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1// SPDX-License-Identifier: GPL-2.02/*3 * fs/sysfs/symlink.c - sysfs symlink implementation4 *5 * Copyright (c) 2001-3 Patrick Mochel6 * Copyright (c) 2007 SUSE Linux Products GmbH7 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>8 *9 * Please see Documentation/filesystems/sysfs.rst for more information.10 */11 12#include <linux/fs.h>13#include <linux/module.h>14#include <linux/kobject.h>15#include <linux/mutex.h>16#include <linux/security.h>17 18#include "sysfs.h"19 20static int sysfs_do_create_link_sd(struct kernfs_node *parent,21 struct kobject *target_kobj,22 const char *name, int warn)23{24 struct kernfs_node *kn, *target = NULL;25 26 if (WARN_ON(!name || !parent))27 return -EINVAL;28 29 /*30 * We don't own @target_kobj and it may be removed at any time.31 * Synchronize using sysfs_symlink_target_lock. See32 * 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 */61int 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 67static 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 else75 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 */89int 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}94EXPORT_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 it103 * doesn't warn if the link already exists.104 */105int 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}110EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn);111 112/**113 * sysfs_delete_link - remove symlink in object's directory.114 * @kobj: object we're acting for.115 * @targ: object we're pointing to.116 * @name: name of the symlink to remove.117 *118 * Unlike sysfs_remove_link sysfs_delete_link has enough information119 * to successfully delete symlinks in tagged directories.120 */121void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,122 const char *name)123{124 const void *ns = NULL;125 126 /*127 * We don't own @target and it may be removed at any time.128 * Synchronize using sysfs_symlink_target_lock. See129 * sysfs_remove_dir() for details.130 */131 spin_lock(&sysfs_symlink_target_lock);132 if (targ->sd && kernfs_ns_enabled(kobj->sd))133 ns = targ->sd->ns;134 spin_unlock(&sysfs_symlink_target_lock);135 kernfs_remove_by_name_ns(kobj->sd, name, ns);136}137 138/**139 * sysfs_remove_link - remove symlink in object's directory.140 * @kobj: object we're acting for.141 * @name: name of the symlink to remove.142 */143void sysfs_remove_link(struct kobject *kobj, const char *name)144{145 struct kernfs_node *parent = NULL;146 147 if (!kobj)148 parent = sysfs_root_kn;149 else150 parent = kobj->sd;151 152 kernfs_remove_by_name(parent, name);153}154EXPORT_SYMBOL_GPL(sysfs_remove_link);155 156/**157 * sysfs_rename_link_ns - rename symlink in object's directory.158 * @kobj: object we're acting for.159 * @targ: object we're pointing to.160 * @old: previous name of the symlink.161 * @new: new name of the symlink.162 * @new_ns: new namespace of the symlink.163 *164 * A helper function for the common rename symlink idiom.165 */166int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,167 const char *old, const char *new, const void *new_ns)168{169 struct kernfs_node *parent, *kn = NULL;170 const void *old_ns = NULL;171 int result;172 173 if (!kobj)174 parent = sysfs_root_kn;175 else176 parent = kobj->sd;177 178 if (targ->sd)179 old_ns = targ->sd->ns;180 181 result = -ENOENT;182 kn = kernfs_find_and_get_ns(parent, old, old_ns);183 if (!kn)184 goto out;185 186 result = -EINVAL;187 if (kernfs_type(kn) != KERNFS_LINK)188 goto out;189 if (kn->symlink.target_kn->priv != targ)190 goto out;191 192 result = kernfs_rename_ns(kn, parent, new, new_ns);193 194out:195 kernfs_put(kn);196 return result;197}198EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);199