1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* -*- mode: c; c-basic-offset: 8; -*-
3 * vim: noexpandtab sw=8 ts=8 sts=0:
5 * file.c - operations for regular (text) files.
8 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
10 * configfs Copyright (C) 2005 Oracle. All rights reserved.
14 #include <linux/module.h>
15 #include <linux/slab.h>
16 #include <linux/mutex.h>
17 #include <linux/vmalloc.h>
18 #include <linux/uaccess.h>
20 #include <linux/configfs.h>
21 #include "configfs_internal.h"
24 * A simple attribute can only be 4096 characters. Why 4k? Because the
25 * original code limited it to PAGE_SIZE. That's a bad idea, though,
26 * because an attribute of 16k on ia64 won't work on x86. So we limit to
27 * 4k, our minimum common page size.
29 #define SIMPLE_ATTR_SIZE 4096
31 struct configfs_buffer
{
35 struct configfs_item_operations
* ops
;
38 bool read_in_progress
;
39 bool write_in_progress
;
46 * fill_read_buffer - allocate and fill buffer from item.
47 * @dentry: dentry pointer.
48 * @buffer: data buffer for file.
50 * Allocate @buffer->page, if it hasn't been already, then call the
51 * config_item's show() method to fill the buffer with this attribute's
53 * This is called only once, on the file's first read.
55 static int fill_read_buffer(struct dentry
* dentry
, struct configfs_buffer
* buffer
)
57 struct configfs_attribute
* attr
= to_attr(dentry
);
58 struct config_item
* item
= to_item(dentry
->d_parent
);
63 buffer
->page
= (char *) get_zeroed_page(GFP_KERNEL
);
67 count
= attr
->show(item
, buffer
->page
);
69 BUG_ON(count
> (ssize_t
)SIMPLE_ATTR_SIZE
);
71 buffer
->needs_read_fill
= 0;
72 buffer
->count
= count
;
79 * configfs_read_file - read an attribute.
80 * @file: file pointer.
81 * @buf: buffer to fill.
82 * @count: number of bytes to read.
83 * @ppos: starting offset in file.
85 * Userspace wants to read an attribute file. The attribute descriptor
86 * is in the file's ->d_fsdata. The target item is in the directory's
89 * We call fill_read_buffer() to allocate and fill the buffer from the
90 * item's show() method exactly once (if the read is happening from
91 * the beginning of the file). That should fill the entire buffer with
92 * all the data the item has to offer for that attribute.
93 * We then call flush_read_buffer() to copy the buffer to userspace
94 * in the increments specified.
98 configfs_read_file(struct file
*file
, char __user
*buf
, size_t count
, loff_t
*ppos
)
100 struct configfs_buffer
* buffer
= file
->private_data
;
103 mutex_lock(&buffer
->mutex
);
104 if (buffer
->needs_read_fill
) {
105 if ((retval
= fill_read_buffer(file
->f_path
.dentry
,buffer
)))
108 pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
109 __func__
, count
, *ppos
, buffer
->page
);
110 retval
= simple_read_from_buffer(buf
, count
, ppos
, buffer
->page
,
113 mutex_unlock(&buffer
->mutex
);
118 * configfs_read_bin_file - read a binary attribute.
119 * @file: file pointer.
120 * @buf: buffer to fill.
121 * @count: number of bytes to read.
122 * @ppos: starting offset in file.
124 * Userspace wants to read a binary attribute file. The attribute
125 * descriptor is in the file's ->d_fsdata. The target item is in the
126 * directory's ->d_fsdata.
128 * We check whether we need to refill the buffer. If so we will
129 * call the attributes' attr->read() twice. The first time we
130 * will pass a NULL as a buffer pointer, which the attributes' method
131 * will use to return the size of the buffer required. If no error
132 * occurs we will allocate the buffer using vmalloc and call
133 * attr->read() again passing that buffer as an argument.
134 * Then we just copy to user-space using simple_read_from_buffer.
