1/*
2 * fs/sysfs/file.c - sysfs regular (text) file implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
7 *
8 * This file is released under the GPLv2.
9 *
10 * Please see Documentation/filesystems/sysfs.txt for more information.
11 */
12
13#include <linux/module.h>
14#include <linux/kobject.h>
15#include <linux/kallsyms.h>
16#include <linux/slab.h>
17#include <linux/list.h>
18#include <linux/mutex.h>
19#include <linux/seq_file.h>
20
21#include "sysfs.h"
22#include "../kernfs/kernfs-internal.h"
23
24/*
25 * Determine ktype->sysfs_ops for the given kernfs_node.  This function
26 * must be called while holding an active reference.
27 */
28static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
29{
30	struct kobject *kobj = kn->parent->priv;
31
32	if (kn->flags & KERNFS_LOCKDEP)
33		lockdep_assert_held(kn);
34	return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
35}
36
37/*
38 * Reads on sysfs are handled through seq_file, which takes care of hairy
39 * details like buffering and seeking.  The following function pipes
40 * sysfs_ops->show() result through seq_file.
41 */
42static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
43{
44	struct kernfs_open_file *of = sf->private;
45	struct kobject *kobj = of->kn->parent->priv;
46	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
47	ssize_t count;
48	char *buf;
49
50	/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
51	count = seq_get_buf(sf, &buf);
52	if (count < PAGE_SIZE) {
53		seq_commit(sf, -1);
54		return 0;
55	}
56	memset(buf, 0, PAGE_SIZE);
57
58	/*
59	 * Invoke show().  Control may reach here via seq file lseek even
60	 * if @ops->show() isn't implemented.
61	 */
62	if (ops->show) {
63		count = ops->show(kobj, of->kn->priv, buf);
64		if (count < 0)
65			return count;
66	}
67
68	/*
69	 * The code works fine with PAGE_SIZE return but it's likely to
70	 * indicate truncated result or overflow in normal use cases.
71	 */
72	if (count >= (ssize_t)PAGE_SIZE) {
73		print_symbol("fill_read_buffer: %s returned bad count\n",
74			(unsigned long)ops->show);
75		/* Try to struggle along */
76		count = PAGE_SIZE - 1;
77	}
78	seq_commit(sf, count);
79	return 0;
80}
81
82static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
83				 size_t count, loff_t pos)
84{
85	struct bin_attribute *battr = of->kn->priv;
86	struct kobject *kobj = of->kn->parent->priv;
87	loff_t size = file_inode(of->file)->i_size;
88
89	if (!count)
90		return 0;
91
92	if (size) {
93		if (pos > size)
94			return 0;
95		if (pos + count > size)
96			count = size - pos;
97	}
98
99	if (!battr->read)
100		return -EIO;
101
102	return battr->read(of->file, kobj, battr, buf, pos, count);
103}
104
105/* kernfs read callback for regular sysfs files with pre-alloc */
106static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
107			     size_t count, loff_t pos)
108{
109	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
110	struct kobject *kobj = of->kn->parent->priv;
111
112	/*
113	 * If buf != of->prealloc_buf, we don't know how
114	 * large it is, so cannot safely pass it to ->show
115	 */
116	if (pos || WARN_ON_ONCE(buf != of->prealloc_buf))
117		return 0;
118	return ops->show(kobj, of->kn->priv, buf);
119}
120
121/* kernfs write callback for regular sysfs files */
122static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
123			      size_t count, loff_t pos)
124{
125	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
126	struct kobject *kobj = of->kn->parent->priv;
127
128	if (!count)
129		return 0;
130
131	return ops->store(kobj, of->kn->priv, buf, count);
132}
133
134/* kernfs write callback for bin sysfs files */
135static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
136				  size_t count, loff_t pos)
137{
138	struct bin_attribute *battr = of->kn->priv;
139	struct kobject *kobj = of->kn->parent->priv;
140	loff_t size = file_inode(of->file)->i_size;
141
142	if (size) {
143		if (size <= pos)
144			return -EFBIG;
145		count = min_t(ssize_t, count, size - pos);
146	}
147	if (!count)
148		return 0;
149
150	if (!battr->write)
151		return -EIO;
152
153	return battr->write(of->file, kobj, battr, buf, pos, count);
154}
155
156static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
157			     struct vm_area_struct *vma)
158{
159	struct bin_attribute *battr = of->kn->priv;
160	struct kobject *kobj = of->kn->parent->priv;
161
162	return battr->mmap(of->file, kobj, battr, vma);
163}
164
165void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
166{
167	struct kernfs_node *kn = kobj->sd, *tmp;
168
169	if (kn && dir)
170		kn = kernfs_find_and_get(kn, dir);
