);
			uio_setresid(uio, orig_resid - value_length + uio_resid(uio));
		}
	}

	*size = value_length;

out:
	if (xfg != NULL) {
		close_xattrfile(xfg, have_iocount, true, context);
	}
	return error;
}

/*
 * Retrieve the list of extended attribute names.
 * (Using DoubleAgent to parse the AD file).
 */
static int
default_listxattr_doubleagent(vnode_t vp, uio_t uio, size_t *size,
    __unused int options, vfs_context_t context, mach_port_t doubleagentd_port)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	int64_t fsize;
	int error;

	mach_port_t fileport = MACH_PORT_NULL;
	kern_return_t kr;
	void *buf = NULL;
	listxattrs_result_t *result;
	bool have_iocount = true;

	/*
	 * We do not zero "*size" here as we don't want to stomp a size set
	 * when VNOP_LISTXATTR() processed any native EAs.  That size is
	 * initially zeroed by the system call layer, up in listxattr() or
	 * flistxattr().
	 */

	if ((error = open_xattrfile(vp, FREAD | O_SHLOCK, &xfg, &fsize,
	    context))) {
		if (error == ENOATTR) {
			error = 0;
		}
		goto out;
	}
	xvp = fg_get_data(xfg);
	if ((error = make_xattrfile_port(xfg, &fileport))) {
		goto out;
	}

	/* Drop the iocount before upcalling to doubleagentd. */
	vnode_put(xvp);
	have_iocount = false;

	buf = kalloc_data(sizeof(listxattrs_result_t), Z_WAITOK);
	result = (listxattrs_result_t *)buf;

	/*
	 * Call doubleagentd to list the xattrs.  The fileport argument
	 * is declared move-send, so the Mig stub consumes it.
	 */
	kr = doubleagent_list_xattrs(doubleagentd_port, fileport, fsize, &error,
	    result);
	if (kr != KERN_SUCCESS) {
		error = EIO;
	}
	if (error == 0) {
		error = vnode_getwithref(xvp);
	}
	if (error) {
		goto out;
	}
	have_iocount = true;

	if (uio != NULL) {
		if (uio_resid(uio) < result->namesLength) {
			error = ERANGE;
			goto out;
		}
		// copy the relevant part of the result into the uio.
		error = uiomove((const char *)result->data, (int)result->namesLength, uio);
		if (error) {
			if (error != EFAULT) {
				error = ERANGE;
			}
			goto out;
		}
	}

	/*
	 * Set *size, while preserving any previous value from
	 * VNOP_LISTXATTR().
	 */
	*size += result->namesLength;

out:
	if (xfg != NULL) {
		close_xattrfile(xfg, have_iocount, true, context);
	}
	if (buf != NULL) {
		kfree_data(buf, sizeof(listxattrs_result_t));
	}
	return error;
}

/*
 * Set the data of an extended attribute.
 * (Using DoubleAgent to parse the AD file).
 */
static int __attribute__((noinline))
default_setxattr_doubleagent(vnode_t vp, const char *name, uio_t uio,
    int options, vfs_context_t context, mach_port_t doubleagentd_port)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	size_t datalen;
	int namelen;
	int fileflags;
	int error;
	char cName[XATTR_MAXNAMELEN] = {0};
	char finfo[FINDERINFOSIZE];
	uio_t finfo_uio = NULL;
	mach_port_t fileport = MACH_PORT_NULL;
	uint64_t value_offset = 0;
	int64_t fsize;
	kern_return_t kr;
	bool have_iocount = true;

	datalen = uio_resid(uio);
	if (datalen > XATTR_MAXSIZE) {
		return E2BIG;
	}
	namelen = (int)strlen(name) + 1;
	if (namelen > UINT8_MAX) {
		return EINVAL;
	}

	/*
	 * By convention, Finder Info that is all zeroes is equivalent to not
	 * having a Finder Info EA.  So if we're trying to set the Finder Info
	 * to all zeroes, then delete it instead.  If a file didn't have an
	 * AppleDouble file before, this prevents creating an AppleDouble file
	 * with no useful content.
	 *
	 * If neither XATTR_CREATE nor XATTR_REPLACE were specified, we check
	 * for all zeroes Finder Info before opening the AppleDouble file.
	 * But if either of those options were specified, we need to open the
	 * AppleDouble file to see whether there was already Finder Info (so we
	 * can return an error if needed); this case is handled in DoubleAgent.
	 */
	if (strncmp(name, XATTR_FINDERINFO_NAME, sizeof(XATTR_FINDERINFO_NAME)) == 0) {
		if (uio_offset(uio) != 0) {
			return EINVAL;
		}

		if (datalen != FINDERINFOSIZE) {
			return ERANGE;
		}

		// Duplicate the uio to keep it as-is for later.
		finfo_uio = uio_duplicate(uio);
		// Get the finfo data from the duplicated uio.
		error = uiomove(finfo, (int)datalen, finfo_uio);
		uio_free(finfo_uio);
		if (error) {
			return error;
		}
		if ((options & (XATTR_CREATE | XATTR_REPLACE)) == 0 &&
		    bcmp(finfo, emptyfinfo, FINDERINFOSIZE) == 0) {
			error = default_removexattr(vp, name, 0, context);
			if (error == ENOATTR) {
				error = 0;
			}
			return error;
		}
	}

	if (strncmp(name, XATTR_RESOURCEFORK_NAME, sizeof(XATTR_RESOURCEFORK_NAME)) == 0) {
		/*
		 * For ResourceFork we allow offset to be != 0, so adjust datalen accordingly
		 * so doubleagent will adjust the file length accordingly
		 *
		 */
		if (__improbable(os_add_overflow(datalen, uio_offset(uio), &datalen))) {
			return EINVAL;
		}

		if (datalen > UINT32_MAX) {
			return EINVAL;
		}
	}

	/*
	 * Open the file locked since setting an attribute
	 * can change the layout of the Apple Double file.
	 */
	fileflags = FREAD | FWRITE | O_EXLOCK;
	if ((error = open_xattrfile(vp, O_CREAT | fileflags, &xfg,
	    &fsize, context))) {
		goto out;
	}
	xvp = fg_get_data(xfg);
	if ((error = make_xattrfile_port(xfg, &fileport))) {
		goto out;
	}

