linux_util.c revision 17450 
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 *	$Id: linux_util.c,v 1.1 1996/03/02 19:38:02 peter Exp $
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/file.h>
38#include <sys/stat.h>
39#include <sys/filedesc.h>
40#include <sys/ioctl.h>
41#include <sys/kernel.h>
42#include <sys/malloc.h>
43#include <sys/vnode.h>
44
45#include <i386/linux/linux_util.h>
46
47const char      linux_emul_path[] = "/compat/linux";
48
49/*
50 * Search an alternate path before passing pathname arguments on
51 * to system calls. Useful for keeping a seperate 'emulation tree'.
52 *
53 * If cflag is set, we check if an attempt can be made to create
54 * the named file, i.e. we check if the directory it should
55 * be in exists.
56 */
57int
58linux_emul_find(p, sgp, prefix, path, pbuf, cflag)
59	struct proc	 *p;
60	caddr_t		 *sgp;		/* Pointer to stackgap memory */
61	const char	 *prefix;
62	char		 *path;
63	char		**pbuf;
64	int		  cflag;
65{
66	struct nameidata	 nd;
67	struct nameidata	 ndroot;
68	struct vattr		 vat;
69	struct vattr		 vatroot;
70	int			 error;
71	char			*ptr, *buf, *cp;
72	size_t			 sz, len;
73
74	buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
75	*pbuf = path;
76
77	for (ptr = buf; (*ptr = *prefix) != '\0'; ptr++, prefix++)
78		continue;
79
80	sz = MAXPATHLEN - (ptr - buf);
81
82	/*
83	 * If sgp is not given then the path is already in kernel space
84	 */
85	if (sgp == NULL)
86		error = copystr(path, ptr, sz, &len);
87	else
88		error = copyinstr(path, ptr, sz, &len);
89
90	if (error) {
91		free(buf, M_TEMP);
92		return error;
93	}
94
95	if (*ptr != '/') {
96		free(buf, M_TEMP);
97		return EINVAL;
98	}
99
100	/*
101	 * We know that there is a / somewhere in this pathname.
102	 * Search backwards for it, to find the file's parent dir
103	 * to see if it exists in the alternate tree. If it does,
104	 * and we want to create a file (cflag is set). We don't
105	 * need to worry about the root comparison in this case.
106	 */
107
108	if (cflag) {
109		for (cp = &ptr[len] - 1; *cp != '/'; cp--);
110		*cp = '\0';
111
112		NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
113
114		if ((error = namei(&nd)) != 0) {
115			free(buf, M_TEMP);
116			return error;
117		}
118
119		*cp = '/';
120	}
121	else {
122		NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
123
124		if ((error = namei(&nd)) != 0) {
125			free(buf, M_TEMP);
126			return error;
127		}
128
129		/*
130		 * We now compare the vnode of the linux_root to the one
131		 * vnode asked. If they resolve to be the same, then we
132		 * ignore the match so that the real root gets used.
133		 * This avoids the problem of traversing "../.." to find the
134		 * root directory and never finding it, because "/" resolves
135		 * to the emulation root directory. This is expensive :-(
136		 */
137		/* XXX: prototype should have const here for NDINIT */
138		NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE,
139		       (char *) linux_emul_path, p);
140
141		if ((error = namei(&ndroot)) != 0) {
142			/* Cannot happen! */
143			free(buf, M_TEMP);
144			vrele(nd.ni_vp);
145			return error;
146		}
147
148		if ((error = VOP_GETATTR(nd.ni_vp, &vat, p->p_ucred, p)) != 0) {
149			goto bad;
150		}
151
152		if ((error = VOP_GETATTR(ndroot.ni_vp, &vatroot, p->p_ucred, p))
153		    != 0) {
154			goto bad;
155		}
156
157		if (vat.va_fsid == vatroot.va_fsid &&
158		    vat.va_fileid == vatroot.va_fileid) {
159			error = ENOENT;
160			goto bad;
161		}
162
163	}
164	if (sgp == NULL)
165		*pbuf = buf;
166	else {
167		sz = &ptr[len] - buf;
168		*pbuf = stackgap_alloc(sgp, sz + 1);
169		error = copyout(buf, *pbuf, sz);
170		free(buf, M_TEMP);
171	}
172
173	vrele(nd.ni_vp);
174	if (!cflag)
175		vrele(ndroot.ni_vp);
176	return error;
177
178bad:
179	vrele(ndroot.ni_vp);
180	vrele(nd.ni_vp);
181	free(buf, M_TEMP);
182	return error;
183}
184