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