	/* Drop the iocount before upcalling to doubleagentd. */
	vnode_put(xvp);
	have_iocount = false;

	strncpy(cName, name, XATTR_MAXNAMELEN);

	/*
	 * Call doubleagentd to allocate space for the xattr.  The
	 * fileport argument is declared move-send, so the Mig stub
	 * consumes it.
	 */
	kr = doubleagent_allocate_xattr(doubleagentd_port, fileport, fsize,
	    cName, datalen, options, &error, &value_offset);
	if (kr != KERN_SUCCESS) {
		error = EIO;
	}
	if (error == 0) {
		error = vnode_getwithref(xvp);
	}
	if (error) {
		goto out;
	}
	have_iocount = true;

	/*
	 * write the uio data into the offset we got from doubleagent,
	 * while adding the given uio offset (could be non-zero only for
	 * resource fork; it is being checked earlier).
	 */
	uio_setoffset(uio, uio_offset(uio) + value_offset);
	error = VNOP_WRITE(xvp, uio, 0, context);
	uio_setoffset(uio, 0);

out:
	if (xfg != NULL) {
		close_xattrfile(xfg, have_iocount, true, context);
	}

	/* Touch the change time if we changed an attribute. */
	if (error == 0) {
		struct vnode_attr va;

		/* Re-write the mtime to cause a ctime change. */
		VATTR_INIT(&va);
		VATTR_WANTED(&va, va_modify_time);
		if (vnode_getattr(vp, &va, context) == 0) {
			VATTR_INIT(&va);
			VATTR_SET(&va, va_modify_time, va.va_modify_time);
			(void) vnode_setattr(vp, &va, context);
		}
	}

	post_event_if_success(vp, error, NOTE_ATTRIB);

	return error;
}

/*
 * Remove an extended attribute.
 * (Using DoubleAgent to parse the AD file).
 */
static int
default_removexattr_doubleagent(vnode_t vp, const char *name,
    __unused int options, vfs_context_t context,
    mach_port_t doubleagentd_port)
{
	vnode_t xvp = NULL;
	struct fileglob *xfg = NULL;
	int isrsrcfork;
	int fileflags;
	int error;
	int64_t fsize;
	boolean_t is_empty = false;
	char cName[XATTR_MAXNAMELEN] = {0};
	mach_port_t fileport = MACH_PORT_NULL;
	kern_return_t kr;
	bool have_iocount = true;

	fileflags = FREAD | FWRITE | O_EXLOCK;
	isrsrcfork = strncmp(name, XATTR_RESOURCEFORK_NAME,
	    sizeof(XATTR_RESOURCEFORK_NAME)) == 0;

	if ((error = open_xattrfile(vp, fileflags, &xfg, &fsize, context))) {
		goto out;
	}
	xvp = fg_get_data(xfg);
	if ((error = make_xattrfile_port(xfg, &fileport))) {
		goto out;
	}

	/* Drop the iocount before upcalling to doubleagentd. */
	vnode_put(xvp);
	have_iocount = false;

	strncpy(cName, name, XATTR_MAXNAMELEN);

	/*
	 * Call doubleagentd to remove the xattr.  The fileport argument
	 * is declared move-send, so the Mig stub consumes it.
	 */
	kr = doubleagent_remove_xattr(doubleagentd_port, fileport, fsize, cName,
	    &error, &is_empty);
	if (kr != KERN_SUCCESS) {
		error = EIO;
	}
	if (error == 0) {
		error = vnode_getwithref(xvp);
	}
	if (error) {
		goto out;
	}
	have_iocount = true;

out:
	if (error == 0) {
		/* When there are no more attributes remove the ._ file. */
		if (is_empty) {
			remove_xattrfile(xfg, xvp, context);
		} else {
			close_xattrfile(xfg, have_iocount, true, context);
		}
		xfg = NULL;

		/* Touch the change time if we changed an attribute. */
		struct vnode_attr va;
		/* Re-write the mtime to cause a ctime change. */
		VATTR_INIT(&va);
		VATTR_WANTED(&va, va_modify_time);
		if (vnode_getattr(vp, &va, context) == 0) {
			VATTR_INIT(&va);
			VATTR_SET(&va, va_modify_time, va.va_modify_time);
			(void) vnode_setattr(vp, &va, context);
		}
	}

	post_event_if_success(vp, error, NOTE_ATTRIB);

	if (xfg != NULL) {
		close_xattrfile(xfg, have_iocount, true, context);
	}
	return error;
}

static int
open_xattrfile(vnode_t vp, int fileflags, struct fileglob **xfgp,
    int64_t *file_sizep, vfs_context_t context)
{
	extern const struct fileops vnops;      /* XXX */
	vnode_t xvp = NULLVP;
	vnode_t dvp = NULLVP;
	struct fileglob *fg = NULL;
	struct vnode_attr *va = NULL;
	struct nameidata *nd = NULL;
	char smallname[64];
	char *filename = NULL;
	const char *basename = NULL;
	size_t alloc_len = 0;
	size_t copy_len;
	errno_t error;
	int opened = 0;
	int referenced = 0;
	bool created_xattr_file = false;

	if (vnode_isvroot(vp) && vnode_isdir(vp)) {
		/*
		 * For the root directory use "._." to hold the attributes.
		 */
		filename = &smallname[0];
		snprintf(filename, sizeof(smallname), "%s%s", ATTR_FILE_PREFIX, ".");
		dvp = vp;  /* the "._." file resides in the root dir */
		goto lookup;
	}
	if ((dvp = vnode_getparent(vp)) == NULLVP) {
		error = ENOATTR;
		goto out;
	}
	if ((basename = vnode_getname(vp)) == NULL) {
		error = ENOATTR;
		goto out;
	}

