Merge tag 'for-linus-5.9-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git...

[mirror_ubuntu-hirsute-kernel.git] / 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);
}

/*
 * populate_dir - populate directory with attributes.
 * @kobj: object we're working on.
 *
 * Most subsystems have a set of default attributes that are associated
 * with an object that registers with them.  This is a helper called during
 * object registration that loops through the default attributes of the
 * subsystem and creates attributes files for them in sysfs.
 */
static int populate_dir(struct kobject *kobj)
{
        struct kobj_type *t = get_ktype(kobj);
        struct attribute *attr;
        int error = 0;
        int i;

        if (t && t->default_attrs) {
                for (i = 0; (attr = t->default_attrs[i]) != NULL; i++) {
                        error = sysfs_create_file(kobj, attr);
                        if (error)
                                break;
                }
        }
        return error;
}

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;

        error = populate_dir(kobj);
        if (error) {
                sysfs_remove_dir(kobj);
                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);
        kset_put(kobj->kset);
}

static void kobject_init_internal(struct kobject *kobj)
{
        if (!kobj)
                return;
        kref_init(&kobj->kref);
        INIT_LIST_HEAD(&kobj->entry);
        kobj->state_in_sysfs = 0;
        kobj->state_add_uevent_sent = 0;
        kobj->state_remove_uevent_sent = 0;
        kobj->state_initialized = 1;
}


static int kobject_add_internal(struct kobject *kobj)
{
        int error = 0;
        struct kobject *parent;

        if (!kobj)
                return -ENOENT;

        if (!kobj->name || !kobj->name[0]) {
                WARN(1,
                     "kobject: (%p): attempted to be registered with empty name!\n",
                     kobj);
                return -EINVAL;
        }

        parent = kobject_get(kobj->parent);

        /* join kset if set, use it as parent if we do not already have one */
        if (kobj->kset) {
                if (!parent)
                        parent = kobject_get(&kobj->kset->kobj);
                kobj_kset_join(kobj);
                kobj->parent = parent;
        }

        pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'\n",
                 kobject_name(kobj), kobj, __func__,
                 parent ? kobject_name(parent) : "<NULL>",
                 kobj->kset ? kobject_name(&kobj->kset->kobj) : "<NULL>");

        error = create_dir(kobj);
        if (error) {
                kobj_kset_leave(kobj);
                kobject_put(parent);
                kobj->parent = NULL;

                /* be noisy on error issues */
                if (error == -EEXIST)
                        pr_err("%s failed for %s with -EEXIST, don't try to register things with the same name in the same directory.\n",
                               __func__, kobject_name(kobj));
                else
                        pr_err("%s failed for %s (error: %d parent: %s)\n",
                               __func__, kobject_name(kobj), error,
                               parent ? kobject_name(parent) : "'none'");
        } else
                kobj->state_in_sysfs = 1;

        return error;
}

/**
 * kobject_set_name_vargs() - Set the name of a kobject.
 * @kobj: struct kobject to set the name of
 * @fmt: format string used to build the name
 * @vargs: vargs to format the string.
 */
int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
                                  va_list vargs)
{
        const char *s;

        if (kobj->name && !fmt)
                return 0;

        s = kvasprintf_const(GFP_KERNEL, fmt, vargs);
        if (!s)
                return -ENOMEM;

        /*
         * ewww... some of these buggers have '/' in the name ... If
         * that's the case, we need to make sure we have an actual
         * allocated copy to modify, since kvasprintf_const may have
         * returned something from .rodata.
         */
        if (strchr(s, '/')) {
                char *t;

                t = kstrdup(s, GFP_KERNEL);
                kfree_const(s);
                if (!t)
                        return -ENOMEM;
                strreplace(t, '/', '!');
                s = t;
        }
        kfree_const(kobj->name);
        kobj->name = s;

        return 0;
}

/**
 * kobject_set_name() - Set the name of a kobject.
 * @kobj: struct kobject to set the name of
 * @fmt: format string used to build the name
 *
 * This sets the name of the kobject.  If you have already added the
 * kobject to the system, you must call kobject_rename() in order to
 * change the name of the kobject.
 */
int kobject_set_name(struct kobject *kobj, const char *fmt, ...)
{
        va_list vargs;
        int retval;

        va_start(vargs, fmt);
        retval = kobject_set_name_vargs(kobj, fmt, vargs);
        va_end(vargs);

        return retval;
}
EXPORT_SYMBOL(kobject_set_name);

