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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
4282d606 SRRH |
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 | * | |
4282d606 | 9 | * tracefs is the file system that is used by the tracing infrastructure. |
4282d606 SRRH |
10 | */ |
11 | ||
12 | #include <linux/module.h> | |
13 | #include <linux/fs.h> | |
14 | #include <linux/mount.h> | |
cc31004a | 15 | #include <linux/kobject.h> |
4282d606 SRRH |
16 | #include <linux/namei.h> |
17 | #include <linux/tracefs.h> | |
18 | #include <linux/fsnotify.h> | |
19 | #include <linux/seq_file.h> | |
20 | #include <linux/parser.h> | |
21 | #include <linux/magic.h> | |
22 | #include <linux/slab.h> | |
ccbd54ff | 23 | #include <linux/security.h> |
4282d606 SRRH |
24 | |
25 | #define TRACEFS_DEFAULT_MODE 0700 | |
26 | ||
27 | static struct vfsmount *tracefs_mount; | |
28 | static int tracefs_mount_count; | |
29 | static bool tracefs_registered; | |
30 | ||
ccbd54ff MG |
31 | static int default_open_file(struct inode *inode, struct file *filp) |
32 | { | |
33 | struct dentry *dentry = filp->f_path.dentry; | |
34 | struct file_operations *real_fops; | |
35 | int ret; | |
36 | ||
37 | if (!dentry) | |
38 | return -EINVAL; | |
39 | ||
40 | ret = security_locked_down(LOCKDOWN_TRACEFS); | |
41 | if (ret) | |
42 | return ret; | |
43 | ||
44 | real_fops = dentry->d_fsdata; | |
45 | if (!real_fops->open) | |
46 | return 0; | |
47 | return real_fops->open(inode, filp); | |
48 | } | |
49 | ||
4282d606 SRRH |
50 | static ssize_t default_read_file(struct file *file, char __user *buf, |
51 | size_t count, loff_t *ppos) | |
52 | { | |
53 | return 0; | |
54 | } | |
55 | ||
56 | static ssize_t default_write_file(struct file *file, const char __user *buf, | |
57 | size_t count, loff_t *ppos) | |
58 | { | |
59 | return count; | |
60 | } | |
61 | ||
62 | static const struct file_operations tracefs_file_operations = { | |
63 | .read = default_read_file, | |
64 | .write = default_write_file, | |
65 | .open = simple_open, | |
66 | .llseek = noop_llseek, | |
67 | }; | |
68 | ||
eae47358 SRRH |
69 | static struct tracefs_dir_ops { |
70 | int (*mkdir)(const char *name); | |
71 | int (*rmdir)(const char *name); | |
5248ee85 | 72 | } tracefs_ops __ro_after_init; |
eae47358 SRRH |
73 | |
74 | static char *get_dname(struct dentry *dentry) | |
75 | { | |
76 | const char *dname; | |
77 | char *name; | |
78 | int len = dentry->d_name.len; | |
79 | ||
80 | dname = dentry->d_name.name; | |
81 | name = kmalloc(len + 1, GFP_KERNEL); | |
82 | if (!name) | |
83 | return NULL; | |
84 | memcpy(name, dname, len); | |
85 | name[len] = 0; | |
86 | return name; | |
87 | } | |
88 | ||
89 | static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode) | |
90 | { | |
91 | char *name; | |
92 | int ret; | |
93 | ||
94 | name = get_dname(dentry); | |
95 | if (!name) | |
96 | return -ENOMEM; | |
97 | ||
98 | /* | |
99 | * The mkdir call can call the generic functions that create | |
100 | * the files within the tracefs system. It is up to the individual | |
101 | * mkdir routine to handle races. | |
102 | */ | |
5955102c | 103 | inode_unlock(inode); |
eae47358 | 104 | ret = tracefs_ops.mkdir(name); |
5955102c | 105 | inode_lock(inode); |
eae47358 SRRH |
106 | |
107 | kfree(name); | |
108 | ||
109 | return ret; | |
110 | } | |
111 | ||
