common/syscall/readlink.c

	readlink.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  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.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/param.h>
#include <sys/isa_defs.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/cred.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/pathname.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/uio.h>
#include <sys/ioreq.h>
#include <sys/debug.h>

/*
 * Read the contents of a symbolic link.
 */
ssize_t
readlink(char *name, char *buf, size_t count)
{
    vnode_t *vp;
    struct iovec aiov;
    struct uio auio;
    int error;
    struct vattr vattr;
    ssize_t cnt;

    if ((cnt = (ssize_t)count) < 0)
        return (set_errno(EINVAL));

lookup:
    if (error = lookupname(name, UIO_USERSPACE, NO_FOLLOW, NULLVPP, &vp)) {
        if (error == ESTALE)
            goto lookup;
        return (set_errno(error));
    }

    if (vp->v_type != VLNK) {
        /*
         * Ask the underlying filesystem if it wants this
         * object to look like a symlink at user-level.
         */
        vattr.va_mask = AT_TYPE;
        error = VOP_GETATTR(vp, &vattr, 0, CRED());
        if (error || vattr.va_type != VLNK) {
            VN_RELE(vp);
            if (error == ESTALE)
                goto lookup;
            return (set_errno(EINVAL));
        }
    }
    aiov.iov_base = buf;
    aiov.iov_len = cnt;
    auio.uio_iov = &aiov;
    auio.uio_iovcnt = 1;
    auio.uio_loffset = 0;
    auio.uio_segflg = UIO_USERSPACE;
    auio.uio_extflg = UIO_COPY_CACHED;
    auio.uio_resid = cnt;
    error = VOP_READLINK(vp, &auio, CRED());
    VN_RELE(vp);
    if (error) {
        if (error == ESTALE)
            goto lookup;
        return (set_errno(error));
    }
    return ((ssize_t)(cnt - auio.uio_resid));
}

#ifdef _SYSCALL32_IMPL
/*
 * readlink32() intentionally returns a ssize_t rather than ssize32_t;
 * see the comments above read32 for details.
 */

ssize_t
readlink32(caddr32_t name, caddr32_t buf, size32_t count)
{
    return ((ssize32_t)readlink((char *)(uintptr_t)name,
        (char *)(uintptr_t)buf, (ssize32_t)count));
}

#endif  /* _SYSCALL32_IMPL */