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/mount.h>
15 #include <linux/kobject.h>
16 #include <linux/namei.h>
17 #include <linux/tracefs.h>
18 #include <linux/fsnotify.h>
19 #include <linux/security.h>
20 #include <linux/seq_file.h>
21 #include <linux/parser.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
tracefs_alloc_inode(struct super_block * sb)40 static struct inode *tracefs_alloc_inode(struct super_block *sb)
41 {
42 struct tracefs_inode *ti;
43 unsigned long flags;
44
45 ti = kmem_cache_alloc(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
tracefs_free_inode_rcu(struct rcu_head * rcu)56 static void tracefs_free_inode_rcu(struct rcu_head *rcu)
57 {
58 struct tracefs_inode *ti;
59
60 ti = container_of(rcu, struct tracefs_inode, rcu);
61 kmem_cache_free(tracefs_inode_cachep, ti);
62 }
63
tracefs_free_inode(struct inode * inode)64 static void tracefs_free_inode(struct inode *inode)
65 {
66 struct tracefs_inode *ti = get_tracefs(inode);
67 unsigned long flags;
68
69 spin_lock_irqsave(&tracefs_inode_lock, flags);
70 list_del_rcu(&ti->list);
71 spin_unlock_irqrestore(&tracefs_inode_lock, flags);
72
73 call_rcu(&ti->rcu, tracefs_free_inode_rcu);
74 }
75
default_read_file(struct file * file,char __user * buf,size_t count,loff_t * ppos)76 static ssize_t default_read_file(struct file *file, char __user *buf,
77 size_t count, loff_t *ppos)
78 {
79 return 0;
80 }
81
default_write_file(struct file * file,const char __user * buf,size_t count,loff_t * ppos)82 static ssize_t default_write_file(struct file *file, const char __user *buf,
83 size_t count, loff_t *ppos)
84 {
85 return count;
86 }
87
88 static const struct file_operations tracefs_file_operations = {
89 .read = default_read_file,
90 .write = default_write_file,
91 .open = simple_open,
92 .llseek = noop_llseek,
93 };
94
95 static struct tracefs_dir_ops {
96 int (*mkdir)(const char *name);
97 int (*rmdir)(const char *name);
98 } tracefs_ops __ro_after_init;
99
get_dname(struct dentry * dentry)100 static char *get_dname(struct dentry *dentry)
101 {
102 const char *dname;
103 char *name;
104 int len = dentry->d_name.len;
105
106 dname = dentry->d_name.name;
107 name = kmalloc(len + 1, GFP_KERNEL);
108 if (!name)
109 return NULL;
110 memcpy(name, dname, len);
111 name[len] = 0;
112 return name;
113 }
114
tracefs_syscall_mkdir(struct mnt_idmap * idmap,struct inode * inode,struct dentry * dentry,umode_t mode)115 static int tracefs_syscall_mkdir(struct mnt_idmap *idmap,
116 struct inode *inode, struct dentry *dentry,
117 umode_t mode)
118 {
119 struct tracefs_inode *ti;
120 char *name;
121 int ret;
122
123 name = get_dname(dentry);
124 if (!name)
125 return -ENOMEM;
126
127 /*
128 * This is a new directory that does not take the default of
129 * the rootfs. It becomes the default permissions for all the
130 * files and directories underneath it.
131 */
132 ti = get_tracefs(inode);
133 ti->flags |= TRACEFS_INSTANCE_INODE;
134 ti->private = inode;
135
136 /*
137 * The mkdir call can call the generic functions that create
138 * the files within the tracefs system. It is up to the individual
139 * mkdir routine to handle races.
140 */
141 inode_unlock(inode);
142 ret = tracefs_ops.mkdir(name);
143 inode_lock(inode);
144
145 kfree(name);
146
147 return ret;
148 }
149
tracefs_syscall_rmdir(struct inode * inode,struct dentry * dentry)150 static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
151 {
152 char *name;
153 int ret;
154
155 name = get_dname(dentry);
156 if (!name)
157 return -ENOMEM;
158
159 /*
160 * The rmdir call can call the generic functions that create
161 * the files within the tracefs system. It is up to the individual
162 * rmdir routine to handle races.
