fs/sysfs/file.c

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This source file includes following definitions.
sysfs_file_ops
sysfs_kf_seq_show
sysfs_kf_bin_read
sysfs_kf_read
sysfs_kf_write
sysfs_kf_bin_write
sysfs_kf_bin_mmap
sysfs_notify
sysfs_add_file_mode_ns
sysfs_create_file_ns
sysfs_create_files
sysfs_add_file_to_group
sysfs_chmod_file
sysfs_break_active_protection
sysfs_unbreak_active_protection
sysfs_remove_file_ns
sysfs_remove_file_self
sysfs_remove_files
sysfs_remove_file_from_group
sysfs_create_bin_file
sysfs_remove_bin_file
   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 
  21 /*
  22  * Determine ktype->sysfs_ops for the given kernfs_node.  This function
  23  * must be called while holding an active reference.
  24  */
  25 static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
  26 {
  27         struct kobject *kobj = kn->parent->priv;
  28 
  29         if (kn->flags & KERNFS_LOCKDEP)
  30                 lockdep_assert_held(kn);
  31         return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
  32 }
  33 
  34 /*
  35  * Reads on sysfs are handled through seq_file, which takes care of hairy
  36  * details like buffering and seeking.  The following function pipes
  37  * sysfs_ops->show() result through seq_file.
  38  */
  39 static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
  40 {
  41         struct kernfs_open_file *of = sf->private;
  42         struct kobject *kobj = of->kn->parent->priv;
  43         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
  44         ssize_t count;
  45         char *buf;
  46 
  47         /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
  48         count = seq_get_buf(sf, &buf);
  49         if (count < PAGE_SIZE) {
  50                 seq_commit(sf, -1);
  51                 return 0;
  52         }
  53         memset(buf, 0, PAGE_SIZE);
  54 
  55         /*
  56          * Invoke show().  Control may reach here via seq file lseek even
  57          * if @ops->show() isn't implemented.
  58          */
  59         if (ops->show) {
  60                 count = ops->show(kobj, of->kn->priv, buf);
  61                 if (count < 0)
  62                         return count;
  63         }
  64 
  65         /*
  66          * The code works fine with PAGE_SIZE return but it's likely to
  67          * indicate truncated result or overflow in normal use cases.
  68          */
  69         if (count >= (ssize_t)PAGE_SIZE) {
  70                 printk("fill_read_buffer: %pS returned bad count\n",
  71                                 ops->show);
  72                 /* Try to struggle along */
  73                 count = PAGE_SIZE - 1;
  74         }
  75         seq_commit(sf, count);
  76         return 0;
  77 }
  78 
  79 static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
  80                                  size_t count, loff_t pos)
  81 {
  82         struct bin_attribute *battr = of->kn->priv;
  83         struct kobject *kobj = of->kn->parent->priv;
  84         loff_t size = file_inode(of->file)->i_size;
  85 
  86         if (!count)
  87                 return 0;
  88 
  89         if (size) {
  90                 if (pos >= size)
  91                         return 0;
  92                 if (pos + count > size)
  93                         count = size - pos;
  94         }
  95 
  96         if (!battr->read)
  97                 return -EIO;
  98 
  99         return battr->read(of->file, kobj, battr, buf, pos, count);
 100 }
 101 
 102 /* kernfs read callback for regular sysfs files with pre-alloc */
 103 static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
 104                              size_t count, loff_t pos)
 105 {
 106         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 107         struct kobject *kobj = of->kn->parent->priv;
 108         ssize_t len;
 109 
 110         /*
 111          * If buf != of->prealloc_buf, we don't know how
 112          * large it is, so cannot safely pass it to ->show
 113          */
 114         if (WARN_ON_ONCE(buf != of->prealloc_buf))
 115                 return 0;
 116         len = ops->show(kobj, of->kn->priv, buf);
 117         if (len < 0)
 118                 return len;
 119         if (pos) {
 120                 if (len <= pos)
 121                         return 0;
 122                 len -= pos;
 123                 memmove(buf, buf + pos, len);
 124         }
 125         return min_t(ssize_t, count, len);
 126 }
 127 
 128 /* kernfs write callback for regular sysfs files */
 129 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
 130                               size_t count, loff_t pos)
 131 {
 132         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 133         struct kobject *kobj = of->kn->parent->priv;
