1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * kernfs.h - pseudo filesystem decoupled from vfs locking
6 #ifndef __LINUX_KERNFS_H
7 #define __LINUX_KERNFS_H
9 #include <linux/kernel.h>
10 #include <linux/err.h>
11 #include <linux/list.h>
12 #include <linux/mutex.h>
13 #include <linux/idr.h>
14 #include <linux/lockdep.h>
15 #include <linux/rbtree.h>
16 #include <linux/atomic.h>
17 #include <linux/uidgid.h>
18 #include <linux/wait.h>
24 struct vm_area_struct
;
26 struct file_system_type
;
27 struct poll_table_struct
;
30 struct kernfs_fs_context
;
31 struct kernfs_open_node
;
34 enum kernfs_node_type
{
40 #define KERNFS_TYPE_MASK 0x000f
41 #define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
42 #define KERNFS_MAX_USER_XATTRS 128
43 #define KERNFS_USER_XATTR_SIZE_LIMIT (128 << 10)
45 enum kernfs_node_flag
{
46 KERNFS_ACTIVATED
= 0x0010,
48 KERNFS_HAS_SEQ_SHOW
= 0x0040,
49 KERNFS_HAS_MMAP
= 0x0080,
50 KERNFS_LOCKDEP
= 0x0100,
51 KERNFS_SUICIDAL
= 0x0400,
52 KERNFS_SUICIDED
= 0x0800,
53 KERNFS_EMPTY_DIR
= 0x1000,
54 KERNFS_HAS_RELEASE
= 0x2000,
57 /* @flags for kernfs_create_root() */
58 enum kernfs_root_flag
{
60 * kernfs_nodes are created in the deactivated state and invisible.
61 * They require explicit kernfs_activate() to become visible. This
62 * can be used to make related nodes become visible atomically
63 * after all nodes are created successfully.
65 KERNFS_ROOT_CREATE_DEACTIVATED
= 0x0001,
68 * For regular files, if the opener has CAP_DAC_OVERRIDE, open(2)
69 * succeeds regardless of the RW permissions. sysfs had an extra
70 * layer of enforcement where open(2) fails with -EACCES regardless
71 * of CAP_DAC_OVERRIDE if the permission doesn't have the
72 * respective read or write access at all (none of S_IRUGO or
73 * S_IWUGO) or the respective operation isn't implemented. The
74 * following flag enables that behavior.
76 KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK
= 0x0002,
79 * The filesystem supports exportfs operation, so userspace can use
80 * fhandle to access nodes of the fs.
82 KERNFS_ROOT_SUPPORT_EXPORTOP
= 0x0004,
85 * Support user xattrs to be written to nodes rooted at this root.
87 KERNFS_ROOT_SUPPORT_USER_XATTR
= 0x0008,
90 /* type-specific structures for kernfs_node union members */
91 struct kernfs_elem_dir
{
92 unsigned long subdirs
;
93 /* children rbtree starts here and goes through kn->rb */
94 struct rb_root children
;
97 * The kernfs hierarchy this directory belongs to. This fits
98 * better directly in kernfs_node but is here to save space.
100 struct kernfs_root
*root
;
102 * Monotonic revision counter, used to identify if a directory
103 * node has changed during negative dentry revalidation.
108 struct kernfs_elem_symlink
{
109 struct kernfs_node
*target_kn
;
112 struct kernfs_elem_attr
{
113 const struct kernfs_ops
*ops
;
114 struct kernfs_open_node
*open
;
116 struct kernfs_node
*notify_next
; /* for kernfs_notify() */
120 * kernfs_node - the building block of kernfs hierarchy. Each and every
121 * kernfs node is represented by single kernfs_node. Most fields are
122 * private to kernfs and shouldn't be accessed directly by kernfs users.
