root/fs/debugfs/inode.c

DEFINITIONS

1. debugfs_setattr
2. debugfs_get_inode
3. debugfs_parse_options
4. debugfs_apply_options
5. debugfs_remount
6. debugfs_show_options
7. debugfs_free_inode
8. debugfs_release_dentry
9. debugfs_automount
10. debug_fill_super
11. debug_mount
12. debugfs_lookup
13. start_creating
14. failed_creating
15. end_creating
16. __debugfs_create_file
17. debugfs_create_file
18. debugfs_create_file_unsafe
19. debugfs_create_file_size
20. debugfs_create_dir
21. debugfs_create_automount
22. debugfs_create_symlink
23. __debugfs_file_removed
24. __debugfs_remove
25. debugfs_remove
26. debugfs_remove_recursive
27. debugfs_rename
28. debugfs_initialized
29. debugfs_init

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  inode.c - part of debugfs, a tiny little debug file system
   4  *
   5  *  Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@kroah.com>
   6  *  Copyright (C) 2004 IBM Inc.
   7  *  Copyright (C) 2019 Linux Foundation <gregkh@linuxfoundation.org>
   8  *
   9  *  debugfs is for people to use instead of /proc or /sys.
  10  *  See ./Documentation/core-api/kernel-api.rst for more details.
  11  */
  12 
  13 #define pr_fmt(fmt)     "debugfs: " fmt
  14 
  15 #include <linux/module.h>
  16 #include <linux/fs.h>
  17 #include <linux/mount.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/init.h>
  20 #include <linux/kobject.h>
  21 #include <linux/namei.h>
  22 #include <linux/debugfs.h>
  23 #include <linux/fsnotify.h>
  24 #include <linux/string.h>
  25 #include <linux/seq_file.h>
  26 #include <linux/parser.h>
  27 #include <linux/magic.h>
  28 #include <linux/slab.h>
  29 #include <linux/security.h>
  30 
  31 #include "internal.h"
  32 
  33 #define DEBUGFS_DEFAULT_MODE    0700
  34 
  35 static struct vfsmount *debugfs_mount;
  36 static int debugfs_mount_count;
  37 static bool debugfs_registered;
  38 
  39 /*
  40  * Don't allow access attributes to be changed whilst the kernel is locked down
  41  * so that we can use the file mode as part of a heuristic to determine whether
  42  * to lock down individual files.
  43  */
  44 static int debugfs_setattr(struct dentry *dentry, struct iattr *ia)
  45 {
  46         int ret = security_locked_down(LOCKDOWN_DEBUGFS);
  47 
  48         if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
  49                 return ret;
  50         return simple_setattr(dentry, ia);
  51 }
  52 
  53 static const struct inode_operations debugfs_file_inode_operations = {
  54         .setattr        = debugfs_setattr,
  55 };
  56 static const struct inode_operations debugfs_dir_inode_operations = {
  57         .lookup         = simple_lookup,
  58         .setattr        = debugfs_setattr,
  59 };
  60 static const struct inode_operations debugfs_symlink_inode_operations = {
  61         .get_link       = simple_get_link,
  62         .setattr        = debugfs_setattr,
  63 };
  64 
  65 static struct inode *debugfs_get_inode(struct super_block *sb)
  66 {
  67         struct inode *inode = new_inode(sb);
  68         if (inode) {
  69                 inode->i_ino = get_next_ino();
  70                 inode->i_atime = inode->i_mtime =
  71                         inode->i_ctime = current_time(inode);
  72         }
  73         return inode;
  74 }
  75 
  76 struct debugfs_mount_opts {
  77         kuid_t uid;
  78         kgid_t gid;
  79         umode_t mode;
  80 };
  81 
  82 enum {
  83         Opt_uid,
  84         Opt_gid,
  85         Opt_mode,
  86         Opt_err
  87 };
  88 
  89 static const match_table_t tokens = {
  90         {Opt_uid, "uid=%u"},
  91         {Opt_gid, "gid=%u"},
  92         {Opt_mode, "mode=%o"},
  93         {Opt_err, NULL}
  94 };
  95 
  96 struct debugfs_fs_info {
  97         struct debugfs_mount_opts mount_opts;
  98 };
  99 
 100 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
 101 {
 102         substring_t args[MAX_OPT_ARGS];
 103         int option;
 104         int token;
 105         kuid_t uid;
