1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * inode.c - part of tracefs, a pseudo file system for activating tracing
4 *
5 * Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
6 *
7 * Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
8 *
9 * tracefs is the file system that is used by the tracing infrastructure.
10 */
11
12 #include <linux/module.h>
13 #include <linux/fs.h>
14 #include <linux/fs_context.h>
15 #include <linux/fs_parser.h>
16 #include <linux/kobject.h>
17 #include <linux/namei.h>
18 #include <linux/tracefs.h>
19 #include <linux/fsnotify.h>
20 #include <linux/security.h>
21 #include <linux/seq_file.h>
22 #include <linux/magic.h>
23 #include <linux/slab.h>
24 #include "internal.h"
25
26 #define TRACEFS_DEFAULT_MODE 0700
27 static struct kmem_cache *tracefs_inode_cachep __ro_after_init;
28
29 static struct vfsmount *tracefs_mount;
30 static int tracefs_mount_count;
31 static bool tracefs_registered;
32
33 /*
34 * Keep track of all tracefs_inodes in order to update their
35 * flags if necessary on a remount.
36 */
37 static DEFINE_SPINLOCK(tracefs_inode_lock);
38 static LIST_HEAD(tracefs_inodes);
39
40 static struct inode *tracefs_alloc_inode(struct super_block *sb)
41 {
42 struct tracefs_inode *ti;
43 unsigned long flags;
44
45 ti = alloc_inode_sb(sb, tracefs_inode_cachep, GFP_KERNEL);
46 if (!ti)
47 return NULL;
48
49 spin_lock_irqsave(&tracefs_inode_lock, flags);
50 list_add_rcu(&ti->list, &tracefs_inodes);
51 spin_unlock_irqrestore(&tracefs_inode_lock, flags);
52
53 return &ti->vfs_inode;
54 }
55
56 static void tracefs_free_inode(struct inode *inode)
57 {
58 struct tracefs_inode *ti = get_tracefs(inode);
59
60 kmem_cache_free(tracefs_inode_cachep, ti);
61 }
62
63 static void tracefs_destroy_inode(struct inode *inode)
64 {
65 struct tracefs_inode *ti = get_tracefs(inode);
66 unsigned long flags;
67
68 spin_lock_irqsave(&tracefs_inode_lock, flags);
69 list_del_rcu(&ti->list);
70 spin_unlock_irqrestore(&tracefs_inode_lock, flags);
71 }
72
73 static ssize_t default_read_file(struct file *file, char __user *buf,
74 size_t count, loff_t *ppos)
75 {
76 return 0;
77 }
78
79 static ssize_t default_write_file(struct file *file, const char __user *buf,
80 size_t count, loff_t *ppos)
81 {
82 return count;
83 }
84
85 static const struct file_operations tracefs_file_operations = {
86 .read = default_read_file,
87 .write = default_write_file,
88 .open = simple_open,
89 .llseek = noop_llseek,
90 };
91
92 static struct tracefs_dir_ops {
93 int (*mkdir)(const char *name);
94 int (*rmdir)(const char *name);
95 } tracefs_ops __ro_after_init;
96
97 static char *get_dname(struct dentry *dentry)
98 {
99 const char *dname;
100 char *name;
101 int len = dentry->d_name.len;
102
103 dname = dentry->d_name.name;
104 name = kmalloc(len + 1, GFP_KERNEL);
105 if (!name)
106 return NULL;
107 memcpy(name, dname, len);
108 name[len] = 0;
109 return name;
110 }
111
112 static int tracefs_syscall_mkdir(struct mnt_idmap *idmap,
113 struct inode *inode, struct dentry *dentry,
114 umode_t mode)
115 {
116 struct tracefs_inode *ti;
117 char *name;
118 int ret;
119
120 name = get_dname(dentry);
121 if (!name)
122 return -ENOMEM;
123
124 /*
125 * This is a new directory that does not take the default of
126 * the rootfs. It becomes the default permissions for all the
127 * files and directories underneath it.
128 */
129 ti = get_tracefs(inode);
130 ti->flags |= TRACEFS_INSTANCE_INODE;
131 ti->private = inode;
132
133 /*
134 * The mkdir call can call the generic functions that create
135 * the files within the tracefs system. It is up to the individual
136 * mkdir routine to handle races.
