1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * file.c - operations for regular (text) files.
6 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
8 * configfs Copyright (C) 2005 Oracle. All rights reserved.
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/mutex.h>
15 #include <linux/vmalloc.h>
16 #include <linux/uaccess.h>
17 #include <linux/uio.h>
18 #include <linux/configfs.h>
19 #include "configfs_internal.h"
22 * A simple attribute can only be 4096 characters. Why 4k? Because the
23 * original code limited it to PAGE_SIZE. That's a bad idea, though,
24 * because an attribute of 16k on ia64 won't work on x86. So we limit to
25 * 4k, our minimum common page size.
27 #define SIMPLE_ATTR_SIZE 4096
29 struct configfs_buffer {
33 struct configfs_item_operations * ops;
36 bool read_in_progress;
37 bool write_in_progress;
41 struct config_item *item;
44 struct configfs_attribute *attr;
45 struct configfs_bin_attribute *bin_attr;
49 static inline struct configfs_fragment *to_frag(struct file *file)
51 struct configfs_dirent *sd = file->f_path.dentry->d_fsdata;
56 static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)
58 struct configfs_fragment *frag = to_frag(file);
59 ssize_t count = -ENOENT;
62 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
66 down_read(&frag->frag_sem);
68 count = buffer->attr->show(buffer->item, buffer->page);
69 up_read(&frag->frag_sem);
73 if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
75 buffer->needs_read_fill = 0;
76 buffer->count = count;
80 static ssize_t configfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
82 struct file *file = iocb->ki_filp;
83 struct configfs_buffer *buffer = file->private_data;
86 mutex_lock(&buffer->mutex);
87 if (buffer->needs_read_fill) {
88 retval = fill_read_buffer(file, buffer);
92 pr_debug("%s: count = %zd, pos = %lld, buf = %s\n",
93 __func__, iov_iter_count(to), iocb->ki_pos, buffer->page);
94 if (iocb->ki_pos >= buffer->count)
96 retval = copy_to_iter(buffer->page + iocb->ki_pos,
97 buffer->count - iocb->ki_pos, to);
98 iocb->ki_pos += retval;
102 mutex_unlock(&buffer->mutex);
106 static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
108 struct file *file = iocb->ki_filp;
109 struct configfs_fragment *frag = to_frag(file);
110 struct configfs_buffer *buffer = file->private_data;
114 mutex_lock(&buffer->mutex);
116 /* we don't support switching read/write modes */
117 if (buffer->write_in_progress) {
121 buffer->read_in_progress = true;
123 if (buffer->needs_read_fill) {
124 /* perform first read with buf == NULL to get extent */
125 down_read(&frag->frag_sem);
126 if (!frag->frag_dead)
127 len = buffer->bin_attr->read(buffer->item, NULL, 0);
130 up_read(&frag->frag_sem);
136 /* do not exceed the maximum value */
137 if (buffer->cb_max_size && len > buffer->cb_max_size) {
142 buffer->bin_buffer = vmalloc(len);
143 if (buffer->bin_buffer == NULL) {
147 buffer->bin_buffer_size = len;
149 /* perform second read to fill buffer */
150 down_read(&frag->frag_sem);
151 if (!frag->frag_dead)
152 len = buffer->bin_attr->read(buffer->item,
153 buffer->bin_buffer, len);
156 up_read(&frag->frag_sem);
159 vfree(buffer->bin_buffer);
160 buffer->bin_buffer_size = 0;
161 buffer->bin_buffer = NULL;
165 buffer->needs_read_fill = 0;
168 if (iocb->ki_pos >= buffer->bin_buffer_size)
170 retval = copy_to_iter(buffer->bin_buffer + iocb->ki_pos,
171 buffer->bin_buffer_size - iocb->ki_pos, to);
172 iocb->ki_pos += retval;
176 mutex_unlock(&buffer->mutex);
180 /* Fill [buffer, buffer + pos) with data coming from @from. */
181 static int fill_write_buffer(struct configfs_buffer *buffer, loff_t pos,
182 struct iov_iter *from)
189 buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
193 to_copy = SIMPLE_ATTR_SIZE - 1 - pos;
196 to = buffer->page + pos;
197 copied = copy_from_iter(to, to_copy, from);
198 buffer->needs_read_fill = 1;
199 /* if buf is assumed to contain a string, terminate it by \0,
200 * so e.g. sscanf() can scan the string easily */
202 return copied ? : -EFAULT;
206 flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)
208 struct configfs_fragment *frag = to_frag(file);
211 down_read(&frag->frag_sem);
212 if (!frag->frag_dead)
213 res = buffer->attr->store(buffer->item, buffer->page, count);
214 up_read(&frag->frag_sem);
220 * There is no easy way for us to know if userspace is only doing a partial
221 * write, so we don't support them. We expect the entire buffer to come on the
223 * Hint: if you're writing a value, first read the file, modify only the value
224 * you're changing, then write entire buffer back.