 106         kgid_t gid;
 107         char *p;
 108 
 109         opts->mode = DEBUGFS_DEFAULT_MODE;
 110 
 111         while ((p = strsep(&data, ",")) != NULL) {
 112                 if (!*p)
 113                         continue;
 114 
 115                 token = match_token(p, tokens, args);
 116                 switch (token) {
 117                 case Opt_uid:
 118                         if (match_int(&args[0], &option))
 119                                 return -EINVAL;
 120                         uid = make_kuid(current_user_ns(), option);
 121                         if (!uid_valid(uid))
 122                                 return -EINVAL;
 123                         opts->uid = uid;
 124                         break;
 125                 case Opt_gid:
 126                         if (match_int(&args[0], &option))
 127                                 return -EINVAL;
 128                         gid = make_kgid(current_user_ns(), option);
 129                         if (!gid_valid(gid))
 130                                 return -EINVAL;
 131                         opts->gid = gid;
 132                         break;
 133                 case Opt_mode:
 134                         if (match_octal(&args[0], &option))
 135                                 return -EINVAL;
 136                         opts->mode = option & S_IALLUGO;
 137                         break;
 138                 /*
 139                  * We might like to report bad mount options here;
 140                  * but traditionally debugfs has ignored all mount options
 141                  */
 142                 }
 143         }
 144 
 145         return 0;
 146 }
 147 
 148 static int debugfs_apply_options(struct super_block *sb)
 149 {
 150         struct debugfs_fs_info *fsi = sb->s_fs_info;
 151         struct inode *inode = d_inode(sb->s_root);
 152         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 153 
 154         inode->i_mode &= ~S_IALLUGO;
 155         inode->i_mode |= opts->mode;
 156 
 157         inode->i_uid = opts->uid;
 158         inode->i_gid = opts->gid;
 159 
 160         return 0;
 161 }
 162 
 163 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
 164 {
 165         int err;
 166         struct debugfs_fs_info *fsi = sb->s_fs_info;
 167 
 168         sync_filesystem(sb);
 169         err = debugfs_parse_options(data, &fsi->mount_opts);
 170         if (err)
 171                 goto fail;
 172 
 173         debugfs_apply_options(sb);
 174 
 175 fail:
 176         return err;
 177 }
 178 
 179 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
 180 {
 181         struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
 182         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 183 
 184         if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
 185                 seq_printf(m, ",uid=%u",
 186                            from_kuid_munged(&init_user_ns, opts->uid));
 187         if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
 188                 seq_printf(m, ",gid=%u",
 189                            from_kgid_munged(&init_user_ns, opts->gid));
 190         if (opts->mode != DEBUGFS_DEFAULT_MODE)
 191                 seq_printf(m, ",mode=%o", opts->mode);
 192 
 193         return 0;
 194 }
 195 
 196 static void debugfs_free_inode(struct inode *inode)
 197 {
 198         if (S_ISLNK(inode->i_mode))
 199                 kfree(inode->i_link);
 200         free_inode_nonrcu(inode);
 201 }
 202 
 203 static const struct super_operations debugfs_super_operations = {
 204         .statfs         = simple_statfs,
 205         .remount_fs     = debugfs_remount,
 206         .show_options   = debugfs_show_options,
 207         .free_inode     = debugfs_free_inode,
 208 };
 209 
 210 static void debugfs_release_dentry(struct dentry *dentry)
 211 {
 212         void *fsd = dentry->d_fsdata;
 213 
 214         if (!((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT))
 215                 kfree(dentry->d_fsdata);
 216 }
 217 
 218 static struct vfsmount *debugfs_automount(struct path *path)
 219 {
 220         debugfs_automount_t f;
 221         f = (debugfs_automount_t)path->dentry->d_fsdata;
 222         return f(path->dentry, d_inode(path->dentry)->i_private);
 223 }
 224 
 225 static const struct dentry_operations debugfs_dops = {
 226         .d_delete = always_delete_dentry,
 227         .d_release = debugfs_release_dentry,
 228         .d_automount = debugfs_automount,
 229 };
 230 
 231 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 232 {
 233         static const struct tree_descr debug_files[] = {{""}};
 234         struct debugfs_fs_info *fsi;
 235         int err;
 236 
 237         fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
 238         sb->s_fs_info = fsi;
 239         if (!fsi) {
 240                 err = -ENOMEM;
 241                 goto fail;
 242         }
 243 
 244         err = debugfs_parse_options(data, &fsi->mount_opts);
 245         if (err)
 246                 goto fail;
 247 
 248         err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 249         if (err)
 250                 goto fail;
 251 
 252         sb->s_op = &debugfs_super_operations;
 253         sb->s_d_op = &debugfs_dops;
 254 
 255         debugfs_apply_options(sb);
 256 
 257         return 0;
 258 
 259 fail:
 260         kfree(fsi);
 261         sb->s_fs_info = NULL;
 262         return err;
 263 }
 264 
 265 static struct dentry *debug_mount(struct file_system_type *fs_type,
 266                         int flags, const char *dev_name,
 267                         void *data)
 268 {
 269         return mount_single(fs_type, flags, data, debug_fill_super);
 270 }
 271 
 272 static struct file_system_type debug_fs_type = {
 273         .owner =        THIS_MODULE,
 274         .name =         "debugfs",
 275         .mount =        debug_mount,
 276         .kill_sb =      kill_litter_super,
 277 };
 278 MODULE_ALIAS_FS("debugfs");
 279 
 280 /**
 281  * debugfs_lookup() - look up an existing debugfs file
 282  * @name: a pointer to a string containing the name of the file to look up.
 283  * @parent: a pointer to the parent dentry of the file.
 284  *
 285  * This function will return a pointer to a dentry if it succeeds.  If the file
 286  * doesn't exist or an error occurs, %NULL will be returned.  The returned
 287  * dentry must be passed to dput() when it is no longer needed.
 288  *
 289  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 290  * returned.
 291  */
 292 struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
 293 {
 294         struct dentry *dentry;
 295 
 296         if (IS_ERR(parent))
 297                 return NULL;
 298 
 299         if (!parent)
 300                 parent = debugfs_mount->mnt_root;
 301 
 302         dentry = lookup_one_len_unlocked(name, parent, strlen(name));
 303         if (IS_ERR(dentry))
 304                 return NULL;
 305         if (!d_really_is_positive(dentry)) {
 306                 dput(dentry);
 307                 return NULL;
 308         }
 309         return dentry;
 310 }
 311 EXPORT_SYMBOL_GPL(debugfs_lookup);
 312 
 313 static struct dentry *start_creating(const char *name, struct dentry *parent)
 314 {
 315         struct dentry *dentry;
 316         int error;
 317 
 318         pr_debug("creating file '%s'\n", name);
 319 
 320         if (IS_ERR(parent))
 321                 return parent;
 322 
 323         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 324                               &debugfs_mount_count);
 325         if (error) {
 326                 pr_err("Unable to pin filesystem for file '%s'\n", name);
 327                 return ERR_PTR(error);
 328         }
 329 
 330         /* If the parent is not specified, we create it in the root.
 331          * We need the root dentry to do this, which is in the super
 332          * block. A pointer to that is in the struct vfsmount that we
 333          * have around.
