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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
25#define TRACEFS_DEFAULT_MODE 0700
26
27static struct vfsmount *tracefs_mount;
28static int tracefs_mount_count;
29static bool tracefs_registered;
30
31static ssize_t default_read_file(struct file *file, char __user *buf,
32 size_t count, loff_t *ppos)
33{
34 return 0;
35}
36
37static ssize_t default_write_file(struct file *file, const char __user *buf,
38 size_t count, loff_t *ppos)
39{
40 return count;
41}
42
43static const struct file_operations tracefs_file_operations = {
44 .read = default_read_file,
45 .write = default_write_file,
46 .open = simple_open,
47 .llseek = noop_llseek,
48};
49
50static struct tracefs_dir_ops {
51 int (*mkdir)(const char *name);
52 int (*rmdir)(const char *name);
53} tracefs_ops __ro_after_init;
54
55static char *get_dname(struct dentry *dentry)
56{
57 const char *dname;
58 char *name;
59 int len = dentry->d_name.len;
60
61 dname = dentry->d_name.name;
62 name = kmalloc(len + 1, GFP_KERNEL);
63 if (!name)
64 return NULL;
65 memcpy(name, dname, len);
66 name[len] = 0;
67 return name;
68}
69
70static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
71{
72 char *name;
73 int ret;
74
75 name = get_dname(dentry);
76 if (!name)
77 return -ENOMEM;
78
79 /*
80 * The mkdir call can call the generic functions that create
81 * the files within the tracefs system. It is up to the individual
82 * mkdir routine to handle races.
83 */
84 inode_unlock(inode);
85 ret = tracefs_ops.mkdir(name);
86 inode_lock(inode);
87
88 kfree(name);
89
90 return ret;
91}
92
93static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
94{
95 char *name;
96 int ret;
97
98 name = get_dname(dentry);
99 if (!name)
100 return -ENOMEM;
101
102 /*
103 * The rmdir call can call the generic functions that create
104 * the files within the tracefs system. It is up to the individual
105 * rmdir routine to handle races.
106 * This time we need to unlock not only the parent (inode) but
107 * also the directory that is being deleted.
108 */
109 inode_unlock(inode);
110 inode_unlock(dentry->d_inode);
111
112 ret = tracefs_ops.rmdir(name);
113
114 inode_lock_nested(inode, I_MUTEX_PARENT);
115 inode_lock(dentry->d_inode);
116
117 kfree(name);
118
119 return ret;
120}
121
122static const struct inode_operations tracefs_dir_inode_operations = {
123 .lookup = simple_lookup,
124 .mkdir = tracefs_syscall_mkdir,
125 .rmdir = tracefs_syscall_rmdir,
126};
127
128static struct inode *tracefs_get_inode(struct super_block *sb)
129{
130 struct inode *inode = new_inode(sb);
131 if (inode) {
132 inode->i_ino = get_next_ino();
133 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
134 }
135 return inode;
136}
137
138struct tracefs_mount_opts {
139 kuid_t uid;
140 kgid_t gid;
141 umode_t mode;
142};
143
144enum {
145 Opt_uid,
146 Opt_gid,
147 Opt_mode,
148 Opt_err
149};
150
151static const match_table_t tokens = {
152 {Opt_uid, "uid=%u"},
153 {Opt_gid, "gid=%u"},
154 {Opt_mode, "mode=%o"},
155 {Opt_err, NULL}
156};
157
158struct tracefs_fs_info {
159 struct tracefs_mount_opts mount_opts;
160};
161
162static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
163{
164 substring_t args[MAX_OPT_ARGS];
165 int option;
166 int token;
167 kuid_t uid;
168 kgid_t gid;
169 char *p;
170
171 opts->mode = TRACEFS_DEFAULT_MODE;
172
173 while ((p = strsep(&data, ",")) != NULL) {
174 if (!*p)
175 continue;
176
177 token = match_token(p, tokens, args);
178 switch (token) {
179 case Opt_uid:
180 if (match_int(&args[0], &option))
181 return -EINVAL;
182 uid = make_kuid(current_user_ns(), option);
183 if (!uid_valid(uid))
184 return -EINVAL;
185 opts->uid = uid;
186 break;
187 case Opt_gid:
188 if (match_int(&args[0], &option))
189 return -EINVAL;
190 gid = make_kgid(current_user_ns(), option);
191 if (!gid_valid(gid))
192 return -EINVAL;
193 opts->gid = gid;
194 break;
195 case Opt_mode:
196 if (match_octal(&args[0], &option))
197 return -EINVAL;
198 opts->mode = option & S_IALLUGO;
199 break;
200 /*
201 * We might like to report bad mount options here;
202 * but traditionally tracefs has ignored all mount options
203 */
204 }
205 }
206
207 return 0;
208}
209
210static int tracefs_apply_options(struct super_block *sb)
211{
212 struct tracefs_fs_info *fsi = sb->s_fs_info;
213 struct inode *inode = sb->s_root->d_inode;
214 struct tracefs_mount_opts *opts = &fsi->mount_opts;
215
216 inode->i_mode &= ~S_IALLUGO;
217 inode->i_mode |= opts->mode;
218
219 inode->i_uid = opts->uid;
220 inode->i_gid = opts->gid;
