compat_util.c revision 1.2 1 /* $NetBSD: compat_util.c,v 1.2 1995/06/26 19:27:17 christos Exp $ */
2
3 /*
4 * Copyright (c) 1994 Christos Zoulas
5 * Copyright (c) 1995 Frank van der Linden
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote products
17 * derived from this software without specific prior written permission
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 */
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/namei.h>
35 #include <sys/proc.h>
36 #include <sys/file.h>
37 #include <sys/stat.h>
38 #include <sys/filedesc.h>
39 #include <sys/ioctl.h>
40 #include <sys/kernel.h>
41 #include <sys/malloc.h>
42 #include <sys/vnode.h>
43
44 #include <compat/common/compat_util.h>
45
46 /*
47 * Search an alternate path before passing pathname arguments on
48 * to system calls. Useful for keeping a separate 'emulation tree'.
49 *
50 * If cflag is set, we check if an attempt can be made to create
51 * the named file, i.e. we check if the directory it should
52 * be in exists.
53 */
54 int
55 emul_find(p, sgp, prefix, path, pbuf, cflag)
56 struct proc *p;
57 caddr_t *sgp; /* Pointer to stackgap memory */
58 const char *prefix;
59 char *path;
60 char **pbuf;
61 int cflag;
62 {
63 struct nameidata nd;
64 struct nameidata ndroot;
65 struct vattr vat;
66 struct vattr vatroot;
67 int error;
68 char *ptr, *buf, *cp;
69 const char *pr;
70 size_t sz, len;
71
72 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
73 *pbuf = path;
74
75 for (ptr = buf, pr = prefix; (*ptr = *pr) != '\0'; ptr++, pr++)
76 continue;
77
78 sz = MAXPATHLEN - (ptr - buf);
79
80 /*
81 * If sgp is not given then the path is already in kernel space
82 */
83 if (sgp == NULL)
84 error = copystr(path, ptr, sz, &len);
85 else
86 error = copyinstr(path, ptr, sz, &len);
87
88 if (error) {
89 free(buf, M_TEMP);
90 return error;
91 }
92
93 if (*ptr != '/') {
94 free(buf, M_TEMP);
95 return EINVAL;
96 }
97
98 /*
99 * We know that there is a / somewhere in this pathname.
100 * Search backwards for it, to find the file's parent dir
101 * to see if it exists in the alternate tree. If it does,
102 * and we want to create a file (cflag is set). We don't
103 * need to worry about the root comparison in this case.
104 */
105
106 if (cflag) {
107 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
108 *cp = '\0';
109
110 NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
111
112 if ((error = namei(&nd)) != 0) {
113 free(buf, M_TEMP);
114 return error;
115 }
116
117 *cp = '/';
118 }
119 else {
120 NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
121
122 if ((error = namei(&nd)) != 0) {
123 free(buf, M_TEMP);
124 return error;
125 }
126
127 /*
128 * We now compare the vnode of the emulation root to the one
129 * vnode asked. If they resolve to be the same, then we
130 * ignore the match so that the real root gets used.
131 * This avoids the problem of traversing "../.." to find the
132 * root directory and never finding it, because "/" resolves
133 * to the emulation root directory. This is expensive :-(
134 */
135 /* XXX: prototype should have const here for NDINIT */
136 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE,
137 (char *) prefix, p);
138
139 if ((error = namei(&ndroot)) != 0) {
140 /* Cannot happen! */
141 free(buf, M_TEMP);
142 vrele(nd.ni_vp);
143 return error;
144 }
145
146 if ((error = VOP_GETATTR(nd.ni_vp, &vat, p->p_ucred, p)) != 0) {
147 goto done;
148 }
149
150 if ((error = VOP_GETATTR(ndroot.ni_vp, &vatroot, p->p_ucred, p))
151 != 0) {
152 goto done;
153 }
154
155 if (vat.va_fsid == vatroot.va_fsid &&
156 vat.va_fileid == vatroot.va_fileid) {
157 error = ENOENT;
158 goto done;
159 }
160
161 }
162 if (sgp == NULL)
163 *pbuf = buf;
164 else {
165 sz = &ptr[len] - buf;
166 *pbuf = stackgap_alloc(sgp, sz + 1);
167 error = copyout(buf, *pbuf, sz);
168 free(buf, M_TEMP);
169 }
170
171
172 done:
173 vrele(nd.ni_vp);
174 if (!cflag)
175 vrele(ndroot.ni_vp);
176 return error;
177 }
178