163 * This time we need to unlock not only the parent (inode) but
164 * also the directory that is being deleted.
165 */
166 inode_unlock(inode);
167 inode_unlock(d_inode(dentry));
168
169 ret = tracefs_ops.rmdir(name);
170
171 inode_lock_nested(inode, I_MUTEX_PARENT);
172 inode_lock(d_inode(dentry));
173
174 kfree(name);
175
176 return ret;
177 }
178
set_tracefs_inode_owner(struct inode * inode)179 static void set_tracefs_inode_owner(struct inode *inode)
180 {
181 struct tracefs_inode *ti = get_tracefs(inode);
182 struct inode *root_inode = ti->private;
183 kuid_t uid;
184 kgid_t gid;
185
186 uid = root_inode->i_uid;
187 gid = root_inode->i_gid;
188
189 /*
190 * If the root is not the mount point, then check the root's
191 * permissions. If it was never set, then default to the
192 * mount point.
193 */
194 if (root_inode != d_inode(root_inode->i_sb->s_root)) {
195 struct tracefs_inode *rti;
196
197 rti = get_tracefs(root_inode);
198 root_inode = d_inode(root_inode->i_sb->s_root);
199
200 if (!(rti->flags & TRACEFS_UID_PERM_SET))
201 uid = root_inode->i_uid;
202
203 if (!(rti->flags & TRACEFS_GID_PERM_SET))
204 gid = root_inode->i_gid;
205 }
206
207 /*
208 * If this inode has never been referenced, then update
209 * the permissions to the superblock.
210 */
211 if (!(ti->flags & TRACEFS_UID_PERM_SET))
212 inode->i_uid = uid;
213
214 if (!(ti->flags & TRACEFS_GID_PERM_SET))
215 inode->i_gid = gid;
216 }
217
tracefs_permission(struct mnt_idmap * idmap,struct inode * inode,int mask)218 static int tracefs_permission(struct mnt_idmap *idmap,
219 struct inode *inode, int mask)
220 {
221 set_tracefs_inode_owner(inode);
222 return generic_permission(idmap, inode, mask);
223 }
224
tracefs_getattr(struct mnt_idmap * idmap,const struct path * path,struct kstat * stat,u32 request_mask,unsigned int flags)225 static int tracefs_getattr(struct mnt_idmap *idmap,
226 const struct path *path, struct kstat *stat,
227 u32 request_mask, unsigned int flags)
228 {
229 struct inode *inode = d_backing_inode(path->dentry);
230
231 set_tracefs_inode_owner(inode);
232 generic_fillattr(idmap, request_mask, inode, stat);
233 return 0;
234 }
235
tracefs_setattr(struct mnt_idmap * idmap,struct dentry * dentry,struct iattr * attr)236 static int tracefs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
237 struct iattr *attr)
238 {
239 unsigned int ia_valid = attr->ia_valid;
240 struct inode *inode = d_inode(dentry);
241 struct tracefs_inode *ti = get_tracefs(inode);
242
243 if (ia_valid & ATTR_UID)
244 ti->flags |= TRACEFS_UID_PERM_SET;
245
246 if (ia_valid & ATTR_GID)
247 ti->flags |= TRACEFS_GID_PERM_SET;
248
249 return simple_setattr(idmap, dentry, attr);
250 }
251
252 static const struct inode_operations tracefs_instance_dir_inode_operations = {
253 .lookup = simple_lookup,
254 .mkdir = tracefs_syscall_mkdir,
255 .rmdir = tracefs_syscall_rmdir,
256 .permission = tracefs_permission,
