1 // SPDX-License-Identifier: GPL-2.0-only
3 * inode.c - part of tracefs, a pseudo file system for activating tracing
5 * Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
7 * Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
9 * tracefs is the file system that is used by the tracing infrastructure.
12 #include <linux/module.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>
25 #define TRACEFS_DEFAULT_MODE 0700
27 static struct vfsmount
*tracefs_mount
;
28 static int tracefs_mount_count
;
29 static bool tracefs_registered
;
31 static ssize_t
default_read_file(struct file
*file
, char __user
*buf
,
32 size_t count
, loff_t
*ppos
)
37 static ssize_t
default_write_file(struct file
*file
, const char __user
*buf
,
38 size_t count
, loff_t
*ppos
)
43 static const struct file_operations tracefs_file_operations
= {
44 .read
= default_read_file
,
45 .write
= default_write_file
,
47 .llseek
= noop_llseek
,
50 static struct tracefs_dir_ops
{
51 int (*mkdir
)(const char *name
);
52 int (*rmdir
)(const char *name
);
53 } tracefs_ops __ro_after_init
;
55 static char *get_dname(struct dentry
*dentry
)
59 int len
= dentry
->d_name
.len
;
61 dname
= dentry
->d_name
.name
;
62 name
= kmalloc(len
+ 1, GFP_KERNEL
);
65 memcpy(name
, dname
, len
);
70 static int tracefs_syscall_mkdir(struct user_namespace
*mnt_userns
,
71 struct inode
*inode
, struct dentry
*dentry
,
77 name
= get_dname(dentry
);
82 * The mkdir call can call the generic functions that create
83 * the files within the tracefs system. It is up to the individual
84 * mkdir routine to handle races.
87 ret
= tracefs_ops
.mkdir(name
);
95 static int tracefs_syscall_rmdir(struct inode
*inode
, struct dentry
*dentry
)
100 name
= get_dname(dentry
);
105 * The rmdir call can call the generic functions that create
106 * the files within the tracefs system. It is up to the individual
107 * rmdir routine to handle races.
108 * This time we need to unlock not only the parent (inode) but
109 * also the directory that is being deleted.
112 inode_unlock(dentry
->d_inode
);
114 ret
= tracefs_ops
.rmdir(name
);
116 inode_lock_nested(inode
, I_MUTEX_PARENT
);
117 inode_lock(dentry
->d_inode
);
124 static const struct inode_operations tracefs_dir_inode_operations
= {
125 .lookup
= simple_lookup
,
126 .mkdir
= tracefs_syscall_mkdir
,
127 .rmdir
= tracefs_syscall_rmdir
,
130 static struct inode
*tracefs_get_inode(struct super_block
*sb
)
132 struct inode
*inode
= new_inode(sb
);
134 inode
->i_ino
= get_next_ino();
135 inode
->i_atime
= inode
->i_mtime
= inode
->i_ctime
= current_time(inode
);
140 struct tracefs_mount_opts
{
153 static const match_table_t tokens
= {
156 {Opt_mode
, "mode=%o"},
160 struct tracefs_fs_info
{
161 struct tracefs_mount_opts mount_opts
;
164 static int tracefs_parse_options(char *data
, struct tracefs_mount_opts
*opts
)
166 substring_t args
[MAX_OPT_ARGS
];
173 opts
->mode
= TRACEFS_DEFAULT_MODE
;
175 while ((p
= strsep(&data
, ",")) != NULL
) {
179 token
= match_token(p
, tokens
, args
);
182 if (match_int(&args
[0], &option
))
184 uid
= make_kuid(current_user_ns(), option
);
190 if (match_int(&args
[0], &option
))
192 gid
= make_kgid(current_user_ns(), option
);
198 if (match_octal(&args
[0], &option
))
200 opts
->mode
= option
& S_IALLUGO
;
203 * We might like to report bad mount options here;
204 * but traditionally tracefs has ignored all mount options
212 static int tracefs_apply_options(struct super_block
*sb
)
214 struct tracefs_fs_info
*fsi
