fs/sysfs/file.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * fs/sysfs/file.c - sysfs regular (text) file implementation
   4  *
   5  * Copyright (c) 2001-3 Patrick Mochel
   6  * Copyright (c) 2007 SUSE Linux Products GmbH
   7  * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   8  *
   9  * Please see Documentation/filesystems/sysfs.txt for more information.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/kobject.h>
  14 #include <linux/slab.h>
  15 #include <linux/list.h>
  16 #include <linux/mutex.h>
  17 #include <linux/seq_file.h>
  18
  19 #include "sysfs.h"
  20 #include "../kernfs/kernfs-internal.h"
  21
  22 /*
  23  * Determine ktype->sysfs_ops for the given kernfs_node.  This function
  24  * must be called while holding an active reference.
  25  */
  26 static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
  27 {
  28         struct kobject *kobj = kn->parent->priv;
  29
  30         if (kn->flags & KERNFS_LOCKDEP)
  31                 lockdep_assert_held(kn);
  32         return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
  33 }
  34
  35 /*
  36  * Reads on sysfs are handled through seq_file, which takes care of hairy
  37  * details like buffering and seeking.  The following function pipes
  38  * sysfs_ops->show() result through seq_file.
  39  */
  40 static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
  41 {
  42         struct kernfs_open_file *of = sf->private;
  43         struct kobject *kobj = of->kn->parent->priv;
  44         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
  45         ssize_t count;
  46         char *buf;
  47
  48         /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
  49         count = seq_get_buf(sf, &buf);
  50         if (count < PAGE_SIZE) {
  51                 seq_commit(sf, -1);
  52                 return 0;
  53         }
  54         memset(buf, 0, PAGE_SIZE);
  55
  56         /*
  57          * Invoke show().  Control may reach here via seq file lseek even
  58          * if @ops->show() isn't implemented.
  59          */
  60         if (ops->show) {
  61                 count = ops->show(kobj, of->kn->priv, buf);
  62                 if (count < 0)
  63                         return count;
  64         }
  65
  66         /*
  67          * The code works fine with PAGE_SIZE return but it's likely to
  68          * indicate truncated result or overflow in normal use cases.
  69          */
  70         if (count >= (ssize_t)PAGE_SIZE) {
  71                 printk("fill_read_buffer: %pS returned bad count\n",
  72                                 ops->show);
  73                 /* Try to struggle along */
  74                 count = PAGE_SIZE - 1;
  75         }
  76         seq_commit(sf, count);
  77         return 0;
  78 }
  79
  80 static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
  81                                  size_t count, loff_t pos)
  82 {
  83         struct bin_attribute *battr = of->kn->priv;
  84         struct kobject *kobj = of->kn->parent->priv;
  85         loff_t size = file_inode(of->file)->i_size;
  86
  87         if (!count)
  88                 return 0;
  89
  90         if (size) {
  91                 if (pos >= size)
  92                         return 0;
  93                 if (pos + count > size)
  94                         count = size - pos;
  95         }
  96
  97         if (!battr->read)
  98                 return -EIO;
  99
 100         return battr->read(of->file, kobj, battr, buf, pos, count);
 101 }
 102
 103 /* kernfs read callback for regular sysfs files with pre-alloc */
 104 static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
 105                              size_t count, loff_t pos)
 106 {
 107         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 108         struct kobject *kobj = of->kn->parent->priv;
 109         ssize_t len;
 110
 111         /*
 112          * If buf != of->prealloc_buf, we don't know how
 113          * large it is, so cannot safely pass it to ->show
 114          */
 115         if (WARN_ON_ONCE(buf != of->prealloc_buf))
 116                 return 0;
 117         len = ops->show(kobj, of->kn->priv, buf);
 118         if (len < 0)
 119                 return len;
 120         if (pos) {
 121                 if (len <= pos)
 122                         return 0;
 123                 len -= pos;
 124                 memmove(buf, buf + pos, len);
 125         }
 126         return min_t(ssize_t, count, len);
