1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
/*
* symlink.c - operations for sysfs symlinks.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/mutex.h>
#include "sysfs.h"
static int object_depth(struct sysfs_dirent *sd)
{
int depth = 0;
for (; sd->s_parent; sd = sd->s_parent)
depth++;
return depth;
}
static int object_path_length(struct sysfs_dirent * sd)
{
int length = 1;
for (; sd->s_parent; sd = sd->s_parent)
length += strlen(sd->s_name) + 1;
return length;
}
static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length)
{
--length;
for (; sd->s_parent; sd = sd->s_parent) {
int cur = strlen(sd->s_name);
/* back up enough to print this bus id with '/' */
length -= cur;
strncpy(buffer + length, sd->s_name, cur);
*(buffer + --length) = '/';
}
}
/**
* sysfs_create_link - create symlink between two objects.
* @kobj: object whose directory we're creating the link in.
* @target: object we're pointing to.
* @name: name of the symlink.
*/
int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name)
{
struct sysfs_dirent *parent_sd = NULL;
struct sysfs_dirent *target_sd = NULL;
struct sysfs_dirent *sd = NULL;
struct sysfs_addrm_cxt acxt;
int error;
BUG_ON(!name);
if (!kobj) {
if (sysfs_mount && sysfs_mount->mnt_sb)
parent_sd = sysfs_mount->mnt_sb->s_root->d_fsdata;
} else
parent_sd = kobj->sd;
error = -EFAULT;
if (!parent_sd)
goto out_put;
/* target->sd can go away beneath us but is protected with
* sysfs_assoc_lock. Fetch target_sd from it.
*/
spin_lock(&sysfs_assoc_lock);
if (target->sd)
target_sd = sysfs_get(target->sd);
spin_unlock(&sysfs_assoc_lock);
error = -ENOENT;
if (!target_sd)
goto out_put;
error = -ENOMEM;
sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
if (!sd)
goto out_put;
sd->s_elem.symlink.target_sd = target_sd;
target_sd = NULL; /* reference is now owned by the symlink */
sysfs_addrm_start(&acxt, parent_sd);
error = sysfs_add_one(&acxt, sd);
sysfs_addrm_finish(&acxt);
if (error)
goto out_put;
return 0;
out_put:
sysfs_put(target_sd);
sysfs_put(sd);
return error;
}
/**
* sysfs_remove_link - remove symlink in object's directory.
* @kobj: object we're acting for.
* @name: name of the symlink to remove.
*/
void sysfs_remove_link(struct kobject * kobj, const char * name)
{
sysfs_hash_and_remove(kobj->sd, name);
}
static int sysfs_get_target_path(struct sysfs_dirent * parent_sd,
struct sysfs_dirent * target_sd, char *path)
{
char * s;
int depth, size;
depth = object_depth(parent_sd);
size = object_path_length(target_sd) + depth * 3 - 1;
if (size > PATH_MAX)
return -ENAMETOOLONG;
pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
for (s = path; depth--; s += 3)
strcpy(s,"../");
fill_object_path(target_sd, path, size);
pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
return 0;
}
static int sysfs_getlink(struct dentry *dentry, char * path)
{
struct sysfs_dirent *sd = dentry->d_fsdata;
struct sysfs_dirent *parent_sd = sd->s_parent;
struct sysfs_dirent *target_sd = sd->s_elem.symlink.target_sd;
int error;
mutex_lock(&sysfs_mutex);
error = sysfs_get_target_path(parent_sd, target_sd, path);
mutex_unlock(&sysfs_mutex);
return error;
}
static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
int error = -ENOMEM;
unsigned long page = get_zeroed_page(GFP_KERNEL);
if (page)
error = sysfs_getlink(dentry, (char *) page);
nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
return NULL;
}
static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
char *page = nd_get_link(nd);
if (!IS_ERR(page))
free_page((unsigned long)page);
}
const struct inode_operations sysfs_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = sysfs_follow_link,
.put_link = sysfs_put_link,
};
EXPORT_SYMBOL_GPL(sysfs_create_link);
EXPORT_SYMBOL_GPL(sysfs_remove_link);
|
