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         ssize_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 (WARN_ON_ONCE(buf != of->prealloc_buf))
 118                 return 0;
 119         len = ops->show(kobj, of->kn->priv, buf);
 120         if (len < 0)
 121                 return len;
 122         if (pos) {
 123                 if (len <= pos)
 124                         return 0;
 125                 len -= pos;
 126                 memmove(buf, buf + pos, len);
 127         }
 128         return min_t(ssize_t, count, len);
 129 }
 130
 131 /* kernfs write callback for regular sysfs files */
 132 static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
 133                               size_t count, loff_t pos)
 134 {
 135         const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
 136         struct kobject *kobj = of->kn->parent->priv;
 137
 138         if (!count)
 139                 return 0;
 140
 141         return ops->store(kobj, of->kn->priv, buf, count);
 142 }
 143
 144 /* kernfs write callback for bin sysfs files */
 145 static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
 146                                   size_t count, loff_t pos)
 147 {
 148         struct bin_attribute *battr = of->kn->priv;
 149         struct kobject *kobj = of->kn->parent->priv;
 150         loff_t size = file_inode(of->file)->i_size;
 151
 152         if (size) {
 153                 if (size <= pos)
 154                         return -EFBIG;
 155                 count = min_t(ssize_t, count, size - pos);
 156         }
 157         if (!count)
 158                 return 0;
 159
 160         if (!battr->write)
 161                 return -EIO;
 162
 163         return battr->write(of->file, kobj, battr, buf, pos, count);
 164 }
 165
 166 static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
 167                              struct vm_area_struct *vma)
 168 {
 169         struct bin_attribute *battr = of->kn->priv;
 170         struct kobject *kobj = of->kn->parent->priv;
 171
 172         return battr->mmap(of->file, kobj, battr, vma);
 173 }
 174
 175 void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
 176 {
 177         struct kernfs_node *kn = kobj->sd, *tmp;
 178
 179         if (kn && dir)
 180                 kn = kernfs_find_and_get(kn, dir);
 181         else
 182                 kernfs_get(kn);
 183
 184         if (kn && attr) {
 185                 tmp = kernfs_find_and_get(kn, attr);
 186                 kernfs_put(kn);
 187                 kn = tmp;
 188         }
 189
 190         if (kn) {
 191                 kernfs_notify(kn);
 192                 kernfs_put(kn);
 193         }
 194 }
 195 EXPORT_SYMBOL_GPL(sysfs_notify);
 196
 197 static const struct kernfs_ops sysfs_file_kfops_empty = {
 198 };
 199
 200 static const struct kernfs_ops sysfs_file_kfops_ro = {
 201         .seq_show       = sysfs_kf_seq_show,
 202 };
 203
 204 static const struct kernfs_ops sysfs_file_kfops_wo = {
 205         .write          = sysfs_kf_write,
 206 };
 207
 208 static const struct kernfs_ops sysfs_file_kfops_rw = {
 209         .seq_show       = sysfs_kf_seq_show,
 210         .write          = sysfs_kf_write,
 211 };
 212
 213 static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
 214         .read           = sysfs_kf_read,
 215         .prealloc       = true,
 216 };
 217
 218 static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
 219         .write          = sysfs_kf_write,
 220         .prealloc       = true,
 221 };
 222
 223 static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
 224         .read           = sysfs_kf_read,
 225         .write          = sysfs_kf_write,
 226         .prealloc       = true,
 227 };
 228
 229 static const struct kernfs_ops sysfs_bin_kfops_ro = {
 230         .read           = sysfs_kf_bin_read,
 231 };
 232
 233 static const struct kernfs_ops sysfs_bin_kfops_wo = {
 234         .write          = sysfs_kf_bin_write,
 235 };
 236
 237 static const struct kernfs_ops sysfs_bin_kfops_rw = {
 238         .read           = sysfs_kf_bin_read,
 239         .write          = sysfs_kf_bin_write,
 240 };
 241
 242 static const struct kernfs_ops sysfs_bin_kfops_mmap = {
 243         .read           = sysfs_kf_bin_read,
 244         .write          = sysfs_kf_bin_write,
 245         .mmap           = sysfs_kf_bin_mmap,
 246 };
 247
 248 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
 249                            const struct attribute *attr, bool is_bin,
 250                            umode_t mode, kuid_t uid, kgid_t gid, const void *ns)
 251 {
 252         struct lock_class_key *key = NULL;
 253         const struct kernfs_ops *ops;
 254         struct kernfs_node *kn;
 255         loff_t size;
 256
 257         if (!is_bin) {
 258                 struct kobject *kobj = parent->priv;
 259                 const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
