namei.c revision 62f17f36031102a2a40fac338e063c556f73b94a 
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 Library
8 * General Public License, version 2.
9 * %End-Header%
10 */
11
12#include "config.h"
13#include <stdio.h>
14#include <string.h>
15#if HAVE_UNISTD_H
16#include <unistd.h>
17#endif
18
19/* #define NAMEI_DEBUG */
20
21#include "ext2_fs.h"
22#include "ext2fs.h"
23#include "ext2fsP.h"
24
25static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
26			    const char *pathname, size_t pathlen, int follow,
27			    int link_count, char *buf, ext2_ino_t *res_inode);
28
29static errcode_t follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
30			     ext2_ino_t inode, int link_count,
31			     char *buf, ext2_ino_t *res_inode)
32{
33	char *pathname;
34	char *buffer = 0;
35	errcode_t retval;
36	struct ext2_inode ei;
37	blk64_t blk;
38
39#ifdef NAMEI_DEBUG
40	printf("follow_link: root=%lu, dir=%lu, inode=%lu, lc=%d\n",
41	       root, dir, inode, link_count);
42
43#endif
44	retval = ext2fs_read_inode (fs, inode, &ei);
45	if (retval) return retval;
46	if (!LINUX_S_ISLNK (ei.i_mode)) {
47		*res_inode = inode;
48		return 0;
49	}
50	if (link_count++ >= EXT2FS_MAX_NESTED_LINKS)
51		return EXT2_ET_SYMLINK_LOOP;
52
53	if (ext2fs_inode_data_blocks(fs,&ei)) {
54		retval = ext2fs_bmap2(fs, inode, &ei, NULL, 0, 0, NULL, &blk);
55		if (retval)
56			return retval;
57
58		retval = ext2fs_get_mem(fs->blocksize, &buffer);
59		if (retval)
60			return retval;
61
62		retval = io_channel_read_blk64(fs->io, blk, 1, buffer);
63		if (retval) {
64			ext2fs_free_mem(&buffer);
65			return retval;
66		}
67		pathname = buffer;
68	} else
69		pathname = (char *)&(ei.i_block[0]);
70	retval = open_namei(fs, root, dir, pathname, ei.i_size, 1,
71			    link_count, buf, res_inode);
72	if (buffer)
73		ext2fs_free_mem(&buffer);
74	return retval;
75}
76
77/*
78 * This routine interprets a pathname in the context of the current
79 * directory and the root directory, and returns the inode of the
80 * containing directory, and a pointer to the filename of the file
81 * (pointing into the pathname) and the length of the filename.
82 */
83static errcode_t dir_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
84			   const char *pathname, int pathlen,
85			   int link_count, char *buf,
86			   const char **name, int *namelen,
87			   ext2_ino_t *res_inode)
88{
89	char c;
90	const char *thisname;
91	int len;
92	ext2_ino_t inode;
93	errcode_t retval;
94
95	if ((c = *pathname) == '/') {
96        	dir = root;
97		pathname++;
98		pathlen--;
99	}
100	while (1) {
101        	thisname = pathname;
102		for (len=0; --pathlen >= 0;len++) {
103			c = *(pathname++);
104			if (c == '/')
105				break;
106		}
107		if (pathlen < 0)
108			break;
109		retval = ext2fs_lookup (fs, dir, thisname, len, buf, &inode);
110		if (retval) return retval;
111        	retval = follow_link (fs, root, dir, inode,
112				      link_count, buf, &dir);
113        	if (retval) return retval;
114    	}
115	*name = thisname;
116	*namelen = len;
117	*res_inode = dir;
118	return 0;
119}
120
121static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
122			    const char *pathname, size_t pathlen, int follow,
123			    int link_count, char *buf, ext2_ino_t *res_inode)
124{
125	const char *base_name;
126	int namelen;
127	ext2_ino_t dir, inode;
128	errcode_t retval;
129
130#ifdef NAMEI_DEBUG
131	printf("open_namei: root=%lu, dir=%lu, path=%*s, lc=%d\n",
132	       root, base, pathlen, pathname, link_count);
133#endif
134	retval = dir_namei(fs, root, base, pathname, pathlen,
135			   link_count, buf, &base_name, &namelen, &dir);
136	if (retval) return retval;
137	if (!namelen) {                     /* special case: '/usr/' etc */
138		*res_inode=dir;
139		return 0;
140	}
141	retval = ext2fs_lookup (fs, dir, base_name, namelen, buf, &inode);
142	if (retval)
143		return retval;
144	if (follow) {
145		retval = follow_link(fs, root, dir, inode, link_count,
146				     buf, &inode);
147		if (retval)
148			return retval;
149	}
150#ifdef NAMEI_DEBUG
151	printf("open_namei: (link_count=%d) returns %lu\n",
152	       link_count, inode);
153#endif
154	*res_inode = inode;
155	return 0;
156}
157
158errcode_t ext2fs_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
159		       const char *name, ext2_ino_t *inode)
160{
161	char *buf;
162	errcode_t retval;
163
164	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
165
166	retval = ext2fs_get_mem(fs->blocksize, &buf);
167	if (retval)
168		return retval;
169
170	retval = open_namei(fs, root, cwd, name, strlen(name), 0, 0,
171			    buf, inode);
172
173	ext2fs_free_mem(&buf);
174	return retval;
175}
176
177errcode_t ext2fs_namei_follow(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
178			      const char *name, ext2_ino_t *inode)
179{
180	char *buf;
181	errcode_t retval;
182
183	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
184
185	retval = ext2fs_get_mem(fs->blocksize, &buf);
186	if (retval)
187		return retval;
188
189	retval = open_namei(fs, root, cwd, name, strlen(name), 1, 0,
190			    buf, inode);
191
192	ext2fs_free_mem(&buf);
193	return retval;
194}
195
196errcode_t ext2fs_follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
197			ext2_ino_t inode, ext2_ino_t *res_inode)
198{
199	char *buf;
200	errcode_t retval;
201
202	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
203
204	retval = ext2fs_get_mem(fs->blocksize, &buf);
205	if (retval)
206		return retval;
207
208	retval = follow_link(fs, root, cwd, inode, 0, buf, res_inode);
209
210	ext2fs_free_mem(&buf);
211	return retval;
212}
213
214