linux_util.c revision 72091 
1/*
2 * Copyright (c) 1994 Christos Zoulas
3 * Copyright (c) 1995 Frank van der Linden
4 * Copyright (c) 1995 Scott Bartram
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. The name of the author may not be used to endorse or promote products
16 *    derived from this software without specific prior written permission
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 *	from: svr4_util.c,v 1.5 1995/01/22 23:44:50 christos Exp
30 * $FreeBSD: head/sys/compat/linux/linux_util.c 72091 2001-02-06 11:21:58Z asmodai $
31 */
32
33#include <sys/param.h>
34#include <sys/systm.h>
35#include <sys/namei.h>
36#include <sys/proc.h>
37#include <sys/malloc.h>
38#include <sys/vnode.h>
39
40#include <compat/linux/linux_util.h>
41
42const char      linux_emul_path[] = "/compat/linux";
43
44/*
45 * Search an alternate path before passing pathname arguments on
46 * to system calls. Useful for keeping a separate 'emulation tree'.
47 *
48 * If cflag is set, we check if an attempt can be made to create
49 * the named file, i.e. we check if the directory it should
50 * be in exists.
51 */
52int
53linux_emul_find(p, sgp, prefix, path, pbuf, cflag)
54	struct proc	 *p;
55	caddr_t		 *sgp;		/* Pointer to stackgap memory */
56	const char	 *prefix;
57	char		 *path;
58	char		**pbuf;
59	int		  cflag;
60{
61	struct nameidata	 nd;
62	struct nameidata	 ndroot;
63	struct vattr		 vat;
64	struct vattr		 vatroot;
65	int			 error;
66	char			*ptr, *buf, *cp;
67	size_t			 sz, len;
68
69	buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
70	*pbuf = path;
71
72	for (ptr = buf; (*ptr = *prefix) != '\0'; ptr++, prefix++)
73		continue;
74
75	sz = MAXPATHLEN - (ptr - buf);
76
77	/*
78	 * If sgp is not given then the path is already in kernel space
79	 */
80	if (sgp == NULL)
81		error = copystr(path, ptr, sz, &len);
82	else
83		error = copyinstr(path, ptr, sz, &len);
84
85	if (error) {
86		free(buf, M_TEMP);
87		return error;
88	}
89
90	if (*ptr != '/') {
91		free(buf, M_TEMP);
92		return EINVAL;
93	}
94
95	/*
96	 * We know that there is a / somewhere in this pathname.
97	 * Search backwards for it, to find the file's parent dir
98	 * to see if it exists in the alternate tree. If it does,
99	 * and we want to create a file (cflag is set). We don't
100	 * need to worry about the root comparison in this case.
101	 */
102
103	if (cflag) {
104		for (cp = &ptr[len] - 1; *cp != '/'; cp--);
105		*cp = '\0';
106
107		NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
108
109		if ((error = namei(&nd)) != 0) {
110			free(buf, M_TEMP);
111			return error;
112		}
113
114		*cp = '/';
115	}
116	else {
117		NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
118
119		if ((error = namei(&nd)) != 0) {
120			free(buf, M_TEMP);
121			return error;
122		}
123
124		/*
125		 * We now compare the vnode of the linux_root to the one
126		 * vnode asked. If they resolve to be the same, then we
127		 * ignore the match so that the real root gets used.
128		 * This avoids the problem of traversing "../.." to find the
129		 * root directory and never finding it, because "/" resolves
130		 * to the emulation root directory. This is expensive :-(
131		 */
132		NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, linux_emul_path,
133		       p);
134
135		if ((error = namei(&ndroot)) != 0) {
136			/* Cannot happen! */
137			free(buf, M_TEMP);
138			NDFREE(&nd, NDF_ONLY_PNBUF);
139			vrele(nd.ni_vp);
140			return error;
141		}
142
143		if ((error = VOP_GETATTR(nd.ni_vp, &vat, p->p_ucred, p)) != 0) {
144			goto bad;
145		}
146
147		if ((error = VOP_GETATTR(ndroot.ni_vp, &vatroot, p->p_ucred, p))
148		    != 0) {
149			goto bad;
150		}
151
152		if (vat.va_fsid == vatroot.va_fsid &&
153		    vat.va_fileid == vatroot.va_fileid) {
154			error = ENOENT;
155			goto bad;
156		}
157
158	}
159	if (sgp == NULL)
160		*pbuf = buf;
161	else {
162		sz = &ptr[len] - buf;
163		*pbuf = stackgap_alloc(sgp, sz + 1);
164		if (*pbuf != NULL)
165			error = copyout(buf, *pbuf, sz);
166		else
167			error = ENAMETOOLONG;
168		free(buf, M_TEMP);
169	}
170
171	NDFREE(&nd, NDF_ONLY_PNBUF);
172	vrele(nd.ni_vp);
173	if (!cflag) {
174		NDFREE(&ndroot, NDF_ONLY_PNBUF);
175		vrele(ndroot.ni_vp);
176	}
177	return error;
178
179bad:
180	NDFREE(&ndroot, NDF_ONLY_PNBUF);
181	vrele(ndroot.ni_vp);
182	NDFREE(&nd, NDF_ONLY_PNBUF);
183	vrele(nd.ni_vp);
184	free(buf, M_TEMP);
185	return error;
186}
187