 127 }
 128
 129 /* kernfs write callback for regular sysfs files */
 130 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
 131                               size_t count, loff_t pos)
 132 {
 133         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 134         struct kobject *kobj = of->kn->parent->priv;
 135
 136         if (!count)
 137                 return 0;
 138
 139         return ops->store(kobj, of->kn->priv, buf, count);
 140 }
 141
 142 /* kernfs write callback for bin sysfs files */
 143 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
 144                                   size_t count, loff_t pos)
 145 {
 146         struct bin_attribute *battr = of->kn->priv;
 147         struct kobject *kobj = of->kn->parent->priv;
 148         loff_t size = file_inode(of->file)->i_size;
 149
 150         if (size) {
 151                 if (size <= pos)
 152                         return -EFBIG;
 153                 count = min_t(ssize_t, count, size - pos);
 154         }
 155         if (!count)
 156                 return 0;
 157
 158         if (!battr->write)
 159                 return -EIO;
 160
 161         return battr->write(of->file, kobj, battr, buf, pos, count);
 162 }
 163
 164 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
 165                              struct vm_area_struct *vma)
 166 {
 167         struct bin_attribute *battr = of->kn->priv;
 168         struct kobject *kobj = of->kn->parent->priv;
 169
 170         return battr->mmap(of->file, kobj, battr, vma);
 171 }
 172
 173 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
 174 {
 175         struct kernfs_node *kn = kobj->sd, *tmp;
 176
 177         if (kn && dir)
 178                 kn = kernfs_find_and_get(kn, dir);
 179         else
 180                 kernfs_get(kn);
 181
 182         if (kn && attr) {
 183                 tmp = kernfs_find_and_get(kn, attr);
 184                 kernfs_put(kn);
 185                 kn = tmp;
 186         }
 187
 188         if (kn) {
 189                 kernfs_notify(kn);
 190                 kernfs_put(kn);
 191         }
 192 }
 193 EXPORT_SYMBOL_GPL(sysfs_notify);
 194
 195 static const struct kernfs_ops sysfs_file_kfops_empty = {
 196 };
 197
 198 static const struct kernfs_ops sysfs_file_kfops_ro = {
 199         .seq_show       = sysfs_kf_seq_show,
 200 };
 201
 202 static const struct kernfs_ops sysfs_file_kfops_wo = {
 203         .write          = sysfs_kf_write,
 204 };
 205
 206 static const struct kernfs_ops sysfs_file_kfops_rw = {
 207         .seq_show       = sysfs_kf_seq_show,
 208         .write          = sysfs_kf_write,
 209 };
 210
 211 static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
 212         .read           = sysfs_kf_read,
 213         .prealloc       = true,
 214 };
 215
 216 static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
 217         .write          = sysfs_kf_write,
 218         .prealloc       = true,
 219 };
 220
 221 static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
 222         .read           = sysfs_kf_read,
 223         .write          = sysfs_kf_write,
 224         .prealloc       = true,
 225 };
 226
 227 static const struct kernfs_ops sysfs_bin_kfops_ro = {
 228         .read           = sysfs_kf_bin_read,
 229 };
 230
 231 static const struct kernfs_ops sysfs_bin_kfops_wo = {
 232         .write          = sysfs_kf_bin_write,
 233 };
 234
 235 static const struct kernfs_ops sysfs_bin_kfops_rw = {
 236         .read           = sysfs_kf_bin_read,
 237         .write          = sysfs_kf_bin_write,
 238 };
 239
 240 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
 241         .read           = sysfs_kf_bin_read,
 242         .write          = sysfs_kf_bin_write,
 243         .mmap           = sysfs_kf_bin_mmap,
 244 };
 245
 246 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
 247                            const struct attribute *attr, bool is_bin,
 248                            umode_t mode, const void *ns)
 249 {
 250         struct lock_class_key *key = NULL;
 251         const struct kernfs_ops *ops;
 252         struct kernfs_node *kn;
 253         loff_t size;
 254
 255         if (!is_bin) {
 256                 struct kobject *kobj = parent->priv;
 257                 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
 258
 259                 /* every kobject with an attribute needs a ktype assigned */
 260                 if (WARN(!sysfs_ops, KERN_ERR
