xref: /openbmc/linux/fs/sysfs/file.c (revision b34e08d5)
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  */
28 static 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  */
42 static 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 */
51 	count = seq_get_buf(sf, &buf);
52 	if (count < PAGE_SIZE) {
53 		seq_commit(sf, -1);
54 		return 0;
55 	}
56 
57 	/*
58 	 * Invoke show().  Control may reach here via seq file lseek even
59 	 * if @ops->show() isn't implemented.
60 	 */
61 	if (ops->show) {
62 		count = ops->show(kobj, of->kn->priv, buf);
63 		if (count < 0)
64 			return count;
65 	}
66 
67 	/*
68 	 * The code works fine with PAGE_SIZE return but it's likely to
69 	 * indicate truncated result or overflow in normal use cases.
70 	 */
71 	if (count >= (ssize_t)PAGE_SIZE) {
72 		print_symbol("fill_read_buffer: %s returned bad count\n",
73 			(unsigned long)ops->show);
74 		/* Try to struggle along */
75 		count = PAGE_SIZE - 1;
76 	}
77 	seq_commit(sf, count);
78 	return 0;
79 }
80 
81 static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
82 				 size_t count, loff_t pos)
83 {
84 	struct bin_attribute *battr = of->kn->priv;
85 	struct kobject *kobj = of->kn->parent->priv;
86 	loff_t size = file_inode(of->file)->i_size;
87 
88 	if (!count)
89 		return 0;
90 
91 	if (size) {
92 		if (pos > size)
93 			return 0;
94 		if (pos + count > size)
95 			count = size - pos;
96 	}
97 
98 	if (!battr->read)
99 		return -EIO;
100 
101 	return battr->read(of->file, kobj, battr, buf, pos, count);
102 }
103 
104 /* kernfs write callback for regular sysfs files */
105 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
106 			      size_t count, loff_t pos)
107 {
108 	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
109 	struct kobject *kobj = of->kn->parent->priv;
110 
111 	if (!count)
112 		return 0;
113 
114 	return ops->store(kobj, of->kn->priv, buf, count);
115 }
116 
117 /* kernfs write callback for bin sysfs files */
118 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
119 				  size_t count, loff_t pos)
120 {
121 	struct bin_attribute *battr = of->kn->priv;
122 	struct kobject *kobj = of->kn->parent->priv;
123 	loff_t size = file_inode(of->file)->i_size;
124 
125 	if (size) {
126 		if (size <= pos)
127 			return 0;
128 		count = min_t(ssize_t, count, size - pos);
129 	}
130 	if (!count)
131 		return 0;
132 
133 	if (!battr->write)
134 		return -EIO;
135 
136 	return battr->write(of->file, kobj, battr, buf, pos, count);
137 }
138 
139 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
140 			     struct vm_area_struct *vma)
141 {
142 	struct bin_attribute *battr = of->kn->priv;
143 	struct kobject *kobj = of->kn->parent->priv;
144 
145 	return battr->mmap(of->file, kobj, battr, vma);
146 }
147 
148 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
149 {
150 	struct kernfs_node *kn = kobj->sd, *tmp;
151 
152 	if (kn && dir)
153 		kn = kernfs_find_and_get(kn, dir);
154 	else
155 		kernfs_get(kn);
156 
157 	if (kn && attr) {
158 		tmp = kernfs_find_and_get(kn, attr);
159 		kernfs_put(kn);
160 		kn = tmp;
161 	}
162 
163 	if (kn) {
164 		kernfs_notify(kn);
165 		kernfs_put(kn);
166 	}
167 }
168 EXPORT_SYMBOL_GPL(sysfs_notify);
169 
170 static const struct kernfs_ops sysfs_file_kfops_empty = {
171 };
172 
173 static const struct kernfs_ops sysfs_file_kfops_ro = {
174 	.seq_show	= sysfs_kf_seq_show,
175 };
176 
177 static const struct kernfs_ops sysfs_file_kfops_wo = {
178 	.write		= sysfs_kf_write,
179 };
180 
