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Linux/fs/debugfs/inode.c

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

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