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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 */
 51         count = seq_get_buf(sf, &buf);
 52         if (count < PAGE_SIZE) {
 53                 seq_commit(sf, -1);
 54                 return 0;
 55         }
 56 
 57         /*
 58          * Invoke show().  Control may reach here via seq file lseek even
 59          * if @ops->show() isn't implemented.
 60          */
 61         if (ops->show) {
 62                 count = ops->show(kobj, of->kn->priv, buf);
 63                 if (count < 0)
 64                         return count;
 65         }
 66 
 67         /*
 68          * The code works fine with PAGE_SIZE return but it's likely to
 69          * indicate truncated result or overflow in normal use cases.
 70          */
 71         if (count >= (ssize_t)PAGE_SIZE) {
 72                 print_symbol("fill_read_buffer: %s returned bad count\n",
 73                         (unsigned long)ops->show);
 74                 /* Try to struggle along */
 75                 count = PAGE_SIZE - 1;
 76         }
 77         seq_commit(sf, count);
 78         return 0;
 79 }
 80 
 81 static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
 82                                  size_t count, loff_t pos)
 83 {
 84         struct bin_attribute *battr = of->kn->priv;
 85         struct kobject *kobj = of->kn->parent->priv;
 86         loff_t size = file_inode(of->file)->i_size;
 87 
 88         if (!count)
 89                 return 0;
 90 
 91         if (size) {
 92                 if (pos > size)
 93                         return 0;
 94                 if (pos + count > size)
 95                         count = size - pos;
 96         }
 97 
 98         if (!battr->read)
 99                 return -EIO;
100 
101         return battr->read(of->file, kobj, battr, buf, pos, count);
102 }
103 
104 /* kernfs write callback for regular sysfs files */
105 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
106                               size_t count, loff_t pos)
107 {
108         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
109         struct kobject *kobj = of->kn->parent->priv;
110 
111         if (!count)
112                 return 0;
113 
114         return ops->store(kobj, of->kn->priv, buf, count);
115 }
116 
117 /* kernfs write callback for bin sysfs files */
118 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
119                                   size_t count, loff_t pos)
120 {
121         struct bin_attribute *battr = of->kn->priv;
122         struct kobject *kobj = of->kn->parent->priv;
123         loff_t size = file_inode(of->file)->i_size;
124 
125         if (size) {
126                 if (size <= pos)
127                         return 0;
128                 count = min_t(ssize_t, count, size - pos);
129         }
130         if (!count)
131                 return 0;
132 
133         if (!battr->write)
134                 return -EIO;
135 
136         return battr->write(of->file, kobj, battr, buf, pos, count);
137 }
138 
139 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
140                              struct vm_area_struct *vma)
141 {
142         struct bin_attribute *battr = of->kn->priv;
143         struct kobject *kobj = of->kn->parent->priv;
144 
145         return battr->mmap(of->file, kobj, battr, vma);
146 }
147 
148 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
149 {
150         struct kernfs_node *kn = kobj->sd, *tmp;
151 
152         if (kn && dir)
153                 kn = kernfs_find_and_get(kn, dir);
154         else
155                 kernfs_get(kn);
156 
157         if (kn && attr) {
158                 tmp = kernfs_find_and_get(kn, attr);
159                 kernfs_put(kn);
160                 kn = tmp;
161         }
162 
163         if (kn) {
164                 kernfs_notify(kn);
165                 kernfs_put(kn);
166         }
167 }
168 EXPORT_SYMBOL_GPL(sysfs_notify);
169 
170 static const struct kernfs_ops sysfs_file_kfops_empty = {
171 };
172 
173 static const struct kernfs_ops sysfs_file_kfops_ro = {
174         .seq_show       = sysfs_kf_seq_show,
175 };
176 
177 static const struct kernfs_ops sysfs_file_kfops_wo = {
178         .write          = sysfs_kf_write,
179 };
180 
181 static const struct kernfs_ops sysfs_file_kfops_rw = {
182         .seq_show       = sysfs_kf_seq_show,
183         .write          = sysfs_kf_write,
184 };
185 
186 static const struct kernfs_ops sysfs_bin_kfops_ro = {
187         .read           = sysfs_kf_bin_read,
188 };
189 
190 static const struct kernfs_ops sysfs_bin_kfops_wo = {
191         .write          = sysfs_kf_bin_write,
192 };
193 
194 static const struct kernfs_ops sysfs_bin_kfops_rw = {
195         .read           = sysfs_kf_bin_read,
196         .write          = sysfs_kf_bin_write,
197 };
198 
199 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
200         .read           = sysfs_kf_bin_read,
201         .write          = sysfs_kf_bin_write,
202         .mmap           = sysfs_kf_bin_mmap,
203 };
204 
205 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
206                            const struct attribute *attr, bool is_bin,
207                            umode_t mode, const void *ns)
208 {
209         struct lock_class_key *key = NULL;
210         const struct kernfs_ops *ops;
211         struct kernfs_node *kn;
212         loff_t size;
213 
214         if (!is_bin) {
215                 struct kobject *kobj = parent->priv;
216                 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
217 