138 configfs_read_bin_file(struct file
*file
, char __user
*buf
,
139 size_t count
, loff_t
*ppos
)
141 struct configfs_buffer
*buffer
= file
->private_data
;
142 struct dentry
*dentry
= file
->f_path
.dentry
;
143 struct config_item
*item
= to_item(dentry
->d_parent
);
144 struct configfs_bin_attribute
*bin_attr
= to_bin_attr(dentry
);
146 ssize_t len
= min_t(size_t, count
, PAGE_SIZE
);
148 mutex_lock(&buffer
->mutex
);
150 /* we don't support switching read/write modes */
151 if (buffer
->write_in_progress
) {
155 buffer
->read_in_progress
= true;
157 if (buffer
->needs_read_fill
) {
158 /* perform first read with buf == NULL to get extent */
159 len
= bin_attr
->read(item
, NULL
, 0);
165 /* do not exceed the maximum value */
166 if (bin_attr
->cb_max_size
&& len
> bin_attr
->cb_max_size
) {
171 buffer
->bin_buffer
= vmalloc(len
);
172 if (buffer
->bin_buffer
== NULL
) {
176 buffer
->bin_buffer_size
= len
;
178 /* perform second read to fill buffer */
179 len
= bin_attr
->read(item
, buffer
->bin_buffer
, len
);
182 vfree(buffer
->bin_buffer
);
183 buffer
->bin_buffer_size
= 0;
184 buffer
->bin_buffer
= NULL
;
188 buffer
->needs_read_fill
= 0;
191 retval
= simple_read_from_buffer(buf
, count
, ppos
, buffer
->bin_buffer
,
192 buffer
->bin_buffer_size
);
194 mutex_unlock(&buffer
->mutex
);
200 * fill_write_buffer - copy buffer from userspace.
201 * @buffer: data buffer for file.
202 * @buf: data from user.
203 * @count: number of bytes in @userbuf.
205 * Allocate @buffer->page if it hasn't been already, then
206 * copy the user-supplied buffer into it.
210 fill_write_buffer(struct configfs_buffer
* buffer
, const char __user
* buf
, size_t count
)
215 buffer
->page
= (char *)__get_free_pages(GFP_KERNEL
, 0);
219 if (count
>= SIMPLE_ATTR_SIZE
)
220 count
= SIMPLE_ATTR_SIZE
- 1;
221 error
= copy_from_user(buffer
->page
,buf
,count
);
222 buffer
->needs_read_fill
= 1;
223 /* if buf is assumed to contain a string, terminate it by \0,
224 * so e.g. sscanf() can scan the string easily */
225 buffer
->page
[count
] = 0;
226 return error
? -EFAULT
: count
;
231 * flush_write_buffer - push buffer to config_item.
232 * @dentry: dentry to the attribute
233 * @buffer: data buffer for file.
234 * @count: number of bytes
236 * Get the correct pointers for the config_item and the attribute we're
237 * dealing with, then call the store() method for the attribute,
238 * passing the buffer that we acquired in fill_write_buffer().
242 flush_write_buffer(struct dentry
* dentry
, struct configfs_buffer
* buffer
, size_t count
)
244 struct configfs_attribute
* attr
= to_attr(dentry
);
245 struct config_item
* item
= to_item(dentry
->d_parent
);
247 return attr
->store(item
, buffer
->page
, count
);
252 * configfs_write_file - write an attribute.
253 * @file: file pointer
254 * @buf: data to write
255 * @count: number of bytes
256 * @ppos: starting offset
258 * Similar to configfs_read_file(), though working in the opposite direction.
259 * We allocate and fill the data from the user in fill_write_buffer(),
260 * then push it to the config_item in flush_write_buffer().
261 * There is no easy way for us to know if userspace is only doing a partial
262 * write, so we don't support them. We expect the entire buffer to come
263 * on the first write.
264 * Hint: if you're writing a value, first read the file, modify only the
265 * the value you're changing, then write entire buffer back.
269 configfs_write_file(struct file
*file
, const char __user
*buf
, size_t count
, loff_t
*ppos
)
271 struct configfs_buffer
* buffer
= file
->private_data
;
274 mutex_lock(&buffer
->mutex
);
275 len
= fill_write_buffer(buffer
, buf
, count
);
277 len
= flush_write_buffer(file
->f_path
.dentry
, buffer
, len
);
280 mutex_unlock(&buffer
->mutex
);
285 * configfs_write_bin_file - write a binary attribute.
