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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> | |
ceeee1fb | 14 | #include <linux/mount.h> |
1da177e4 LT |
15 | #include <linux/module.h> |
16 | #include <linux/kobject.h> | |
17 | #include <linux/namei.h> | |
869512ab | 18 | #include <linux/mutex.h> |
ddd29ec6 | 19 | #include <linux/security.h> |
1da177e4 LT |
20 | |
21 | #include "sysfs.h" | |
22 | ||
36ce6dad CH |
23 | static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, |
24 | const char *name, int warn) | |
1da177e4 | 25 | { |
2b29ac25 TH |
26 | struct sysfs_dirent *parent_sd = NULL; |
27 | struct sysfs_dirent *target_sd = NULL; | |
3007e997 | 28 | struct sysfs_dirent *sd = NULL; |
fb6896da | 29 | struct sysfs_addrm_cxt acxt; |
3007e997 | 30 | int error; |
1da177e4 | 31 | |
ceeee1fb GKH |
32 | BUG_ON(!name); |
33 | ||
7d0c7d67 EB |
34 | if (!kobj) |
35 | parent_sd = &sysfs_root; | |
36 | else | |
608e266a | 37 | parent_sd = kobj->sd; |
ceeee1fb | 38 | |
3007e997 | 39 | error = -EFAULT; |
608e266a | 40 | if (!parent_sd) |
3007e997 | 41 | goto out_put; |
2b29ac25 | 42 | |
608e266a | 43 | /* target->sd can go away beneath us but is protected with |
5f995323 | 44 | * sysfs_assoc_lock. Fetch target_sd from it. |
2b29ac25 | 45 | */ |
5f995323 | 46 | spin_lock(&sysfs_assoc_lock); |
608e266a TH |
47 | if (target->sd) |
48 | target_sd = sysfs_get(target->sd); | |
5f995323 | 49 | spin_unlock(&sysfs_assoc_lock); |
2b29ac25 | 50 | |
3007e997 | 51 | error = -ENOENT; |
2b29ac25 | 52 | if (!target_sd) |
3007e997 TH |
53 | goto out_put; |
54 | ||
55 | error = -ENOMEM; | |
56 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); | |
57 | if (!sd) | |
58 | goto out_put; | |
a1da4dfe | 59 | |
b1fc3d61 | 60 | sd->s_symlink.target_sd = target_sd; |
a1da4dfe | 61 | target_sd = NULL; /* reference is now owned by the symlink */ |
1da177e4 | 62 | |
fb6896da | 63 | sysfs_addrm_start(&acxt, parent_sd); |
36ce6dad CH |
64 | if (warn) |
65 | error = sysfs_add_one(&acxt, sd); | |
66 | else | |
67 | error = __sysfs_add_one(&acxt, sd); | |
23dc2799 | 68 | sysfs_addrm_finish(&acxt); |
2b29ac25 | 69 | |
23dc2799 | 70 | if (error) |
967e35dc | 71 | goto out_put; |
967e35dc TH |
72 | |
73 | return 0; | |
fb6896da | 74 | |
3007e997 TH |
75 | out_put: |
76 | sysfs_put(target_sd); | |
77 | sysfs_put(sd); | |
1da177e4 LT |
78 | return error; |
79 | } | |
80 | ||
36ce6dad CH |
81 | /** |
82 | * sysfs_create_link - create symlink between two objects. | |
83 | * @kobj: object whose directory we're creating the link in. | |
84 | * @target: object we're pointing to. | |
85 | * @name: name of the symlink. | |
86 | */ | |
87 | int sysfs_create_link(struct kobject *kobj, struct kobject *target, | |
88 | const char *name) | |
89 | { | |
90 | return sysfs_do_create_link(kobj, target, name, 1); | |
91 | } | |
92 | ||
93 | /** | |
94 | * sysfs_create_link_nowarn - create symlink between two objects. | |
95 | * @kobj: object whose directory we're creating the link in. | |
96 | * @target: object we're pointing to. | |
97 | * @name: name of the symlink. | |
98 | * | |
99 | * This function does the same as sysf_create_link(), but it | |
100 | * doesn't warn if the link already exists. | |
101 | */ | |
102 | int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, | |
103 | const char *name) | |
104 | { | |
105 | return sysfs_do_create_link(kobj, target, name, 0); | |
106 | } | |
107 | ||
1da177e4 LT |
108 | /** |
109 | * sysfs_remove_link - remove symlink in object's directory. | |
110 | * @kobj: object we're acting for. | |
111 | * @name: name of the symlink to remove. | |
