blob: 4a0e48f9210483adf6b9bee36f220e80d65a09cd [file] [log] [blame]
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -05001/*
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>
Steven Rostedt (Red Hat)cc310042015-01-21 11:28:23 -050019#include <linux/kobject.h>
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -050020#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
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -050053static 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 */
Al Viro59551022016-01-22 15:40:57 -050087 inode_unlock(inode);
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -050088 ret = tracefs_ops.mkdir(name);
Al Viro59551022016-01-22 15:40:57 -050089 inode_lock(inode);
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -050090
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 */
Al Viro59551022016-01-22 15:40:57 -0500112 inode_unlock(inode);
113 inode_unlock(dentry->d_inode);
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500114
115 ret = tracefs_ops.rmdir(name);
116
Al Viro59551022016-01-22 15:40:57 -0500117 inode_lock_nested(inode, I_MUTEX_PARENT);
118 inode_lock(dentry->d_inode);
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500119
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
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500131static 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;
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 struct tree_descr trace_files[] = {{""}};
270 struct tracefs_fs_info *fsi;
271 int err;
272
273 save_mount_options(sb, data);
274
275 fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
276 sb->s_fs_info = fsi;
277 if (!fsi) {
278 err = -ENOMEM;
279 goto fail;
280 }
281
282 err = tracefs_parse_options(data, &fsi->mount_opts);
283 if (err)
284 goto fail;
285
286 err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
287 if (err)
288 goto fail;
289
290 sb->s_op = &tracefs_super_operations;
291
292 tracefs_apply_options(sb);
293
294 return 0;
295
296fail:
297 kfree(fsi);
298 sb->s_fs_info = NULL;
299 return err;
300}
301
302static struct dentry *trace_mount(struct file_system_type *fs_type,
303 int flags, const char *dev_name,
304 void *data)
305{
306 return mount_single(fs_type, flags, data, trace_fill_super);
307}
308
309static struct file_system_type trace_fs_type = {
310 .owner = THIS_MODULE,
311 .name = "tracefs",
312 .mount = trace_mount,
313 .kill_sb = kill_litter_super,
314};
315MODULE_ALIAS_FS("tracefs");
316
317static struct dentry *start_creating(const char *name, struct dentry *parent)
318{
319 struct dentry *dentry;
320 int error;
321
322 pr_debug("tracefs: creating file '%s'\n",name);
323
324 error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
325 &tracefs_mount_count);
326 if (error)
327 return ERR_PTR(error);
328
329 /* If the parent is not specified, we create it in the root.
330 * We need the root dentry to do this, which is in the super
331 * block. A pointer to that is in the struct vfsmount that we
332 * have around.
333 */
334 if (!parent)
335 parent = tracefs_mount->mnt_root;
336
Al Viro59551022016-01-22 15:40:57 -0500337 inode_lock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500338 dentry = lookup_one_len(name, parent, strlen(name));
339 if (!IS_ERR(dentry) && dentry->d_inode) {
340 dput(dentry);
341 dentry = ERR_PTR(-EEXIST);
342 }
Daniel Borkmannd227c3a2015-11-04 23:33:17 +0100343
344 if (IS_ERR(dentry)) {
Al Viro59551022016-01-22 15:40:57 -0500345 inode_unlock(parent->d_inode);
Daniel Borkmannd227c3a2015-11-04 23:33:17 +0100346 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
347 }
348
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500349 return dentry;
350}
351
352static struct dentry *failed_creating(struct dentry *dentry)
353{
Al Viro59551022016-01-22 15:40:57 -0500354 inode_unlock(dentry->d_parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500355 dput(dentry);
356 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
357 return NULL;
358}
359
360static struct dentry *end_creating(struct dentry *dentry)
361{
Al Viro59551022016-01-22 15:40:57 -0500362 inode_unlock(dentry->d_parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500363 return dentry;
364}
365
366/**
367 * tracefs_create_file - create a file in the tracefs filesystem
368 * @name: a pointer to a string containing the name of the file to create.
369 * @mode: the permission that the file should have.
370 * @parent: a pointer to the parent dentry for this file. This should be a
371 * directory dentry if set. If this parameter is NULL, then the
372 * file will be created in the root of the tracefs filesystem.
373 * @data: a pointer to something that the caller will want to get to later
374 * on. The inode.i_private pointer will point to this value on
375 * the open() call.
376 * @fops: a pointer to a struct file_operations that should be used for
377 * this file.
378 *
379 * This is the basic "create a file" function for tracefs. It allows for a
380 * wide range of flexibility in creating a file, or a directory (if you want
381 * to create a directory, the tracefs_create_dir() function is
382 * recommended to be used instead.)
383 *
384 * This function will return a pointer to a dentry if it succeeds. This
385 * pointer must be passed to the tracefs_remove() function when the file is
386 * to be removed (no automatic cleanup happens if your module is unloaded,
387 * you are responsible here.) If an error occurs, %NULL will be returned.
388 *
389 * If tracefs is not enabled in the kernel, the value -%ENODEV will be
390 * returned.
391 */
392struct dentry *tracefs_create_file(const char *name, umode_t mode,
393 struct dentry *parent, void *data,
394 const struct file_operations *fops)
395{
396 struct dentry *dentry;
397 struct inode *inode;
398
399 if (!(mode & S_IFMT))
400 mode |= S_IFREG;
401 BUG_ON(!S_ISREG(mode));
402 dentry = start_creating(name, parent);
403
404 if (IS_ERR(dentry))
405 return NULL;
406
407 inode = tracefs_get_inode(dentry->d_sb);
408 if (unlikely(!inode))
409 return failed_creating(dentry);
410
411 inode->i_mode = mode;
412 inode->i_fop = fops ? fops : &tracefs_file_operations;
413 inode->i_private = data;
414 d_instantiate(dentry, inode);
415 fsnotify_create(dentry->d_parent->d_inode, dentry);
416 return end_creating(dentry);
417}
418
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500419static struct dentry *__create_dir(const char *name, struct dentry *parent,
420 const struct inode_operations *ops)
421{
422 struct dentry *dentry = start_creating(name, parent);
423 struct inode *inode;
424
425 if (IS_ERR(dentry))
426 return NULL;
427
428 inode = tracefs_get_inode(dentry->d_sb);
429 if (unlikely(!inode))
430 return failed_creating(dentry);
431
432 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
433 inode->i_op = ops;
434 inode->i_fop = &simple_dir_operations;
435
436 /* directory inodes start off with i_nlink == 2 (for "." entry) */
437 inc_nlink(inode);
438 d_instantiate(dentry, inode);
439 inc_nlink(dentry->d_parent->d_inode);
440 fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
441 return end_creating(dentry);
442}
443
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500444/**
445 * tracefs_create_dir - create a directory in the tracefs filesystem
446 * @name: a pointer to a string containing the name of the directory to
447 * create.
448 * @parent: a pointer to the parent dentry for this file. This should be a
449 * directory dentry if set. If this parameter is NULL, then the
450 * directory will be created in the root of the tracefs filesystem.
451 *
452 * This function creates a directory in tracefs with the given name.
453 *
454 * This function will return a pointer to a dentry if it succeeds. This
455 * pointer must be passed to the tracefs_remove() function when the file is
456 * to be removed. If an error occurs, %NULL will be returned.
457 *
458 * If tracing is not enabled in the kernel, the value -%ENODEV will be
459 * returned.
460 */
461struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
462{
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500463 return __create_dir(name, parent, &simple_dir_inode_operations);
464}
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500465
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500466/**
467 * tracefs_create_instance_dir - create the tracing instances directory
468 * @name: The name of the instances directory to create
469 * @parent: The parent directory that the instances directory will exist
470 * @mkdir: The function to call when a mkdir is performed.
471 * @rmdir: The function to call when a rmdir is performed.
472 *
473 * Only one instances directory is allowed.
474 *
475 * The instances directory is special as it allows for mkdir and rmdir to
476 * to be done by userspace. When a mkdir or rmdir is performed, the inode
477 * locks are released and the methhods passed in (@mkdir and @rmdir) are
478 * called without locks and with the name of the directory being created
479 * within the instances directory.
480 *
481 * Returns the dentry of the instances directory.
482 */
483struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
484 int (*mkdir)(const char *name),
485 int (*rmdir)(const char *name))
486{
487 struct dentry *dentry;
488
489 /* Only allow one instance of the instances directory. */
490 if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500491 return NULL;
492
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500493 dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
494 if (!dentry)
495 return NULL;
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500496
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500497 tracefs_ops.mkdir = mkdir;
498 tracefs_ops.rmdir = rmdir;
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500499
Steven Rostedt (Red Hat)eae47352015-01-21 10:01:39 -0500500 return dentry;
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500501}
502
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500503static int __tracefs_remove(struct dentry *dentry, struct dentry *parent)
504{
505 int ret = 0;
506
Al Virodc3f4192015-05-18 10:10:34 -0400507 if (simple_positive(dentry)) {
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500508 if (dentry->d_inode) {
509 dget(dentry);
510 switch (dentry->d_inode->i_mode & S_IFMT) {
511 case S_IFDIR:
512 ret = simple_rmdir(parent->d_inode, dentry);
513 break;
514 default:
515 simple_unlink(parent->d_inode, dentry);
516 break;
517 }
518 if (!ret)
519 d_delete(dentry);
520 dput(dentry);
521 }
522 }
523 return ret;
524}
525
526/**
527 * tracefs_remove - removes a file or directory from the tracefs filesystem
528 * @dentry: a pointer to a the dentry of the file or directory to be
529 * removed.
