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
 112         /*
 113          * If buf != of->prealloc_buf, we don't know how
 114          * large it is, so cannot safely pass it to ->show
 115          */
 116         if (pos || WARN_ON_ONCE(buf != of->prealloc_buf))
 117                 return 0;
 118         return ops->show(kobj, of->kn->priv, buf);
 119 }
 120
 121 /* kernfs write callback for regular sysfs files */
 122 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
 123                               size_t count, loff_t pos)
 124 {
 125         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 126         struct kobject *kobj = of->kn->parent->priv;
 127
 128         if (!count)
 129                 return 0;
 130
 131         return ops->store(kobj, of->kn->priv, buf, count);
 132 }
 133
 134 /* kernfs write callback for bin sysfs files */
 135 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
 136                                   size_t count, loff_t pos)
 137 {
 138         struct bin_attribute *battr = of->kn->priv;
 139         struct kobject *kobj = of->kn->parent->priv;
 140         loff_t size = file_inode(of->file)->i_size;
 141
 142         if (size) {
 143                 if (size <= pos)
 144                         return -EFBIG;
 145                 count = min_t(ssize_t, count, size - pos);
 146         }
 147         if (!count)
 148                 return 0;
 149
 150         if (!battr->write)
 151                 return -EIO;
 152
 153         return battr->write(of->file, kobj, battr, buf, pos, count);
 154 }
 155
 156 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
 157                              struct vm_area_struct *vma)
 158 {
 159         struct bin_attribute *battr = of->kn->priv;
 160         struct kobject *kobj = of->kn->parent->priv;
 161
 162         return battr->mmap(of->file, kobj, battr, vma);
 163 }
 164
 165 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
 166 {
 167         struct kernfs_node *kn = kobj->sd, *tmp;
 168
 169         if (kn && dir)
 170                 kn = kernfs_find_and_get(kn, dir);
 171         else
 172                 kernfs_get(kn);
 173
 174         if (kn && attr) {
 175                 tmp = kernfs_find_and_get(kn, attr);
 176                 kernfs_put(kn);
 177                 kn = tmp;
 178         }
 179
 180         if (kn) {
 181                 kernfs_notify(kn);
 182                 kernfs_put(kn);
 183         }
 184 }
 185 EXPORT_SYMBOL_GPL(sysfs_notify);
 186
 187 static const struct kernfs_ops sysfs_file_kfops_empty = {
 188 };
 189
 190 static const struct kernfs_ops sysfs_file_kfops_ro = {
 191         .seq_show       = sysfs_kf_seq_show,
 192 };
 193
 194 static const struct kernfs_ops sysfs_file_kfops_wo = {
 195         .write          = sysfs_kf_write,
 196 };
 197
 198 static const struct kernfs_ops sysfs_file_kfops_rw = {
 199         .seq_show       = sysfs_kf_seq_show,
 200         .write          = sysfs_kf_write,
 201 };
 202
 203 static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
 204         .read           = sysfs_kf_read,
 205         .prealloc       = true,
 206 };
 207
 208 static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
 209         .write          = sysfs_kf_write,
 210         .prealloc       = true,
 211 };
 212
 213 static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
 214         .read           = sysfs_kf_read,
 215         .write          = sysfs_kf_write,
 216         .prealloc       = true,
 217 };
 218
 219 static const struct kernfs_ops sysfs_bin_kfops_ro = {
 220         .read           = sysfs_kf_bin_read,
 221 };
 222
 223 static const struct kernfs_ops sysfs_bin_kfops_wo = {
 224         .write          = sysfs_kf_bin_write,
 225 };
 226
 227 static const struct kernfs_ops sysfs_bin_kfops_rw = {
 228         .read           = sysfs_kf_bin_read,
 229         .write          = sysfs_kf_bin_write,
 230 };
 231
 232 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
 233         .read           = sysfs_kf_bin_read,
 234         .write          = sysfs_kf_bin_write,
 235         .mmap           = sysfs_kf_bin_mmap,
 236 };
 237
 238 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
 239                            const struct attribute *attr, bool is_bin,
 240                            umode_t mode, const void *ns)
 241 {
 242         struct lock_class_key *key = NULL;
 243         const struct kernfs_ops *ops;
 244         struct kernfs_node *kn;
 245         loff_t size;
 246
 247         if (!is_bin) {
 248                 struct kobject *kobj = parent->priv;
