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Linux/fs/sysfs/file.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * fs/sysfs/file.c - sysfs regular (text) file implementation
  4  *
  5  * Copyright (c) 2001-3 Patrick Mochel
  6  * Copyright (c) 2007 SUSE Linux Products GmbH
  7  * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
  8  *
  9  * Please see Documentation/filesystems/sysfs.txt for more information.
 10  */
 11 
 12 #include <linux/module.h>
 13 #include <linux/kobject.h>
 14 #include <linux/slab.h>
 15 #include <linux/list.h>
 16 #include <linux/mutex.h>
 17 #include <linux/seq_file.h>
 18 
 19 #include "sysfs.h"
 20 #include "../kernfs/kernfs-internal.h"
 21 
 22 /*
 23  * Determine ktype->sysfs_ops for the given kernfs_node.  This function
 24  * must be called while holding an active reference.
 25  */
 26 static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
 27 {
 28         struct kobject *kobj = kn->parent->priv;
 29 
 30         if (kn->flags & KERNFS_LOCKDEP)
 31                 lockdep_assert_held(kn);
 32         return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
 33 }
 34 
 35 /*
 36  * Reads on sysfs are handled through seq_file, which takes care of hairy
 37  * details like buffering and seeking.  The following function pipes
 38  * sysfs_ops->show() result through seq_file.
 39  */
 40 static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
 41 {
 42         struct kernfs_open_file *of = sf->private;
 43         struct kobject *kobj = of->kn->parent->priv;
 44         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 45         ssize_t count;
 46         char *buf;
 47 
 48         /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
 49         count = seq_get_buf(sf, &buf);
 50         if (count < PAGE_SIZE) {
 51                 seq_commit(sf, -1);
 52                 return 0;
 53         }
 54         memset(buf, 0, PAGE_SIZE);
 55 
 56         /*
 57          * Invoke show().  Control may reach here via seq file lseek even
 58          * if @ops->show() isn't implemented.
 59          */
 60         if (ops->show) {
 61                 count = ops->show(kobj, of->kn->priv, buf);
 62                 if (count < 0)
 63                         return count;
 64         }
 65 
 66         /*
 67          * The code works fine with PAGE_SIZE return but it's likely to
 68          * indicate truncated result or overflow in normal use cases.
 69          */
 70         if (count >= (ssize_t)PAGE_SIZE) {
 71                 printk("fill_read_buffer: %pS returned bad count\n",
 72                                 ops->show);
 73                 /* Try to struggle along */
 74                 count = PAGE_SIZE - 1;
 75         }
 76         seq_commit(sf, count);
 77         return 0;
 78 }
 79 
 80 static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
 81                                  size_t count, loff_t pos)
 82 {
 83         struct bin_attribute *battr = of->kn->priv;
 84         struct kobject *kobj = of->kn->parent->priv;
 85         loff_t size = file_inode(of->file)->i_size;
 86 
 87         if (!count)
 88                 return 0;
 89 
 90         if (size) {
 91                 if (pos >= size)
 92                         return 0;
 93                 if (pos + count > size)
 94                         count = size - pos;
 95         }
 96 
 97         if (!battr->read)
 98                 return -EIO;
 99 
100         return battr->read(of->file, kobj, battr, buf, pos, count);
101 }
102 
103 /* kernfs read callback for regular sysfs files with pre-alloc */
104 static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
105                              size_t count, loff_t pos)
106 {
107         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
108         struct kobject *kobj = of->kn->parent->priv;
109         ssize_t len;
110 
111         /*
112          * If buf != of->prealloc_buf, we don't know how
113          * large it is, so cannot safely pass it to ->show
114          */
115         if (WARN_ON_ONCE(buf != of->prealloc_buf))
116                 return 0;
117         len = ops->show(kobj, of->kn->priv, buf);
118         if (len < 0)
119                 return len;
120         if (pos) {
121                 if (len <= pos)
122                         return 0;
123                 len -= pos;
124                 memmove(buf, buf + pos, len);
125         }
126         return min_t(ssize_t, count, len);
127 }
128 
129 /* kernfs write callback for regular sysfs files */
130 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
131                               size_t count, loff_t pos)
132 {
133         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
134         struct kobject *kobj = of->kn->parent->priv;