 334          */
 335         if (!parent)
 336                 parent = debugfs_mount->mnt_root;
 337 
 338         inode_lock(d_inode(parent));
 339         dentry = lookup_one_len(name, parent, strlen(name));
 340         if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
 341                 if (d_is_dir(dentry))
 342                         pr_err("Directory '%s' with parent '%s' already present!\n",
 343                                name, parent->d_name.name);
 344                 else
 345                         pr_err("File '%s' in directory '%s' already present!\n",
 346                                name, parent->d_name.name);
 347                 dput(dentry);
 348                 dentry = ERR_PTR(-EEXIST);
 349         }
 350 
 351         if (IS_ERR(dentry)) {
 352                 inode_unlock(d_inode(parent));
 353                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 354         }
 355 
 356         return dentry;
 357 }
 358 
 359 static struct dentry *failed_creating(struct dentry *dentry)
 360 {
 361         inode_unlock(d_inode(dentry->d_parent));
 362         dput(dentry);
 363         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 364         return ERR_PTR(-ENOMEM);
 365 }
 366 
 367 static struct dentry *end_creating(struct dentry *dentry)
 368 {
 369         inode_unlock(d_inode(dentry->d_parent));
 370         return dentry;
 371 }
 372 
 373 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 374                                 struct dentry *parent, void *data,
 375                                 const struct file_operations *proxy_fops,
 376                                 const struct file_operations *real_fops)
 377 {
 378         struct dentry *dentry;
 379         struct inode *inode;
 380 
 381         if (!(mode & S_IFMT))
 382                 mode |= S_IFREG;
 383         BUG_ON(!S_ISREG(mode));
 384         dentry = start_creating(name, parent);
 385 
 386         if (IS_ERR(dentry))
 387                 return dentry;
 388 
 389         inode = debugfs_get_inode(dentry->d_sb);
 390         if (unlikely(!inode)) {
 391                 pr_err("out of free dentries, can not create file '%s'\n",
 392                        name);
 393                 return failed_creating(dentry);
 394         }
 395 
 396         inode->i_mode = mode;
 397         inode->i_private = data;
 398 
 399         inode->i_op = &debugfs_file_inode_operations;
 400         inode->i_fop = proxy_fops;
 401         dentry->d_fsdata = (void *)((unsigned long)real_fops |
 402                                 DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
 403 
 404         d_instantiate(dentry, inode);
 405         fsnotify_create(d_inode(dentry->d_parent), dentry);
 406         return end_creating(dentry);
 407 }
 408 
 409 /**
 410  * debugfs_create_file - create a file in the debugfs filesystem
 411  * @name: a pointer to a string containing the name of the file to create.
 412  * @mode: the permission that the file should have.
 413  * @parent: a pointer to the parent dentry for this file.  This should be a
 414  *          directory dentry if set.  If this parameter is NULL, then the
 415  *          file will be created in the root of the debugfs filesystem.
 416  * @data: a pointer to something that the caller will want to get to later
 417  *        on.  The inode.i_private pointer will point to this value on
 418  *        the open() call.
 419  * @fops: a pointer to a struct file_operations that should be used for
 420  *        this file.
 421  *
 422  * This is the basic "create a file" function for debugfs.  It allows for a
 423  * wide range of flexibility in creating a file, or a directory (if you want
 424  * to create a directory, the debugfs_create_dir() function is
 425  * recommended to be used instead.)
 426  *
 427  * This function will return a pointer to a dentry if it succeeds.  This
 428  * pointer must be passed to the debugfs_remove() function when the file is
 429  * to be removed (no automatic cleanup happens if your module is unloaded,
 430  * you are responsible here.)  If an error occurs, %ERR_PTR(-ERROR) will be
 431  * returned.
 432  *
 433  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 434  * returned.
 435  */
 436 struct dentry *debugfs_create_file(const char *name, umode_t mode,
 437                                    struct dentry *parent, void *data,
 438                                    const struct file_operations *fops)
 439 {
 440 
 441         return __debugfs_create_file(name, mode, parent, data,
 442                                 fops ? &debugfs_full_proxy_file_operations :
 443                                         &debugfs_noop_file_operations,
 444                                 fops);
 445 }
 446 EXPORT_SYMBOL_GPL(debugfs_create_file);
 447 
 448 /**
 449  * debugfs_create_file_unsafe - create a file in the debugfs filesystem
 450  * @name: a pointer to a string containing the name of the file to create.
 451  * @mode: the permission that the file should have.
 452  * @parent: a pointer to the parent dentry for this file.  This should be a
 453  *          directory dentry if set.  If this parameter is NULL, then the
 454  *          file will be created in the root of the debugfs filesystem.
 455  * @data: a pointer to something that the caller will want to get to later
 456  *        on.  The inode.i_private pointer will point to this value on
 457  *        the open() call.
 458  * @fops: a pointer to a struct file_operations that should be used for
 459  *        this file.
 460  *
 461  * debugfs_create_file_unsafe() is completely analogous to
 462  * debugfs_create_file(), the only difference being that the fops
 463  * handed it will not get protected against file removals by the
 464  * debugfs core.
 465  *
 466  * It is your responsibility to protect your struct file_operation
 467  * methods against file removals by means of debugfs_file_get()
 468  * and debugfs_file_put(). ->open() is still protected by
 469  * debugfs though.
 470  *
 471  * Any struct file_operations defined by means of
 472  * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
 473  * thus, may be used here.
 474  */
 475 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
 476                                    struct dentry *parent, void *data,
 477                                    const struct file_operations *fops)
 478 {
 479 
 480         return __debugfs_create_file(name, mode, parent, data,
 481                                 fops ? &debugfs_open_proxy_file_operations :
 482                                         &debugfs_noop_file_operations,
 483                                 fops);
 484 }
 485 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
 486 
 487 /**
 488  * debugfs_create_file_size - create a file in the debugfs filesystem
 489  * @name: a pointer to a string containing the name of the file to create.
 490  * @mode: the permission that the file should have.
 491  * @parent: a pointer to the parent dentry for this file.  This should be a
 492  *          directory dentry if set.  If this parameter is NULL, then the
 493  *          file will be created in the root of the debugfs filesystem.
 494  * @data: a pointer to something that the caller will want to get to later
 495  *        on.  The inode.i_private pointer will point to this value on
 496  *        the open() call.
 497  * @fops: a pointer to a struct file_operations that should be used for
 498  *        this file.
 499  * @file_size: initial file size
 500  *
 501  * This is the basic "create a file" function for debugfs.  It allows for a
 502  * wide range of flexibility in creating a file, or a directory (if you want
 503  * to create a directory, the debugfs_create_dir() function is
 504  * recommended to be used instead.)
 505  *
 506  * This function will return a pointer to a dentry if it succeeds.  This
 507  * pointer must be passed to the debugfs_remove() function when the file is
 508  * to be removed (no automatic cleanup happens if your module is unloaded,
 509  * you are responsible here.)  If an error occurs, %ERR_PTR(-ERROR) will be
 510  * returned.
 511  *
 512  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 513  * returned.
 514  */
 515 struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
 516                                         struct dentry *parent, void *data,
 517                                         const struct file_operations *fops,
 518                                         loff_t file_size)
 519 {
 520         struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
 521 
 522         if (de)
 523                 d_inode(de)->i_size = file_size;
 524         return de;
 525 }
 526 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
 527 
 528 /**
 529  * debugfs_create_dir - create a directory in the debugfs filesystem
 530  * @name: a pointer to a string containing the name of the directory to
 531  *        create.
 532  * @parent: a pointer to the parent dentry for this file.  This should be a
 533  *          directory dentry if set.  If this parameter is NULL, then the
 534  *          directory will be created in the root of the debugfs filesystem.
 535  *
 536  * This function creates a directory in debugfs with the given name.
 537  *
 538  * This function will return a pointer to a dentry if it succeeds.  This
 539  * pointer must be passed to the debugfs_remove() function when the file is
 540  * to be removed (no automatic cleanup happens if your module is unloaded,
 541  * you are responsible here.)  If an error occurs, %ERR_PTR(-ERROR) will be
 542  * returned.
 543  *
 544  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 545  * returned.
 546  */
 547 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 548 {
 549         struct dentry *dentry = start_creating(name, parent);
 550         struct inode *inode;
 551 
 552         if (IS_ERR(dentry))
 553                 return dentry;
 554 
 555         inode = debugfs_get_inode(dentry->d_sb);
 556         if (unlikely(!inode)) {
 557                 pr_err("out of free dentries, can not create directory '%s'\n",
 558                        name);
 559                 return failed_creating(dentry);
 560         }
 561 
 562         inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 563         inode->i_op = &debugfs_dir_inode_operations;
 564         inode->i_fop = &simple_dir_operations;
 565 
 566         /* directory inodes start off with i_nlink == 2 (for "." entry) */
 567         inc_nlink(inode);
 568         d_instantiate(dentry, inode);
 569         inc_nlink(d_inode(dentry->d_parent));
 570         fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
 571         return end_creating(dentry);
 572 }
 573 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 574 
 575 /**
 576  * debugfs_create_automount - create automount point in the debugfs filesystem
 577  * @name: a pointer to a string containing the name of the file to create.
