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 | ||
69 | kfree(sl->link_name); | |
70 | exit2: | |
71 | kfree(sl); | |
72 | exit1: | |
73 | return error; | |
74 | } | |
75 | ||
76 | /** | |
77 | * sysfs_create_link - create symlink between two objects. | |
78 | * @kobj: object whose directory we're creating the link in. | |
79 | * @target: object we're pointing to. | |
80 | * @name: name of the symlink. | |
81 | */ | |
e3a15db2 | 82 | int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name) |
1da177e4 LT |
83 | { |
84 | struct dentry * dentry = kobj->dentry; | |
85 | int error = 0; | |
86 | ||
87 | BUG_ON(!kobj || !kobj->dentry || !name); | |
88 | ||
89 | down(&dentry->d_inode->i_sem); | |
90 | error = sysfs_add_link(dentry, name, target); | |
91 | up(&dentry->d_inode->i_sem); | |
92 | return error; | |
93 | } | |
94 | ||
95 | ||
96 | /** | |
97 | * sysfs_remove_link - remove symlink in object's directory. | |
98 | * @kobj: object we're acting for. | |
99 | * @name: name of the symlink to remove. | |
100 | */ | |
101 | ||
e3a15db2 | 102 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 LT |
103 | { |
104 | sysfs_hash_and_remove(kobj->dentry,name); | |
105 | } | |
106 | ||
107 | static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target, | |
e3a15db2 | 108 | char *path) |
1da177e4 LT |
109 | { |
110 | char * s; | |
111 | int depth, size; | |
112 | ||
113 | depth = object_depth(kobj); | |
114 | size = object_path_length(target) + depth * 3 - 1; | |
115 | if (size > PATH_MAX) | |
116 | return -ENAMETOOLONG; | |
117 | ||
118 | pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); | |
119 | ||
120 | for (s = path; depth--; s += 3) | |
121 | strcpy(s,"../"); | |
122 | ||
123 | fill_object_path(target, path, size); | |
124 | pr_debug("%s: path = '%s'\n", __FUNCTION__, path); | |
125 | ||
126 | return 0; | |
127 | } | |
128 | ||
129 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
130 | { | |
131 | struct kobject *kobj, *target_kobj; | |
132 | int error = 0; | |
133 | ||
134 | kobj = sysfs_get_kobject(dentry->d_parent); | |
135 | if (!kobj) | |
136 | return -EINVAL; | |
137 | ||
138 | target_kobj = sysfs_get_kobject(dentry); | |
139 | if (!target_kobj) { | |
140 | kobject_put(kobj); | |
141 | return -EINVAL; | |
142 | } | |
143 | ||
144 | down_read(&sysfs_rename_sem); | |
145 | error = sysfs_get_target_path(kobj, target_kobj, path); | |
146 | up_read(&sysfs_rename_sem); | |
147 | ||
148 | kobject_put(kobj); | |
149 | kobject_put(target_kobj); | |
150 | return error; | |
151 | ||
152 | } | |
153 | ||
154 | static int sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) | |
155 | { | |
156 | int error = -ENOMEM; | |
157 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
158 | if (page) | |
159 | error = sysfs_getlink(dentry, (char *) page); | |
160 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); | |
161 | return 0; | |
162 | } | |
163 | ||
164 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd) | |
165 | { | |
166 | char *page = nd_get_link(nd); | |
167 | if (!IS_ERR(page)) | |
168 | free_page((unsigned long)page); | |
169 | } | |
170 | ||
171 | struct inode_operations sysfs_symlink_inode_operations = { | |
172 | .readlink = generic_readlink, | |
173 | .follow_link = sysfs_follow_link, | |
174 | .put_link = sysfs_put_link, | |
175 | }; | |
176 | ||
177 | ||
178 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
179 | EXPORT_SYMBOL_GPL(sysfs_remove_link); | |
180 |