Commit | Line | Data |
---|---|---|
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 | |
3ff195b0 EB |
61 | if (sysfs_ns_type(parent_sd)) |
62 | sd->s_ns = target->ktype->namespace(target); | |
b1fc3d61 | 63 | sd->s_symlink.target_sd = target_sd; |
a1da4dfe | 64 | target_sd = NULL; /* reference is now owned by the symlink */ |
1da177e4 | 65 | |
fb6896da | 66 | sysfs_addrm_start(&acxt, parent_sd); |
36ce6dad CH |
67 | if (warn) |
68 | error = sysfs_add_one(&acxt, sd); | |
69 | else | |
70 | error = __sysfs_add_one(&acxt, sd); | |
23dc2799 | 71 | sysfs_addrm_finish(&acxt); |
2b29ac25 | 72 | |
23dc2799 | 73 | if (error) |
967e35dc | 74 | goto out_put; |
967e35dc TH |
75 | |
76 | return 0; | |
fb6896da | 77 | |
3007e997 TH |
78 | out_put: |
79 | sysfs_put(target_sd); | |
80 | sysfs_put(sd); | |
1da177e4 LT |
81 | return error; |
82 | } | |
83 | ||
36ce6dad CH |
84 | /** |
85 | * sysfs_create_link - create symlink between two objects. | |
86 | * @kobj: object whose directory we're creating the link in. | |
87 | * @target: object we're pointing to. | |
88 | * @name: name of the symlink. | |
89 | */ | |
90 | int sysfs_create_link(struct kobject *kobj, struct kobject *target, | |
91 | const char *name) | |
92 | { | |
93 | return sysfs_do_create_link(kobj, target, name, 1); | |
94 | } | |
95 | ||
96 | /** | |
97 | * sysfs_create_link_nowarn - create symlink between two objects. | |
98 | * @kobj: object whose directory we're creating the link in. | |
99 | * @target: object we're pointing to. | |
100 | * @name: name of the symlink. | |
101 | * | |
102 | * This function does the same as sysf_create_link(), but it | |
103 | * doesn't warn if the link already exists. | |
104 | */ | |
105 | int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, | |
106 | const char *name) | |
107 | { | |
108 | return sysfs_do_create_link(kobj, target, name, 0); | |
109 | } | |
110 | ||
746edb7a EB |
111 | /** |
112 | * sysfs_delete_link - remove symlink in object's directory. | |
113 | * @kobj: object we're acting for. | |
114 | * @targ: object we're pointing to. | |
115 | * @name: name of the symlink to remove. | |
116 | * | |
117 | * Unlike sysfs_remove_link sysfs_delete_link has enough information | |
118 | * to successfully delete symlinks in tagged directories. | |
119 | */ | |
120 | void sysfs_delete_link(struct kobject *kobj, struct kobject *targ, | |
121 | const char *name) | |
122 | { | |
123 | const void *ns = NULL; | |
124 | spin_lock(&sysfs_assoc_lock); | |
125 | if (targ->sd) | |
126 | ns = targ->sd->s_ns; | |
127 | spin_unlock(&sysfs_assoc_lock); | |
128 | sysfs_hash_and_remove(kobj->sd, ns, name); | |
129 | } | |
130 | ||
1da177e4 LT |
131 | /** |
132 | * sysfs_remove_link - remove symlink in object's directory. | |
133 | * @kobj: object we're acting for. | |
134 | * @name: name of the symlink to remove. | |
135 | */ | |
136 | ||
e3a15db2 | 137 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 | 138 | { |
a839c5af MF |
139 | struct sysfs_dirent *parent_sd = NULL; |
140 | ||
141 | if (!kobj) | |
142 | parent_sd = &sysfs_root; | |
143 | else | |
144 | parent_sd = kobj->sd; | |
145 | ||
3ff195b0 | 146 | sysfs_hash_and_remove(parent_sd, NULL, name); |
1da177e4 LT |
147 | } |
148 | ||
7cb32942 EB |
149 | /** |
150 | * sysfs_rename_link - rename symlink in object's directory. | |
151 | * @kobj: object we're acting for. | |
152 | * @targ: object we're pointing to. | |
153 | * @old: previous name of the symlink. | |
154 | * @new: new name of the symlink. | |
155 | * | |
156 | * A helper function for the common rename symlink idiom. | |
157 | */ | |
158 | int sysfs_rename_link(struct kobject *kobj, struct kobject *targ, | |
159 | const char *old, const char *new) | |
160 | { | |
161 | struct sysfs_dirent *parent_sd, *sd = NULL; | |
3ff195b0 | 162 | const void *old_ns = NULL, *new_ns = NULL; |
7cb32942 EB |
163 | int result; |
164 | ||
165 | if (!kobj) | |
166 | parent_sd = &sysfs_root; | |
167 | else | |
168 | parent_sd = kobj->sd; | |
169 | ||
3ff195b0 EB |
170 | if (targ->sd) |
171 | old_ns = targ->sd->s_ns; | |
