636 lines
16 KiB
C
636 lines
16 KiB
C
/*
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* file.c - operations for regular (text) files.
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*/
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#include <linux/module.h>
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#include <linux/fsnotify.h>
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#include <linux/kobject.h>
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#include <linux/namei.h>
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#include <linux/poll.h>
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#include <linux/list.h>
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#include <asm/uaccess.h>
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#include <asm/semaphore.h>
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#include "sysfs.h"
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#define to_sattr(a) container_of(a,struct subsys_attribute, attr)
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/*
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* Subsystem file operations.
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* These operations allow subsystems to have files that can be
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* read/written.
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*/
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static ssize_t
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subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page)
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{
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struct kset *kset = to_kset(kobj);
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struct subsys_attribute * sattr = to_sattr(attr);
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ssize_t ret = -EIO;
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if (sattr->show)
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ret = sattr->show(kset, page);
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return ret;
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}
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static ssize_t
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subsys_attr_store(struct kobject * kobj, struct attribute * attr,
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const char * page, size_t count)
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{
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struct kset *kset = to_kset(kobj);
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struct subsys_attribute * sattr = to_sattr(attr);
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ssize_t ret = -EIO;
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if (sattr->store)
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ret = sattr->store(kset, page, count);
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return ret;
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}
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static struct sysfs_ops subsys_sysfs_ops = {
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.show = subsys_attr_show,
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.store = subsys_attr_store,
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};
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struct sysfs_buffer {
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size_t count;
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loff_t pos;
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char * page;
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struct sysfs_ops * ops;
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struct semaphore sem;
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int needs_read_fill;
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int event;
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};
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/**
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* fill_read_buffer - allocate and fill buffer from object.
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* @dentry: dentry pointer.
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* @buffer: data buffer for file.
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*
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* Allocate @buffer->page, if it hasn't been already, then call the
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* kobject's show() method to fill the buffer with this attribute's
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* data.
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* This is called only once, on the file's first read unless an error
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* is returned.
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*/
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static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
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{
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struct sysfs_dirent *attr_sd = dentry->d_fsdata;
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struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
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struct sysfs_ops * ops = buffer->ops;
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int ret = 0;
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ssize_t count;
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if (!buffer->page)
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buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
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if (!buffer->page)
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return -ENOMEM;
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/* need attr_sd for attr and ops, its parent for kobj */
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if (!sysfs_get_active_two(attr_sd))
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return -ENODEV;
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buffer->event = atomic_read(&attr_sd->s_event);
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count = ops->show(kobj, attr_sd->s_elem.attr.attr, buffer->page);
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sysfs_put_active_two(attr_sd);
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BUG_ON(count > (ssize_t)PAGE_SIZE);
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if (count >= 0) {
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buffer->needs_read_fill = 0;
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buffer->count = count;
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} else {
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ret = count;
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}
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return ret;
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}
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/**
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* sysfs_read_file - read an attribute.
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* @file: file pointer.
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* @buf: buffer to fill.
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* @count: number of bytes to read.
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* @ppos: starting offset in file.
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*
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* Userspace wants to read an attribute file. The attribute descriptor
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* is in the file's ->d_fsdata. The target object is in the directory's
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* ->d_fsdata.
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*
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* We call fill_read_buffer() to allocate and fill the buffer from the
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* object's show() method exactly once (if the read is happening from
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* the beginning of the file). That should fill the entire buffer with
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* all the data the object has to offer for that attribute.
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* We then call flush_read_buffer() to copy the buffer to userspace
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* in the increments specified.
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*/
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static ssize_t
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sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
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{
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struct sysfs_buffer * buffer = file->private_data;
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ssize_t retval = 0;
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down(&buffer->sem);
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if (buffer->needs_read_fill) {
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retval = fill_read_buffer(file->f_path.dentry,buffer);
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if (retval)
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goto out;
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}
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pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
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__FUNCTION__, count, *ppos, buffer->page);
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retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
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buffer->count);
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out:
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up(&buffer->sem);
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return retval;
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}
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/**
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* fill_write_buffer - copy buffer from userspace.
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* @buffer: data buffer for file.
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* @buf: data from user.
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* @count: number of bytes in @userbuf.
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*
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* Allocate @buffer->page if it hasn't been already, then
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* copy the user-supplied buffer into it.
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*/
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static int
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fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
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{
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int error;
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if (!buffer->page)
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buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
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if (!buffer->page)
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return -ENOMEM;
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if (count >= PAGE_SIZE)
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count = PAGE_SIZE - 1;
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error = copy_from_user(buffer->page,buf,count);
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buffer->needs_read_fill = 1;
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/* if buf is assumed to contain a string, terminate it by \0,
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so e.g. sscanf() can scan the string easily */
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buffer->page[count] = 0;
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return error ? -EFAULT : count;
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}
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/**
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* flush_write_buffer - push buffer to kobject.
