/* -*- mode: c; c-basic-offset: 8; -*- * vim: noexpandtab sw=8 ts=8 sts=0: * * file.c - operations for regular (text) files. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public * License along with this program; if not, write to the * Free Software Foundation, Inc., 59 Temple Place - Suite 330, * Boston, MA 021110-1307, USA. * * Based on sysfs: * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel * * configfs Copyright (C) 2005 Oracle. All rights reserved. */ #include <linux/fs.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/mutex.h> #include <asm/uaccess.h> #include <linux/configfs.h> #include "configfs_internal.h" /* * A simple attribute can only be 4096 characters. Why 4k? Because the * original code limited it to PAGE_SIZE. That's a bad idea, though, * because an attribute of 16k on ia64 won't work on x86. So we limit to * 4k, our minimum common page size. */ #define SIMPLE_ATTR_SIZE 4096 struct configfs_buffer { size_t count; loff_t pos; char * page; struct configfs_item_operations * ops; struct mutex mutex; int needs_read_fill; }; /** * fill_read_buffer - allocate and fill buffer from item. * @dentry: dentry pointer. * @buffer: data buffer for file. * * Allocate @buffer->page, if it hasn't been already, then call the * config_item'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 configfs_buffer * buffer) { struct configfs_attribute * attr = to_attr(dentry); struct config_item * item = to_item(dentry->d_parent); struct configfs_item_operations * 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; count = ops->show_attribute(item,attr,buffer->page); buffer->needs_read_fill = 0; BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE); if (count >= 0) buffer->count = count; else ret = count; return ret; } /** * configfs_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 item is in the directory's * ->d_fsdata. * * We call fill_read_buffer() to allocate and fill the buffer from the * item'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 item 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 configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct configfs_buffer * buffer = file->private_data; ssize_t retval = 0; mutex_lock(&buffer->mutex); if (buffer->needs_read_fill) { if ((retval = fill_read_buffer(file->f_path.dentry,buffer))) goto out; } pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n", __FUNCTION__, 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 configfs_buffer * buffer, const char __user * buf, size_t count) { int error; if (!buffer->page) buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0); if (!buffer->page) return -ENOMEM; if (count >= SIMPLE_ATTR_SIZE) count = SIMPLE_ATTR_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 config_item. * @dentry: dentry to the attribute * @buffer: data buffer for file. * @count: number of bytes * * Get the correct pointers for the config_item 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 configfs_buffer * buffer, size_t count) { struct configfs_attribute * attr = to_attr(dentry); struct config_item * item = to_item(dentry->d_parent); struct configfs_item_operations * ops = buffer->ops; return ops->store_attribute(item,attr,buffer->page,count); } /** * configfs_write_file - write an attribute. * @file: file pointer * @buf: data to write * @count: number of bytes * @ppos: starting offset * * Similar to configfs_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 config_item 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 configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { struct configfs_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, count); if (len > 0) *ppos += len; mutex_unlock(&buffer->mutex); return len; } static int check_perm(struct inode * inode, struct file * file) { struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent); struct configfs_attribute * attr = to_attr(file->f_path.dentry); struct configfs_buffer * buffer; struct configfs_item_operations * ops = NULL; int error = 0; if (!item || !attr) goto Einval; /* Grab the module reference for this attribute if we have one */ if (!try_module_get(attr->ca_owner)) { error = -ENODEV; goto Done; } if (item->ci_type) ops = item->ci_type->ct_item_ops; else 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_attribute) 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_attribute) 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 configfs_buffer),GFP_KERNEL); if (!buffer) { error = -ENOMEM; goto Enomem; } mutex_init(&buffer->mutex); buffer->needs_read_fill = 1; buffer->ops = ops; file->private_data = buffer; goto Done; Einval: error = -EINVAL; goto Done; Eaccess: error = -EACCES; Enomem: module_put(attr->ca_owner); Done: if (error && item) config_item_put(item); return error; } static int configfs_open_file(struct inode * inode, struct file * filp) { return check_perm(inode,filp); } static int configfs_release(struct inode * inode, struct file * filp) { struct config_item * item = to_item(filp->f_path.dentry->d_parent); struct configfs_attribute * attr = to_attr(filp->f_path.dentry); struct module * owner = attr->ca_owner; struct configfs_buffer * buffer = filp->private_data; if (item) config_item_put(item); /* After this point, attr should not be accessed. */ module_put(owner); if (buffer) { if (buffer->page) free_page((unsigned long)buffer->page); mutex_destroy(&buffer->mutex); kfree(buffer); } return 0; } const struct file_operations configfs_file_operations = { .read = configfs_read_file, .write = configfs_write_file, .llseek = generic_file_llseek, .open = configfs_open_file, .release = configfs_release, }; int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type) { struct configfs_dirent * parent_sd = dir->d_fsdata; umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG; int error = 0; mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_NORMAL); error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type); mutex_unlock(&dir->d_inode->i_mutex); return error; } /** * configfs_create_file - create an attribute file for an item. * @item: item we're creating for. * @attr: atrribute descriptor. */ int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr) { BUG_ON(!item || !item->ci_dentry || !attr); return configfs_add_file(item->ci_dentry, attr, CONFIGFS_ITEM_ATTR); }