137 */
138 inode_unlock(inode);
139 ret = tracefs_ops.mkdir(name);
140 inode_lock(inode);
141
142 kfree(name);
143
144 return ret;
145 }
146
147 static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
148 {
149 char *name;
150 int ret;
151
152 name = get_dname(dentry);
153 if (!name)
154 return -ENOMEM;
155
156 /*
157 * The rmdir call can call the generic functions that create
158 * the files within the tracefs system. It is up to the individual
159 * rmdir routine to handle races.
160 * This time we need to unlock not only the parent (inode) but
161 * also the directory that is being deleted.
162 */
163 inode_unlock(inode);
164 inode_unlock(d_inode(dentry));
165
166 ret = tracefs_ops.rmdir(name);
167
168 inode_lock_nested(inode, I_MUTEX_PARENT);
169 inode_lock(d_inode(dentry));
170
171 kfree(name);
172
173 return ret;
174 }
175
176 static void set_tracefs_inode_owner(struct inode *inode)
177 {
178 struct tracefs_inode *ti = get_tracefs(inode);
179 struct inode *root_inode = ti->private;
180 kuid_t uid;
181 kgid_t gid;
182
183 uid = root_inode->i_uid;
184 gid = root_inode->i_gid;
185
186 /*
187 * If the root is not the mount point, then check the root's
188 * permissions. If it was never set, then default to the
189 * mount point.
190 */
191 if (root_inode != d_inode(root_inode->i_sb->s_root)) {
192 struct tracefs_inode *rti;
193
194 rti = get_tracefs(root_inode);
195 root_inode = d_inode(root_inode->i_sb->s_root);
196
197 if (!(rti->flags & TRACEFS_UID_PERM_SET))
198 uid = root_inode->i_uid;
199
200 if (!(rti->flags & TRACEFS_GID_PERM_SET))
201 gid = root_inode->i_gid;
202 }
203
204 /*
205 * If this inode has never been referenced, then update
206 * the permissions to the superblock.
207 */
208 if (!(ti->flags & TRACEFS_UID_PERM_SET))
209 inode->i_uid = uid;
210
211 if (!(ti->flags & TRACEFS_GID_PERM_SET))
212 inode->i_gid = gid;
213 }
214
215 static int tracefs_permission(struct mnt_idmap *idmap,
216 struct inode *inode, int mask)
217 {
218 set_tracefs_inode_owner(inode);
219 return generic_permission(idmap, inode, mask);
220 }
221
222 static int tracefs_getattr(struct mnt_idmap *idmap,
223 const struct path *path, struct kstat *stat,
224 u32 request_mask, unsigned int flags)
225 {
226 struct inode *inode = d_backing_inode(path->dentry);
227
228 set_tracefs_inode_owner(inode);
229 generic_fillattr(idmap, request_mask, inode, stat);
230 return 0;
231 }
232
233 static int tracefs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
234 struct iattr *attr)
235 {
236 unsigned int ia_valid = attr->ia_valid;
237 struct inode *inode = d_inode(dentry);
238 struct tracefs_inode *ti = get_tracefs(inode);
239
240 if (ia_valid & ATTR_UID)
241 ti->flags |= TRACEFS_UID_PERM_SET;
242
243 if (ia_valid & ATTR_GID)
244 ti->flags |= TRACEFS_GID_PERM_SET;
245
246 return simple_setattr(idmap, dentry, attr);
247 }
248
249 static const struct inode_operations tracefs_instance_dir_inode_operations = {
250 .lookup = simple_lookup,
251 .mkdir = tracefs_syscall_mkdir,
252 .rmdir = tracefs_syscall_rmdir,
253 .permission = tracefs_permission,
254 .getattr = tracefs_getattr,
255 .setattr = tracefs_setattr,
256 };
257
258 static const struct inode_operations tracefs_dir_inode_operations = {
259 .lookup = simple_lookup,
260 .permission = tracefs_permission,
261 .getattr = tracefs_getattr,
262 .setattr = tracefs_setattr,
263 };
264
265 static const struct inode_operations tracefs_file_inode_operations = {
266 .permission = tracefs_permission,
267 .getattr = tracefs_getattr,
268 .setattr = tracefs_setattr,
269 };
270
271 struct inode *tracefs_get_inode(struct super_block *sb)
272 {
273 struct inode *inode = new_inode(sb);
274 if (inode) {
275 inode->i_ino = get_next_ino();
276 simple_inode_init_ts(inode);
277 }
278 return inode;
279 }
280
281 struct tracefs_fs_info {
282 kuid_t uid;
283 kgid_t gid;
