/*
* file.c - operations for regular (text) files.
*/
#include <linux/module.h>
#include <linux/fsnotify.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <asm/uaccess.h>
#include <asm/semaphore.h>
#include "sysfs.h"
#define to_subsys(k) container_of(k,struct subsystem,kset.kobj)
#define to_sattr(a) container_of(a,struct subsys_attribute,attr)
/*
* Subsystem file operations.
* These operations allow subsystems to have files that can be
* read/written.
*/
static ssize_t
subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page)
{
struct subsystem * s = to_subsys(kobj);
struct subsys_attribute * sattr = to_sattr(attr);
ssize_t ret = -EIO;
if (sattr->show)
ret = sattr->show(s,page);
return ret;
}
static ssize_t
subsys_attr_store(struct kobject * kobj, struct attribute * attr,
const char * page, size_t count)
{
struct subsystem * s = to_subsys(kobj);
struct subsys_attribute * sattr = to_sattr(attr);
ssize_t ret = -EIO;
if (sattr->store)
ret = sattr->store(s,page,count);
return ret;
}
static struct sysfs_ops subsys_sysfs_ops = {
.show = subsys_attr_show,
.store = subsys_attr_store,
};
struct sysfs_buffer {
size_t count;
loff_t pos;
char * page;
struct sysfs_ops * ops;
struct semaphore sem;
int needs_read_fill;
int event;
};
/**
* 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.
*/
static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
{
struct sysfs_dirent * sd = dentry->d_fsdata;
struct attribute * attr = to_attr(dentry);
struct kobject * kobj = to_kobj(dentry->d_parent);
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;
buffer->event = atomic_read(&sd->s_event);
count = ops->show(kobj,attr,buffer->page);
buffer->needs_read_fill = 0;
BUG_ON(count > (ssize_t)PAGE_SIZE);
if (count >= 0)
buffer->count = count;
else
ret = count;
return ret;
}
/**
* flush_read_buffer - push buffer to userspace.
* @buffer: data buffer for file.
* @buf: user-passed buffer.
* @count: number of bytes requested.
* @ppos: file position.
*
* Copy the buffer we filled in fill_read_buffer() to userspace.
* This is done at the reader's leisure, copying and advancing
* the amount they specify each time.
* This may be called continuously until the buffer is empty.
*/
static int flush_read_buffer(struct sysfs_buffer * buffer, char __user * buf,
size_t count, loff_t * ppos)
{
int error;
if (*ppos > buffer->count)
return 0;
if (count > (buffer->count - *ppos))
count = buffer->count - *ppos;
error = copy_to_user(buf,buffer->page + *ppos,count);
if (!error)
*ppos += count;
return error ? -EFAULT : count;
}
/**
* 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;
down(&buffer->sem);
if (buffer->needs_read_fill) {
if ((retval = fill_read_buffer(file->f_dentry,buffer)))
goto out;
}
pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
__FUNCTION__, count, *ppos, buffer->page);
retval = flush_read_buffer(buffer,buf,count,ppos);
out:
up(&buffer->sem);
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 attribute * attr = to_attr(dentry);
struct kobject * kobj = to_kobj(dentry->d_parent);
struct sysfs_ops * ops = buffer->ops;
return ops->store(kobj,attr,buffer->page,count);
}
/**
* 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;
down(&buffer->sem);
len = fill_write_buffer(buffer, buf, count);
if (len > 0)
len = flush_write_buffer(file->f_dentry, buffer, len);
if (len > 0)
*ppos += len;
up(&buffer->sem);
return len;
}
static int check_perm(struct inode * inode, struct file * file)
{
struct kobject *kobj = sysfs_get_kobject(file->f_dentry->d_parent);
struct attribute * attr = to_attr(file->f_dentry);
struct sysfs_buffer * buffer;
struct sysfs_ops * ops = NULL;
int error = 0;
if (!kobj || !attr)
goto Einval;
/* Grab the module reference for this attribute if we have one */
if (!try_module_get(attr->owner)) {
error = -ENODEV;
goto Done;
}
/* if the kobject has no ktype, then we assume that it is a subsystem
* itself, and use ops for it.
*/
if (kobj->kset && kobj->kset->ktype)
ops = kobj->kset->ktype->sysfs_ops;
else if (kobj->ktype)
ops = kobj->ktype->sysfs_ops;
else
ops = &subsys_sysfs_ops;
/* No sysfs operations, either from having no subsystem,
* or the subsystem have no operations.
*/
if (!ops)
goto Eaccess;
/* 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 Eaccess;
}
/* 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 Eaccess;
}
/* No error? Great, allocate a buffer for the file, and store it
* it in file->private_data for easy access.
