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