 261                          "missing sysfs attribute operations for kobject: %s\n",
 262                          kobject_name(kobj)))
 263                         return -EINVAL;
 264
 265                 if (sysfs_ops->show && sysfs_ops->store) {
 266                         if (mode & SYSFS_PREALLOC)
 267                                 ops = &sysfs_prealloc_kfops_rw;
 268                         else
 269                                 ops = &sysfs_file_kfops_rw;
 270                 } else if (sysfs_ops->show) {
 271                         if (mode & SYSFS_PREALLOC)
 272                                 ops = &sysfs_prealloc_kfops_ro;
 273                         else
 274                                 ops = &sysfs_file_kfops_ro;
 275                 } else if (sysfs_ops->store) {
 276                         if (mode & SYSFS_PREALLOC)
 277                                 ops = &sysfs_prealloc_kfops_wo;
 278                         else
 279                                 ops = &sysfs_file_kfops_wo;
 280                 } else
 281                         ops = &sysfs_file_kfops_empty;
 282
 283                 size = PAGE_SIZE;
 284         } else {
 285                 struct bin_attribute *battr = (void *)attr;
 286
 287                 if (battr->mmap)
 288                         ops = &sysfs_bin_kfops_mmap;
 289                 else if (battr->read && battr->write)
 290                         ops = &sysfs_bin_kfops_rw;
 291                 else if (battr->read)
 292                         ops = &sysfs_bin_kfops_ro;
 293                 else if (battr->write)
 294                         ops = &sysfs_bin_kfops_wo;
 295                 else
 296                         ops = &sysfs_file_kfops_empty;
 297
 298                 size = battr->size;
 299         }
 300
 301 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 302         if (!attr->ignore_lockdep)
 303                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
 304 #endif
 305         kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
 306                                   (void *)attr, ns, key);
 307         if (IS_ERR(kn)) {
 308                 if (PTR_ERR(kn) == -EEXIST)
 309                         sysfs_warn_dup(parent, attr->name);
 310                 return PTR_ERR(kn);
 311         }
 312         return 0;
 313 }
 314
 315 int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
 316                    bool is_bin)
 317 {
 318         return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
 319 }
 320
 321 /**
 322  * sysfs_create_file_ns - create an attribute file for an object with custom ns
 323  * @kobj: object we're creating for
 324  * @attr: attribute descriptor
 325  * @ns: namespace the new file should belong to
 326  */
 327 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
 328                          const void *ns)
 329 {
 330         BUG_ON(!kobj || !kobj->sd || !attr);
 331
 332         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
 333
 334 }
 335 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
 336
 337 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
 338 {
 339         int err = 0;
 340         int i;
 341
 342         for (i = 0; ptr[i] && !err; i++)
 343                 err = sysfs_create_file(kobj, ptr[i]);
 344         if (err)
 345                 while (--i >= 0)
 346                         sysfs_remove_file(kobj, ptr[i]);
 347         return err;
 348 }
 349 EXPORT_SYMBOL_GPL(sysfs_create_files);
 350
 351 /**
 352  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 353  * @kobj: object we're acting for.
 354  * @attr: attribute descriptor.
 355  * @group: group name.
 356  */
 357 int sysfs_add_file_to_group(struct kobject *kobj,
 358                 const struct attribute *attr, const char *group)
 359 {
 360         struct kernfs_node *parent;
 361         int error;
 362
 363         if (group) {
 364                 parent = kernfs_find_and_get(kobj->sd, group);
 365         } else {
 366                 parent = kobj->sd;
 367                 kernfs_get(parent);
 368         }
 369
 370         if (!parent)
 371                 return -ENOENT;
 372
 373         error = sysfs_add_file(parent, attr, false);
 374         kernfs_put(parent);
 375
 376         return error;
 377 }
 378 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 379
 380 /**
 381  * sysfs_chmod_file - update the modified mode value on an object attribute.