286 * @file: file pointer
287 * @buf: data to write
288 * @count: number of bytes
289 * @ppos: starting offset
291 * Writing to a binary attribute file is similar to a normal read.
292 * We buffer the consecutive writes (binary attribute files do not
293 * support lseek) in a continuously growing buffer, but we don't
294 * commit until the close of the file.
298 configfs_write_bin_file(struct file
*file
, const char __user
*buf
,
299 size_t count
, loff_t
*ppos
)
301 struct configfs_buffer
*buffer
= file
->private_data
;
302 struct dentry
*dentry
= file
->f_path
.dentry
;
303 struct configfs_bin_attribute
*bin_attr
= to_bin_attr(dentry
);
307 mutex_lock(&buffer
->mutex
);
309 /* we don't support switching read/write modes */
310 if (buffer
->read_in_progress
) {
314 buffer
->write_in_progress
= true;
317 if (*ppos
+ count
> buffer
->bin_buffer_size
) {
319 if (bin_attr
->cb_max_size
&&
320 *ppos
+ count
> bin_attr
->cb_max_size
) {
325 tbuf
= vmalloc(*ppos
+ count
);
331 /* copy old contents */
332 if (buffer
->bin_buffer
) {
333 memcpy(tbuf
, buffer
->bin_buffer
,
334 buffer
->bin_buffer_size
);
335 vfree(buffer
->bin_buffer
);
338 /* clear the new area */
339 memset(tbuf
+ buffer
->bin_buffer_size
, 0,
340 *ppos
+ count
- buffer
->bin_buffer_size
);
341 buffer
->bin_buffer
= tbuf
;
342 buffer
->bin_buffer_size
= *ppos
+ count
;
345 len
= simple_write_to_buffer(buffer
->bin_buffer
,
346 buffer
->bin_buffer_size
, ppos
, buf
, count
);
348 mutex_unlock(&buffer
->mutex
);
352 static int check_perm(struct inode
* inode
, struct file
* file
, int type
)
354 struct config_item
*item
= configfs_get_config_item(file
->f_path
.dentry
->d_parent
);
355 struct configfs_attribute
* attr
= to_attr(file
->f_path
.dentry
);
356 struct configfs_bin_attribute
*bin_attr
= NULL
;
357 struct configfs_buffer
* buffer
;
358 struct configfs_item_operations
* ops
= NULL
;
364 if (type
& CONFIGFS_ITEM_BIN_ATTR
)
365 bin_attr
= to_bin_attr(file
->f_path
.dentry
);
367 /* Grab the module reference for this attribute if we have one */
368 if (!try_module_get(attr
->ca_owner
)) {
374 ops
= item
->ci_type
->ct_item_ops
;
378 /* File needs write support.
379 * The inode's perms must say it's ok,
380 * and we must have a store method.
382 if (file
->f_mode
& FMODE_WRITE
) {
383 if (!(inode
->i_mode
& S_IWUGO
))
386 if ((type
& CONFIGFS_ITEM_ATTR
) && !attr
->store
)
389 if ((type
& CONFIGFS_ITEM_BIN_ATTR
) && !bin_attr
->write
)
393 /* File needs read support.
394 * The inode's perms must say it's ok, and we there
395 * must be a show method for it.
397 if (file
->f_mode
& FMODE_READ
) {
398 if (!(inode
->i_mode
& S_IRUGO
))
401 if ((type
& CONFIGFS_ITEM_ATTR
) && !attr
->show
)
404 if ((type
& CONFIGFS_ITEM_BIN_ATTR
) && !bin_attr
->read
)
408 /* No error? Great, allocate a buffer for the file, and store it
409 * it in file->private_data for easy access.
