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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 | ||
0bb8f3d6 RW |
24 | static int sysfs_do_create_link_sd(struct sysfs_dirent *parent_sd, |
25 | struct kobject *target, | |
26 | const char *name, int warn) | |
1da177e4 | 27 | { |
2b29ac25 | 28 | struct sysfs_dirent *target_sd = NULL; |
3007e997 | 29 | struct sysfs_dirent *sd = NULL; |
fb6896da | 30 | struct sysfs_addrm_cxt acxt; |
96d6523a | 31 | enum kobj_ns_type ns_type; |
3007e997 | 32 | int error; |
1da177e4 | 33 | |
0bb8f3d6 | 34 | BUG_ON(!name || !parent_sd); |
2b29ac25 | 35 | |
608e266a | 36 | /* target->sd can go away beneath us but is protected with |
5f995323 | 37 | * sysfs_assoc_lock. Fetch target_sd from it. |
2b29ac25 | 38 | */ |
5f995323 | 39 | spin_lock(&sysfs_assoc_lock); |
608e266a TH |
40 | if (target->sd) |
41 | target_sd = sysfs_get(target->sd); | |
5f995323 | 42 | spin_unlock(&sysfs_assoc_lock); |
2b29ac25 | 43 | |
3007e997 | 44 | error = -ENOENT; |
2b29ac25 | 45 | if (!target_sd) |
3007e997 TH |
46 | goto out_put; |
47 | ||
48 | error = -ENOMEM; | |
49 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); | |
50 | if (!sd) | |
51 | goto out_put; | |
a1da4dfe | 52 | |
96d6523a EB |
53 | ns_type = sysfs_ns_type(parent_sd); |
54 | if (ns_type) | |
3ff195b0 | 55 | sd->s_ns = target->ktype->namespace(target); |
b1fc3d61 | 56 | sd->s_symlink.target_sd = target_sd; |
a1da4dfe | 57 | target_sd = NULL; /* reference is now owned by the symlink */ |
1da177e4 | 58 | |
fb6896da | 59 | sysfs_addrm_start(&acxt, parent_sd); |
96d6523a | 60 | /* Symlinks must be between directories with the same ns_type */ |
d3300212 EB |
61 | if (!ns_type || |
62 | (ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent))) { | |
96d6523a EB |
63 | if (warn) |
64 | error = sysfs_add_one(&acxt, sd); | |
65 | else | |
66 | error = __sysfs_add_one(&acxt, sd); | |
67 | } else { | |
68 | error = -EINVAL; | |
69 | WARN(1, KERN_WARNING | |
70 | "sysfs: symlink across ns_types %s/%s -> %s/%s\n", | |
71 | parent_sd->s_name, | |
72 | sd->s_name, | |
73 | sd->s_symlink.target_sd->s_parent->s_name, | |
74 | sd->s_symlink.target_sd->s_name); | |
75 | } | |
23dc2799 | 76 | sysfs_addrm_finish(&acxt); |
2b29ac25 | 77 | |
23dc2799 | 78 | if (error) |
967e35dc | 79 | goto out_put; |
967e35dc TH |
80 | |
81 | return 0; | |
fb6896da | 82 | |
3007e997 TH |
83 | out_put: |
84 | sysfs_put(target_sd); | |
85 | sysfs_put(sd); | |
1da177e4 LT |
86 | return error; |
87 | } | |
88 | ||
0bb8f3d6 RW |
89 | /** |
90 | * sysfs_create_link_sd - create symlink to a given object. | |
91 | * @sd: directory we're creating the link in. | |
92 | * @target: object we're pointing to. | |
93 | * @name: name of the symlink. | |
94 | */ | |
95 | int sysfs_create_link_sd(struct sysfs_dirent *sd, struct kobject *target, | |
96 | const char *name) | |
97 | { | |
98 | return sysfs_do_create_link_sd(sd, target, name, 1); | |
99 | } | |
100 | ||
101 | static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, | |
102 | const char *name, int warn) | |
103 | { | |
104 | struct sysfs_dirent *parent_sd = NULL; | |
105 | ||
106 | if (!kobj) | |
107 | parent_sd = &sysfs_root; | |
108 | else | |
109 | parent_sd = kobj->sd; | |
110 | ||
111 | if (!parent_sd) | |
112 | return -EFAULT; | |
113 | ||
114 | return sysfs_do_create_link_sd(parent_sd, target, name, warn); | |
115 | } | |
116 | ||
36ce6dad CH |
117 | /** |
118 | * sysfs_create_link - create symlink between two objects. | |
119 | * @kobj: object whose directory we're creating the link in. | |
120 | * @target: object we're pointing to. | |