530 *
531 * This function removes a file or directory in tracefs that was previously
532 * created with a call to another tracefs function (like
533 * tracefs_create_file() or variants thereof.)
534 */
535void tracefs_remove(struct dentry *dentry)
536{
537 struct dentry *parent;
538 int ret;
539
540 if (IS_ERR_OR_NULL(dentry))
541 return;
542
543 parent = dentry->d_parent;
544 if (!parent || !parent->d_inode)
545 return;
546
Al Viro59551022016-01-22 15:40:57 -0500547 inode_lock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500548 ret = __tracefs_remove(dentry, parent);
Al Viro59551022016-01-22 15:40:57 -0500549 inode_unlock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500550 if (!ret)
551 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
552}
553
554/**
555 * tracefs_remove_recursive - recursively removes a directory
556 * @dentry: a pointer to a the dentry of the directory to be removed.
557 *
558 * This function recursively removes a directory tree in tracefs that
559 * was previously created with a call to another tracefs function
560 * (like tracefs_create_file() or variants thereof.)
561 */
562void tracefs_remove_recursive(struct dentry *dentry)
563{
564 struct dentry *child, *parent;
565
566 if (IS_ERR_OR_NULL(dentry))
567 return;
568
569 parent = dentry->d_parent;
570 if (!parent || !parent->d_inode)
571 return;
572
573 parent = dentry;
574 down:
Al Viro59551022016-01-22 15:40:57 -0500575 inode_lock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500576 loop:
577 /*
578 * The parent->d_subdirs is protected by the d_lock. Outside that
579 * lock, the child can be unlinked and set to be freed which can
580 * use the d_u.d_child as the rcu head and corrupt this list.
581 */
582 spin_lock(&parent->d_lock);
583 list_for_each_entry(child, &parent->d_subdirs, d_child) {
Al Virodc3f4192015-05-18 10:10:34 -0400584 if (!simple_positive(child))
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500585 continue;
586
587 /* perhaps simple_empty(child) makes more sense */
588 if (!list_empty(&child->d_subdirs)) {
589 spin_unlock(&parent->d_lock);
Al Viro59551022016-01-22 15:40:57 -0500590 inode_unlock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500591 parent = child;
592 goto down;
593 }
594
595 spin_unlock(&parent->d_lock);
596
597 if (!__tracefs_remove(child, parent))
598 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
599
600 /*
601 * The parent->d_lock protects agaist child from unlinking
602 * from d_subdirs. When releasing the parent->d_lock we can
603 * no longer trust that the next pointer is valid.
604 * Restart the loop. We'll skip this one with the
Al Virodc3f4192015-05-18 10:10:34 -0400605 * simple_positive() check.
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500606 */
607 goto loop;
608 }
609 spin_unlock(&parent->d_lock);
610
Al Viro59551022016-01-22 15:40:57 -0500611 inode_unlock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500612 child = parent;
613 parent = parent->d_parent;
Al Viro59551022016-01-22 15:40:57 -0500614 inode_lock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500615
616 if (child != dentry)
617 /* go up */
618 goto loop;
619
620 if (!__tracefs_remove(child, parent))
621 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
Al Viro59551022016-01-22 15:40:57 -0500622 inode_unlock(parent->d_inode);
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500623}
624
625/**
626 * tracefs_initialized - Tells whether tracefs has been registered
627 */
628bool tracefs_initialized(void)
629{
630 return tracefs_registered;
631}
632
633static int __init tracefs_init(void)
634{
635 int retval;
636
Eric W. Biedermanf9bb4882015-05-13 17:35:41 -0500637 retval = sysfs_create_mount_point(kernel_kobj, "tracing");
638 if (retval)
Steven Rostedt (Red Hat)cc310042015-01-21 11:28:23 -0500639 return -EINVAL;
640
Steven Rostedt (Red Hat)4282d602015-01-20 11:36:55 -0500641 retval = register_filesystem(&trace_fs_type);
642 if (!retval)
643 tracefs_registered = true;
644
645 return retval;
646}
647core_initcall(tracefs_init);