 260
 261                 /* every kobject with an attribute needs a ktype assigned */
 262                 if (WARN(!sysfs_ops, KERN_ERR
 263                          "missing sysfs attribute operations for kobject: %s\n",
 264                          kobject_name(kobj)))
 265                         return -EINVAL;
 266
 267                 if (sysfs_ops->show && sysfs_ops->store) {
 268                         if (mode & SYSFS_PREALLOC)
 269                                 ops = &sysfs_prealloc_kfops_rw;
 270                         else
 271                                 ops = &sysfs_file_kfops_rw;
 272                 } else if (sysfs_ops->show) {
 273                         if (mode & SYSFS_PREALLOC)
 274                                 ops = &sysfs_prealloc_kfops_ro;
 275                         else
 276                                 ops = &sysfs_file_kfops_ro;
 277                 } else if (sysfs_ops->store) {
 278                         if (mode & SYSFS_PREALLOC)
 279                                 ops = &sysfs_prealloc_kfops_wo;
 280                         else
 281                                 ops = &sysfs_file_kfops_wo;
 282                 } else
 283                         ops = &sysfs_file_kfops_empty;
 284
 285                 size = PAGE_SIZE;
 286         } else {
 287                 struct bin_attribute *battr = (void *)attr;
 288
 289                 if (battr->mmap)
 290                         ops = &sysfs_bin_kfops_mmap;
 291                 else if (battr->read && battr->write)
 292                         ops = &sysfs_bin_kfops_rw;
 293                 else if (battr->read)
 294                         ops = &sysfs_bin_kfops_ro;
 295                 else if (battr->write)
 296                         ops = &sysfs_bin_kfops_wo;
 297                 else
 298                         ops = &sysfs_file_kfops_empty;
 299
 300                 size = battr->size;
 301         }
 302
 303 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 304         if (!attr->ignore_lockdep)
 305                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
 306 #endif
 307
 308         kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
 309                                   size, ops, (void *)attr, ns, key);
 310         if (IS_ERR(kn)) {
 311                 if (PTR_ERR(kn) == -EEXIST)
 312                         sysfs_warn_dup(parent, attr->name);
 313                 return PTR_ERR(kn);
 314         }
 315         return 0;
 316 }
 317
 318 /**
 319  * sysfs_create_file_ns - create an attribute file for an object with custom ns
 320  * @kobj: object we're creating for
 321  * @attr: attribute descriptor
 322  * @ns: namespace the new file should belong to
 323  */
 324 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
 325                          const void *ns)
 326 {
 327         kuid_t uid;
 328         kgid_t gid;
 329
 330         BUG_ON(!kobj || !kobj->sd || !attr);
 331
 332         kobject_get_ownership(kobj, &uid, &gid);
 333         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode,
 334                                       uid, gid, ns);
 335
 336 }
 337 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
 338
 339 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
 340 {
 341         int err = 0;
 342         int i;
 343
 344         for (i = 0; ptr[i] && !err; i++)
 345                 err = sysfs_create_file(kobj, ptr[i]);
 346         if (err)
 347                 while (--i >= 0)
 348                         sysfs_remove_file(kobj, ptr[i]);
 349         return err;
 350 }
 351 EXPORT_SYMBOL_GPL(sysfs_create_files);
 352
 353 /**
 354  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 355  * @kobj: object we're acting for.
 356  * @attr: attribute descriptor.
 357  * @group: group name.
 358  */
 359 int sysfs_add_file_to_group(struct kobject *kobj,
 360                 const struct attribute *attr, const char *group)
 361 {
 362         struct kernfs_node *parent;
 363         kuid_t uid;
 364         kgid_t gid;
 365         int error;
 366
 367         if (group) {
 368                 parent = kernfs_find_and_get(kobj->sd, group);
 369         } else {
 370                 parent = kobj->sd;
 371                 kernfs_get(parent);
 372         }
 373
 374         if (!parent)
 375                 return -ENOENT;
 376
 377         kobject_get_ownership(kobj, &uid, &gid);
 378         error = sysfs_add_file_mode_ns(parent, attr, false,
 379                                        attr->mode, uid, gid, NULL);
 380         kernfs_put(parent);
 381
 382         return error;
 383 }
 384 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 385
 386 /**
 387  * sysfs_chmod_file - update the modified mode value on an object attribute.
 388  * @kobj: object we're acting for.
 389  * @attr: attribute descriptor.
 390  * @mode: file permissions.
