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

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