181 static const struct kernfs_ops sysfs_file_kfops_rw = {
182 	.seq_show	= sysfs_kf_seq_show,
183 	.write		= sysfs_kf_write,
184 };
185 
186 static const struct kernfs_ops sysfs_bin_kfops_ro = {
187 	.read		= sysfs_kf_bin_read,
188 };
189 
190 static const struct kernfs_ops sysfs_bin_kfops_wo = {
191 	.write		= sysfs_kf_bin_write,
192 };
193 
194 static const struct kernfs_ops sysfs_bin_kfops_rw = {
195 	.read		= sysfs_kf_bin_read,
196 	.write		= sysfs_kf_bin_write,
197 };
198 
199 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
200 	.read		= sysfs_kf_bin_read,
201 	.write		= sysfs_kf_bin_write,
202 	.mmap		= sysfs_kf_bin_mmap,
203 };
204 
205 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
206 			   const struct attribute *attr, bool is_bin,
207 			   umode_t mode, const void *ns)
208 {
209 	struct lock_class_key *key = NULL;
210 	const struct kernfs_ops *ops;
211 	struct kernfs_node *kn;
212 	loff_t size;
213 
214 	if (!is_bin) {
215 		struct kobject *kobj = parent->priv;
216 		const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
217 
218 		/* every kobject with an attribute needs a ktype assigned */
219 		if (WARN(!sysfs_ops, KERN_ERR
220 			 "missing sysfs attribute operations for kobject: %s\n",
221 			 kobject_name(kobj)))
222 			return -EINVAL;
223 
224 		if (sysfs_ops->show && sysfs_ops->store)
225 			ops = &sysfs_file_kfops_rw;
226 		else if (sysfs_ops->show)
227 			ops = &sysfs_file_kfops_ro;
228 		else if (sysfs_ops->store)
229 			ops = &sysfs_file_kfops_wo;
230 		else
231 			ops = &sysfs_file_kfops_empty;
232 
233 		size = PAGE_SIZE;
234 	} else {
235 		struct bin_attribute *battr = (void *)attr;
236 
237 		if (battr->mmap)
238 			ops = &sysfs_bin_kfops_mmap;
239 		else if (battr->read && battr->write)
240 			ops = &sysfs_bin_kfops_rw;
241 		else if (battr->read)
242 			ops = &sysfs_bin_kfops_ro;
243 		else if (battr->write)
244 			ops = &sysfs_bin_kfops_wo;
245 		else
246 			ops = &sysfs_file_kfops_empty;
247 
248 		size = battr->size;
249 	}
250 
251 #ifdef CONFIG_DEBUG_LOCK_ALLOC
252 	if (!attr->ignore_lockdep)
253 		key = attr->key ?: (struct lock_class_key *)&attr->skey;
254 #endif
255 	kn = __kernfs_create_file(parent, attr->name, mode, size, ops,
256 				  (void *)attr, ns, true, key);
257 	if (IS_ERR(kn)) {
258 		if (PTR_ERR(kn) == -EEXIST)
259 			sysfs_warn_dup(parent, attr->name);
260 		return PTR_ERR(kn);
261 	}
262 	return 0;
263 }
264 
265 int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
266 		   bool is_bin)
267 {
268 	return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
269 }
270 
271 /**
272  * sysfs_create_file_ns - create an attribute file for an object with custom ns
273  * @kobj: object we're creating for
274  * @attr: attribute descriptor
275  * @ns: namespace the new file should belong to
276  */
277 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
278 			 const void *ns)
279 {
280 	BUG_ON(!kobj || !kobj->sd || !attr);
281 
282 	return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
283 
284 }
285 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
286 
287 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
288 {
289 	int err = 0;
290 	int i;
291 
292 	for (i = 0; ptr[i] && !err; i++)
293 		err = sysfs_create_file(kobj, ptr[i]);
294 	if (err)
295 		while (--i >= 0)
296 			sysfs_remove_file(kobj, ptr[i]);
297 	return err;
298 }
299 EXPORT_SYMBOL_GPL(sysfs_create_files);
300 
301 /**
302  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
303  * @kobj: object we're acting for.