284 umode_t mode;
285 /* Opt_* bitfield. */
286 unsigned int opts;
287 };
288
289 enum {
290 Opt_uid,
291 Opt_gid,
292 Opt_mode,
293 };
294
295 static const struct fs_parameter_spec tracefs_param_specs[] = {
296 fsparam_gid ("gid", Opt_gid),
297 fsparam_u32oct ("mode", Opt_mode),
298 fsparam_uid ("uid", Opt_uid),
299 {}
300 };
301
302 static int tracefs_parse_param(struct fs_context *fc, struct fs_parameter *param)
303 {
304 struct tracefs_fs_info *opts = fc->s_fs_info;
305 struct fs_parse_result result;
306 int opt;
307
308 opt = fs_parse(fc, tracefs_param_specs, param, &result);
309 if (opt < 0)
310 return opt;
311
312 switch (opt) {
313 case Opt_uid:
314 opts->uid = result.uid;
315 break;
316 case Opt_gid:
317 opts->gid = result.gid;
318 break;
319 case Opt_mode:
320 opts->mode = result.uint_32 & S_IALLUGO;
321 break;
322 /*
323 * We might like to report bad mount options here;
324 * but traditionally tracefs has ignored all mount options
325 */
326 }
327
328 opts->opts |= BIT(opt);
329
330 return 0;
331 }
332
333 static int tracefs_apply_options(struct super_block *sb, bool remount)
334 {
335 struct tracefs_fs_info *fsi = sb->s_fs_info;
336 struct inode *inode = d_inode(sb->s_root);
337 struct tracefs_inode *ti;
338 bool update_uid, update_gid;
339 umode_t tmp_mode;
340
341 /*
342 * On remount, only reset mode/uid/gid if they were provided as mount
343 * options.
344 */
345
346 if (!remount || fsi->opts & BIT(Opt_mode)) {
347 tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;
348 tmp_mode |= fsi->mode;
349 WRITE_ONCE(inode->i_mode, tmp_mode);
350 }
351
352 if (!remount || fsi->opts & BIT(Opt_uid))
353 inode->i_uid = fsi->uid;
354
355 if (!remount || fsi->opts & BIT(Opt_gid))
356 inode->i_gid = fsi->gid;
357
358 if (remount && (fsi->opts & BIT(Opt_uid) || fsi->opts & BIT(Opt_gid))) {
359
360 update_uid = fsi->opts & BIT(Opt_uid);
361 update_gid = fsi->opts & BIT(Opt_gid);
362
363 rcu_read_lock();
364 list_for_each_entry_rcu(ti, &tracefs_inodes, list) {
365 if (update_uid) {
366 ti->flags &= ~TRACEFS_UID_PERM_SET;
367 ti->vfs_inode.i_uid = fsi->uid;
368 }
369
370 if (update_gid) {
371 ti->flags &= ~TRACEFS_GID_PERM_SET;
372 ti->vfs_inode.i_gid = fsi->gid;
373 }
374
375 /*
376 * Note, the above ti->vfs_inode updates are
377 * used in eventfs_remount() so they must come
378 * before calling it.
379 */
380 if (ti->flags & TRACEFS_EVENT_INODE)
381 eventfs_remount(ti, update_uid, update_gid);
382 }
383 rcu_read_unlock();
384 }
385
386 return 0;
387 }
388
389 static int tracefs_reconfigure(struct fs_context *fc)
390 {
391 struct super_block *sb = fc->root->d_sb;
392 struct tracefs_fs_info *sb_opts = sb->s_fs_info;
393 struct tracefs_fs_info *new_opts = fc->s_fs_info;
394
395 sync_filesystem(sb);
396 /* structure copy of new mount options to sb */
397 *sb_opts = *new_opts;
398
399 return tracefs_apply_options(sb, true);
400 }
401
402 static int tracefs_show_options(struct seq_file *m, struct dentry *root)
403 {
404 struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
405
406 if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
407 seq_printf(m, ",uid=%u",
408 from_kuid_munged(&init_user_ns, fsi->uid));
409 if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
410 seq_printf(m, ",gid=%u",
411 from_kgid_munged(&init_user_ns, fsi->gid));
412 if (fsi->mode != TRACEFS_DEFAULT_MODE)
413 seq_printf(m, ",mode=%o", fsi->mode);
414
415 return 0;
416 }
417
418 static int tracefs_drop_inode(struct inode *inode)
419 {
420 struct tracefs_inode *ti = get_tracefs(inode);
421
422 /*
423 * This inode is being freed and cannot be used for
424 * eventfs. Clear the flag so that it doesn't call into
425 * eventfs during the remount flag updates. The eventfs_inode
426 * gets freed after an RCU cycle, so the content will still
427 * be safe if the iteration is going on now.
428 */
429 ti->flags &= ~TRACEFS_EVENT_INODE;
430
431 return 1;
432 }
433
434 static const struct super_operations tracefs_super_operations = {
435 .alloc_inode = tracefs_alloc_inode,
436 .free_inode = tracefs_free_inode,
437 .destroy_inode = tracefs_destroy_inode,
438 .drop_inode = tracefs_drop_inode,
439 .statfs = simple_statfs,
440 .show_options = tracefs_show_options,
441 };
442
443 /*
444 * It would be cleaner if eventfs had its own dentry ops.
445 *
446 * Note that d_revalidate is called potentially under RCU,
447 * so it can't take the eventfs mutex etc. It's fine - if
448 * we open a file just as it's marked dead, things will
449 * still work just fine, and just see the old stale case.
450 */
451 static void tracefs_d_release(struct dentry *dentry)
452 {
453 if (dentry->d_fsdata)
454 eventfs_d_release(dentry);
455 }
456
457 static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
458 {
459 struct eventfs_inode *ei = dentry->d_fsdata;
460
461 return !(ei && ei->is_freed);
462 }
463
464 static const struct dentry_operations tracefs_dentry_operations = {
465 .d_revalidate = tracefs_d_revalidate,
466 .d_release = tracefs_d_release,
467 };
468
469 static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc)
470 {
471 static const struct tree_descr trace_files[] = {{""}};
472 int err;
473
474 err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
475 if (err)
476 return err;
477
478 sb->s_op = &tracefs_super_operations;
479 sb->s_d_op = &tracefs_dentry_operations;
480
481 tracefs_apply_options(sb, false);
482
483 return 0;
484 }
485
486 static int tracefs_get_tree(struct fs_context *fc)
487 {
488 return get_tree_single(fc, tracefs_fill_super);
489 }
490
491 static void tracefs_free_fc(struct fs_context *fc)
492 {
493 kfree(fc->s_fs_info);
494 }
495
496 static const struct fs_context_operations tracefs_context_ops = {
497 .free = tracefs_free_fc,
498 .parse_param = tracefs_parse_param,
499 .get_tree = tracefs_get_tree,
500 .reconfigure = tracefs_reconfigure,
501 };
502
503 static int tracefs_init_fs_context(struct fs_context *fc)
504 {
505 struct tracefs_fs_info *fsi;
506
507 fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
508 if (!fsi)
509 return -ENOMEM;
510
511 fsi->mode = TRACEFS_DEFAULT_MODE;
512
513 fc->s_fs_info = fsi;
514 fc->ops = &tracefs_context_ops;
515 return 0;
516 }
517
518 static struct file_system_type trace_fs_type = {
519 .owner = THIS_MODULE,
520 .name = "tracefs",
521 .init_fs_context = tracefs_init_fs_context,
522 .parameters = tracefs_param_specs,
523 .kill_sb = kill_litter_super,
524 };
525 MODULE_ALIAS_FS("tracefs");
526
527 struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
528 {
529 struct dentry *dentry;
530 int error;
531
532 pr_debug("tracefs: creating file '%s'\n",name);
533
534 error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
535 &tracefs_mount_count);
536 if (error)
537 return ERR_PTR(error);
538
539 /* If the parent is not specified, we create it in the root.
540 * We need the root dentry to do this, which is in the super
541 * block. A pointer to that is in the struct vfsmount that we
542 * have around.
