/**
* sysfs_get_active_two - get active references to sysfs_dirent and parent
* @sd: sysfs_dirent of interest
*
* Get active reference to @sd and its parent. Parent's active
* reference is grabbed first. This function is noop if @sd is
* NULL.
*
* RETURNS:
* Pointer to @sd on success, NULL on failure.
*/
struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd)
{
if (sd) {
if (sd->s_parent && unlikely(!sysfs_get_active(sd->s_parent)))
return NULL;
if (unlikely(!sysfs_get_active(sd))) {
sysfs_put_active(sd->s_parent);
return NULL;
}
}
return sd;
}
/**
* flush_write_buffer - push buffer to kobject
* @of: open file
* @buf: data buffer for file
* @off: file offset to write to
* @count: number of bytes
*
* Get the correct pointers for the kobject and the attribute we're dealing
* with, then call the store() method for it with @buf.
*/
static int flush_write_buffer(struct sysfs_open_file *of, char *buf, loff_t off,
size_t count)
{
struct kobject *kobj = of->sd->s_parent->s_dir.kobj;
int rc = 0;
/*
* Need @of->sd for attr and ops, its parent for kobj. @of->mutex
* nests outside active ref and is just to ensure that the ops
* aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd)) {
mutex_unlock(&of->mutex);
return -ENODEV;
}
if (sysfs_is_bin(of->sd)) {
struct bin_attribute *battr = of->sd->s_attr.bin_attr;
rc = -EIO;
if (battr->write)
rc = battr->write(of->file, kobj, battr, buf, off,
count);
} else {
const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
rc = ops->store(kobj, of->sd->s_attr.attr, buf, count);
}
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
return rc;
}
/*
* Reads on sysfs are handled through seq_file, which takes care of hairy
* details like buffering and seeking. The following function pipes
* sysfs_ops->show() result through seq_file.
*/
static int sysfs_seq_show(struct seq_file *sf, void *v)
{
struct sysfs_open_file *of = sf->private;
struct kobject *kobj = of->sd->s_parent->s_dir.kobj;
const struct sysfs_ops *ops;
char *buf;
ssize_t count;
/* acquire buffer and ensure that it's >= PAGE_SIZE */
count = seq_get_buf(sf, &buf);
if (count < PAGE_SIZE) {
seq_commit(sf, -1);
return 0;
}
/*
* Need @of->sd for attr and ops, its parent for kobj. @of->mutex
* nests outside active ref and is just to ensure that the ops
* aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd)) {
mutex_unlock(&of->mutex);
return -ENODEV;
}
of->event = atomic_read(&of->sd->s_attr.open->event);
/*
* Lookup @ops and invoke show(). Control may reach here via seq
* file lseek even if @ops->show() isn't implemented.
*/
ops = sysfs_file_ops(of->sd);
if (ops->show)
count = ops->show(kobj, of->sd->s_attr.attr, buf);
else
count = 0;
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
if (count < 0)
return count;
/*
* 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;
}
seq_commit(sf, count);
return 0;
}
/*
* Read method for bin files. As reading a bin file can have side-effects,
* the exact offset and bytes specified in read(2) call should be passed to
* the read callback making it difficult to use seq_file. Implement
* simplistic custom buffering for bin files.
*/
static ssize_t sysfs_bin_read(struct file *file, char __user *userbuf,
size_t bytes, loff_t *off)
{
struct sysfs_open_file *of = sysfs_of(file);
struct bin_attribute *battr = of->sd->s_attr.bin_attr;
struct kobject *kobj = of->sd->s_parent->s_dir.kobj;
loff_t size = file_inode(file)->i_size;
int count = min_t(size_t, bytes, PAGE_SIZE);
loff_t offs = *off;
char *buf;
if (!bytes)
return 0;
if (size) {
if (offs > size)
return 0;
if (offs + count > size)
count = size - offs;
}
buf = kmalloc(count, GFP_KERNEL);
if (!buf)
return -ENOMEM;
/* need of->sd for battr, its parent for kobj */
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd)) {
count = -ENODEV;
mutex_unlock(&of->mutex);
goto out_free;
}
if (battr->read)
count = battr->read(file, kobj, battr, buf, offs, count);
else
count = -EIO;
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
if (count < 0)
goto out_free;
if (copy_to_user(userbuf, buf, count)) {
count = -EFAULT;
goto out_free;
}
pr_debug("offs = %lld, *off = %lld, count = %d\n", offs, *off, count);
*off = offs + count;
out_free:
kfree(buf);
return count;
}
static void sysfs_bin_vma_open(struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
struct sysfs_open_file *of = sysfs_of(file);
if (!of->vm_ops)
return;
if (!sysfs_get_active(of->sd))
return;
if (of->vm_ops->open)
of->vm_ops->open(vma);
sysfs_put_active(of->sd);
}
static void bin_vma_close(struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