304  * @attr: attribute descriptor.
305  * @group: group name.
306  */
307 int sysfs_add_file_to_group(struct kobject *kobj,
308 		const struct attribute *attr, const char *group)
309 {
310 	struct kernfs_node *parent;
311 	int error;
312 
313 	if (group) {
314 		parent = kernfs_find_and_get(kobj->sd, group);
315 	} else {
316 		parent = kobj->sd;
317 		kernfs_get(parent);
318 	}
319 
320 	if (!parent)
321 		return -ENOENT;
322 
323 	error = sysfs_add_file(parent, attr, false);
324 	kernfs_put(parent);
325 
326 	return error;
327 }
328 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
329 
330 /**
331  * sysfs_chmod_file - update the modified mode value on an object attribute.
332  * @kobj: object we're acting for.
333  * @attr: attribute descriptor.
334  * @mode: file permissions.
335  *
336  */
337 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
338 		     umode_t mode)
339 {
340 	struct kernfs_node *kn;
341 	struct iattr newattrs;
342 	int rc;
343 
344 	kn = kernfs_find_and_get(kobj->sd, attr->name);
345 	if (!kn)
346 		return -ENOENT;
347 
348 	newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
349 	newattrs.ia_valid = ATTR_MODE;
350 
351 	rc = kernfs_setattr(kn, &newattrs);
352 
353 	kernfs_put(kn);
354 	return rc;
355 }
356 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
357 
358 /**
359  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
360  * @kobj: object we're acting for
361  * @attr: attribute descriptor
362  * @ns: namespace tag of the file to remove
363  *
364  * Hash the attribute name and namespace tag and kill the victim.
365  */
366 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
367 			  const void *ns)
368 {
369 	struct kernfs_node *parent = kobj->sd;
370 
371 	kernfs_remove_by_name_ns(parent, attr->name, ns);
372 }
373 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
374 
375 /**
376  * sysfs_remove_file_self - remove an object attribute from its own method
377  * @kobj: object we're acting for
378  * @attr: attribute descriptor
379  *
380  * See kernfs_remove_self() for details.
381  */
382 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
383 {
384 	struct kernfs_node *parent = kobj->sd;
385 	struct kernfs_node *kn;
386 	bool ret;
387 
388 	kn = kernfs_find_and_get(parent, attr->name);
389 	if (WARN_ON_ONCE(!kn))
390 		return false;
391 
392 	ret = kernfs_remove_self(kn);
393 
394 	kernfs_put(kn);
395 	return ret;
396 }
397 
398 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
399 {
400 	int i;
401 	for (i = 0; ptr[i]; i++)
402 		sysfs_remove_file(kobj, ptr[i]);
403 }
404 EXPORT_SYMBOL_GPL(sysfs_remove_files);
405 
406 /**
407  * sysfs_remove_file_from_group - remove an attribute file from a group.
408  * @kobj: object we're acting for.
409  * @attr: attribute descriptor.
410  * @group: group name.
411  */
412 void sysfs_remove_file_from_group(struct kobject *kobj,
413 		const struct attribute *attr, const char *group)
414 {
415 	struct kernfs_node *parent;
416 
417 	if (group) {
418 		parent = kernfs_find_and_get(kobj->sd, group);
419 	} else {
420 		parent = kobj->sd;
421 		kernfs_get(parent);
422 	}
423 
424 	if (parent) {
425 		kernfs_remove_by_name(parent, attr->name);
426 		kernfs_put(parent);
427 	}
428 }
429 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
430 
431 /**
432  *	sysfs_create_bin_file - create binary file for object.
433  *	@kobj:	object.
434  *	@attr:	attribute descriptor.
435  */
436 int sysfs_create_bin_file(struct kobject *kobj,
437 			  const struct bin_attribute *attr)
438 {
439 	BUG_ON(!kobj || !kobj->sd || !attr);
440 
441 	return sysfs_add_file(kobj->sd, &attr->attr, true);
442 }
443 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
444 
445 /**
446  *	sysfs_remove_bin_file - remove binary file for object.