*/
buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
if (buffer) {
init_MUTEX(&buffer->sem);
buffer->needs_read_fill = 1;
buffer->ops = ops;
file->private_data = buffer;
} else
error = -ENOMEM;
goto Done;
Einval:
error = -EINVAL;
goto Done;
Eaccess:
error = -EACCES;
module_put(attr->owner);
Done:
if (error && kobj)
kobject_put(kobj);
return error;
}
static int sysfs_open_file(struct inode * inode, struct file * filp)
{
return check_perm(inode,filp);
}
static int sysfs_release(struct inode * inode, struct file * filp)
{
struct kobject * kobj = to_kobj(filp->f_dentry->d_parent);
struct attribute * attr = to_attr(filp->f_dentry);
struct module * owner = attr->owner;
struct sysfs_buffer * buffer = filp->private_data;
if (kobj)
kobject_put(kobj);
/* After this point, attr should not be accessed. */
module_put(owner);
if (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, as simply seeking and reading
* again will not get new data, or reset the state of 'poll'.
* 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 (Nether 'poll' or '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 kobject * kobj = to_kobj(filp->f_dentry->d_parent);
struct sysfs_dirent * sd = filp->f_dentry->d_fsdata;
int res = 0;
poll_wait(filp, &kobj->poll, wait);
if (buffer->event != atomic_read(&sd->s_event)) {
res = POLLERR|POLLPRI;
buffer->needs_read_fill = 1;
}
return res;
}
static struct dentry *step_down(struct dentry *dir, const char * name)
{
struct dentry * de;
if (dir == NULL || dir->d_inode == NULL)
return NULL;
mutex_lock(&dir->d_inode->i_mutex);
de = lookup_one_len(name, dir, strlen(name));
mutex_unlock(&dir->d_inode->i_mutex);
dput(dir);
if (IS_ERR(de))
return NULL;
if (de->d_inode == NULL) {
dput(de);
return NULL;
}
return de;
}
void sysfs_notify(struct kobject * k, char *dir, char *attr)
{
struct dentry *de = k->dentry;
if (de)
dget(de);
if (de && dir)
de = step_down(de, dir);
if (de && attr)
de = step_down(de, attr);
if (de) {
struct sysfs_dirent * sd = de->d_fsdata;
if (sd)
atomic_inc(&sd->s_event);
wake_up_interruptible(&k->poll);
dput(de);
}
}
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(struct dentry * dir, const struct attribute * attr, int type)
{
struct sysfs_dirent * parent_sd = dir->d_fsdata;
umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
int error = -EEXIST;
mutex_lock(&dir->d_inode->i_mutex);
if (!sysfs_dirent_exist(parent_sd, attr->name))
error = sysfs_make_dirent(parent_sd, NULL, (void *)attr,
mode, type);
mutex_unlock(&dir->d_inode->i_mutex);
return error;
}
/**
* sysfs_create_file - create an attribute file for an object.
* @kobj: object we're creating for.
* @attr: atrribute descriptor.
*/
int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
{
BUG_ON(!kobj || !kobj->dentry || !attr);
return sysfs_add_file(kobj->dentry, attr, SYSFS_KOBJ_ATTR);
}
/**
* sysfs_update_file - update the modified timestamp on an object attribute.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
*/
int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
{
struct dentry * dir = kobj->dentry;
struct dentry * victim;
int res = -ENOENT;
mutex_lock(&dir->d_inode->i_mutex);
victim = lookup_one_len(attr->name, dir, strlen(attr->name));
if (!IS_ERR(victim)) {
/* make sure dentry is really there */
if (victim->d_inode &&
(victim->d_parent->d_inode == dir->d_inode)) {
victim->d_inode->i_mtime = CURRENT_TIME;
fsnotify_modify(victim);
res = 0;
} else
d_drop(victim);
/**
* Drop the reference acquired from lookup_one_len() above.
*/
dput(victim);
}
mutex_unlock(&dir->d_inode->i_mutex);
return res;
}
/**
* 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 dentry *dir = kobj->dentry;
struct dentry *victim;
struct inode * inode;
struct iattr newattrs;
int res = -ENOENT;
mutex_lock(&dir->d_inode->i_mutex);
victim = lookup_one_len(attr->name, dir, strlen(attr->name));
if (!IS_ERR(victim)) {
if (victim->d_inode &&
(victim->d_parent->d_inode == dir->d_inode)) {
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;
res = notify_change(victim, &newattrs);
mutex_unlock(&inode->i_mutex);
}
dput(victim);
}
mutex_unlock(&dir->d_inode->i_mutex);
return res;
}
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->dentry,attr->name);
}
EXPORT_SYMBOL_GPL(sysfs_create_file);
EXPORT_SYMBOL_GPL(sysfs_remove_file);
EXPORT_SYMBOL_GPL(sysfs_update_file);
