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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * symlink.c - operations for sysfs symlinks. | |
3 | */ | |
4 | ||
5 | #include <linux/fs.h> | |
ceeee1fb | 6 | #include <linux/mount.h> |
1da177e4 LT |
7 | #include <linux/module.h> |
8 | #include <linux/kobject.h> | |
9 | #include <linux/namei.h> | |
94bebf4d | 10 | #include <asm/semaphore.h> |
1da177e4 LT |
11 | |
12 | #include "sysfs.h" | |
13 | ||
14 | static int object_depth(struct kobject * kobj) | |
15 | { | |
16 | struct kobject * p = kobj; | |
17 | int depth = 0; | |
18 | do { depth++; } while ((p = p->parent)); | |
19 | return depth; | |
20 | } | |
21 | ||
22 | static int object_path_length(struct kobject * kobj) | |
23 | { | |
24 | struct kobject * p = kobj; | |
25 | int length = 1; | |
26 | do { | |
27 | length += strlen(kobject_name(p)) + 1; | |
28 | p = p->parent; | |
29 | } while (p); | |
30 | return length; | |
31 | } | |
32 | ||
33 | static void fill_object_path(struct kobject * kobj, char * buffer, int length) | |
34 | { | |
35 | struct kobject * p; | |
36 | ||
37 | --length; | |
38 | for (p = kobj; p; p = p->parent) { | |
39 | int cur = strlen(kobject_name(p)); | |
40 | ||
41 | /* back up enough to print this bus id with '/' */ | |
42 | length -= cur; | |
43 | strncpy(buffer + length,kobject_name(p),cur); | |
44 | *(buffer + --length) = '/'; | |
45 | } | |
46 | } | |
47 | ||
e3a15db2 | 48 | static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target) |
1da177e4 LT |
49 | { |
50 | struct sysfs_dirent * parent_sd = parent->d_fsdata; | |
a26cd722 | 51 | struct sysfs_dirent * sd; |
1da177e4 | 52 | |
3e519038 | 53 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); |
a26cd722 | 54 | if (!sd) |
3e519038 | 55 | return -ENOMEM; |
dfeb9fb0 | 56 | |
3e519038 TH |
57 | sd->s_elem.symlink.target_kobj = kobject_get(target); |
58 | sysfs_attach_dirent(sd, parent_sd, NULL); | |
dfeb9fb0 | 59 | return 0; |
1da177e4 LT |
60 | } |
61 | ||
62 | /** | |
63 | * sysfs_create_link - create symlink between two objects. | |
64 | * @kobj: object whose directory we're creating the link in. | |
65 | * @target: object we're pointing to. | |
66 | * @name: name of the symlink. | |
67 | */ | |
e3a15db2 | 68 | int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name) |
1da177e4 | 69 | { |
ceeee1fb | 70 | struct dentry *dentry = NULL; |
c516865c | 71 | int error = -EEXIST; |
1da177e4 | 72 | |
ceeee1fb GKH |
73 | BUG_ON(!name); |
74 | ||
75 | if (!kobj) { | |
76 | if (sysfs_mount && sysfs_mount->mnt_sb) | |
77 | dentry = sysfs_mount->mnt_sb->s_root; | |
78 | } else | |
79 | dentry = kobj->dentry; | |
80 | ||
81 | if (!dentry) | |
82 | return -EFAULT; | |
1da177e4 | 83 | |
1b1dcc1b | 84 | mutex_lock(&dentry->d_inode->i_mutex); |
c516865c MS |
85 | if (!sysfs_dirent_exist(dentry->d_fsdata, name)) |
86 | error = sysfs_add_link(dentry, name, target); | |
1b1dcc1b | 87 | mutex_unlock(&dentry->d_inode->i_mutex); |
1da177e4 LT |
88 | return error; |
89 | } | |
90 | ||
91 | ||
92 | /** | |
93 | * sysfs_remove_link - remove symlink in object's directory. | |
94 | * @kobj: object we're acting for. | |
95 | * @name: name of the symlink to remove. | |
96 | */ | |
97 | ||
e3a15db2 | 98 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 LT |
99 | { |
100 | sysfs_hash_and_remove(kobj->dentry,name); | |
101 | } | |
102 | ||
103 | static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target, | |
e3a15db2 | 104 | char *path) |
1da177e4 LT |
105 | { |
106 | char * s; | |
107 | int depth, size; | |
108 | ||
109 | depth = object_depth(kobj); | |
110 | size = object_path_length(target) + depth * 3 - 1; | |
111 | if (size > PATH_MAX) | |
112 | return -ENAMETOOLONG; | |
113 | ||
114 | pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); | |
115 | ||
116 | for (s = path; depth--; s += 3) | |
117 | strcpy(s,"../"); | |
118 | ||
119 | fill_object_path(target, path, size); | |
120 | pr_debug("%s: path = '%s'\n", __FUNCTION__, path); | |
121 | ||
122 | return 0; | |
123 | } | |
124 | ||
125 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
126 | { | |
127 | struct kobject *kobj, *target_kobj; | |
128 | int error = 0; | |
129 | ||
130 | kobj = sysfs_get_kobject(dentry->d_parent); | |
131 | if (!kobj) | |
132 | return -EINVAL; | |
133 | ||
134 | target_kobj = sysfs_get_kobject(dentry); | |
135 | if (!target_kobj) { | |
136 | kobject_put(kobj); | |
137 | return -EINVAL; | |
138 | } | |
139 | ||
140 | down_read(&sysfs_rename_sem); | |
141 | error = sysfs_get_target_path(kobj, target_kobj, path); | |
142 | up_read(&sysfs_rename_sem); | |
143 | ||
144 | kobject_put(kobj); | |
145 | kobject_put(target_kobj); | |
146 | return error; | |
147 | ||
148 | } | |
149 | ||
cc314eef | 150 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
151 | { |
152 | int error = -ENOMEM; | |
153 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
154 | if (page) | |
155 | error = sysfs_getlink(dentry, (char *) page); | |
156 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); | |
cc314eef | 157 | return NULL; |
1da177e4 LT |
158 | } |
159 | ||
cc314eef | 160 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
161 | { |
162 | char *page = nd_get_link(nd); | |
163 | if (!IS_ERR(page)) | |
164 | free_page((unsigned long)page); | |
165 | } | |
166 | ||
c5ef1c42 | 167 | const struct inode_operations sysfs_symlink_inode_operations = { |
1da177e4 LT |
168 | .readlink = generic_readlink, |
169 | .follow_link = sysfs_follow_link, | |
170 | .put_link = sysfs_put_link, | |
171 | }; | |
172 | ||
173 | ||
174 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
175 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |