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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);
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
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 = 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
56static 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
64static 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
76static ssize_t default_read_file(struct file *file, char __user *buf,
77 size_t count, loff_t *ppos)
78{
79 return 0;
80}
81
82static 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
88static 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
95static struct tracefs_dir_ops {
96 int (*mkdir)(const char *name);
97 int (*rmdir)(const char *name);
98} tracefs_ops __ro_after_init;
99
100static 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
115static 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
150static 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
179static 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
218static 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
225static 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
236static 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
252static 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
261static 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
268static const struct inode_operations tracefs_file_inode_operations = {
269 .permission = tracefs_permission,
270 .getattr = tracefs_getattr,
271 .setattr = tracefs_setattr,
272};
273
274struct 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 simple_inode_init_ts(inode);
280 }
281 return inode;
282}
283
284struct tracefs_mount_opts {
285 kuid_t uid;
286 kgid_t gid;
287 umode_t mode;
288 /* Opt_* bitfield. */
289 unsigned int opts;
290};
291
292enum {
293 Opt_uid,
294 Opt_gid,
295 Opt_mode,
296 Opt_err
297};
298
299static 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
306struct tracefs_fs_info {
307 struct tracefs_mount_opts mount_opts;
308};
309
310static 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
361static 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
409static 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
421fail:
422 return err;
423}
424
425static 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
442static const struct super_operations tracefs_super_operations = {
443 .alloc_inode = tracefs_alloc_inode,
444 .free_inode = tracefs_free_inode,
445 .drop_inode = generic_delete_inode,
446 .statfs = simple_statfs,
447 .remount_fs = tracefs_remount,
448 .show_options = tracefs_show_options,
449};
450
451/*
452 * It would be cleaner if eventfs had its own dentry ops.
453 *
454 * Note that d_revalidate is called potentially under RCU,
455 * so it can't take the eventfs mutex etc. It's fine - if
456 * we open a file just as it's marked dead, things will
457 * still work just fine, and just see the old stale case.
458 */
459static void tracefs_d_release(struct dentry *dentry)
460{
461 if (dentry->d_fsdata)
462 eventfs_d_release(dentry);
463}
464
465static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
466{
467 struct eventfs_inode *ei = dentry->d_fsdata;
468
469 return !(ei && ei->is_freed);
470}
471
472static void tracefs_d_iput(struct dentry *dentry, struct inode *inode)
473{
474 struct tracefs_inode *ti = get_tracefs(inode);
475
476 /*
477 * This inode is being freed and cannot be used for
478 * eventfs. Clear the flag so that it doesn't call into
479 * eventfs during the remount flag updates. The eventfs_inode
480 * gets freed after an RCU cycle, so the content will still
481 * be safe if the iteration is going on now.
482 */
483 ti->flags &= ~TRACEFS_EVENT_INODE;
484}
485
486static const struct dentry_operations tracefs_dentry_operations = {
487 .d_iput = tracefs_d_iput,
488 .d_revalidate = tracefs_d_revalidate,
489 .d_release = tracefs_d_release,
490};
491
492static int trace_fill_super(struct super_block *sb, void *data, int silent)
493{
494 static const struct tree_descr trace_files[] = {{""}};
495 struct tracefs_fs_info *fsi;
496 int err;
497
498 fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
499 sb->s_fs_info = fsi;
500 if (!fsi) {
501 err = -ENOMEM;
502 goto fail;
503 }
504
505 err = tracefs_parse_options(data, &fsi->mount_opts);
506 if (err)
507 goto fail;
508
509 err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
510 if (err)
511 goto fail;
512
513 sb->s_op = &tracefs_super_operations;
514 sb->s_d_op = &tracefs_dentry_operations;
515
516 tracefs_apply_options(sb, false);
517
518 return 0;
519
520fail:
521 kfree(fsi);
522 sb->s_fs_info = NULL;
523 return err;
524}
525
526static struct dentry *trace_mount(struct file_system_type *fs_type,
527 int flags, const char *dev_name,
528 void *data)
529{
530 return mount_single(fs_type, flags, data, trace_fill_super);
531}
532
533static struct file_system_type trace_fs_type = {
534 .owner = THIS_MODULE,
535 .name = "tracefs",
536 .mount = trace_mount,
537 .kill_sb = kill_litter_super,
538};
539MODULE_ALIAS_FS("tracefs");
540
541struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
542{
543 struct dentry *dentry;
544 int error;
545
546 pr_debug("tracefs: creating file '%s'\n",name);
547
548 error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
549 &tracefs_mount_count);
550 if (error)
551 return ERR_PTR(error);
552
553 /* If the parent is not specified, we create it in the root.
554 * We need the root dentry to do this, which is in the super
555 * block. A pointer to that is in the struct vfsmount that we
556 * have around.
557 */
558 if (!parent)
559 parent = tracefs_mount->mnt_root;
560
561 inode_lock(d_inode(parent));
562 if (unlikely(IS_DEADDIR(d_inode(parent))))
563 dentry = ERR_PTR(-ENOENT);
564 else
565 dentry = lookup_one_len(name, parent, strlen(name));
566 if (!IS_ERR(dentry) && d_inode(dentry)) {
567 dput(dentry);
568 dentry = ERR_PTR(-EEXIST);
569 }
570
571 if (IS_ERR(dentry)) {
572 inode_unlock(d_inode(parent));
573 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
574 }
575
576 return dentry;
577}
578
579struct dentry *tracefs_failed_creating(struct dentry *dentry)
580{
581 inode_unlock(d_inode(dentry->d_parent));
582 dput(dentry);
583 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
584 return NULL;
585}
586
587struct dentry *tracefs_end_creating(struct dentry *dentry)
588{
589 inode_unlock(d_inode(dentry->d_parent));
590 return dentry;
591}
592
593/* Find the inode that this will use for default */
594static struct inode *instance_inode(struct dentry *parent, struct inode *inode)
595{
596 struct tracefs_inode *ti;
597
598 /* If parent is NULL then use root inode */
599 if (!parent)
600 return d_inode(inode->i_sb->s_root);
601
602 /* Find the inode that is flagged as an instance or the root inode */
603 while (!IS_ROOT(parent)) {
604 ti = get_tracefs(d_inode(parent));
605 if (ti->flags & TRACEFS_INSTANCE_INODE)
606 break;
607 parent = parent->d_parent;
608 }
609
610 return d_inode(parent);
611}
612
613/**
614 * tracefs_create_file - create a file in the tracefs filesystem
615 * @name: a pointer to a string containing the name of the file to create.
616 * @mode: the permission that the file should have.
617 * @parent: a pointer to the parent dentry for this file. This should be a
618 * directory dentry if set. If this parameter is NULL, then the
619 * file will be created in the root of the tracefs filesystem.
620 * @data: a pointer to something that the caller will want to get to later
621 * on. The inode.i_private pointer will point to this value on
622 * the open() call.
623 * @fops: a pointer to a struct file_operations that should be used for
624 * this file.
625 *
626 * This is the basic "create a file" function for tracefs. It allows for a
627 * wide range of flexibility in creating a file, or a directory (if you want
628 * to create a directory, the tracefs_create_dir() function is
629 * recommended to be used instead.)
630 *
631 * This function will return a pointer to a dentry if it succeeds. This
632 * pointer must be passed to the tracefs_remove() function when the file is
633 * to be removed (no automatic cleanup happens if your module is unloaded,
634 * you are responsible here.) If an error occurs, %NULL will be returned.
635 *
636 * If tracefs is not enabled in the kernel, the value -%ENODEV will be
637 * returned.
638 */
639struct dentry *tracefs_create_file(const char *name, umode_t mode,
640 struct dentry *parent, void *data,
641 const struct file_operations *fops)
642{
643 struct tracefs_inode *ti;
644 struct dentry *dentry;
645 struct inode *inode;
646
647 if (security_locked_down(LOCKDOWN_TRACEFS))
648 return NULL;
649
650 if (!(mode & S_IFMT))
651 mode |= S_IFREG;
652 BUG_ON(!S_ISREG(mode));
653 dentry = tracefs_start_creating(name, parent);
654
655 if (IS_ERR(dentry))
656 return NULL;
657
658 inode = tracefs_get_inode(dentry->d_sb);
659 if (unlikely(!inode))
660 return tracefs_failed_creating(dentry);
661
662 ti = get_tracefs(inode);
663 ti->private = instance_inode(parent, inode);
664
665 inode->i_mode = mode;
666 inode->i_op = &tracefs_file_inode_operations;
667 inode->i_fop = fops ? fops : &tracefs_file_operations;
668 inode->i_private = data;
669 inode->i_uid = d_inode(dentry->d_parent)->i_uid;
670 inode->i_gid = d_inode(dentry->d_parent)->i_gid;
671 d_instantiate(dentry, inode);
672 fsnotify_create(d_inode(dentry->d_parent), dentry);
673 return tracefs_end_creating(dentry);
674}
675
676static struct dentry *__create_dir(const char *name, struct dentry *parent,
677 const struct inode_operations *ops)
678{
679 struct tracefs_inode *ti;
680 struct dentry *dentry = tracefs_start_creating(name, parent);
681 struct inode *inode;
682
683 if (IS_ERR(dentry))
684 return NULL;
685
686 inode = tracefs_get_inode(dentry->d_sb);
687 if (unlikely(!inode))
688 return tracefs_failed_creating(dentry);
689
690 /* Do not set bits for OTH */
691 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
692 inode->i_op = ops;
693 inode->i_fop = &simple_dir_operations;
694 inode->i_uid = d_inode(dentry->d_parent)->i_uid;
695 inode->i_gid = d_inode(dentry->d_parent)->i_gid;
696
697 ti = get_tracefs(inode);
698 ti->private = instance_inode(parent, inode);
699
700 /* directory inodes start off with i_nlink == 2 (for "." entry) */
701 inc_nlink(inode);
702 d_instantiate(dentry, inode);
703 inc_nlink(d_inode(dentry->d_parent));
704 fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
705 return tracefs_end_creating(dentry);
706}
707
708/**
709 * tracefs_create_dir - create a directory in the tracefs filesystem
710 * @name: a pointer to a string containing the name of the directory to
711 * create.