	/* "._" Attribute files cannot have attributes */
	if (vp->v_type == VREG && strlen(basename) > 2 &&
	    basename[0] == '.' && basename[1] == '_') {
		error = EPERM;
		goto out;
	}
	filename = &smallname[0];
	alloc_len = snprintf(filename, sizeof(smallname), "%s%s", ATTR_FILE_PREFIX, basename);
	if (alloc_len >= sizeof(smallname)) {
		alloc_len++;  /* snprintf result doesn't include '\0' */
		filename = kalloc_data(alloc_len, Z_WAITOK);
		copy_len = snprintf(filename, alloc_len, "%s%s", ATTR_FILE_PREFIX, basename);
	}
	/*
	 * Note that the lookup here does not authorize.  Since we are looking
	 * up in the same directory that we already have the file vnode in,
	 * we must have been given the file vnode legitimately.  Read/write
	 * access has already been authorized in layers above for calls from
	 * userspace, and the authorization code using this path to read
	 * file security from the EA must always get access
	 */
lookup:
	nd = kalloc_type(struct nameidata, Z_WAITOK);
	NDINIT(nd, LOOKUP, OP_OPEN, LOCKLEAF | NOFOLLOW | USEDVP | DONOTAUTH,
	    UIO_SYSSPACE, CAST_USER_ADDR_T(filename), context);
	nd->ni_dvp = dvp;

	va = kalloc_type(struct vnode_attr, Z_WAITOK);

	if (fileflags & O_CREAT) {
		nd->ni_cnd.cn_nameiop = CREATE;
#if CONFIG_TRIGGERS
		nd->ni_op = OP_LINK;
#endif
		if (dvp != vp) {
			nd->ni_cnd.cn_flags |= LOCKPARENT;
		}
		if ((error = namei(nd))) {
			nd->ni_dvp = NULLVP;
			error = ENOATTR;
			goto out;
		}
		if ((xvp = nd->ni_vp) == NULLVP) {
			uid_t uid;
			gid_t gid;
			mode_t umode;

			/*
			 * Pick up uid/gid/mode from target file.
			 */
			VATTR_INIT(va);
			VATTR_WANTED(va, va_uid);
			VATTR_WANTED(va, va_gid);
			VATTR_WANTED(va, va_mode);
			if (VNOP_GETATTR(vp, va, context) == 0 &&
			    VATTR_IS_SUPPORTED(va, va_uid) &&
			    VATTR_IS_SUPPORTED(va, va_gid) &&
			    VATTR_IS_SUPPORTED(va, va_mode)) {
				uid = va->va_uid;
				gid = va->va_gid;
				umode = va->va_mode & (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
			} else { /* fallback values */
				uid = KAUTH_UID_NONE;
				gid = KAUTH_GID_NONE;
				umode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
			}

			VATTR_INIT(va);
			VATTR_SET(va, va_type, VREG);
			VATTR_SET(va, va_mode, umode);
			if (uid != KAUTH_UID_NONE) {
				VATTR_SET(va, va_uid, uid);
			}
			if (gid != KAUTH_GID_NONE) {
				VATTR_SET(va, va_gid, gid);
			}

			error = vn_create(dvp, &nd->ni_vp, nd, va,
			    VN_CREATE_NOAUTH | VN_CREATE_NOINHERIT | VN_CREATE_NOLABEL,
			    0, NULL,
			    context);
			if (error) {
				error = ENOATTR;
			} else {
				xvp = nd->ni_vp;
				created_xattr_file = true;
			}
		}
		nameidone(nd);
		if (dvp != vp) {
			vnode_put(dvp);  /* drop iocount from LOCKPARENT request above */
		}
		if (error) {
			goto out;
		}
	} else {
		if ((error = namei(nd))) {
			nd->ni_dvp = NULLVP;
			error = ENOATTR;
			goto out;
		}
		xvp = nd->ni_vp;
		nameidone(nd);
	}
	nd->ni_dvp = NULLVP;

	if (xvp->v_type != VREG) {
		error = ENOATTR;
		goto out;
	}
	/*
	 * Owners must match.
	 */
	VATTR_INIT(va);
	VATTR_WANTED(va, va_uid);
	if (VNOP_GETATTR(vp, va, context) == 0 && VATTR_IS_SUPPORTED(va, va_uid)) {
		uid_t owner = va->va_uid;

		VATTR_INIT(va);
		VATTR_WANTED(va, va_uid);
		if (VNOP_GETATTR(xvp, va, context) == 0 && (owner != va->va_uid)) {
			error = ENOATTR;  /* don't use this "._" file */
			goto out;
		}
	}

	if ((error = VNOP_OPEN(xvp, fileflags & ~(O_EXLOCK | O_SHLOCK), context))) {
		error = ENOATTR;
		goto out;
	}
	opened = 1;

	if ((error = vnode_ref_ext(xvp, fileflags, 0)) != 0) {
		goto out;
	}
	referenced = 1;

	/*
	 * If create was requested, make sure file header exists.
	 * This is only done in the non-DoubleAgent case.
	 * XXX And will be garbage-collected in due time.
	 */
	if (!vfs_xattr_doubleagent_enabled && (fileflags & O_CREAT) != 0) {
		VATTR_INIT(va);
		VATTR_WANTED(va, va_data_size);
		VATTR_WANTED(va, va_fileid);
		VATTR_WANTED(va, va_nlink);
		if ((error = vnode_getattr(xvp, va, context)) != 0) {
			error = EPERM;
			goto out;
		}

		/* If the file is empty then add a default header. */
		if (va->va_data_size == 0) {
			/* Don't adopt hard-linked "._" files. */
			if (VATTR_IS_SUPPORTED(va, va_nlink) && va->va_nlink > 1) {
				error = EPERM;
				goto out;
			}
			if ((error = create_xattrfile(xvp, (u_int32_t)va->va_fileid, context))) {
				goto out;
			}
		}
	}

	/*
	 * Allocate a file object for the referenced vnode.
	 * This file object now owns the vnode reference,
	 * and the caller owns the iocount, which will be
	 * dropped in close_xattrfile().
	 */
	fg = fg_alloc_init(context);
	fg->fg_flag = fileflags & FMASK;
	fg->fg_ops = &vnops;
	fg_set_data(fg, xvp);

