fs/debugfs/inode.c

   1 /*
   2  *  inode.c - part of debugfs, a tiny little debug file system
   3  *
   4  *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   5  *  Copyright (C) 2004 IBM Inc.
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License version
   9  *      2 as published by the Free Software Foundation.
  10  *
  11  *  debugfs is for people to use instead of /proc or /sys.
  12  *  See Documentation/DocBook/kernel-api for more details.
  13  *
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/fs.h>
  18 #include <linux/mount.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/init.h>
  21 #include <linux/kobject.h>
  22 #include <linux/namei.h>
  23 #include <linux/debugfs.h>
  24 #include <linux/fsnotify.h>
  25 #include <linux/string.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/parser.h>
  28 #include <linux/magic.h>
  29 #include <linux/slab.h>
  30
  31 #define DEBUGFS_DEFAULT_MODE    0755
  32
  33 static struct vfsmount *debugfs_mount;
  34 static int debugfs_mount_count;
  35 static bool debugfs_registered;
  36
  37 static struct inode *debugfs_get_inode(struct super_block *sb, umode_t mode, dev_t dev,
  38                                        void *data, const struct file_operations *fops)
  39
  40 {
  41         struct inode *inode = new_inode(sb);
  42
  43         if (inode) {
  44                 inode->i_ino = get_next_ino();
  45                 inode->i_mode = mode;
  46                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  47                 switch (mode & S_IFMT) {
  48                 default:
  49                         init_special_inode(inode, mode, dev);
  50                         break;
  51                 case S_IFREG:
  52                         inode->i_fop = fops ? fops : &debugfs_file_operations;
  53                         inode->i_private = data;
  54                         break;
  55                 case S_IFLNK:
  56                         inode->i_op = &debugfs_link_operations;
  57                         inode->i_private = data;
  58                         break;
  59                 case S_IFDIR:
  60                         inode->i_op = &simple_dir_inode_operations;
  61                         inode->i_fop = &simple_dir_operations;
  62
  63                         /* directory inodes start off with i_nlink == 2
  64                          * (for "." entry) */
  65                         inc_nlink(inode);
  66                         break;
  67                 }
  68         }
  69         return inode;
  70 }
  71
  72 /* SMP-safe */
  73 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  74                          umode_t mode, dev_t dev, void *data,
  75                          const struct file_operations *fops)
  76 {
  77         struct inode *inode;
  78         int error = -EPERM;
  79
  80         if (dentry->d_inode)
  81                 return -EEXIST;
  82
  83         inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);
  84         if (inode) {
  85                 d_instantiate(dentry, inode);
  86                 dget(dentry);
  87                 error = 0;
  88         }
  89         return error;
  90 }
  91
  92 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
  93 {
  94         int res;
  95
  96         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  97         res = debugfs_mknod(dir, dentry, mode, 0, NULL, NULL);
  98         if (!res) {
  99                 inc_nlink(dir);
 100                 fsnotify_mkdir(dir, dentry);
 101         }
 102         return res;
 103 }
 104
 105 static int debugfs_link(struct inode *dir, struct dentry *dentry, umode_t mode,
 106                         void *data)
 107 {
 108         mode = (mode & S_IALLUGO) | S_IFLNK;
 109         return debugfs_mknod(dir, dentry, mode, 0, data, NULL);
 110 }
 111
 112 static int debugfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 113                           void *data, const struct file_operations *fops)
 114 {
 115         int res;
 116
 117         mode = (mode & S_IALLUGO) | S_IFREG;
 118         res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
 119         if (!res)
 120                 fsnotify_create(dir, dentry);
 121         return res;
 122 }
 123
 124 static inline int debugfs_positive(struct dentry *dentry)
 125 {
 126         return dentry->d_inode && !d_unhashed(dentry);
 127 }
 128
 129 struct debugfs_mount_opts {
 130         kuid_t uid;
 131         kgid_t gid;
 132         umode_t mode;
 133 };
 134
 135 enum {
 136         Opt_uid,
 137         Opt_gid,
 138         Opt_mode,
 139         Opt_err
 140 };
 141
 142 static const match_table_t tokens = {
 143         {Opt_uid, "uid=%u"},
 144         {Opt_gid, "gid=%u"},
 145         {Opt_mode, "mode=%o"},
 146         {Opt_err, NULL}
 147 };
 148
 149 struct debugfs_fs_info {
 150         struct debugfs_mount_opts mount_opts;
 151 };
 152
 153 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
 154 {
 155         substring_t args[MAX_OPT_ARGS];
 156         int option;
 157         int token;
 158         kuid_t uid;
 159         kgid_t gid;
 160         char *p;
 161
 162         opts->mode = DEBUGFS_DEFAULT_MODE;
 163
 164         while ((p = strsep(&data, ",")) != NULL) {
 165                 if (!*p)
 166                         continue;
 167
