/*
 * 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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright (c) 2015, Joyent, Inc.  All rights reserved.
 * Copyright 2017 Nexenta Systems, Inc.  All rights reserved.
 */

/*      Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T     */
/*        All Rights Reserved   */

/*
 * Portions of this source code were derived from Berkeley 4.3 BSD
 * under license from the Regents of the University of California.
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/inttypes.h>
#include <sys/sysmacros.h>
#include <sys/cred.h>
#include <sys/user.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/proc.h>
#include <sys/uio.h>
#include <sys/debug.h>

#include <libfksmbfs.h>

#define set_errno(e) (-(e))

ssize_t
fake_pread(vnode_t *vp, void *cbuf, size_t count, off_t offset)
{
        struct uio auio;
        struct iovec aiov;
        int fflag, ioflag, rwflag;
        ssize_t bcount;
        int error = 0;
        u_offset_t fileoff = (u_offset_t)(ulong_t)offset;
        const u_offset_t maxoff = MAXOFF32_T;

        if ((bcount = (ssize_t)count) < 0)
                return (set_errno(EINVAL));
        fflag = FREAD;

        rwflag = 0;

        if (vp->v_type == VREG) {

                if (bcount == 0)
                        goto out;

                /*
                 * Return EINVAL if an invalid offset comes to pread.
                 * Negative offset from user will cause this error.
                 */

                if (fileoff > maxoff) {
                        error = EINVAL;
                        goto out;
                }
                /*
                 * Limit offset such that we don't read or write
                 * a file beyond the maximum offset representable in
                 * an off_t structure.
                 */
                if (fileoff + bcount > maxoff)
                        bcount = (ssize_t)((offset_t)maxoff - fileoff);
        } else if (vp->v_type == VFIFO) {
                error = ESPIPE;
                goto out;
        }

        aiov.iov_base = cbuf;
        aiov.iov_len = bcount;
        (void) VOP_RWLOCK(vp, rwflag, NULL);
        auio.uio_loffset = fileoff;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_resid = bcount;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_llimit = MAXOFFSET_T;
        auio.uio_fmode = fflag;
        auio.uio_extflg = UIO_COPY_CACHED;

        ioflag = auio.uio_fmode & (FAPPEND|FSYNC|FDSYNC|FRSYNC);

        /* If read sync is not asked for, filter sync flags */
        if ((ioflag & FRSYNC) == 0)
                ioflag &= ~(FSYNC|FDSYNC);
        error = VOP_READ(vp, &auio, ioflag, CRED(), NULL);
        bcount -= auio.uio_resid;
        VOP_RWUNLOCK(vp, rwflag, NULL);

        if (error == EINTR && bcount != 0)
                error = 0;
out:
        if (error)
                return (set_errno(error));
        return (bcount);
}

ssize_t
fake_pwrite(vnode_t *vp, void *cbuf, size_t count, off_t offset)
{
        struct uio auio;
        struct iovec aiov;
        int fflag, ioflag, rwflag;
        ssize_t bcount;
        int error = 0;
        u_offset_t fileoff = (u_offset_t)(ulong_t)offset;
        const u_offset_t maxoff = MAXOFF32_T;

        if ((bcount = (ssize_t)count) < 0)
                return (set_errno(EINVAL));
        fflag = FREAD | FWRITE;

        rwflag = 1;

        if (vp->v_type == VREG) {

                if (bcount == 0)
                        goto out;

                /*
                 * return EINVAL for offsets that cannot be
                 * represented in an off_t.
                 */
                if (fileoff > maxoff) {
                        error = EINVAL;
                        goto out;
                }
                /*
                 * Don't allow pwrite to cause file sizes to exceed
                 * maxoff.
                 */
                if (fileoff == maxoff) {
                        error = EFBIG;
                        goto out;
                }
                if (fileoff + count > maxoff)
                        bcount = (ssize_t)((u_offset_t)maxoff - fileoff);
        } else if (vp->v_type == VFIFO) {
                error = ESPIPE;
                goto out;
        }

        aiov.iov_base = cbuf;
        aiov.iov_len = bcount;
        (void) VOP_RWLOCK(vp, rwflag, NULL);
        auio.uio_loffset = fileoff;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_resid = bcount;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_llimit = MAXOFFSET_T;
        auio.uio_fmode = fflag;
        auio.uio_extflg = UIO_COPY_CACHED;

        /*
         * The SUSv4 POSIX specification states:
         *      The pwrite() function shall be equivalent to write(), except
         *      that it writes into a given position and does not change
         *      the file offset (regardless of whether O_APPEND is set).
         * To make this be true, we omit the FAPPEND flag from ioflag.
         */
        ioflag = auio.uio_fmode & (FSYNC|FDSYNC|FRSYNC);

        error = VOP_WRITE(vp, &auio, ioflag, CRED(), NULL);
        bcount -= auio.uio_resid;
        VOP_RWUNLOCK(vp, rwflag, NULL);

        if (error == EINTR && bcount != 0)
                error = 0;
out:
        if (error)
                return (set_errno(error));
        return (bcount);
}