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Commit | Line | Data |
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1da177e4 | 1 | /* |
6d66f5cd TH |
2 | * fs/sysfs/symlink.c - sysfs symlink implementation |
3 | * | |
4 | * Copyright (c) 2001-3 Patrick Mochel | |
5 | * Copyright (c) 2007 SUSE Linux Products GmbH | |
6 | * Copyright (c) 2007 Tejun Heo <teheo@suse.de> | |
7 | * | |
8 | * This file is released under the GPLv2. | |
9 | * | |
10 | * Please see Documentation/filesystems/sysfs.txt for more information. | |
1da177e4 LT |
11 | */ |
12 | ||
13 | #include <linux/fs.h> | |
5a0e3ad6 | 14 | #include <linux/gfp.h> |
ceeee1fb | 15 | #include <linux/mount.h> |
1da177e4 LT |
16 | #include <linux/module.h> |
17 | #include <linux/kobject.h> | |
18 | #include <linux/namei.h> | |
869512ab | 19 | #include <linux/mutex.h> |
ddd29ec6 | 20 | #include <linux/security.h> |
1da177e4 LT |
21 | |
22 | #include "sysfs.h" | |
23 | ||
36ce6dad CH |
24 | static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, |
25 | const char *name, int warn) | |
1da177e4 | 26 | { |
2b29ac25 TH |
27 | struct sysfs_dirent *parent_sd = NULL; |
28 | struct sysfs_dirent *target_sd = NULL; | |
3007e997 | 29 | struct sysfs_dirent *sd = NULL; |
fb6896da | 30 | struct sysfs_addrm_cxt acxt; |
3007e997 | 31 | int error; |
1da177e4 | 32 | |
ceeee1fb GKH |
33 | BUG_ON(!name); |
34 | ||
7d0c7d67 EB |
35 | if (!kobj) |
36 | parent_sd = &sysfs_root; | |
37 | else | |
608e266a | 38 | parent_sd = kobj->sd; |
ceeee1fb | 39 | |
3007e997 | 40 | error = -EFAULT; |
608e266a | 41 | if (!parent_sd) |
3007e997 | 42 | goto out_put; |
2b29ac25 | 43 | |
608e266a | 44 | /* target->sd can go away beneath us but is protected with |
5f995323 | 45 | * sysfs_assoc_lock. Fetch target_sd from it. |
2b29ac25 | 46 | */ |
5f995323 | 47 | spin_lock(&sysfs_assoc_lock); |
608e266a TH |
48 | if (target->sd) |
49 | target_sd = sysfs_get(target->sd); | |
5f995323 | 50 | spin_unlock(&sysfs_assoc_lock); |
2b29ac25 | 51 | |
3007e997 | 52 | error = -ENOENT; |
2b29ac25 | 53 | if (!target_sd) |
3007e997 TH |
54 | goto out_put; |
55 | ||
56 | error = -ENOMEM; | |
57 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); | |
58 | if (!sd) | |
59 | goto out_put; | |
a1da4dfe | 60 | |
b1fc3d61 | 61 | sd->s_symlink.target_sd = target_sd; |
a1da4dfe | 62 | target_sd = NULL; /* reference is now owned by the symlink */ |
1da177e4 | 63 | |
fb6896da | 64 | sysfs_addrm_start(&acxt, parent_sd); |
36ce6dad CH |
65 | if (warn) |
66 | error = sysfs_add_one(&acxt, sd); | |
67 | else | |
68 | error = __sysfs_add_one(&acxt, sd); | |
23dc2799 | 69 | sysfs_addrm_finish(&acxt); |
2b29ac25 | 70 | |
23dc2799 | 71 | if (error) |
967e35dc | 72 | goto out_put; |
967e35dc TH |
73 | |
74 | return 0; | |
fb6896da | 75 | |
3007e997 TH |
76 | out_put: |
77 | sysfs_put(target_sd); | |
78 | sysfs_put(sd); | |
1da177e4 LT |
79 | return error; |
80 | } | |
81 | ||
36ce6dad CH |
82 | /** |
83 | * sysfs_create_link - create symlink between two objects. | |
84 | * @kobj: object whose directory we're creating the link in. | |
85 | * @target: object we're pointing to. | |
86 | * @name: name of the symlink. | |
87 | */ | |
88 | int sysfs_create_link(struct kobject *kobj, struct kobject *target, | |
89 | const char *name) | |
90 | { | |
91 | return sysfs_do_create_link(kobj, target, name, 1); | |
92 | } | |
93 | ||
94 | /** | |
95 | * sysfs_create_link_nowarn - create symlink between two objects. | |
96 | * @kobj: object whose directory we're creating the link in. | |
97 | * @target: object we're pointing to. | |
98 | * @name: name of the symlink. | |
99 | * | |
100 | * This function does the same as sysf_create_link(), but it | |
101 | * doesn't warn if the link already exists. | |
102 | */ | |
103 | int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, | |
104 | const char *name) | |
105 | { | |
106 | return sysfs_do_create_link(kobj, target, name, 0); | |
107 | } | |
108 | ||
1da177e4 LT |
109 | /** |
110 | * sysfs_remove_link - remove symlink in object's directory. | |
111 | * @kobj: object we're acting for. | |
112 | * @name: name of the symlink to remove. | |
113 | */ | |
114 | ||
e3a15db2 | 115 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 | 116 | { |
a839c5af MF |
117 | struct sysfs_dirent *parent_sd = NULL; |
118 | ||
119 | if (!kobj) | |
120 | parent_sd = &sysfs_root; | |
121 | else | |
122 | parent_sd = kobj->sd; | |
123 | ||
124 | sysfs_hash_and_remove(parent_sd, name); | |
1da177e4 LT |
125 | } |
126 | ||
7cb32942 EB |
127 | /** |
