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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 (pos || WARN_ON_ONCE(buf != of->prealloc_buf))
118                 return 0;
119         len = ops->show(kobj, of->kn->priv, buf);
120         return min(count, len);
121 }
122 
123 /* kernfs write callback for regular sysfs files */
124 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
125                               size_t count, loff_t pos)
126 {
127         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
128         struct kobject *kobj = of->kn->parent->priv;
129 
130         if (!count)
131                 return 0;
132 
133         return ops->store(kobj, of->kn->priv, buf, count);
134 }
135 
136 /* kernfs write callback for bin sysfs files */
137 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
138                                   size_t count, loff_t pos)
139 {
140         struct bin_attribute *battr = of->kn->priv;
141         struct kobject *kobj = of->kn->parent->priv;
142         loff_t size = file_inode(of->file)->i_size;
143 
144         if (size) {
145                 if (size <= pos)
146                         return -EFBIG;
147                 count = min_t(ssize_t, count, size - pos);
148         }
149         if (!count)
150                 return 0;
151 
152         if (!battr->write)
153                 return -EIO;
154 
155         return battr->write(of->file, kobj, battr, buf, pos, count);
156 }
157 
158 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
159                              struct vm_area_struct *vma)
160 {
161         struct bin_attribute *battr = of->kn->priv;
162         struct kobject *kobj = of->kn->parent->priv;
163 
164         return battr->mmap(of->file, kobj, battr, vma);
165 }
166 
167 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
168 {
169         struct kernfs_node *kn = kobj->sd, *tmp;
170 
171         if (kn && dir)
172                 kn = kernfs_find_and_get(kn, dir);
173         else
174                 kernfs_get(kn);
175 
176         if (kn && attr) {
177                 tmp = kernfs_find_and_get(kn, attr);
178                 kernfs_put(kn);
179                 kn = tmp;
180         }
181 
182         if (kn) {
183                 kernfs_notify(kn);
184                 kernfs_put(kn);
185         }
186 }
187 EXPORT_SYMBOL_GPL(sysfs_notify);
188 
189 static const struct kernfs_ops sysfs_file_kfops_empty = {
190 };
191 
192 static const struct kernfs_ops sysfs_file_kfops_ro = {
193         .seq_show       = sysfs_kf_seq_show,
194 };
195 
196 static const struct kernfs_ops sysfs_file_kfops_wo = {
197         .write          = sysfs_kf_write,
198 };
199 
200 static const struct kernfs_ops sysfs_file_kfops_rw = {
201         .seq_show       = sysfs_kf_seq_show,
202         .write          = sysfs_kf_write,
203 };
204 
205 static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
206         .read           = sysfs_kf_read,
207         .prealloc       = true,
208 };
209 
210 static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
211         .write          = sysfs_kf_write,
212         .prealloc       = true,
213 };
214 
215 static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
216         .read           = sysfs_kf_read,
217         .write          = sysfs_kf_write,
218         .prealloc       = true,
219 };
220 
221 static const struct kernfs_ops sysfs_bin_kfops_ro = {
222         .read           = sysfs_kf_bin_read,
223 };
224 
225 static const struct kernfs_ops sysfs_bin_kfops_wo = {
226         .write          = sysfs_kf_bin_write,
227 };
228 
229 static const struct kernfs_ops sysfs_bin_kfops_rw = {
230         .read           = sysfs_kf_bin_read,
231         .write          = sysfs_kf_bin_write,
232 };
233 
234 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
235         .read           = sysfs_kf_bin_read,
236         .write          = sysfs_kf_bin_write,
237         .mmap           = sysfs_kf_bin_mmap,
238 };
239 
240 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
241                            const struct attribute *attr, bool is_bin,
242                            umode_t mode, const void *ns)
243 {
244         struct lock_class_key *key = NULL;
245         const struct kernfs_ops *ops;
246         struct kernfs_node *kn;
247         loff_t size;
248 
249         if (!is_bin) {
250                 struct kobject *kobj = parent->priv;
251                 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
252 
253                 /* every kobject with an attribute needs a ktype assigned */
254                 if (WARN(!sysfs_ops, KERN_ERR
255                          "missing sysfs attribute operations for kobject: %s\n",
256                          kobject_name(kobj)))
257                         return -EINVAL;
258 
259                 if (sysfs_ops->show && sysfs_ops->store) {
260                         if (mode & SYSFS_PREALLOC)
261                                 ops = &sysfs_prealloc_kfops_rw;
262                         else
263                                 ops = &sysfs_file_kfops_rw;
264                 } else if (sysfs_ops->show) {
265                         if (mode & SYSFS_PREALLOC)
266                                 ops = &sysfs_prealloc_kfops_ro;
267                         else
268                                 ops = &sysfs_file_kfops_ro;
269                 } else if (sysfs_ops->store) {
270                         if (mode & SYSFS_PREALLOC)
271                                 ops = &sysfs_prealloc_kfops_wo;
272                         else
273                                 ops = &sysfs_file_kfops_wo;
274                 } else
275                         ops = &sysfs_file_kfops_empty;
276 
277                 size = PAGE_SIZE;
278         } else {
279                 struct bin_attribute *battr = (void *)attr;
280 
281                 if (battr->mmap)
282                         ops = &sysfs_bin_kfops_mmap;
283                 else if (battr->read && battr->write)
284                         ops = &sysfs_bin_kfops_rw;
285                 else if (battr->read)
286                         ops = &sysfs_bin_kfops_ro;
287                 else if (battr->write)
288                         ops = &sysfs_bin_kfops_wo;
289                 else
290                         ops = &sysfs_file_kfops_empty;
291 
292                 size = battr->size;
293         }
294 
295 #ifdef CONFIG_DEBUG_LOCK_ALLOC
296         if (!attr->ignore_lockdep)
297                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
298 #endif
299         kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
300                                   (void *)attr, ns, key);
301         if (IS_ERR(kn)) {
302                 if (PTR_ERR(kn) == -EEXIST)
303                         sysfs_warn_dup(parent, attr->name);
304                 return PTR_ERR(kn);
305         }
306         return 0;
307 }
308 
309 int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
310                    bool is_bin)
311 {
312         return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
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         BUG_ON(!kobj || !kobj->sd || !attr);
325 
326         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
327 
328 }
329 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
330 
331 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
332 {
333         int err = 0;
334         int i;
335 
336         for (i = 0; ptr[i] && !err; i++)
337                 err = sysfs_create_file(kobj, ptr[i]);
338         if (err)
339                 while (--i >= 0)
340                         sysfs_remove_file(kobj, ptr[i]);
341         return err;
342 }
343 EXPORT_SYMBOL_GPL(sysfs_create_files);
344 
345 /**
346  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
347  * @kobj: object we're acting for.