112 | static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry) | |
113 | { | |
114 | char *name; | |
115 | int ret; | |
116 | ||
117 | name = get_dname(dentry); | |
118 | if (!name) | |
119 | return -ENOMEM; | |
120 | ||
121 | /* | |
122 | * The rmdir call can call the generic functions that create | |
123 | * the files within the tracefs system. It is up to the individual | |
124 | * rmdir routine to handle races. | |
125 | * This time we need to unlock not only the parent (inode) but | |
126 | * also the directory that is being deleted. | |
127 | */ | |
5955102c AV |
128 | inode_unlock(inode); |
129 | inode_unlock(dentry->d_inode); | |
eae47358 SRRH |
130 | |
131 | ret = tracefs_ops.rmdir(name); | |
132 | ||
5955102c AV |
133 | inode_lock_nested(inode, I_MUTEX_PARENT); |
134 | inode_lock(dentry->d_inode); | |
eae47358 SRRH |
135 | |
136 | kfree(name); | |
137 | ||
138 | return ret; | |
139 | } | |
140 | ||
141 | static const struct inode_operations tracefs_dir_inode_operations = { | |
142 | .lookup = simple_lookup, | |
143 | .mkdir = tracefs_syscall_mkdir, | |
144 | .rmdir = tracefs_syscall_rmdir, | |
145 | }; | |
146 | ||
4282d606 SRRH |
147 | static struct inode *tracefs_get_inode(struct super_block *sb) |
148 | { | |
149 | struct inode *inode = new_inode(sb); | |
150 | if (inode) { | |
151 | inode->i_ino = get_next_ino(); | |
078cd827 | 152 | inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); |
4282d606 SRRH |
153 | } |
154 | return inode; | |
155 | } | |
156 | ||
157 | struct tracefs_mount_opts { | |
158 | kuid_t uid; | |
159 | kgid_t gid; | |
160 | umode_t mode; | |
161 | }; | |
162 | ||
163 | enum { | |
164 | Opt_uid, | |
165 | Opt_gid, | |
166 | Opt_mode, | |
167 | Opt_err | |
168 | }; | |
169 | ||
170 | static const match_table_t tokens = { | |
171 | {Opt_uid, "uid=%u"}, | |
172 | {Opt_gid, "gid=%u"}, | |
173 | {Opt_mode, "mode=%o"}, | |
174 | {Opt_err, NULL} | |
175 | }; | |
176 | ||
177 | struct tracefs_fs_info { | |
178 | struct tracefs_mount_opts mount_opts; | |
179 | }; | |
180 | ||
181 | static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts) | |
182 | { | |
183 | substring_t args[MAX_OPT_ARGS]; | |
184 | int option; | |
185 | int token; | |
186 | kuid_t uid; | |
187 | kgid_t gid; | |
188 | char *p; | |
189 | ||
190 | opts->mode = TRACEFS_DEFAULT_MODE; | |
191 | ||
192 | while ((p = strsep(&data, ",")) != NULL) { | |
193 | if (!*p) | |
194 | continue; | |
195 | ||
196 | token = match_token(p, tokens, args); | |
197 | switch (token) { | |
198 | case Opt_uid: | |
199 | if (match_int(&args[0], &option)) | |
200 | return -EINVAL; | |
201 | uid = make_kuid(current_user_ns(), option); | |
202 | if (!uid_valid(uid)) | |
203 | return -EINVAL; | |
204 | opts->uid = uid; | |
205 | break; | |
206 | case Opt_gid: | |
207 | if (match_int(&args[0], &option)) | |
208 | return -EINVAL; | |
209 | gid = make_kgid(current_user_ns(), option); | |
210 | if (!gid_valid(gid)) | |
211 | return -EINVAL; | |
212 | opts->gid = gid; | |
213 | break; | |
214 | case Opt_mode: | |
215 | if (match_octal(&args[0], &option)) | |
216 | return -EINVAL; | |
217 | opts->mode = option & S_IALLUGO; | |
218 | break; | |
219 | /* | |
220 | * We might like to report bad mount options here; | |
221 | * but traditionally tracefs has ignored all mount options | |
222 | */ | |
223 | } | |
224 | } | |
225 | ||
226 | return 0; | |
227 | } | |
228 | ||
229 | static int tracefs_apply_options(struct super_block *sb) | |
230 | { | |
231 | struct tracefs_fs_info *fsi = sb->s_fs_info; | |
232 | struct inode *inode = sb->s_root->d_inode; | |
233 | struct tracefs_mount_opts *opts = &fsi->mount_opts; | |
234 | ||
235 | inode->i_mode &= ~S_IALLUGO; | |
236 | inode->i_mode |= opts->mode; | |
237 | ||
238 | inode->i_uid = opts->uid; | |
239 | inode->i_gid = opts->gid; | |
240 | ||
241 | return 0; | |
242 | } | |
243 | ||
ccbd54ff MG |
244 | static void tracefs_destroy_inode(struct inode *inode) |
245 | { | |
246 | if (S_ISREG(inode->i_mode)) | |
247 | kfree(inode->i_fop); | |
248 | } | |
249 | ||
4282d606 SRRH |
250 | static int tracefs_remount(struct super_block *sb, int *flags, char *data) |
251 | { | |
252 | int err; | |
253 | struct tracefs_fs_info *fsi = sb->s_fs_info; | |
254 | ||
255 | sync_filesystem(sb); | |
256 | err = tracefs_parse_options(data, &fsi->mount_opts); | |
257 | if (err) | |
258 | goto fail; | |
259 | ||
260 | tracefs_apply_options(sb); | |
261 | ||
262 | fail: | |
263 | return err; | |
264 | } | |
265 | ||
266 | static int tracefs_show_options(struct seq_file *m, struct dentry *root) | |
267 | { | |
268 | struct tracefs_fs_info *fsi = root->d_sb->s_fs_info; | |
269 | struct tracefs_mount_opts *opts = &fsi->mount_opts; | |
270 | ||
271 | if (!uid_eq(opts->uid, GLOBAL_ROOT_UID)) | |
272 | seq_printf(m, ",uid=%u", | |
273 | from_kuid_munged(&init_user_ns, opts->uid)); | |
274 | if (!gid_eq(opts->gid, GLOBAL_ROOT_GID)) | |
275 | seq_printf(m, ",gid=%u", | |
276 | from_kgid_munged(&init_user_ns, opts->gid)); | |
277 | if (opts->mode != TRACEFS_DEFAULT_MODE) | |
278 | seq_printf(m, ",mode=%o", opts->mode); | |
279 | ||
280 | return 0; | |
281 | } | |
282 | ||
283 | static const struct super_operations tracefs_super_operations = { | |
284 | .statfs = simple_statfs, | |
285 | .remount_fs = tracefs_remount, | |
ccbd54ff | 286 | .destroy_inode = tracefs_destroy_inode, |
4282d606 SRRH |
287 | .show_options = tracefs_show_options, |
288 | }; | |
289 | ||
290 | static int trace_fill_super(struct super_block *sb, void *data, int silent) | |
291 | { | |
cda37124 | 292 | static const struct tree_descr trace_files[] = {{""}}; |
4282d606 SRRH |
293 | struct tracefs_fs_info *fsi; |
294 | int err; | |
295 | ||
4282d606 SRRH |
296 | fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL); |
297 | sb->s_fs_info = fsi; | |
298 | if (!fsi) { | |
299 | err = -ENOMEM; | |
300 | goto fail; | |
301 | } | |
302 | ||
303 | err = tracefs_parse_options(data, &fsi->mount_opts); | |
304 | if (err) | |
305 | goto fail; | |
306 | ||
307 | err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files); | |
308 | if (err) | |
309 | goto fail; | |
310 | ||
311 | sb->s_op = &tracefs_super_operations; | |
312 | ||
313 | tracefs_apply_options(sb); | |
314 | ||
315 | return 0; | |
316 | ||
317 | fail: | |
318 | kfree(fsi); | |
319 | sb->s_fs_info = NULL; | |
320 | return err; | |
321 | } | |
322 | ||
323 | static struct dentry *trace_mount(struct file_system_type *fs_type, | |
324 | int flags, const char *dev_name, | |
325 | void *data) | |
326 | { | |
327 | return mount_single(fs_type, flags, data, trace_fill_super); | |
328 | } | |
329 | ||
330 | static struct file_system_type trace_fs_type = { | |
331 | .owner = THIS_MODULE, | |