/**
 * kobject_init() - Initialize a kobject structure.
 * @kobj: pointer to the kobject to initialize
 * @ktype: pointer to the ktype for this kobject.
 *
 * This function will properly initialize a kobject such that it can then
 * be passed to the kobject_add() call.
 *
 * After this function is called, the kobject MUST be cleaned up by a call
 * to kobject_put(), not by a call to kfree directly to ensure that all of
 * the memory is cleaned up properly.
 */
void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
{
        char *err_str;

        if (!kobj) {
                err_str = "invalid kobject pointer!";
                goto error;
        }
        if (!ktype) {
                err_str = "must have a ktype to be initialized properly!\n";
                goto error;
        }
        if (kobj->state_initialized) {
                /* do not error out as sometimes we can recover */
                pr_err("kobject (%p): tried to init an initialized object, something is seriously wrong.\n",
                       kobj);
                dump_stack();
        }

        kobject_init_internal(kobj);
        kobj->ktype = ktype;
        return;

error:
        pr_err("kobject (%p): %s\n", kobj, err_str);
        dump_stack();
}
EXPORT_SYMBOL(kobject_init);

static __printf(3, 0) int kobject_add_varg(struct kobject *kobj,
                                           struct kobject *parent,
                                           const char *fmt, va_list vargs)
{
        int retval;

        retval = kobject_set_name_vargs(kobj, fmt, vargs);
        if (retval) {
                pr_err("kobject: can not set name properly!\n");
                return retval;
        }
        kobj->parent = parent;
        return kobject_add_internal(kobj);
}

/**
 * kobject_add() - The main kobject add function.
 * @kobj: the kobject to add
 * @parent: pointer to the parent of the kobject.
 * @fmt: format to name the kobject with.
 *
 * The kobject name is set and added to the kobject hierarchy in this
 * function.
 *
 * If @parent is set, then the parent of the @kobj will be set to it.
 * If @parent is NULL, then the parent of the @kobj will be set to the
 * kobject associated with the kset assigned to this kobject.  If no kset
 * is assigned to the kobject, then the kobject will be located in the
 * root of the sysfs tree.
 *
 * Note, no "add" uevent will be created with this call, the caller should set
 * up all of the necessary sysfs files for the object and then call
 * kobject_uevent() with the UEVENT_ADD parameter to ensure that
 * userspace is properly notified of this kobject's creation.
 *
 * Return: If this function returns an error, kobject_put() must be
 *         called to properly clean up the memory associated with the
 *         object.  Under no instance should the kobject that is passed
 *         to this function be directly freed with a call to kfree(),
 *         that can leak memory.
 *
 *         If this function returns success, kobject_put() must also be called
 *         in order to properly clean up the memory associated with the object.
 *
 *         In short, once this function is called, kobject_put() MUST be called
 *         when the use of the object is finished in order to properly free
 *         everything.
 */
int kobject_add(struct kobject *kobj, struct kobject *parent,
                const char *fmt, ...)
{
        va_list args;
        int retval;

        if (!kobj)
                return -EINVAL;

        if (!kobj->state_initialized) {
                pr_err("kobject '%s' (%p): tried to add an uninitialized object, something is seriously wrong.\n",
                       kobject_name(kobj), kobj);
                dump_stack();
                return -EINVAL;
        }
        va_start(args, fmt);
        retval = kobject_add_varg(kobj, parent, fmt, args);
        va_end(args);

        return retval;
}
EXPORT_SYMBOL(kobject_add);

