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
 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 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
112static 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
147static 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
176static 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
215static 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
222static 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
233static 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
249static 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
258static 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
265static const struct inode_operations tracefs_file_inode_operations = {
266	.permission	= tracefs_permission,
267	.getattr	= tracefs_getattr,
268	.setattr	= tracefs_setattr,
269};
270
271struct 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
281struct tracefs_fs_info {
282	kuid_t uid;
283	kgid_t gid;
284	umode_t mode;
285	/* Opt_* bitfield. */
286	unsigned int opts;
287};
288
289enum {
290	Opt_uid,
291	Opt_gid,
292	Opt_mode,
 
293};
294
295static 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
302static 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
333static 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
389static 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	if (!new_opts)
396		return 0;
397
398	sync_filesystem(sb);
399	/* structure copy of new mount options to sb */
400	*sb_opts = *new_opts;
 
 
 
401
402	return tracefs_apply_options(sb, true);
 
403}
404
405static int tracefs_show_options(struct seq_file *m, struct dentry *root)
406{
407	struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
 
408
409	if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
410		seq_printf(m, ",uid=%u",
411			   from_kuid_munged(&init_user_ns, fsi->uid));
412	if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
413		seq_printf(m, ",gid=%u",
414			   from_kgid_munged(&init_user_ns, fsi->gid));
415	if (fsi->mode != TRACEFS_DEFAULT_MODE)
416		seq_printf(m, ",mode=%o", fsi->mode);
417
418	return 0;
419}
420
421static int tracefs_drop_inode(struct inode *inode)
422{
423	struct tracefs_inode *ti = get_tracefs(inode);
424
425	/*
426	 * This inode is being freed and cannot be used for
427	 * eventfs. Clear the flag so that it doesn't call into
428	 * eventfs during the remount flag updates. The eventfs_inode
429	 * gets freed after an RCU cycle, so the content will still
430	 * be safe if the iteration is going on now.
431	 */
432	ti->flags &= ~TRACEFS_EVENT_INODE;
433
434	return 1;
435}
436
437static const struct super_operations tracefs_super_operations = {
438	.alloc_inode    = tracefs_alloc_inode,
439	.free_inode     = tracefs_free_inode,
440	.destroy_inode  = tracefs_destroy_inode,
441	.drop_inode     = tracefs_drop_inode,
442	.statfs		= simple_statfs,
 
443	.show_options	= tracefs_show_options,
444};
445
446/*
447 * It would be cleaner if eventfs had its own dentry ops.
448 *
449 * Note that d_revalidate is called potentially under RCU,
450 * so it can't take the eventfs mutex etc. It's fine - if
451 * we open a file just as it's marked dead, things will
452 * still work just fine, and just see the old stale case.
453 */
454static void tracefs_d_release(struct dentry *dentry)
455{
456	if (dentry->d_fsdata)
457		eventfs_d_release(dentry);
458}
459
460static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
461{
462	struct eventfs_inode *ei = dentry->d_fsdata;
463
464	return !(ei && ei->is_freed);
465}
466
467static const struct dentry_operations tracefs_dentry_operations = {
468	.d_revalidate = tracefs_d_revalidate,
469	.d_release = tracefs_d_release,
470};
471
472static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc)
473{
474	static const struct tree_descr trace_files[] = {{""}};
 
475	int err;
476
477	err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
478	if (err)
479		return err;
 
 
 
480
481	sb->s_op = &tracefs_super_operations;
482	sb->s_d_op = &tracefs_dentry_operations;
 
483
484	return 0;
485}
 
486
487static int tracefs_get_tree(struct fs_context *fc)
488{
489	int err = get_tree_single(fc, tracefs_fill_super);
490
491	if (err)
492		return err;
493
494	return tracefs_reconfigure(fc);
495}
496
497static void tracefs_free_fc(struct fs_context *fc)
498{
499	kfree(fc->s_fs_info);
 
