zfs/module/zcommon/zfs_uio.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
/*	  All Rights Reserved	*/

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

/*
 * The uio support from OpenSolaris has been added as a short term
 * work around.  The hope is to adopt native Linux type and drop the
 * use of uio's entirely.  Under Linux they only add overhead and
 * when possible we want to use native APIs for the ZPL layer.
 */
#ifdef _KERNEL

#include <sys/types.h>
#include <sys/uio_impl.h>

/*
 * Move "n" bytes at byte address "p"; "rw" indicates the direction
 * of the move, and the I/O parameters are provided in "uio", which is
 * update to reflect the data which was moved.  Returns 0 on success or
 * a non-zero errno on failure.
 */
int
uiomove(void *p, size_t n, enum uio_rw rw, struct uio *uio)
{
	struct iovec *iov;
	ulong_t cnt;

	while (n && uio->uio_resid) {
		iov = uio->uio_iov;
		cnt = MIN(iov->iov_len, n);
		if (cnt == 0l) {
			uio->uio_iov++;
			uio->uio_iovcnt--;
			continue;
		}
		switch (uio->uio_segflg) {
		case UIO_USERSPACE:
		case UIO_USERISPACE:
			/*
			 * p = kernel data pointer
			 * iov->iov_base = user data pointer
			 */
			if (rw == UIO_READ) {
				if (copy_to_user(iov->iov_base, p, cnt))
					return (EFAULT);
			} else {
				if (copy_from_user(p, iov->iov_base, cnt))
					return (EFAULT);
			}
			break;
		case UIO_SYSSPACE:
			if (rw == UIO_READ)
				bcopy(p, iov->iov_base, cnt);
			else
				bcopy(iov->iov_base, p, cnt);
			break;
		}
		iov->iov_base += cnt;
		iov->iov_len -= cnt;
		uio->uio_resid -= cnt;
		uio->uio_loffset += cnt;
		p = (caddr_t)p + cnt;
		n -= cnt;
	}
	return (0);
}
EXPORT_SYMBOL(uiomove);

#define	fuword8(uptr, vptr)	get_user((*vptr), (uptr))

/*
 * Fault in the pages of the first n bytes specified by the uio structure.
 * 1 byte in each page is touched and the uio struct is unmodified. Any
 * error will terminate the process as this is only a best attempt to get
 * the pages resident.
 */
void
uio_prefaultpages(ssize_t n, struct uio *uio)
{
	struct iovec *iov;
	ulong_t cnt, incr;
	caddr_t p;
	uint8_t tmp;
	int iovcnt;

	iov = uio->uio_iov;
	iovcnt = uio->uio_iovcnt;

	while ((n > 0) && (iovcnt > 0)) {
		cnt = MIN(iov->iov_len, n);
		if (cnt == 0) {
			/* empty iov entry */
			iov++;
			iovcnt--;
			continue;
		}
		n -= cnt;
		/*
		 * touch each page in this segment.
		 */
		p = iov->iov_base;
		while (cnt) {
			switch (uio->uio_segflg) {
			case UIO_USERSPACE:
			case UIO_USERISPACE:
				if (fuword8((uint8_t *) p, &tmp))
					return;
				break;
			case UIO_SYSSPACE:
				bcopy(p, &tmp, 1);
				break;
			}
			incr = MIN(cnt, PAGESIZE);
			p += incr;
			cnt -= incr;
		}
		/*
		 * touch the last byte in case it straddles a page.
		 */
		p--;
		switch (uio->uio_segflg) {
		case UIO_USERSPACE:
		case UIO_USERISPACE:
			if (fuword8((uint8_t *) p, &tmp))
				return;
			break;
		case UIO_SYSSPACE:
			bcopy(p, &tmp, 1);
			break;
		}
		iov++;
		iovcnt--;
	}
}
EXPORT_SYMBOL(uio_prefaultpages);

/*
 * same as uiomove() but doesn't modify uio structure.
 * return in cbytes how many bytes were copied.
 */
int
uiocopy(void *p, size_t n, enum uio_rw rw, struct uio *uio, size_t *cbytes)
{
	struct iovec *iov;
	ulong_t cnt;
	int iovcnt;

	iovcnt = uio->uio_iovcnt;
	*cbytes = 0;

	for (iov = uio->uio_iov; n && iovcnt; iov++, iovcnt--) {
		cnt = MIN(iov->iov_len, n);
		if (cnt == 0)
			continue;

		switch (uio->uio_segflg) {

		case UIO_USERSPACE:
		case UIO_USERISPACE:
			/*
			 * p = kernel data pointer
			 * iov->iov_base = user data pointer
			 */
			if (rw == UIO_READ) {
				/* UIO_READ = copy data from kernel to user */
				if (copy_to_user(iov->iov_base, p, cnt))
					return (EFAULT);
			} else {
				/* UIO_WRITE = copy data from user to kernel */
				if (copy_from_user(p, iov->iov_base, cnt))
					return (EFAULT);
			}
			break;

		case UIO_SYSSPACE:
			if (rw == UIO_READ)
				bcopy(p, iov->iov_base, cnt);
			else
				bcopy(iov->iov_base, p, cnt);
			break;
		}
		p = (caddr_t)p + cnt;
		n -= cnt;
		*cbytes += cnt;
	}
	return (0);
}
EXPORT_SYMBOL(uiocopy);

/*
 * Drop the next n chars out of *uiop.
 */
void
uioskip(uio_t *uiop, size_t n)
{
	if (n > uiop->uio_resid)
		return;
	while (n != 0) {
		iovec_t	*iovp = uiop->uio_iov;
		size_t		niovb = MIN(iovp->iov_len, n);

		if (niovb == 0) {
			uiop->uio_iov++;
			uiop->uio_iovcnt--;
			continue;
		}
		iovp->iov_base += niovb;
		uiop->uio_loffset += niovb;
		iovp->iov_len -= niovb;
		uiop->uio_resid -= niovb;
		n -= niovb;
	}
}
EXPORT_SYMBOL(uioskip);
#endif /* _KERNEL */