| 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/module.h> |
| 15 | #include <linux/kobject.h> |
| 16 | #include <linux/mutex.h> |
| 17 | #include <linux/security.h> |
| 18 | |
| 19 | #include "sysfs.h" |
| 20 | |
| 21 | static int sysfs_do_create_link_sd(struct kernfs_node *parent, |
| 22 | struct kobject *target_kobj, |
| 23 | const char *name, int warn) |
| 24 | { |
| 25 | struct kernfs_node *kn, *target = NULL; |
| 26 | |
| 27 | BUG_ON(!name || !parent); |
| 28 | |
| 29 | /* |
| 30 | * We don't own @target_kobj and it may be removed at any time. |
| 31 | * Synchronize using sysfs_symlink_target_lock. See |
| 32 | * sysfs_remove_dir() for details. |
| 33 | */ |
| 34 | spin_lock(&sysfs_symlink_target_lock); |
| 35 | if (target_kobj->sd) { |
| 36 | target = target_kobj->sd; |
| 37 | kernfs_get(target); |
| 38 | } |
| 39 | spin_unlock(&sysfs_symlink_target_lock); |
| 40 | |
| 41 | if (!target) |
| 42 | return -ENOENT; |
| 43 | |
| 44 | kn = kernfs_create_link(parent, name, target); |
| 45 | kernfs_put(target); |
| 46 | |
| 47 | if (!IS_ERR(kn)) |
| 48 | return 0; |
| 49 | |
| 50 | if (warn && PTR_ERR(kn) == -EEXIST) |
| 51 | sysfs_warn_dup(parent, name); |
| 52 | return PTR_ERR(kn); |
| 53 | } |
| 54 | |
| 55 | /** |
| 56 | * sysfs_create_link_sd - create symlink to a given object. |
| 57 | * @kn: directory we're creating the link in. |
| 58 | * @target: object we're pointing to. |
| 59 | * @name: name of the symlink. |
| 60 | */ |
| 61 | int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target, |
| 62 | const char *name) |
| 63 | { |
| 64 | return sysfs_do_create_link_sd(kn, target, name, 1); |
| 65 | } |
| 66 | |
| 67 | static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, |
| 68 | const char *name, int warn) |
| 69 | { |
| 70 | struct kernfs_node *parent = NULL; |
| 71 | |
| 72 | if (!kobj) |
| 73 | parent = sysfs_root_kn; |
| 74 | else |
| 75 | parent = kobj->sd; |
| 76 | |
| 77 | if (!parent) |
| 78 | return -EFAULT; |
| 79 | |
| 80 | return sysfs_do_create_link_sd(parent, target, name, warn); |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * sysfs_create_link - create symlink between two objects. |
| 85 | * @kobj: object whose directory we're creating the link in. |
| 86 | * @target: object we're pointing to. |
| 87 | * @name: name of the symlink. |
| 88 | */ |
| 89 | int sysfs_create_link(struct kobject *kobj, struct kobject *target, |
| 90 | const char *name) |
| 91 | { |
| 92 | return sysfs_do_create_link(kobj, target, name, 1); |
| 93 | } |
| 94 | EXPORT_SYMBOL_GPL(sysfs_create_link); |
| 95 | |
| 96 | /** |
| 97 | * sysfs_create_link_nowarn - create symlink between two objects. |
| 98 | * @kobj: object whose directory we're creating the link in. |
| 99 | * @target: object we're pointing to. |
| 100 | * @name: name of the symlink. |
| 101 | * |
| 102 | * This function does the same as sysfs_create_link(), but it |
| 103 | * doesn't warn if the link already exists. |
| 104 | */ |
| 105 | int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, |
| 106 | const char *name) |
| 107 | { |
| 108 | return sysfs_do_create_link(kobj, target, name, 0); |
| 109 | } |
| 110 | |
| 111 | /** |
| 112 | * sysfs_delete_link - remove symlink in object's directory. |
| 113 | * @kobj: object we're acting for. |
| 114 | * @targ: object we're pointing to. |
| 115 | * @name: name of the symlink to remove. |
| 116 | * |
| 117 | * Unlike sysfs_remove_link sysfs_delete_link has enough information |
| 118 | * to successfully delete symlinks in tagged directories. |
| 119 | */ |
| 120 | void sysfs_delete_link(struct kobject *kobj, struct kobject *targ, |
| 121 | const char *name) |
| 122 | { |
| 123 | const void *ns = NULL; |
| 124 | |
| 125 | /* |
| 126 | * We don't own @target and it may be removed at any time. |
| 127 | * Synchronize using sysfs_symlink_target_lock. See |
| 128 | * sysfs_remove_dir() for details. |
| 129 | */ |
| 130 | spin_lock(&sysfs_symlink_target_lock); |
| 131 | if (targ->sd && kernfs_ns_enabled(kobj->sd)) |
| 132 | ns = targ->sd->ns; |
| 133 | spin_unlock(&sysfs_symlink_target_lock); |
| 134 | kernfs_remove_by_name_ns(kobj->sd, name, ns); |
| 135 | } |
| 136 | |
| 137 | /** |
| 138 | * sysfs_remove_link - remove symlink in object's directory. |
| 139 | * @kobj: object we're acting for. |
| 140 | * @name: name of the symlink to remove. |
| 141 | */ |
| 142 | void sysfs_remove_link(struct kobject *kobj, const char *name) |
| 143 | { |
| 144 | struct kernfs_node *parent = NULL; |
| 145 | |
| 146 | if (!kobj) |
| 147 | parent = sysfs_root_kn; |
| 148 | else |
| 149 | parent = kobj->sd; |
| 150 | |
| 151 | kernfs_remove_by_name(parent, name); |
| 152 | } |
| 153 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |
| 154 | |
| 155 | /** |
| 156 | * sysfs_rename_link_ns - rename symlink in object's directory. |
| 157 | * @kobj: object we're acting for. |
| 158 | * @targ: object we're pointing to. |
| 159 | * @old: previous name of the symlink. |
| 160 | * @new: new name of the symlink. |
| 161 | * @new_ns: new namespace of the symlink. |
| 162 | * |
| 163 | * A helper function for the common rename symlink idiom. |
| 164 | */ |
| 165 | int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ, |
| 166 | const char *old, const char *new, const void *new_ns) |
| 167 | { |
| 168 | struct kernfs_node *parent, *kn = NULL; |
| 169 | const void *old_ns = NULL; |
| 170 | int result; |
| 171 | |
| 172 | if (!kobj) |
| 173 | parent = sysfs_root_kn; |
| 174 | else |
| 175 | parent = kobj->sd; |
| 176 | |
| 177 | if (targ->sd) |
| 178 | old_ns = targ->sd->ns; |
| 179 | |
| 180 | result = -ENOENT; |
| 181 | kn = kernfs_find_and_get_ns(parent, old, old_ns); |
| 182 | if (!kn) |
| 183 | goto out; |
| 184 | |
| 185 | result = -EINVAL; |
| 186 | if (kernfs_type(kn) != KERNFS_LINK) |
| 187 | goto out; |
| 188 | if (kn->symlink.target_kn->priv != targ) |
| 189 | goto out; |
| 190 | |
| 191 | result = kernfs_rename_ns(kn, parent, new, new_ns); |
| 192 | |
| 193 | out: |
| 194 | kernfs_put(kn); |
| 195 | return result; |
| 196 | } |
| 197 | EXPORT_SYMBOL_GPL(sysfs_rename_link_ns); |