/**
 * kobject_init_and_add() - Initialize a kobject structure and add it to
 *                          the kobject hierarchy.
 * @kobj: pointer to the kobject to initialize
 * @ktype: pointer to the ktype for this kobject.
 * @parent: pointer to the parent of this kobject.
 * @fmt: the name of the kobject.
 *
 * This function combines the call to kobject_init() and kobject_add().
 *
 * If this function returns an error, kobject_put() must be called to
 * properly clean up the memory associated with the object.  This is the
 * same type of error handling after a call to kobject_add() and kobject
 * lifetime rules are the same here.
 */
int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype,
                         struct kobject *parent, const char *fmt, ...)
{
        va_list args;
        int retval;

        kobject_init(kobj, ktype);

        va_start(args, fmt);
        retval = kobject_add_varg(kobj, parent, fmt, args);
        va_end(args);

        return retval;
}
EXPORT_SYMBOL_GPL(kobject_init_and_add);

/**
 * kobject_rename() - Change the name of an object.
 * @kobj: object in question.
 * @new_name: object's new name
 *
 * It is the responsibility of the caller to provide mutual
 * exclusion between two different calls of kobject_rename
 * on the same kobject and to ensure that new_name is valid and
 * won't conflict with other kobjects.
 */
int kobject_rename(struct kobject *kobj, const char *new_name)
{
        int error = 0;
        const char *devpath = NULL;
        const char *dup_name = NULL, *name;
        char *devpath_string = NULL;
        char *envp[2];

        kobj = kobject_get(kobj);
        if (!kobj)
                return -EINVAL;
        if (!kobj->parent) {
                kobject_put(kobj);
                return -EINVAL;
        }

        devpath = kobject_get_path(kobj, GFP_KERNEL);
        if (!devpath) {
                error = -ENOMEM;
                goto out;
        }
        devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);
        if (!devpath_string) {
                error = -ENOMEM;
                goto out;
        }
        sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);
        envp[0] = devpath_string;
        envp[1] = NULL;

        name = dup_name = kstrdup_const(new_name, GFP_KERNEL);
        if (!name) {
                error = -ENOMEM;
                goto out;
        }

        error = sysfs_rename_dir_ns(kobj, new_name, kobject_namespace(kobj));
        if (error)
                goto out;

        /* Install the new kobject name */
        dup_name = kobj->name;
        kobj->name = name;

        /* This function is mostly/only used for network interface.
         * Some hotplug package track interfaces by their name and
         * therefore want to know when the name is changed by the user. */
        kobject_uevent_env(kobj, KOBJ_MOVE, envp);

out:
        kfree_const(dup_name);
        kfree(devpath_string);
        kfree(devpath);
        kobject_put(kobj);

        return error;
}
EXPORT_SYMBOL_GPL(kobject_rename);

/**
 * kobject_move() - Move object to another parent.
 * @kobj: object in question.
 * @new_parent: object's new parent (can be NULL)
 */
int kobject_move(struct kobject *kobj, struct kobject *new_parent)
{
        int error;
        struct kobject *old_parent;
        const char *devpath = NULL;
        char *devpath_string = NULL;
        char *envp[2];

        kobj = kobject_get(kobj);
        if (!kobj)
                return -EINVAL;
        new_parent = kobject_get(new_parent);
        if (!new_parent) {
                if (kobj->kset)
                        new_parent = kobject_get(&kobj->kset->kobj);
        }

        /* old object path */
        devpath = kobject_get_path(kobj, GFP_KERNEL);
        if (!devpath) {
                error = -ENOMEM;
                goto out;
        }
        devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);
        if (!devpath_string) {
                error = -ENOMEM;
                goto out;
        }
        sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);
        envp[0] = devpath_string;
        envp[1] = NULL;
        error = sysfs_move_dir_ns(kobj, new_parent, kobject_namespace(kobj));
        if (error)
                goto out;
        old_parent = kobj->parent;
        kobj->parent = new_parent;
        new_parent = NULL;
        kobject_put(old_parent);
        kobject_uevent_env(kobj, KOBJ_MOVE, envp);
out:
        kobject_put(new_parent);
        kobject_put(kobj);
        kfree(devpath_string);
        kfree(devpath);
        return error;
}
EXPORT_SYMBOL_GPL(kobject_move);

static void __kobject_del(struct kobject *kobj)
{
        struct kernfs_node *sd;
        const struct kobj_type *ktype;

        if (!kobj)
                return;

        sd = kobj->sd;
        ktype = get_ktype(kobj);

        if (ktype)
                sysfs_remove_groups(kobj, ktype->default_groups);

