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 retval = copy_to_iter(buffer->page, buffer->count, to);
95 iocb->ki_pos += retval;
99 mutex_unlock(&buffer->mutex);
103 static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
105 struct file *file = iocb->ki_filp;
106 struct configfs_fragment *frag = to_frag(file);
107 struct configfs_buffer *buffer = file->private_data;
111 mutex_lock(&buffer->mutex);
113 /* we don't support switching read/write modes */
114 if (buffer->write_in_progress) {
118 buffer->read_in_progress = true;
120 if (buffer->needs_read_fill) {
121 /* perform first read with buf == NULL to get extent */
122 down_read(&frag->frag_sem);
123 if (!frag->frag_dead)
124 len = buffer->bin_attr->read(buffer->item, NULL, 0);
127 up_read(&frag->frag_sem);
133 /* do not exceed the maximum value */
134 if (buffer->cb_max_size && len > buffer->cb_max_size) {
139 buffer->bin_buffer = vmalloc(len);
140 if (buffer->bin_buffer == NULL) {
144 buffer->bin_buffer_size = len;
146 /* perform second read to fill buffer */
147 down_read(&frag->frag_sem);
148 if (!frag->frag_dead)
149 len = buffer->bin_attr->read(buffer->item,
150 buffer->bin_buffer, len);
153 up_read(&frag->frag_sem);
156 vfree(buffer->bin_buffer);
157 buffer->bin_buffer_size = 0;
158 buffer->bin_buffer = NULL;
162 buffer->needs_read_fill = 0;
165 retval = copy_to_iter(buffer->bin_buffer, buffer->bin_buffer_size, to);
166 iocb->ki_pos += retval;
170 mutex_unlock(&buffer->mutex);
174 static int fill_write_buffer(struct configfs_buffer *buffer,
175 struct iov_iter *from)
180 buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
184 copied = copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from);
185 buffer->needs_read_fill = 1;
186 /* if buf is assumed to contain a string, terminate it by \0,
187 * so e.g. sscanf() can scan the string easily */
188 buffer->page[copied] = 0;
189 return copied ? : -EFAULT;
193 flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)
195 struct configfs_fragment *frag = to_frag(file);
198 down_read(&frag->frag_sem);
199 if (!frag->frag_dead)
200 res = buffer->attr->store(buffer->item, buffer->page, count);
201 up_read(&frag->frag_sem);
207 * There is no easy way for us to know if userspace is only doing a partial
208 * write, so we don't support them. We expect the entire buffer to come on the
210 * Hint: if you're writing a value, first read the file, modify only the value
211 * you're changing, then write entire buffer back.
213 static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
215 struct file *file = iocb->ki_filp;
216 struct configfs_buffer *buffer = file->private_data;
219 mutex_lock(&buffer->mutex);
220 len = fill_write_buffer(buffer, from);
222 len = flush_write_buffer(file, buffer, len);
225 mutex_unlock(&buffer->mutex);
229 static ssize_t configfs_bin_write_iter(struct kiocb *iocb,
230 struct iov_iter *from)
232 struct file *file = iocb->ki_filp;
233 struct configfs_buffer *buffer = file->private_data;
238 mutex_lock(&buffer->mutex);
240 /* we don't support switching read/write modes */
241 if (buffer->read_in_progress) {
245 buffer->write_in_progress = true;
248 end_offset = iocb->ki_pos + iov_iter_count(from);
249 if (end_offset > buffer->bin_buffer_size) {
250 if (buffer->cb_max_size && end_offset > buffer->cb_max_size) {
255 tbuf = vmalloc(end_offset);
261 /* copy old contents */
262 if (buffer->bin_buffer) {
263 memcpy(tbuf, buffer->bin_buffer,
264 buffer->bin_buffer_size);
265 vfree(buffer->bin_buffer);
268 /* clear the new area */
269 memset(tbuf + buffer->bin_buffer_size, 0,
270 end_offset - buffer->bin_buffer_size);
271 buffer->bin_buffer = tbuf;
272 buffer->bin_buffer_size = end_offset;
275 len = copy_from_iter(buffer->bin_buffer, buffer->bin_buffer_size, from);
277 mutex_unlock(&buffer->mutex);
278 return len ? : -EFAULT;
281 static int __configfs_open_file(struct inode *inode, struct file *file, int type)
283 struct dentry *dentry = file->f_path.dentry;
284 struct configfs_fragment *frag = to_frag(file);
285 struct configfs_attribute *attr;
286 struct configfs_buffer *buffer;
290 buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
295 down_read(&frag->frag_sem);
296 if (unlikely(frag->frag_dead))
297 goto out_free_buffer;
300 buffer->item = to_item(dentry->d_parent);
302 goto out_free_buffer;
304 attr = to_attr(dentry);
306 goto out_free_buffer;
308 if (type & CONFIGFS_ITEM_BIN_ATTR) {
309 buffer->bin_attr = to_bin_attr(dentry);
310 buffer->cb_max_size = buffer->bin_attr->cb_max_size;
315 buffer->owner = attr->ca_owner;
316 /* Grab the module reference for this attribute if we have one */
318 if (!try_module_get(buffer->owner))
319 goto out_free_buffer;
322 if (!buffer->item->ci_type)
325 buffer->ops = buffer->item->ci_type->ct_item_ops;
327 /* File needs write support.
