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);