500}
501
502static const struct fs_context_operations tracefs_context_ops = {
503	.free		= tracefs_free_fc,
504	.parse_param	= tracefs_parse_param,
505	.get_tree	= tracefs_get_tree,
506	.reconfigure	= tracefs_reconfigure,
507};
508
509static int tracefs_init_fs_context(struct fs_context *fc)
510{
511	struct tracefs_fs_info *fsi;
512
513	fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
514	if (!fsi)
515		return -ENOMEM;
516
517	fsi->mode = TRACEFS_DEFAULT_MODE;
518
519	fc->s_fs_info = fsi;
520	fc->ops = &tracefs_context_ops;
521	return 0;
522}
523
524static struct file_system_type trace_fs_type = {
525	.owner =	THIS_MODULE,
526	.name =		"tracefs",
527	.init_fs_context = tracefs_init_fs_context,
528	.parameters	= tracefs_param_specs,
529	.kill_sb =	kill_litter_super,
530};
531MODULE_ALIAS_FS("tracefs");
532
533struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
534{
535	struct dentry *dentry;
536	int error;
537
538	pr_debug("tracefs: creating file '%s'\n",name);
539
540	error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
541			      &tracefs_mount_count);
542	if (error)
543		return ERR_PTR(error);
544
545	/* If the parent is not specified, we create it in the root.
546	 * We need the root dentry to do this, which is in the super
547	 * block. A pointer to that is in the struct vfsmount that we
548	 * have around.
549	 */
550	if (!parent)
551		parent = tracefs_mount->mnt_root;
552
553	inode_lock(d_inode(parent));
554	if (unlikely(IS_DEADDIR(d_inode(parent))))
555		dentry = ERR_PTR(-ENOENT);
556	else
557		dentry = lookup_one_len(name, parent, strlen(name));
558	if (!IS_ERR(dentry) && d_inode(dentry)) {
559		dput(dentry);
560		dentry = ERR_PTR(-EEXIST);
561	}
562
563	if (IS_ERR(dentry)) {
564		inode_unlock(d_inode(parent));
565		simple_release_fs(&tracefs_mount, &tracefs_mount_count);
566	}
567
568	return dentry;
569}
570
571struct dentry *tracefs_failed_creating(struct dentry *dentry)
572{
573	inode_unlock(d_inode(dentry->d_parent));
574	dput(dentry);
575	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
576	return NULL;
577}
578
579struct dentry *tracefs_end_creating(struct dentry *dentry)
580{
581	inode_unlock(d_inode(dentry->d_parent));
582	return dentry;
583}
584
585/* Find the inode that this will use for default */
586static struct inode *instance_inode(struct dentry *parent, struct inode *inode)
587{
588	struct tracefs_inode *ti;
589
590	/* If parent is NULL then use root inode */
591	if (!parent)
592		return d_inode(inode->i_sb->s_root);
593
594	/* Find the inode that is flagged as an instance or the root inode */
595	while (!IS_ROOT(parent)) {
596		ti = get_tracefs(d_inode(parent));
597		if (ti->flags & TRACEFS_INSTANCE_INODE)
598			break;
599		parent = parent->d_parent;
600	}
601
602	return d_inode(parent);
603}
604
605/**
606 * tracefs_create_file - create a file in the tracefs filesystem
607 * @name: a pointer to a string containing the name of the file to create.
608 * @mode: the permission that the file should have.
609 * @parent: a pointer to the parent dentry for this file.  This should be a
610 *          directory dentry if set.  If this parameter is NULL, then the
611 *          file will be created in the root of the tracefs filesystem.
612 * @data: a pointer to something that the caller will want to get to later
613 *        on.  The inode.i_private pointer will point to this value on
614 *        the open() call.
615 * @fops: a pointer to a struct file_operations that should be used for
616 *        this file.
617 *
618 * This is the basic "create a file" function for tracefs.  It allows for a
619 * wide range of flexibility in creating a file, or a directory (if you want
620 * to create a directory, the tracefs_create_dir() function is
621 * recommended to be used instead.)
622 *
623 * This function will return a pointer to a dentry if it succeeds.  This
624 * pointer must be passed to the tracefs_remove() function when the file is
625 * to be removed (no automatic cleanup happens if your module is unloaded,
626 * you are responsible here.)  If an error occurs, %NULL will be returned.
627 *
628 * If tracefs is not enabled in the kernel, the value -%ENODEV will be
629 * returned.
630 */
631struct dentry *tracefs_create_file(const char *name, umode_t mode,
632				   struct dentry *parent, void *data,
633				   const struct file_operations *fops)
634{
635	struct tracefs_inode *ti;
636	struct dentry *dentry;
637	struct inode *inode;
638
639	if (security_locked_down(LOCKDOWN_TRACEFS))
640		return NULL;
641
642	if (!(mode & S_IFMT))
643		mode |= S_IFREG;
644	BUG_ON(!S_ISREG(mode));
645	dentry = tracefs_start_creating(name, parent);
646
647	if (IS_ERR(dentry))
648		return NULL;
649
650	inode = tracefs_get_inode(dentry->d_sb);
651	if (unlikely(!inode))
652		return tracefs_failed_creating(dentry);
653
654	ti = get_tracefs(inode);
655	ti->private = instance_inode(parent, inode);
656
657	inode->i_mode = mode;
658	inode->i_op = &tracefs_file_inode_operations;
659	inode->i_fop = fops ? fops : &tracefs_file_operations;
660	inode->i_private = data;
661	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
662	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
663	d_instantiate(dentry, inode);
664	fsnotify_create(d_inode(dentry->d_parent), dentry);