        /* send "remove" if the caller did not do it but sent "add" */
        if (kobj->state_add_uevent_sent && !kobj->state_remove_uevent_sent) {
                pr_debug("kobject: '%s' (%p): auto cleanup 'remove' event\n",
                         kobject_name(kobj), kobj);
                kobject_uevent(kobj, KOBJ_REMOVE);
        }

        sysfs_remove_dir(kobj);
        sysfs_put(sd);

        kobj->state_in_sysfs = 0;
        kobj_kset_leave(kobj);
        kobj->parent = NULL;
}

/**
 * kobject_del() - Unlink kobject from hierarchy.
 * @kobj: object.
 *
 * This is the function that should be called to delete an object
 * successfully added via kobject_add().
 */
void kobject_del(struct kobject *kobj)
{
        struct kobject *parent = kobj->parent;

        __kobject_del(kobj);
        kobject_put(parent);
}
EXPORT_SYMBOL(kobject_del);

/**
 * kobject_get() - Increment refcount for object.
 * @kobj: object.
 */
struct kobject *kobject_get(struct kobject *kobj)
{
        if (kobj) {
                if (!kobj->state_initialized)
                        WARN(1, KERN_WARNING
                                "kobject: '%s' (%p): is not initialized, yet kobject_get() is being called.\n",
                             kobject_name(kobj), kobj);
                kref_get(&kobj->kref);
        }
        return kobj;
}
EXPORT_SYMBOL(kobject_get);

struct kobject * __must_check kobject_get_unless_zero(struct kobject *kobj)
{
        if (!kobj)
                return NULL;
        if (!kref_get_unless_zero(&kobj->kref))
                kobj = NULL;
        return kobj;
}
EXPORT_SYMBOL(kobject_get_unless_zero);

/*
 * kobject_cleanup - free kobject resources.
 * @kobj: object to cleanup
 */
static void kobject_cleanup(struct kobject *kobj)
{
        struct kobject *parent = kobj->parent;
        struct kobj_type *t = get_ktype(kobj);
        const char *name = kobj->name;

        pr_debug("kobject: '%s' (%p): %s, parent %p\n",
                 kobject_name(kobj), kobj, __func__, kobj->parent);

        if (t && !t->release)
                pr_debug("kobject: '%s' (%p): does not have a release() function, it is broken and must be fixed. See Documentation/core-api/kobject.rst.\n",
                         kobject_name(kobj), kobj);

        /* remove from sysfs if the caller did not do it */
        if (kobj->state_in_sysfs) {
                pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n",
                         kobject_name(kobj), kobj);
                __kobject_del(kobj);
        } else {
                /* avoid dropping the parent reference unnecessarily */
                parent = NULL;
        }

        if (t && t->release) {
                pr_debug("kobject: '%s' (%p): calling ktype release\n",
                         kobject_name(kobj), kobj);
                t->release(kobj);
        }

        /* free name if we allocated it */
        if (name) {
                pr_debug("kobject: '%s': free name\n", name);
                kfree_const(name);
        }

        kobject_put(parent);
}

#ifdef CONFIG_DEBUG_KOBJECT_RELEASE
static void kobject_delayed_cleanup(struct work_struct *work)
{
        kobject_cleanup(container_of(to_delayed_work(work),
                                     struct kobject, release));
}
#endif

static void kobject_release(struct kref *kref)
{
        struct kobject *kobj = container_of(kref, struct kobject, kref);
#ifdef CONFIG_DEBUG_KOBJECT_RELEASE
        unsigned long delay = HZ + HZ * (get_random_int() & 0x3);
        pr_info("kobject: '%s' (%p): %s, parent %p (delayed %ld)\n",
                 kobject_name(kobj), kobj, __func__, kobj->parent, delay);
        INIT_DELAYED_WORK(&kobj->release, kobject_delayed_cleanup);

        schedule_delayed_work(&kobj->release, delay);
#else
        kobject_cleanup(kobj);
#endif
}

