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

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