257 .getattr = tracefs_getattr,
258 .setattr = tracefs_setattr,
259 };
260
261 static const struct inode_operations tracefs_dir_inode_operations = {
262 .lookup = simple_lookup,
263 .permission = tracefs_permission,
264 .getattr = tracefs_getattr,
265 .setattr = tracefs_setattr,
266 };
267
268 static const struct inode_operations tracefs_file_inode_operations = {
269 .permission = tracefs_permission,
270 .getattr = tracefs_getattr,
271 .setattr = tracefs_setattr,
272 };
273
tracefs_get_inode(struct super_block * sb)274 struct inode *tracefs_get_inode(struct super_block *sb)
275 {
276 struct inode *inode = new_inode(sb);
277 if (inode) {
278 inode->i_ino = get_next_ino();
279 inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
280 }
281 return inode;
282 }
283
284 struct tracefs_mount_opts {
285 kuid_t uid;
286 kgid_t gid;
287 umode_t mode;
288 /* Opt_* bitfield. */
289 unsigned int opts;
290 };
291
292 enum {
293 Opt_uid,
294 Opt_gid,
295 Opt_mode,
296 Opt_err
297 };
298
299 static const match_table_t tokens = {
300 {Opt_uid, "uid=%u"},
301 {Opt_gid, "gid=%u"},
302 {Opt_mode, "mode=%o"},
303 {Opt_err, NULL}
304 };
305
306 struct tracefs_fs_info {
307 struct tracefs_mount_opts mount_opts;
308 };
309
tracefs_parse_options(char * data,struct tracefs_mount_opts * opts)310 static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
311 {
312 substring_t args[MAX_OPT_ARGS];
313 int option;
314 int token;
315 kuid_t uid;
316 kgid_t gid;
317 char *p;
318
319 opts->opts = 0;
320 opts->mode = TRACEFS_DEFAULT_MODE;
321
322 while ((p = strsep(&data, ",")) != NULL) {
323 if (!*p)
324 continue;
325
326 token = match_token(p, tokens, args);
327 switch (token) {
328 case Opt_uid:
329 if (match_int(&args[0], &option))
330 return -EINVAL;
331 uid = make_kuid(current_user_ns(), option);
332 if (!uid_valid(uid))
333 return -EINVAL;
334 opts->uid = uid;
335 break;
336 case Opt_gid:
337 if (match_int(&args[0], &option))
338 return -EINVAL;
339 gid = make_kgid(current_user_ns(), option);
340 if (!gid_valid(gid))
341 return -EINVAL;
342 opts->gid = gid;
343 break;
344 case Opt_mode:
345 if (match_octal(&args[0], &option))
346 return -EINVAL;
347 opts->mode = option & S_IALLUGO;
348 break;
349 /*
350 * We might like to report bad mount options here;
351 * but traditionally tracefs has ignored all mount options
352 */
353 }
354
355 opts->opts |= BIT(token);
356 }
357
358 return 0;
359 }
360
tracefs_apply_options(struct super_block * sb,bool remount)361 static int tracefs_apply_options(struct super_block *sb, bool remount)
362 {
363 struct tracefs_fs_info *fsi = sb->s_fs_info;
364 struct inode *inode = d_inode(sb->s_root);
365 struct tracefs_mount_opts *opts = &fsi->mount_opts;
366 struct tracefs_inode *ti;
367 bool update_uid, update_gid;
368 umode_t tmp_mode;
369
370 /*
371 * On remount, only reset mode/uid/gid if they were provided as mount
372 * options.