411 buffer
= kzalloc(sizeof(struct configfs_buffer
),GFP_KERNEL
);
416 mutex_init(&buffer
->mutex
);
417 buffer
->needs_read_fill
= 1;
418 buffer
->read_in_progress
= false;
419 buffer
->write_in_progress
= false;
421 file
->private_data
= buffer
;
430 module_put(attr
->ca_owner
);
433 config_item_put(item
);
437 static int configfs_release(struct inode
*inode
, struct file
*filp
)
439 struct config_item
* item
= to_item(filp
->f_path
.dentry
->d_parent
);
440 struct configfs_attribute
* attr
= to_attr(filp
->f_path
.dentry
);
441 struct module
* owner
= attr
->ca_owner
;
442 struct configfs_buffer
* buffer
= filp
->private_data
;
445 config_item_put(item
);
446 /* After this point, attr should not be accessed. */
451 free_page((unsigned long)buffer
->page
);
452 mutex_destroy(&buffer
->mutex
);
458 static int configfs_open_file(struct inode
*inode
, struct file
*filp
)
460 return check_perm(inode
, filp
, CONFIGFS_ITEM_ATTR
);
463 static int configfs_open_bin_file(struct inode
*inode
, struct file
*filp
)
465 return check_perm(inode
, filp
, CONFIGFS_ITEM_BIN_ATTR
);
468 static int configfs_release_bin_file(struct inode
*inode
, struct file
*filp
)
470 struct configfs_buffer
*buffer
= filp
->private_data
;
471 struct dentry
*dentry
= filp
->f_path
.dentry
;
472 struct config_item
*item
= to_item(dentry
->d_parent
);
473 struct configfs_bin_attribute
*bin_attr
= to_bin_attr(dentry
);
477 buffer
->read_in_progress
= false;
479 if (buffer
->write_in_progress
) {
480 buffer
->write_in_progress
= false;
482 len
= bin_attr
->write(item
, buffer
->bin_buffer
,
483 buffer
->bin_buffer_size
);
485 /* vfree on NULL is safe */
486 vfree(buffer
->bin_buffer
);
487 buffer
->bin_buffer
= NULL
;
488 buffer
->bin_buffer_size
= 0;
489 buffer
->needs_read_fill
= 1;
492 ret
= configfs_release(inode
, filp
);
499 const struct file_operations configfs_file_operations
= {
500 .read
= configfs_read_file
,
501 .write
= configfs_write_file
,
502 .llseek
= generic_file_llseek
,
503 .open
= configfs_open_file
,
504 .release
= configfs_release
,
507 const struct file_operations configfs_bin_file_operations
= {
508 .read
= configfs_read_bin_file
,
509 .write
= configfs_write_bin_file
,
510 .llseek
= NULL
, /* bin file is not seekable */
511 .open
= configfs_open_bin_file
,
512 .release
= configfs_release_bin_file
,
516 * configfs_create_file - create an attribute file for an item.
517 * @item: item we're creating for.
518 * @attr: atrribute descriptor.
521 int configfs_create_file(struct config_item
* item
, const struct configfs_attribute
* attr
)
523 struct dentry
*dir
= item
->ci_dentry
;
524 struct configfs_dirent
*parent_sd
= dir
->d_fsdata
;
525 umode_t mode
= (attr
->ca_mode
& S_IALLUGO
) | S_IFREG
;
528 inode_lock_nested(d_inode(dir
), I_MUTEX_NORMAL
);
529 error
= configfs_make_dirent(parent_sd
, NULL
, (void *) attr
, mode
,
531 inode_unlock(d_inode(dir
));
537 * configfs_create_bin_file - create a binary attribute file for an item.
538 * @item: item we're creating for.
539 * @attr: atrribute descriptor.
542 int configfs_create_bin_file(struct config_item
*item
,
543 const struct configfs_bin_attribute
*bin_attr
)
545 struct dentry
*dir
= item
->ci_dentry
;
546 struct configfs_dirent
*parent_sd
= dir
->d_fsdata
;
547 umode_t mode
= (bin_attr
->cb_attr
.ca_mode
& S_IALLUGO
) | S_IFREG
;
550 inode_lock_nested(dir
->d_inode
, I_MUTEX_NORMAL
);
551 error
= configfs_make_dirent(parent_sd
, NULL
, (void *) bin_attr
, mode
,
552 CONFIGFS_ITEM_BIN_ATTR
);
553 inode_unlock(dir
->d_inode
);