 382  * @kobj: object we're acting for.
 383  * @attr: attribute descriptor.
 384  * @mode: file permissions.
 385  *
 386  */
 387 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
 388                      umode_t mode)
 389 {
 390         struct kernfs_node *kn;
 391         struct iattr newattrs;
 392         int rc;
 393
 394         kn = kernfs_find_and_get(kobj->sd, attr->name);
 395         if (!kn)
 396                 return -ENOENT;
 397
 398         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
 399         newattrs.ia_valid = ATTR_MODE;
 400
 401         rc = kernfs_setattr(kn, &newattrs);
 402
 403         kernfs_put(kn);
 404         return rc;
 405 }
 406 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 407
 408 /**
 409  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
 410  * @kobj: object we're acting for
 411  * @attr: attribute descriptor
 412  * @ns: namespace tag of the file to remove
 413  *
 414  * Hash the attribute name and namespace tag and kill the victim.
 415  */
 416 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
 417                           const void *ns)
 418 {
 419         struct kernfs_node *parent = kobj->sd;
 420
 421         kernfs_remove_by_name_ns(parent, attr->name, ns);
 422 }
 423 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
 424
 425 /**
 426  * sysfs_remove_file_self - remove an object attribute from its own method
 427  * @kobj: object we're acting for
 428  * @attr: attribute descriptor
 429  *
 430  * See kernfs_remove_self() for details.
 431  */
 432 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
 433 {
 434         struct kernfs_node *parent = kobj->sd;
 435         struct kernfs_node *kn;
 436         bool ret;
 437
 438         kn = kernfs_find_and_get(parent, attr->name);
 439         if (WARN_ON_ONCE(!kn))
 440                 return false;
 441
 442         ret = kernfs_remove_self(kn);
 443
 444         kernfs_put(kn);
 445         return ret;
 446 }
 447
 448 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
 449 {
 450         int i;
 451         for (i = 0; ptr[i]; i++)
 452                 sysfs_remove_file(kobj, ptr[i]);
 453 }
 454 EXPORT_SYMBOL_GPL(sysfs_remove_files);
 455
 456 /**
 457  * sysfs_remove_file_from_group - remove an attribute file from a group.
 458  * @kobj: object we're acting for.
 459  * @attr: attribute descriptor.
 460  * @group: group name.
 461  */
 462 void sysfs_remove_file_from_group(struct kobject *kobj,
 463                 const struct attribute *attr, const char *group)
 464 {
 465         struct kernfs_node *parent;
 466
 467         if (group) {
 468                 parent = kernfs_find_and_get(kobj->sd, group);
 469         } else {
 470                 parent = kobj->sd;
 471                 kernfs_get(parent);
 472         }
 473
 474         if (parent) {
 475                 kernfs_remove_by_name(parent, attr->name);
 476                 kernfs_put(parent);
 477         }
 478 }
 479 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 480
 481 /**
 482  *      sysfs_create_bin_file - create binary file for object.
 483  *      @kobj:  object.
 484  *      @attr:  attribute descriptor.
 485  */
 486 int sysfs_create_bin_file(struct kobject *kobj,
 487                           const struct bin_attribute *attr)
 488 {
 489         BUG_ON(!kobj || !kobj->sd || !attr);
 490
 491         return sysfs_add_file(kobj->sd, &attr->attr, true);
 492 }
 493 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
 494
 495 /**
 496  *      sysfs_remove_bin_file - remove binary file for object.
 497  *      @kobj:  object.
 498  *      @attr:  attribute descriptor.
 499  */
 500 void sysfs_remove_bin_file(struct kobject *kobj,
 501                            const struct bin_attribute *attr)
 502 {
 503         kernfs_remove_by_name(kobj->sd, attr->attr.name);
 504 }
 505 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);