712 * @parent: a pointer to the parent dentry for this file. This should be a
713 * directory dentry if set. If this parameter is NULL, then the
714 * directory will be created in the root of the tracefs filesystem.
715 *
716 * This function creates a directory in tracefs with the given name.
717 *
718 * This function will return a pointer to a dentry if it succeeds. This
719 * pointer must be passed to the tracefs_remove() function when the file is
720 * to be removed. If an error occurs, %NULL will be returned.
721 *
722 * If tracing is not enabled in the kernel, the value -%ENODEV will be
723 * returned.
724 */
725struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
726{
727 if (security_locked_down(LOCKDOWN_TRACEFS))
728 return NULL;
729
730 return __create_dir(name, parent, &tracefs_dir_inode_operations);
731}
732
733/**
734 * tracefs_create_instance_dir - create the tracing instances directory
735 * @name: The name of the instances directory to create
736 * @parent: The parent directory that the instances directory will exist
737 * @mkdir: The function to call when a mkdir is performed.
738 * @rmdir: The function to call when a rmdir is performed.
739 *
740 * Only one instances directory is allowed.
741 *
742 * The instances directory is special as it allows for mkdir and rmdir
743 * to be done by userspace. When a mkdir or rmdir is performed, the inode
744 * locks are released and the methods passed in (@mkdir and @rmdir) are
745 * called without locks and with the name of the directory being created
746 * within the instances directory.
747 *
748 * Returns the dentry of the instances directory.
749 */
750__init struct dentry *tracefs_create_instance_dir(const char *name,
751 struct dentry *parent,
752 int (*mkdir)(const char *name),
753 int (*rmdir)(const char *name))
754{
755 struct dentry *dentry;
756
757 /* Only allow one instance of the instances directory. */
758 if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
759 return NULL;
760
761 dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations);
762 if (!dentry)
763 return NULL;
764
765 tracefs_ops.mkdir = mkdir;
766 tracefs_ops.rmdir = rmdir;
767
768 return dentry;
769}
770
771static void remove_one(struct dentry *victim)
772{
773 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
774}
775
776/**
777 * tracefs_remove - recursively removes a directory
778 * @dentry: a pointer to a the dentry of the directory to be removed.
779 *
780 * This function recursively removes a directory tree in tracefs that
781 * was previously created with a call to another tracefs function
782 * (like tracefs_create_file() or variants thereof.)
783 */
784void tracefs_remove(struct dentry *dentry)
785{
786 if (IS_ERR_OR_NULL(dentry))
787 return;
788
789 simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
790 simple_recursive_removal(dentry, remove_one);
791 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
792}
793
794/**
795 * tracefs_initialized - Tells whether tracefs has been registered
796 */
797bool tracefs_initialized(void)
798{
799 return tracefs_registered;
800}
801
802static void init_once(void *foo)
803{
804 struct tracefs_inode *ti = (struct tracefs_inode *) foo;
805
806 /* inode_init_once() calls memset() on the vfs_inode portion */
807 inode_init_once(&ti->vfs_inode);
808
809 /* Zero out the rest */
810 memset_after(ti, 0, vfs_inode);
811}
812
813static int __init tracefs_init(void)
814{
815 int retval;
816
817 tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache",
818 sizeof(struct tracefs_inode),
819 0, (SLAB_RECLAIM_ACCOUNT|
820 SLAB_ACCOUNT),
821 init_once);
822 if (!tracefs_inode_cachep)
823 return -ENOMEM;
824
825 retval = sysfs_create_mount_point(kernel_kobj, "tracing");
826 if (retval)
827 return -EINVAL;
828
829 retval = register_filesystem(&trace_fs_type);
830 if (!retval)
831 tracefs_registered = true;
832
833 return retval;
834}
835core_initcall(tracefs_init);