 134 
 135         if (!count)
 136                 return 0;
 137 
 138         return ops->store(kobj, of->kn->priv, buf, count);
 139 }
 140 
 141 /* kernfs write callback for bin sysfs files */
 142 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
 143                                   size_t count, loff_t pos)
 144 {
 145         struct bin_attribute *battr = of->kn->priv;
 146         struct kobject *kobj = of->kn->parent->priv;
 147         loff_t size = file_inode(of->file)->i_size;
 148 
 149         if (size) {
 150                 if (size <= pos)
 151                         return -EFBIG;
 152                 count = min_t(ssize_t, count, size - pos);
 153         }
 154         if (!count)
 155                 return 0;
 156 
 157         if (!battr->write)
 158                 return -EIO;
 159 
 160         return battr->write(of->file, kobj, battr, buf, pos, count);
 161 }
 162 
 163 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
 164                              struct vm_area_struct *vma)
 165 {
 166         struct bin_attribute *battr = of->kn->priv;
 167         struct kobject *kobj = of->kn->parent->priv;
 168 
 169         return battr->mmap(of->file, kobj, battr, vma);
 170 }
 171 
 172 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
 173 {
 174         struct kernfs_node *kn = kobj->sd, *tmp;
 175 
 176         if (kn && dir)
 177                 kn = kernfs_find_and_get(kn, dir);
 178         else
 179                 kernfs_get(kn);
 180 
 181         if (kn && attr) {
 182                 tmp = kernfs_find_and_get(kn, attr);
 183                 kernfs_put(kn);
 184                 kn = tmp;
 185         }
 186 
 187         if (kn) {
 188                 kernfs_notify(kn);
 189                 kernfs_put(kn);
 190         }
 191 }
 192 EXPORT_SYMBOL_GPL(sysfs_notify);
 193 
 194 static const struct kernfs_ops sysfs_file_kfops_empty = {
 195 };
 196 
 197 static const struct kernfs_ops sysfs_file_kfops_ro = {
 198         .seq_show       = sysfs_kf_seq_show,
 199 };
 200 
 201 static const struct kernfs_ops sysfs_file_kfops_wo = {
 202         .write          = sysfs_kf_write,
 203 };
 204 
 205 static const struct kernfs_ops sysfs_file_kfops_rw = {
 206         .seq_show       = sysfs_kf_seq_show,
 207         .write          = sysfs_kf_write,
 208 };
 209 
 210 static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
 211         .read           = sysfs_kf_read,
 212         .prealloc       = true,
 213 };
 214 
 215 static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
 216         .write          = sysfs_kf_write,
 217         .prealloc       = true,
 218 };
 219 
 220 static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
 221         .read           = sysfs_kf_read,
 222         .write          = sysfs_kf_write,
 223         .prealloc       = true,
 224 };
 225 
 226 static const struct kernfs_ops sysfs_bin_kfops_ro = {
 227         .read           = sysfs_kf_bin_read,
 228 };
 229 
 230 static const struct kernfs_ops sysfs_bin_kfops_wo = {
 231         .write          = sysfs_kf_bin_write,
 232 };
 233 
 234 static const struct kernfs_ops sysfs_bin_kfops_rw = {
 235         .read           = sysfs_kf_bin_read,
 236         .write          = sysfs_kf_bin_write,
 237 };
 238 
 239 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
 240         .read           = sysfs_kf_bin_read,
 241         .write          = sysfs_kf_bin_write,
 242         .mmap           = sysfs_kf_bin_mmap,
 243 };
 244 
 245 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
 246                            const struct attribute *attr, bool is_bin,
 247                            umode_t mode, kuid_t uid, kgid_t gid, const void *ns)
 248 {
 249         struct lock_class_key *key = NULL;
 250         const struct kernfs_ops *ops;
 251         struct kernfs_node *kn;
 252         loff_t size;
 253 
 254         if (!is_bin) {
 255                 struct kobject *kobj = parent->priv;
 256                 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
 257 
 258                 /* every kobject with an attribute needs a ktype assigned */
 259                 if (WARN(!sysfs_ops, KERN_ERR
 260                          "missing sysfs attribute operations for kobject: %s\n",
 261                          kobject_name(kobj)))
 262                         return -EINVAL;
 263 
 264                 if (sysfs_ops->show && sysfs_ops->store) {
 265                         if (mode & SYSFS_PREALLOC)
 266                                 ops = &sysfs_prealloc_kfops_rw;
 267                         else
 268                                 ops = &sysfs_file_kfops_rw;
 269                 } else if (sysfs_ops->show) {
 270                         if (mode & SYSFS_PREALLOC)