121 | * @name: name of the symlink. | |
122 | */ | |
123 | int sysfs_create_link(struct kobject *kobj, struct kobject *target, | |
124 | const char *name) | |
125 | { | |
126 | return sysfs_do_create_link(kobj, target, name, 1); | |
127 | } | |
1b866757 | 128 | EXPORT_SYMBOL_GPL(sysfs_create_link); |
36ce6dad CH |
129 | |
130 | /** | |
131 | * sysfs_create_link_nowarn - create symlink between two objects. | |
132 | * @kobj: object whose directory we're creating the link in. | |
133 | * @target: object we're pointing to. | |
134 | * @name: name of the symlink. | |
135 | * | |
6f1cbd4a | 136 | * This function does the same as sysfs_create_link(), but it |
36ce6dad CH |
137 | * doesn't warn if the link already exists. |
138 | */ | |
139 | int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, | |
140 | const char *name) | |
141 | { | |
142 | return sysfs_do_create_link(kobj, target, name, 0); | |
143 | } | |
144 | ||
746edb7a EB |
145 | /** |
146 | * sysfs_delete_link - remove symlink in object's directory. | |
147 | * @kobj: object we're acting for. | |
148 | * @targ: object we're pointing to. | |
149 | * @name: name of the symlink to remove. | |
150 | * | |
151 | * Unlike sysfs_remove_link sysfs_delete_link has enough information | |
152 | * to successfully delete symlinks in tagged directories. | |
153 | */ | |
154 | void sysfs_delete_link(struct kobject *kobj, struct kobject *targ, | |
155 | const char *name) | |
156 | { | |
157 | const void *ns = NULL; | |
158 | spin_lock(&sysfs_assoc_lock); | |
521d0453 | 159 | if (targ->sd && sysfs_ns_type(kobj->sd)) |
746edb7a EB |
160 | ns = targ->sd->s_ns; |
161 | spin_unlock(&sysfs_assoc_lock); | |
162 | sysfs_hash_and_remove(kobj->sd, ns, name); | |
163 | } | |
164 | ||
1da177e4 LT |
165 | /** |
166 | * sysfs_remove_link - remove symlink in object's directory. | |
167 | * @kobj: object we're acting for. | |
168 | * @name: name of the symlink to remove. | |
169 | */ | |
1b18dc2b | 170 | void sysfs_remove_link(struct kobject *kobj, const char *name) |
1da177e4 | 171 | { |
a839c5af MF |
172 | struct sysfs_dirent *parent_sd = NULL; |
173 | ||
174 | if (!kobj) | |
175 | parent_sd = &sysfs_root; | |
176 | else | |
177 | parent_sd = kobj->sd; | |
178 | ||
3ff195b0 | 179 | sysfs_hash_and_remove(parent_sd, NULL, name); |
1da177e4 | 180 | } |
1b866757 | 181 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |
1da177e4 | 182 | |
7cb32942 EB |
183 | /** |
184 | * sysfs_rename_link - rename symlink in object's directory. | |
185 | * @kobj: object we're acting for. | |
186 | * @targ: object we're pointing to. | |
187 | * @old: previous name of the symlink. | |
188 | * @new: new name of the symlink. | |
189 | * | |
190 | * A helper function for the common rename symlink idiom. | |
191 | */ | |
192 | int sysfs_rename_link(struct kobject *kobj, struct kobject *targ, | |
193 | const char *old, const char *new) | |
194 | { | |
195 | struct sysfs_dirent *parent_sd, *sd = NULL; | |
3ff195b0 | 196 | const void *old_ns = NULL, *new_ns = NULL; |
7cb32942 EB |
197 | int result; |
198 | ||
199 | if (!kobj) | |
200 | parent_sd = &sysfs_root; | |
201 | else | |
202 | parent_sd = kobj->sd; | |
203 | ||
3ff195b0 EB |
204 | if (targ->sd) |
205 | old_ns = targ->sd->s_ns; | |
206 | ||
7cb32942 | 207 | result = -ENOENT; |
3ff195b0 | 208 | sd = sysfs_get_dirent(parent_sd, old_ns, old); |
7cb32942 EB |
209 | if (!sd) |
210 | goto out; | |
211 | ||
212 | result = -EINVAL; | |
213 | if (sysfs_type(sd) != SYSFS_KOBJ_LINK) | |
214 | goto out; | |
215 | if (sd->s_symlink.target_sd->s_dir.kobj != targ) | |
216 | goto out; | |
217 | ||
3ff195b0 EB |
218 | if (sysfs_ns_type(parent_sd)) |