373 */
374
375 if (!remount || opts->opts & BIT(Opt_mode)) {
376 tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;
377 tmp_mode |= opts->mode;
378 WRITE_ONCE(inode->i_mode, tmp_mode);
379 }
380
381 if (!remount || opts->opts & BIT(Opt_uid))
382 inode->i_uid = opts->uid;
383
384 if (!remount || opts->opts & BIT(Opt_gid))
385 inode->i_gid = opts->gid;
386
387 if (remount && (opts->opts & BIT(Opt_uid) || opts->opts & BIT(Opt_gid))) {
388
389 update_uid = opts->opts & BIT(Opt_uid);
390 update_gid = opts->opts & BIT(Opt_gid);
391
392 rcu_read_lock();
393 list_for_each_entry_rcu(ti, &tracefs_inodes, list) {
394 if (update_uid)
395 ti->flags &= ~TRACEFS_UID_PERM_SET;
396
397 if (update_gid)
398 ti->flags &= ~TRACEFS_GID_PERM_SET;
399
400 if (ti->flags & TRACEFS_EVENT_INODE)
401 eventfs_remount(ti, update_uid, update_gid);
402 }
403 rcu_read_unlock();
404 }
405
406 return 0;
407 }
408
tracefs_remount(struct super_block * sb,int * flags,char * data)409 static int tracefs_remount(struct super_block *sb, int *flags, char *data)
410 {
411 int err;
412 struct tracefs_fs_info *fsi = sb->s_fs_info;
413
414 sync_filesystem(sb);
415 err = tracefs_parse_options(data, &fsi->mount_opts);
416 if (err)
417 goto fail;
418
419 tracefs_apply_options(sb, true);
420
421 fail:
422 return err;
423 }
424
tracefs_show_options(struct seq_file * m,struct dentry * root)425 static int tracefs_show_options(struct seq_file *m, struct dentry *root)
426 {
427 struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
428 struct tracefs_mount_opts *opts = &fsi->mount_opts;
429
430 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
431 seq_printf(m, ",uid=%u",
432 from_kuid_munged(&init_user_ns, opts->uid));
433 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
434 seq_printf(m, ",gid=%u",
435 from_kgid_munged(&init_user_ns, opts->gid));
436 if (opts->mode != TRACEFS_DEFAULT_MODE)
437 seq_printf(m, ",mode=%o", opts->mode);
438
439 return 0;
440 }
441
tracefs_drop_inode(struct inode * inode)442 static int tracefs_drop_inode(struct inode *inode)
443 {
444 struct tracefs_inode *ti = get_tracefs(inode);
445
446 /*
447 * This inode is being freed and cannot be used for
448 * eventfs. Clear the flag so that it doesn't call into
449 * eventfs during the remount flag updates. The eventfs_inode
450 * gets freed after an RCU cycle, so the content will still
451 * be safe if the iteration is going on now.
452 */
453 ti->flags &= ~TRACEFS_EVENT_INODE;
454
455 return 1;
456 }
457
458 static const struct super_operations tracefs_super_operations = {
459 .alloc_inode = tracefs_alloc_inode,
460 .free_inode = tracefs_free_inode,
461 .drop_inode = tracefs_drop_inode,
462 .statfs = simple_statfs,
463 .remount_fs = tracefs_remount,
464 .show_options = tracefs_show_options,
465 };
466
467 /*
468 * It would be cleaner if eventfs had its own dentry ops.
469 *
470 * Note that d_revalidate is called potentially under RCU,
471 * so it can't take the eventfs mutex etc. It's fine - if
472 * we open a file just as it's marked dead, things will
473 * still work just fine, and just see the old stale case.
