2 * fs/sysfs/symlink.c - sysfs symlink implementation
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8 * This file is released under the GPLv2.
10 * Please see Documentation/filesystems/sysfs.txt for more information.
14 #include <linux/gfp.h>
15 #include <linux/mount.h>
16 #include <linux/module.h>
17 #include <linux/kobject.h>
18 #include <linux/namei.h>
19 #include <linux/mutex.h>
20 #include <linux/security.h>
24 static int sysfs_do_create_link_sd(struct sysfs_dirent
*parent_sd
,
25 struct kobject
*target
,
26 const char *name
, int warn
)
28 struct sysfs_dirent
*target_sd
= NULL
;
29 struct sysfs_dirent
*sd
= NULL
;
30 struct sysfs_addrm_cxt acxt
;
31 enum kobj_ns_type ns_type
;
34 BUG_ON(!name
|| !parent_sd
);
37 * We don't own @target and it may be removed at any time.
38 * Synchronize using sysfs_symlink_target_lock. See
39 * sysfs_remove_dir() for details.
41 spin_lock(&sysfs_symlink_target_lock
);
43 target_sd
= sysfs_get(target
->sd
);
44 spin_unlock(&sysfs_symlink_target_lock
);
51 sd
= sysfs_new_dirent(name
, S_IFLNK
|S_IRWXUGO
, SYSFS_KOBJ_LINK
);
55 ns_type
= sysfs_ns_type(parent_sd
);
57 sd
->s_ns
= target_sd
->s_ns
;
58 sd
->s_symlink
.target_sd
= target_sd
;
59 target_sd
= NULL
; /* reference is now owned by the symlink */
61 sysfs_addrm_start(&acxt
);
62 /* Symlinks must be between directories with the same ns_type */
64 (ns_type
== sysfs_ns_type(sd
->s_symlink
.target_sd
->s_parent
))) {
66 error
= sysfs_add_one(&acxt
, sd
, parent_sd
);
68 error
= __sysfs_add_one(&acxt
, sd
, parent_sd
);
72 "sysfs: symlink across ns_types %s/%s -> %s/%s\n",
75 sd
->s_symlink
.target_sd
->s_parent
->s_name
,
76 sd
->s_symlink
.target_sd
->s_name
);
78 sysfs_addrm_finish(&acxt
);
92 * sysfs_create_link_sd - create symlink to a given object.
93 * @sd: directory we're creating the link in.
94 * @target: object we're pointing to.
95 * @name: name of the symlink.
97 int sysfs_create_link_sd(struct sysfs_dirent
*sd
, struct kobject
*target
,
100 return sysfs_do_create_link_sd(sd
, target
, name
, 1);
103 static int sysfs_do_create_link(struct kobject
*kobj
, struct kobject
*target
,
104 const char *name
, int warn
)
106 struct sysfs_dirent
*parent_sd
= NULL
;
109 parent_sd
= &sysfs_root
;
111 parent_sd
= kobj
->sd
;
116 return sysfs_do_create_link_sd(parent_sd
, target
, name
, warn
);
120 * sysfs_create_link - create symlink between two objects.
121 * @kobj: object whose directory we're creating the link in.
122 * @target: object we're pointing to.
123 * @name: name of the symlink.
125 int sysfs_create_link(struct kobject
*kobj
, struct kobject
*target
,
128 return sysfs_do_create_link(kobj
, target
, name
, 1);
130 EXPORT_SYMBOL_GPL(sysfs_create_link
);
133 * sysfs_create_link_nowarn - create symlink between two objects.
134 * @kobj: object whose directory we're creating the link in.
135 * @target: object we're pointing to.
136 * @name: name of the symlink.
138 * This function does the same as sysfs_create_link(), but it
139 * doesn't warn if the link already exists.
141 int sysfs_create_link_nowarn(struct kobject
*kobj
, struct kobject
*target
,
144 return sysfs_do_create_link(kobj
, target
, name
, 0);
148 * sysfs_delete_link - remove symlink in object's directory.
149 * @kobj: object we're acting for.
150 * @targ: object we're pointing to.
151 * @name: name of the symlink to remove.
153 * Unlike sysfs_remove_link sysfs_delete_link has enough information
154 * to successfully delete symlinks in tagged directories.
156 void sysfs_delete_link(struct kobject
*kobj
, struct kobject
*targ
,
159 const void *ns
= NULL
;
162 * We don't own @target and it may be removed at any time.
163 * Synchronize using sysfs_symlink_target_lock. See
164 * sysfs_remove_dir() for details.
