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
|
/*
* fs/kernfs/symlink.c - kernfs symlink implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
*
* This file is released under the GPLv2.
*/
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/namei.h>
#include "kernfs-internal.h"
/**
* kernfs_create_link - create a symlink
* @parent: directory to create the symlink in
* @name: name of the symlink
* @target: target node for the symlink to point to
*
* Returns the created node on success, ERR_PTR() value on error.
*/
struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
const char *name,
struct sysfs_dirent *target)
{
struct sysfs_dirent *sd;
struct sysfs_addrm_cxt acxt;
int error;
sd = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
SYSFS_KOBJ_LINK);
if (!sd)
return ERR_PTR(-ENOMEM);
if (parent->s_flags & SYSFS_FLAG_NS)
sd->s_ns = target->s_ns;
sd->s_symlink.target_sd = target;
kernfs_get(target); /* ref owned by symlink */
sysfs_addrm_start(&acxt);
error = sysfs_add_one(&acxt, sd, parent);
sysfs_addrm_finish(&acxt);
if (!error)
return sd;
kernfs_put(sd);
return ERR_PTR(error);
}
static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
struct sysfs_dirent *target_sd, char *path)
{
struct sysfs_dirent *base, *sd;
char *s = path;
int len = 0;
/* go up to the root, stop at the base */
base = parent_sd;
while (base->s_parent) {
sd = target_sd->s_parent;
while (sd->s_parent && base != sd)
sd = sd->s_parent;
if (base == sd)
break;
strcpy(s, "../");
s += 3;
base = base->s_parent;
}
/* determine end of target string for reverse fillup */
sd = target_sd;
while (sd->s_parent && sd != base) {
len += strlen(sd->s_name) + 1;
sd = sd->s_parent;
}
/* check limits */
if (len < 2)
return -EINVAL;
len--;
if ((s - path) + len > PATH_MAX)
return -ENAMETOOLONG;
/* reverse fillup of target string from target to base */
sd = target_sd;
while (sd->s_parent && sd != base) {
int slen = strlen(sd->s_name);
len -= slen;
strncpy(s + len, sd->s_name, slen);
if (len)
s[--len] = '/';
sd = sd->s_parent;
}
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_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);
if (error < 0)
free_page((unsigned long)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 = {
.setxattr = sysfs_setxattr,
.readlink = generic_readlink,
.follow_link = sysfs_follow_link,
.put_link = sysfs_put_link,
.setattr = sysfs_setattr,
.getattr = sysfs_getattr,
.permission = sysfs_permission,
};
|