172 | ||
7cb32942 | 173 | result = -ENOENT; |
3ff195b0 | 174 | sd = sysfs_get_dirent(parent_sd, old_ns, old); |
7cb32942 EB |
175 | if (!sd) |
176 | goto out; | |
177 | ||
178 | result = -EINVAL; | |
179 | if (sysfs_type(sd) != SYSFS_KOBJ_LINK) | |
180 | goto out; | |
181 | if (sd->s_symlink.target_sd->s_dir.kobj != targ) | |
182 | goto out; | |
183 | ||
3ff195b0 EB |
184 | if (sysfs_ns_type(parent_sd)) |
185 | new_ns = targ->ktype->namespace(targ); | |
186 | ||
187 | result = sysfs_rename(sd, parent_sd, new_ns, new); | |
7cb32942 EB |
188 | |
189 | out: | |
190 | sysfs_put(sd); | |
191 | return result; | |
192 | } | |
193 | ||
2f90a851 KS |
194 | static int sysfs_get_target_path(struct sysfs_dirent *parent_sd, |
195 | struct sysfs_dirent *target_sd, char *path) | |
1da177e4 | 196 | { |
2f90a851 KS |
197 | struct sysfs_dirent *base, *sd; |
198 | char *s = path; | |
199 | int len = 0; | |
200 | ||
201 | /* go up to the root, stop at the base */ | |
202 | base = parent_sd; | |
203 | while (base->s_parent) { | |
204 | sd = target_sd->s_parent; | |
205 | while (sd->s_parent && base != sd) | |
206 | sd = sd->s_parent; | |
207 | ||
208 | if (base == sd) | |
209 | break; | |
210 | ||
211 | strcpy(s, "../"); | |
212 | s += 3; | |
213 | base = base->s_parent; | |
214 | } | |
215 | ||
216 | /* determine end of target string for reverse fillup */ | |
217 | sd = target_sd; | |
218 | while (sd->s_parent && sd != base) { | |
219 | len += strlen(sd->s_name) + 1; | |
220 | sd = sd->s_parent; | |
221 | } | |
1da177e4 | 222 | |
2f90a851 KS |
223 | /* check limits */ |
224 | if (len < 2) | |
225 | return -EINVAL; | |
226 | len--; | |
227 | if ((s - path) + len > PATH_MAX) | |
1da177e4 LT |
228 | return -ENAMETOOLONG; |
229 | ||
2f90a851 KS |
230 | /* reverse fillup of target string from target to base */ |
231 | sd = target_sd; | |
232 | while (sd->s_parent && sd != base) { | |
233 | int slen = strlen(sd->s_name); | |
1da177e4 | 234 | |
2f90a851 KS |
235 | len -= slen; |
236 | strncpy(s + len, sd->s_name, slen); | |
237 | if (len) | |
238 | s[--len] = '/'; | |
1da177e4 | 239 | |
2f90a851 KS |
240 | sd = sd->s_parent; |
241 | } | |
1da177e4 LT |
242 | |
243 | return 0; | |
244 | } | |
245 | ||
246 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
247 | { | |
2b29ac25 TH |
248 | struct sysfs_dirent *sd = dentry->d_fsdata; |
249 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
b1fc3d61 | 250 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; |
2b29ac25 | 251 | int error; |
1da177e4 | 252 | |
3007e997 | 253 | mutex_lock(&sysfs_mutex); |
2b29ac25 | 254 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
3007e997 | 255 | mutex_unlock(&sysfs_mutex); |
1da177e4 | 256 | |
2b29ac25 | 257 | return error; |
1da177e4 LT |
258 | } |
259 | ||
cc314eef | 260 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
261 | { |
262 | int error = -ENOMEM; | |
263 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
557411eb | 264 | if (page) { |
1da177e4 | 265 | error = sysfs_getlink(dentry, (char *) page); |
557411eb AK |
266 | if (error < 0) |
267 | free_page((unsigned long)page); | |
268 | } | |
1da177e4 | 269 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); |
cc314eef | 270 | return NULL; |
1da177e4 LT |
271 | } |
272 | ||
cc314eef | 273 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
274 | { |
275 | char *page = nd_get_link(nd); | |
276 | if (!IS_ERR(page)) | |
277 | free_page((unsigned long)page); | |
278 | } | |
279 | ||
c5ef1c42 | 280 | const struct inode_operations sysfs_symlink_inode_operations = { |
c099aacd EB |
281 | .setxattr = sysfs_setxattr, |
282 | .readlink = generic_readlink, | |
283 | .follow_link = sysfs_follow_link, | |
284 | .put_link = sysfs_put_link, | |
e61ab4ae EB |
285 | .setattr = sysfs_setattr, |
286 | .getattr = sysfs_getattr, | |
287 | .permission = sysfs_permission, | |
1da177e4 LT |
288 | }; |
289 | ||
290 | ||
291 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
292 | EXPORT_SYMBOL_GPL(sysfs_remove_link); | |
e0f43752 | 293 | EXPORT_SYMBOL_GPL(sysfs_rename_link); |