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