221
222 return 0;
223}
224
225static int tracefs_remount(struct super_block *sb, int *flags, char *data)
226{
227 int err;
228 struct tracefs_fs_info *fsi = sb->s_fs_info;
229
230 sync_filesystem(sb);
231 err = tracefs_parse_options(data, &fsi->mount_opts);
232 if (err)
233 goto fail;
234
235 tracefs_apply_options(sb);
236
237fail:
238 return err;
239}
240
241static int tracefs_show_options(struct seq_file *m, struct dentry *root)
242{
243 struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
244 struct tracefs_mount_opts *opts = &fsi->mount_opts;
245
246 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
247 seq_printf(m, ",uid=%u",
248 from_kuid_munged(&init_user_ns, opts->uid));
249 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
250 seq_printf(m, ",gid=%u",
251 from_kgid_munged(&init_user_ns, opts->gid));
252 if (opts->mode != TRACEFS_DEFAULT_MODE)
253 seq_printf(m, ",mode=%o", opts->mode);
254
255 return 0;
256}
257
258static const struct super_operations tracefs_super_operations = {
259 .statfs = simple_statfs,
260 .remount_fs = tracefs_remount,
261 .show_options = tracefs_show_options,
262};
263
264static int trace_fill_super(struct super_block *sb, void *data, int silent)
265{
266 static const struct tree_descr trace_files[] = {{""}};
267 struct tracefs_fs_info *fsi;
268 int err;
269
270 fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
271 sb->s_fs_info = fsi;
272 if (!fsi) {
273 err = -ENOMEM;
274 goto fail;
275 }
276
277 err = tracefs_parse_options(data, &fsi->mount_opts);
278 if (err)
279 goto fail;
280
281 err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
282 if (err)
283 goto fail;
284
285 sb->s_op = &tracefs_super_operations;
286
287 tracefs_apply_options(sb);
288
289 return 0;
290
291fail:
292 kfree(fsi);
293 sb->s_fs_info = NULL;
294 return err;
295}
296
297static struct dentry *trace_mount(struct file_system_type *fs_type,
298 int flags, const char *dev_name,
299 void *data)
300{
301 return mount_single(fs_type, flags, data, trace_fill_super);
302}
303
304static struct file_system_type trace_fs_type = {
305 .owner = THIS_MODULE,
306 .name = "tracefs",
307 .mount = trace_mount,
308 .kill_sb = kill_litter_super,
309};
310MODULE_ALIAS_FS("tracefs");
311
312static struct dentry *start_creating(const char *name, struct dentry *parent)
313{
314 struct dentry *dentry;
315 int error;
316
317 pr_debug("tracefs: creating file '%s'\n",name);
318
319 error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
320 &tracefs_mount_count);
321 if (error)
322 return ERR_PTR(error);
323
324 /* If the parent is not specified, we create it in the root.
325 * We need the root dentry to do this, which is in the super
326 * block. A pointer to that is in the struct vfsmount that we
327 * have around.
328 */
329 if (!parent)
330 parent = tracefs_mount->mnt_root;
331
332 inode_lock(parent->d_inode);
333 if (unlikely(IS_DEADDIR(parent->d_inode)))
334 dentry = ERR_PTR(-ENOENT);
335 else
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 (security_locked_down(LOCKDOWN_TRACEFS))
398 return NULL;
399
400 if (!(mode & S_IFMT))
401 mode |= S_IFREG;
402 BUG_ON(!S_ISREG(mode));
403 dentry = start_creating(name, parent);
404
405 if (IS_ERR(dentry))
406 return NULL;
407
408 inode = tracefs_get_inode(dentry->d_sb);
409 if (unlikely(!inode))
410 return failed_creating(dentry);
411
412 inode->i_mode = mode;
413 inode->i_fop = fops ? fops : &tracefs_file_operations;
414 inode->i_private = data;
415 d_instantiate(dentry, inode);
416 fsnotify_create(dentry->d_parent->d_inode, dentry);
417 return end_creating(dentry);
418}
419
420static struct dentry *__create_dir(const char *name, struct dentry *parent,
421 const struct inode_operations *ops)
422{
423 struct dentry *dentry = start_creating(name, parent);
424 struct inode *inode;
425
426 if (IS_ERR(dentry))
427 return NULL;
428
429 inode = tracefs_get_inode(dentry->d_sb);
430 if (unlikely(!inode))
431 return failed_creating(dentry);
432
433 inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
434 inode->i_op = ops;
435 inode->i_fop = &simple_dir_operations;
436
437 /* directory inodes start off with i_nlink == 2 (for "." entry) */
438 inc_nlink(inode);
439 d_instantiate(dentry, inode);
440 inc_nlink(dentry->d_parent->d_inode);
441 fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
442 return end_creating(dentry);
443}
444
445/**
446 * tracefs_create_dir - create a directory in the tracefs filesystem
447 * @name: a pointer to a string containing the name of the directory to
448 * create.