	/* Apply file locking if requested. */
	if (fileflags & (O_EXLOCK | O_SHLOCK)) {
		struct flock lf = {
			.l_whence = SEEK_SET,
		};

		if (fileflags & O_EXLOCK) {
			lf.l_type = F_WRLCK;
		} else {
			lf.l_type = F_RDLCK;
		}
		error = VNOP_ADVLOCK(xvp, (caddr_t)fg, F_SETLK, &lf, F_FLOCK | F_WAIT, context, NULL);
		if (error == ENOTSUP) {
			error = 0;
		} else if (error) {
			error = ENOATTR;
			goto out;
		} else { // error == 0
			fg->fg_flag |= FWASLOCKED;
		}
	}

	if (file_sizep != NULL) {
		/*
		 * Now that the file is locked, get the file's size.
		 */
		VATTR_INIT(va);
		VATTR_WANTED(va, va_data_size);
		if ((error = vnode_getattr(xvp, va, context)) != 0) {
			error = ENOATTR;
			goto out;
		}
		*file_sizep = va->va_data_size;
	}
out:
	if (error) {
		if (fg != NULL) {
			/* Let the normal close path handle this. */
			if (created_xattr_file) {
				remove_xattrfile(fg, xvp, context);
			} else {
				close_xattrfile(fg, true, true, context);
			}
			fg = NULL;
			xvp = NULLVP;
		} else if (xvp != NULLVP) {
			if (opened) {
				(void) VNOP_CLOSE(xvp, fileflags, context);
			}
			if (created_xattr_file) {
				remove_xattrfile(NULL, xvp, context);
			}
			if (referenced) {
				(void) vnode_rele(xvp);
			}
			/* remove_xattrfile() would have dropped the iocount already */
			if (!created_xattr_file) {
				(void) vnode_put(xvp);
			}
			xvp = NULLVP;
		}
		if ((error == ENOATTR) && (fileflags & O_CREAT)) {
			error = EPERM;
		}
	}

	/* Release resources after error-handling */
	kfree_type(struct nameidata, nd);
	kfree_type(struct vnode_attr, va);
	if (dvp && (dvp != vp)) {
		vnode_put(dvp);
	}
	if (basename) {
		vnode_putname(basename);
	}
	if (filename && filename != &smallname[0]) {
		kfree_data(filename, alloc_len);
	}

	*xfgp = fg;
	return error;
}

static void
close_xattrfile(struct fileglob *xfg, bool have_iocount, bool drop_iocount,
    vfs_context_t context)
{
	vnode_t xvp = fg_get_data(xfg);

	/*
	 * N.B. The only time have_iocount would be false would be when
	 * a vnode_getwithref() calls fails after coming back from a
	 * doubleagentd upcall.  If that happens, then it would mean
	 * that the old vnode identity is gone, and our advisory lock
	 * would have been garbage-collected when the vnode was reclaimed.
	 */
	if (have_iocount) {
		/*
		 * fg_drop() won't drop our advisory lock because we are not
		 * following POSIX semantics.  Drop it here.
		 */
		struct flock lf = {
			.l_whence = SEEK_SET,
			.l_type = F_UNLCK,
		};
		(void)VNOP_ADVLOCK(xvp, (caddr_t)xfg, F_UNLCK, &lf, F_FLOCK,
		    context, NULL);

		/* (Maybe) drop the iocount we took in open_xattrfile(). */
		if (drop_iocount) {
			vnode_put(xvp);
		}
	}

	(void) fg_drop(current_proc(), xfg);
}

static void
remove_xattrfile(struct fileglob *xfg, vnode_t xvp, vfs_context_t context)
{
	vnode_t dvp = NULL, rvp = NULL;
	struct nameidata nd;
	char *path = NULL;
	int pathlen;
	int error;

	if (xfg != NULL) {
		/*
		 * Close the xattr file but don't dispose of the
		 * iocount acquired in open_xattrfile() while doing
		 * so.  We'll do that below once we have performed
		 * the unlink operation.
		 */
		close_xattrfile(xfg, true, false, context);
	}

	path = zalloc(ZV_NAMEI);
	pathlen = MAXPATHLEN;
	error = vn_getpath(xvp, path, &pathlen);
	if (error) {
		zfree(ZV_NAMEI, path);
		goto out;
	}

	NDINIT(&nd, DELETE, OP_UNLINK, LOCKPARENT | NOFOLLOW | DONOTAUTH,
	    UIO_SYSSPACE, CAST_USER_ADDR_T(path), context);
	error = namei(&nd);
	zfree(ZV_NAMEI, path);
	if (error) {
		goto out;
	}
	dvp = nd.ni_dvp;
	rvp = nd.ni_vp;

	/*
	 * Only remove if the namei() returned to us the same vnode that
	 * we think we are supposed to be removing.  If they're not the
	 * same, we could have raced against something else trying to
	 * unlink it, and we don't want to remove someone else's (possibly
	 * very important) file.
	 */
	if (rvp == xvp) {
		(void) VNOP_REMOVE(dvp, rvp, &nd.ni_cnd, 0, context);
	}
	nameidone(&nd);

out:
	vnode_put(xvp);
	if (dvp != NULLVP) {
		vnode_put(dvp);
	}
	if (rvp != NULLVP) {
		vnode_put(rvp);
	}
}

/*
 * Read in and parse the AppleDouble header and entries, and the extended
 * attribute header and entries if any.  Populates the fields of ainfop
 * based on the headers and entries found.
 *
 * The basic idea is to:
 * - Read in up to ATTR_MAX_HDR_SIZE bytes of the start of the file.  All
 *   AppleDouble entries, the extended attribute header, and extended
 *   attribute entries must lie within this part of the file; the rest of
 *   the AppleDouble handling code assumes this.  Plus it allows us to
 *   somewhat optimize by doing a smaller number of larger I/Os.
 * - Swap and sanity check the AppleDouble header (including the AppleDouble
 *   entries).
 * - Find the Finder Info and Resource Fork entries, if any.
 * - If we're going to be writing, try to make sure the Finder Info entry has
 *   room to store the extended attribute header, plus some space for extended
 *   attributes.
 * - Swap and sanity check the extended attribute header and entries (if any).
 */
static int
get_xattrinfo(vnode_t xvp, int setting, attr_info_t *ainfop, vfs_context_t context)
{
	uio_t auio = NULL;
	void * buffer = NULL;
	apple_double_header_t  *filehdr;
	struct vnode_attr va;
	size_t iosize = 0;
	int i;
	int error;

	bzero(ainfop, sizeof(attr_info_t));
	ainfop->filevp = xvp;
	ainfop->context = context;
	VATTR_INIT(&va);
	VATTR_WANTED(&va, va_data_size);
	VATTR_WANTED(&va, va_fileid);
	if ((error = vnode_getattr(xvp, &va, context))) {
		goto bail;
	}
	ainfop->filesize = va.va_data_size;