226 static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
228 struct file *file = iocb->ki_filp;
229 struct configfs_buffer *buffer = file->private_data;
232 mutex_lock(&buffer->mutex);
233 len = fill_write_buffer(buffer, iocb->ki_pos, from);
235 len = flush_write_buffer(file, buffer, len);
238 mutex_unlock(&buffer->mutex);
242 static ssize_t configfs_bin_write_iter(struct kiocb *iocb,
243 struct iov_iter *from)
245 struct file *file = iocb->ki_filp;
246 struct configfs_buffer *buffer = file->private_data;
251 mutex_lock(&buffer->mutex);
253 /* we don't support switching read/write modes */
254 if (buffer->read_in_progress) {
258 buffer->write_in_progress = true;
261 end_offset = iocb->ki_pos + iov_iter_count(from);
262 if (end_offset > buffer->bin_buffer_size) {
263 if (buffer->cb_max_size && end_offset > buffer->cb_max_size) {
268 tbuf = vmalloc(end_offset);
274 /* copy old contents */
275 if (buffer->bin_buffer) {
276 memcpy(tbuf, buffer->bin_buffer,
277 buffer->bin_buffer_size);
278 vfree(buffer->bin_buffer);
281 /* clear the new area */
282 memset(tbuf + buffer->bin_buffer_size, 0,
283 end_offset - buffer->bin_buffer_size);
284 buffer->bin_buffer = tbuf;
285 buffer->bin_buffer_size = end_offset;
288 len = copy_from_iter(buffer->bin_buffer + iocb->ki_pos,
289 buffer->bin_buffer_size - iocb->ki_pos, from);
292 mutex_unlock(&buffer->mutex);
293 return len ? : -EFAULT;
296 static int __configfs_open_file(struct inode *inode, struct file *file, int type)
298 struct dentry *dentry = file->f_path.dentry;
299 struct configfs_fragment *frag = to_frag(file);
300 struct configfs_attribute *attr;
301 struct configfs_buffer *buffer;
305 buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
310 down_read(&frag->frag_sem);
311 if (unlikely(frag->frag_dead))
312 goto out_free_buffer;
315 buffer->item = to_item(dentry->d_parent);
317 goto out_free_buffer;
319 attr = to_attr(dentry);
321 goto out_free_buffer;
323 if (type & CONFIGFS_ITEM_BIN_ATTR) {
324 buffer->bin_attr = to_bin_attr(dentry);
325 buffer->cb_max_size = buffer->bin_attr->cb_max_size;
330 buffer->owner = attr->ca_owner;
331 /* Grab the module reference for this attribute if we have one */
333 if (!try_module_get(buffer->owner))
334 goto out_free_buffer;
337 if (!buffer->item->ci_type)
340 buffer->ops = buffer->item->ci_type->ct_item_ops;
342 /* File needs write support.
343 * The inode's perms must say it's ok,
344 * and we must have a store method.
346 if (file->f_mode & FMODE_WRITE) {
347 if (!(inode->i_mode & S_IWUGO))
349 if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
351 if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
355 /* File needs read support.
356 * The inode's perms must say it's ok, and we there
357 * must be a show method for it.
359 if (file->f_mode & FMODE_READ) {
360 if (!(inode->i_mode & S_IRUGO))
362 if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
364 if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
368 mutex_init(&buffer->mutex);
369 buffer->needs_read_fill = 1;
370 buffer->read_in_progress = false;
371 buffer->write_in_progress = false;
372 file->private_data = buffer;
373 up_read(&frag->frag_sem);
377 module_put(buffer->owner);
379 up_read(&frag->frag_sem);
385 static int configfs_release(struct inode *inode, struct file *filp)
387 struct configfs_buffer *buffer = filp->private_data;
389 module_put(buffer->owner);
391 free_page((unsigned long)buffer->page);
392 mutex_destroy(&buffer->mutex);
397 static int configfs_open_file(struct inode *inode, struct file *filp)
399 return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
402 static int configfs_open_bin_file(struct inode *inode, struct file *filp)
404 return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
407 static int configfs_release_bin_file(struct inode *inode, struct file *file)
409 struct configfs_buffer *buffer = file->private_data;
411 if (buffer->write_in_progress) {
412 struct configfs_fragment *frag = to_frag(file);
414 down_read(&frag->frag_sem);
415 if (!frag->frag_dead) {
416 /* result of ->release() is ignored */
417 buffer->bin_attr->write(buffer->item,
419 buffer->bin_buffer_size);
421 up_read(&frag->frag_sem);
424 vfree(buffer->bin_buffer);
426 configfs_release(inode, file);
431 const struct file_operations configfs_file_operations = {
432 .read_iter = configfs_read_iter,
433 .write_iter = configfs_write_iter,
434 .llseek = generic_file_llseek,
435 .open = configfs_open_file,
436 .release = configfs_release,
439 const struct file_operations configfs_bin_file_operations = {
440 .read_iter = configfs_bin_read_iter,
441 .write_iter = configfs_bin_write_iter,
442 .llseek = NULL, /* bin file is not seekable */
443 .open = configfs_open_bin_file,
444 .release = configfs_release_bin_file,
448 * configfs_create_file - create an attribute file for an item.
449 * @item: item we're creating for.
450 * @attr: atrribute descriptor.
453 int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
455 struct dentry *dir = item->ci_dentry;
456 struct configfs_dirent *parent_sd = dir->d_fsdata;
457 umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
460 inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
461 error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
462 CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
463 inode_unlock(d_inode(dir));
469 * configfs_create_bin_file - create a binary attribute file for an item.
470 * @item: item we're creating for.
471 * @bin_attr: atrribute descriptor.
474 int configfs_create_bin_file(struct config_item *item,
475 const struct configfs_bin_attribute *bin_attr)
477 struct dentry *dir = item->ci_dentry;
478 struct configfs_dirent *parent_sd = dir->d_fsdata;
479 umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
482 inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
483 error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
484 CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
485 inode_unlock(dir->d_inode);