 578  * @parent: a pointer to the parent dentry for this file.  This should be a
 579  *          directory dentry if set.  If this parameter is NULL, then the
 580  *          file will be created in the root of the debugfs filesystem.
 581  * @f: function to be called when pathname resolution steps on that one.
 582  * @data: opaque argument to pass to f().
 583  *
 584  * @f should return what ->d_automount() would.
 585  */
 586 struct dentry *debugfs_create_automount(const char *name,
 587                                         struct dentry *parent,
 588                                         debugfs_automount_t f,
 589                                         void *data)
 590 {
 591         struct dentry *dentry = start_creating(name, parent);
 592         struct inode *inode;
 593 
 594         if (IS_ERR(dentry))
 595                 return dentry;
 596 
 597         inode = debugfs_get_inode(dentry->d_sb);
 598         if (unlikely(!inode)) {
 599                 pr_err("out of free dentries, can not create automount '%s'\n",
 600                        name);
 601                 return failed_creating(dentry);
 602         }
 603 
 604         make_empty_dir_inode(inode);
 605         inode->i_flags |= S_AUTOMOUNT;
 606         inode->i_private = data;
 607         dentry->d_fsdata = (void *)f;
 608         /* directory inodes start off with i_nlink == 2 (for "." entry) */
 609         inc_nlink(inode);
 610         d_instantiate(dentry, inode);
 611         inc_nlink(d_inode(dentry->d_parent));
 612         fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
 613         return end_creating(dentry);
 614 }
 615 EXPORT_SYMBOL(debugfs_create_automount);
 616 
 617 /**
 618  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 619  * @name: a pointer to a string containing the name of the symbolic link to
 620  *        create.
 621  * @parent: a pointer to the parent dentry for this symbolic link.  This
 622  *          should be a directory dentry if set.  If this parameter is NULL,
 623  *          then the symbolic link will be created in the root of the debugfs
 624  *          filesystem.
 625  * @target: a pointer to a string containing the path to the target of the
 626  *          symbolic link.
 627  *
 628  * This function creates a symbolic link with the given name in debugfs that
 629  * links to the given target path.
 630  *
 631  * This function will return a pointer to a dentry if it succeeds.  This
 632  * pointer must be passed to the debugfs_remove() function when the symbolic
 633  * link is to be removed (no automatic cleanup happens if your module is
 634  * unloaded, you are responsible here.)  If an error occurs, %ERR_PTR(-ERROR)
 635  * will be returned.
 636  *
 637  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 638  * returned.
 639  */
 640 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 641                                       const char *target)
 642 {
 643         struct dentry *dentry;
 644         struct inode *inode;
 645         char *link = kstrdup(target, GFP_KERNEL);
 646         if (!link)
 647                 return ERR_PTR(-ENOMEM);
 648 
 649         dentry = start_creating(name, parent);
 650         if (IS_ERR(dentry)) {
 651                 kfree(link);
 652                 return dentry;
 653         }
 654 
 655         inode = debugfs_get_inode(dentry->d_sb);
 656         if (unlikely(!inode)) {
 657                 pr_err("out of free dentries, can not create symlink '%s'\n",
 658                        name);
 659                 kfree(link);
 660                 return failed_creating(dentry);
 661         }
 662         inode->i_mode = S_IFLNK | S_IRWXUGO;
 663         inode->i_op = &debugfs_symlink_inode_operations;
 664         inode->i_link = link;
 665         d_instantiate(dentry, inode);
 666         return end_creating(dentry);
 667 }
 668 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 669 
 670 static void __debugfs_file_removed(struct dentry *dentry)
 671 {
 672         struct debugfs_fsdata *fsd;
 673 
 674         /*
 675          * Paired with the closing smp_mb() implied by a successful
 676          * cmpxchg() in debugfs_file_get(): either
 677          * debugfs_file_get() must see a dead dentry or we must see a
 678          * debugfs_fsdata instance at ->d_fsdata here (or both).