218                 /* every kobject with an attribute needs a ktype assigned */
219                 if (WARN(!sysfs_ops, KERN_ERR
220                          "missing sysfs attribute operations for kobject: %s\n",
221                          kobject_name(kobj)))
222                         return -EINVAL;
223 
224                 if (sysfs_ops->show && sysfs_ops->store)
225                         ops = &sysfs_file_kfops_rw;
226                 else if (sysfs_ops->show)
227                         ops = &sysfs_file_kfops_ro;
228                 else if (sysfs_ops->store)
229                         ops = &sysfs_file_kfops_wo;
230                 else
231                         ops = &sysfs_file_kfops_empty;
232 
233                 size = PAGE_SIZE;
234         } else {
235                 struct bin_attribute *battr = (void *)attr;
236 
237                 if (battr->mmap)
238                         ops = &sysfs_bin_kfops_mmap;
239                 else if (battr->read && battr->write)
240                         ops = &sysfs_bin_kfops_rw;
241                 else if (battr->read)
242                         ops = &sysfs_bin_kfops_ro;
243                 else if (battr->write)
244                         ops = &sysfs_bin_kfops_wo;
245                 else
246                         ops = &sysfs_file_kfops_empty;
247 
248                 size = battr->size;
249         }
250 
251 #ifdef CONFIG_DEBUG_LOCK_ALLOC
252         if (!attr->ignore_lockdep)
253                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
254 #endif
255         kn = __kernfs_create_file(parent, attr->name, mode, size, ops,
256                                   (void *)attr, ns, true, key);
257         if (IS_ERR(kn)) {
258                 if (PTR_ERR(kn) == -EEXIST)
259                         sysfs_warn_dup(parent, attr->name);
260                 return PTR_ERR(kn);
261         }
262         return 0;
263 }
264 
265 int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
266                    bool is_bin)
267 {
268         return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
269 }
270 
271 /**
272  * sysfs_create_file_ns - create an attribute file for an object with custom ns
273  * @kobj: object we're creating for
274  * @attr: attribute descriptor
275  * @ns: namespace the new file should belong to
276  */
277 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
278                          const void *ns)
279 {
280         BUG_ON(!kobj || !kobj->sd || !attr);
281 
282         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
283 
284 }
285 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
286 
287 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
288 {
289         int err = 0;
290         int i;
291 
292         for (i = 0; ptr[i] && !err; i++)
293                 err = sysfs_create_file(kobj, ptr[i]);
294         if (err)
295                 while (--i >= 0)
296                         sysfs_remove_file(kobj, ptr[i]);
297         return err;
298 }
299 EXPORT_SYMBOL_GPL(sysfs_create_files);
300 
301 /**
302  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
303  * @kobj: object we're acting for.
304  * @attr: attribute descriptor.
305  * @group: group name.
306  */
307 int sysfs_add_file_to_group(struct kobject *kobj,
308                 const struct attribute *attr, const char *group)
309 {
310         struct kernfs_node *parent;
311         int error;
312 
313         if (group) {
314                 parent = kernfs_find_and_get(kobj->sd, group);
315         } else {
316                 parent = kobj->sd;
317                 kernfs_get(parent);
318         }
319 
320         if (!parent)
321                 return -ENOENT;
322 
323         error = sysfs_add_file(parent, attr, false);
324         kernfs_put(parent);
325 
326         return error;
327 }
328 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
329 
330 /**
331  * sysfs_chmod_file - update the modified mode value on an object attribute.
332  * @kobj: object we're acting for.
333  * @attr: attribute descriptor.
334  * @mode: file permissions.
335  *
336  */
337 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
338                      umode_t mode)
339 {
340         struct kernfs_node *kn;
341         struct iattr newattrs;
342         int rc;
343 
344         kn = kernfs_find_and_get(kobj->sd, attr->name);
345         if (!kn)
346                 return -ENOENT;
347 
348         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
349         newattrs.ia_valid = ATTR_MODE;
350 
351         rc = kernfs_setattr(kn, &newattrs);
352 
353         kernfs_put(kn);
354         return rc;
355 }
356 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
357 
358 /**
359  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
360  * @kobj: object we're acting for
361  * @attr: attribute descriptor
362  * @ns: namespace tag of the file to remove
363  *
364  * Hash the attribute name and namespace tag and kill the victim.
365  */
366 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
367                           const void *ns)
368 {
369         struct kernfs_node *parent = kobj->sd;
370 
371         kernfs_remove_by_name_ns(parent, attr->name, ns);
372 }
373 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
374 
375 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
376 {
377         int i;
378         for (i = 0; ptr[i]; i++)
379                 sysfs_remove_file(kobj, ptr[i]);
380 }
381 EXPORT_SYMBOL_GPL(sysfs_remove_files);
382 
383 /**
384  * sysfs_remove_file_from_group - remove an attribute file from a group.
