path: root/lib/kobject.c

// SPDX-License-Identifier: GPL-2.0
/*
 * kobject.c - library routines for handling generic kernel objects
 *
 * Copyright (c) 2002-2003 Patrick Mochel <mochel@osdl.org>
 * Copyright (c) 2006-2007 Greg Kroah-Hartman <greg@kroah.com>
 * Copyright (c) 2006-2007 Novell Inc.
 *
 * Please see the file Documentation/core-api/kobject.rst for critical information
 * about using the kobject interface.
 */

#include <linux/kobject.h>
#include <linux/string.h>
#include <linux/export.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/random.h>

/**
 * kobject_namespace() - Return @kobj's namespace tag.
 * @kobj: kobject in question
 *
 * Returns namespace tag of @kobj if its parent has namespace ops enabled
 * and thus @kobj should have a namespace tag associated with it.  Returns
 * %NULL otherwise.
 */
const void *kobject_namespace(struct kobject *kobj)
{
	const struct kobj_ns_type_operations *ns_ops = kobj_ns_ops(kobj);

	if (!ns_ops || ns_ops->type == KOBJ_NS_TYPE_NONE)
		return NULL;

	return kobj->ktype->namespace(kobj);
}

/**
 * kobject_get_ownership() - Get sysfs ownership data for @kobj.
 * @kobj: kobject in question
 * @uid: kernel user ID for sysfs objects
 * @gid: kernel group ID for sysfs objects
 *
 * Returns initial uid/gid pair that should be used when creating sysfs
 * representation of given kobject. Normally used to adjust ownership of
 * objects in a container.
 */
void kobject_get_ownership(struct kobject *kobj, kuid_t *uid, kgid_t *gid)
{
	*uid = GLOBAL_ROOT_UID;
	*gid = GLOBAL_ROOT_GID;

	if (kobj->ktype->get_ownership)
		kobj->ktype->get_ownership(kobj, uid, gid);
}

static int create_dir(struct kobject *kobj)
{
	const struct kobj_type *ktype = get_ktype(kobj);
	const struct kobj_ns_type_operations *ops;
	int error;

	error = sysfs_create_dir_ns(kobj, kobject_namespace(kobj));
	if (error)
		return error;

	if (ktype) {
		error = sysfs_create_groups(kobj, ktype->default_groups);
		if (error) {
			sysfs_remove_dir(kobj);
			return error;
		}
	}

	/*
	 * @kobj->sd may be deleted by an ancestor going away.  Hold an
	 * extra reference so that it stays until @kobj is gone.
	 */
	sysfs_get(kobj->sd);

	/*
	 * If @kobj has ns_ops, its children need to be filtered based on
	 * their namespace tags.  Enable namespace support on @kobj->sd.
	 */
	ops = kobj_child_ns_ops(kobj);
	if (ops) {
		BUG_ON(ops->type <= KOBJ_NS_TYPE_NONE);
		BUG_ON(ops->type >= KOBJ_NS_TYPES);
		BUG_ON(!kobj_ns_type_registered(ops->type));

		sysfs_enable_ns(kobj->sd);
	}

	return 0;
}

static int get_kobj_path_length(struct kobject *kobj)
{
	int length = 1;
	struct kobject *parent = kobj;

	/* walk up the ancestors until we hit the one pointing to the
	 * root.
	 * Add 1 to strlen for leading '/' of each level.
	 */
	do {
		if (kobject_name(parent) == NULL)
			return 0;
		length += strlen(kobject_name(parent)) + 1;
		parent = parent->parent;
	} while (parent);
	return length;
}

static void fill_kobj_path(struct kobject *kobj, char *path, int length)
{
	struct kobject *parent;

	--length;
	for (parent = kobj; parent; parent = parent->parent) {
		int cur = strlen(kobject_name(parent));
		/* back up enough to print this name with '/' */
		length -= cur;
		memcpy(path + length, kobject_name(parent), cur);
		*(path + --length) = '/';
	}

	pr_debug("kobject: '%s' (%p): %s: path = '%s'\n", kobject_name(kobj),
		 kobj, __func__, path);
}

/**
 * kobject_get_path() - Allocate memory and fill in the path for @kobj.
 * @kobj:	kobject in question, with which to build the path
 * @gfp_mask:	the allocation type used to allocate the path
 *
 * Return: The newly allocated memory, caller must free with kfree().
 */
char *kobject_get_path(struct kobject *kobj, gfp_t gfp_mask)
{
	char *path;
	int len;

	len = get_kobj_path_length(kobj);
	if (len == 0)
		return NULL;
	path = kzalloc(len, gfp_mask);
	if (!path)
		return NULL;
	fill_kobj_path(kobj, path, len);

	return path;
}
EXPORT_SYMBOL_GPL(kobject_get_path);

/* add the kobject to its kset's list */
static void kobj_kset_join(struct kobject *kobj)
{
	if (!kobj->kset)
		return;

	kset_get(kobj->kset);
	spin_lock(&kobj->kset->list_lock);
	list_add_tail(&kobj->entry, &kobj->kset->list);
	spin_unlock(&kobj->kset->list_lock);
}

/* remove the kobject from its kset's list */
static void kobj_kset_leave(struct kobject *kobj)
{
	if (!kobj->kset)
		return;

	spin_lock(&kobj->kset->list_lock);
	list_del_init(&kobj->entry);
	spin_unlock(&kobj->kset->list_lock);