332 | .name = "tracefs", | |
333 | .mount = trace_mount, | |
334 | .kill_sb = kill_litter_super, | |
335 | }; | |
336 | MODULE_ALIAS_FS("tracefs"); | |
337 | ||
338 | static struct dentry *start_creating(const char *name, struct dentry *parent) | |
339 | { | |
340 | struct dentry *dentry; | |
341 | int error; | |
342 | ||
343 | pr_debug("tracefs: creating file '%s'\n",name); | |
344 | ||
345 | error = simple_pin_fs(&trace_fs_type, &tracefs_mount, | |
346 | &tracefs_mount_count); | |
347 | if (error) | |
348 | return ERR_PTR(error); | |
349 | ||
350 | /* If the parent is not specified, we create it in the root. | |
351 | * We need the root dentry to do this, which is in the super | |
352 | * block. A pointer to that is in the struct vfsmount that we | |
353 | * have around. | |
354 | */ | |
355 | if (!parent) | |
356 | parent = tracefs_mount->mnt_root; | |
357 | ||
5955102c | 358 | inode_lock(parent->d_inode); |
4282d606 SRRH |
359 | dentry = lookup_one_len(name, parent, strlen(name)); |
360 | if (!IS_ERR(dentry) && dentry->d_inode) { | |
361 | dput(dentry); | |
362 | dentry = ERR_PTR(-EEXIST); | |
363 | } | |
d227c3ae DB |
364 | |
365 | if (IS_ERR(dentry)) { | |
5955102c | 366 | inode_unlock(parent->d_inode); |
d227c3ae DB |
367 | simple_release_fs(&tracefs_mount, &tracefs_mount_count); |
368 | } | |
369 | ||
4282d606 SRRH |
370 | return dentry; |
371 | } | |
372 | ||
373 | static struct dentry *failed_creating(struct dentry *dentry) | |
374 | { | |
5955102c | 375 | inode_unlock(dentry->d_parent->d_inode); |
4282d606 SRRH |
376 | dput(dentry); |
377 | simple_release_fs(&tracefs_mount, &tracefs_mount_count); | |
378 | return NULL; | |
379 | } | |
380 | ||
381 | static struct dentry *end_creating(struct dentry *dentry) | |
382 | { | |
5955102c | 383 | inode_unlock(dentry->d_parent->d_inode); |
4282d606 SRRH |
384 | return dentry; |
385 | } | |
386 | ||
387 | /** | |
388 | * tracefs_create_file - create a file in the tracefs filesystem | |
389 | * @name: a pointer to a string containing the name of the file to create. | |
390 | * @mode: the permission that the file should have. | |
391 | * @parent: a pointer to the parent dentry for this file. This should be a | |
392 | * directory dentry if set. If this parameter is NULL, then the | |
393 | * file will be created in the root of the tracefs filesystem. | |
394 | * @data: a pointer to something that the caller will want to get to later | |
395 | * on. The inode.i_private pointer will point to this value on | |
396 | * the open() call. | |
397 | * @fops: a pointer to a struct file_operations that should be used for | |
398 | * this file. | |
399 | * | |
400 | * This is the basic "create a file" function for tracefs. It allows for a | |
401 | * wide range of flexibility in creating a file, or a directory (if you want | |
402 | * to create a directory, the tracefs_create_dir() function is | |
403 | * recommended to be used instead.) | |
404 | * | |
405 | * This function will return a pointer to a dentry if it succeeds. This | |
406 | * pointer must be passed to the tracefs_remove() function when the file is | |
407 | * to be removed (no automatic cleanup happens if your module is unloaded, | |
408 | * you are responsible here.) If an error occurs, %NULL will be returned. | |
409 | * | |
410 | * If tracefs is not enabled in the kernel, the value -%ENODEV will be | |
