Quelle kobject.c Sprache: 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.
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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(const 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(const 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 bool kobj_ns_type_is_valid(enum kobj_ns_type type)
{
if ((type <= KOBJ_NS_TYPE_NONE) || (type >= KOBJ_NS_TYPES))
  return false;

return true;
}

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(!kobj_ns_type_is_valid(ops->type));
  BUG_ON(!kobj_ns_type_registered(ops->type));

  sysfs_enable_ns(kobj->sd);
}

return 0;
}

static int get_kobj_path_length(const struct kobject *kobj)
{
int length = 1;
const 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 int fill_kobj_path(const struct kobject *kobj, char *path, int length)
{
const 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;
  if (length <= 0)
   return -EINVAL;
  memcpy(path + length, kobject_name(parent), cur);
  *(path + --length) = '/';
}

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

return 0;
}

/**
* 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(const struct kobject *kobj, gfp_t gfp_mask)
{
char *path;
int len;

retry:
len = get_kobj_path_length(kobj);
if (len == 0)
  return NULL;
path = kzalloc(len, gfp_mask);
if (!path)
  return NULL;
if (fill_kobj_path(kobj, path, len)) {
  kfree(path);
  goto retry;
}

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

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;
  s = strreplace(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, const 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_lvl(KERN_ERR);
}

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

error:
pr_err("kobject (%p): %s\n", kobj, err_str);
dump_stack_lvl(KERN_ERR);
}
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("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_lvl(KERN_ERR);
  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, const 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;

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("'%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;

if (!kobj)
  return;

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;
const struct kobj_type *t = get_ktype(kobj);
const char *name = kobj->name;

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

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

/* free name if we allocated it */
if (name) {
  pr_debug("'%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_u32_below(4);
pr_info("'%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("(%p): %s\n", kobj, __func__);
kfree(kobj);
}

static const 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.
*/
static 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.
*
* NOTE: On error, the kset.kobj.name allocated by() kobj_set_name()
* is freed, it can not be used any more.
*/
int kset_register(struct kset *k)
{
int err;

if (!k)
  return -EINVAL;

if (!k->kobj.ktype) {
  pr_err("must have a ktype to be initialized properly!\n");
  return -EINVAL;
}

kset_init(k);
err = kobject_add_internal(&k->kobj);
if (err) {
  kfree_const(k->kobj.name);
  /* Set it to NULL to avoid accessing bad pointer in callers. */
  k->kobj.name = NULL;
  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("'%s' (%p): %s\n",
   kobject_name(kobj), kobj, __func__);
kfree(kset);
}

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

static const 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 (!kobj_ns_type_is_valid(type))
  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 (kobj_ns_type_is_valid(type))
  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(const 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(const 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 (kobj_ns_type_is_valid(type) && 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 (kobj_ns_type_is_valid(type) && 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);

void kobj_ns_drop(enum kobj_ns_type type, void *ns)
{
spin_lock(&kobj_ns_type_lock);
if (kobj_ns_type_is_valid(type) &&
     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);

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