blob: 3c9eb5624f5e195d6e2b06908f3b21396ccc8723 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Tejun Heo6d66f5c2007-09-20 17:31:38 +09002 * 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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 */
12
13#include <linux/fs.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090014#include <linux/gfp.h>
Greg Kroah-Hartmanceeee1f2002-04-09 12:14:34 -070015#include <linux/mount.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#include <linux/module.h>
17#include <linux/kobject.h>
18#include <linux/namei.h>
Dave Young869512a2007-07-26 14:53:53 +000019#include <linux/mutex.h>
David P. Quigleyddd29ec2009-09-09 14:25:37 -040020#include <linux/security.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
22#include "sysfs.h"
23
Cornelia Huck36ce6da2008-06-10 11:09:08 +020024static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
25 const char *name, int warn)
Linus Torvalds1da177e2005-04-16 15:20:36 -070026{
Tejun Heo2b29ac22007-06-14 03:45:15 +090027 struct sysfs_dirent *parent_sd = NULL;
28 struct sysfs_dirent *target_sd = NULL;
Tejun Heo3007e992007-06-14 04:27:23 +090029 struct sysfs_dirent *sd = NULL;
Tejun Heofb6896d2007-06-14 04:27:24 +090030 struct sysfs_addrm_cxt acxt;
Eric W. Biederman96d65232010-07-08 09:31:24 -070031 enum kobj_ns_type ns_type;
Tejun Heo3007e992007-06-14 04:27:23 +090032 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -070033
Greg Kroah-Hartmanceeee1f2002-04-09 12:14:34 -070034 BUG_ON(!name);
35
Eric W. Biederman7d0c7d62007-08-20 21:36:30 +090036 if (!kobj)
37 parent_sd = &sysfs_root;
38 else
Tejun Heo608e2662007-06-14 04:27:22 +090039 parent_sd = kobj->sd;
Greg Kroah-Hartmanceeee1f2002-04-09 12:14:34 -070040
Tejun Heo3007e992007-06-14 04:27:23 +090041 error = -EFAULT;
Tejun Heo608e2662007-06-14 04:27:22 +090042 if (!parent_sd)
Tejun Heo3007e992007-06-14 04:27:23 +090043 goto out_put;
Tejun Heo2b29ac22007-06-14 03:45:15 +090044
Tejun Heo608e2662007-06-14 04:27:22 +090045 /* target->sd can go away beneath us but is protected with
Tejun Heo5f995322007-06-14 04:27:23 +090046 * sysfs_assoc_lock. Fetch target_sd from it.
Tejun Heo2b29ac22007-06-14 03:45:15 +090047 */
Tejun Heo5f995322007-06-14 04:27:23 +090048 spin_lock(&sysfs_assoc_lock);
Tejun Heo608e2662007-06-14 04:27:22 +090049 if (target->sd)
50 target_sd = sysfs_get(target->sd);
Tejun Heo5f995322007-06-14 04:27:23 +090051 spin_unlock(&sysfs_assoc_lock);
Tejun Heo2b29ac22007-06-14 03:45:15 +090052
Tejun Heo3007e992007-06-14 04:27:23 +090053 error = -ENOENT;
Tejun Heo2b29ac22007-06-14 03:45:15 +090054 if (!target_sd)
Tejun Heo3007e992007-06-14 04:27:23 +090055 goto out_put;
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
Tejun Heo3007e992007-06-14 04:27:23 +090057 error = -ENOMEM;
58 sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
59 if (!sd)
60 goto out_put;
Tejun Heoa1da4df2007-07-18 16:14:45 +090061
Eric W. Biederman96d65232010-07-08 09:31:24 -070062 ns_type = sysfs_ns_type(parent_sd);
63 if (ns_type)
Eric W. Biederman3ff195b2010-03-30 11:31:26 -070064 sd->s_ns = target->ktype->namespace(target);
Tejun Heob1fc3d62007-09-20 16:05:11 +090065 sd->s_symlink.target_sd = target_sd;
Tejun Heoa1da4df2007-07-18 16:14:45 +090066 target_sd = NULL; /* reference is now owned by the symlink */
Tejun Heo2b29ac22007-06-14 03:45:15 +090067
Tejun Heofb6896d2007-06-14 04:27:24 +090068 sysfs_addrm_start(&acxt, parent_sd);
Eric W. Biederman96d65232010-07-08 09:31:24 -070069 /* Symlinks must be between directories with the same ns_type */
Eric W. Biedermand3300212010-07-20 22:12:01 -070070 if (!ns_type ||
71 (ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent))) {
Eric W. Biederman96d65232010-07-08 09:31:24 -070072 if (warn)
73 error = sysfs_add_one(&acxt, sd);
74 else
75 error = __sysfs_add_one(&acxt, sd);
76 } else {
77 error = -EINVAL;
78 WARN(1, KERN_WARNING
79 "sysfs: symlink across ns_types %s/%s -> %s/%s\n",
80 parent_sd->s_name,
81 sd->s_name,
82 sd->s_symlink.target_sd->s_parent->s_name,
83 sd->s_symlink.target_sd->s_name);
84 }
Tejun Heo23dc2792007-08-02 21:38:03 +090085 sysfs_addrm_finish(&acxt);
Tejun Heofb6896d2007-06-14 04:27:24 +090086
Tejun Heo23dc2792007-08-02 21:38:03 +090087 if (error)
Tejun Heo967e35d2007-07-18 16:38:11 +090088 goto out_put;
Tejun Heofb6896d2007-06-14 04:27:24 +090089
Tejun Heo967e35d2007-07-18 16:38:11 +090090 return 0;
91
Tejun Heo3007e992007-06-14 04:27:23 +090092 out_put:
93 sysfs_put(target_sd);
94 sysfs_put(sd);
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 return error;
96}
97
Linus Torvalds1da177e2005-04-16 15:20:36 -070098/**
Cornelia Huck36ce6da2008-06-10 11:09:08 +020099 * sysfs_create_link - create symlink between two objects.