 249                 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
 250
 251                 /* every kobject with an attribute needs a ktype assigned */
 252                 if (WARN(!sysfs_ops, KERN_ERR
 253                          "missing sysfs attribute operations for kobject: %s\n",
 254                          kobject_name(kobj)))
 255                         return -EINVAL;
 256
 257                 if (sysfs_ops->show && sysfs_ops->store) {
 258                         if (mode & SYSFS_PREALLOC)
 259                                 ops = &sysfs_prealloc_kfops_rw;
 260                         else
 261                                 ops = &sysfs_file_kfops_rw;
 262                 } else if (sysfs_ops->show) {
 263                         if (mode & SYSFS_PREALLOC)
 264                                 ops = &sysfs_prealloc_kfops_ro;
 265                         else
 266                                 ops = &sysfs_file_kfops_ro;
 267                 } else if (sysfs_ops->store) {
 268                         if (mode & SYSFS_PREALLOC)
 269                                 ops = &sysfs_prealloc_kfops_wo;
 270                         else
 271                                 ops = &sysfs_file_kfops_wo;
 272                 } else
 273                         ops = &sysfs_file_kfops_empty;
 274
 275                 size = PAGE_SIZE;
 276         } else {
 277                 struct bin_attribute *battr = (void *)attr;
 278
 279                 if (battr->mmap)
 280                         ops = &sysfs_bin_kfops_mmap;
 281                 else if (battr->read && battr->write)
 282                         ops = &sysfs_bin_kfops_rw;
 283                 else if (battr->read)
 284                         ops = &sysfs_bin_kfops_ro;
 285                 else if (battr->write)
 286                         ops = &sysfs_bin_kfops_wo;
 287                 else
 288                         ops = &sysfs_file_kfops_empty;
 289
 290                 size = battr->size;
 291         }
 292
 293 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 294         if (!attr->ignore_lockdep)
 295                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
 296 #endif
 297         kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
 298                                   (void *)attr, ns, key);
 299         if (IS_ERR(kn)) {
 300                 if (PTR_ERR(kn) == -EEXIST)
 301                         sysfs_warn_dup(parent, attr->name);
 302                 return PTR_ERR(kn);
 303         }
 304         return 0;
 305 }
 306
 307 int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
 308                    bool is_bin)
 309 {
 310         return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
 311 }
 312
 313 /**
 314  * sysfs_create_file_ns - create an attribute file for an object with custom ns
 315  * @kobj: object we're creating for
 316  * @attr: attribute descriptor
 317  * @ns: namespace the new file should belong to
 318  */
 319 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
 320                          const void *ns)
 321 {
 322         BUG_ON(!kobj || !kobj->sd || !attr);
 323
 324         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
 325
 326 }
 327 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
 328
 329 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
 330 {
 331         int err = 0;
 332         int i;
 333
 334         for (i = 0; ptr[i] && !err; i++)
 335                 err = sysfs_create_file(kobj, ptr[i]);
 336         if (err)
 337                 while (--i >= 0)
 338                         sysfs_remove_file(kobj, ptr[i]);
 339         return err;
 340 }
 341 EXPORT_SYMBOL_GPL(sysfs_create_files);
 342
 343 /**
 344  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 345  * @kobj: object we're acting for.
 346  * @attr: attribute descriptor.
 347  * @group: group name.
 348  */
 349 int sysfs_add_file_to_group(struct kobject *kobj,
 350                 const struct attribute *attr, const char *group)
 351 {
 352         struct kernfs_node *parent;
 353         int error;
 354
 355         if (group) {
 356                 parent = kernfs_find_and_get(kobj->sd, group);
 357         } else {
 358                 parent = kobj->sd;
 359                 kernfs_get(parent);
 360         }
 361
 362         if (!parent)
 363                 return -ENOENT;
 364
 365         error = sysfs_add_file(parent, attr, false);
 366         kernfs_put(parent);
 367
 368         return error;
 369 }
 370 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 371
 372 /**
 373  * sysfs_chmod_file - update the modified mode value on an object attribute.
