Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * symlink.c - operations for sysfs symlinks. | |
3 | */ | |
4 | ||
5 | #include <linux/fs.h> | |
6 | #include <linux/module.h> | |
7 | #include <linux/kobject.h> | |
8 | #include <linux/namei.h> | |
9 | ||
10 | #include "sysfs.h" | |
11 | ||
12 | static int object_depth(struct kobject * kobj) | |
13 | { | |
14 | struct kobject * p = kobj; | |
15 | int depth = 0; | |
16 | do { depth++; } while ((p = p->parent)); | |
17 | return depth; | |
18 | } | |
19 | ||
20 | static int object_path_length(struct kobject * kobj) | |
21 | { | |
22 | struct kobject * p = kobj; | |
23 | int length = 1; | |
24 | do { | |
25 | length += strlen(kobject_name(p)) + 1; | |
26 | p = p->parent; | |
27 | } while (p); | |
28 | return length; | |
29 | } | |
30 | ||
31 | static void fill_object_path(struct kobject * kobj, char * buffer, int length) | |
32 | { | |
33 | struct kobject * p; | |
34 | ||
35 | --length; | |
36 | for (p = kobj; p; p = p->parent) { | |
37 | int cur = strlen(kobject_name(p)); | |
38 | ||
39 | /* back up enough to print this bus id with '/' */ | |
40 | length -= cur; | |
41 | strncpy(buffer + length,kobject_name(p),cur); | |
42 | *(buffer + --length) = '/'; | |
43 | } | |
44 | } | |
45 | ||
e3a15db2 | 46 | static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target) |
1da177e4 LT |
47 | { |
48 | struct sysfs_dirent * parent_sd = parent->d_fsdata; | |
49 | struct sysfs_symlink * sl; | |
50 | int error = 0; | |
51 | ||
52 | error = -ENOMEM; | |
53 | sl = kmalloc(sizeof(*sl), GFP_KERNEL); | |
54 | if (!sl) | |
55 | goto exit1; | |
56 | ||
57 | sl->link_name = kmalloc(strlen(name) + 1, GFP_KERNEL); | |
58 | if (!sl->link_name) | |
59 | goto exit2; | |
60 | ||
61 | strcpy(sl->link_name, name); | |
62 | sl->target_kobj = kobject_get(target); | |
63 | ||
64 | error = sysfs_make_dirent(parent_sd, NULL, sl, S_IFLNK|S_IRWXUGO, | |
65 | SYSFS_KOBJ_LINK); | |
66 | if (!error) | |
67 | return 0; | |
68 | ||
b3229087 | 69 | kobject_put(target); |
1da177e4 LT |
70 | kfree(sl->link_name); |
71 | exit2: | |
72 | kfree(sl); | |
73 | exit1: | |
74 | return error; | |
75 | } | |
76 | ||
77 | /** | |
78 | * sysfs_create_link - create symlink between two objects. | |
79 | * @kobj: object whose directory we're creating the link in. | |
80 | * @target: object we're pointing to. | |
81 | * @name: name of the symlink. | |
82 | */ | |
e3a15db2 | 83 | int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name) |
1da177e4 LT |
84 | { |
85 | struct dentry * dentry = kobj->dentry; | |
c516865c | 86 | int error = -EEXIST; |
1da177e4 LT |
87 | |
88 | BUG_ON(!kobj || !kobj->dentry || !name); | |
89 | ||
1b1dcc1b | 90 | mutex_lock(&dentry->d_inode->i_mutex); |
c516865c MS |
91 | if (!sysfs_dirent_exist(dentry->d_fsdata, name)) |
92 | error = sysfs_add_link(dentry, name, target); | |
1b1dcc1b | 93 | mutex_unlock(&dentry->d_inode->i_mutex); |
1da177e4 LT |
94 | return error; |
95 | } | |
96 | ||
97 | ||
98 | /** | |
99 | * sysfs_remove_link - remove symlink in object's directory. | |
100 | * @kobj: object we're acting for. | |
101 | * @name: name of the symlink to remove. | |
102 | */ | |
103 | ||
e3a15db2 | 104 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 LT |
105 | { |
106 | sysfs_hash_and_remove(kobj->dentry,name); | |
107 | } | |
108 | ||
109 | static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target, | |
e3a15db2 | 110 | char *path) |
1da177e4 LT |
111 | { |
112 | char * s; | |
113 | int depth, size; | |
114 | ||
115 | depth = object_depth(kobj); | |
116 | size = object_path_length(target) + depth * 3 - 1; | |
117 | if (size > PATH_MAX) | |
118 | return -ENAMETOOLONG; | |
119 | ||
120 | pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); | |
121 | ||
122 | for (s = path; depth--; s += 3) | |
123 | strcpy(s,"../"); | |
124 | ||
125 | fill_object_path(target, path, size); | |
126 | pr_debug("%s: path = '%s'\n", __FUNCTION__, path); | |
127 | ||
128 | return 0; | |
129 | } | |
130 | ||
131 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
132 | { | |
133 | struct kobject *kobj, *target_kobj; | |
134 | int error = 0; | |
135 | ||
136 | kobj = sysfs_get_kobject(dentry->d_parent); | |
137 | if (!kobj) | |
138 | return -EINVAL; | |
139 | ||
140 | target_kobj = sysfs_get_kobject(dentry); | |
141 | if (!target_kobj) { | |
142 | kobject_put(kobj); | |
143 | return -EINVAL; | |
144 | } | |
145 | ||
146 | down_read(&sysfs_rename_sem); | |
147 | error = sysfs_get_target_path(kobj, target_kobj, path); | |
148 | up_read(&sysfs_rename_sem); | |
149 | ||
150 | kobject_put(kobj); | |
151 | kobject_put(target_kobj); | |
152 | return error; | |
153 | ||
154 | } | |
155 | ||
cc314eef | 156 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
157 | { |
158 | int error = -ENOMEM; | |
159 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
160 | if (page) | |
161 | error = sysfs_getlink(dentry, (char *) page); | |
162 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); | |
cc314eef | 163 | return NULL; |
1da177e4 LT |
164 | } |
165 | ||
cc314eef | 166 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
167 | { |
168 | char *page = nd_get_link(nd); | |
169 | if (!IS_ERR(page)) | |
170 | free_page((unsigned long)page); | |
171 | } | |
172 | ||
173 | struct inode_operations sysfs_symlink_inode_operations = { | |
174 | .readlink = generic_readlink, | |
175 | .follow_link = sysfs_follow_link, | |
176 | .put_link = sysfs_put_link, | |
177 | }; | |
178 | ||
179 | ||
180 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
181 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |