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, 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         kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
 308                                   (void *)attr, ns, key);
 309         if (IS_ERR(kn)) {
 310                 if (PTR_ERR(kn) == -EEXIST)
 311                         sysfs_warn_dup(parent, attr->name);
 312                 return PTR_ERR(kn);
 313         }
 314         return 0;
 315 }
 316
 317 int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
 318                    bool is_bin)
 319 {
 320         return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
 321 }
 322
 323 /**
 324  * sysfs_create_file_ns - create an attribute file for an object with custom ns
 325  * @kobj: object we're creating for
 326  * @attr: attribute descriptor
 327  * @ns: namespace the new file should belong to
 328  */
 329 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
 330                          const void *ns)
 331 {
 332         BUG_ON(!kobj || !kobj->sd || !attr);
 333
 334         return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, 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         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         error = sysfs_add_file(parent, attr, false);
 376         kernfs_put(parent);
 377
 378         return error;
 379 }
 380 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 381
 382 /**
 383  * sysfs_chmod_file - update the modified mode value on an object attribute.
 384  * @kobj: object we're acting for.
 385  * @attr: attribute descriptor.
 386  * @mode: file permissions.
 387  *
 388  */
 389 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
 390                      umode_t mode)
 391 {
 392         struct kernfs_node *kn;
 393         struct iattr newattrs;
 394         int rc;
 395
 396         kn = kernfs_find_and_get(kobj->sd, attr->name);
 397         if (!kn)
 398                 return -ENOENT;
 399
 400         newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
 401         newattrs.ia_valid = ATTR_MODE;
 402
 403         rc = kernfs_setattr(kn, &newattrs);
 404
 405         kernfs_put(kn);
 406         return rc;
 407 }
 408 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 409
 410 /**
 411  * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
 412  * @kobj: object we're acting for
 413  * @attr: attribute descriptor
 414  * @ns: namespace tag of the file to remove
 415  *
 416  * Hash the attribute name and namespace tag and kill the victim.
 417  */
 418 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
 419                           const void *ns)
 420 {
 421         struct kernfs_node *parent = kobj->sd;
 422
 423         kernfs_remove_by_name_ns(parent, attr->name, ns);
 424 }
 425 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
 426
 427 /**
 428  * sysfs_remove_file_self - remove an object attribute from its own method
 429  * @kobj: object we're acting for
 430  * @attr: attribute descriptor
 431  *
 432  * See kernfs_remove_self() for details.
 433  */
 434 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
 435 {
 436         struct kernfs_node *parent = kobj->sd;
 437         struct kernfs_node *kn;
 438         bool ret;
 439
 440         kn = kernfs_find_and_get(parent, attr->name);
 441         if (WARN_ON_ONCE(!kn))
 442                 return false;
 443
 444         ret = kernfs_remove_self(kn);
 445
 446         kernfs_put(kn);
 447         return ret;
 448 }
 449
 450 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
 451 {
 452         int i;
 453         for (i = 0; ptr[i]; i++)
 454                 sysfs_remove_file(kobj, ptr[i]);
 455 }
 456 EXPORT_SYMBOL_GPL(sysfs_remove_files);
 457
 458 /**
 459  * sysfs_remove_file_from_group - remove an attribute file from a group.
 460  * @kobj: object we're acting for.
 461  * @attr: attribute descriptor.
 462  * @group: group name.
 463  */
 464 void sysfs_remove_file_from_group(struct kobject *kobj,
 465                 const struct attribute *attr, const char *group)
 466 {
 467         struct kernfs_node *parent;
 468
 469         if (group) {
 470                 parent = kernfs_find_and_get(kobj->sd, group);
 471         } else {
 472                 parent = kobj->sd;
 473                 kernfs_get(parent);
 474         }
 475
 476         if (parent) {
 477                 kernfs_remove_by_name(parent, attr->name);
 478                 kernfs_put(parent);
 479         }
 480 }
 481 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 482
 483 /**
 484  *      sysfs_create_bin_file - create binary file for object.
 485  *      @kobj:  object.
 486  *      @attr:  attribute descriptor.
 487  */
 488 int sysfs_create_bin_file(struct kobject *kobj,
 489                           const struct bin_attribute *attr)
 490 {
 491         BUG_ON(!kobj || !kobj->sd || !attr);
 492
 493         return sysfs_add_file(kobj->sd, &attr->attr, true);
 494 }
 495 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
 496
 497 /**
 498  *      sysfs_remove_bin_file - remove binary file for object.
 499  *      @kobj:  object.
 500  *      @attr:  attribute descriptor.
 501  */
 502 void sysfs_remove_bin_file(struct kobject *kobj,
 503                            const struct bin_attribute *attr)
 504 {
 505         kernfs_remove_by_name(kobj->sd, attr->attr.name);
 506 }
 507 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);