135 
136         if (!count)
137                 return 0;
138 
139         return ops->store(kobj, of->kn->priv, buf, count);
140 }
141 
142 /* kernfs write callback for bin sysfs files */
143 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
144                                   size_t count, loff_t pos)
145 {
146         struct bin_attribute *battr = of->kn->priv;
147         struct kobject *kobj = of->kn->parent->priv;
148         loff_t size = file_inode(of->file)->i_size;
149 
150         if (size) {
151                 if (size <= pos)
152                         return -EFBIG;
153                 count = min_t(ssize_t, count, size - pos);
154         }
155         if (!count)
156                 return 0;
157 
158         if (!battr->write)
159                 return -EIO;
160 
161         return battr->write(of->file, kobj, battr, buf, pos, count);
162 }
163 
164 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
165                              struct vm_area_struct *vma)
166 {
167         struct bin_attribute *battr = of->kn->priv;
168         struct kobject *kobj = of->kn->parent->priv;
169 
170         return battr->mmap(of->file, kobj, battr, vma);
171 }
172 
173 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
174 {
175         struct kernfs_node *kn = kobj->sd, *tmp;
176 
177         if (kn && dir)
178                 kn = kernfs_find_and_get(kn, dir);
179         else
180                 kernfs_get(kn);
181 
182         if (kn && attr) {
183                 tmp = kernfs_find_and_get(kn, attr);
184                 kernfs_put(kn);
185                 kn = tmp;
186         }
187 
188         if (kn) {
189                 kernfs_notify(kn);
190                 kernfs_put(kn);
191         }
192 }
193 EXPORT_SYMBOL_GPL(sysfs_notify);
194 
195 static const struct kernfs_ops sysfs_file_kfops_empty = {
196 };
197 
198 static const struct kernfs_ops sysfs_file_kfops_ro = {
199         .seq_show       = sysfs_kf_seq_show,
200 };
201 
202 static const struct kernfs_ops sysfs_file_kfops_wo = {
203         .write          = sysfs_kf_write,
204 };
205 
206 static const struct kernfs_ops sysfs_file_kfops_rw = {
207         .seq_show       = sysfs_kf_seq_show,
208         .write          = sysfs_kf_write,
209 };
210 
211 static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
212         .read           = sysfs_kf_read,
213         .prealloc       = true,
214 };
215 
216 static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
217         .write          = sysfs_kf_write,
218         .prealloc       = true,
219 };
220 
221 static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
222         .read           = sysfs_kf_read,
223         .write          = sysfs_kf_write,
224         .prealloc       = true,
225 };
226 
227 static const struct kernfs_ops sysfs_bin_kfops_ro = {
228         .read           = sysfs_kf_bin_read,
229 };
230 
231 static const struct kernfs_ops sysfs_bin_kfops_wo = {
232         .write          = sysfs_kf_bin_write,
233 };
234 
235 static const struct kernfs_ops sysfs_bin_kfops_rw = {
236         .read           = sysfs_kf_bin_read,
237         .write          = sysfs_kf_bin_write,
238 };
239 
240 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
241         .read           = sysfs_kf_bin_read,
242         .write          = sysfs_kf_bin_write,
243         .mmap           = sysfs_kf_bin_mmap,
244 };
245 
246 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
247                            const struct attribute *attr, bool is_bin,
248                            umode_t mode, kuid_t uid, kgid_t gid, const void *ns)
249 {
250         struct lock_class_key *key = NULL;
251         const struct kernfs_ops *ops;
252         struct kernfs_node *kn;
253         loff_t size;
254 
255         if (!is_bin) {
256                 struct kobject *kobj = parent->priv;
257                 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
258 
259                 /* every kobject with an attribute needs a ktype assigned */
260                 if (WARN(!sysfs_ops, KERN_ERR
261                          "missing sysfs attribute operations for kobject: %s\n",
262                          kobject_name(kobj)))
263                         return -EINVAL;
264 
265                 if (sysfs_ops->show && sysfs_ops->store) {
266                         if (mode & SYSFS_PREALLOC)
267                                 ops = &sysfs_prealloc_kfops_rw;
268                         else
269                                 ops = &sysfs_file_kfops_rw;
270                 } else if (sysfs_ops->show) {
271                         if (mode & SYSFS_PREALLOC)
272                                 ops = &sysfs_prealloc_kfops_ro;
273                         else
274                                 ops = &sysfs_file_kfops_ro;