 168                 token = match_token(p, tokens, args);
 169                 switch (token) {
 170                 case Opt_uid:
 171                         if (match_int(&args[0], &option))
 172                                 return -EINVAL;
 173                         uid = make_kuid(current_user_ns(), option);
 174                         if (!uid_valid(uid))
 175                                 return -EINVAL;
 176                         opts->uid = uid;
 177                         break;
 178                 case Opt_gid:
 179                         if (match_int(&args[0], &option))
 180                                 return -EINVAL;
 181                         gid = make_kgid(current_user_ns(), option);
 182                         if (!gid_valid(gid))
 183                                 return -EINVAL;
 184                         opts->gid = gid;
 185                         break;
 186                 case Opt_mode:
 187                         if (match_octal(&args[0], &option))
 188                                 return -EINVAL;
 189                         opts->mode = option & S_IALLUGO;
 190                         break;
 191                 /*
 192                  * We might like to report bad mount options here;
 193                  * but traditionally debugfs has ignored all mount options
 194                  */
 195                 }
 196         }
 197
 198         return 0;
 199 }
 200
 201 static int debugfs_apply_options(struct super_block *sb)
 202 {
 203         struct debugfs_fs_info *fsi = sb->s_fs_info;
 204         struct inode *inode = sb->s_root->d_inode;
 205         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 206
 207         inode->i_mode &= ~S_IALLUGO;
 208         inode->i_mode |= opts->mode;
 209
 210         inode->i_uid = opts->uid;
 211         inode->i_gid = opts->gid;
 212
 213         return 0;
 214 }
 215
 216 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
 217 {
 218         int err;
 219         struct debugfs_fs_info *fsi = sb->s_fs_info;
 220
 221         err = debugfs_parse_options(data, &fsi->mount_opts);
 222         if (err)
 223                 goto fail;
 224
 225         debugfs_apply_options(sb);
 226
 227 fail:
 228         return err;
 229 }
 230
 231 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
 232 {
 233         struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
 234         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 235
 236         if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
 237                 seq_printf(m, ",uid=%u",
 238                            from_kuid_munged(&init_user_ns, opts->uid));
 239         if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
 240                 seq_printf(m, ",gid=%u",
 241                            from_kgid_munged(&init_user_ns, opts->gid));
 242         if (opts->mode != DEBUGFS_DEFAULT_MODE)
 243                 seq_printf(m, ",mode=%o", opts->mode);
 244
 245         return 0;
 246 }
 247
 248 static const struct super_operations debugfs_super_operations = {
 249         .statfs         = simple_statfs,
 250         .remount_fs     = debugfs_remount,
 251         .show_options   = debugfs_show_options,
 252 };
 253
 254 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 255 {
 256         static struct tree_descr debug_files[] = {{""}};
 257         struct debugfs_fs_info *fsi;
 258         int err;
 259
 260         save_mount_options(sb, data);
 261
 262         fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
 263         sb->s_fs_info = fsi;
 264         if (!fsi) {
 265                 err = -ENOMEM;
 266                 goto fail;
 267         }
 268
 269         err = debugfs_parse_options(data, &fsi->mount_opts);
 270         if (err)
 271                 goto fail;
 272
 273         err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 274         if (err)
 275                 goto fail;
 276
 277         sb->s_op = &debugfs_super_operations;
 278
 279         debugfs_apply_options(sb);
 280
 281         return 0;
 282
 283 fail:
 284         kfree(fsi);
 285         sb->s_fs_info = NULL;
 286         return err;
 287 }
 288
 289 static struct dentry *debug_mount(struct file_system_type *fs_type,
 290                         int flags, const char *dev_name,
 291                         void *data)
 292 {
 293         return mount_single(fs_type, flags, data, debug_fill_super);
 294 }
 295
 296 static struct file_system_type debug_fs_type = {
 297         .owner =        THIS_MODULE,
 298         .name =         "debugfs",
 299         .mount =        debug_mount,
 300         .kill_sb =      kill_litter_super,
 301 };
 302 MODULE_ALIAS_FS("debugfs");
 303
 304 static struct dentry *__create_file(const char *name, umode_t mode,
 305                                     struct dentry *parent, void *data,
 306                                     const struct file_operations *fops)
 307 {
 308         struct dentry *dentry = NULL;
 309         int error;
 310
 311         pr_debug("debugfs: creating file '%s'\n",name);
 312
 313         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 314                               &debugfs_mount_count);
 315         if (error)
 316                 goto exit;
 317
 318         /* If the parent is not specified, we create it in the root.
 319          * We need the root dentry to do this, which is in the super
 320          * block. A pointer to that is in the struct vfsmount that we
 321          * have around.
 322          */
 323         if (!parent)
 324                 parent = debugfs_mount->mnt_root;
 325
 326         mutex_lock(&parent->d_inode->i_mutex);
 327         dentry = lookup_one_len(name, parent, strlen(name));
 328         if (!IS_ERR(dentry)) {
 329                 switch (mode & S_IFMT) {
 330                 case S_IFDIR:
 331                         error = debugfs_mkdir(parent->d_inode, dentry, mode);
 332
 333                         break;
 334                 case S_IFLNK:
 335                         error = debugfs_link(parent->d_inode, dentry, mode,
 336                                              data);
 337                         break;
 338                 default:
 339                         error = debugfs_create(parent->d_inode, dentry, mode,
 340                                                data, fops);
 341                         break;
 342                 }
 343                 dput(dentry);
 344         } else
 345                 error = PTR_ERR(dentry);
 346         mutex_unlock(&parent->d_inode->i_mutex);
 347
 348         if (error) {
 349                 dentry = NULL;
 350                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 351         }
 352 exit:
 353         return dentry;
 354 }
 355
 356 /**
 357  * debugfs_create_file - create a file in the debugfs filesystem
 358  * @name: a pointer to a string containing the name of the file to create.
 359  * @mode: the permission that the file should have.
 360  * @parent: a pointer to the parent dentry for this file.  This should be a
 361  *          directory dentry if set.  If this paramater is NULL, then the
 362  *          file will be created in the root of the debugfs filesystem.
 363  * @data: a pointer to something that the caller will want to get to later
 364  *        on.  The inode.i_private pointer will point to this value on
 365  *        the open() call.
 366  * @fops: a pointer to a struct file_operations that should be used for
 367  *        this file.
 368  *
 369  * This is the basic "create a file" function for debugfs.  It allows for a
 370  * wide range of flexibility in creating a file, or a directory (if you want
 371  * to create a directory, the debugfs_create_dir() function is
 372  * recommended to be used instead.)
 373  *
 374  * This function will return a pointer to a dentry if it succeeds.  This
 375  * pointer must be passed to the debugfs_remove() function when the file is
 376  * to be removed (no automatic cleanup happens if your module is unloaded,
 377  * you are responsible here.)  If an error occurs, %NULL will be returned.
 378  *
 379  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 380  * returned.
 381  */
 382 struct dentry *debugfs_create_file(const char *name, umode_t mode,
 383                                    struct dentry *parent, void *data,
 384                                    const struct file_operations *fops)
 385 {
 386         switch (mode & S_IFMT) {
 387         case S_IFREG:
 388         case 0:
 389                 break;
 390         default:
 391                 BUG();
 392         }
 393
 394         return __create_file(name, mode, parent, data, fops);
 395 }
 396 EXPORT_SYMBOL_GPL(debugfs_create_file);
 397
 398 /**
 399  * debugfs_create_dir - create a directory in the debugfs filesystem
 400  * @name: a pointer to a string containing the name of the directory to
 401  *        create.
 402  * @parent: a pointer to the parent dentry for this file.  This should be a
 403  *          directory dentry if set.  If this paramater is NULL, then the
 404  *          directory will be created in the root of the debugfs filesystem.
 405  *
 406  * This function creates a directory in debugfs with the given name.