 374  * @kobj: object we're acting for.
 375  * @attr: attribute descriptor.
 376  * @mode: file permissions.
 377  *
 378  */
 379 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
 380                      umode_t mode)
 381 {
 382         struct kernfs_node *kn;
 383         struct iattr newattrs;
 384         int rc;
 385
 386         kn = kernfs_find_and_get(kobj->sd, attr->name);
 387         if (!kn)
 388                 return -ENOENT;
 389
 390         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
 391         newattrs.ia_valid = ATTR_MODE;
 392
 393         rc = kernfs_setattr(kn, &newattrs);
 394
 395         kernfs_put(kn);
 396         return rc;
 397 }
 398 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 399
 400 /**
 401  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
 402  * @kobj: object we're acting for
 403  * @attr: attribute descriptor
 404  * @ns: namespace tag of the file to remove
 405  *
 406  * Hash the attribute name and namespace tag and kill the victim.
 407  */
 408 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
 409                           const void *ns)
 410 {
 411         struct kernfs_node *parent = kobj->sd;
 412
 413         kernfs_remove_by_name_ns(parent, attr->name, ns);
 414 }
 415 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
 416
 417 /**
 418  * sysfs_remove_file_self - remove an object attribute from its own method
 419  * @kobj: object we're acting for
 420  * @attr: attribute descriptor
 421  *
 422  * See kernfs_remove_self() for details.
 423  */
 424 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
 425 {
 426         struct kernfs_node *parent = kobj->sd;
 427         struct kernfs_node *kn;
 428         bool ret;
 429
 430         kn = kernfs_find_and_get(parent, attr->name);
 431         if (WARN_ON_ONCE(!kn))
 432                 return false;
 433
 434         ret = kernfs_remove_self(kn);
 435
 436         kernfs_put(kn);
 437         return ret;
 438 }
 439
 440 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
 441 {
 442         int i;
 443         for (i = 0; ptr[i]; i++)
 444                 sysfs_remove_file(kobj, ptr[i]);
 445 }
 446 EXPORT_SYMBOL_GPL(sysfs_remove_files);
 447
 448 /**
 449  * sysfs_remove_file_from_group - remove an attribute file from a group.
 450  * @kobj: object we're acting for.
 451  * @attr: attribute descriptor.
 452  * @group: group name.
 453  */
 454 void sysfs_remove_file_from_group(struct kobject *kobj,
 455                 const struct attribute *attr, const char *group)
 456 {
 457         struct kernfs_node *parent;
 458
 459         if (group) {
 460                 parent = kernfs_find_and_get(kobj->sd, group);
 461         } else {
 462                 parent = kobj->sd;
 463                 kernfs_get(parent);
 464         }
 465
 466         if (parent) {
 467                 kernfs_remove_by_name(parent, attr->name);
 468                 kernfs_put(parent);
 469         }
 470 }
 471 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 472
 473 /**
 474  *      sysfs_create_bin_file - create binary file for object.
 475  *      @kobj:  object.
 476  *      @attr:  attribute descriptor.
 477  */
 478 int sysfs_create_bin_file(struct kobject *kobj,
 479                           const struct bin_attribute *attr)
 480 {
 481         BUG_ON(!kobj || !kobj->sd || !attr);
 482
 483         return sysfs_add_file(kobj->sd, &attr->attr, true);
 484 }
 485 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
 486
 487 /**
 488  *      sysfs_remove_bin_file - remove binary file for object.
 489  *      @kobj:  object.
 490  *      @attr:  attribute descriptor.
 491  */
 492 void sysfs_remove_bin_file(struct kobject *kobj,
 493                            const struct bin_attribute *attr)
 494 {
 495         kernfs_remove_by_name(kobj->sd, attr->attr.name);
 496 }
 497 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);