171	else
172		kernfs_get(kn);
173
174	if (kn && attr) {
175		tmp = kernfs_find_and_get(kn, attr);
176		kernfs_put(kn);
177		kn = tmp;
178	}
179
180	if (kn) {
181		kernfs_notify(kn);
182		kernfs_put(kn);
183	}
184}
185EXPORT_SYMBOL_GPL(sysfs_notify);
186
187static const struct kernfs_ops sysfs_file_kfops_empty = {
188};
189
190static const struct kernfs_ops sysfs_file_kfops_ro = {
191	.seq_show	= sysfs_kf_seq_show,
192};
193
194static const struct kernfs_ops sysfs_file_kfops_wo = {
195	.write		= sysfs_kf_write,
196};
197
198static const struct kernfs_ops sysfs_file_kfops_rw = {
199	.seq_show	= sysfs_kf_seq_show,
200	.write		= sysfs_kf_write,
201};
202
203static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
204	.read		= sysfs_kf_read,
205	.prealloc	= true,
206};
207
208static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
209	.write		= sysfs_kf_write,
210	.prealloc	= true,
211};
212
213static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
214	.read		= sysfs_kf_read,
215	.write		= sysfs_kf_write,
216	.prealloc	= true,
217};
218
219static const struct kernfs_ops sysfs_bin_kfops_ro = {
220	.read		= sysfs_kf_bin_read,
221};
222
223static const struct kernfs_ops sysfs_bin_kfops_wo = {
224	.write		= sysfs_kf_bin_write,
225};
226
227static const struct kernfs_ops sysfs_bin_kfops_rw = {
228	.read		= sysfs_kf_bin_read,
229	.write		= sysfs_kf_bin_write,
230};
231
232static const struct kernfs_ops sysfs_bin_kfops_mmap = {
233	.read		= sysfs_kf_bin_read,
234	.write		= sysfs_kf_bin_write,
235	.mmap		= sysfs_kf_bin_mmap,
236};
237
238int sysfs_add_file_mode_ns(struct kernfs_node *parent,
239			   const struct attribute *attr, bool is_bin,
240			   umode_t mode, const void *ns)
241{
242	struct lock_class_key *key = NULL;
243	const struct kernfs_ops *ops;
244	struct kernfs_node *kn;
245	loff_t size;
246
247	if (!is_bin) {
248		struct kobject *kobj = parent->priv;
249		const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
250
251		/* every kobject with an attribute needs a ktype assigned */
252		if (WARN(!sysfs_ops, KERN_ERR
253			 "missing sysfs attribute operations for kobject: %s\n",
254			 kobject_name(kobj)))
255			return -EINVAL;
256
257		if (sysfs_ops->show && sysfs_ops->store) {
258			if (mode & SYSFS_PREALLOC)
259				ops = &sysfs_prealloc_kfops_rw;
260			else
261				ops = &sysfs_file_kfops_rw;
262		} else if (sysfs_ops->show) {
263			if (mode & SYSFS_PREALLOC)
264				ops = &sysfs_prealloc_kfops_ro;
265			else
266				ops = &sysfs_file_kfops_ro;
267		} else if (sysfs_ops->store) {
268			if (mode & SYSFS_PREALLOC)
269				ops = &sysfs_prealloc_kfops_wo;
270			else
271				ops = &sysfs_file_kfops_wo;
272		} else
273			ops = &sysfs_file_kfops_empty;
274
275		size = PAGE_SIZE;
276	} else {
277		struct bin_attribute *battr = (void *)attr;
278
279		if (battr->mmap)
280			ops = &sysfs_bin_kfops_mmap;
281		else if (battr->read && battr->write)
282			ops = &sysfs_bin_kfops_rw;
283		else if (battr->read)
284			ops = &sysfs_bin_kfops_ro;
285		else if (battr->write)
286			ops = &sysfs_bin_kfops_wo;
287		else
288			ops = &sysfs_file_kfops_empty;
289
290		size = battr->size;
291	}
292
293#ifdef CONFIG_DEBUG_LOCK_ALLOC
294	if (!attr->ignore_lockdep)
295		key = attr->key ?: (struct lock_class_key *)&attr->skey;
296#endif
297	kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
298				  (void *)attr, ns, key);
299	if (IS_ERR(kn)) {
300		if (PTR_ERR(kn) == -EEXIST)
301			sysfs_warn_dup(parent, attr->name);
302		return PTR_ERR(kn);
303	}
304	return 0;
305}
306
307int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
308		   bool is_bin)
309{
310	return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
311}
312
313/**
314 * sysfs_create_file_ns - create an attribute file for an object with custom ns
315 * @kobj: object we're creating for
316 * @attr: attribute descriptor
317 * @ns: namespace the new file should belong to
318 */
319int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
320			 const void *ns)
321{
322	BUG_ON(!kobj || !kobj->sd || !attr);
323
324	return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
325
326}
327EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
328
329int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
330{
331	int err = 0;
332	int i;
333
334	for (i = 0; ptr[i] && !err; i++)
335		err = sysfs_create_file(kobj, ptr[i]);
336	if (err)
337		while (--i >= 0)
338			sysfs_remove_file(kobj, ptr[i]);
339	return err;
340}
341EXPORT_SYMBOL_GPL(sysfs_create_files);
342
343/**
344 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
345 * @kobj: object we're acting for.