= sb
->s_fs_info
;
215 struct inode
*inode
= sb
->s_root
->d_inode
;
216 struct tracefs_mount_opts
*opts
= &fsi
->mount_opts
;
218 inode
->i_mode
&= ~S_IALLUGO
;
219 inode
->i_mode
|= opts
->mode
;
221 inode
->i_uid
= opts
->uid
;
222 inode
->i_gid
= opts
->gid
;
227 static int tracefs_remount(struct super_block
*sb
, int *flags
, char *data
)
230 struct tracefs_fs_info
*fsi
= sb
->s_fs_info
;
233 err
= tracefs_parse_options(data
, &fsi
->mount_opts
);
237 tracefs_apply_options(sb
);
243 static int tracefs_show_options(struct seq_file
*m
, struct dentry
*root
)
245 struct tracefs_fs_info
*fsi
= root
->d_sb
->s_fs_info
;
246 struct tracefs_mount_opts
*opts
= &fsi
->mount_opts
;
248 if (!uid_eq(opts
->uid
, GLOBAL_ROOT_UID
))
249 seq_printf(m
, ",uid=%u",
250 from_kuid_munged(&init_user_ns
, opts
->uid
));
251 if (!gid_eq(opts
->gid
, GLOBAL_ROOT_GID
))
252 seq_printf(m
, ",gid=%u",
253 from_kgid_munged(&init_user_ns
, opts
->gid
));
254 if (opts
->mode
!= TRACEFS_DEFAULT_MODE
)
255 seq_printf(m
, ",mode=%o", opts
->mode
);
260 static const struct super_operations tracefs_super_operations
= {
261 .statfs
= simple_statfs
,
262 .remount_fs
= tracefs_remount
,
263 .show_options
= tracefs_show_options
,
266 static int trace_fill_super(struct super_block
*sb
, void *data
, int silent
)
268 static const struct tree_descr trace_files
[] = {{""}};
269 struct tracefs_fs_info
*fsi
;
272 fsi
= kzalloc(sizeof(struct tracefs_fs_info
), GFP_KERNEL
);
279 err
= tracefs_parse_options(data
, &fsi
->mount_opts
);
283 err
= simple_fill_super(sb
, TRACEFS_MAGIC
, trace_files
);
287 sb
->s_op
= &tracefs_super_operations
;
289 tracefs_apply_options(sb
);
295 sb
->s_fs_info
= NULL
;
299 static struct dentry
*trace_mount(struct file_system_type
*fs_type
,
300 int flags
, const char *dev_name
,
303 return mount_single(fs_type
, flags
, data
, trace_fill_super
);
306 static struct file_system_type trace_fs_type
= {
307 .owner
= THIS_MODULE
,
309 .mount
= trace_mount
,
310 .kill_sb
= kill_litter_super
,
312 MODULE_ALIAS_FS("tracefs");
314 static struct dentry
*start_creating(const char *name
, struct dentry
*parent
)
316 struct dentry
*dentry
;
319 pr_debug("tracefs: creating file '%s'\n",name
);
321 error
= simple_pin_fs(&trace_fs_type
, &tracefs_mount
,
322 &tracefs_mount_count
);
324 return ERR_PTR(error
);
326 /* If the parent is not specified, we create it in the root.
327 * We need the root dentry to do this, which is in the super
328 * block. A pointer to that is in the struct vfsmount that we
332 parent
= tracefs_mount
->mnt_root
;
334 inode_lock(parent
->d_inode
);
335 if (unlikely(IS_DEADDIR(parent
->d_inode
)))
336 dentry
= ERR_PTR(-ENOENT
);
338 dentry
= lookup_one_len(name
, parent
, strlen(name
));
339 if (!IS_ERR(dentry
) && dentry
->d_inode
) {
341 dentry
= ERR_PTR(-EEXIST
);
344 if (IS_ERR(dentry
)) {
345 inode_unlock(parent
->d_inode
);
346 simple_release_fs(&tracefs_mount
, &tracefs_mount_count
);
352 static struct dentry
*failed_creating(struct dentry
*dentry
)
354 inode_unlock(dentry
->d_parent
->d_inode
);
356 simple_release_fs(&tracefs_mount
, &tracefs_mount_count
);
360 static struct dentry
*end_creating(struct dentry
*dentry
)
362 inode_unlock(dentry
->d_parent
->d_inode
);
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
376 * @fops: a pointer to a struct file_operations that should be used for
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.)
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.