/**
 * kobject_put() - Decrement refcount for object.
 * @kobj: object.
 *
 * Decrement the refcount, and if 0, call kobject_cleanup().
 */
void kobject_put(struct kobject *kobj)
{
        if (kobj) {
                if (!kobj->state_initialized)
                        WARN(1, KERN_WARNING
                                "kobject: '%s' (%p): is not initialized, yet kobject_put() is being called.\n",
                             kobject_name(kobj), kobj);
                kref_put(&kobj->kref, kobject_release);
        }
}
EXPORT_SYMBOL(kobject_put);

static void dynamic_kobj_release(struct kobject *kobj)
{
        pr_debug("kobject: (%p): %s\n", kobj, __func__);
        kfree(kobj);
}

static struct kobj_type dynamic_kobj_ktype = {
        .release        = dynamic_kobj_release,
        .sysfs_ops      = &kobj_sysfs_ops,
};

/**
 * kobject_create() - Create a struct kobject dynamically.
 *
 * This function creates a kobject structure dynamically and sets it up
 * to be a "dynamic" kobject with a default release function set up.
 *
 * If the kobject was not able to be created, NULL will be returned.
 * The kobject structure returned from here must be cleaned up with a
 * call to kobject_put() and not kfree(), as kobject_init() has
 * already been called on this structure.
 */
struct kobject *kobject_create(void)
{
        struct kobject *kobj;

        kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
        if (!kobj)
                return NULL;

        kobject_init(kobj, &dynamic_kobj_ktype);
        return kobj;
}

/**
 * kobject_create_and_add() - Create a struct kobject dynamically and
 *                            register it with sysfs.
 * @name: the name for the kobject
 * @parent: the parent kobject of this kobject, if any.
 *
 * This function creates a kobject structure dynamically and registers it
 * with sysfs.  When you are finished with this structure, call
 * kobject_put() and the structure will be dynamically freed when
 * it is no longer being used.
 *
 * If the kobject was not able to be created, NULL will be returned.
 */
struct kobject *kobject_create_and_add(const char *name, struct kobject *parent)
{
        struct kobject *kobj;
        int retval;

        kobj = kobject_create();
        if (!kobj)
                return NULL;

        retval = kobject_add(kobj, parent, "%s", name);
        if (retval) {
                pr_warn("%s: kobject_add error: %d\n", __func__, retval);
                kobject_put(kobj);
                kobj = NULL;
        }
        return kobj;
}
EXPORT_SYMBOL_GPL(kobject_create_and_add);

/**
 * kset_init() - Initialize a kset for use.
 * @k: kset
 */
void kset_init(struct kset *k)
{
        kobject_init_internal(&k->kobj);
        INIT_LIST_HEAD(&k->list);
        spin_lock_init(&k->list_lock);
}

/* default kobject attribute operations */
static ssize_t kobj_attr_show(struct kobject *kobj, struct attribute *attr,
                              char *buf)
{
        struct kobj_attribute *kattr;
        ssize_t ret = -EIO;

        kattr = container_of(attr, struct kobj_attribute, attr);
        if (kattr->show)
                ret = kattr->show(kobj, kattr, buf);
        return ret;
}

static ssize_t kobj_attr_store(struct kobject *kobj, struct attribute *attr,
                               const char *buf, size_t count)
{
        struct kobj_attribute *kattr;
        ssize_t ret = -EIO;

        kattr = container_of(attr, struct kobj_attribute, attr);
        if (kattr->store)
                ret = kattr->store(kobj, kattr, buf, count);
        return ret;
}

const struct sysfs_ops kobj_sysfs_ops = {
        .show   = kobj_attr_show,
        .store  = kobj_attr_store,
};
EXPORT_SYMBOL_GPL(kobj_sysfs_ops);

