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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> |
1da177e4 LT |
19 | |
20 | #include "sysfs.h" | |
21 | ||
2b29ac25 | 22 | static int object_depth(struct sysfs_dirent *sd) |
1da177e4 | 23 | { |
1da177e4 | 24 | int depth = 0; |
2b29ac25 TH |
25 | |
26 | for (; sd->s_parent; sd = sd->s_parent) | |
27 | depth++; | |
28 | ||
1da177e4 LT |
29 | return depth; |
30 | } | |
31 | ||
2b29ac25 | 32 | static int object_path_length(struct sysfs_dirent * sd) |
1da177e4 | 33 | { |
1da177e4 | 34 | int length = 1; |
2b29ac25 TH |
35 | |
36 | for (; sd->s_parent; sd = sd->s_parent) | |
37 | length += strlen(sd->s_name) + 1; | |
38 | ||
1da177e4 LT |
39 | return length; |
40 | } | |
41 | ||
2b29ac25 | 42 | static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length) |
1da177e4 | 43 | { |
1da177e4 | 44 | --length; |
2b29ac25 TH |
45 | for (; sd->s_parent; sd = sd->s_parent) { |
46 | int cur = strlen(sd->s_name); | |
1da177e4 LT |
47 | |
48 | /* back up enough to print this bus id with '/' */ | |
49 | length -= cur; | |
2b29ac25 | 50 | strncpy(buffer + length, sd->s_name, cur); |
1da177e4 LT |
51 | *(buffer + --length) = '/'; |
52 | } | |
53 | } | |
54 | ||
1da177e4 LT |
55 | /** |
56 | * sysfs_create_link - create symlink between two objects. | |
57 | * @kobj: object whose directory we're creating the link in. | |
58 | * @target: object we're pointing to. | |
59 | * @name: name of the symlink. | |
60 | */ | |
e3a15db2 | 61 | int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name) |
1da177e4 | 62 | { |
2b29ac25 TH |
63 | struct sysfs_dirent *parent_sd = NULL; |
64 | struct sysfs_dirent *target_sd = NULL; | |
3007e997 | 65 | struct sysfs_dirent *sd = NULL; |
fb6896da | 66 | struct sysfs_addrm_cxt acxt; |
3007e997 | 67 | int error; |
1da177e4 | 68 | |
ceeee1fb GKH |
69 | BUG_ON(!name); |
70 | ||
7d0c7d67 EB |
71 | if (!kobj) |
72 | parent_sd = &sysfs_root; | |
73 | else | |
608e266a | 74 | parent_sd = kobj->sd; |
ceeee1fb | 75 | |
3007e997 | 76 | error = -EFAULT; |
608e266a | 77 | if (!parent_sd) |
3007e997 | 78 | goto out_put; |
2b29ac25 | 79 | |
608e266a | 80 | /* target->sd can go away beneath us but is protected with |
5f995323 | 81 | * sysfs_assoc_lock. Fetch target_sd from it. |
2b29ac25 | 82 | */ |
5f995323 | 83 | spin_lock(&sysfs_assoc_lock); |
608e266a TH |
84 | if (target->sd) |
85 | target_sd = sysfs_get(target->sd); | |
5f995323 | 86 | spin_unlock(&sysfs_assoc_lock); |
2b29ac25 | 87 | |
3007e997 | 88 | error = -ENOENT; |
2b29ac25 | 89 | if (!target_sd) |
3007e997 TH |
90 | goto out_put; |
91 | ||
92 | error = -ENOMEM; | |
93 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); | |
94 | if (!sd) | |
95 | goto out_put; | |
a1da4dfe | 96 | |
b1fc3d61 | 97 | sd->s_symlink.target_sd = target_sd; |
a1da4dfe | 98 | target_sd = NULL; /* reference is now owned by the symlink */ |
1da177e4 | 99 | |
fb6896da | 100 | sysfs_addrm_start(&acxt, parent_sd); |
23dc2799 TH |
101 | error = sysfs_add_one(&acxt, sd); |
102 | sysfs_addrm_finish(&acxt); | |
2b29ac25 | 103 | |
23dc2799 | 104 | if (error) |
967e35dc | 105 | goto out_put; |
967e35dc TH |
106 | |
107 | return 0; | |
fb6896da | 108 | |
3007e997 TH |
109 | out_put: |
110 | sysfs_put(target_sd); | |
111 | sysfs_put(sd); | |
1da177e4 LT |
112 | return error; |
113 | } | |
114 | ||
115 | ||
116 | /** | |
117 | * sysfs_remove_link - remove symlink in object's directory. | |
118 | * @kobj: object we're acting for. | |
119 | * @name: name of the symlink to remove. | |
120 | */ | |
121 | ||
e3a15db2 | 122 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 | 123 | { |
608e266a | 124 | sysfs_hash_and_remove(kobj->sd, name); |
1da177e4 LT |
125 | } |
126 | ||
2b29ac25 TH |
127 | static int sysfs_get_target_path(struct sysfs_dirent * parent_sd, |
128 | struct sysfs_dirent * target_sd, char *path) | |
1da177e4 LT |
129 | { |
130 | char * s; | |
131 | int depth, size; | |
132 | ||
2b29ac25 TH |
133 | depth = object_depth(parent_sd); |
134 | size = object_path_length(target_sd) + depth * 3 - 1; | |
1da177e4 LT |
135 | if (size > PATH_MAX) |
136 | return -ENAMETOOLONG; | |
137 | ||
138 | pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); | |
139 | ||
140 | for (s = path; depth--; s += 3) | |
141 | strcpy(s,"../"); | |
142 | ||
2b29ac25 | 143 | fill_object_path(target_sd, path, size); |
1da177e4 LT |
144 | pr_debug("%s: path = '%s'\n", __FUNCTION__, path); |
145 | ||
146 | return 0; | |
147 | } | |
148 | ||
149 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
150 | { | |
2b29ac25 TH |
151 | struct sysfs_dirent *sd = dentry->d_fsdata; |
152 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
b1fc3d61 | 153 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; |
2b29ac25 | 154 | int error; |
1da177e4 | 155 | |
3007e997 | 156 | mutex_lock(&sysfs_mutex); |
2b29ac25 | 157 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
3007e997 | 158 | mutex_unlock(&sysfs_mutex); |
1da177e4 | 159 | |
2b29ac25 | 160 | return error; |
1da177e4 LT |
161 | } |
162 | ||
cc314eef | 163 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
164 | { |
165 | int error = -ENOMEM; | |
166 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
167 | if (page) | |
168 | error = sysfs_getlink(dentry, (char *) page); | |
169 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); | |
cc314eef | 170 | return NULL; |
1da177e4 LT |
171 | } |
172 | ||
cc314eef | 173 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
174 | { |
175 | char *page = nd_get_link(nd); | |
176 | if (!IS_ERR(page)) | |
177 | free_page((unsigned long)page); | |
178 | } | |
179 | ||
c5ef1c42 | 180 | const struct inode_operations sysfs_symlink_inode_operations = { |
1da177e4 LT |
181 | .readlink = generic_readlink, |
182 | .follow_link = sysfs_follow_link, | |
183 | .put_link = sysfs_put_link, | |
184 | }; | |
185 | ||
186 | ||
187 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
188 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |