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	size_t len;
112
113	/*
114	 * If buf != of->prealloc_buf, we don't know how
115	 * large it is, so cannot safely pass it to ->show
116	 */
117	if (pos || WARN_ON_ONCE(buf != of->prealloc_buf))
118		return 0;
119	len = ops->show(kobj, of->kn->priv, buf);
120	return min(count, len);
121}
122
123/* kernfs write callback for regular sysfs files */
124static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
125			      size_t count, loff_t pos)
126{
127	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
128	struct kobject *kobj = of->kn->parent->priv;
129
130	if (!count)
131		return 0;
132
133	return ops->store(kobj, of->kn->priv, buf, count);
134}
135
136/* kernfs write callback for bin sysfs files */
137static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
138				  size_t count, loff_t pos)
139{
140	struct bin_attribute *battr = of->kn->priv;
141	struct kobject *kobj = of->kn->parent->priv;
142	loff_t size = file_inode(of->file)->i_size;
143
144	if (size) {
145		if (size <= pos)
146			return -EFBIG;
147		count = min_t(ssize_t, count, size - pos);
148	}
149	if (!count)
150		return 0;
151
152	if (!battr->write)
153		return -EIO;
154
155	return battr->write(of->file, kobj, battr, buf, pos, count);
156}
157
158static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
159			     struct vm_area_struct *vma)
160{
161	struct bin_attribute *battr = of->kn->priv;
162	struct kobject *kobj = of->kn->parent->priv;
163
164	return battr->mmap(of->file, kobj, battr, vma);
165}
166
167void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
168{
169	struct kernfs_node *kn = kobj->sd, *tmp;
170
171	if (kn && dir)
172		kn = kernfs_find_and_get(kn, dir);
173	else
174		kernfs_get(kn);
175
176	if (kn && attr) {
177		tmp = kernfs_find_and_get(kn, attr);
178		kernfs_put(kn);
179		kn = tmp;
180	}
181
182	if (kn) {
183		kernfs_notify(kn);
184		kernfs_put(kn);
185	}
186}
187EXPORT_SYMBOL_GPL(sysfs_notify);
188
189static const struct kernfs_ops sysfs_file_kfops_empty = {
190};
191
192static const struct kernfs_ops sysfs_file_kfops_ro = {
193	.seq_show	= sysfs_kf_seq_show,
194};
195
196static const struct kernfs_ops sysfs_file_kfops_wo = {
197	.write		= sysfs_kf_write,
198};
199
200static const struct kernfs_ops sysfs_file_kfops_rw = {
201	.seq_show	= sysfs_kf_seq_show,
202	.write		= sysfs_kf_write,
203};
204
205static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
206	.read		= sysfs_kf_read,
207	.prealloc	= true,
208};
209
210static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
211	.write		= sysfs_kf_write,
212	.prealloc	= true,
213};
214
215static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
216	.read		= sysfs_kf_read,
217	.write		= sysfs_kf_write,
218	.prealloc	= true,
219};
220
221static const struct kernfs_ops sysfs_bin_kfops_ro = {
222	.read		= sysfs_kf_bin_read,
223};
224
225static const struct kernfs_ops sysfs_bin_kfops_wo = {
226	.write		= sysfs_kf_bin_write,
227};
228
229static const struct kernfs_ops sysfs_bin_kfops_rw = {
230	.read		= sysfs_kf_bin_read,
231	.write		= sysfs_kf_bin_write,
232};
233
234static const struct kernfs_ops sysfs_bin_kfops_mmap = {
235	.read		= sysfs_kf_bin_read,
236	.write		= sysfs_kf_bin_write,
237	.mmap		= sysfs_kf_bin_mmap,
238};
239
240int sysfs_add_file_mode_ns(struct kernfs_node *parent,
241			   const struct attribute *attr, bool is_bin,
242			   umode_t mode, const void *ns)
243{
244	struct lock_class_key *key = NULL;
245	const struct kernfs_ops *ops;
246	struct kernfs_node *kn;
247	loff_t size;
248
249	if (!is_bin) {
250		struct kobject *kobj = parent->priv;
251		const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
252
253		/* every kobject with an attribute needs a ktype assigned */
254		if (WARN(!sysfs_ops, KERN_ERR
255			 "missing sysfs attribute operations for kobject: %s\n",
256			 kobject_name(kobj)))
257			return -EINVAL;
258
259		if (sysfs_ops->show && sysfs_ops->store) {
260			if (mode & SYSFS_PREALLOC)
261				ops = &sysfs_prealloc_kfops_rw;
262			else
263				ops = &sysfs_file_kfops_rw;
264		} else if (sysfs_ops->show) {
265			if (mode & SYSFS_PREALLOC)
266				ops = &sysfs_prealloc_kfops_ro;
267			else
268				ops = &sysfs_file_kfops_ro;
269		} else if (sysfs_ops->store) {
270			if (mode & SYSFS_PREALLOC)
271				ops = &sysfs_prealloc_kfops_wo;
272			else
273				ops = &sysfs_file_kfops_wo;
274		} else
275			ops = &sysfs_file_kfops_empty;
276
277		size = PAGE_SIZE;
278	} else {
279		struct bin_attribute *battr = (void *)attr;
280
281		if (battr->mmap)
282			ops = &sysfs_bin_kfops_mmap;
283		else if (battr->read && battr->write)
284			ops = &sysfs_bin_kfops_rw;
285		else if (battr->read)
286			ops = &sysfs_bin_kfops_ro;
287		else if (battr->write)
288			ops = &sysfs_bin_kfops_wo;
289		else
290			ops = &sysfs_file_kfops_empty;
291
292		size = battr->size;
293	}
294
295#ifdef CONFIG_DEBUG_LOCK_ALLOC
296	if (!attr->ignore_lockdep)
297		key = attr->key ?: (struct lock_class_key *)&attr->skey;
298#endif
299	kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
300				  (void *)attr, ns, key);
301	if (IS_ERR(kn)) {
302		if (PTR_ERR(kn) == -EEXIST)
303			sysfs_warn_dup(parent, attr->name);
304		return PTR_ERR(kn);
305	}
306	return 0;
307}
308
309int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
310		   bool is_bin)
311{
312	return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
313}
314
315/**
316 * sysfs_create_file_ns - create an attribute file for an object with custom ns
317 * @kobj: object we're creating for
318 * @attr: attribute descriptor
319 * @ns: namespace the new file should belong to
320 */
321int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
322			 const void *ns)
323{
324	BUG_ON(!kobj || !kobj->sd || !attr);
325
326	return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
327
328}
329EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
330
331int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
332{
333	int err = 0;
334	int i;
335
336	for (i = 0; ptr[i] && !err; i++)
337		err = sysfs_create_file(kobj, ptr[i]);
338	if (err)
339		while (--i >= 0)
340			sysfs_remove_file(kobj, ptr[i]);
341	return err;
342}
343EXPORT_SYMBOL_GPL(sysfs_create_files);
344
345/**
346 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
347 * @kobj: object we're acting for.
348 * @attr: attribute descriptor.
349 * @group: group name.
350 */
351int sysfs_add_file_to_group(struct kobject *kobj,
352		const struct attribute *attr, const char *group)
353{
354	struct kernfs_node *parent;
355	int error;
356
357	if (group) {
358		parent = kernfs_find_and_get(kobj->sd, group);
359	} else {
360		parent = kobj->sd;
361		kernfs_get(parent);
362	}
363
364	if (!parent)
365		return -ENOENT;
366
367	error = sysfs_add_file(parent, attr, false);
368	kernfs_put(parent);
369
370	return error;
371}
372EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
373
374/**
375 * sysfs_chmod_file - update the modified mode value on an object attribute.
376 * @kobj: object we're acting for.
377 * @attr: attribute descriptor.
378 * @mode: file permissions.
379 *
380 */
381int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
382		     umode_t mode)
383{
384	struct kernfs_node *kn;
385	struct iattr newattrs;
386	int rc;
387
388	kn = kernfs_find_and_get(kobj->sd, attr->name);
389	if (!kn)
390		return -ENOENT;
391
392	newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
393	newattrs.ia_valid = ATTR_MODE;
394
395	rc = kernfs_setattr(kn, &newattrs);
396
397	kernfs_put(kn);
398	return rc;
399}
400EXPORT_SYMBOL_GPL(sysfs_chmod_file);
401
402/**
403 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
404 * @kobj: object we're acting for
405 * @attr: attribute descriptor
406 * @ns: namespace tag of the file to remove
407 *
408 * Hash the attribute name and namespace tag and kill the victim.
409 */
410void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
411			  const void *ns)
412{
413	struct kernfs_node *parent = kobj->sd;
414
415	kernfs_remove_by_name_ns(parent, attr->name, ns);
416}
417EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
418
419/**
420 * sysfs_remove_file_self - remove an object attribute from its own method
421 * @kobj: object we're acting for
422 * @attr: attribute descriptor
423 *
424 * See kernfs_remove_self() for details.
425 */
426bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
427{
428	struct kernfs_node *parent = kobj->sd;
429	struct kernfs_node *kn;
430	bool ret;
431
432	kn = kernfs_find_and_get(parent, attr->name);
433	if (WARN_ON_ONCE(!kn))
434		return false;
435
436	ret = kernfs_remove_self(kn);
437
438	kernfs_put(kn);
439	return ret;
440}
441
442void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
443{
444	int i;
445	for (i = 0; ptr[i]; i++)
446		sysfs_remove_file(kobj, ptr[i]);
447}
448EXPORT_SYMBOL_GPL(sysfs_remove_files);
449
450/**
451 * sysfs_remove_file_from_group - remove an attribute file from a group.
452 * @kobj: object we're acting for.
453 * @attr: attribute descriptor.
454 * @group: group name.
455 */
456void sysfs_remove_file_from_group(struct kobject *kobj,
457		const struct attribute *attr, const char *group)
458{
459	struct kernfs_node *parent;
460
461	if (group) {
462		parent = kernfs_find_and_get(kobj->sd, group);
463	} else {
464		parent = kobj->sd;
465		kernfs_get(parent);
466	}
467
468	if (parent) {
469		kernfs_remove_by_name(parent, attr->name);
470		kernfs_put(parent);
471	}
472}
473EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
474
475/**
476 *	sysfs_create_bin_file - create binary file for object.
477 *	@kobj:	object.
478 *	@attr:	attribute descriptor.
479 */
480int sysfs_create_bin_file(struct kobject *kobj,
481			  const struct bin_attribute *attr)
482{
483	BUG_ON(!kobj || !kobj->sd || !attr);
484
485	return sysfs_add_file(kobj->sd, &attr->attr, true);
486}
487EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
488
489/**
490 *	sysfs_remove_bin_file - remove binary file for object.
491 *	@kobj:	object.
492 *	@attr:	attribute descriptor.
493 */
494void sysfs_remove_bin_file(struct kobject *kobj,
495			   const struct bin_attribute *attr)
496{
497	kernfs_remove_by_name(kobj->sd, attr->attr.name);
498}
499EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
500