 407  *
 408  * This function will return a pointer to a dentry if it succeeds.  This
 409  * pointer must be passed to the debugfs_remove() function when the file is
 410  * to be removed (no automatic cleanup happens if your module is unloaded,
 411  * you are responsible here.)  If an error occurs, %NULL will be returned.
 412  *
 413  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 414  * returned.
 415  */
 416 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 417 {
 418         return __create_file(name, S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 419                                    parent, NULL, NULL);
 420 }
 421 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 422
 423 /**
 424  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 425  * @name: a pointer to a string containing the name of the symbolic link to
 426  *        create.
 427  * @parent: a pointer to the parent dentry for this symbolic link.  This
 428  *          should be a directory dentry if set.  If this paramater is NULL,
 429  *          then the symbolic link will be created in the root of the debugfs
 430  *          filesystem.
 431  * @target: a pointer to a string containing the path to the target of the
 432  *          symbolic link.
 433  *
 434  * This function creates a symbolic link with the given name in debugfs that
 435  * links to the given target path.
 436  *
 437  * This function will return a pointer to a dentry if it succeeds.  This
 438  * pointer must be passed to the debugfs_remove() function when the symbolic
 439  * link is to be removed (no automatic cleanup happens if your module is
 440  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 441  * returned.
 442  *
 443  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 444  * returned.
 445  */
 446 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 447                                       const char *target)
 448 {
 449         struct dentry *result;
 450         char *link;
 451
 452         link = kstrdup(target, GFP_KERNEL);
 453         if (!link)
 454                 return NULL;
 455
 456         result = __create_file(name, S_IFLNK | S_IRWXUGO, parent, link, NULL);
 457         if (!result)
 458                 kfree(link);
 459         return result;
 460 }
 461 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 462
 463 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 464 {
 465         int ret = 0;
 466
 467         if (debugfs_positive(dentry)) {
 468                 if (dentry->d_inode) {
 469                         dget(dentry);
 470                         switch (dentry->d_inode->i_mode & S_IFMT) {
 471                         case S_IFDIR:
 472                                 ret = simple_rmdir(parent->d_inode, dentry);
 473                                 break;
 474                         case S_IFLNK:
 475                                 kfree(dentry->d_inode->i_private);
 476                                 /* fall through */
 477                         default:
 478                                 simple_unlink(parent->d_inode, dentry);
 479                                 break;
 480                         }
 481                         if (!ret)
 482                                 d_delete(dentry);
 483                         dput(dentry);
 484                 }
 485         }
 486         return ret;
 487 }
 488
 489 /**
 490  * debugfs_remove - removes a file or directory from the debugfs filesystem
 491  * @dentry: a pointer to a the dentry of the file or directory to be
 492  *          removed.
 493  *
 494  * This function removes a file or directory in debugfs that was previously
 495  * created with a call to another debugfs function (like
 496  * debugfs_create_file() or variants thereof.)
 497  *
 498  * This function is required to be called in order for the file to be
 499  * removed, no automatic cleanup of files will happen when a module is
 500  * removed, you are responsible here.
 501  */
 502 void debugfs_remove(struct dentry *dentry)
 503 {
 504         struct dentry *parent;
 505         int ret;
 506
 507         if (IS_ERR_OR_NULL(dentry))
 508                 return;
 509
 510         parent = dentry->d_parent;
 511         if (!parent || !parent->d_inode)
 512                 return;
 513
 514         mutex_lock(&parent->d_inode->i_mutex);
 515         ret = __debugfs_remove(dentry, parent);
 516         mutex_unlock(&parent->d_inode->i_mutex);
 517         if (!ret)
 518                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 519 }
 520 EXPORT_SYMBOL_GPL(debugfs_remove);
 521
 522 /**
 523  * debugfs_remove_recursive - recursively removes a directory
 524  * @dentry: a pointer to a the dentry of the directory to be removed.
 525  *
 526  * This function recursively removes a directory tree in debugfs that
 527  * was previously created with a call to another debugfs function
 528  * (like debugfs_create_file() or variants thereof.)
 529  *
 530  * This function is required to be called in order for the file to be
 531  * removed, no automatic cleanup of files will happen when a module is
 532  * removed, you are responsible here.