/**
 * kset_register() - Initialize and add a kset.
 * @k: kset.
 */
int kset_register(struct kset *k)
{
        int err;

        if (!k)
                return -EINVAL;

        kset_init(k);
        err = kobject_add_internal(&k->kobj);
        if (err)
                return err;
        kobject_uevent(&k->kobj, KOBJ_ADD);
        return 0;
}
EXPORT_SYMBOL(kset_register);

/**
 * kset_unregister() - Remove a kset.
 * @k: kset.
 */
void kset_unregister(struct kset *k)
{
        if (!k)
                return;
        kobject_del(&k->kobj);
        kobject_put(&k->kobj);
}
EXPORT_SYMBOL(kset_unregister);

/**
 * kset_find_obj() - Search for object in kset.
 * @kset: kset we're looking in.
 * @name: object's name.
 *
 * Lock kset via @kset->subsys, and iterate over @kset->list,
 * looking for a matching kobject. If matching object is found
 * take a reference and return the object.
 */
struct kobject *kset_find_obj(struct kset *kset, const char *name)
{
        struct kobject *k;
        struct kobject *ret = NULL;

        spin_lock(&kset->list_lock);

        list_for_each_entry(k, &kset->list, entry) {
                if (kobject_name(k) && !strcmp(kobject_name(k), name)) {
                        ret = kobject_get_unless_zero(k);
                        break;
                }
        }

        spin_unlock(&kset->list_lock);
        return ret;
}
EXPORT_SYMBOL_GPL(kset_find_obj);

static void kset_release(struct kobject *kobj)
{
        struct kset *kset = container_of(kobj, struct kset, kobj);
        pr_debug("kobject: '%s' (%p): %s\n",
                 kobject_name(kobj), kobj, __func__);
        kfree(kset);
}

static void kset_get_ownership(struct kobject *kobj, kuid_t *uid, kgid_t *gid)
{
        if (kobj->parent)
                kobject_get_ownership(kobj->parent, uid, gid);
}

static struct kobj_type kset_ktype = {
        .sysfs_ops      = &kobj_sysfs_ops,
        .release        = kset_release,
        .get_ownership  = kset_get_ownership,
};

/**
 * kset_create() - Create a struct kset dynamically.
 *
 * @name: the name for the kset
 * @uevent_ops: a struct kset_uevent_ops for the kset
 * @parent_kobj: the parent kobject of this kset, if any.
 *
 * This function creates a kset structure dynamically.  This structure can
 * then be registered with the system and show up in sysfs with a call to
 * kset_register().  When you are finished with this structure, if
 * kset_register() has been called, call kset_unregister() and the
 * structure will be dynamically freed when it is no longer being used.
 *
 * If the kset was not able to be created, NULL will be returned.
 */
static struct kset *kset_create(const char *name,
                                const struct kset_uevent_ops *uevent_ops,
                                struct kobject *parent_kobj)
{
        struct kset *kset;
        int retval;

        kset = kzalloc(sizeof(*kset), GFP_KERNEL);
        if (!kset)
                return NULL;
        retval = kobject_set_name(&kset->kobj, "%s", name);
        if (retval) {
                kfree(kset);
                return NULL;
        }
        kset->uevent_ops = uevent_ops;
        kset->kobj.parent = parent_kobj;

        /*
         * The kobject of this kset will have a type of kset_ktype and belong to
         * no kset itself.  That way we can properly free it when it is
         * finished being used.
         */
        kset->kobj.ktype = &kset_ktype;
        kset->kobj.kset = NULL;

        return kset;
}

/**
 * kset_create_and_add() - Create a struct kset dynamically and add it to sysfs.
 *
 * @name: the name for the kset
 * @uevent_ops: a struct kset_uevent_ops for the kset
 * @parent_kobj: the parent kobject of this kset, if any.
 *
 * This function creates a kset structure dynamically and registers it
 * with sysfs.  When you are finished with this structure, call
 * kset_unregister() and the structure will be dynamically freed when it
 * is no longer being used.
 *
 * If the kset was not able to be created, NULL will be returned.
 */
struct kset *kset_create_and_add(const char *name,
                                 const struct kset_uevent_ops *uevent_ops,
                                 struct kobject *parent_kobj)
{
        struct kset *kset;
        int error;