 391  *
 392  */
 393 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
 394                      umode_t mode)
 395 {
 396         struct kernfs_node *kn;
 397         struct iattr newattrs;
 398         int rc;
 399
 400         kn = kernfs_find_and_get(kobj->sd, attr->name);
 401         if (!kn)
 402                 return -ENOENT;
 403
 404         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
 405         newattrs.ia_valid = ATTR_MODE;
 406
 407         rc = kernfs_setattr(kn, &newattrs);
 408
 409         kernfs_put(kn);
 410         return rc;
 411 }
 412 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 413
 414 /**
 415  * sysfs_break_active_protection - break "active" protection
 416  * @kobj: The kernel object @attr is associated with.
 417  * @attr: The attribute to break the "active" protection for.
 418  *
 419  * With sysfs, just like kernfs, deletion of an attribute is postponed until
 420  * all active .show() and .store() callbacks have finished unless this function
 421  * is called. Hence this function is useful in methods that implement self
 422  * deletion.
 423  */
 424 struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
 425                                                   const struct attribute *attr)
 426 {
 427         struct kernfs_node *kn;
 428
 429         kobject_get(kobj);
 430         kn = kernfs_find_and_get(kobj->sd, attr->name);
 431         if (kn)
 432                 kernfs_break_active_protection(kn);
 433         return kn;
 434 }
 435 EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
 436
 437 /**
 438  * sysfs_unbreak_active_protection - restore "active" protection
 439  * @kn: Pointer returned by sysfs_break_active_protection().
 440  *
 441  * Undo the effects of sysfs_break_active_protection(). Since this function
 442  * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
 443  * argument passed to sysfs_break_active_protection() that attribute may have
 444  * been removed between the sysfs_break_active_protection() and
 445  * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
 446  * this function has returned.
 447  */
 448 void sysfs_unbreak_active_protection(struct kernfs_node *kn)
 449 {
 450         struct kobject *kobj = kn->parent->priv;
 451
 452         kernfs_unbreak_active_protection(kn);
 453         kernfs_put(kn);
 454         kobject_put(kobj);
 455 }
 456 EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
 457
 458 /**
 459  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
 460  * @kobj: object we're acting for
 461  * @attr: attribute descriptor
 462  * @ns: namespace tag of the file to remove
 463  *
 464  * Hash the attribute name and namespace tag and kill the victim.
 465  */
 466 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
 467                           const void *ns)
 468 {
 469         struct kernfs_node *parent = kobj->sd;
 470
 471         kernfs_remove_by_name_ns(parent, attr->name, ns);
 472 }
 473 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
 474
 475 /**
 476  * sysfs_remove_file_self - remove an object attribute from its own method
 477  * @kobj: object we're acting for
 478  * @attr: attribute descriptor
 479  *
 480  * See kernfs_remove_self() for details.
 481  */
 482 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
 483 {
 484         struct kernfs_node *parent = kobj->sd;
 485         struct kernfs_node *kn;
 486         bool ret;
 487
 488         kn = kernfs_find_and_get(parent, attr->name);
 489         if (WARN_ON_ONCE(!kn))
 490                 return false;
 491
 492         ret = kernfs_remove_self(kn);
 493
 494         kernfs_put(kn);
 495         return ret;
 496 }
 497
 498 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
 499 {
 500         int i;
 501         for (i = 0; ptr[i]; i++)
 502                 sysfs_remove_file(kobj, ptr[i]);
 503 }
 504 EXPORT_SYMBOL_GPL(sysfs_remove_files);
 505
 506 /**
 507  * sysfs_remove_file_from_group - remove an attribute file from a group.
 508  * @kobj: object we're acting for.
 509  * @attr: attribute descriptor.
 510  * @group: group name.
 511  */
 512 void sysfs_remove_file_from_group(struct kobject *kobj,
 513                 const struct attribute *attr, const char *group)
 514 {
 515         struct kernfs_node *parent;
 516
 517         if (group) {
 518                 parent = kernfs_find_and_get(kobj->sd, group);
 519         } else {
 520                 parent = kobj->sd;
 521                 kernfs_get(parent);
 522         }
 523
 524         if (parent) {
 525                 kernfs_remove_by_name(parent, attr->name);
 526                 kernfs_put(parent);
 527         }
 528 }
 529 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 530
 531 /**
 532  *      sysfs_create_bin_file - create binary file for object.
 533  *      @kobj:  object.
 534  *      @attr:  attribute descriptor.
 535  */
 536 int sysfs_create_bin_file(struct kobject *kobj,
 537                           const struct bin_attribute *attr)
 538 {
 539         kuid_t uid;
 540         kgid_t gid;
 541
 542         BUG_ON(!kobj || !kobj->sd || !attr);
 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);