275                 } else if (sysfs_ops->store) {
276                         if (mode & SYSFS_PREALLOC)
277                                 ops = &sysfs_prealloc_kfops_wo;
278                         else
279                                 ops = &sysfs_file_kfops_wo;
280                 } else
281                         ops = &sysfs_file_kfops_empty;
282 
283                 size = PAGE_SIZE;
284         } else {
285                 struct bin_attribute *battr = (void *)attr;
286 
287                 if (battr->mmap)
288                         ops = &sysfs_bin_kfops_mmap;
289                 else if (battr->read && battr->write)
290                         ops = &sysfs_bin_kfops_rw;
291                 else if (battr->read)
292                         ops = &sysfs_bin_kfops_ro;
293                 else if (battr->write)
294                         ops = &sysfs_bin_kfops_wo;
295                 else
296                         ops = &sysfs_file_kfops_empty;
297 
298                 size = battr->size;
299         }
300 
301 #ifdef CONFIG_DEBUG_LOCK_ALLOC
302         if (!attr->ignore_lockdep)
303                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
304 #endif
305 
306         kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
307                                   size, ops, (void *)attr, ns, key);
308         if (IS_ERR(kn)) {
309                 if (PTR_ERR(kn) == -EEXIST)
310                         sysfs_warn_dup(parent, attr->name);
311                 return PTR_ERR(kn);
312         }
313         return 0;
314 }
315 
316 /**
317  * sysfs_create_file_ns - create an attribute file for an object with custom ns
318  * @kobj: object we're creating for
319  * @attr: attribute descriptor
320  * @ns: namespace the new file should belong to
321  */
322 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
323                          const void *ns)
324 {
325         kuid_t uid;
326         kgid_t gid;
327 
328         if (WARN_ON(!kobj || !kobj->sd || !attr))
329                 return -EINVAL;
330 
331         kobject_get_ownership(kobj, &uid, &gid);
332         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode,
333                                       uid, gid, ns);
334 
335 }
336 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
337 
338 int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
339 {
340         int err = 0;
341         int i;
342 
343         for (i = 0; ptr[i] && !err; i++)
344                 err = sysfs_create_file(kobj, ptr[i]);
345         if (err)
346                 while (--i >= 0)
347                         sysfs_remove_file(kobj, ptr[i]);
348         return err;
349 }
350 EXPORT_SYMBOL_GPL(sysfs_create_files);
351 
352 /**
353  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
354  * @kobj: object we're acting for.
355  * @attr: attribute descriptor.
356  * @group: group name.
357  */
358 int sysfs_add_file_to_group(struct kobject *kobj,
359                 const struct attribute *attr, const char *group)
360 {
361         struct kernfs_node *parent;
362         kuid_t uid;
363         kgid_t gid;
364         int error;
365 
366         if (group) {
367                 parent = kernfs_find_and_get(kobj->sd, group);
368         } else {
369                 parent = kobj->sd;
370                 kernfs_get(parent);
371         }
372 
373         if (!parent)
374                 return -ENOENT;
375 
376         kobject_get_ownership(kobj, &uid, &gid);
377         error = sysfs_add_file_mode_ns(parent, attr, false,
378                                        attr->mode, uid, gid, NULL);
379         kernfs_put(parent);
380 
381         return error;
382 }
383 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
384 
385 /**
386  * sysfs_chmod_file - update the modified mode value on an object attribute.
387  * @kobj: object we're acting for.
388  * @attr: attribute descriptor.
389  * @mode: file permissions.
390  *
391  */
392 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
393                      umode_t mode)
394 {
395         struct kernfs_node *kn;
396         struct iattr newattrs;
397         int rc;
398 
399         kn = kernfs_find_and_get(kobj->sd, attr->name);
400         if (!kn)
401                 return -ENOENT;
402 
403         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
404         newattrs.ia_valid = ATTR_MODE;
405 
406         rc = kernfs_setattr(kn, &newattrs);
407 
408         kernfs_put(kn);
409         return rc;
410 }
411 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
412 
413 /**
414  * sysfs_break_active_protection - break "active" protection
415  * @kobj: The kernel object @attr is associated with.
416  * @attr: The attribute to break the "active" protection for.
