namei.c revision efc6f628e15de95bcd13e4f0ee223cb42115d520 
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#include "ext2_fs.h"
21#include "ext2fs.h"
22
23static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
24			    const char *pathname, size_t pathlen, int follow,
25			    int link_count, char *buf, ext2_ino_t *res_inode);
26
27static errcode_t follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
28			     ext2_ino_t inode, int link_count,
29			     char *buf, ext2_ino_t *res_inode)
30{
31	char *pathname;
32	char *buffer = 0;
33	errcode_t retval;
34	struct ext2_inode ei;
35
36#ifdef NAMEI_DEBUG
37	printf("follow_link: root=%lu, dir=%lu, inode=%lu, lc=%d\n",
38	       root, dir, inode, link_count);
39
40#endif
41	retval = ext2fs_read_inode (fs, inode, &ei);
42	if (retval) return retval;
43	if (!LINUX_S_ISLNK (ei.i_mode)) {
44		*res_inode = inode;
45		return 0;
46	}
47	if (link_count++ > 5) {
48		return EXT2_ET_SYMLINK_LOOP;
49	}
50	if (ext2fs_inode_data_blocks(fs,&ei)) {
51		retval = ext2fs_get_mem(fs->blocksize, &buffer);
52		if (retval)
53			return retval;
54		retval = io_channel_read_blk(fs->io, ei.i_block[0], 1, buffer);
55		if (retval) {
56			ext2fs_free_mem(&buffer);
57			return retval;
58		}
59		pathname = buffer;
60	} else
61		pathname = (char *)&(ei.i_block[0]);
62	retval = open_namei(fs, root, dir, pathname, ei.i_size, 1,
63			    link_count, buf, res_inode);
64	if (buffer)
65		ext2fs_free_mem(&buffer);
66	return retval;
67}
68
69/*
70 * This routine interprets a pathname in the context of the current
71 * directory and the root directory, and returns the inode of the
72 * containing directory, and a pointer to the filename of the file
73 * (pointing into the pathname) and the length of the filename.
74 */
75static errcode_t dir_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
76			   const char *pathname, int pathlen,
77			   int link_count, char *buf,
78			   const char **name, int *namelen,
79			   ext2_ino_t *res_inode)
80{
81	char c;
82	const char *thisname;
83	int len;
84	ext2_ino_t inode;
85	errcode_t retval;
86
87	if ((c = *pathname) == '/') {
88        	dir = root;
89		pathname++;
90		pathlen--;
91	}
92	while (1) {
93        	thisname = pathname;
94		for (len=0; --pathlen >= 0;len++) {
95			c = *(pathname++);
96			if (c == '/')
97				break;
98		}
99		if (pathlen < 0)
100			break;
101		retval = ext2fs_lookup (fs, dir, thisname, len, buf, &inode);
102		if (retval) return retval;
103        	retval = follow_link (fs, root, dir, inode,
104				      link_count, buf, &dir);
105        	if (retval) return retval;
106    	}
107	*name = thisname;
108	*namelen = len;
109	*res_inode = dir;
110	return 0;
111}
112
113static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
114			    const char *pathname, size_t pathlen, int follow,
115			    int link_count, char *buf, ext2_ino_t *res_inode)
116{
117	const char *base_name;
118	int namelen;
119	ext2_ino_t dir, inode;
120	errcode_t retval;
121
122#ifdef NAMEI_DEBUG
123	printf("open_namei: root=%lu, dir=%lu, path=%*s, lc=%d\n",
124	       root, base, pathlen, pathname, link_count);
125#endif
126	retval = dir_namei(fs, root, base, pathname, pathlen,
127			   link_count, buf, &base_name, &namelen, &dir);
128	if (retval) return retval;
129	if (!namelen) {                     /* special case: '/usr/' etc */
130		*res_inode=dir;
131		return 0;
132	}
133	retval = ext2fs_lookup (fs, dir, base_name, namelen, buf, &inode);
134	if (retval)
135		return retval;
136	if (follow) {
137		retval = follow_link(fs, root, dir, inode, link_count,
138				     buf, &inode);
139		if (retval)
140			return retval;
141	}
142#ifdef NAMEI_DEBUG
143	printf("open_namei: (link_count=%d) returns %lu\n",
144	       link_count, inode);
145#endif
146	*res_inode = inode;
147	return 0;
148}
149
150errcode_t ext2fs_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
151		       const char *name, ext2_ino_t *inode)
152{
153	char *buf;
154	errcode_t retval;
155
156	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
157
158	retval = ext2fs_get_mem(fs->blocksize, &buf);
159	if (retval)
160		return retval;
161
162	retval = open_namei(fs, root, cwd, name, strlen(name), 0, 0,
163			    buf, inode);
164
165	ext2fs_free_mem(&buf);
166	return retval;
167}
168
169errcode_t ext2fs_namei_follow(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
170			      const char *name, ext2_ino_t *inode)
171{
172	char *buf;
173	errcode_t retval;
174
175	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
176
177	retval = ext2fs_get_mem(fs->blocksize, &buf);
178	if (retval)
179		return retval;
180
181	retval = open_namei(fs, root, cwd, name, strlen(name), 1, 0,
182			    buf, inode);
183
184	ext2fs_free_mem(&buf);
185	return retval;
186}
187
188errcode_t ext2fs_follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
189			ext2_ino_t inode, ext2_ino_t *res_inode)
190{
191	char *buf;
192	errcode_t retval;
193
194	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
195
196	retval = ext2fs_get_mem(fs->blocksize, &buf);
197	if (retval)
198		return retval;
199
200	retval = follow_link(fs, root, cwd, inode, 0, buf, res_inode);
201
202	ext2fs_free_mem(&buf);
203	return retval;
204}
205
206