665	return tracefs_end_creating(dentry);
666}
667
668static struct dentry *__create_dir(const char *name, struct dentry *parent,
669				   const struct inode_operations *ops)
670{
671	struct tracefs_inode *ti;
672	struct dentry *dentry = tracefs_start_creating(name, parent);
673	struct inode *inode;
674
675	if (IS_ERR(dentry))
676		return NULL;
677
678	inode = tracefs_get_inode(dentry->d_sb);
679	if (unlikely(!inode))
680		return tracefs_failed_creating(dentry);
681
682	/* Do not set bits for OTH */
683	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
684	inode->i_op = ops;
685	inode->i_fop = &simple_dir_operations;
686	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
687	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
688
689	ti = get_tracefs(inode);
690	ti->private = instance_inode(parent, inode);
691
692	/* directory inodes start off with i_nlink == 2 (for "." entry) */
693	inc_nlink(inode);
694	d_instantiate(dentry, inode);
695	inc_nlink(d_inode(dentry->d_parent));
696	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
697	return tracefs_end_creating(dentry);
698}
699
700/**
701 * tracefs_create_dir - create a directory in the tracefs filesystem
702 * @name: a pointer to a string containing the name of the directory to
703 *        create.
704 * @parent: a pointer to the parent dentry for this file.  This should be a
705 *          directory dentry if set.  If this parameter is NULL, then the
706 *          directory will be created in the root of the tracefs filesystem.
707 *
708 * This function creates a directory in tracefs with the given name.
709 *
710 * This function will return a pointer to a dentry if it succeeds.  This
711 * pointer must be passed to the tracefs_remove() function when the file is
712 * to be removed. If an error occurs, %NULL will be returned.
713 *
714 * If tracing is not enabled in the kernel, the value -%ENODEV will be
715 * returned.
716 */
717struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
718{
719	if (security_locked_down(LOCKDOWN_TRACEFS))
720		return NULL;
721
722	return __create_dir(name, parent, &tracefs_dir_inode_operations);
723}
724
725/**
726 * tracefs_create_instance_dir - create the tracing instances directory
727 * @name: The name of the instances directory to create
728 * @parent: The parent directory that the instances directory will exist
729 * @mkdir: The function to call when a mkdir is performed.
730 * @rmdir: The function to call when a rmdir is performed.
731 *
732 * Only one instances directory is allowed.
733 *
734 * The instances directory is special as it allows for mkdir and rmdir
735 * to be done by userspace. When a mkdir or rmdir is performed, the inode
736 * locks are released and the methods passed in (@mkdir and @rmdir) are
737 * called without locks and with the name of the directory being created
738 * within the instances directory.
739 *
740 * Returns the dentry of the instances directory.
741 */
742__init struct dentry *tracefs_create_instance_dir(const char *name,
743					  struct dentry *parent,
744					  int (*mkdir)(const char *name),
745					  int (*rmdir)(const char *name))
746{
747	struct dentry *dentry;
748
749	/* Only allow one instance of the instances directory. */
750	if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
751		return NULL;
752
753	dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations);
754	if (!dentry)
755		return NULL;
756
757	tracefs_ops.mkdir = mkdir;
758	tracefs_ops.rmdir = rmdir;
759
760	return dentry;
761}
762
763static void remove_one(struct dentry *victim)
764{
765	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
766}
767
768/**
769 * tracefs_remove - recursively removes a directory
770 * @dentry: a pointer to a the dentry of the directory to be removed.
771 *
772 * This function recursively removes a directory tree in tracefs that
773 * was previously created with a call to another tracefs function
774 * (like tracefs_create_file() or variants thereof.)
775 */
776void tracefs_remove(struct dentry *dentry)
777{
778	if (IS_ERR_OR_NULL(dentry))
779		return;
780
781	simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
782	simple_recursive_removal(dentry, remove_one);
783	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
784}
785
786/**
787 * tracefs_initialized - Tells whether tracefs has been registered
788 */
789bool tracefs_initialized(void)
790{
791	return tracefs_registered;
792}
793
794static void init_once(void *foo)
795{
796	struct tracefs_inode *ti = (struct tracefs_inode *) foo;
797
798	/* inode_init_once() calls memset() on the vfs_inode portion */
799	inode_init_once(&ti->vfs_inode);
800
801	/* Zero out the rest */
802	memset_after(ti, 0, vfs_inode);
803}
804
805static int __init tracefs_init(void)
806{
807	int retval;
808
809	tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",
810						 sizeof(struct tracefs_inode),
811						 0, (SLAB_RECLAIM_ACCOUNT|
812						     SLAB_ACCOUNT),
813						 init_once);
814	if (!tracefs_inode_cachep)
815		return -ENOMEM;
816
817	retval = sysfs_create_mount_point(kernel_kobj, "tracing");
818	if (retval)
819		return -EINVAL;
820
821	retval = register_filesystem(&trace_fs_type);
822	if (!retval)
823		tracefs_registered = true;
824
825	return retval;
826}
827core_initcall(tracefs_init);