219 | new_ns = targ->ktype->namespace(targ); | |
220 | ||
221 | result = sysfs_rename(sd, parent_sd, new_ns, new); | |
7cb32942 EB |
222 | |
223 | out: | |
224 | sysfs_put(sd); | |
225 | return result; | |
226 | } | |
1b866757 | 227 | EXPORT_SYMBOL_GPL(sysfs_rename_link); |
7cb32942 | 228 | |
2f90a851 KS |
229 | static int sysfs_get_target_path(struct sysfs_dirent *parent_sd, |
230 | struct sysfs_dirent *target_sd, char *path) | |
1da177e4 | 231 | { |
2f90a851 KS |
232 | struct sysfs_dirent *base, *sd; |
233 | char *s = path; | |
234 | int len = 0; | |
235 | ||
236 | /* go up to the root, stop at the base */ | |
237 | base = parent_sd; | |
238 | while (base->s_parent) { | |
239 | sd = target_sd->s_parent; | |
240 | while (sd->s_parent && base != sd) | |
241 | sd = sd->s_parent; | |
242 | ||
243 | if (base == sd) | |
244 | break; | |
245 | ||
246 | strcpy(s, "../"); | |
247 | s += 3; | |
248 | base = base->s_parent; | |
249 | } | |
250 | ||
251 | /* determine end of target string for reverse fillup */ | |
252 | sd = target_sd; | |
253 | while (sd->s_parent && sd != base) { | |
254 | len += strlen(sd->s_name) + 1; | |
255 | sd = sd->s_parent; | |
256 | } | |
1da177e4 | 257 | |
2f90a851 KS |
258 | /* check limits */ |
259 | if (len < 2) | |
260 | return -EINVAL; | |
261 | len--; | |
262 | if ((s - path) + len > PATH_MAX) | |
1da177e4 LT |
263 | return -ENAMETOOLONG; |
264 | ||
2f90a851 KS |
265 | /* reverse fillup of target string from target to base */ |
266 | sd = target_sd; | |
267 | while (sd->s_parent && sd != base) { | |
268 | int slen = strlen(sd->s_name); | |
1da177e4 | 269 | |
2f90a851 KS |
270 | len -= slen; |
271 | strncpy(s + len, sd->s_name, slen); | |
272 | if (len) | |
273 | s[--len] = '/'; | |
1da177e4 | 274 | |
2f90a851 KS |
275 | sd = sd->s_parent; |
276 | } | |
1da177e4 LT |
277 | |
278 | return 0; | |
279 | } | |
280 | ||
1b18dc2b | 281 | static int sysfs_getlink(struct dentry *dentry, char *path) |
1da177e4 | 282 | { |
2b29ac25 TH |
283 | struct sysfs_dirent *sd = dentry->d_fsdata; |
284 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
b1fc3d61 | 285 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; |
2b29ac25 | 286 | int error; |
1da177e4 | 287 | |
3007e997 | 288 | mutex_lock(&sysfs_mutex); |
2b29ac25 | 289 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
3007e997 | 290 | mutex_unlock(&sysfs_mutex); |
1da177e4 | 291 | |
2b29ac25 | 292 | return error; |
1da177e4 LT |
293 | } |
294 | ||
cc314eef | 295 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
296 | { |
297 | int error = -ENOMEM; | |
298 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
557411eb | 299 | if (page) { |
ab9bf4be | 300 | error = sysfs_getlink(dentry, (char *) page); |
557411eb AK |
301 | if (error < 0) |
302 | free_page((unsigned long)page); | |
303 | } | |
1da177e4 | 304 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); |
cc314eef | 305 | return NULL; |
1da177e4 LT |
306 | } |
307 | ||
ddfd6d07 GKH |
308 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, |
309 | void *cookie) | |
1da177e4 LT |
310 | { |
311 | char *page = nd_get_link(nd); | |
312 | if (!IS_ERR(page)) | |
313 | free_page((unsigned long)page); | |
314 | } | |
315 | ||
c5ef1c42 | 316 | const struct inode_operations sysfs_symlink_inode_operations = { |
c099aacd EB |
317 | .setxattr = sysfs_setxattr, |
318 | .readlink = generic_readlink, | |
319 | .follow_link = sysfs_follow_link, | |
320 | .put_link = sysfs_put_link, | |
e61ab4ae EB |
321 | .setattr = sysfs_setattr, |
322 | .getattr = sysfs_getattr, | |
323 | .permission = sysfs_permission, | |
1da177e4 | 324 | }; |