449 * @parent: a pointer to the parent dentry for this file. This should be a
450 * directory dentry if set. If this parameter is NULL, then the
451 * directory will be created in the root of the tracefs filesystem.
452 *
453 * This function creates a directory in tracefs with the given name.
454 *
455 * This function will return a pointer to a dentry if it succeeds. This
456 * pointer must be passed to the tracefs_remove() function when the file is
457 * to be removed. If an error occurs, %NULL will be returned.
458 *
459 * If tracing is not enabled in the kernel, the value -%ENODEV will be
460 * returned.
461 */
462struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
463{
464 return __create_dir(name, parent, &simple_dir_inode_operations);
465}
466
467/**
468 * tracefs_create_instance_dir - create the tracing instances directory
469 * @name: The name of the instances directory to create
470 * @parent: The parent directory that the instances directory will exist
471 * @mkdir: The function to call when a mkdir is performed.
472 * @rmdir: The function to call when a rmdir is performed.
473 *
474 * Only one instances directory is allowed.
475 *
476 * The instances directory is special as it allows for mkdir and rmdir to
477 * to be done by userspace. When a mkdir or rmdir is performed, the inode
478 * locks are released and the methhods passed in (@mkdir and @rmdir) are
479 * called without locks and with the name of the directory being created
480 * within the instances directory.
481 *
482 * Returns the dentry of the instances directory.
483 */
484__init struct dentry *tracefs_create_instance_dir(const char *name,
485 struct dentry *parent,
486 int (*mkdir)(const char *name),
487 int (*rmdir)(const char *name))
488{
489 struct dentry *dentry;
490
491 /* Only allow one instance of the instances directory. */
492 if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
493 return NULL;
494
495 dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
496 if (!dentry)
497 return NULL;
498
499 tracefs_ops.mkdir = mkdir;
500 tracefs_ops.rmdir = rmdir;
501
502 return dentry;
503}
504
505static void remove_one(struct dentry *victim)
506{
507 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
508}
509
510/**
511 * tracefs_remove - recursively removes a directory
512 * @dentry: a pointer to a the dentry of the directory to be removed.
513 *
514 * This function recursively removes a directory tree in tracefs that
515 * was previously created with a call to another tracefs function
516 * (like tracefs_create_file() or variants thereof.)
517 */
518void tracefs_remove(struct dentry *dentry)
519{
520 if (IS_ERR_OR_NULL(dentry))
521 return;
522
523 simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
524 simple_recursive_removal(dentry, remove_one);
525 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
526}
527
528/**
529 * tracefs_initialized - Tells whether tracefs has been registered
530 */
531bool tracefs_initialized(void)
532{
533 return tracefs_registered;
534}
535
536static int __init tracefs_init(void)
537{
538 int retval;
539
540 retval = sysfs_create_mount_point(kernel_kobj, "tracing");
541 if (retval)
542 return -EINVAL;
543
544 retval = register_filesystem(&trace_fs_type);
545 if (!retval)
546 tracefs_registered = true;
547
548 return retval;
549}
550core_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;
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
337 inode_lock(parent->d_inode);
338 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 }
343
344 if (IS_ERR(dentry)) {
345 inode_unlock(parent->d_inode);
346 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
347 }
348
349 return dentry;
350}
351
352static struct dentry *failed_creating(struct dentry *dentry)
353{
354 inode_unlock(dentry->d_parent->d_inode);
355 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{
362 inode_unlock(dentry->d_parent->d_inode);
363 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
419static 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
444/**
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{
463 return __create_dir(name, parent, &simple_dir_inode_operations);
464}
465
466/**
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))
491 return NULL;
492
493 dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
494 if (!dentry)
495 return NULL;
496
497 tracefs_ops.mkdir = mkdir;
498 tracefs_ops.rmdir = rmdir;
499
500 return dentry;
501}
502
503static int __tracefs_remove(struct dentry *dentry, struct dentry *parent)
504{
505 int ret = 0;
506
507 if (simple_positive(dentry)) {
508 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
547 inode_lock(parent->d_inode);
548 ret = __tracefs_remove(dentry, parent);
549 inode_unlock(parent->d_inode);
550 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:
575 inode_lock(parent->d_inode);
576 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) {
584 if (!simple_positive(child))
585 continue;
586
587 /* perhaps simple_empty(child) makes more sense */
588 if (!list_empty(&child->d_subdirs)) {
589 spin_unlock(&parent->d_lock);
590 inode_unlock(parent->d_inode);
591 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
605 * simple_positive() check.
606 */
607 goto loop;
608 }
609 spin_unlock(&parent->d_lock);
610
611 inode_unlock(parent->d_inode);
612 child = parent;
613 parent = parent->d_parent;
614 inode_lock(parent->d_inode);
615
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);
622 inode_unlock(parent->d_inode);
623}
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
637 retval = sysfs_create_mount_point(kernel_kobj, "tracing");
638 if (retval)
639 return -EINVAL;
640
641 retval = register_filesystem(&trace_fs_type);
642 if (!retval)
643 tracefs_registered = true;
644
645 return retval;
646}
647core_initcall(tracefs_init);