	/* When setting attributes, allow room for the header to grow. */
	if (setting) {
		iosize = ATTR_MAX_HDR_SIZE;
	} else {
		iosize = MIN(ATTR_MAX_HDR_SIZE, ainfop->filesize);
	}

	if (iosize == 0 || iosize < sizeof(apple_double_header_t)) {
		error = ENOATTR;
		goto bail;
	}

	ainfop->iosize = iosize;
	buffer = kalloc_data(iosize, Z_WAITOK | Z_ZERO);
	if (buffer == NULL) {
		error = ENOMEM;
		goto bail;
	}

	auio = uio_create(1, 0, UIO_SYSSPACE, UIO_READ);
	uio_addiov(auio, (uintptr_t)buffer, iosize);

	/* Read the file header. */
	error = VNOP_READ(xvp, auio, 0, context);
	if (error) {
		goto bail;
	}
	ainfop->rawsize = iosize - uio_resid(auio);
	ainfop->rawdata = (u_int8_t *)buffer;

	filehdr = (apple_double_header_t *)buffer;

	error = check_and_swap_apple_double_header(ainfop);
	if (error) {
		goto bail;
	}

	ainfop->filehdr = filehdr;  /* valid AppleDouble header */

	/* rel_xattrinfo is responsible for freeing the header buffer */
	buffer = NULL;

	/* Find the Finder Info and Resource Fork entries, if any */
	for (i = 0; i < filehdr->numEntries; ++i) {
		if (filehdr->entries[i].type == AD_FINDERINFO &&
		    filehdr->entries[i].length >= FINDERINFOSIZE) {
			/* We found the Finder Info entry. */
			ainfop->finderinfo = &filehdr->entries[i];

			/* At this point check_and_swap_apple_double_header() call above
			 * verified that all apple double entires are valid:
			 * they point somewhere within the file.
			 *
			 * Now for finderinfo make sure that the fixed portion
			 * is within the buffer we read in.
			 */
			if (((ainfop->finderinfo->offset + FINDERINFOSIZE) > ainfop->finderinfo->offset) &&
			    ((ainfop->finderinfo->offset + FINDERINFOSIZE) <= ainfop->rawsize)) {
				/*
				 * Is the Finder Info "empty" (all zeroes)?  If so,
				 * we'll pretend like the Finder Info extended attribute
				 * does not exist.
				 */
				if (bcmp((u_int8_t*)ainfop->filehdr + ainfop->finderinfo->offset, emptyfinfo, sizeof(emptyfinfo)) == 0) {
					ainfop->emptyfinderinfo = 1;
				}
			} else {
				error = ENOATTR;
				goto bail;
			}
		}
		if (filehdr->entries[i].type == AD_RESOURCE) {
			/*
			 * Ignore zero-length resource forks when getting.  If setting,
			 * we need to remember the resource fork entry so it can be
			 * updated once the new content has been written.
			 */
			if (filehdr->entries[i].length == 0 && !setting) {
				continue;
			}

			/*
			 * Check to see if any "empty" resource fork is ours (i.e. is ignorable).
			 *
			 * The "empty" resource headers we created have a system data tag of:
			 * "This resource fork intentionally left blank   "
			 */
			if (filehdr->entries[i].length == sizeof(rsrcfork_header_t) && !setting) {
				uio_t  rf_uio;
				u_int8_t  systemData[64];
				int  rf_err;


				/* Read the system data which starts at byte 16 */
				rf_uio = uio_create(1, 0, UIO_SYSSPACE, UIO_READ);
				uio_addiov(rf_uio, (uintptr_t)systemData, sizeof(systemData));
				uio_setoffset(rf_uio, filehdr->entries[i].offset + 16);
				rf_err = VNOP_READ(xvp, rf_uio, 0, context);
				uio_free(rf_uio);

				if (rf_err != 0 ||
				    bcmp(systemData, RF_EMPTY_TAG, sizeof(RF_EMPTY_TAG)) == 0) {
					continue;  /* skip this resource fork */
				}
			}
			ainfop->rsrcfork = &filehdr->entries[i];
			if (i != (filehdr->numEntries - 1)) {
				printf("get_xattrinfo: resource fork not last entry\n");
				ainfop->readonly = 1;
			}
			continue;
		}
	}

	/*
	 * See if this file looks like it is laid out correctly to contain
	 * extended attributes.  If so, then do the following:
	 *
	 * - If we're going to be writing, try to make sure the Finder Info
	 *   entry has room to store the extended attribute header, plus some
	 *   space for extended attributes.
	 *
	 * - Swap and sanity check the extended attribute header and entries
	 *   (if any).
	 */
	if (filehdr->numEntries == 2 &&
	    ainfop->finderinfo == &filehdr->entries[0] &&
	    ainfop->rsrcfork == &filehdr->entries[1] &&
	    ainfop->finderinfo->offset == offsetof(apple_double_header_t, finfo)) {
		attr_header_t *attrhdr;
		attrhdr = (attr_header_t *)filehdr;
		/*
		 * If we're going to be writing, try to make sure the Finder
		 * Info entry has room to store the extended attribute header,
		 * plus some space for extended attributes.
		 */
		if (setting && ainfop->finderinfo->length == FINDERINFOSIZE) {
			size_t delta;
			size_t writesize;

			delta = ATTR_BUF_SIZE - (filehdr->entries[0].offset + FINDERINFOSIZE);
			if (ainfop->rsrcfork && filehdr->entries[1].length) {
				/* Make some room before existing resource fork. */
				shift_data_down(xvp,
				    filehdr->entries[1].offset,
				    filehdr->entries[1].length,
				    delta, context);
				writesize = sizeof(attr_header_t);
			} else {
				/* We are in case where existing resource fork of length 0, try to create a new, empty resource fork. */
				rsrcfork_header_t *rsrcforkhdr;

				/* Do we have enough space in the header buffer for empty resource fork */
				if (filehdr->entries[1].offset + delta + sizeof(rsrcfork_header_t) > ainfop->iosize) {
					/* we do not have space, bail for now */
					error = ENOATTR;
					goto bail;
				}

				vnode_setsize(xvp, filehdr->entries[1].offset + delta, 0, context);

				/* Steal some space for an empty RF header. */
				delta -= sizeof(rsrcfork_header_t);

				bzero(&attrhdr->appledouble.pad[0], delta);
				rsrcforkhdr = (rsrcfork_header_t *)((char *)filehdr + filehdr->entries[1].offset + delta);