166 spin_lock(&sysfs_symlink_target_lock
);
167 if (targ
->sd
&& sysfs_ns_type(kobj
->sd
))
169 spin_unlock(&sysfs_symlink_target_lock
);
170 sysfs_hash_and_remove(kobj
->sd
, name
, ns
);
174 * sysfs_remove_link - remove symlink in object's directory.
175 * @kobj: object we're acting for.
176 * @name: name of the symlink to remove.
178 void sysfs_remove_link(struct kobject
*kobj
, const char *name
)
180 struct sysfs_dirent
*parent_sd
= NULL
;
183 parent_sd
= &sysfs_root
;
185 parent_sd
= kobj
->sd
;
187 sysfs_hash_and_remove(parent_sd
, name
, NULL
);
189 EXPORT_SYMBOL_GPL(sysfs_remove_link
);
192 * sysfs_rename_link_ns - rename symlink in object's directory.
193 * @kobj: object we're acting for.
194 * @targ: object we're pointing to.
195 * @old: previous name of the symlink.
196 * @new: new name of the symlink.
197 * @new_ns: new namespace of the symlink.
199 * A helper function for the common rename symlink idiom.
201 int sysfs_rename_link_ns(struct kobject
*kobj
, struct kobject
*targ
,
202 const char *old
, const char *new, const void *new_ns
)
204 struct sysfs_dirent
*parent_sd
, *sd
= NULL
;
205 const void *old_ns
= NULL
;
209 parent_sd
= &sysfs_root
;
211 parent_sd
= kobj
->sd
;
214 old_ns
= targ
->sd
->s_ns
;
217 sd
= sysfs_get_dirent_ns(parent_sd
, old
, old_ns
);
222 if (sysfs_type(sd
) != SYSFS_KOBJ_LINK
)
224 if (sd
->s_symlink
.target_sd
->s_dir
.kobj
!= targ
)
227 result
= sysfs_rename(sd
, parent_sd
, new, new_ns
);
233 EXPORT_SYMBOL_GPL(sysfs_rename_link_ns
);
235 static int sysfs_get_target_path(struct sysfs_dirent
*parent_sd
,
236 struct sysfs_dirent
*target_sd
, char *path
)
238 struct sysfs_dirent
*base
, *sd
;
242 /* go up to the root, stop at the base */
244 while (base
->s_parent
) {
245 sd
= target_sd
->s_parent
;
246 while (sd
->s_parent
&& base
!= sd
)
254 base
= base
->s_parent
;
257 /* determine end of target string for reverse fillup */
259 while (sd
->s_parent
&& sd
!= base
) {
260 len
+= strlen(sd
->s_name
) + 1;
268 if ((s
- path
) + len
> PATH_MAX
)
269 return -ENAMETOOLONG
;
271 /* reverse fillup of target string from target to base */
273 while (sd
->s_parent
&& sd
!= base
) {
274 int slen
= strlen(sd
->s_name
);
277 strncpy(s
+ len
, sd
->s_name
, slen
);
287 static int sysfs_getlink(struct dentry
*dentry
, char *path
)
289 struct sysfs_dirent
*sd
= dentry
->d_fsdata
;
290 struct sysfs_dirent
*parent_sd
= sd
->s_parent
;
291 struct sysfs_dirent
*target_sd
= sd
->s_symlink
.target_sd
;
294 mutex_lock(&sysfs_mutex
);
295 error
= sysfs_get_target_path(parent_sd
, target_sd
, path
);
296 mutex_unlock(&sysfs_mutex
);
301 static void *sysfs_follow_link(struct dentry
*dentry
, struct nameidata
*nd
)
304 unsigned long page
= get_zeroed_page(GFP_KERNEL
);
306 error
= sysfs_getlink(dentry
, (char *) page
);
308 free_page((unsigned long)page
);
310 nd_set_link(nd
, error
? ERR_PTR(error
) : (char *)page
);
314 static void sysfs_put_link(struct dentry
*dentry
, struct nameidata
*nd
,
317 char *page
= nd_get_link(nd
);
319 free_page((unsigned long)page
);
322 const struct inode_operations sysfs_symlink_inode_operations
= {
323 .setxattr
= sysfs_setxattr
,
324 .readlink
= generic_readlink
,
325 .follow_link
= sysfs_follow_link
,
326 .put_link
= sysfs_put_link
,
327 .setattr
= sysfs_setattr
,
328 .getattr
= sysfs_getattr
,
329 .permission
= sysfs_permission
,