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DEFINITIONS
This source file includes following definitions.
- fill_read_buffer
- sysfs_read_file
- fill_write_buffer
- flush_write_buffer
- sysfs_write_file
- sysfs_get_open_dirent
- sysfs_put_open_dirent
- sysfs_open_file
- sysfs_release
- sysfs_poll
- sysfs_notify
- sysfs_add_file_mode
- sysfs_add_file
- sysfs_create_file
- sysfs_add_file_to_group
- sysfs_chmod_file
- sysfs_remove_file
- sysfs_remove_file_from_group
- sysfs_schedule_callback_work
- sysfs_schedule_callback
/*
* fs/sysfs/file.c - sysfs regular (text) file implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
*
* This file is released under the GPLv2.
*
* Please see Documentation/filesystems/sysfs.txt for more information.
*/
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/kallsyms.h>
#include <linux/slab.h>
#include <linux/fsnotify.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>
#include "sysfs.h"
/*
* There's one sysfs_buffer for each open file and one
* sysfs_open_dirent for each sysfs_dirent with one or more open
* files.
*
* filp->private_data points to sysfs_buffer and
* sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open
* is protected by sysfs_open_dirent_lock.
*/
static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
struct sysfs_open_dirent {
atomic_t refcnt;
atomic_t event;
wait_queue_head_t poll;
struct list_head buffers; /* goes through sysfs_buffer.list */
};
struct sysfs_buffer {
size_t count;
loff_t pos;
char * page;
struct sysfs_ops * ops;
struct mutex mutex;
int needs_read_fill;
int event;
struct list_head list;
};
/**
* fill_read_buffer - allocate and fill buffer from object.
* @dentry: dentry pointer.
* @buffer: data buffer for file.
*
* Allocate @buffer->page, if it hasn't been already, then call the
* kobject's show() method to fill the buffer with this attribute's
* data.
* This is called only once, on the file's first read unless an error
* is returned.
*/
static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
{
struct sysfs_dirent *attr_sd = dentry->d_fsdata;
struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
struct sysfs_ops * ops = buffer->ops;
int ret = 0;
ssize_t count;
if (!buffer->page)
buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
if (!buffer->page)
return -ENOMEM;
/* need attr_sd for attr and ops, its parent for kobj */
if (!sysfs_get_active_two(attr_sd))
return -ENODEV;
buffer->event = atomic_read(&attr_sd->s_attr.open->event);
count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
sysfs_put_active_two(attr_sd);
/*
* The code works fine with PAGE_SIZE return but it's likely to
* indicate truncated result or overflow in normal use cases.
*/
if (count >= (ssize_t)PAGE_SIZE) {
print_symbol("fill_read_buffer: %s returned bad count\n",
(unsigned long)ops->show);
/* Try to struggle along */
count = PAGE_SIZE - 1;
}
if (count >= 0) {
buffer->needs_read_fill = 0;
buffer->count = count;
} else {
ret = count;
}
return ret;
}
/**
* sysfs_read_file - read an attribute.
* @file: file pointer.
* @buf: buffer to fill.
* @count: number of bytes to read.
* @ppos: starting offset in file.
*
* Userspace wants to read an attribute file. The attribute descriptor
* is in the file's ->d_fsdata. The target object is in the directory's
* ->d_fsdata.
*
* We call fill_read_buffer() to allocate and fill the buffer from the
* object's show() method exactly once (if the read is happening from
* the beginning of the file). That should fill the entire buffer with
* all the data the object has to offer for that attribute.
* We then call flush_read_buffer() to copy the buffer to userspace
* in the increments specified.
*/
static ssize_t
sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct sysfs_buffer * buffer = file->private_data;
ssize_t retval = 0;
mutex_lock(&buffer->mutex);
if (buffer->needs_read_fill || *ppos == 0) {
retval = fill_read_buffer(file->f_path.dentry,buffer);
if (retval)
goto out;
}
pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
__func__, count, *ppos, buffer->page);
retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
buffer->count);
out:
mutex_unlock(&buffer->mutex);
return retval;
}
/**
* fill_write_buffer - copy buffer from userspace.
* @buffer: data buffer for file.
* @buf: data from user.
* @count: number of bytes in @userbuf.
*
* Allocate @buffer->page if it hasn't been already, then
* copy the user-supplied buffer into it.