447  *	@kobj:	object.
448  *	@attr:	attribute descriptor.
449  */
450 void sysfs_remove_bin_file(struct kobject *kobj,
451 			   const struct bin_attribute *attr)
452 {
453 	kernfs_remove_by_name(kobj->sd, attr->attr.name);
454 }
455 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
456 
457 struct sysfs_schedule_callback_struct {
458 	struct list_head	workq_list;
459 	struct kobject		*kobj;
460 	void			(*func)(void *);
461 	void			*data;
462 	struct module		*owner;
463 	struct work_struct	work;
464 };
465 
466 static struct workqueue_struct *sysfs_workqueue;
467 static DEFINE_MUTEX(sysfs_workq_mutex);
468 static LIST_HEAD(sysfs_workq);
469 static void sysfs_schedule_callback_work(struct work_struct *work)
470 {
471 	struct sysfs_schedule_callback_struct *ss = container_of(work,
472 			struct sysfs_schedule_callback_struct, work);
473 
474 	(ss->func)(ss->data);
475 	kobject_put(ss->kobj);
476 	module_put(ss->owner);
477 	mutex_lock(&sysfs_workq_mutex);
478 	list_del(&ss->workq_list);
479 	mutex_unlock(&sysfs_workq_mutex);
480 	kfree(ss);
481 }
482 
483 /**
484  * sysfs_schedule_callback - helper to schedule a callback for a kobject
485  * @kobj: object we're acting for.
486  * @func: callback function to invoke later.
487  * @data: argument to pass to @func.
488  * @owner: module owning the callback code
489  *
490  * sysfs attribute methods must not unregister themselves or their parent
491  * kobject (which would amount to the same thing).  Attempts to do so will
492  * deadlock, since unregistration is mutually exclusive with driver
493  * callbacks.
494  *
495  * Instead methods can call this routine, which will attempt to allocate
496  * and schedule a workqueue request to call back @func with @data as its
497  * argument in the workqueue's process context.  @kobj will be pinned
498  * until @func returns.
499  *
500  * Returns 0 if the request was submitted, -ENOMEM if storage could not
501  * be allocated, -ENODEV if a reference to @owner isn't available,
502  * -EAGAIN if a callback has already been scheduled for @kobj.
503  */
504 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
505 		void *data, struct module *owner)
506 {
507 	struct sysfs_schedule_callback_struct *ss, *tmp;
508 
509 	if (!try_module_get(owner))
510 		return -ENODEV;
511 
512 	mutex_lock(&sysfs_workq_mutex);
513 	list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
514 		if (ss->kobj == kobj) {
515 			module_put(owner);
516 			mutex_unlock(&sysfs_workq_mutex);
517 			return -EAGAIN;
518 		}
519 	mutex_unlock(&sysfs_workq_mutex);
520 
521 	if (sysfs_workqueue == NULL) {
522 		sysfs_workqueue = create_singlethread_workqueue("sysfsd");
523 		if (sysfs_workqueue == NULL) {
524 			module_put(owner);
525 			return -ENOMEM;
526 		}
527 	}
528 
529 	ss = kmalloc(sizeof(*ss), GFP_KERNEL);
530 	if (!ss) {
531 		module_put(owner);
532 		return -ENOMEM;
533 	}
534 	kobject_get(kobj);
535 	ss->kobj = kobj;
536 	ss->func = func;
537 	ss->data = data;
538 	ss->owner = owner;
539 	INIT_WORK(&ss->work, sysfs_schedule_callback_work);
540 	INIT_LIST_HEAD(&ss->workq_list);
541 	mutex_lock(&sysfs_workq_mutex);
542 	list_add_tail(&ss->workq_list, &sysfs_workq);
543 	mutex_unlock(&sysfs_workq_mutex);
544 	queue_work(sysfs_workqueue, &ss->work);
545 	return 0;
546 }
547 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
548