417  *
418  * With sysfs, just like kernfs, deletion of an attribute is postponed until
419  * all active .show() and .store() callbacks have finished unless this function
420  * is called. Hence this function is useful in methods that implement self
421  * deletion.
422  */
423 struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
424                                                   const struct attribute *attr)
425 {
426         struct kernfs_node *kn;
427 
428         kobject_get(kobj);
429         kn = kernfs_find_and_get(kobj->sd, attr->name);
430         if (kn)
431                 kernfs_break_active_protection(kn);
432         return kn;
433 }
434 EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
435 
436 /**
437  * sysfs_unbreak_active_protection - restore "active" protection
438  * @kn: Pointer returned by sysfs_break_active_protection().
439  *
440  * Undo the effects of sysfs_break_active_protection(). Since this function
441  * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
442  * argument passed to sysfs_break_active_protection() that attribute may have
443  * been removed between the sysfs_break_active_protection() and
444  * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
445  * this function has returned.
446  */
447 void sysfs_unbreak_active_protection(struct kernfs_node *kn)
448 {
449         struct kobject *kobj = kn->parent->priv;
450 
451         kernfs_unbreak_active_protection(kn);
452         kernfs_put(kn);
453         kobject_put(kobj);
454 }
455 EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
456 
457 /**
458  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
459  * @kobj: object we're acting for
460  * @attr: attribute descriptor
461  * @ns: namespace tag of the file to remove
462  *
463  * Hash the attribute name and namespace tag and kill the victim.
464  */
465 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
466                           const void *ns)
467 {
468         struct kernfs_node *parent = kobj->sd;
469 
470         kernfs_remove_by_name_ns(parent, attr->name, ns);
471 }
472 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
473 
474 /**
475  * sysfs_remove_file_self - remove an object attribute from its own method
476  * @kobj: object we're acting for
477  * @attr: attribute descriptor
478  *
479  * See kernfs_remove_self() for details.
480  */
481 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
482 {
483         struct kernfs_node *parent = kobj->sd;
484         struct kernfs_node *kn;
485         bool ret;
486 
487         kn = kernfs_find_and_get(parent, attr->name);
488         if (WARN_ON_ONCE(!kn))
489                 return false;
490 
491         ret = kernfs_remove_self(kn);
492 
493         kernfs_put(kn);
494         return ret;
495 }
496 
497 void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
498 {
499         int i;
500         for (i = 0; ptr[i]; i++)
501                 sysfs_remove_file(kobj, ptr[i]);
502 }
503 EXPORT_SYMBOL_GPL(sysfs_remove_files);
504 
505 /**
506  * sysfs_remove_file_from_group - remove an attribute file from a group.
507  * @kobj: object we're acting for.
508  * @attr: attribute descriptor.
509  * @group: group name.
510  */
511 void sysfs_remove_file_from_group(struct kobject *kobj,
512                 const struct attribute *attr, const char *group)
513 {
514         struct kernfs_node *parent;
515 
516         if (group) {
517                 parent = kernfs_find_and_get(kobj->sd, group);
518         } else {
519                 parent = kobj->sd;
520                 kernfs_get(parent);
521         }
522 
523         if (parent) {
524                 kernfs_remove_by_name(parent, attr->name);
525                 kernfs_put(parent);
526         }
527 }
528 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
529 
530 /**
531  *      sysfs_create_bin_file - create binary file for object.
532  *      @kobj:  object.
533  *      @attr:  attribute descriptor.
534  */
535 int sysfs_create_bin_file(struct kobject *kobj,
536                           const struct bin_attribute *attr)
537 {
538         kuid_t uid;
539         kgid_t gid;
540 
541         if (WARN_ON(!kobj || !kobj->sd || !attr))
542                 return -EINVAL;
543 
544         kobject_get_ownership(kobj, &uid, &gid);
545         return sysfs_add_file_mode_ns(kobj->sd, &attr->attr, true,
546                                       attr->attr.mode, uid, gid, NULL);
547 }
548 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
549 
550 /**
551  *      sysfs_remove_bin_file - remove binary file for object.
552  *      @kobj:  object.
553  *      @attr:  attribute descriptor.
554  */
555 void sysfs_remove_bin_file(struct kobject *kobj,
556                            const struct bin_attribute *attr)
557 {
558         kernfs_remove_by_name(kobj->sd, attr->attr.name);
559 }
560 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
561 

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