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* @dentry: dentry to the attribute
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* @buffer: data buffer for file.
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* @count: number of bytes
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*
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* Get the correct pointers for the kobject and the attribute we're
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* dealing with, then call the store() method for the attribute,
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* passing the buffer that we acquired in fill_write_buffer().
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*/
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static int
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flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
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{
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struct sysfs_dirent *attr_sd = dentry->d_fsdata;
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struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
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struct sysfs_ops * ops = buffer->ops;
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int rc;
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/* need attr_sd for attr and ops, its parent for kobj */
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if (!sysfs_get_active_two(attr_sd))
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return -ENODEV;
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rc = ops->store(kobj, attr_sd->s_elem.attr.attr, buffer->page, count);
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sysfs_put_active_two(attr_sd);
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return rc;
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}
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/**
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* sysfs_write_file - write an attribute.
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* @file: file pointer
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* @buf: data to write
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* @count: number of bytes
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* @ppos: starting offset
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*
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* Similar to sysfs_read_file(), though working in the opposite direction.
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* We allocate and fill the data from the user in fill_write_buffer(),
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* then push it to the kobject in flush_write_buffer().
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* There is no easy way for us to know if userspace is only doing a partial
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* write, so we don't support them. We expect the entire buffer to come
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* on the first write.
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* Hint: if you're writing a value, first read the file, modify only the
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* the value you're changing, then write entire buffer back.
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*/
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static ssize_t
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sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
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{
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struct sysfs_buffer * buffer = file->private_data;
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ssize_t len;
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down(&buffer->sem);
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len = fill_write_buffer(buffer, buf, count);
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if (len > 0)
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len = flush_write_buffer(file->f_path.dentry, buffer, len);
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if (len > 0)
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*ppos += len;
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up(&buffer->sem);
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return len;
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}
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static int sysfs_open_file(struct inode *inode, struct file *file)
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{
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struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
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struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
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struct sysfs_buffer * buffer;
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struct sysfs_ops * ops = NULL;
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int error;
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/* need attr_sd for attr and ops, its parent for kobj */
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if (!sysfs_get_active_two(attr_sd))
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return -ENODEV;
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/* if the kobject has no ktype, then we assume that it is a subsystem
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* itself, and use ops for it.
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*/
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if (kobj->kset && kobj->kset->ktype)
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ops = kobj->kset->ktype->sysfs_ops;
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else if (kobj->ktype)
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ops = kobj->ktype->sysfs_ops;
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else
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ops = &subsys_sysfs_ops;
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error = -EACCES;
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/* No sysfs operations, either from having no subsystem,
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* or the subsystem have no operations.
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*/
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if (!ops)
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goto err_out;
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/* File needs write support.
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* The inode's perms must say it's ok,
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* and we must have a store method.
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*/
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if (file->f_mode & FMODE_WRITE) {
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if (!(inode->i_mode & S_IWUGO) || !ops->store)
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goto err_out;
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}
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/* File needs read support.
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* The inode's perms must say it's ok, and we there
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* must be a show method for it.
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*/
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if (file->f_mode & FMODE_READ) {
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if (!(inode->i_mode & S_IRUGO) || !ops->show)
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goto err_out;
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}
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/* No error? Great, allocate a buffer for the file, and store it
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* it in file->private_data for easy access.
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*/
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error = -ENOMEM;
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buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
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if (!buffer)
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goto err_out;
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init_MUTEX(&buffer->sem);
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buffer->needs_read_fill = 1;
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buffer->ops = ops;
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file->private_data = buffer;
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/* open succeeded, put active references and pin attr_sd */
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sysfs_put_active_two(attr_sd);
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sysfs_get(attr_sd);
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return 0;
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err_out:
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sysfs_put_active_two(attr_sd);
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return error;
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}
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static int sysfs_release(struct inode * inode, struct file * filp)
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{
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struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
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struct sysfs_buffer *buffer = filp->private_data;
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sysfs_put(attr_sd);
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if (buffer) {
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if (buffer->page)
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free_page((unsigned long)buffer->page);
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kfree(buffer);
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}
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return 0;
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}
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/* Sysfs attribute files are pollable. The idea is that you read
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* the content and then you use 'poll' or 'select' to wait for
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* the content to change. When the content changes (assuming the
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* manager for the kobject supports notification), poll will
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* return POLLERR|POLLPRI, and select will return the fd whether
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* it is waiting for read, write, or exceptions.
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* Once poll/select indicates that the value has changed, you
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* need to close and re-open the file, as simply seeking and reading
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* again will not get new data, or reset the state of 'poll'.