474 */
tracefs_d_release(struct dentry * dentry)475 static void tracefs_d_release(struct dentry *dentry)
476 {
477 if (dentry->d_fsdata)
478 eventfs_d_release(dentry);
479 }
480
tracefs_d_revalidate(struct dentry * dentry,unsigned int flags)481 static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
482 {
483 struct eventfs_inode *ei = dentry->d_fsdata;
484
485 return !(ei && ei->is_freed);
486 }
487
488 static const struct dentry_operations tracefs_dentry_operations = {
489 .d_revalidate = tracefs_d_revalidate,
490 .d_release = tracefs_d_release,
491 };
492
trace_fill_super(struct super_block * sb,void * data,int silent)493 static int trace_fill_super(struct super_block *sb, void *data, int silent)
494 {
495 static const struct tree_descr trace_files[] = {{""}};
496 struct tracefs_fs_info *fsi;
497 int err;
498
499 fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
500 sb->s_fs_info = fsi;
501 if (!fsi) {
502 err = -ENOMEM;
503 goto fail;
504 }
505
506 err = tracefs_parse_options(data, &fsi->mount_opts);
507 if (err)
508 goto fail;
509
510 err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
511 if (err)
512 goto fail;
513
514 sb->s_op = &tracefs_super_operations;
515 sb->s_d_op = &tracefs_dentry_operations;
516
517 tracefs_apply_options(sb, false);
518
519 return 0;
520
521 fail:
522 kfree(fsi);
523 sb->s_fs_info = NULL;
524 return err;
525 }
526
trace_mount(struct file_system_type * fs_type,int flags,const char * dev_name,void * data)527 static struct dentry *trace_mount(struct file_system_type *fs_type,
528 int flags, const char *dev_name,
529 void *data)
530 {
531 return mount_single(fs_type, flags, data, trace_fill_super);
532 }
533
534 static struct file_system_type trace_fs_type = {
535 .owner = THIS_MODULE,
536 .name = "tracefs",
537 .mount = trace_mount,
538 .kill_sb = kill_litter_super,
539 };
540 MODULE_ALIAS_FS("tracefs");
541
tracefs_start_creating(const char * name,struct dentry * parent)542 struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
543 {
544 struct dentry *dentry;
545 int error;
546
547 pr_debug("tracefs: creating file '%s'\n",name);
548
549 error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
550 &tracefs_mount_count);
551 if (error)
552 return ERR_PTR(error);
553
554 /* If the parent is not specified, we create it in the root.
555 * We need the root dentry to do this, which is in the super
556 * block. A pointer to that is in the struct vfsmount that we
557 * have around.
558 */
559 if (!parent)
560 parent = tracefs_mount->mnt_root;
561
562 inode_lock(d_inode(parent));
563 if (unlikely(IS_DEADDIR(d_inode(parent))))
564 dentry = ERR_PTR(-ENOENT);
565 else
566 dentry = lookup_one_len(name, parent, strlen(name));
567 if (!IS_ERR(dentry) && d_inode(dentry)) {
568 dput(dentry);
569 dentry = ERR_PTR(-EEXIST);
570 }
571
572 if (IS_ERR(dentry)) {
573 inode_unlock(d_inode(parent));
574 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
575 }
576
577 return dentry;
578 }
579
tracefs_failed_creating(struct dentry * dentry)580 struct dentry *tracefs_failed_creating(struct dentry *dentry)
581 {
582 inode_unlock(d_inode(dentry->d_parent));
583 dput(dentry);
584 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
585 return NULL;
586 }
587
tracefs_end_creating(struct dentry * dentry)588 struct dentry *tracefs_end_creating(struct dentry *dentry)
589 {
590 inode_unlock(d_inode(dentry->d_parent));
591 return dentry;
592 }
593
594 /* Find the inode that this will use for default */
instance_inode(struct dentry * parent,struct inode * inode)595 static struct inode *instance_inode(struct dentry *parent, struct inode *inode)
596 {
597 struct tracefs_inode *ti;
598
599 /* If parent is NULL then use root inode */
600 if (!parent)
601 return d_inode(inode->i_sb->s_root);
602
603 /* Find the inode that is flagged as an instance or the root inode */
604 while (!IS_ROOT(parent)) {
605 ti = get_tracefs(d_inode(parent));
606 if (ti->flags & TRACEFS_INSTANCE_INODE)
607 break;
608 parent = parent->d_parent;
609 }
610
611 return d_inode(parent);
612 }
613
614 /**
615 * tracefs_create_file - create a file in the tracefs filesystem
616 * @name: a pointer to a string containing the name of the file to create.
617 * @mode: the permission that the file should have.
618 * @parent: a pointer to the parent dentry for this file. This should be a
619 * directory dentry if set. If this parameter is NULL, then the
620 * file will be created in the root of the tracefs filesystem.