389 * If tracefs is not enabled in the kernel, the value -%ENODEV will be
392 struct dentry
*tracefs_create_file(const char *name
, umode_t mode
,
393 struct dentry
*parent
, void *data
,
394 const struct file_operations
*fops
)
396 struct dentry
*dentry
;
399 if (security_locked_down(LOCKDOWN_TRACEFS
))
402 if (!(mode
& S_IFMT
))
404 BUG_ON(!S_ISREG(mode
));
405 dentry
= start_creating(name
, parent
);
410 inode
= tracefs_get_inode(dentry
->d_sb
);
411 if (unlikely(!inode
))
412 return failed_creating(dentry
);
414 inode
->i_mode
= mode
;
415 inode
->i_fop
= fops
? fops
: &tracefs_file_operations
;
416 inode
->i_private
= data
;
417 d_instantiate(dentry
, inode
);
418 fsnotify_create(dentry
->d_parent
->d_inode
, dentry
);
419 return end_creating(dentry
);
422 static struct dentry
*__create_dir(const char *name
, struct dentry
*parent
,
423 const struct inode_operations
*ops
)
425 struct dentry
*dentry
= start_creating(name
, parent
);
431 inode
= tracefs_get_inode(dentry
->d_sb
);
432 if (unlikely(!inode
))
433 return failed_creating(dentry
);
435 inode
->i_mode
= S_IFDIR
| S_IRWXU
| S_IRUGO
| S_IXUGO
;
437 inode
->i_fop
= &simple_dir_operations
;
439 /* directory inodes start off with i_nlink == 2 (for "." entry) */
441 d_instantiate(dentry
, inode
);
442 inc_nlink(dentry
->d_parent
->d_inode
);
443 fsnotify_mkdir(dentry
->d_parent
->d_inode
, dentry
);
444 return end_creating(dentry
);
448 * tracefs_create_dir - create a directory in the tracefs filesystem
449 * @name: a pointer to a string containing the name of the directory to
451 * @parent: a pointer to the parent dentry for this file. This should be a
452 * directory dentry if set. If this parameter is NULL, then the
453 * directory will be created in the root of the tracefs filesystem.
455 * This function creates a directory in tracefs with the given name.
457 * This function will return a pointer to a dentry if it succeeds. This
458 * pointer must be passed to the tracefs_remove() function when the file is
459 * to be removed. If an error occurs, %NULL will be returned.
461 * If tracing is not enabled in the kernel, the value -%ENODEV will be
464 struct dentry
*tracefs_create_dir(const char *name
, struct dentry
*parent
)
466 return __create_dir(name
, parent
, &simple_dir_inode_operations
);
470 * tracefs_create_instance_dir - create the tracing instances directory
471 * @name: The name of the instances directory to create
472 * @parent: The parent directory that the instances directory will exist
473 * @mkdir: The function to call when a mkdir is performed.
474 * @rmdir: The function to call when a rmdir is performed.
476 * Only one instances directory is allowed.
478 * The instances directory is special as it allows for mkdir and rmdir to
479 * to be done by userspace. When a mkdir or rmdir is performed, the inode
480 * locks are released and the methods passed in (@mkdir and @rmdir) are
481 * called without locks and with the name of the directory being created
482 * within the instances directory.
484 * Returns the dentry of the instances directory.
486 __init
struct dentry
*tracefs_create_instance_dir(const char *name
,
487 struct dentry
*parent
,
488 int (*mkdir
)(const char *name
),
489 int (*rmdir
)(const char *name
))
491 struct dentry
*dentry
;
493 /* Only allow one instance of the instances directory. */
494 if (WARN_ON(tracefs_ops
.mkdir
|| tracefs_ops
.rmdir
))
497 dentry
= __create_dir(name
, parent
, &tracefs_dir_inode_operations
);
501 tracefs_ops
.mkdir
= mkdir
;
502 tracefs_ops
.rmdir
= rmdir
;
507 static void remove_one(struct dentry
*victim
)
509 simple_release_fs(&tracefs_mount
, &tracefs_mount_count
);
513 * tracefs_remove - recursively removes a directory
514 * @dentry: a pointer to a the dentry of the directory to be removed.
516 * This function recursively removes a directory tree in tracefs that
517 * was previously created with a call to another tracefs function
518 * (like tracefs_create_file() or variants thereof.)
520 void tracefs_remove(struct dentry
*dentry
)
522 if (IS_ERR_OR_NULL(dentry
))
525 simple_pin_fs(&trace_fs_type
, &tracefs_mount
, &tracefs_mount_count
);
526 simple_recursive_removal(dentry
, remove_one
);
527 simple_release_fs(&tracefs_mount
, &tracefs_mount_count
);
531 * tracefs_initialized - Tells whether tracefs has been registered
533 bool tracefs_initialized(void)
535 return tracefs_registered
;
538 static int __init
tracefs_init(void)
542 retval
= sysfs_create_mount_point(kernel_kobj
, "tracing");
546 retval
= register_filesystem(&trace_fs_type
);
548 tracefs_registered
= true;
552 core_initcall(tracefs_init
);