100 * @kobj: object whose directory we're creating the link in.
101 * @target: object we're pointing to.
102 * @name: name of the symlink.
103 */
104int sysfs_create_link(struct kobject *kobj, struct kobject *target,
105 const char *name)
106{
107 return sysfs_do_create_link(kobj, target, name, 1);
108}
109
110/**
111 * sysfs_create_link_nowarn - create symlink between two objects.
112 * @kobj: object whose directory we're creating the link in.
113 * @target: object we're pointing to.
114 * @name: name of the symlink.
115 *
Robert P. J. Day6f1cbd42012-09-04 07:23:35 -0400116 * This function does the same as sysfs_create_link(), but it
Cornelia Huck36ce6da2008-06-10 11:09:08 +0200117 * doesn't warn if the link already exists.
118 */
119int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
120 const char *name)
121{
122 return sysfs_do_create_link(kobj, target, name, 0);
123}
124
125/**
Eric W. Biederman746edb72010-03-30 11:31:28 -0700126 * sysfs_delete_link - remove symlink in object's directory.
127 * @kobj: object we're acting for.
128 * @targ: object we're pointing to.
129 * @name: name of the symlink to remove.
130 *
131 * Unlike sysfs_remove_link sysfs_delete_link has enough information
132 * to successfully delete symlinks in tagged directories.
133 */
134void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
135 const char *name)
136{
137 const void *ns = NULL;
138 spin_lock(&sysfs_assoc_lock);
Eric W. Biederman521d0452010-07-20 22:10:58 -0700139 if (targ->sd && sysfs_ns_type(kobj->sd))
Eric W. Biederman746edb72010-03-30 11:31:28 -0700140 ns = targ->sd->s_ns;
141 spin_unlock(&sysfs_assoc_lock);
142 sysfs_hash_and_remove(kobj->sd, ns, name);
143}
144
145/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146 * sysfs_remove_link - remove symlink in object's directory.
147 * @kobj: object we're acting for.
148 * @name: name of the symlink to remove.
149 */
150
Dmitry Torokhove3a15db2005-04-26 02:31:08 -0500151void sysfs_remove_link(struct kobject * kobj, const char * name)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152{
Mark Fasheha839c5a2008-01-29 14:35:18 -0800153 struct sysfs_dirent *parent_sd = NULL;
154
155 if (!kobj)
156 parent_sd = &sysfs_root;
157 else
158 parent_sd = kobj->sd;
159
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700160 sysfs_hash_and_remove(parent_sd, NULL, name);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161}
162
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800163/**
164 * sysfs_rename_link - rename symlink in object's directory.
165 * @kobj: object we're acting for.
166 * @targ: object we're pointing to.
167 * @old: previous name of the symlink.
168 * @new: new name of the symlink.
169 *
170 * A helper function for the common rename symlink idiom.
