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 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
 377 {
 378         int i;
 379         for (i = 0; ptr[i]; i++)
 380                 sysfs_remove_file(kobj, ptr[i]);
 381 }
 382 EXPORT_SYMBOL_GPL(sysfs_remove_files);
 383
 384 /**
 385  * sysfs_remove_file_from_group - remove an attribute file from a group.
 386  * @kobj: object we're acting for.
 387  * @attr: attribute descriptor.
 388  * @group: group name.
 389  */
 390 void sysfs_remove_file_from_group(struct kobject *kobj,
 391                 const struct attribute *attr, const char *group)
 392 {
 393         struct kernfs_node *parent;
 394
 395         if (group) {
 396                 parent = kernfs_find_and_get(kobj->sd, group);
 397         } else {
 398                 parent = kobj->sd;
 399                 kernfs_get(parent);
 400         }
 401
 402         if (parent) {
 403                 kernfs_remove_by_name(parent, attr->name);
 404                 kernfs_put(parent);
 405         }
 406 }
 407 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 408
 409 /**
 410  *      sysfs_create_bin_file - create binary file for object.
 411  *      @kobj:  object.
 412  *      @attr:  attribute descriptor.
 413  */
 414 int sysfs_create_bin_file(struct kobject *kobj,
 415                           const struct bin_attribute *attr)
 416 {
 417         BUG_ON(!kobj || !kobj->sd || !attr);
 418
 419         return sysfs_add_file(kobj->sd, &attr->attr, true);
 420 }
 421 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
 422
 423 /**
 424  *      sysfs_remove_bin_file - remove binary file for object.
 425  *      @kobj:  object.
 426  *      @attr:  attribute descriptor.
 427  */
 428 void sysfs_remove_bin_file(struct kobject *kobj,
 429                            const struct bin_attribute *attr)
 430 {
 431         kernfs_remove_by_name(kobj->sd, attr->attr.name);
 432 }
 433 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
 434
 435 struct sysfs_schedule_callback_struct {
 436         struct list_head        workq_list;
 437         struct kobject          *kobj;
 438         void                    (*func)(void *);
 439         void                    *data;
 440         struct module           *owner;
 441         struct work_struct      work;
 442 };
 443
 444 static struct workqueue_struct *sysfs_workqueue;
 445 static DEFINE_MUTEX(sysfs_workq_mutex);
 446 static LIST_HEAD(sysfs_workq);
 447 static void sysfs_schedule_callback_work(struct work_struct *work)
 448 {
 449         struct sysfs_schedule_callback_struct *ss = container_of(work,
 450                         struct sysfs_schedule_callback_struct, work);
 451
 452         (ss->func)(ss->data);
 453         kobject_put(ss->kobj);
 454         module_put(ss->owner);
 455         mutex_lock(&sysfs_workq_mutex);
 456         list_del(&ss->workq_list);
 457         mutex_unlock(&sysfs_workq_mutex);
 458         kfree(ss);
 459 }
 460
 461 /**
 462  * sysfs_schedule_callback - helper to schedule a callback for a kobject
 463  * @kobj: object we're acting for.
 464  * @func: callback function to invoke later.
 465  * @data: argument to pass to @func.
 466  * @owner: module owning the callback code
 467  *
 468  * sysfs attribute methods must not unregister themselves or their parent
 469  * kobject (which would amount to the same thing).  Attempts to do so will
 470  * deadlock, since unregistration is mutually exclusive with driver
 471  * callbacks.
 472  *
 473  * Instead methods can call this routine, which will attempt to allocate
 474  * and schedule a workqueue request to call back @func with @data as its
 475  * argument in the workqueue's process context.  @kobj will be pinned
 476  * until @func returns.
 477  *
 478  * Returns 0 if the request was submitted, -ENOMEM if storage could not
 479  * be allocated, -ENODEV if a reference to @owner isn't available,
 480  * -EAGAIN if a callback has already been scheduled for @kobj.
 481  */
 482 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
 483                 void *data, struct module *owner)
 484 {
 485         struct sysfs_schedule_callback_struct *ss, *tmp;
 486
 487         if (!try_module_get(owner))
 488                 return -ENODEV;
 489
 490         mutex_lock(&sysfs_workq_mutex);
 491         list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
 492                 if (ss->kobj == kobj) {
 493                         module_put(owner);
 494                         mutex_unlock(&sysfs_workq_mutex);
 495                         return -EAGAIN;
 496                 }
 497         mutex_unlock(&sysfs_workq_mutex);
 498
 499         if (sysfs_workqueue == NULL) {
 500                 sysfs_workqueue = create_singlethread_workqueue("sysfsd");
 501                 if (sysfs_workqueue == NULL) {
 502                         module_put(owner);
 503                         return -ENOMEM;
 504                 }
 505         }
 506
 507         ss = kmalloc(sizeof(*ss), GFP_KERNEL);
 508         if (!ss) {
 509                 module_put(owner);
 510                 return -ENOMEM;
 511         }
 512         kobject_get(kobj);
 513         ss->kobj = kobj;
 514         ss->func = func;
 515         ss->data = data;
 516         ss->owner = owner;
 517         INIT_WORK(&ss->work, sysfs_schedule_callback_work);
 518         INIT_LIST_HEAD(&ss->workq_list);
 519         mutex_lock(&sysfs_workq_mutex);
 520         list_add_tail(&ss->workq_list, &sysfs_workq);
 521         mutex_unlock(&sysfs_workq_mutex);
 522         queue_work(sysfs_workqueue, &ss->work);
 523         return 0;
 524 }
 525 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);