summaryrefslogtreecommitdiffstats
path: root/fs/configfs/file.c
blob: d98be5e013280e7708e825d4b458acc3219c5a62 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
/* -*- 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 <asm/uaccess.h>
#include <asm/semaphore.h>

#include <linux/configfs.h>
#include "configfs_internal.h"


struct configfs_buffer {
	size_t			count;
	loff_t			pos;
	char			* page;
	struct configfs_item_operations	* ops;
	struct semaphore	sem;
	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)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.
 *	@userbuf:	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 configfs_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;
}

/**
 *	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;

	down(&buffer->sem);
	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 = 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 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 >= 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 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;

	down(&buffer->sem);
	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;
	up(&buffer->sem);
	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;
	}
	init_MUTEX(&buffer->sem);
	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);
		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(&dir->d_inode->i_mutex);
	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);
}

OpenPOWER on IntegriCloud