 271                                 ops = &sysfs_prealloc_kfops_ro;
 272                         else
 273                                 ops = &sysfs_file_kfops_ro;
 274                 } else if (sysfs_ops->store) {
 275                         if (mode & SYSFS_PREALLOC)
 276                                 ops = &sysfs_prealloc_kfops_wo;
 277                         else
 278                                 ops = &sysfs_file_kfops_wo;
 279                 } else
 280                         ops = &sysfs_file_kfops_empty;
 281 
 282                 size = PAGE_SIZE;
 283         } else {
 284                 struct bin_attribute *battr = (void *)attr;
 285 
 286                 if (battr->mmap)
 287                         ops = &sysfs_bin_kfops_mmap;
 288                 else if (battr->read && battr->write)
 289                         ops = &sysfs_bin_kfops_rw;
 290                 else if (battr->read)
 291                         ops = &sysfs_bin_kfops_ro;
 292                 else if (battr->write)
 293                         ops = &sysfs_bin_kfops_wo;
 294                 else
 295                         ops = &sysfs_file_kfops_empty;
 296 
 297                 size = battr->size;
 298         }
 299 
 300 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 301         if (!attr->ignore_lockdep)
 302                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
 303 #endif
 304 
 305         kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
 306                                   size, ops, (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 /**
 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         kuid_t uid;
 325         kgid_t gid;
 326 
 327         if (WARN_ON(!kobj || !kobj->sd || !attr))
 328                 return -EINVAL;
 329 
 330         kobject_get_ownership(kobj, &uid, &gid);
 331         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode,
 332                                       uid, gid, ns);
 333 
 334 }
 335 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
 336 
 337 int sysfs_create_files(struct kobject *kobj, const struct attribute * const *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         kuid_t uid;
 362         kgid_t gid;
 363         int error;
 364 
 365         if (group) {
 366                 parent = kernfs_find_and_get(kobj->sd, group);
 367         } else {
 368                 parent = kobj->sd;
 369                 kernfs_get(parent);
 370         }
 371 
 372         if (!parent)
 373                 return -ENOENT;
 374 
 375         kobject_get_ownership(kobj, &uid, &gid);
 376         error = sysfs_add_file_mode_ns(parent, attr, false,
 377                                        attr->mode, uid, gid, NULL);
 378         kernfs_put(parent);
 379 
 380         return error;
 381 }
 382 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 383 
 384 /**
 385  * sysfs_chmod_file - update the modified mode value on an object attribute.
 386  * @kobj: object we're acting for.
 387  * @attr: attribute descriptor.
 388  * @mode: file permissions.
 389  *
 390  */
 391 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
 392                      umode_t mode)
 393 {
 394         struct kernfs_node *kn;
 395         struct iattr newattrs;
 396         int rc;
 397 
 398         kn = kernfs_find_and_get(kobj->sd, attr->name);
 399         if (!kn)
 400                 return -ENOENT;
 401 
 402         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
 403         newattrs.ia_valid = ATTR_MODE;
 404 
 405         rc = kernfs_setattr(kn, &newattrs);
 406 
 407         kernfs_put(kn);
 408         return rc;
 409 }
 410 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 411 
 412 /**
 413  * sysfs_break_active_protection - break "active" protection
 414  * @kobj: The kernel object @attr is associated with.
 415  * @attr: The attribute to break the "active" protection for.
 416  *
 417  * With sysfs, just like kernfs, deletion of an attribute is postponed until
 418  * all active .show() and .store() callbacks have finished unless this function
 419  * is called. Hence this function is useful in methods that implement self
 420  * deletion.
 421  */
 422 struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
 423                                                   const struct attribute *attr)
 424 {
 425         struct kernfs_node *kn;
 426 
 427         kobject_get(kobj);
 428         kn = kernfs_find_and_get(kobj->sd, attr->name);
 429         if (kn)
 430                 kernfs_break_active_protection(kn);
 431         return kn;
 432 }
 433 EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
 434 
 435 /**
 436  * sysfs_unbreak_active_protection - restore "active" protection
 437  * @kn: Pointer returned by sysfs_break_active_protection().