struct bin_buffer *bb = file->private_data;
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
if (!bb->vm_ops || !bb->vm_ops->close)
return;
if (!sysfs_get_active(attr_sd))
return;
bb->vm_ops->close(vma);
sysfs_put_active(attr_sd);
}
static int bin_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct file *file = vma->vm_file;
struct bin_buffer *bb = file->private_data;
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
int ret;
if (!bb->vm_ops || !bb->vm_ops->fault)
return VM_FAULT_SIGBUS;
if (!sysfs_get_active(attr_sd))
return VM_FAULT_SIGBUS;
ret = bb->vm_ops->fault(vma, vmf);
sysfs_put_active(attr_sd);
return ret;
}
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;
const struct sysfs_ops * ops = buffer->ops;
int rc;
/* need attr_sd for attr and ops, its parent for kobj */
if (!sysfs_get_active(attr_sd))
return -ENODEV;
rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);
sysfs_put_active(attr_sd);
return rc;
}
static int bin_access(struct vm_area_struct *vma, unsigned long addr,
void *buf, int len, int write)
{
struct file *file = vma->vm_file;
struct bin_buffer *bb = file->private_data;
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
int ret;
if (!bb->vm_ops || !bb->vm_ops->access)
return -EINVAL;
if (!sysfs_get_active(attr_sd))
return -EINVAL;
ret = bb->vm_ops->access(vma, addr, buf, len, write);
sysfs_put_active(attr_sd);
return ret;
}
static int sysfs_bin_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct file *file = vma->vm_file;
struct sysfs_open_file *of = sysfs_of(file);
int ret;
if (!of->vm_ops)
return VM_FAULT_SIGBUS;
if (!sysfs_get_active(of->sd))
return VM_FAULT_SIGBUS;
ret = VM_FAULT_SIGBUS;
if (of->vm_ops->fault)
ret = of->vm_ops->fault(vma, vmf);
sysfs_put_active(of->sd);
return ret;
}
static int
fill_read(struct file *file, char *buffer, loff_t off, size_t count)
{
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
struct bin_attribute *attr = attr_sd->s_bin_attr.bin_attr;
struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
int rc;
/* need attr_sd for attr, its parent for kobj */
if (!sysfs_get_active(attr_sd))
return -ENODEV;
rc = -EIO;
if (attr->read)
rc = attr->read(file, kobj, attr, buffer, off, count);
sysfs_put_active(attr_sd);
return rc;
}
static int sysfs_bin_access(struct vm_area_struct *vma, unsigned long addr,
void *buf, int len, int write)
{
struct file *file = vma->vm_file;
struct sysfs_open_file *of = sysfs_of(file);
int ret;
if (!of->vm_ops)
return -EINVAL;
if (!sysfs_get_active(of->sd))
return -EINVAL;
ret = -EINVAL;
if (of->vm_ops->access)
ret = of->vm_ops->access(vma, addr, buf, len, write);
sysfs_put_active(of->sd);
return ret;
}
/**
* 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;
const 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(attr_sd))
return -ENODEV;
buffer->event = atomic_read_unchecked(&attr_sd->s_attr.open->event);
count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
sysfs_put_active(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;
}
static int bin_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct file *file = vma->vm_file;
struct bin_buffer *bb = file->private_data;
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
int ret;
if (!bb->vm_ops)
return VM_FAULT_SIGBUS;
if (!sysfs_get_active(attr_sd))
return VM_FAULT_SIGBUS;
ret = 0;
if (bb->vm_ops->page_mkwrite)
ret = bb->vm_ops->page_mkwrite(vma, vmf);
else
file_update_time(file);
sysfs_put_active(attr_sd);
return ret;
}
static int sysfs_bin_page_mkwrite(struct vm_area_struct *vma,
struct vm_fault *vmf)
{
struct file *file = vma->vm_file;
struct sysfs_open_file *of = sysfs_of(file);
int ret;
if (!of->vm_ops)
return VM_FAULT_SIGBUS;
if (!sysfs_get_active(of->sd))
return VM_FAULT_SIGBUS;
ret = 0;
if (of->vm_ops->page_mkwrite)
ret = of->vm_ops->page_mkwrite(vma, vmf);
else
file_update_time(file);
sysfs_put_active(of->sd);
return ret;
}
/* 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(attr_sd))
goto trigger;
poll_wait(filp, &od->poll, wait);
sysfs_put_active(attr_sd);
if (buffer->event != atomic_read_unchecked(&od->event))
goto trigger;
return DEFAULT_POLLMASK;
trigger:
buffer->needs_read_fill = 1;
return DEFAULT_POLLMASK|POLLERR|POLLPRI;
}
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;
const struct sysfs_ops *ops;
int error = -EACCES;
/* need attr_sd for attr and ops, its parent for kobj */
if (!sysfs_get_active(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(attr_sd);
return 0;
err_free:
kfree(buffer);
err_out:
sysfs_put_active(attr_sd);
return error;
}