				/* Fill in Empty Resource Fork Header. */
				init_empty_resource_fork(rsrcforkhdr);

				filehdr->entries[1].length = sizeof(rsrcfork_header_t);
				writesize = ATTR_BUF_SIZE;
			}
			filehdr->entries[0].length += delta;
			filehdr->entries[1].offset += delta;

			/* Fill in Attribute Header. */
			attrhdr->magic       = ATTR_HDR_MAGIC;
			attrhdr->debug_tag   = (u_int32_t)va.va_fileid;
			attrhdr->total_size  = filehdr->entries[1].offset;
			attrhdr->data_start  = sizeof(attr_header_t);
			attrhdr->data_length = 0;
			attrhdr->reserved[0] = 0;
			attrhdr->reserved[1] = 0;
			attrhdr->reserved[2] = 0;
			attrhdr->flags       = 0;
			attrhdr->num_attrs   = 0;

			/* Push out new header */
			uio_reset(auio, 0, UIO_SYSSPACE, UIO_WRITE);
			uio_addiov(auio, (uintptr_t)filehdr, writesize);

			swap_adhdr(filehdr);    /* to big endian */
			swap_attrhdr(attrhdr, ainfop);  /* to big endian */
			error = VNOP_WRITE(xvp, auio, 0, context);
			swap_adhdr(filehdr);    /* back to native */
			/* The attribute header gets swapped below. */
		}
	}
	/*
	 * Swap and sanity check the extended attribute header and
	 * entries (if any).  The Finder Info content must be big enough
	 * to include the extended attribute header; if not, we just
	 * ignore it.
	 *
	 * Note that we're passing the offset + length (i.e. the end)
	 * of the Finder Info instead of rawsize to validate_attrhdr.
	 * This ensures that all extended attributes lie within the
	 * Finder Info content according to the AppleDouble entry.
	 *
	 * Sets ainfop->attrhdr and ainfop->attr_entry if a valid
	 * header was found.
	 */
	if (ainfop->finderinfo &&
	    ainfop->finderinfo == &filehdr->entries[0] &&
	    ainfop->finderinfo->length >= (sizeof(attr_header_t) - sizeof(apple_double_header_t))) {
		attr_header_t *attrhdr = (attr_header_t*)filehdr;

		if (ainfop->finderinfo->offset != offsetof(apple_double_header_t, finfo)) {
			error = ENOATTR;
			goto bail;
		}

		if ((error = check_and_swap_attrhdr(attrhdr, ainfop)) == 0) {
			ainfop->attrhdr = attrhdr;  /* valid attribute header */
			/* First attr_entry starts immediately following attribute header */
			ainfop->attr_entry = (attr_entry_t *)&attrhdr[1];
		}
	}

	error = 0;
bail:
	if (auio != NULL) {
		uio_free(auio);
	}
	kfree_data(buffer, iosize);
	return error;
}


static int
create_xattrfile(vnode_t xvp, u_int32_t fileid, vfs_context_t context)
{
	attr_header_t *xah;
	rsrcfork_header_t *rsrcforkhdr;
	void * buffer;
	uio_t auio;
	int rsrcforksize;
	int error;

	buffer = kalloc_data(ATTR_BUF_SIZE, Z_WAITOK | Z_ZERO);

	xah = (attr_header_t *)buffer;
	auio = uio_create(1, 0, UIO_SYSSPACE, UIO_WRITE);
	uio_addiov(auio, (uintptr_t)buffer, ATTR_BUF_SIZE);
	rsrcforksize = sizeof(rsrcfork_header_t);
	rsrcforkhdr = (rsrcfork_header_t *) ((char *)buffer + ATTR_BUF_SIZE - rsrcforksize);

	/* Fill in Apple Double Header. */
	xah->appledouble.magic             = SWAP32(ADH_MAGIC);
	xah->appledouble.version           = SWAP32(ADH_VERSION);
	xah->appledouble.numEntries        = SWAP16(2);
	xah->appledouble.entries[0].type   = SWAP32(AD_FINDERINFO);
	xah->appledouble.entries[0].offset = SWAP32(offsetof(apple_double_header_t, finfo));
	xah->appledouble.entries[0].length = SWAP32(ATTR_BUF_SIZE - offsetof(apple_double_header_t, finfo) - rsrcforksize);
	xah->appledouble.entries[1].type   = SWAP32(AD_RESOURCE);
	xah->appledouble.entries[1].offset = SWAP32(ATTR_BUF_SIZE - rsrcforksize);
	xah->appledouble.entries[1].length = SWAP32(rsrcforksize);
	bcopy(ADH_MACOSX, xah->appledouble.filler, sizeof(xah->appledouble.filler));

	/* Fill in Attribute Header. */
	xah->magic       = SWAP32(ATTR_HDR_MAGIC);
	xah->debug_tag   = SWAP32(fileid);
	xah->total_size  = SWAP32(ATTR_BUF_SIZE - rsrcforksize);
	xah->data_start  = SWAP32(sizeof(attr_header_t));

	/* Fill in Empty Resource Fork Header. */
	init_empty_resource_fork(rsrcforkhdr);

	/* Push it out. */
	error = VNOP_WRITE(xvp, auio, IO_UNIT, context);

	/* Did we write out the full uio? */
	if (uio_resid(auio) > 0) {
		error = ENOSPC;
	}

	uio_free(auio);
	kfree_data(buffer, ATTR_BUF_SIZE);

	return error;
}

static void
init_empty_resource_fork(rsrcfork_header_t * rsrcforkhdr)
{
	bzero(rsrcforkhdr, sizeof(rsrcfork_header_t));
	rsrcforkhdr->fh_DataOffset = SWAP32(RF_FIRST_RESOURCE);
	rsrcforkhdr->fh_MapOffset  = SWAP32(RF_FIRST_RESOURCE);
	rsrcforkhdr->fh_MapLength  = SWAP32(RF_NULL_MAP_LENGTH);
	rsrcforkhdr->mh_DataOffset = SWAP32(RF_FIRST_RESOURCE);
	rsrcforkhdr->mh_MapOffset  = SWAP32(RF_FIRST_RESOURCE);
	rsrcforkhdr->mh_MapLength  = SWAP32(RF_NULL_MAP_LENGTH);
	rsrcforkhdr->mh_Types      = SWAP16(RF_NULL_MAP_LENGTH - 2 );
	rsrcforkhdr->mh_Names      = SWAP16(RF_NULL_MAP_LENGTH);
	rsrcforkhdr->typeCount     = SWAP16(-1);
	bcopy(RF_EMPTY_TAG, rsrcforkhdr->systemData, sizeof(RF_EMPTY_TAG));
}

