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Linux/fs/sysfs/file.c

  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 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 
 82 static 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 */
106 static 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 (WARN_ON_ONCE(buf != of->prealloc_buf))
118                 return 0;
119         len = ops->show(kobj, of->kn->priv, buf);
120         if (pos) {
121                 if (len <= pos)
122                         return 0;
123                 len -= pos;
124                 memmove(buf, buf + pos, len);
125         }
126         return min(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, 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         kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
306                                   (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 int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
316                    bool is_bin)
317 {
318         return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
319 }
320 
321 /**
322  * sysfs_create_file_ns - create an attribute file for an object with custom ns
323  * @kobj: object we're creating for
324  * @attr: attribute descriptor
325  * @ns: namespace the new file should belong to
326  */
327 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
328                          const void *ns)
329 {
330         BUG_ON(!kobj || !kobj->sd || !attr);
331 
332         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
333 
334 }
335 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
336 
337 int sysfs_create_files(struct kobject *kobj, const struct attribute **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         int error;
362 
363         if (group) {
364                 parent = kernfs_find_and_get(kobj->sd, group);
365         } else {
366                 parent = kobj->sd;
367                 kernfs_get(parent);
368         }
369 
370         if (!parent)
371                 return -ENOENT;
372 
373         error = sysfs_add_file(parent, attr, false);
374         kernfs_put(parent);
375 
376         return error;
377 }
378 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
379 
380 /**
381  * sysfs_chmod_file - update the modified mode value on an object attribute.
382  * @kobj: object we're acting for.
383  * @attr: attribute descriptor.
384  * @mode: file permissions.
385  *
386  */
387 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
388                      umode_t mode)
389 {
390         struct kernfs_node *kn;
391         struct iattr newattrs;
392         int rc;
393 
394         kn = kernfs_find_and_get(kobj->sd, attr->name);
395         if (!kn)
396                 return -ENOENT;
397 
398         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
399         newattrs.ia_valid = ATTR_MODE;
400 
401         rc = kernfs_setattr(kn, &newattrs);
402 
403         kernfs_put(kn);
404         return rc;
405 }
406 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
407 
408 /**
409  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
410  * @kobj: object we're acting for
411  * @attr: attribute descriptor
412  * @ns: namespace tag of the file to remove
413  *
414  * Hash the attribute name and namespace tag and kill the victim.
415  */
416 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
417                           const void *ns)
418 {
419         struct kernfs_node *parent = kobj->sd;
420 
421         kernfs_remove_by_name_ns(parent, attr->name, ns);
422 }
423 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
424 
425 /**
426  * sysfs_remove_file_self - remove an object attribute from its own method
427  * @kobj: object we're acting for
428  * @attr: attribute descriptor
429  *
430  * See kernfs_remove_self() for details.
431  */
432 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
433 {
434         struct kernfs_node *parent = kobj->sd;
435         struct kernfs_node *kn;
436         bool ret;
437 
438         kn = kernfs_find_and_get(parent, attr->name);
439         if (WARN_ON_ONCE(!kn))
440                 return false;
441 
442         ret = kernfs_remove_self(kn);
443 
444         kernfs_put(kn);
445         return ret;
446 }
447 
448 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
449 {
450         int i;
451         for (i = 0; ptr[i]; i++)
452                 sysfs_remove_file(kobj, ptr[i]);
453 }
454 EXPORT_SYMBOL_GPL(sysfs_remove_files);
455 
456 /**
457  * sysfs_remove_file_from_group - remove an attribute file from a group.
458  * @kobj: object we're acting for.
459  * @attr: attribute descriptor.
460  * @group: group name.
461  */
462 void sysfs_remove_file_from_group(struct kobject *kobj,
463                 const struct attribute *attr, const char *group)
464 {
465         struct kernfs_node *parent;
466 
467         if (group) {
468                 parent = kernfs_find_and_get(kobj->sd, group);
469         } else {
470                 parent = kobj->sd;
471                 kernfs_get(parent);
472         }
473 
474         if (parent) {
475                 kernfs_remove_by_name(parent, attr->name);
476                 kernfs_put(parent);
477         }
478 }
479 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
480 
481 /**
482  *      sysfs_create_bin_file - create binary file for object.
483  *      @kobj:  object.
484  *      @attr:  attribute descriptor.
485  */
486 int sysfs_create_bin_file(struct kobject *kobj,
487                           const struct bin_attribute *attr)
488 {
489         BUG_ON(!kobj || !kobj->sd || !attr);
490 
491         return sysfs_add_file(kobj->sd, &attr->attr, true);
492 }
493 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
494 
495 /**
496  *      sysfs_remove_bin_file - remove binary file for object.
497  *      @kobj:  object.
498  *      @attr:  attribute descriptor.
499  */
500 void sysfs_remove_bin_file(struct kobject *kobj,
501                            const struct bin_attribute *attr)
502 {
503         kernfs_remove_by_name(kobj->sd, attr->attr.name);
504 }
505 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
506 

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