348  * @attr: attribute descriptor.
349  * @group: group name.
350  */
351 int sysfs_add_file_to_group(struct kobject *kobj,
352                 const struct attribute *attr, const char *group)
353 {
354         struct kernfs_node *parent;
355         int error;
356 
357         if (group) {
358                 parent = kernfs_find_and_get(kobj->sd, group);
359         } else {
360                 parent = kobj->sd;
361                 kernfs_get(parent);
362         }
363 
364         if (!parent)
365                 return -ENOENT;
366 
367         error = sysfs_add_file(parent, attr, false);
368         kernfs_put(parent);
369 
370         return error;
371 }
372 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
373 
374 /**
375  * sysfs_chmod_file - update the modified mode value on an object attribute.
376  * @kobj: object we're acting for.
377  * @attr: attribute descriptor.
378  * @mode: file permissions.
379  *
380  */
381 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
382                      umode_t mode)
383 {
384         struct kernfs_node *kn;
385         struct iattr newattrs;
386         int rc;
387 
388         kn = kernfs_find_and_get(kobj->sd, attr->name);
389         if (!kn)
390                 return -ENOENT;
391 
392         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
393         newattrs.ia_valid = ATTR_MODE;
394 
395         rc = kernfs_setattr(kn, &newattrs);
396 
397         kernfs_put(kn);
398         return rc;
399 }
400 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
401 
402 /**
403  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
404  * @kobj: object we're acting for
405  * @attr: attribute descriptor
406  * @ns: namespace tag of the file to remove
407  *
408  * Hash the attribute name and namespace tag and kill the victim.
409  */
410 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
411                           const void *ns)
412 {
413         struct kernfs_node *parent = kobj->sd;
414 
415         kernfs_remove_by_name_ns(parent, attr->name, ns);
416 }
417 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
418 
419 /**
420  * sysfs_remove_file_self - remove an object attribute from its own method
421  * @kobj: object we're acting for
422  * @attr: attribute descriptor
423  *
424  * See kernfs_remove_self() for details.
425  */
426 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
427 {
428         struct kernfs_node *parent = kobj->sd;
429         struct kernfs_node *kn;
430         bool ret;
431 
432         kn = kernfs_find_and_get(parent, attr->name);
433         if (WARN_ON_ONCE(!kn))
434                 return false;
435 
436         ret = kernfs_remove_self(kn);
437 
438         kernfs_put(kn);
439         return ret;
440 }
441 
442 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
443 {
444         int i;
445         for (i = 0; ptr[i]; i++)
446                 sysfs_remove_file(kobj, ptr[i]);
447 }
448 EXPORT_SYMBOL_GPL(sysfs_remove_files);
449 
450 /**
451  * sysfs_remove_file_from_group - remove an attribute file from a group.
452  * @kobj: object we're acting for.
453  * @attr: attribute descriptor.
454  * @group: group name.
455  */
456 void sysfs_remove_file_from_group(struct kobject *kobj,
457                 const struct attribute *attr, const char *group)
458 {
459         struct kernfs_node *parent;
460 
461         if (group) {
462                 parent = kernfs_find_and_get(kobj->sd, group);
463         } else {
464                 parent = kobj->sd;
465                 kernfs_get(parent);
466         }
467 
468         if (parent) {
469                 kernfs_remove_by_name(parent, attr->name);
470                 kernfs_put(parent);
471         }
472 }
473 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
474 
475 /**
476  *      sysfs_create_bin_file - create binary file for object.
477  *      @kobj:  object.
478  *      @attr:  attribute descriptor.
479  */
480 int sysfs_create_bin_file(struct kobject *kobj,
481                           const struct bin_attribute *attr)
482 {
483         BUG_ON(!kobj || !kobj->sd || !attr);
484 
485         return sysfs_add_file(kobj->sd, &attr->attr, true);
486 }
487 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
488 
489 /**
490  *      sysfs_remove_bin_file - remove binary file for object.
491  *      @kobj:  object.
492  *      @attr:  attribute descriptor.
493  */
494 void sysfs_remove_bin_file(struct kobject *kobj,
495                            const struct bin_attribute *attr)
496 {
497         kernfs_remove_by_name(kobj->sd, attr->attr.name);
498 }
499 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
500 

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