namei.c revision 2eb374c9401079aa56aa12f0047ca3866e69b754 
1/*
2 * namei.c --- ext2fs directory lookup operations
3 *
4 * Copyright (C) 1993, 1994, 1994, 1995 Theodore Ts'o.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Public
8 * License.
9 * %End-Header%
10 */
11
12#include <stdio.h>
13#include <string.h>
14#if HAVE_UNISTD_H
15#include <unistd.h>
16#endif
17
18/* #define NAMEI_DEBUG */
19
20#if EXT2_FLAT_INCLUDES
21#include "ext2_fs.h"
22#else
23#include <linux/ext2_fs.h>
24#endif
25
26#include "ext2fs.h"
27
28static errcode_t open_namei(ext2_filsys fs, ino_t root, ino_t base,
29			    const char *pathname, size_t pathlen, int follow,
30			    int link_count, char *buf, ino_t *res_inode);
31
32static errcode_t follow_link(ext2_filsys fs, ino_t root, ino_t dir,
33			     ino_t inode, int link_count,
34			     char *buf, ino_t *res_inode)
35{
36	char *pathname;
37	char *buffer = 0;
38	errcode_t retval;
39	struct ext2_inode ei;
40
41#ifdef NAMEI_DEBUG
42	printf("follow_link: root=%lu, dir=%lu, inode=%lu, lc=%d\n",
43	       root, dir, inode, link_count);
44
45#endif
46	retval = ext2fs_read_inode (fs, inode, &ei);
47	if (retval) return retval;
48	if (!LINUX_S_ISLNK (ei.i_mode)) {
49		*res_inode = inode;
50		return 0;
51	}
52	if (link_count++ > 5) {
53		return EXT2_ET_SYMLINK_LOOP;
54	}
55	if (ei.i_blocks) {
56		retval = ext2fs_get_mem(fs->blocksize, (void **) &buffer);
57		if (retval)
58			return retval;
59		retval = io_channel_read_blk(fs->io, ei.i_block[0], 1, buffer);
60		if (retval) {
61			ext2fs_free_mem((void **) &buffer);
62			return retval;
63		}
64		pathname = buffer;
65	} else
66		pathname = (char *)&(ei.i_block[0]);
67	retval = open_namei(fs, root, dir, pathname, ei.i_size, 1,
68			    link_count, buf, res_inode);
69	if (buffer)
70		ext2fs_free_mem((void **) &buffer);
71	return retval;
72}
73
74/*
75 * This routine interprets a pathname in the context of the current
76 * directory and the root directory, and returns the inode of the
77 * containing directory, and a pointer to the filename of the file
78 * (pointing into the pathname) and the length of the filename.
79 */
80static errcode_t dir_namei(ext2_filsys fs, ino_t root, ino_t dir,
81			   const char *pathname, int pathlen,
82			   int link_count, char *buf,
83			   const char **name, int *namelen, ino_t *res_inode)
84{
85	char c;
86	const char *thisname;
87	int len;
88	ino_t inode;
89	errcode_t retval;
90
91	if ((c = *pathname) == '/') {
92        	dir = root;
93		pathname++;
94		pathlen--;
95	}
96	while (1) {
97        	thisname = pathname;
98		for (len=0; --pathlen >= 0;len++) {
99			c = *(pathname++);
100			if (c == '/')
101				break;
102		}
103		if (pathlen < 0)
104			break;
105		retval = ext2fs_lookup (fs, dir, thisname, len, buf, &inode);
106		if (retval) return retval;
107        	retval = follow_link (fs, root, dir, inode,
108				      link_count, buf, &dir);
109        	if (retval) return retval;
110    	}
111	*name = thisname;
112	*namelen = len;
113	*res_inode = dir;
114	return 0;
115}
116
117static errcode_t open_namei(ext2_filsys fs, ino_t root, ino_t base,
118			    const char *pathname, size_t pathlen, int follow,
119			    int link_count, char *buf, ino_t *res_inode)
120{
121	const char *basename;
122	int namelen;
123	ino_t dir, inode;
124	errcode_t retval;
125
126#ifdef NAMEI_DEBUG
127	printf("open_namei: root=%lu, dir=%lu, path=%*s, lc=%d\n",
128	       root, base, pathlen, pathname, link_count);
129#endif
130	retval = dir_namei(fs, root, base, pathname, pathlen,
131			   link_count, buf, &basename, &namelen, &dir);
132	if (retval) return retval;
133	if (!namelen) {                     /* special case: '/usr/' etc */
134		*res_inode=dir;
135		return 0;
136	}
137	retval = ext2fs_lookup (fs, dir, basename, namelen, buf, &inode);
138	if (retval)
139		return retval;
140	if (follow) {
141		retval = follow_link(fs, root, dir, inode, link_count,
142				     buf, &inode);
143		if (retval)
144			return retval;
145	}
146#ifdef NAMEI_DEBUG
147	printf("open_namei: (link_count=%d) returns %lu\n",
148	       link_count, inode);
149#endif
150	*res_inode = inode;
151	return 0;
152}
153
154errcode_t ext2fs_namei(ext2_filsys fs, ino_t root, ino_t cwd,
155		       const char *name, ino_t *inode)
156{
157	char *buf;
158	errcode_t retval;
159
160	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
161
162	retval = ext2fs_get_mem(fs->blocksize, (void **) &buf);
163	if (retval)
164		return retval;
165
166	retval = open_namei(fs, root, cwd, name, strlen(name), 0, 0,
167			    buf, inode);
168
169	ext2fs_free_mem((void **) &buf);
170	return retval;
171}
172
173errcode_t ext2fs_namei_follow(ext2_filsys fs, ino_t root, ino_t cwd,
174			      const char *name, ino_t *inode)
175{
176	char *buf;
177	errcode_t retval;
178
179	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
180
181	retval = ext2fs_get_mem(fs->blocksize, (void **) &buf);
182	if (retval)
183		return retval;
184
185	retval = open_namei(fs, root, cwd, name, strlen(name), 1, 0,
186			    buf, inode);
187
188	ext2fs_free_mem((void **) &buf);
189	return retval;
190}
191
192errcode_t ext2fs_follow_link(ext2_filsys fs, ino_t root, ino_t cwd,
193			ino_t inode, ino_t *res_inode)
194{
195	char *buf;
196	errcode_t retval;
197
198	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
199
200	retval = ext2fs_get_mem(fs->blocksize, (void **) &buf);
201	if (retval)
202		return retval;
203
204	retval = follow_link(fs, root, cwd, inode, 0, buf, res_inode);
205
206	ext2fs_free_mem((void **) &buf);
207	return retval;
208}
209
210