411 | * returned. | |
412 | */ | |
413 | struct dentry *tracefs_create_file(const char *name, umode_t mode, | |
414 | struct dentry *parent, void *data, | |
415 | const struct file_operations *fops) | |
416 | { | |
ccbd54ff | 417 | struct file_operations *proxy_fops; |
4282d606 SRRH |
418 | struct dentry *dentry; |
419 | struct inode *inode; | |
420 | ||
421 | if (!(mode & S_IFMT)) | |
422 | mode |= S_IFREG; | |
423 | BUG_ON(!S_ISREG(mode)); | |
424 | dentry = start_creating(name, parent); | |
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 | ||
ccbd54ff MG |
433 | proxy_fops = kzalloc(sizeof(struct file_operations), GFP_KERNEL); |
434 | if (unlikely(!proxy_fops)) { | |
435 | iput(inode); | |
436 | return failed_creating(dentry); | |
437 | } | |
438 | ||
439 | if (!fops) | |
440 | fops = &tracefs_file_operations; | |
441 | ||
442 | dentry->d_fsdata = (void *)fops; | |
443 | memcpy(proxy_fops, fops, sizeof(*proxy_fops)); | |
444 | proxy_fops->open = default_open_file; | |
4282d606 | 445 | inode->i_mode = mode; |
ccbd54ff | 446 | inode->i_fop = proxy_fops; |
4282d606 SRRH |
447 | inode->i_private = data; |
448 | d_instantiate(dentry, inode); | |
449 | fsnotify_create(dentry->d_parent->d_inode, dentry); | |
450 | return end_creating(dentry); | |
451 | } | |
452 | ||
eae47358 SRRH |
453 | static struct dentry *__create_dir(const char *name, struct dentry *parent, |
454 | const struct inode_operations *ops) | |
455 | { | |
456 | struct dentry *dentry = start_creating(name, parent); | |
457 | struct inode *inode; | |
458 | ||
459 | if (IS_ERR(dentry)) | |
460 | return NULL; | |
461 | ||
462 | inode = tracefs_get_inode(dentry->d_sb); | |
463 | if (unlikely(!inode)) | |
464 | return failed_creating(dentry); | |
465 | ||
466 | inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; | |
467 | inode->i_op = ops; | |
468 | inode->i_fop = &simple_dir_operations; | |
469 | ||
470 | /* directory inodes start off with i_nlink == 2 (for "." entry) */ | |
471 | inc_nlink(inode); | |
472 | d_instantiate(dentry, inode); | |
473 | inc_nlink(dentry->d_parent->d_inode); | |
474 | fsnotify_mkdir(dentry->d_parent->d_inode, dentry); | |
475 | return end_creating(dentry); | |
476 | } | |
477 | ||
4282d606 SRRH |
478 | /** |
479 | * tracefs_create_dir - create a directory in the tracefs filesystem | |
480 | * @name: a pointer to a string containing the name of the directory to | |
481 | * create. | |
482 | * @parent: a pointer to the parent dentry for this file. This should be a | |
483 | * directory dentry if set. If this parameter is NULL, then the | |
484 | * directory will be created in the root of the tracefs filesystem. | |
485 | * | |
486 | * This function creates a directory in tracefs with the given name. | |
487 | * | |
488 | * This function will return a pointer to a dentry if it succeeds. This | |
489 | * pointer must be passed to the tracefs_remove() function when the file is | |
490 | * to be removed. If an error occurs, %NULL will be returned. | |
491 | * | |
492 | * If tracing is not enabled in the kernel, the value -%ENODEV will be | |
493 | * returned. | |
494 | */ | |
495 | struct dentry *tracefs_create_dir(const char *name, struct dentry *parent) | |
496 | { | |
eae47358 SRRH |
497 | return __create_dir(name, parent, &simple_dir_inode_operations); |
498 | } | |