*/
static int
fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
{
int error;
if (!buffer->page)
buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
if (!buffer->page)
return -ENOMEM;
if (count >= PAGE_SIZE)
count = PAGE_SIZE - 1;
error = copy_from_user(buffer->page,buf,count);
buffer->needs_read_fill = 1;
/* if buf is assumed to contain a string, terminate it by \0,
so e.g. sscanf() can scan the string easily */
buffer->page[count] = 0;
return error ? -EFAULT : count;
}
/**
* flush_write_buffer - push buffer to kobject.
* @dentry: dentry to the attribute
* @buffer: data buffer for file.
* @count: number of bytes
*
* Get the correct pointers for the kobject and the attribute we're
* dealing with, then call the store() method for the attribute,
* passing the buffer that we acquired in fill_write_buffer().
*/
static int
flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
{
struct sysfs_dirent *attr_sd = dentry->d_fsdata;
struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
struct sysfs_ops * ops = buffer->ops;
int rc;
/* need attr_sd for attr and ops, its parent for kobj */
if (!sysfs_get_active_two(attr_sd))
return -ENODEV;
rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);
sysfs_put_active_two(attr_sd);
return rc;
}
/**
* sysfs_write_file - write an attribute.
* @file: file pointer
* @buf: data to write
* @count: number of bytes
* @ppos: starting offset
*
* Similar to sysfs_read_file(), though working in the opposite direction.
* We allocate and fill the data from the user in fill_write_buffer(),
* then push it to the kobject in flush_write_buffer().
* There is no easy way for us to know if userspace is only doing a partial
* write, so we don't support them. We expect the entire buffer to come
* on the first write.
* Hint: if you're writing a value, first read the file, modify only the
* the value you're changing, then write entire buffer back.
*/
static ssize_t
sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
struct sysfs_buffer * buffer = file->private_data;
ssize_t len;
mutex_lock(&buffer->mutex);
len = fill_write_buffer(buffer, buf, count);
if (len > 0)
len = flush_write_buffer(file->f_path.dentry, buffer, len);
if (len > 0)
*ppos += len;
mutex_unlock(&buffer->mutex);
return len;
}
/**
* sysfs_get_open_dirent - get or create sysfs_open_dirent
* @sd: target sysfs_dirent
* @buffer: sysfs_buffer for this instance of open
*
* If @sd->s_attr.open exists, increment its reference count;
* otherwise, create one. @buffer is chained to the buffers
* list.
*
* LOCKING:
* Kernel thread context (may sleep).
*
* RETURNS:
* 0 on success, -errno on failure.
*/
static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
struct sysfs_buffer *buffer)
{
struct sysfs_open_dirent *od, *new_od = NULL;
retry:
spin_lock(&sysfs_open_dirent_lock);
if (!sd->s_attr.open && new_od) {
sd->s_attr.open = new_od;
new_od = NULL;
}
od = sd->s_attr.open;
if (od) {
atomic_inc(&od->refcnt);
list_add_tail(&buffer->list, &od->buffers);
}
spin_unlock(&sysfs_open_dirent_lock);
if (od) {
kfree(new_od);
return 0;
}
/* not there, initialize a new one and retry */
new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
if (!new_od)
return -ENOMEM;
atomic_set(&new_od->refcnt, 0);
atomic_set(&new_od->event, 1);
init_waitqueue_head(&new_od->poll);
INIT_LIST_HEAD(&new_od->buffers);
goto retry;
}
/**
* sysfs_put_open_dirent - put sysfs_open_dirent
* @sd: target sysfs_dirent
* @buffer: associated sysfs_buffer
*
* Put @sd->s_attr.open and unlink @buffer from the buffers list.
* If reference count reaches zero, disassociate and free it.
*
* LOCKING:
* None.
*/
static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
struct sysfs_buffer *buffer)
{
struct sysfs_open_dirent *od = sd->s_attr.open;
spin_lock(&sysfs_open_dirent_lock);
list_del(&buffer->list);
if (atomic_dec_and_test(&od->refcnt))
sd->s_attr.open = NULL;
else
od = NULL;
spin_unlock(&sysfs_open_dirent_lock);
kfree(od);
}
static int sysfs_open_file(struct inode *inode, struct file *file)
{
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
struct sysfs_buffer *buffer;
struct sysfs_ops *ops;
int error = -EACCES;
/* need attr_sd for attr and ops, its parent for kobj */
if (!sysfs_get_active_two(attr_sd))
return -ENODEV;
/* every kobject with an attribute needs a ktype assigned */
if (kobj->ktype && kobj->ktype->sysfs_ops)
ops = kobj->ktype->sysfs_ops;
else {
WARN(1, KERN_ERR "missing sysfs attribute operations for "
"kobject: %s\n", kobject_name(kobj));
goto err_out;
}
/* File needs write support.
