1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.
24  */
25 
26 /*	Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T	*/
27 /*	  All Rights Reserved  	*/
28 
29 /*
30  * Portions of this source code were derived from Berkeley 4.3 BSD
31  * under license from the Regents of the University of California.
32  */
33 
34 #include <sys/param.h>
35 #include <sys/isa_defs.h>
36 #include <sys/types.h>
37 #include <sys/sysmacros.h>
38 #include <sys/cred.h>
39 #include <sys/systm.h>
40 #include <sys/errno.h>
41 #include <sys/pathname.h>
42 #include <sys/vnode.h>
43 #include <sys/file.h>
44 #include <sys/fcntl.h>
45 #include <sys/uio.h>
46 #include <sys/debug.h>
47 #include <fs/fs_subr.h>
48 #include <c2/audit.h>
49 
50 /*
51  * Read the contents of a symbolic link.
52  */
53 ssize_t
readlinkat(int dfd,char * name,char * buf,size_t count)54 readlinkat(int dfd, char *name, char *buf, size_t count)
55 {
56 	vnode_t *startvp;
57 	vnode_t *vp;
58 	struct iovec aiov;
59 	struct uio auio;
60 	int error;
61 	struct vattr vattr;
62 	ssize_t cnt;
63 	int estale_retry = 0;
64 
65 	if ((cnt = (ssize_t)count) < 0)
66 		return (set_errno(EINVAL));
67 	if (name == NULL)
68 		return (set_errno(EFAULT));
69 	if ((error = fgetstartvp(dfd, name, &startvp)) != 0)
70 		return (set_errno(error));
71 
72 lookup:
73 	if (AU_AUDITING() && startvp != NULL)
74 		audit_setfsat_path(1);
75 	if (error = lookupnameat(name, UIO_USERSPACE, NO_FOLLOW,
76 	    NULLVPP, &vp, startvp)) {
77 		if (error == ESTALE && fs_need_estale_retry(estale_retry++))
78 			goto lookup;
79 		goto out;
80 	}
81 
82 	if (vp->v_type != VLNK) {
83 		/*
84 		 * Ask the underlying filesystem if it wants this
85 		 * object to look like a symlink at user-level.
86 		 */
87 		vattr.va_mask = AT_TYPE;
88 		error = VOP_GETATTR(vp, &vattr, 0, CRED(), NULL);
89 		if (error || vattr.va_type != VLNK) {
90 			VN_RELE(vp);
91 			if ((error == ESTALE) &&
92 			    fs_need_estale_retry(estale_retry++))
93 				goto lookup;
94 			error = EINVAL;
95 			goto out;
96 		}
97 	}
98 	aiov.iov_base = buf;
99 	aiov.iov_len = cnt;
100 	auio.uio_iov = &aiov;
101 	auio.uio_iovcnt = 1;
102 	auio.uio_loffset = 0;
103 	auio.uio_segflg = UIO_USERSPACE;
104 	auio.uio_extflg = UIO_COPY_CACHED;
105 	auio.uio_resid = cnt;
106 	error = VOP_READLINK(vp, &auio, CRED(), NULL);
107 	VN_RELE(vp);
108 	if (error == ESTALE && fs_need_estale_retry(estale_retry++))
109 		goto lookup;
110 out:
111 	if (startvp != NULL)
112 		VN_RELE(startvp);
113 	if (error)
114 		return (set_errno(error));
115 	return ((ssize_t)(cnt - auio.uio_resid));
116 }
117 
118 ssize_t
readlink(char * name,char * buf,size_t count)119 readlink(char *name, char *buf, size_t count)
120 {
121 	return (readlinkat(AT_FDCWD, name, buf, count));
122 }
123 
124 #ifdef _SYSCALL32_IMPL
125 /*
126  * readlink32() intentionally returns a ssize_t rather than ssize32_t;
127  * see the comments above read32 for details.
128  */
129 
130 ssize_t
readlinkat32(int dfd,caddr32_t name,caddr32_t buf,size32_t count)131 readlinkat32(int dfd, caddr32_t name, caddr32_t buf, size32_t count)
132 {
133 	return ((ssize32_t)readlinkat(dfd, (char *)(uintptr_t)name,
134 	    (char *)(uintptr_t)buf, (ssize32_t)count));
135 }
136 
137 ssize_t
readlink32(caddr32_t name,caddr32_t buf,size32_t count)138 readlink32(caddr32_t name, caddr32_t buf, size32_t count)
139 {
140 	return ((ssize32_t)readlinkat(AT_FDCWD, (char *)(uintptr_t)name,
141 	    (char *)(uintptr_t)buf, (ssize32_t)count));
142 }
143 
144 #endif	/* _SYSCALL32_IMPL */
145