621 * @data: a pointer to something that the caller will want to get to later
622 * on. The inode.i_private pointer will point to this value on
623 * the open() call.
624 * @fops: a pointer to a struct file_operations that should be used for
625 * this file.
626 *
627 * This is the basic "create a file" function for tracefs. It allows for a
628 * wide range of flexibility in creating a file, or a directory (if you want
629 * to create a directory, the tracefs_create_dir() function is
630 * recommended to be used instead.)
631 *
632 * This function will return a pointer to a dentry if it succeeds. This
633 * pointer must be passed to the tracefs_remove() function when the file is
634 * to be removed (no automatic cleanup happens if your module is unloaded,
635 * you are responsible here.) If an error occurs, %NULL will be returned.
636 *
637 * If tracefs is not enabled in the kernel, the value -%ENODEV will be
638 * returned.
639 */
tracefs_create_file(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops)640 struct dentry *tracefs_create_file(const char *name, umode_t mode,
641 struct dentry *parent, void *data,
642 const struct file_operations *fops)
643 {
644 struct tracefs_inode *ti;
645 struct dentry *dentry;
646 struct inode *inode;
647
648 if (security_locked_down(LOCKDOWN_TRACEFS))
649 return NULL;
650
651 if (!(mode & S_IFMT))
652 mode |= S_IFREG;
653 BUG_ON(!S_ISREG(mode));
654 dentry = tracefs_start_creating(name, parent);
655
656 if (IS_ERR(dentry))
657 return NULL;
658
659 inode = tracefs_get_inode(dentry->d_sb);
660 if (unlikely(!inode))
661 return tracefs_failed_creating(dentry);
662
663 ti = get_tracefs(inode);
664 ti->private = instance_inode(parent, inode);
665
666 inode->i_mode = mode;
667 inode->i_op = &tracefs_file_inode_operations;
668 inode->i_fop = fops ? fops : &tracefs_file_operations;
669 inode->i_private = data;
670 inode->i_uid = d_inode(dentry->d_parent)->i_uid;
671 inode->i_gid = d_inode(dentry->d_parent)->i_gid;
672 d_instantiate(dentry, inode);
673 fsnotify_create(d_inode(dentry->d_parent), dentry);
674 return tracefs_end_creating(dentry);
675 }
676
__create_dir(const char * name,struct dentry * parent,const struct inode_operations * ops)677 static struct dentry *__create_dir(const char *name, struct dentry *parent,
678 const struct inode_operations *ops)
679 {
680 struct tracefs_inode *ti;
681 struct dentry *dentry = tracefs_start_creating(name, parent);
682 struct inode *inode;
683
684 if (IS_ERR(dentry))
685 return NULL;
686
687 inode = tracefs_get_inode(dentry->d_sb);
688 if (unlikely(!inode))
689 return tracefs_failed_creating(dentry);
690
691 /* Do not set bits for OTH */
692 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
693 inode->i_op = ops;
694 inode->i_fop = &simple_dir_operations;
695 inode->i_uid = d_inode(dentry->d_parent)->i_uid;
696 inode->i_gid = d_inode(dentry->d_parent)->i_gid;
697
698 ti = get_tracefs(inode);
699 ti->private = instance_inode(parent, inode);
700
701 /* directory inodes start off with i_nlink == 2 (for "." entry) */
702 inc_nlink(inode);
703 d_instantiate(dentry, inode);
704 inc_nlink(d_inode(dentry->d_parent));
705 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
706 return tracefs_end_creating(dentry);
707 }
708
709 /**
710 * tracefs_create_dir - create a directory in the tracefs filesystem
711 * @name: a pointer to a string containing the name of the directory to
712 * create.
713 * @parent: a pointer to the parent dentry for this file. This should be a
714 * directory dentry if set. If this parameter is NULL, then the
715 * directory will be created in the root of the tracefs filesystem.
716 *
717 * This function creates a directory in tracefs with the given name.
