blob: de402fa915f2778e010d20bfeca2c6ebc05f6ddd [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
12static 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
20static 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
31static 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
Dmitry Torokhove3a15db2005-04-26 02:31:08 -050046static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target)
Linus Torvalds1da177e2005-04-16 15:20:36 -070047{
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);
70exit2:
71 kfree(sl);
72exit1:
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 */
Dmitry Torokhove3a15db2005-04-26 02:31:08 -050082int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name)
Linus Torvalds1da177e2005-04-16 15:20:36 -070083{
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
Dmitry Torokhove3a15db2005-04-26 02:31:08 -0500102void sysfs_remove_link(struct kobject * kobj, const char * name)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103{
104 sysfs_hash_and_remove(kobj->dentry,name);
105}
106
107static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
Dmitry Torokhove3a15db2005-04-26 02:31:08 -0500108 char *path)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109{
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
129static 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
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700154static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155{
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);
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700161 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162}
163
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700164static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165{
166 char *page = nd_get_link(nd);
167 if (!IS_ERR(page))
168 free_page((unsigned long)page);
169}
170
171struct 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
178EXPORT_SYMBOL_GPL(sysfs_create_link);
179EXPORT_SYMBOL_GPL(sysfs_remove_link);
180