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);