718 *
719 * This function will return a pointer to a dentry if it succeeds. This
720 * pointer must be passed to the tracefs_remove() function when the file is
721 * to be removed. If an error occurs, %NULL will be returned.
722 *
723 * If tracing is not enabled in the kernel, the value -%ENODEV will be
724 * returned.
725 */
tracefs_create_dir(const char * name,struct dentry * parent)726 struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
727 {
728 if (security_locked_down(LOCKDOWN_TRACEFS))
729 return NULL;
730
731 return __create_dir(name, parent, &tracefs_dir_inode_operations);
732 }
733
734 /**
735 * tracefs_create_instance_dir - create the tracing instances directory
736 * @name: The name of the instances directory to create
737 * @parent: The parent directory that the instances directory will exist
738 * @mkdir: The function to call when a mkdir is performed.
739 * @rmdir: The function to call when a rmdir is performed.
740 *
741 * Only one instances directory is allowed.
742 *
743 * The instances directory is special as it allows for mkdir and rmdir
744 * to be done by userspace. When a mkdir or rmdir is performed, the inode
745 * locks are released and the methods passed in (@mkdir and @rmdir) are
746 * called without locks and with the name of the directory being created
747 * within the instances directory.
748 *
749 * Returns the dentry of the instances directory.
750 */
tracefs_create_instance_dir(const char * name,struct dentry * parent,int (* mkdir)(const char * name),int (* rmdir)(const char * name))751 __init struct dentry *tracefs_create_instance_dir(const char *name,
752 struct dentry *parent,
753 int (*mkdir)(const char *name),
754 int (*rmdir)(const char *name))
755 {
756 struct dentry *dentry;
757
758 /* Only allow one instance of the instances directory. */
759 if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
760 return NULL;
761
762 dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations);
763 if (!dentry)
764 return NULL;
765
766 tracefs_ops.mkdir = mkdir;
767 tracefs_ops.rmdir = rmdir;
768
769 return dentry;
770 }
771
remove_one(struct dentry * victim)772 static void remove_one(struct dentry *victim)
773 {
774 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
775 }
776
777 /**
778 * tracefs_remove - recursively removes a directory
779 * @dentry: a pointer to a the dentry of the directory to be removed.
780 *
781 * This function recursively removes a directory tree in tracefs that
782 * was previously created with a call to another tracefs function
783 * (like tracefs_create_file() or variants thereof.)
784 */
tracefs_remove(struct dentry * dentry)785 void tracefs_remove(struct dentry *dentry)
786 {
787 if (IS_ERR_OR_NULL(dentry))
788 return;
789
790 simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
791 simple_recursive_removal(dentry, remove_one);
792 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
793 }
794
795 /**
796 * tracefs_initialized - Tells whether tracefs has been registered
797 */
tracefs_initialized(void)798 bool tracefs_initialized(void)
799 {
800 return tracefs_registered;
801 }
802
init_once(void * foo)803 static void init_once(void *foo)
804 {
805 struct tracefs_inode *ti = (struct tracefs_inode *) foo;
806
807 /* inode_init_once() calls memset() on the vfs_inode portion */
808 inode_init_once(&ti->vfs_inode);
809
810 /* Zero out the rest */
811 memset_after(ti, 0, vfs_inode);
812 }
813
tracefs_init(void)814 static int __init tracefs_init(void)
815 {
816 int retval;
817
818 tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",
819 sizeof(struct tracefs_inode),
820 0, (SLAB_RECLAIM_ACCOUNT|
821 SLAB_MEM_SPREAD|
822 SLAB_ACCOUNT),
823 init_once);
824 if (!tracefs_inode_cachep)
825 return -ENOMEM;
826
827 retval = sysfs_create_mount_point(kernel_kobj, "tracing");
828 if (retval)
829 return -EINVAL;
830
831 retval = register_filesystem(&trace_fs_type);
832 if (!retval)
833 tracefs_registered = true;
834
835 return retval;
836 }
837 core_initcall(tracefs_init);
838