 438  *
 439  * Undo the effects of sysfs_break_active_protection(). Since this function
 440  * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
 441  * argument passed to sysfs_break_active_protection() that attribute may have
 442  * been removed between the sysfs_break_active_protection() and
 443  * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
 444  * this function has returned.
 445  */
 446 void sysfs_unbreak_active_protection(struct kernfs_node *kn)
 447 {
 448         struct kobject *kobj = kn->parent->priv;
 449 
 450         kernfs_unbreak_active_protection(kn);
 451         kernfs_put(kn);
 452         kobject_put(kobj);
 453 }
 454 EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
 455 
 456 /**
 457  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
 458  * @kobj: object we're acting for
 459  * @attr: attribute descriptor
 460  * @ns: namespace tag of the file to remove
 461  *
 462  * Hash the attribute name and namespace tag and kill the victim.
 463  */
 464 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
 465                           const void *ns)
 466 {
 467         struct kernfs_node *parent = kobj->sd;
 468 
 469         kernfs_remove_by_name_ns(parent, attr->name, ns);
 470 }
 471 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
 472 
 473 /**
 474  * sysfs_remove_file_self - remove an object attribute from its own method
 475  * @kobj: object we're acting for
 476  * @attr: attribute descriptor
 477  *
 478  * See kernfs_remove_self() for details.
 479  */
 480 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
 481 {
 482         struct kernfs_node *parent = kobj->sd;
 483         struct kernfs_node *kn;
 484         bool ret;
 485 
 486         kn = kernfs_find_and_get(parent, attr->name);
 487         if (WARN_ON_ONCE(!kn))
 488                 return false;
 489 
 490         ret = kernfs_remove_self(kn);
 491 
 492         kernfs_put(kn);
 493         return ret;
 494 }
 495 
 496 void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
 497 {
 498         int i;
 499 
 500         for (i = 0; ptr[i]; i++)
 501                 sysfs_remove_file(kobj, ptr[i]);
 502 }
 503 EXPORT_SYMBOL_GPL(sysfs_remove_files);
 504 
 505 /**
 506  * sysfs_remove_file_from_group - remove an attribute file from a group.
 507  * @kobj: object we're acting for.
 508  * @attr: attribute descriptor.
 509  * @group: group name.
 510  */
 511 void sysfs_remove_file_from_group(struct kobject *kobj,
 512                 const struct attribute *attr, const char *group)
 513 {
 514         struct kernfs_node *parent;
 515 
 516         if (group) {
 517                 parent = kernfs_find_and_get(kobj->sd, group);
 518         } else {
 519                 parent = kobj->sd;
 520                 kernfs_get(parent);
 521         }
 522 
 523         if (parent) {
 524                 kernfs_remove_by_name(parent, attr->name);
 525                 kernfs_put(parent);
 526         }
 527 }
 528 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 529 
 530 /**
 531  *      sysfs_create_bin_file - create binary file for object.
 532  *      @kobj:  object.
 533  *      @attr:  attribute descriptor.
 534  */
 535 int sysfs_create_bin_file(struct kobject *kobj,
 536                           const struct bin_attribute *attr)
 537 {
 538         kuid_t uid;
 539         kgid_t gid;
 540 
 541         if (WARN_ON(!kobj || !kobj->sd || !attr))
 542                 return -EINVAL;
 543 
 544         kobject_get_ownership(kobj, &uid, &gid);
 545         return sysfs_add_file_mode_ns(kobj->sd, &attr->attr, true,
 546                                       attr->attr.mode, uid, gid, NULL);
 547 }
 548 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
 549 
 550 /**
 551  *      sysfs_remove_bin_file - remove binary file for object.
 552  *      @kobj:  object.
 553  *      @attr:  attribute descriptor.
 554  */
 555 void sysfs_remove_bin_file(struct kobject *kobj,
 556                            const struct bin_attribute *attr)
 557 {
 558         kernfs_remove_by_name(kobj->sd, attr->attr.name);
 559 }
 560 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
/* [<][>][^][v][top][bottom][index][help] */
root/fs/sysfs/file.c

DEFINITIONS