 679          */
 680         smp_mb();
 681         fsd = READ_ONCE(dentry->d_fsdata);
 682         if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
 683                 return;
 684         if (!refcount_dec_and_test(&fsd->active_users))
 685                 wait_for_completion(&fsd->active_users_drained);
 686 }
 687 
 688 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 689 {
 690         int ret = 0;
 691 
 692         if (simple_positive(dentry)) {
 693                 dget(dentry);
 694                 if (d_is_dir(dentry)) {
 695                         ret = simple_rmdir(d_inode(parent), dentry);
 696                         if (!ret)
 697                                 fsnotify_rmdir(d_inode(parent), dentry);
 698                 } else {
 699                         simple_unlink(d_inode(parent), dentry);
 700                         fsnotify_unlink(d_inode(parent), dentry);
 701                 }
 702                 if (!ret)
 703                         d_delete(dentry);
 704                 if (d_is_reg(dentry))
 705                         __debugfs_file_removed(dentry);
 706                 dput(dentry);
 707         }
 708         return ret;
 709 }
 710 
 711 /**
 712  * debugfs_remove - removes a file or directory from the debugfs filesystem
 713  * @dentry: a pointer to a the dentry of the file or directory to be
 714  *          removed.  If this parameter is NULL or an error value, nothing
 715  *          will be done.
 716  *
 717  * This function removes a file or directory in debugfs that was previously
 718  * created with a call to another debugfs function (like
 719  * debugfs_create_file() or variants thereof.)
 720  *
 721  * This function is required to be called in order for the file to be
 722  * removed, no automatic cleanup of files will happen when a module is
 723  * removed, you are responsible here.
 724  */
 725 void debugfs_remove(struct dentry *dentry)
 726 {
 727         struct dentry *parent;
 728         int ret;
 729 
 730         if (IS_ERR_OR_NULL(dentry))
 731                 return;
 732 
 733         parent = dentry->d_parent;
 734         inode_lock(d_inode(parent));
 735         ret = __debugfs_remove(dentry, parent);
 736         inode_unlock(d_inode(parent));
 737         if (!ret)
 738                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 739 }
 740 EXPORT_SYMBOL_GPL(debugfs_remove);
 741 
 742 /**
 743  * debugfs_remove_recursive - recursively removes a directory
 744  * @dentry: a pointer to a the dentry of the directory to be removed.  If this
 745  *          parameter is NULL or an error value, nothing will be done.
 746  *
 747  * This function recursively removes a directory tree in debugfs that
 748  * was previously created with a call to another debugfs function
 749  * (like debugfs_create_file() or variants thereof.)
 750  *
 751  * This function is required to be called in order for the file to be
 752  * removed, no automatic cleanup of files will happen when a module is
 753  * removed, you are responsible here.
 754  */
 755 void debugfs_remove_recursive(struct dentry *dentry)
 756 {
 757         struct dentry *child, *parent;
 758 
 759         if (IS_ERR_OR_NULL(dentry))
 760                 return;
 761 
 762         parent = dentry;
 763  down:
 764         inode_lock(d_inode(parent));
 765  loop:
 766         /*
 767          * The parent->d_subdirs is protected by the d_lock. Outside that
 768          * lock, the child can be unlinked and set to be freed which can
 769          * use the d_u.d_child as the rcu head and corrupt this list.
 770          */
 771         spin_lock(&parent->d_lock);
 772         list_for_each_entry(child, &parent->d_subdirs, d_child) {
 773                 if (!simple_positive(child))
 774                         continue;
 775 
 776                 /* perhaps simple_empty(child) makes more sense */
 777                 if (!list_empty(&child->d_subdirs)) {
 778                         spin_unlock(&parent->d_lock);
 779                         inode_unlock(d_inode(parent));
 780                         parent = child;
 781                         goto down;
 782                 }
 783 
 784                 spin_unlock(&parent->d_lock);
 785 
 786                 if (!__debugfs_remove(child, parent))
 787                         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 788 
 789                 /*
 790                  * The parent->d_lock protects agaist child from unlinking
 791                  * from d_subdirs. When releasing the parent->d_lock we can
 792                  * no longer trust that the next pointer is valid.