328 * The inode's perms must say it's ok,
329 * and we must have a store method.
331 if (file->f_mode & FMODE_WRITE) {
332 if (!(inode->i_mode & S_IWUGO))
334 if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
336 if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
340 /* File needs read support.
341 * The inode's perms must say it's ok, and we there
342 * must be a show method for it.
344 if (file->f_mode & FMODE_READ) {
345 if (!(inode->i_mode & S_IRUGO))
347 if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
349 if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
353 mutex_init(&buffer->mutex);
354 buffer->needs_read_fill = 1;
355 buffer->read_in_progress = false;
356 buffer->write_in_progress = false;
357 file->private_data = buffer;
358 up_read(&frag->frag_sem);
362 module_put(buffer->owner);
364 up_read(&frag->frag_sem);
370 static int configfs_release(struct inode *inode, struct file *filp)
372 struct configfs_buffer *buffer = filp->private_data;
374 module_put(buffer->owner);
376 free_page((unsigned long)buffer->page);
377 mutex_destroy(&buffer->mutex);
382 static int configfs_open_file(struct inode *inode, struct file *filp)
384 return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
387 static int configfs_open_bin_file(struct inode *inode, struct file *filp)
389 return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
392 static int configfs_release_bin_file(struct inode *inode, struct file *file)
394 struct configfs_buffer *buffer = file->private_data;
396 if (buffer->write_in_progress) {
397 struct configfs_fragment *frag = to_frag(file);
399 down_read(&frag->frag_sem);
400 if (!frag->frag_dead) {
401 /* result of ->release() is ignored */
402 buffer->bin_attr->write(buffer->item,
404 buffer->bin_buffer_size);
406 up_read(&frag->frag_sem);
409 vfree(buffer->bin_buffer);
411 configfs_release(inode, file);
416 const struct file_operations configfs_file_operations = {
417 .read_iter = configfs_read_iter,
418 .write_iter = configfs_write_iter,
419 .llseek = generic_file_llseek,
420 .open = configfs_open_file,
421 .release = configfs_release,
424 const struct file_operations configfs_bin_file_operations = {
425 .read_iter = configfs_bin_read_iter,
426 .write_iter = configfs_bin_write_iter,
427 .llseek = NULL, /* bin file is not seekable */
428 .open = configfs_open_bin_file,
429 .release = configfs_release_bin_file,
433 * configfs_create_file - create an attribute file for an item.
434 * @item: item we're creating for.
435 * @attr: atrribute descriptor.
438 int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
440 struct dentry *dir = item->ci_dentry;
441 struct configfs_dirent *parent_sd = dir->d_fsdata;
442 umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
445 inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
446 error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
447 CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
448 inode_unlock(d_inode(dir));
454 * configfs_create_bin_file - create a binary attribute file for an item.
455 * @item: item we're creating for.
456 * @bin_attr: atrribute descriptor.
459 int configfs_create_bin_file(struct config_item *item,
460 const struct configfs_bin_attribute *bin_attr)
462 struct dentry *dir = item->ci_dentry;
463 struct configfs_dirent *parent_sd = dir->d_fsdata;
464 umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
467 inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
468 error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
469 CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
470 inode_unlock(dir->d_inode);