* The inode's perms must say it's ok,
* and we must have a store method.
*/
if (file->f_mode & FMODE_WRITE) {
if (!(inode->i_mode & S_IWUGO) || !ops->store)
goto err_out;
}
/* File needs read support.
* The inode's perms must say it's ok, and we there
* must be a show method for it.
*/
if (file->f_mode & FMODE_READ) {
if (!(inode->i_mode & S_IRUGO) || !ops->show)
goto err_out;
}
/* No error? Great, allocate a buffer for the file, and store it
* it in file->private_data for easy access.
*/
error = -ENOMEM;
buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
if (!buffer)
goto err_out;
mutex_init(&buffer->mutex);
buffer->needs_read_fill = 1;
buffer->ops = ops;
file->private_data = buffer;
/* make sure we have open dirent struct */
error = sysfs_get_open_dirent(attr_sd, buffer);
if (error)
goto err_free;
/* open succeeded, put active references */
sysfs_put_active_two(attr_sd);
return 0;
err_free:
kfree(buffer);
err_out:
sysfs_put_active_two(attr_sd);
return error;
}
static int sysfs_release(struct inode *inode, struct file *filp)
{
struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
struct sysfs_buffer *buffer = filp->private_data;
sysfs_put_open_dirent(sd, buffer);
if (buffer->page)
free_page((unsigned long)buffer->page);
kfree(buffer);
return 0;
}
/* Sysfs attribute files are pollable. The idea is that you read
* the content and then you use 'poll' or 'select' to wait for
* the content to change. When the content changes (assuming the
* manager for the kobject supports notification), poll will
* return POLLERR|POLLPRI, and select will return the fd whether
* it is waiting for read, write, or exceptions.
* Once poll/select indicates that the value has changed, you
* need to close and re-open the file, or seek to 0 and read again.
* Reminder: this only works for attributes which actively support
* it, and it is not possible to test an attribute from userspace
* to see if it supports poll (Neither 'poll' nor 'select' return
* an appropriate error code). When in doubt, set a suitable timeout value.
*/
static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
{
struct sysfs_buffer * buffer = filp->private_data;
struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
struct sysfs_open_dirent *od = attr_sd->s_attr.open;
/* need parent for the kobj, grab both */
if (!sysfs_get_active_two(attr_sd))
goto trigger;
poll_wait(filp, &od->poll, wait);
sysfs_put_active_two(attr_sd);
if (buffer->event != atomic_read(&od->event))
goto trigger;
return 0;
trigger:
buffer->needs_read_fill = 1;
return POLLERR|POLLPRI;
}
void sysfs_notify(struct kobject *k, char *dir, char *attr)
{
struct sysfs_dirent *sd = k->sd;
mutex_lock(&sysfs_mutex);
if (sd && dir)
sd = sysfs_find_dirent(sd, dir);
if (sd && attr)
sd = sysfs_find_dirent(sd, attr);
if (sd) {
struct sysfs_open_dirent *od;
spin_lock(&sysfs_open_dirent_lock);
od = sd->s_attr.open;
if (od) {
atomic_inc(&od->event);
wake_up_interruptible(&od->poll);
}
spin_unlock(&sysfs_open_dirent_lock);
}
mutex_unlock(&sysfs_mutex);
}
EXPORT_SYMBOL_GPL(sysfs_notify);
const struct file_operations sysfs_file_operations = {
.read = sysfs_read_file,
.write = sysfs_write_file,
.llseek = generic_file_llseek,
.open = sysfs_open_file,
.release = sysfs_release,
.poll = sysfs_poll,
};
int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
const struct attribute *attr, int type, mode_t amode)
{
umode_t mode = (amode & S_IALLUGO) | S_IFREG;
struct sysfs_addrm_cxt acxt;
struct sysfs_dirent *sd;
int rc;
sd = sysfs_new_dirent(attr->name, mode, type);
if (!sd)
return -ENOMEM;
sd->s_attr.attr = (void *)attr;
sysfs_addrm_start(&acxt, dir_sd);
rc = sysfs_add_one(&acxt, sd);
sysfs_addrm_finish(&acxt);
if (rc)
sysfs_put(sd);
return rc;
}
int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
int type)
{
return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
}
/**
* sysfs_create_file - create an attribute file for an object.
* @kobj: object we're creating for.
* @attr: attribute descriptor.