112 | */ | |
113 | ||
e3a15db2 | 114 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 | 115 | { |
a839c5af MF |
116 | struct sysfs_dirent *parent_sd = NULL; |
117 | ||
118 | if (!kobj) | |
119 | parent_sd = &sysfs_root; | |
120 | else | |
121 | parent_sd = kobj->sd; | |
122 | ||
123 | sysfs_hash_and_remove(parent_sd, name); | |
1da177e4 LT |
124 | } |
125 | ||
2f90a851 KS |
126 | static int sysfs_get_target_path(struct sysfs_dirent *parent_sd, |
127 | struct sysfs_dirent *target_sd, char *path) | |
1da177e4 | 128 | { |
2f90a851 KS |
129 | struct sysfs_dirent *base, *sd; |
130 | char *s = path; | |
131 | int len = 0; | |
132 | ||
133 | /* go up to the root, stop at the base */ | |
134 | base = parent_sd; | |
135 | while (base->s_parent) { | |
136 | sd = target_sd->s_parent; | |
137 | while (sd->s_parent && base != sd) | |
138 | sd = sd->s_parent; | |
139 | ||
140 | if (base == sd) | |
141 | break; | |
142 | ||
143 | strcpy(s, "../"); | |
144 | s += 3; | |
145 | base = base->s_parent; | |
146 | } | |
147 | ||
148 | /* determine end of target string for reverse fillup */ | |
149 | sd = target_sd; | |
150 | while (sd->s_parent && sd != base) { | |
151 | len += strlen(sd->s_name) + 1; | |
152 | sd = sd->s_parent; | |
153 | } | |
1da177e4 | 154 | |
2f90a851 KS |
155 | /* check limits */ |
156 | if (len < 2) | |
157 | return -EINVAL; | |
158 | len--; | |
159 | if ((s - path) + len > PATH_MAX) | |
1da177e4 LT |
160 | return -ENAMETOOLONG; |
161 | ||
2f90a851 KS |
162 | /* reverse fillup of target string from target to base */ |
163 | sd = target_sd; | |
164 | while (sd->s_parent && sd != base) { | |
165 | int slen = strlen(sd->s_name); | |
1da177e4 | 166 | |
2f90a851 KS |
167 | len -= slen; |
168 | strncpy(s + len, sd->s_name, slen); | |
169 | if (len) | |
170 | s[--len] = '/'; | |
1da177e4 | 171 | |
2f90a851 KS |
172 | sd = sd->s_parent; |
173 | } | |
1da177e4 LT |
174 | |
175 | return 0; | |
176 | } | |
177 | ||
178 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
179 | { | |
2b29ac25 TH |
180 | struct sysfs_dirent *sd = dentry->d_fsdata; |
181 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
b1fc3d61 | 182 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; |
2b29ac25 | 183 | int error; |
1da177e4 | 184 | |
3007e997 | 185 | mutex_lock(&sysfs_mutex); |
2b29ac25 | 186 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
3007e997 | 187 | mutex_unlock(&sysfs_mutex); |
1da177e4 | 188 | |
2b29ac25 | 189 | return error; |
1da177e4 LT |
190 | } |
191 | ||
cc314eef | 192 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
193 | { |
194 | int error = -ENOMEM; | |
195 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
557411eb | 196 | if (page) { |
1da177e4 | 197 | error = sysfs_getlink(dentry, (char *) page); |
557411eb AK |
198 | if (error < 0) |
199 | free_page((unsigned long)page); | |
200 | } | |
1da177e4 | 201 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); |
cc314eef | 202 | return NULL; |
1da177e4 LT |
203 | } |
204 | ||
cc314eef | 205 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
206 | { |
207 | char *page = nd_get_link(nd); | |
208 | if (!IS_ERR(page)) | |
209 | free_page((unsigned long)page); | |
210 | } | |
211 | ||
c5ef1c42 | 212 | const struct inode_operations sysfs_symlink_inode_operations = { |
ddd29ec6 | 213 | .setxattr = sysfs_setxattr, |
1da177e4 LT |
214 | .readlink = generic_readlink, |
215 | .follow_link = sysfs_follow_link, | |
216 | .put_link = sysfs_put_link, | |
217 | }; | |
218 | ||
219 | ||
220 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
221 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |