1 /*
2 * fs/sysfs/symlink.c - sysfs symlink implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
7 *
8 * This file is released under the GPLv2.
9 *
10 * Please see Documentation/filesystems/sysfs.txt for more information.
11 */
12
13 #include <linux/fs.h>
14 #include <linux/mount.h>
15 #include <linux/module.h>
16 #include <linux/kobject.h>
17 #include <linux/namei.h>
18 #include <linux/mutex.h>
19
20 #include "sysfs.h"
21
22 static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
23 const char *name, int warn)
24 {
25 struct sysfs_dirent *parent_sd = NULL;
26 struct sysfs_dirent *target_sd = NULL;
27 struct sysfs_dirent *sd = NULL;
28 struct sysfs_addrm_cxt acxt;
29 int error;
30
31 BUG_ON(!name);
32
33 if (!kobj)
34 parent_sd = &sysfs_root;
35 else
36 parent_sd = kobj->sd;
37
38 error = -EFAULT;
39 if (!parent_sd)
40 goto out_put;
41
42 /* target->sd can go away beneath us but is protected with
43 * sysfs_assoc_lock. Fetch target_sd from it.
44 */
45 spin_lock(&sysfs_assoc_lock);
46 if (target->sd)
47 target_sd = sysfs_get(target->sd);
48 spin_unlock(&sysfs_assoc_lock);
49
50 error = -ENOENT;
51 if (!target_sd)
52 goto out_put;
53
54 error = -ENOMEM;
55 sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
56 if (!sd)
57 goto out_put;
58
59 sd->s_symlink.target_sd = target_sd;
60 target_sd = NULL; /* reference is now owned by the symlink */
61
62 sysfs_addrm_start(&acxt, parent_sd);
63 if (warn)
64 error = sysfs_add_one(&acxt, sd);
65 else
66 error = __sysfs_add_one(&acxt, sd);
67 sysfs_addrm_finish(&acxt);
68
69 if (error)
70 goto out_put;
71
72 return 0;
73
74 out_put:
75 sysfs_put(target_sd);
76 sysfs_put(sd);
77 return error;
78 }
79
80 /**
81 * sysfs_create_link - create symlink between two objects.
82 * @kobj: object whose directory we're creating the link in.
83 * @target: object we're pointing to.
84 * @name: name of the symlink.
85 */
86 int sysfs_create_link(struct kobject *kobj, struct kobject *target,
87 const char *name)
88 {
89 return sysfs_do_create_link(kobj, target, name, 1);
90 }
91
92 /**
93 * sysfs_create_link_nowarn - create symlink between two objects.
94 * @kobj: object whose directory we're creating the link in.
95 * @target: object we're pointing to.
96 * @name: name of the symlink.
97 *
98 * This function does the same as sysf_create_link(), but it
99 * doesn't warn if the link already exists.
100 */
101 int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
102 const char *name)
103 {
104 return sysfs_do_create_link(kobj, target, name, 0);
105 }
106
107 /**
108 * sysfs_remove_link - remove symlink in object's directory.
109 * @kobj: object we're acting for.
110 * @name: name of the symlink to remove.
111 */
112
113 void sysfs_remove_link(struct kobject * kobj, const char * name)
114 {
115 struct sysfs_dirent *parent_sd = NULL;
116
117 if (!kobj)
118 parent_sd = &sysfs_root;
119 else
120 parent_sd = kobj->sd;
121
122 sysfs_hash_and_remove(parent_sd, name);
123 }
124
125 static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
126 struct sysfs_dirent *target_sd, char *path)
127 {
128 struct sysfs_dirent *base, *sd;
129 char *s = path;
130 int len = 0;
131
132 /* go up to the root, stop at the base */
133 base = parent_sd;
134 while (base->s_parent) {
135 sd = target_sd->s_parent;
136 while (sd->s_parent && base != sd)
137 sd = sd->s_parent;
138
139 if (base == sd)
140 break;
141
142 strcpy(s, "../");
143 s += 3;
144 base = base->s_parent;
145 }
146
147 /* determine end of target string for reverse fillup */
148 sd = target_sd;
149 while (sd->s_parent && sd != base) {
150 len += strlen(sd->s_name) + 1;
151 sd = sd->s_parent;
152 }
153
154 /* check limits */
155 if (len < 2)
156 return -EINVAL;
157 len--;
158 if ((s - path) + len > PATH_MAX)
159 return -ENAMETOOLONG;
160
161 /* reverse fillup of target string from target to base */
162 sd = target_sd;
163 while (sd->s_parent && sd != base) {
164 int slen = strlen(sd->s_name);
165
166 len -= slen;
167 strncpy(s + len, sd->s_name, slen);
168 if (len)
169 s[--len] = '/';
170
171 sd = sd->s_parent;
172 }
173
174 return 0;
175 }
176
177 static int sysfs_getlink(struct dentry *dentry, char * path)
178 {
179 struct sysfs_dirent *sd = dentry->d_fsdata;
180 struct sysfs_dirent *parent_sd = sd->s_parent;
181 struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
182 int error;
183
184 mutex_lock(&sysfs_mutex);
185 error = sysfs_get_target_path(parent_sd, target_sd, path);
186 mutex_unlock(&sysfs_mutex);
187
188 return error;
189 }
190
191 static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
192 {
193 int error = -ENOMEM;
194 unsigned long page = get_zeroed_page(GFP_KERNEL);
195 if (page) {
196 error = sysfs_getlink(dentry, (char *) page);
197 if (error < 0)
198 free_page((unsigned long)page);
199 }
200 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
201 return NULL;
202 }
203
204 static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
205 {
206 char *page = nd_get_link(nd);
207 if (!IS_ERR(page))
208 free_page((unsigned long)page);
209 }
210
211 const struct inode_operations sysfs_symlink_inode_operations = {
212 .readlink = generic_readlink,
213 .follow_link = sysfs_follow_link,
214 .put_link = sysfs_put_link,
215 };
216
217
218 EXPORT_SYMBOL_GPL(sysfs_create_link);
219 EXPORT_SYMBOL_GPL(sysfs_remove_link);
220
|
This page was automatically generated by the
LXR engine.
|