Commit | Line | Data |
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b8441ed2 TH |
1 | /* |
2 | * fs/kernfs/symlink.c - kernfs symlink implementation | |
3 | * | |
4 | * Copyright (c) 2001-3 Patrick Mochel | |
5 | * Copyright (c) 2007 SUSE Linux Products GmbH | |
6 | * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> | |
7 | * | |
8 | * This file is released under the GPLv2. | |
9 | */ | |
2072f1af TH |
10 | |
11 | #include <linux/fs.h> | |
12 | #include <linux/gfp.h> | |
13 | #include <linux/namei.h> | |
14 | ||
15 | #include "kernfs-internal.h" | |
16 | ||
17 | /** | |
18 | * kernfs_create_link - create a symlink | |
19 | * @parent: directory to create the symlink in | |
20 | * @name: name of the symlink | |
21 | * @target: target node for the symlink to point to | |
22 | * | |
23 | * Returns the created node on success, ERR_PTR() value on error. | |
24 | */ | |
25 | struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent, | |
26 | const char *name, | |
27 | struct sysfs_dirent *target) | |
28 | { | |
29 | struct sysfs_dirent *sd; | |
30 | struct sysfs_addrm_cxt acxt; | |
31 | int error; | |
32 | ||
bc755553 TH |
33 | sd = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO, |
34 | SYSFS_KOBJ_LINK); | |
2072f1af TH |
35 | if (!sd) |
36 | return ERR_PTR(-ENOMEM); | |
37 | ||
ac9bba03 | 38 | if (kernfs_ns_enabled(parent)) |
2072f1af TH |
39 | sd->s_ns = target->s_ns; |
40 | sd->s_symlink.target_sd = target; | |
41 | kernfs_get(target); /* ref owned by symlink */ | |
42 | ||
43 | sysfs_addrm_start(&acxt); | |
44 | error = sysfs_add_one(&acxt, sd, parent); | |
45 | sysfs_addrm_finish(&acxt); | |
46 | ||
47 | if (!error) | |
48 | return sd; | |
49 | ||
50 | kernfs_put(sd); | |
51 | return ERR_PTR(error); | |
52 | } | |
53 | ||
54 | static int sysfs_get_target_path(struct sysfs_dirent *parent_sd, | |
55 | struct sysfs_dirent *target_sd, char *path) | |
56 | { | |
57 | struct sysfs_dirent *base, *sd; | |
58 | char *s = path; | |
59 | int len = 0; | |
60 | ||
61 | /* go up to the root, stop at the base */ | |
62 | base = parent_sd; | |
63 | while (base->s_parent) { | |
64 | sd = target_sd->s_parent; | |
65 | while (sd->s_parent && base != sd) | |
66 | sd = sd->s_parent; | |
67 | ||
68 | if (base == sd) | |
69 | break; | |
70 | ||
71 | strcpy(s, "../"); | |
72 | s += 3; | |
73 | base = base->s_parent; | |
74 | } | |
75 | ||
76 | /* determine end of target string for reverse fillup */ | |
77 | sd = target_sd; | |
78 | while (sd->s_parent && sd != base) { | |
79 | len += strlen(sd->s_name) + 1; | |
80 | sd = sd->s_parent; | |
81 | } | |
82 | ||
83 | /* check limits */ | |
84 | if (len < 2) | |
85 | return -EINVAL; | |
86 | len--; | |
87 | if ((s - path) + len > PATH_MAX) | |
88 | return -ENAMETOOLONG; | |
89 | ||
90 | /* reverse fillup of target string from target to base */ | |
91 | sd = target_sd; | |
92 | while (sd->s_parent && sd != base) { | |
93 | int slen = strlen(sd->s_name); | |
94 | ||
95 | len -= slen; | |
96 | strncpy(s + len, sd->s_name, slen); | |
97 | if (len) | |
98 | s[--len] = '/'; | |
99 | ||
100 | sd = sd->s_parent; | |
101 | } | |
102 | ||
103 | return 0; | |
104 | } | |
105 | ||
106 | static int sysfs_getlink(struct dentry *dentry, char *path) | |
107 | { | |
108 | struct sysfs_dirent *sd = dentry->d_fsdata; | |
109 | struct sysfs_dirent *parent_sd = sd->s_parent; | |
110 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; | |
111 | int error; | |
112 | ||
113 | mutex_lock(&sysfs_mutex); | |
114 | error = sysfs_get_target_path(parent_sd, target_sd, path); | |
115 | mutex_unlock(&sysfs_mutex); | |
116 | ||
117 | return error; | |
118 | } | |
119 | ||
120 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) | |
121 | { | |
122 | int error = -ENOMEM; | |
123 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
124 | if (page) { | |
125 | error = sysfs_getlink(dentry, (char *) page); | |
126 | if (error < 0) | |
127 | free_page((unsigned long)page); | |
128 | } | |
129 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); | |
130 | return NULL; | |
131 | } | |
132 | ||
133 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, | |
134 | void *cookie) | |
135 | { | |
136 | char *page = nd_get_link(nd); | |
137 | if (!IS_ERR(page)) | |
138 | free_page((unsigned long)page); | |
139 | } | |
140 | ||
141 | const struct inode_operations sysfs_symlink_inode_operations = { | |
142 | .setxattr = sysfs_setxattr, | |
2322392b TH |
143 | .removexattr = sysfs_removexattr, |
144 | .getxattr = sysfs_getxattr, | |
145 | .listxattr = sysfs_listxattr, | |
2072f1af TH |
146 | .readlink = generic_readlink, |
147 | .follow_link = sysfs_follow_link, | |
148 | .put_link = sysfs_put_link, | |
149 | .setattr = sysfs_setattr, | |
150 | .getattr = sysfs_getattr, | |
151 | .permission = sysfs_permission, | |
152 | }; |