static void
rel_xattrinfo(attr_info_t *ainfop)
{
	kfree_data_addr(ainfop->filehdr);
	bzero(ainfop, sizeof(attr_info_t));
}

static int
write_xattrinfo(attr_info_t *ainfop)
{
	uio_t auio;
	int error;

	auio = uio_create(1, 0, UIO_SYSSPACE, UIO_WRITE);
	uio_addiov(auio, (uintptr_t)ainfop->filehdr, ainfop->iosize);

	swap_adhdr(ainfop->filehdr);
	if (ainfop->attrhdr != NULL) {
		swap_attrhdr(ainfop->attrhdr, ainfop);
	}

	error = VNOP_WRITE(ainfop->filevp, auio, 0, ainfop->context);

	swap_adhdr(ainfop->filehdr);
	if (ainfop->attrhdr != NULL) {
		swap_attrhdr(ainfop->attrhdr, ainfop);
	}
	uio_free(auio);

	return error;
}

#if BYTE_ORDER == LITTLE_ENDIAN
/*
 * Endian swap apple double header
 */
static void
swap_adhdr(apple_double_header_t *adh)
{
	int count;
	int i;

	count = (adh->magic == ADH_MAGIC) ? adh->numEntries : SWAP16(adh->numEntries);

	adh->magic      = SWAP32(adh->magic);
	adh->version    = SWAP32(adh->version);
	adh->numEntries = SWAP16(adh->numEntries);

	for (i = 0; i < count; i++) {
		adh->entries[i].type   = SWAP32(adh->entries[i].type);
		adh->entries[i].offset = SWAP32(adh->entries[i].offset);
		adh->entries[i].length = SWAP32(adh->entries[i].length);
	}
}

/*
 * Endian swap extended attributes header
 */
static void
swap_attrhdr(attr_header_t *ah, attr_info_t* info)
{
	attr_entry_t *ae;
	int count;
	int i;

	count = (ah->magic == ATTR_HDR_MAGIC) ? ah->num_attrs : SWAP16(ah->num_attrs);

	ah->magic       = SWAP32(ah->magic);
	ah->debug_tag   = SWAP32(ah->debug_tag);
	ah->total_size  = SWAP32(ah->total_size);
	ah->data_start  = SWAP32(ah->data_start);
	ah->data_length = SWAP32(ah->data_length);
	ah->flags       = SWAP16(ah->flags);
	ah->num_attrs   = SWAP16(ah->num_attrs);

	ae = (attr_entry_t *)(&ah[1]);
	for (i = 0; i < count && ATTR_VALID(ae, *info); i++, ae = ATTR_NEXT(ae)) {
		ae->offset = SWAP32(ae->offset);
		ae->length = SWAP32(ae->length);
		ae->flags  = SWAP16(ae->flags);
	}
}
#endif

/*
 * Validate and swap the attributes header contents, and each attribute's
 * attr_entry_t.
 *
 * Note: Assumes the caller has verified that the Finder Info content is large
 * enough to contain the attr_header structure itself.  Therefore, we can
 * swap the header fields before sanity checking them.
 */
static int
check_and_swap_attrhdr(attr_header_t *ah, attr_info_t *ainfop)
{
	attr_entry_t *ae;
	u_int8_t *buf_end;
	u_int32_t end;
	int count;
	int i;
	uint32_t total_header_size;
	uint32_t total_data_size;

	if (ah == NULL) {
		return EINVAL;
	}

	if (SWAP32(ah->magic) != ATTR_HDR_MAGIC) {
		return EINVAL;
	}

	/* Swap the basic header fields */
	ah->magic       = SWAP32(ah->magic);
	ah->debug_tag   = SWAP32(ah->debug_tag);
	ah->total_size  = SWAP32(ah->total_size);
	ah->data_start  = SWAP32(ah->data_start);
	ah->data_length = SWAP32(ah->data_length);
	ah->flags       = SWAP16(ah->flags);
	ah->num_attrs   = SWAP16(ah->num_attrs);

	/*
	 * Make sure the total_size fits within the Finder Info area, and the
	 * extended attribute data area fits within total_size.
	 */
	end = ah->data_start + ah->data_length;
	if (ah->total_size > ainfop->finderinfo->offset + ainfop->finderinfo->length ||
	    ah->data_start < sizeof(attr_header_t) ||
	    end < ah->data_start ||
	    end > ah->total_size) {
		return EINVAL;
	}

	/*
	 * Make sure each of the attr_entry_t's fits within total_size.
	 */
	buf_end = ainfop->rawdata + ah->data_start;
	if (buf_end > ainfop->rawdata + ainfop->rawsize) {
		return EINVAL;
	}
	count = ah->num_attrs;
	if (count > 256) {
		return EINVAL;
	}
	ae = (attr_entry_t *)(&ah[1]);

	total_header_size = sizeof(attr_header_t);
	total_data_size = 0;
	for (i = 0; i < count; i++) {
		/* Make sure the fixed-size part of this attr_entry_t fits. */
		if ((u_int8_t *) &ae[1] > buf_end) {
			return EINVAL;
		}

		/* Make sure the variable-length name fits */
		if (&ae->name[ae->namelen] > buf_end) {
			return EINVAL;
		}

		/* Make sure that namelen is matching name's real length, namelen included NUL */
		if (strnlen((const char *)ae->name, ae->namelen) != ae->namelen - 1) {
			return EINVAL;
		}

		/* Swap the attribute entry fields */
		ae->offset      = SWAP32(ae->offset);
		ae->length      = SWAP32(ae->length);
		ae->flags       = SWAP16(ae->flags);

		/* Make sure the attribute content fits and points to the data part */
		end = ae->offset + ae->length;
		if (end < ae->offset || end > ah->total_size) {
			return EINVAL;
		}

		/* Make sure entry points to data section and not header */
		if (ae->offset < ah->data_start || end > ah->data_start + ah->data_length) {
			return EINVAL;
		}