124 * As long as count reference is held, the kernfs_node itself is
125 * accessible. Dereferencing elem or any other outer entity requires
131 #ifdef CONFIG_DEBUG_LOCK_ALLOC
132 struct lockdep_map dep_map
;
135 * Use kernfs_get_parent() and kernfs_name/path() instead of
136 * accessing the following two fields directly. If the node is
137 * never moved to a different parent, it is safe to access the
140 struct kernfs_node
*parent
;
145 const void *ns
; /* namespace tag */
146 unsigned int hash
; /* ns + name hash */
148 struct kernfs_elem_dir dir
;
149 struct kernfs_elem_symlink symlink
;
150 struct kernfs_elem_attr attr
;
156 * 64bit unique ID. On 64bit ino setups, id is the ino. On 32bit,
157 * the low 32bits are ino and upper generation.
161 unsigned short flags
;
163 struct kernfs_iattrs
*iattr
;
167 * kernfs_syscall_ops may be specified on kernfs_create_root() to support
168 * syscalls. These optional callbacks are invoked on the matching syscalls
169 * and can perform any kernfs operations which don't necessarily have to be
170 * the exact operation requested. An active reference is held for each
171 * kernfs_node parameter.
173 struct kernfs_syscall_ops
{
174 int (*show_options
)(struct seq_file
*sf
, struct kernfs_root
*root
);
176 int (*mkdir
)(struct kernfs_node
*parent
, const char *name
,
178 int (*rmdir
)(struct kernfs_node
*kn
);
179 int (*rename
)(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
180 const char *new_name
);
181 int (*show_path
)(struct seq_file
*sf
, struct kernfs_node
*kn
,
182 struct kernfs_root
*root
);
186 /* published fields */
187 struct kernfs_node
*kn
;
188 unsigned int flags
; /* KERNFS_ROOT_* flags */
190 /* private fields, do not use outside kernfs proper */
194 struct kernfs_syscall_ops
*syscall_ops
;
196 /* list of kernfs_super_info of this root, protected by kernfs_rwsem */
197 struct list_head supers
;
199 wait_queue_head_t deactivate_waitq
;
202 struct kernfs_open_file
{
203 /* published fields */
204 struct kernfs_node
*kn
;
206 struct seq_file
*seq_file
;
209 /* private fields, do not use outside kernfs proper */
211 struct mutex prealloc_mutex
;
213 struct list_head list
;
216 size_t atomic_write_len
;
219 const struct vm_operations_struct
*vm_ops
;
224 * Optional open/release methods. Both are called with
225 * @of->seq_file populated.
227 int (*open
)(struct kernfs_open_file
*of
);
228 void (*release
)(struct kernfs_open_file
*of
);
231 * Read is handled by either seq_file or raw_read().
233 * If seq_show() is present, seq_file path is active. Other seq
234 * operations are optional and if not implemented, the behavior is
235 * equivalent to single_open(). @sf->private points to the
236 * associated kernfs_open_file.
238 * read() is bounced through kernel buffer and a read larger than
239 * PAGE_SIZE results in partial operation of PAGE_SIZE.
241 int (*seq_show
)(struct seq_file
*sf
, void *v
);
243 void *(*seq_start
)(struct seq_file
*sf
, loff_t
*ppos
);
244 void *(*seq_next
)(struct seq_file
*sf
, void *v
, loff_t
*ppos
);
245 void (*seq_stop
)(struct seq_file
*sf
, void *v
);
247 ssize_t (*read
)(struct kernfs_open_file
*of
, char *buf
, size_t bytes
,
251 * write() is bounced through kernel buffer. If atomic_write_len
252 * is not set, a write larger than PAGE_SIZE results in partial
253 * operations of PAGE_SIZE chunks. If atomic_write_len is set,
254 * writes upto the specified size are executed atomically but
255 * larger ones are rejected with -E2BIG.
257 size_t atomic_write_len
;
259 * "prealloc" causes a buffer to be allocated at open for
260 * all read/write requests. As ->seq_show uses seq_read()
261 * which does its own allocation, it is incompatible with
262 * ->prealloc. Provide ->read and ->write with ->prealloc.
265 ssize_t (*write
)(struct kernfs_open_file
*of
, char *buf
, size_t bytes
,
268 __poll_t (*poll
)(struct kernfs_open_file
*of
,
269 struct poll_table_struct
*pt
);
271 int (*mmap
)(struct kernfs_open_file
*of
, struct vm_area_struct
*vma
);
273 #ifdef CONFIG_DEBUG_LOCK_ALLOC
274 struct lock_class_key lockdep_key
;
279 * The kernfs superblock creation/mount parameter context.