346 * @attr: attribute descriptor.
347 * @group: group name.
348 */
349int sysfs_add_file_to_group(struct kobject *kobj,
350		const struct attribute *attr, const char *group)
351{
352	struct kernfs_node *parent;
353	int error;
354
355	if (group) {
356		parent = kernfs_find_and_get(kobj->sd, group);
357	} else {
358		parent = kobj->sd;
359		kernfs_get(parent);
360	}
361
362	if (!parent)
363		return -ENOENT;
364
365	error = sysfs_add_file(parent, attr, false);
366	kernfs_put(parent);
367
368	return error;
369}
370EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
371
372/**
373 * sysfs_chmod_file - update the modified mode value on an object attribute.
374 * @kobj: object we're acting for.
375 * @attr: attribute descriptor.
376 * @mode: file permissions.
377 *
378 */
379int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
380		     umode_t mode)
381{
382	struct kernfs_node *kn;
383	struct iattr newattrs;
384	int rc;
385
386	kn = kernfs_find_and_get(kobj->sd, attr->name);
387	if (!kn)
388		return -ENOENT;
389
390	newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
391	newattrs.ia_valid = ATTR_MODE;
392
393	rc = kernfs_setattr(kn, &newattrs);
394
395	kernfs_put(kn);
396	return rc;
397}
398EXPORT_SYMBOL_GPL(sysfs_chmod_file);
399
400/**
401 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
402 * @kobj: object we're acting for
403 * @attr: attribute descriptor
404 * @ns: namespace tag of the file to remove
405 *
406 * Hash the attribute name and namespace tag and kill the victim.
407 */
408void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
409			  const void *ns)
410{
411	struct kernfs_node *parent = kobj->sd;
412
413	kernfs_remove_by_name_ns(parent, attr->name, ns);
414}
415EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
416
417/**
418 * sysfs_remove_file_self - remove an object attribute from its own method
419 * @kobj: object we're acting for
420 * @attr: attribute descriptor
421 *
422 * See kernfs_remove_self() for details.
423 */
424bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
425{
426	struct kernfs_node *parent = kobj->sd;
427	struct kernfs_node *kn;
428	bool ret;
429
430	kn = kernfs_find_and_get(parent, attr->name);
431	if (WARN_ON_ONCE(!kn))
432		return false;
433
434	ret = kernfs_remove_self(kn);
435
436	kernfs_put(kn);
437	return ret;
438}
439
440void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
441{
442	int i;
443	for (i = 0; ptr[i]; i++)
444		sysfs_remove_file(kobj, ptr[i]);
445}
446EXPORT_SYMBOL_GPL(sysfs_remove_files);
447
448/**
449 * sysfs_remove_file_from_group - remove an attribute file from a group.
450 * @kobj: object we're acting for.
451 * @attr: attribute descriptor.
452 * @group: group name.
453 */
454void sysfs_remove_file_from_group(struct kobject *kobj,
455		const struct attribute *attr, const char *group)
456{
457	struct kernfs_node *parent;
458
459	if (group) {
460		parent = kernfs_find_and_get(kobj->sd, group);
461	} else {
462		parent = kobj->sd;
463		kernfs_get(parent);
464	}
465
466	if (parent) {
467		kernfs_remove_by_name(parent, attr->name);
468		kernfs_put(parent);
469	}
470}
471EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
472
473/**
474 *	sysfs_create_bin_file - create binary file for object.
475 *	@kobj:	object.
476 *	@attr:	attribute descriptor.
477 */
478int sysfs_create_bin_file(struct kobject *kobj,
479			  const struct bin_attribute *attr)
480{
481	BUG_ON(!kobj || !kobj->sd || !attr);
482
483	return sysfs_add_file(kobj->sd, &attr->attr, true);
484}
485EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
486
487/**
488 *	sysfs_remove_bin_file - remove binary file for object.
489 *	@kobj:	object.
490 *	@attr:	attribute descriptor.
491 */
492void sysfs_remove_bin_file(struct kobject *kobj,
493			   const struct bin_attribute *attr)
494{
495	kernfs_remove_by_name(kobj->sd, attr->attr.name);
496}
497EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
498