543 */
544 if (!parent)
545 parent = tracefs_mount->mnt_root;
546
547 inode_lock(d_inode(parent));
548 if (unlikely(IS_DEADDIR(d_inode(parent))))
549 dentry = ERR_PTR(-ENOENT);
550 else
551 dentry = lookup_one_len(name, parent, strlen(name));
552 if (!IS_ERR(dentry) && d_inode(dentry)) {
553 dput(dentry);
554 dentry = ERR_PTR(-EEXIST);
555 }
556
557 if (IS_ERR(dentry)) {
558 inode_unlock(d_inode(parent));
559 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
560 }
561
562 return dentry;
563 }
564
565 struct dentry *tracefs_failed_creating(struct dentry *dentry)
566 {
567 inode_unlock(d_inode(dentry->d_parent));
568 dput(dentry);
569 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
570 return NULL;
571 }
572
573 struct dentry *tracefs_end_creating(struct dentry *dentry)
574 {
575 inode_unlock(d_inode(dentry->d_parent));
576 return dentry;
577 }
578
579 /* Find the inode that this will use for default */
580 static struct inode *instance_inode(struct dentry *parent, struct inode *inode)
581 {
582 struct tracefs_inode *ti;
583
584 /* If parent is NULL then use root inode */
585 if (!parent)
586 return d_inode(inode->i_sb->s_root);
587
588 /* Find the inode that is flagged as an instance or the root inode */
589 while (!IS_ROOT(parent)) {
590 ti = get_tracefs(d_inode(parent));
591 if (ti->flags & TRACEFS_INSTANCE_INODE)
592 break;
593 parent = parent->d_parent;
594 }
595
596 return d_inode(parent);
597 }
598
599 /**
600 * tracefs_create_file - create a file in the tracefs filesystem
601 * @name: a pointer to a string containing the name of the file to create.
602 * @mode: the permission that the file should have.
603 * @parent: a pointer to the parent dentry for this file. This should be a
604 * directory dentry if set. If this parameter is NULL, then the
605 * file will be created in the root of the tracefs filesystem.
606 * @data: a pointer to something that the caller will want to get to later
607 * on. The inode.i_private pointer will point to this value on
608 * the open() call.
609 * @fops: a pointer to a struct file_operations that should be used for
610 * this file.
611 *
612 * This is the basic "create a file" function for tracefs. It allows for a
613 * wide range of flexibility in creating a file, or a directory (if you want
614 * to create a directory, the tracefs_create_dir() function is
615 * recommended to be used instead.)
616 *
617 * This function will return a pointer to a dentry if it succeeds. This
618 * pointer must be passed to the tracefs_remove() function when the file is
619 * to be removed (no automatic cleanup happens if your module is unloaded,
620 * you are responsible here.) If an error occurs, %NULL will be returned.
621 *
622 * If tracefs is not enabled in the kernel, the value -%ENODEV will be
623 * returned.
624 */
625 struct dentry *tracefs_create_file(const char *name, umode_t mode,
626 struct dentry *parent, void *data,
627 const struct file_operations *fops)
628 {
629 struct tracefs_inode *ti;
630 struct dentry *dentry;
631 struct inode *inode;
632
633 if (security_locked_down(LOCKDOWN_TRACEFS))
634 return NULL;
635
636 if (!(mode & S_IFMT))
637 mode |= S_IFREG;
638 BUG_ON(!S_ISREG(mode));
639 dentry = tracefs_start_creating(name, parent);
640
641 if (IS_ERR(dentry))
642 return NULL;
643
644 inode = tracefs_get_inode(dentry->d_sb);
645 if (unlikely(!inode))
646 return tracefs_failed_creating(dentry);
647
648 ti = get_tracefs(inode);
649 ti->private = instance_inode(parent, inode);
650
651 inode->i_mode = mode;
652 inode->i_op = &tracefs_file_inode_operations;
653 inode->i_fop = fops ? fops : &tracefs_file_operations;
654 inode->i_private = data;
655 inode->i_uid = d_inode(dentry->d_parent)->i_uid;
656 inode->i_gid = d_inode(dentry->d_parent)->i_gid;
657 d_instantiate(dentry, inode);
658 fsnotify_create(d_inode(dentry->d_parent), dentry);
659 return tracefs_end_creating(dentry);
660 }
661
662 static struct dentry *__create_dir(const char *name, struct dentry *parent,
663 const struct inode_operations *ops)
664 {
665 struct tracefs_inode *ti;
666 struct dentry *dentry = tracefs_start_creating(name, parent);
667 struct inode *inode;
668
669 if (IS_ERR(dentry))
670 return NULL;
671
672 inode = tracefs_get_inode(dentry->d_sb);
673 if (unlikely(!inode))
674 return tracefs_failed_creating(dentry);
675
676 /* Do not set bits for OTH */
677 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
678 inode->i_op = ops;
679 inode->i_fop = &simple_dir_operations;
680 inode->i_uid = d_inode(dentry->d_parent)->i_uid;
681 inode->i_gid = d_inode(dentry->d_parent)->i_gid;
682
683 ti = get_tracefs(inode);
684 ti->private = instance_inode(parent, inode);
685
686 /* directory inodes start off with i_nlink == 2 (for "." entry) */
687 inc_nlink(inode);
688 d_instantiate(dentry, inode);
689 inc_nlink(d_inode(dentry->d_parent));
690 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
691 return tracefs_end_creating(dentry);
692 }
693
694 /**
695 * tracefs_create_dir - create a directory in the tracefs filesystem
696 * @name: a pointer to a string containing the name of the directory to
697 * create.