        kset = kset_create(name, uevent_ops, parent_kobj);
        if (!kset)
                return NULL;
        error = kset_register(kset);
        if (error) {
                kfree(kset);
                return NULL;
        }
        return kset;
}
EXPORT_SYMBOL_GPL(kset_create_and_add);


static DEFINE_SPINLOCK(kobj_ns_type_lock);
static const struct kobj_ns_type_operations *kobj_ns_ops_tbl[KOBJ_NS_TYPES];

int kobj_ns_type_register(const struct kobj_ns_type_operations *ops)
{
        enum kobj_ns_type type = ops->type;
        int error;

        spin_lock(&kobj_ns_type_lock);

        error = -EINVAL;
        if (type >= KOBJ_NS_TYPES)
                goto out;

        error = -EINVAL;
        if (type <= KOBJ_NS_TYPE_NONE)
                goto out;

        error = -EBUSY;
        if (kobj_ns_ops_tbl[type])
                goto out;

        error = 0;
        kobj_ns_ops_tbl[type] = ops;

out:
        spin_unlock(&kobj_ns_type_lock);
        return error;
}

int kobj_ns_type_registered(enum kobj_ns_type type)
{
        int registered = 0;

        spin_lock(&kobj_ns_type_lock);
        if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES))
                registered = kobj_ns_ops_tbl[type] != NULL;
        spin_unlock(&kobj_ns_type_lock);

        return registered;
}

const struct kobj_ns_type_operations *kobj_child_ns_ops(struct kobject *parent)
{
        const struct kobj_ns_type_operations *ops = NULL;

        if (parent && parent->ktype && parent->ktype->child_ns_type)
                ops = parent->ktype->child_ns_type(parent);

        return ops;
}

const struct kobj_ns_type_operations *kobj_ns_ops(struct kobject *kobj)
{
        return kobj_child_ns_ops(kobj->parent);
}

bool kobj_ns_current_may_mount(enum kobj_ns_type type)
{
        bool may_mount = true;

        spin_lock(&kobj_ns_type_lock);
        if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
            kobj_ns_ops_tbl[type])
                may_mount = kobj_ns_ops_tbl[type]->current_may_mount();
        spin_unlock(&kobj_ns_type_lock);

        return may_mount;
}

void *kobj_ns_grab_current(enum kobj_ns_type type)
{
        void *ns = NULL;

        spin_lock(&kobj_ns_type_lock);
        if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
            kobj_ns_ops_tbl[type])
                ns = kobj_ns_ops_tbl[type]->grab_current_ns();
        spin_unlock(&kobj_ns_type_lock);

        return ns;
}
EXPORT_SYMBOL_GPL(kobj_ns_grab_current);

const void *kobj_ns_netlink(enum kobj_ns_type type, struct sock *sk)
{
        const void *ns = NULL;

        spin_lock(&kobj_ns_type_lock);
        if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
            kobj_ns_ops_tbl[type])
                ns = kobj_ns_ops_tbl[type]->netlink_ns(sk);
        spin_unlock(&kobj_ns_type_lock);

        return ns;
}

const void *kobj_ns_initial(enum kobj_ns_type type)
{
        const void *ns = NULL;

        spin_lock(&kobj_ns_type_lock);
        if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
            kobj_ns_ops_tbl[type])
                ns = kobj_ns_ops_tbl[type]->initial_ns();
        spin_unlock(&kobj_ns_type_lock);

        return ns;
}

void kobj_ns_drop(enum kobj_ns_type type, void *ns)
{
        spin_lock(&kobj_ns_type_lock);
        if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
            kobj_ns_ops_tbl[type] && kobj_ns_ops_tbl[type]->drop_ns)
                kobj_ns_ops_tbl[type]->drop_ns(ns);
        spin_unlock(&kobj_ns_type_lock);
}
EXPORT_SYMBOL_GPL(kobj_ns_drop);