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* Reminder: this only works for attributes which actively support
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* it, and it is not possible to test an attribute from userspace
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* to see if it supports poll (Nether 'poll' or 'select' return
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* an appropriate error code). When in doubt, set a suitable timeout value.
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*/
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static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
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{
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struct sysfs_buffer * buffer = filp->private_data;
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struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
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struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
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/* need parent for the kobj, grab both */
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if (!sysfs_get_active_two(attr_sd))
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goto trigger;
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poll_wait(filp, &kobj->poll, wait);
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sysfs_put_active_two(attr_sd);
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if (buffer->event != atomic_read(&attr_sd->s_event))
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goto trigger;
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return 0;
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trigger:
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buffer->needs_read_fill = 1;
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return POLLERR|POLLPRI;
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}
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void sysfs_notify(struct kobject *k, char *dir, char *attr)
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{
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struct sysfs_dirent *sd = k->sd;
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mutex_lock(&sysfs_mutex);
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if (sd && dir)
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sd = sysfs_find_dirent(sd, dir);
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if (sd && attr)
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sd = sysfs_find_dirent(sd, attr);
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if (sd) {
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atomic_inc(&sd->s_event);
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wake_up_interruptible(&k->poll);
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}
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mutex_unlock(&sysfs_mutex);
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}
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EXPORT_SYMBOL_GPL(sysfs_notify);
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const struct file_operations sysfs_file_operations = {
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.read = sysfs_read_file,
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.write = sysfs_write_file,
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.llseek = generic_file_llseek,
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.open = sysfs_open_file,
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.release = sysfs_release,
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.poll = sysfs_poll,
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};
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int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
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int type)
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{
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umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
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struct sysfs_addrm_cxt acxt;
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struct sysfs_dirent *sd;
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sd = sysfs_new_dirent(attr->name, mode, type);
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if (!sd)
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return -ENOMEM;
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sd->s_elem.attr.attr = (void *)attr;
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sysfs_addrm_start(&acxt, dir_sd);
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if (!sysfs_find_dirent(dir_sd, attr->name)) {
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sysfs_add_one(&acxt, sd);
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sysfs_link_sibling(sd);
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}
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if (!sysfs_addrm_finish(&acxt)) {
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sysfs_put(sd);
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return -EEXIST;
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}
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return 0;
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}
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/**
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* sysfs_create_file - create an attribute file for an object.
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* @kobj: object we're creating for.
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* @attr: atrribute descriptor.
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*/
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int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
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{
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BUG_ON(!kobj || !kobj->sd || !attr);
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return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
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}
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/**
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* sysfs_add_file_to_group - add an attribute file to a pre-existing group.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @group: group name.
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*/
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int sysfs_add_file_to_group(struct kobject *kobj,
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const struct attribute *attr, const char *group)
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{
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struct sysfs_dirent *dir_sd;
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int error;
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dir_sd = sysfs_get_dirent(kobj->sd, group);
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if (!dir_sd)
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return -ENOENT;
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error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
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sysfs_put(dir_sd);
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return error;
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}
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EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
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/**
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* sysfs_update_file - update the modified timestamp on an object attribute.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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*/
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int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
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{
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struct sysfs_dirent *victim_sd = NULL;
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struct dentry *victim = NULL;
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int rc;
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rc = -ENOENT;
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victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
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if (!victim_sd)
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goto out;
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victim = sysfs_get_dentry(victim_sd);
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if (IS_ERR(victim)) {
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rc = PTR_ERR(victim);
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victim = NULL;
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goto out;
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}
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mutex_lock(&victim->d_inode->i_mutex);
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victim->d_inode->i_mtime = CURRENT_TIME;
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fsnotify_modify(victim);
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mutex_unlock(&victim->d_inode->i_mutex);
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rc = 0;
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out:
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dput(victim);
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sysfs_put(victim_sd);
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return rc;
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}
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/**
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* sysfs_chmod_file - update the modified mode value on an object attribute.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @mode: file permissions.
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*
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*/
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int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
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{
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struct sysfs_dirent *victim_sd = NULL;
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struct dentry *victim = NULL;
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struct inode * inode;
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struct iattr newattrs;
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int rc;
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rc = -ENOENT;
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victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
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if (!victim_sd)
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goto out;
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victim = sysfs_get_dentry(victim_sd);
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if (IS_ERR(victim)) {
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rc = PTR_ERR(victim);
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victim = NULL;
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goto out;
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}
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inode = victim->d_inode;
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mutex_lock(&inode->i_mutex);
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newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
|
|
newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
|
|
rc = notify_change(victim, &newattrs);
|
|
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;
|
|
|
|
dir_sd = sysfs_get_dirent(kobj->sd, group);
|
|
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);
|
|
EXPORT_SYMBOL_GPL(sysfs_update_file);
|