*/
int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
{
BUG_ON(!kobj || !kobj->sd || !attr);
return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
}
/**
* sysfs_add_file_to_group - add an attribute file to a pre-existing group.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
* @group: group name.
*/
int sysfs_add_file_to_group(struct kobject *kobj,
const struct attribute *attr, const char *group)
{
struct sysfs_dirent *dir_sd;
int error;
if (group)
dir_sd = sysfs_get_dirent(kobj->sd, group);
else
dir_sd = sysfs_get(kobj->sd);
if (!dir_sd)
return -ENOENT;
error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
sysfs_put(dir_sd);
return error;
}
EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
/**
* sysfs_chmod_file - update the modified mode value on an object attribute.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
* @mode: file permissions.
*
*/
int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
{
struct sysfs_dirent *victim_sd = NULL;
struct dentry *victim = NULL;
struct inode * inode;
struct iattr newattrs;
int rc;
rc = -ENOENT;
victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
if (!victim_sd)
goto out;
mutex_lock(&sysfs_rename_mutex);
victim = sysfs_get_dentry(victim_sd);
mutex_unlock(&sysfs_rename_mutex);
if (IS_ERR(victim)) {
rc = PTR_ERR(victim);
victim = NULL;
goto out;
}
inode = victim->d_inode;
mutex_lock(&inode->i_mutex);
newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
newattrs.ia_ctime = current_fs_time(inode->i_sb);
rc = sysfs_setattr(victim, &newattrs);
if (rc == 0) {
fsnotify_change(victim, newattrs.ia_valid);
mutex_lock(&sysfs_mutex);
victim_sd->s_mode = newattrs.ia_mode;
mutex_unlock(&sysfs_mutex);
}
mutex_unlock(&inode->i_mutex);
out:
dput(victim);
sysfs_put(victim_sd);
return rc;
}
EXPORT_SYMBOL_GPL(sysfs_chmod_file);
/**
* sysfs_remove_file - remove an object attribute.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
*
* Hash the attribute name and kill the victim.
*/
void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
{
sysfs_hash_and_remove(kobj->sd, attr->name);
}
/**
* sysfs_remove_file_from_group - remove an attribute file from a group.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
* @group: group name.
*/
void sysfs_remove_file_from_group(struct kobject *kobj,
const struct attribute *attr, const char *group)
{
struct sysfs_dirent *dir_sd;
if (group)
dir_sd = sysfs_get_dirent(kobj->sd, group);
else
dir_sd = sysfs_get(kobj->sd);
if (dir_sd) {
sysfs_hash_and_remove(dir_sd, attr->name);
sysfs_put(dir_sd);
}
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
struct sysfs_schedule_callback_struct {
struct kobject *kobj;
void (*func)(void *);
void *data;
struct module *owner;
struct work_struct work;
};
static void sysfs_schedule_callback_work(struct work_struct *work)
{
struct sysfs_schedule_callback_struct *ss = container_of(work,
struct sysfs_schedule_callback_struct, work);
(ss->func)(ss->data);
kobject_put(ss->kobj);
module_put(ss->owner);
kfree(ss);
}
/**
* sysfs_schedule_callback - helper to schedule a callback for a kobject
* @kobj: object we're acting for.
* @func: callback function to invoke later.
* @data: argument to pass to @func.
* @owner: module owning the callback code
*
* sysfs attribute methods must not unregister themselves or their parent
* kobject (which would amount to the same thing). Attempts to do so will
* deadlock, since unregistration is mutually exclusive with driver
* callbacks.
*
* Instead methods can call this routine, which will attempt to allocate
* and schedule a workqueue request to call back @func with @data as its
* argument in the workqueue's process context. @kobj will be pinned
* until @func returns.
*
* Returns 0 if the request was submitted, -ENOMEM if storage could not
* be allocated, -ENODEV if a reference to @owner isn't available.
*/
int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
void *data, struct module *owner)
{
struct sysfs_schedule_callback_struct *ss;
if (!try_module_get(owner))
return -ENODEV;
ss = kmalloc(sizeof(*ss), GFP_KERNEL);
if (!ss) {
module_put(owner);
return -ENOMEM;
}
kobject_get(kobj);
ss->kobj = kobj;
ss->func = func;
ss->data = data;
ss->owner = owner;
INIT_WORK(&ss->work, sysfs_schedule_callback_work);
schedule_work(&ss->work);
return 0;
}
EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
EXPORT_SYMBOL_GPL(sysfs_create_file);
EXPORT_SYMBOL_GPL(sysfs_remove_file);