4282d606 | 499 | |
eae47358 SRRH |
500 | /** |
501 | * tracefs_create_instance_dir - create the tracing instances directory | |
502 | * @name: The name of the instances directory to create | |
503 | * @parent: The parent directory that the instances directory will exist | |
504 | * @mkdir: The function to call when a mkdir is performed. | |
505 | * @rmdir: The function to call when a rmdir is performed. | |
506 | * | |
507 | * Only one instances directory is allowed. | |
508 | * | |
509 | * The instances directory is special as it allows for mkdir and rmdir to | |
510 | * to be done by userspace. When a mkdir or rmdir is performed, the inode | |
511 | * locks are released and the methhods passed in (@mkdir and @rmdir) are | |
512 | * called without locks and with the name of the directory being created | |
513 | * within the instances directory. | |
514 | * | |
515 | * Returns the dentry of the instances directory. | |
516 | */ | |
5248ee85 ZM |
517 | __init struct dentry *tracefs_create_instance_dir(const char *name, |
518 | struct dentry *parent, | |
eae47358 SRRH |
519 | int (*mkdir)(const char *name), |
520 | int (*rmdir)(const char *name)) | |
521 | { | |
522 | struct dentry *dentry; | |
523 | ||
524 | /* Only allow one instance of the instances directory. */ | |
525 | if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir)) | |
4282d606 SRRH |
526 | return NULL; |
527 | ||
eae47358 SRRH |
528 | dentry = __create_dir(name, parent, &tracefs_dir_inode_operations); |
529 | if (!dentry) | |
530 | return NULL; | |
4282d606 | 531 | |
eae47358 SRRH |
532 | tracefs_ops.mkdir = mkdir; |
533 | tracefs_ops.rmdir = rmdir; | |
4282d606 | 534 | |
eae47358 | 535 | return dentry; |
4282d606 SRRH |
536 | } |
537 | ||
4282d606 SRRH |
538 | static int __tracefs_remove(struct dentry *dentry, struct dentry *parent) |
539 | { | |
540 | int ret = 0; | |
541 | ||
dc3f4198 | 542 | if (simple_positive(dentry)) { |
4282d606 SRRH |
543 | if (dentry->d_inode) { |
544 | dget(dentry); | |
545 | switch (dentry->d_inode->i_mode & S_IFMT) { | |
546 | case S_IFDIR: | |
547 | ret = simple_rmdir(parent->d_inode, dentry); | |
4bf23774 AG |
548 | if (!ret) |
549 | fsnotify_rmdir(parent->d_inode, dentry); | |
4282d606 SRRH |
550 | break; |
551 | default: | |
552 | simple_unlink(parent->d_inode, dentry); | |
4bf23774 | 553 | fsnotify_unlink(parent->d_inode, dentry); |
4282d606 SRRH |
554 | break; |
555 | } | |
556 | if (!ret) | |
557 | d_delete(dentry); | |
558 | dput(dentry); | |
559 | } | |
560 | } | |
561 | return ret; | |
562 | } | |
563 | ||
564 | /** | |
565 | * tracefs_remove - removes a file or directory from the tracefs filesystem | |
566 | * @dentry: a pointer to a the dentry of the file or directory to be | |
567 | * removed. | |
568 | * | |
569 | * This function removes a file or directory in tracefs that was previously | |
570 | * created with a call to another tracefs function (like | |
571 | * tracefs_create_file() or variants thereof.) | |
572 | */ | |
573 | void tracefs_remove(struct dentry *dentry) | |
574 | { | |
575 | struct dentry *parent; | |
576 | int ret; | |
577 | ||
578 | if (IS_ERR_OR_NULL(dentry)) | |
579 | return; | |
580 | ||
581 | parent = dentry->d_parent; | |
5955102c | 582 | inode_lock(parent->d_inode); |
4282d606 | 583 | ret = __tracefs_remove(dentry, parent); |