698 * @parent: a pointer to the parent dentry for this file. This should be a
699 * directory dentry if set. If this parameter is NULL, then the
700 * directory will be created in the root of the tracefs filesystem.
701 *
702 * This function creates a directory in tracefs with the given name.
703 *
704 * This function will return a pointer to a dentry if it succeeds. This
705 * pointer must be passed to the tracefs_remove() function when the file is
706 * to be removed. If an error occurs, %NULL will be returned.
707 *
708 * If tracing is not enabled in the kernel, the value -%ENODEV will be
709 * returned.
710 */
711 struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
712 {
713 if (security_locked_down(LOCKDOWN_TRACEFS))
714 return NULL;
715
716 return __create_dir(name, parent, &tracefs_dir_inode_operations);
717 }
718
719 /**
720 * tracefs_create_instance_dir - create the tracing instances directory
721 * @name: The name of the instances directory to create
722 * @parent: The parent directory that the instances directory will exist
723 * @mkdir: The function to call when a mkdir is performed.
724 * @rmdir: The function to call when a rmdir is performed.
725 *
726 * Only one instances directory is allowed.
727 *
728 * The instances directory is special as it allows for mkdir and rmdir
729 * to be done by userspace. When a mkdir or rmdir is performed, the inode
730 * locks are released and the methods passed in (@mkdir and @rmdir) are
731 * called without locks and with the name of the directory being created
732 * within the instances directory.
733 *
734 * Returns the dentry of the instances directory.
735 */
736 __init struct dentry *tracefs_create_instance_dir(const char *name,
737 struct dentry *parent,
738 int (*mkdir)(const char *name),
739 int (*rmdir)(const char *name))
740 {
741 struct dentry *dentry;
742
743 /* Only allow one instance of the instances directory. */
744 if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
745 return NULL;
746
747 dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations);
748 if (!dentry)
749 return NULL;
750
751 tracefs_ops.mkdir = mkdir;
752 tracefs_ops.rmdir = rmdir;
753
754 return dentry;
755 }
756
757 static void remove_one(struct dentry *victim)
758 {
759 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
760 }
761
762 /**
763 * tracefs_remove - recursively removes a directory
764 * @dentry: a pointer to a the dentry of the directory to be removed.
765 *
766 * This function recursively removes a directory tree in tracefs that
767 * was previously created with a call to another tracefs function
768 * (like tracefs_create_file() or variants thereof.)
769 */
770 void tracefs_remove(struct dentry *dentry)
771 {
772 if (IS_ERR_OR_NULL(dentry))
773 return;
774
775 simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
776 simple_recursive_removal(dentry, remove_one);
777 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
778 }
779
780 /**
781 * tracefs_initialized - Tells whether tracefs has been registered
782 */
783 bool tracefs_initialized(void)
784 {
785 return tracefs_registered;
786 }
787
788 static void init_once(void *foo)
789 {
790 struct tracefs_inode *ti = (struct tracefs_inode *) foo;
791
792 /* inode_init_once() calls memset() on the vfs_inode portion */
793 inode_init_once(&ti->vfs_inode);
794
795 /* Zero out the rest */
796 memset_after(ti, 0, vfs_inode);
797 }
798
799 static int __init tracefs_init(void)
800 {
801 int retval;
802
803 tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",
804 sizeof(struct tracefs_inode),
805 0, (SLAB_RECLAIM_ACCOUNT|
806 SLAB_ACCOUNT),
807 init_once);
808 if (!tracefs_inode_cachep)
809 return -ENOMEM;
810
811 retval = sysfs_create_mount_point(kernel_kobj, "tracing");
812 if (retval)
813 return -EINVAL;
814
815 retval = register_filesystem(&trace_fs_type);
816 if (!retval)
817 tracefs_registered = true;
818
819 return retval;
820 }
821 core_initcall(tracefs_init);
822
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