 793                  * Restart the loop. We'll skip this one with the
 794                  * simple_positive() check.
 795                  */
 796                 goto loop;
 797         }
 798         spin_unlock(&parent->d_lock);
 799 
 800         inode_unlock(d_inode(parent));
 801         child = parent;
 802         parent = parent->d_parent;
 803         inode_lock(d_inode(parent));
 804 
 805         if (child != dentry)
 806                 /* go up */
 807                 goto loop;
 808 
 809         if (!__debugfs_remove(child, parent))
 810                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 811         inode_unlock(d_inode(parent));
 812 }
 813 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 814 
 815 /**
 816  * debugfs_rename - rename a file/directory in the debugfs filesystem
 817  * @old_dir: a pointer to the parent dentry for the renamed object. This
 818  *          should be a directory dentry.
 819  * @old_dentry: dentry of an object to be renamed.
 820  * @new_dir: a pointer to the parent dentry where the object should be
 821  *          moved. This should be a directory dentry.
 822  * @new_name: a pointer to a string containing the target name.
 823  *
 824  * This function renames a file/directory in debugfs.  The target must not
 825  * exist for rename to succeed.
 826  *
 827  * This function will return a pointer to old_dentry (which is updated to
 828  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 829  * returned.
 830  *
 831  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 832  * returned.
 833  */
 834 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 835                 struct dentry *new_dir, const char *new_name)
 836 {
 837         int error;
 838         struct dentry *dentry = NULL, *trap;
 839         struct name_snapshot old_name;
 840 
 841         if (IS_ERR(old_dir))
 842                 return old_dir;
 843         if (IS_ERR(new_dir))
 844                 return new_dir;
 845         if (IS_ERR_OR_NULL(old_dentry))
 846                 return old_dentry;
 847 
 848         trap = lock_rename(new_dir, old_dir);
 849         /* Source or destination directories don't exist? */
 850         if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
 851                 goto exit;
 852         /* Source does not exist, cyclic rename, or mountpoint? */
 853         if (d_really_is_negative(old_dentry) || old_dentry == trap ||
 854             d_mountpoint(old_dentry))
 855                 goto exit;
 856         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 857         /* Lookup failed, cyclic rename or target exists? */
 858         if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
 859                 goto exit;
 860 
 861         take_dentry_name_snapshot(&old_name, old_dentry);
 862 
 863         error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
 864                               dentry, 0);
 865         if (error) {
 866                 release_dentry_name_snapshot(&old_name);
 867                 goto exit;
 868         }
 869         d_move(old_dentry, dentry);
 870         fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
 871                 d_is_dir(old_dentry),
 872                 NULL, old_dentry);
 873         release_dentry_name_snapshot(&old_name);
 874         unlock_rename(new_dir, old_dir);
 875         dput(dentry);
 876         return old_dentry;
 877 exit:
 878         if (dentry && !IS_ERR(dentry))
 879                 dput(dentry);
 880         unlock_rename(new_dir, old_dir);
 881         if (IS_ERR(dentry))
 882                 return dentry;
 883         return ERR_PTR(-EINVAL);
 884 }
 885 EXPORT_SYMBOL_GPL(debugfs_rename);
 886 
 887 /**
 888  * debugfs_initialized - Tells whether debugfs has been registered
 889  */
 890 bool debugfs_initialized(void)
 891 {
 892         return debugfs_registered;
 893 }
 894 EXPORT_SYMBOL_GPL(debugfs_initialized);
 895 
 896 static int __init debugfs_init(void)
 897 {
 898         int retval;
 899 
 900         retval = sysfs_create_mount_point(kernel_kobj, "debug");
 901         if (retval)
 902                 return retval;
 903 
 904         retval = register_filesystem(&debug_fs_type);
 905         if (retval)
 906                 sysfs_remove_mount_point(kernel_kobj, "debug");
 907         else
 908                 debugfs_registered = true;
 909 
 910         return retval;
 911 }
 912 core_initcall(debugfs_init);
 913