171 */
172int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
173 const char *old, const char *new)
174{
175 struct sysfs_dirent *parent_sd, *sd = NULL;
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700176 const void *old_ns = NULL, *new_ns = NULL;
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800177 int result;
178
179 if (!kobj)
180 parent_sd = &sysfs_root;
181 else
182 parent_sd = kobj->sd;
183
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700184 if (targ->sd)
185 old_ns = targ->sd->s_ns;
186
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800187 result = -ENOENT;
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700188 sd = sysfs_get_dirent(parent_sd, old_ns, old);
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800189 if (!sd)
190 goto out;
191
192 result = -EINVAL;
193 if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
194 goto out;
195 if (sd->s_symlink.target_sd->s_dir.kobj != targ)
196 goto out;
197
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700198 if (sysfs_ns_type(parent_sd))
199 new_ns = targ->ktype->namespace(targ);
200
201 result = sysfs_rename(sd, parent_sd, new_ns, new);
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800202
203out:
204 sysfs_put(sd);
205 return result;
206}
207
Kay Sievers2f90a852007-11-01 20:20:52 +0100208static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
209 struct sysfs_dirent *target_sd, char *path)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210{
Kay Sievers2f90a852007-11-01 20:20:52 +0100211 struct sysfs_dirent *base, *sd;
212 char *s = path;
213 int len = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
Kay Sievers2f90a852007-11-01 20:20:52 +0100215 /* go up to the root, stop at the base */
216 base = parent_sd;
217 while (base->s_parent) {
218 sd = target_sd->s_parent;
219 while (sd->s_parent && base != sd)
220 sd = sd->s_parent;
221
222 if (base == sd)
223 break;
224
225 strcpy(s, "../");
226 s += 3;
227 base = base->s_parent;
228 }
229
230 /* determine end of target string for reverse fillup */
231 sd = target_sd;
232 while (sd->s_parent && sd != base) {
233 len += strlen(sd->s_name) + 1;
234 sd = sd->s_parent;
235 }
236
237 /* check limits */
238 if (len < 2)
239 return -EINVAL;
240 len--;
241 if ((s - path) + len > PATH_MAX)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 return -ENAMETOOLONG;
243
Kay Sievers2f90a852007-11-01 20:20:52 +0100244 /* reverse fillup of target string from target to base */
245 sd = target_sd;
246 while (sd->s_parent && sd != base) {
247 int slen = strlen(sd->s_name);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700248
Kay Sievers2f90a852007-11-01 20:20:52 +0100249 len -= slen;
250 strncpy(s + len, sd->s_name, slen);
251 if (len)
252 s[--len] = '/';
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253
Kay Sievers2f90a852007-11-01 20:20:52 +0100254 sd = sd->s_parent;
255 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256
257 return 0;
258}
259
260static int sysfs_getlink(struct dentry *dentry, char * path)
261{
Tejun Heo2b29ac22007-06-14 03:45:15 +0900262 struct sysfs_dirent *sd = dentry->d_fsdata;
263 struct sysfs_dirent *parent_sd = sd->s_parent;
Tejun Heob1fc3d62007-09-20 16:05:11 +0900264 struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
Tejun Heo2b29ac22007-06-14 03:45:15 +0900265 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266
Tejun Heo3007e992007-06-14 04:27:23 +0900267 mutex_lock(&sysfs_mutex);
Tejun Heo2b29ac22007-06-14 03:45:15 +0900268 error = sysfs_get_target_path(parent_sd, target_sd, path);
Tejun Heo3007e992007-06-14 04:27:23 +0900269 mutex_unlock(&sysfs_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270
Tejun Heo2b29ac22007-06-14 03:45:15 +0900271 return error;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700272}
273
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700274static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275{
276 int error = -ENOMEM;
277 unsigned long page = get_zeroed_page(GFP_KERNEL);
Armin Kuster557411e2009-04-29 07:29:59 -1000278 if (page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700279 error = sysfs_getlink(dentry, (char *) page);
Armin Kuster557411e2009-04-29 07:29:59 -1000280 if (error < 0)
281 free_page((unsigned long)page);
282 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700283 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700284 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285}
286
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700287static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288{
289 char *page = nd_get_link(nd);
290 if (!IS_ERR(page))
291 free_page((unsigned long)page);
292}
293
Arjan van de Venc5ef1c42007-02-12 00:55:40 -0800294const struct inode_operations sysfs_symlink_inode_operations = {
Eric W. Biedermanc099aac2009-11-20 16:08:52 -0800295 .setxattr = sysfs_setxattr,
296 .readlink = generic_readlink,
297 .follow_link = sysfs_follow_link,
298 .put_link = sysfs_put_link,
Eric W. Biedermane61ab4a2009-11-20 16:08:53 -0800299 .setattr = sysfs_setattr,
300 .getattr = sysfs_getattr,
301 .permission = sysfs_permission,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700302};
303
304
305EXPORT_SYMBOL_GPL(sysfs_create_link);
306EXPORT_SYMBOL_GPL(sysfs_remove_link);
Simon Arlotte0f43752010-05-10 09:31:11 +0000307EXPORT_SYMBOL_GPL(sysfs_rename_link);