		/* We verified namelen is ok above, so add this entry's size to a total */
		if (os_add_overflow(total_header_size, ATTR_ENTRY_LENGTH(ae->namelen), &total_header_size)) {
			return EINVAL;
		}

		/* We verified that entry's length is within data section, so add it to running size total */
		if (os_add_overflow(total_data_size, ae->length, &total_data_size)) {
			return EINVAL;
		}

		ae = ATTR_NEXT(ae);
	}


	/* make sure data_start is actually after all the xattr key entries */
	if (ah->data_start < total_header_size) {
		return EINVAL;
	}

	/* make sure all entries' data  length add to header's idea of data length */
	if (total_data_size != ah->data_length) {
		return EINVAL;
	}

	return 0;
}

//
// "start" & "end" are byte offsets in the file.
// "to" is the byte offset we want to move the
// data to.  "to" should be > "start".
//
// we do the copy backwards to avoid problems if
// there's an overlap.
//
static int
shift_data_down(vnode_t xvp, off_t start, size_t len, off_t delta, vfs_context_t context)
{
	int ret, iolen;
	size_t chunk, orig_chunk;
	char *buff;
	off_t pos;
	kauth_cred_t ucred = vfs_context_ucred(context);
	proc_t p = vfs_context_proc(context);

	if (delta == 0 || len == 0) {
		return 0;
	}

	chunk = 4096;
	if (len < chunk) {
		chunk = len;
	}
	orig_chunk = chunk;

	buff = kalloc_data(chunk, Z_WAITOK);
	if (buff == NULL) {
		return ENOMEM;
	}

	for (pos = start + len - chunk; pos >= start; pos -= chunk) {
		ret = vn_rdwr(UIO_READ, xvp, buff, (int)chunk, pos, UIO_SYSSPACE, IO_NODELOCKED | IO_NOAUTH, ucred, &iolen, p);
		if (iolen != 0) {
			printf("xattr:shift_data: error reading data @ %lld (read %d of %lu) (%d)\n",
			    pos, ret, chunk, ret);
			break;
		}

		ret = vn_rdwr(UIO_WRITE, xvp, buff, (int)chunk, pos + delta, UIO_SYSSPACE, IO_NODELOCKED | IO_NOAUTH, ucred, &iolen, p);
		if (iolen != 0) {
			printf("xattr:shift_data: error writing data @ %lld (wrote %d of %lu) (%d)\n",
			    pos + delta, ret, chunk, ret);
			break;
		}

		if ((pos - (off_t)chunk) < start) {
			chunk = pos - start;

			if (chunk == 0) {   // we're all done
				break;
			}
		}
	}

	kfree_data(buff, orig_chunk);
	return 0;
}


static int
shift_data_up(vnode_t xvp, off_t start, size_t len, off_t delta, vfs_context_t context)
{
	int ret, iolen;
	size_t chunk, orig_chunk;
	char *buff;
	off_t pos;
	off_t end;
	kauth_cred_t ucred = vfs_context_ucred(context);
	proc_t p = vfs_context_proc(context);

	if (delta == 0 || len == 0) {
		return 0;
	}

	chunk = 4096;
	if (len < chunk) {
		chunk = len;
	}
	orig_chunk = chunk;
	end = start + len;

	buff = kalloc_data(chunk, Z_WAITOK);
	if (buff == NULL) {
		return ENOMEM;
	}

	for (pos = start; pos < end; pos += chunk) {
		ret = vn_rdwr(UIO_READ, xvp, buff, (int)chunk, pos, UIO_SYSSPACE, IO_NODELOCKED | IO_NOAUTH, ucred, &iolen, p);
		if (iolen != 0) {
			printf("xattr:shift_data: error reading data @ %lld (read %d of %lu) (%d)\n",
			    pos, ret, chunk, ret);
			break;
		}

		ret = vn_rdwr(UIO_WRITE, xvp, buff, (int)chunk, pos - delta, UIO_SYSSPACE, IO_NODELOCKED | IO_NOAUTH, ucred, &iolen, p);
		if (iolen != 0) {
			printf("xattr:shift_data: error writing data @ %lld (wrote %d of %lu) (%d)\n",
			    pos + delta, ret, chunk, ret);
			break;
		}

		if ((pos + (off_t)chunk) > end) {
			chunk = end - pos;

			if (chunk == 0) {   // we're all done
				break;
			}
		}
	}

	kfree_data(buff, orig_chunk);
	return 0;
}

static int
make_xattrfile_port(struct fileglob *fg, ipc_port_t *portp)
{
	/*
	 * This is essentially a stripped-down copy of
	 * sys_fileport_makeport().
	 */
	ipc_port_t fileport;
	int error = 0;

	/* Dropped when port is deallocated. */
	fg_ref(FG_NOPROC, fg);

	fileport = fileport_alloc(fg);
	if (fileport == IPC_PORT_NULL) {
		fg_drop_live(fg);
		error = EIO;
	} else {
		/* Tag the fileglob for debugging purposes */
		lck_mtx_lock_spin(&fg->fg_lock);
		fg->fg_lflags |= FG_PORTMADE;
		lck_mtx_unlock(&fg->fg_lock);
	}

	/*
	 * The Mig defs for doubleagentd declare the fileport argument
	 * as move-send.  If we ever decide we want to cache the fileport
	 * here in the kernel, we will either need to change the Mig
	 * defs back to the default mach_port_t (which is a copy-send)
	 * or explicitly ipc_port_copy_send_any() the right before
	 * sending it in the Mig stub.
	 */

	*portp = fileport;
	return error;
}

#else /* CONFIG_APPLEDOUBLE */


static int
default_getxattr(__unused vnode_t vp, __unused const char *name,
    __unused uio_t uio, __unused size_t *size, __unused int options,
    __unused vfs_context_t context)
{
	return ENOTSUP;
}

static int
default_setxattr(__unused vnode_t vp, __unused const char *name,
    __unused uio_t uio, __unused int options, __unused vfs_context_t context)
{
	return ENOTSUP;
}

static int
default_listxattr(__unused vnode_t vp,
    __unused uio_t uio, __unused size_t *size, __unused int options,
    __unused vfs_context_t context)
{
	return ENOTSUP;
}

static int
default_removexattr(__unused vnode_t vp, __unused const char *name,
    __unused int options, __unused vfs_context_t context)
{
	return ENOTSUP;
}

#endif /* CONFIG_APPLEDOUBLE */