128 | * sysfs_rename_link - rename symlink in object's directory. | |
129 | * @kobj: object we're acting for. | |
130 | * @targ: object we're pointing to. | |
131 | * @old: previous name of the symlink. | |
132 | * @new: new name of the symlink. | |
133 | * | |
134 | * A helper function for the common rename symlink idiom. | |
135 | */ | |
136 | int sysfs_rename_link(struct kobject *kobj, struct kobject *targ, | |
137 | const char *old, const char *new) | |
138 | { | |
139 | struct sysfs_dirent *parent_sd, *sd = NULL; | |
140 | int result; | |
141 | ||
142 | if (!kobj) | |
143 | parent_sd = &sysfs_root; | |
144 | else | |
145 | parent_sd = kobj->sd; | |
146 | ||
147 | result = -ENOENT; | |
148 | sd = sysfs_get_dirent(parent_sd, old); | |
149 | if (!sd) | |
150 | goto out; | |
151 | ||
152 | result = -EINVAL; | |
153 | if (sysfs_type(sd) != SYSFS_KOBJ_LINK) | |
154 | goto out; | |
155 | if (sd->s_symlink.target_sd->s_dir.kobj != targ) | |
156 | goto out; | |
157 | ||
158 | result = sysfs_rename(sd, parent_sd, new); | |
159 | ||
160 | out: | |
161 | sysfs_put(sd); | |
162 | return result; | |
163 | } | |
164 | ||
2f90a851 KS |
165 | static int sysfs_get_target_path(struct sysfs_dirent *parent_sd, |
166 | struct sysfs_dirent *target_sd, char *path) | |
1da177e4 | 167 | { |
2f90a851 KS |
168 | struct sysfs_dirent *base, *sd; |
169 | char *s = path; | |
170 | int len = 0; | |
171 | ||
172 | /* go up to the root, stop at the base */ | |
173 | base = parent_sd; | |
174 | while (base->s_parent) { | |
175 | sd = target_sd->s_parent; | |
176 | while (sd->s_parent && base != sd) | |
177 | sd = sd->s_parent; | |
178 | ||
179 | if (base == sd) | |
180 | break; | |
181 | ||
182 | strcpy(s, "../"); | |
183 | s += 3; | |
184 | base = base->s_parent; | |
185 | } | |
186 | ||
187 | /* determine end of target string for reverse fillup */ | |
188 | sd = target_sd; | |
189 | while (sd->s_parent && sd != base) { | |
190 | len += strlen(sd->s_name) + 1; | |
191 | sd = sd->s_parent; | |
192 | } | |
1da177e4 | 193 | |
2f90a851 KS |
194 | /* check limits */ |
195 | if (len < 2) | |
196 | return -EINVAL; | |
197 | len--; | |
198 | if ((s - path) + len > PATH_MAX) | |
1da177e4 LT |
199 | return -ENAMETOOLONG; |
200 | ||
2f90a851 KS |
201 | /* reverse fillup of target string from target to base */ |
202 | sd = target_sd; | |
203 | while (sd->s_parent && sd != base) { | |
204 | int slen = strlen(sd->s_name); | |
1da177e4 | 205 | |
2f90a851 KS |
206 | len -= slen; |
207 | strncpy(s + len, sd->s_name, slen); | |
208 | if (len) | |
209 | s[--len] = '/'; | |
1da177e4 | 210 | |
2f90a851 KS |
211 | sd = sd->s_parent; |
212 | } | |
1da177e4 LT |
213 | |
214 | return 0; | |
215 | } | |
216 | ||
217 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
218 | { | |
2b29ac25 TH |
219 | struct sysfs_dirent *sd = dentry->d_fsdata; |
220 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
b1fc3d61 | 221 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; |
2b29ac25 | 222 | int error; |
1da177e4 | 223 | |
3007e997 | 224 | mutex_lock(&sysfs_mutex); |
2b29ac25 | 225 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
3007e997 | 226 | mutex_unlock(&sysfs_mutex); |
1da177e4 | 227 | |
2b29ac25 | 228 | return error; |
1da177e4 LT |
229 | } |
230 | ||
cc314eef | 231 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
232 | { |
233 | int error = -ENOMEM; | |
234 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
557411eb | 235 | if (page) { |
1da177e4 | 236 | error = sysfs_getlink(dentry, (char *) page); |
557411eb AK |
237 | if (error < 0) |
238 | free_page((unsigned long)page); | |
239 | } | |
1da177e4 | 240 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); |
cc314eef | 241 | return NULL; |
1da177e4 LT |
242 | } |
243 | ||
cc314eef | 244 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
245 | { |
246 | char *page = nd_get_link(nd); | |
247 | if (!IS_ERR(page)) | |
248 | free_page((unsigned long)page); | |
249 | } | |
250 | ||
c5ef1c42 | 251 | const struct inode_operations sysfs_symlink_inode_operations = { |
c099aacd EB |
252 | .setxattr = sysfs_setxattr, |
253 | .readlink = generic_readlink, | |
254 | .follow_link = sysfs_follow_link, | |
255 | .put_link = sysfs_put_link, | |
e61ab4ae EB |
256 | .setattr = sysfs_setattr, |
257 | .getattr = sysfs_getattr, | |
258 | .permission = sysfs_permission, | |
1da177e4 LT |
259 | }; |
260 | ||
261 | ||
262 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
263 | EXPORT_SYMBOL_GPL(sysfs_remove_link); | |
e0f43752 | 264 | EXPORT_SYMBOL_GPL(sysfs_rename_link); |