385  * @kobj: object we're acting for.
386  * @attr: attribute descriptor.
387  * @group: group name.
388  */
389 void sysfs_remove_file_from_group(struct kobject *kobj,
390                 const struct attribute *attr, const char *group)
391 {
392         struct kernfs_node *parent;
393 
394         if (group) {
395                 parent = kernfs_find_and_get(kobj->sd, group);
396         } else {
397                 parent = kobj->sd;
398                 kernfs_get(parent);
399         }
400 
401         if (parent) {
402                 kernfs_remove_by_name(parent, attr->name);
403                 kernfs_put(parent);
404         }
405 }
406 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
407 
408 /**
409  *      sysfs_create_bin_file - create binary file for object.
410  *      @kobj:  object.
411  *      @attr:  attribute descriptor.
412  */
413 int sysfs_create_bin_file(struct kobject *kobj,
414                           const struct bin_attribute *attr)
415 {
416         BUG_ON(!kobj || !kobj->sd || !attr);
417 
418         return sysfs_add_file(kobj->sd, &attr->attr, true);
419 }
420 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
421 
422 /**
423  *      sysfs_remove_bin_file - remove binary file for object.
424  *      @kobj:  object.
425  *      @attr:  attribute descriptor.
426  */
427 void sysfs_remove_bin_file(struct kobject *kobj,
428                            const struct bin_attribute *attr)
429 {
430         kernfs_remove_by_name(kobj->sd, attr->attr.name);
431 }
432 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
433 
434 struct sysfs_schedule_callback_struct {
435         struct list_head        workq_list;
436         struct kobject          *kobj;
437         void                    (*func)(void *);
438         void                    *data;
439         struct module           *owner;
440         struct work_struct      work;
441 };
442 
443 static struct workqueue_struct *sysfs_workqueue;
444 static DEFINE_MUTEX(sysfs_workq_mutex);
445 static LIST_HEAD(sysfs_workq);
446 static void sysfs_schedule_callback_work(struct work_struct *work)
447 {
448         struct sysfs_schedule_callback_struct *ss = container_of(work,
449                         struct sysfs_schedule_callback_struct, work);
450 
451         (ss->func)(ss->data);
452         kobject_put(ss->kobj);
453         module_put(ss->owner);
454         mutex_lock(&sysfs_workq_mutex);
455         list_del(&ss->workq_list);
456         mutex_unlock(&sysfs_workq_mutex);
457         kfree(ss);
458 }
459 
460 /**
461  * sysfs_schedule_callback - helper to schedule a callback for a kobject
462  * @kobj: object we're acting for.
463  * @func: callback function to invoke later.
464  * @data: argument to pass to @func.
465  * @owner: module owning the callback code
466  *
467  * sysfs attribute methods must not unregister themselves or their parent
468  * kobject (which would amount to the same thing).  Attempts to do so will
469  * deadlock, since unregistration is mutually exclusive with driver
470  * callbacks.
471  *
472  * Instead methods can call this routine, which will attempt to allocate
473  * and schedule a workqueue request to call back @func with @data as its
474  * argument in the workqueue's process context.  @kobj will be pinned
475  * until @func returns.
476  *
477  * Returns 0 if the request was submitted, -ENOMEM if storage could not
478  * be allocated, -ENODEV if a reference to @owner isn't available,
479  * -EAGAIN if a callback has already been scheduled for @kobj.
480  */
481 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
482                 void *data, struct module *owner)
483 {
484         struct sysfs_schedule_callback_struct *ss, *tmp;
485 
486         if (!try_module_get(owner))
487                 return -ENODEV;
488 
489         mutex_lock(&sysfs_workq_mutex);
490         list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
491                 if (ss->kobj == kobj) {
492                         module_put(owner);
493                         mutex_unlock(&sysfs_workq_mutex);
494                         return -EAGAIN;
495                 }
496         mutex_unlock(&sysfs_workq_mutex);
497 
498         if (sysfs_workqueue == NULL) {
499                 sysfs_workqueue = create_singlethread_workqueue("sysfsd");
500                 if (sysfs_workqueue == NULL) {
501                         module_put(owner);
502                         return -ENOMEM;
503                 }
504         }
505 
506         ss = kmalloc(sizeof(*ss), GFP_KERNEL);
507         if (!ss) {
508                 module_put(owner);
509                 return -ENOMEM;
510         }
511         kobject_get(kobj);
512         ss->kobj = kobj;
513         ss->func = func;
514         ss->data = data;
515         ss->owner = owner;
516         INIT_WORK(&ss->work, sysfs_schedule_callback_work);
517         INIT_LIST_HEAD(&ss->workq_list);
518         mutex_lock(&sysfs_workq_mutex);
519         list_add_tail(&ss->workq_list, &sysfs_workq);
520         mutex_unlock(&sysfs_workq_mutex);
521         queue_work(sysfs_workqueue, &ss->work);
522         return 0;
523 }
524 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
525 

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