Commit | Line | Data |
---|---|---|
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> | |
869512ab | 10 | #include <linux/mutex.h> |
1da177e4 LT |
11 | |
12 | #include "sysfs.h" | |
13 | ||
2b29ac25 | 14 | static int object_depth(struct sysfs_dirent *sd) |
1da177e4 | 15 | { |
1da177e4 | 16 | int depth = 0; |
2b29ac25 TH |
17 | |
18 | for (; sd->s_parent; sd = sd->s_parent) | |
19 | depth++; | |
20 | ||
1da177e4 LT |
21 | return depth; |
22 | } | |
23 | ||
2b29ac25 | 24 | static int object_path_length(struct sysfs_dirent * sd) |
1da177e4 | 25 | { |
1da177e4 | 26 | int length = 1; |
2b29ac25 TH |
27 | |
28 | for (; sd->s_parent; sd = sd->s_parent) | |
29 | length += strlen(sd->s_name) + 1; | |
30 | ||
1da177e4 LT |
31 | return length; |
32 | } | |
33 | ||
2b29ac25 | 34 | static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length) |
1da177e4 | 35 | { |
1da177e4 | 36 | --length; |
2b29ac25 TH |
37 | for (; sd->s_parent; sd = sd->s_parent) { |
38 | int cur = strlen(sd->s_name); | |
1da177e4 LT |
39 | |
40 | /* back up enough to print this bus id with '/' */ | |
41 | length -= cur; | |
2b29ac25 | 42 | strncpy(buffer + length, sd->s_name, cur); |
1da177e4 LT |
43 | *(buffer + --length) = '/'; |
44 | } | |
45 | } | |
46 | ||
1da177e4 LT |
47 | /** |
48 | * sysfs_create_link - create symlink between two objects. | |
49 | * @kobj: object whose directory we're creating the link in. | |
50 | * @target: object we're pointing to. | |
51 | * @name: name of the symlink. | |
52 | */ | |
e3a15db2 | 53 | int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name) |
1da177e4 | 54 | { |
2b29ac25 TH |
55 | struct sysfs_dirent *parent_sd = NULL; |
56 | struct sysfs_dirent *target_sd = NULL; | |
3007e997 | 57 | struct sysfs_dirent *sd = NULL; |
fb6896da | 58 | struct sysfs_addrm_cxt acxt; |
3007e997 | 59 | int error; |
1da177e4 | 60 | |
ceeee1fb GKH |
61 | BUG_ON(!name); |
62 | ||
7d0c7d67 EB |
63 | if (!kobj) |
64 | parent_sd = &sysfs_root; | |
65 | else | |
608e266a | 66 | parent_sd = kobj->sd; |
ceeee1fb | 67 | |
3007e997 | 68 | error = -EFAULT; |
608e266a | 69 | if (!parent_sd) |
3007e997 | 70 | goto out_put; |
2b29ac25 | 71 | |
608e266a | 72 | /* target->sd can go away beneath us but is protected with |
5f995323 | 73 | * sysfs_assoc_lock. Fetch target_sd from it. |
2b29ac25 | 74 | */ |
5f995323 | 75 | spin_lock(&sysfs_assoc_lock); |
608e266a TH |
76 | if (target->sd) |
77 | target_sd = sysfs_get(target->sd); | |
5f995323 | 78 | spin_unlock(&sysfs_assoc_lock); |
2b29ac25 | 79 | |
3007e997 | 80 | error = -ENOENT; |
2b29ac25 | 81 | if (!target_sd) |
3007e997 TH |
82 | goto out_put; |
83 | ||
84 | error = -ENOMEM; | |
85 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); | |
86 | if (!sd) | |
87 | goto out_put; | |
a1da4dfe | 88 | |
b1fc3d61 | 89 | sd->s_symlink.target_sd = target_sd; |
a1da4dfe | 90 | target_sd = NULL; /* reference is now owned by the symlink */ |
1da177e4 | 91 | |
fb6896da | 92 | sysfs_addrm_start(&acxt, parent_sd); |
23dc2799 TH |
93 | error = sysfs_add_one(&acxt, sd); |
94 | sysfs_addrm_finish(&acxt); | |
2b29ac25 | 95 | |
23dc2799 | 96 | if (error) |
967e35dc | 97 | goto out_put; |
967e35dc TH |
98 | |
99 | return 0; | |
fb6896da | 100 | |
3007e997 TH |
101 | out_put: |
102 | sysfs_put(target_sd); | |
103 | sysfs_put(sd); | |
1da177e4 LT |
104 | return error; |
105 | } | |
106 | ||
107 | ||
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 | { |
608e266a | 116 | sysfs_hash_and_remove(kobj->sd, name); |
1da177e4 LT |
117 | } |
118 | ||
2b29ac25 TH |
119 | static int sysfs_get_target_path(struct sysfs_dirent * parent_sd, |
120 | struct sysfs_dirent * target_sd, char *path) | |
1da177e4 LT |
121 | { |
122 | char * s; | |
123 | int depth, size; | |
124 | ||
2b29ac25 TH |
125 | depth = object_depth(parent_sd); |
126 | size = object_path_length(target_sd) + depth * 3 - 1; | |
1da177e4 LT |
127 | if (size > PATH_MAX) |
128 | return -ENAMETOOLONG; | |
129 | ||
130 | pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); | |
131 | ||
132 | for (s = path; depth--; s += 3) | |
133 | strcpy(s,"../"); | |
134 | ||
2b29ac25 | 135 | fill_object_path(target_sd, path, size); |
1da177e4 LT |
136 | pr_debug("%s: path = '%s'\n", __FUNCTION__, path); |
137 | ||
138 | return 0; | |
139 | } | |
140 | ||
141 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
142 | { | |
2b29ac25 TH |
143 | struct sysfs_dirent *sd = dentry->d_fsdata; |
144 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
b1fc3d61 | 145 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; |
2b29ac25 | 146 | int error; |
1da177e4 | 147 | |
3007e997 | 148 | mutex_lock(&sysfs_mutex); |
2b29ac25 | 149 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
3007e997 | 150 | mutex_unlock(&sysfs_mutex); |
1da177e4 | 151 | |
2b29ac25 | 152 | return error; |
1da177e4 LT |
153 | } |
154 | ||
cc314eef | 155 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
156 | { |
157 | int error = -ENOMEM; | |
158 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
159 | if (page) | |
160 | error = sysfs_getlink(dentry, (char *) page); | |
161 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); | |
cc314eef | 162 | return NULL; |
1da177e4 LT |
163 | } |
164 | ||
cc314eef | 165 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
166 | { |
167 | char *page = nd_get_link(nd); | |
168 | if (!IS_ERR(page)) | |
169 | free_page((unsigned long)page); | |
170 | } | |
171 | ||
c5ef1c42 | 172 | const struct inode_operations sysfs_symlink_inode_operations = { |
1da177e4 LT |
173 | .readlink = generic_readlink, |
174 | .follow_link = sysfs_follow_link, | |
175 | .put_link = sysfs_put_link, | |
176 | }; | |
177 | ||
178 | ||
179 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
180 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |