diff options
Diffstat (limited to '')
| -rw-r--r-- | fs/sysfs/symlink.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c new file mode 100644 index 000000000..5603530a1 --- /dev/null +++ b/fs/sysfs/symlink.c @@ -0,0 +1,198 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * fs/sysfs/symlink.c - sysfs symlink implementation + * + * Copyright (c) 2001-3 Patrick Mochel + * Copyright (c) 2007 SUSE Linux Products GmbH + * Copyright (c) 2007 Tejun Heo <teheo@suse.de> + * + * Please see Documentation/filesystems/sysfs.rst for more information. + */ + +#include <linux/fs.h> +#include <linux/module.h> +#include <linux/kobject.h> +#include <linux/mutex.h> +#include <linux/security.h> + +#include "sysfs.h" + +static int sysfs_do_create_link_sd(struct kernfs_node *parent, + struct kobject *target_kobj, + const char *name, int warn) +{ + struct kernfs_node *kn, *target = NULL; + + if (WARN_ON(!name || !parent)) + return -EINVAL; + + /* + * We don't own @target_kobj and it may be removed at any time. + * Synchronize using sysfs_symlink_target_lock. See + * sysfs_remove_dir() for details. + */ + spin_lock(&sysfs_symlink_target_lock); + if (target_kobj->sd) { + target = target_kobj->sd; + kernfs_get(target); + } + spin_unlock(&sysfs_symlink_target_lock); + + if (!target) + return -ENOENT; + + kn = kernfs_create_link(parent, name, target); + kernfs_put(target); + + if (!IS_ERR(kn)) + return 0; + + if (warn && PTR_ERR(kn) == -EEXIST) + sysfs_warn_dup(parent, name); + return PTR_ERR(kn); +} + +/** + * sysfs_create_link_sd - create symlink to a given object. + * @kn: directory we're creating the link in. + * @target: object we're pointing to. + * @name: name of the symlink. + */ +int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target, + const char *name) +{ + return sysfs_do_create_link_sd(kn, target, name, 1); +} + +static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, + const char *name, int warn) +{ + struct kernfs_node *parent = NULL; + + if (!kobj) + parent = sysfs_root_kn; + else + parent = kobj->sd; + + if (!parent) + return -EFAULT; + + return sysfs_do_create_link_sd(parent, target, name, warn); +} + +/** + * 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) +{ + return sysfs_do_create_link(kobj, target, name, 1); +} +EXPORT_SYMBOL_GPL(sysfs_create_link); + +/** + * sysfs_create_link_nowarn - 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. + * + * This function does the same as sysfs_create_link(), but it + * doesn't warn if the link already exists. + */ +int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, + const char *name) +{ + return sysfs_do_create_link(kobj, target, name, 0); +} +EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn); + +/** + * sysfs_delete_link - remove symlink in object's directory. + * @kobj: object we're acting for. + * @targ: object we're pointing to. + * @name: name of the symlink to remove. + * + * Unlike sysfs_remove_link sysfs_delete_link has enough information + * to successfully delete symlinks in tagged directories. + */ +void sysfs_delete_link(struct kobject *kobj, struct kobject *targ, + const char *name) +{ + const void *ns = NULL; + + /* + * We don't own @target and it may be removed at any time. + * Synchronize using sysfs_symlink_target_lock. See + * sysfs_remove_dir() for details. + */ + spin_lock(&sysfs_symlink_target_lock); + if (targ->sd && kernfs_ns_enabled(kobj->sd)) + ns = targ->sd->ns; + spin_unlock(&sysfs_symlink_target_lock); + kernfs_remove_by_name_ns(kobj->sd, name, ns); +} + +/** + * 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) +{ + struct kernfs_node *parent = NULL; + + if (!kobj) + parent = sysfs_root_kn; + else + parent = kobj->sd; + + kernfs_remove_by_name(parent, name); +} +EXPORT_SYMBOL_GPL(sysfs_remove_link); + +/** + * sysfs_rename_link_ns - rename symlink in object's directory. + * @kobj: object we're acting for. + * @targ: object we're pointing to. + * @old: previous name of the symlink. + * @new: new name of the symlink. + * @new_ns: new namespace of the symlink. + * + * A helper function for the common rename symlink idiom. + */ +int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ, + const char *old, const char *new, const void *new_ns) +{ + struct kernfs_node *parent, *kn = NULL; + const void *old_ns = NULL; + int result; + + if (!kobj) + parent = sysfs_root_kn; + else + parent = kobj->sd; + + if (targ->sd) + old_ns = targ->sd->ns; + + result = -ENOENT; + kn = kernfs_find_and_get_ns(parent, old, old_ns); + if (!kn) + goto out; + + result = -EINVAL; + if (kernfs_type(kn) != KERNFS_LINK) + goto out; + if (kn->symlink.target_kn->priv != targ) + goto out; + + result = kernfs_rename_ns(kn, parent, new, new_ns); + +out: + kernfs_put(kn); + return result; +} +EXPORT_SYMBOL_GPL(sysfs_rename_link_ns); |