 533  */
 534 void debugfs_remove_recursive(struct dentry *dentry)
 535 {
 536         struct dentry *child, *next, *parent;
 537
 538         if (IS_ERR_OR_NULL(dentry))
 539                 return;
 540
 541         parent = dentry->d_parent;
 542         if (!parent || !parent->d_inode)
 543                 return;
 544
 545         parent = dentry;
 546  down:
 547         mutex_lock(&parent->d_inode->i_mutex);
 548         list_for_each_entry_safe(child, next, &parent->d_subdirs, d_u.d_child) {
 549                 if (!debugfs_positive(child))
 550                         continue;
 551
 552                 /* perhaps simple_empty(child) makes more sense */
 553                 if (!list_empty(&child->d_subdirs)) {
 554                         mutex_unlock(&parent->d_inode->i_mutex);
 555                         parent = child;
 556                         goto down;
 557                 }
 558  up:
 559                 if (!__debugfs_remove(child, parent))
 560                         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 561         }
 562
 563         mutex_unlock(&parent->d_inode->i_mutex);
 564         child = parent;
 565         parent = parent->d_parent;
 566         mutex_lock(&parent->d_inode->i_mutex);
 567
 568         if (child != dentry) {
 569                 next = list_entry(child->d_u.d_child.next, struct dentry,
 570                                         d_u.d_child);
 571                 goto up;
 572         }
 573
 574         if (!__debugfs_remove(child, parent))
 575                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 576         mutex_unlock(&parent->d_inode->i_mutex);
 577 }
 578 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 579
 580 /**
 581  * debugfs_rename - rename a file/directory in the debugfs filesystem
 582  * @old_dir: a pointer to the parent dentry for the renamed object. This
 583  *          should be a directory dentry.
 584  * @old_dentry: dentry of an object to be renamed.
 585  * @new_dir: a pointer to the parent dentry where the object should be
 586  *          moved. This should be a directory dentry.
 587  * @new_name: a pointer to a string containing the target name.
 588  *
 589  * This function renames a file/directory in debugfs.  The target must not
 590  * exist for rename to succeed.
 591  *
 592  * This function will return a pointer to old_dentry (which is updated to
 593  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 594  * returned.
 595  *
 596  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 597  * returned.
 598  */
 599 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 600                 struct dentry *new_dir, const char *new_name)
 601 {
 602         int error;
 603         struct dentry *dentry = NULL, *trap;
 604         const char *old_name;
 605
 606         trap = lock_rename(new_dir, old_dir);
 607         /* Source or destination directories don't exist? */
 608         if (!old_dir->d_inode || !new_dir->d_inode)
 609                 goto exit;
 610         /* Source does not exist, cyclic rename, or mountpoint? */
 611         if (!old_dentry->d_inode || old_dentry == trap ||
 612             d_mountpoint(old_dentry))
 613                 goto exit;
 614         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 615         /* Lookup failed, cyclic rename or target exists? */
 616         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 617                 goto exit;
 618
 619         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 620
 621         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 622                 dentry);
 623         if (error) {
 624                 fsnotify_oldname_free(old_name);
 625                 goto exit;
 626         }
 627         d_move(old_dentry, dentry);
 628         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 629                 S_ISDIR(old_dentry->d_inode->i_mode),
 630                 NULL, old_dentry);
 631         fsnotify_oldname_free(old_name);
 632         unlock_rename(new_dir, old_dir);
 633         dput(dentry);
 634         return old_dentry;
 635 exit:
 636         if (dentry && !IS_ERR(dentry))
 637                 dput(dentry);
 638         unlock_rename(new_dir, old_dir);
 639         return NULL;
 640 }
 641 EXPORT_SYMBOL_GPL(debugfs_rename);
 642
 643 /**
 644  * debugfs_initialized - Tells whether debugfs has been registered
 645  */
 646 bool debugfs_initialized(void)
 647 {
 648         return debugfs_registered;
 649 }
 650 EXPORT_SYMBOL_GPL(debugfs_initialized);
 651
 652
 653 static struct kobject *debug_kobj;
 654
 655 static int __init debugfs_init(void)
 656 {
 657         int retval;
 658
 659         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 660         if (!debug_kobj)
 661                 return -EINVAL;
 662
 663         retval = register_filesystem(&debug_fs_type);
 664         if (retval)
 665                 kobject_put(debug_kobj);
 666         else
 667                 debugfs_registered = true;
 668
 669         return retval;
 670 }
 671 core_initcall(debugfs_init);
 672