5955102c | 584 | inode_unlock(parent->d_inode); |
4282d606 SRRH |
585 | if (!ret) |
586 | simple_release_fs(&tracefs_mount, &tracefs_mount_count); | |
587 | } | |
588 | ||
589 | /** | |
590 | * tracefs_remove_recursive - recursively removes a directory | |
591 | * @dentry: a pointer to a the dentry of the directory to be removed. | |
592 | * | |
593 | * This function recursively removes a directory tree in tracefs that | |
594 | * was previously created with a call to another tracefs function | |
595 | * (like tracefs_create_file() or variants thereof.) | |
596 | */ | |
597 | void tracefs_remove_recursive(struct dentry *dentry) | |
598 | { | |
599 | struct dentry *child, *parent; | |
600 | ||
601 | if (IS_ERR_OR_NULL(dentry)) | |
602 | return; | |
603 | ||
4282d606 SRRH |
604 | parent = dentry; |
605 | down: | |
5955102c | 606 | inode_lock(parent->d_inode); |
4282d606 SRRH |
607 | loop: |
608 | /* | |
609 | * The parent->d_subdirs is protected by the d_lock. Outside that | |
610 | * lock, the child can be unlinked and set to be freed which can | |
611 | * use the d_u.d_child as the rcu head and corrupt this list. | |
612 | */ | |
613 | spin_lock(&parent->d_lock); | |
614 | list_for_each_entry(child, &parent->d_subdirs, d_child) { | |
dc3f4198 | 615 | if (!simple_positive(child)) |
4282d606 SRRH |
616 | continue; |
617 | ||
618 | /* perhaps simple_empty(child) makes more sense */ | |
619 | if (!list_empty(&child->d_subdirs)) { | |
620 | spin_unlock(&parent->d_lock); | |
5955102c | 621 | inode_unlock(parent->d_inode); |
4282d606 SRRH |
622 | parent = child; |
623 | goto down; | |
624 | } | |
625 | ||
626 | spin_unlock(&parent->d_lock); | |
627 | ||
628 | if (!__tracefs_remove(child, parent)) | |
629 | simple_release_fs(&tracefs_mount, &tracefs_mount_count); | |
630 | ||
631 | /* | |
632 | * The parent->d_lock protects agaist child from unlinking | |
633 | * from d_subdirs. When releasing the parent->d_lock we can | |
634 | * no longer trust that the next pointer is valid. | |
635 | * Restart the loop. We'll skip this one with the | |
dc3f4198 | 636 | * simple_positive() check. |
4282d606 SRRH |
637 | */ |
638 | goto loop; | |
639 | } | |
640 | spin_unlock(&parent->d_lock); | |
641 | ||
5955102c | 642 | inode_unlock(parent->d_inode); |
4282d606 SRRH |
643 | child = parent; |
644 | parent = parent->d_parent; | |
5955102c | 645 | inode_lock(parent->d_inode); |
4282d606 SRRH |
646 | |
647 | if (child != dentry) | |
648 | /* go up */ | |
649 | goto loop; | |
650 | ||
651 | if (!__tracefs_remove(child, parent)) | |
652 | simple_release_fs(&tracefs_mount, &tracefs_mount_count); | |
5955102c | 653 | inode_unlock(parent->d_inode); |
4282d606 SRRH |
654 | } |
655 | ||
656 | /** | |
657 | * tracefs_initialized - Tells whether tracefs has been registered | |
658 | */ | |
659 | bool tracefs_initialized(void) | |
660 | { | |
661 | return tracefs_registered; | |
662 | } | |
663 | ||
664 | static int __init tracefs_init(void) | |
665 | { | |
666 | int retval; | |
667 | ||
f9bb4882 EB |
668 | retval = sysfs_create_mount_point(kernel_kobj, "tracing"); |
669 | if (retval) | |
cc31004a SRRH |
670 | return -EINVAL; |
671 | ||
4282d606 SRRH |
672 | retval = register_filesystem(&trace_fs_type); |
673 | if (!retval) | |
674 | tracefs_registered = true; | |
675 | ||
676 | return retval; | |
677 | } | |
678 | core_initcall(tracefs_init); |