281 struct kernfs_fs_context
{
282 struct kernfs_root
*root
; /* Root of the hierarchy being mounted */
283 void *ns_tag
; /* Namespace tag of the mount (or NULL) */
284 unsigned long magic
; /* File system specific magic number */
286 /* The following are set/used by kernfs_mount() */
287 bool new_sb_created
; /* Set to T if we allocated a new sb */
292 static inline enum kernfs_node_type
kernfs_type(struct kernfs_node
*kn
)
294 return kn
->flags
& KERNFS_TYPE_MASK
;
297 static inline ino_t
kernfs_id_ino(u64 id
)
299 /* id is ino if ino_t is 64bit; otherwise, low 32bits */
300 if (sizeof(ino_t
) >= sizeof(u64
))
306 static inline u32
kernfs_id_gen(u64 id
)
308 /* gen is fixed at 1 if ino_t is 64bit; otherwise, high 32bits */
309 if (sizeof(ino_t
) >= sizeof(u64
))
315 static inline ino_t
kernfs_ino(struct kernfs_node
*kn
)
317 return kernfs_id_ino(kn
->id
);
320 static inline ino_t
kernfs_gen(struct kernfs_node
*kn
)
322 return kernfs_id_gen(kn
->id
);
326 * kernfs_enable_ns - enable namespace under a directory
327 * @kn: directory of interest, should be empty
329 * This is to be called right after @kn is created to enable namespace
330 * under it. All children of @kn must have non-NULL namespace tags and
331 * only the ones which match the super_block's tag will be visible.
333 static inline void kernfs_enable_ns(struct kernfs_node
*kn
)
335 WARN_ON_ONCE(kernfs_type(kn
) != KERNFS_DIR
);
336 WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn
->dir
.children
));
337 kn
->flags
|= KERNFS_NS
;
341 * kernfs_ns_enabled - test whether namespace is enabled
342 * @kn: the node to test
344 * Test whether namespace filtering is enabled for the children of @ns.
346 static inline bool kernfs_ns_enabled(struct kernfs_node
*kn
)
348 return kn
->flags
& KERNFS_NS
;
351 int kernfs_name(struct kernfs_node
*kn
, char *buf
, size_t buflen
);
352 int kernfs_path_from_node(struct kernfs_node
*root_kn
, struct kernfs_node
*kn
,
353 char *buf
, size_t buflen
);
354 void pr_cont_kernfs_name(struct kernfs_node
*kn
);
355 void pr_cont_kernfs_path(struct kernfs_node
*kn
);
356 struct kernfs_node
*kernfs_get_parent(struct kernfs_node
*kn
);
357 struct kernfs_node
*kernfs_find_and_get_ns(struct kernfs_node
*parent
,
358 const char *name
, const void *ns
);
359 struct kernfs_node
*kernfs_walk_and_get_ns(struct kernfs_node
*parent
,
360 const char *path
, const void *ns
);
361 void kernfs_get(struct kernfs_node
*kn
);
362 void kernfs_put(struct kernfs_node
*kn
);
364 struct kernfs_node
*kernfs_node_from_dentry(struct dentry
*dentry
);
365 struct kernfs_root
*kernfs_root_from_sb(struct super_block
*sb
);
366 struct inode
*kernfs_get_inode(struct super_block
*sb
, struct kernfs_node
*kn
);
368 struct dentry
*kernfs_node_dentry(struct kernfs_node
*kn
,
369 struct super_block
*sb
);
370 struct kernfs_root
*kernfs_create_root(struct kernfs_syscall_ops
*scops
,
371 unsigned int flags
, void *priv
);
372 void kernfs_destroy_root(struct kernfs_root
*root
);
374 struct kernfs_node
*kernfs_create_dir_ns(struct kernfs_node
*parent
,
375 const char *name
, umode_t mode
,
376 kuid_t uid
, kgid_t gid
,
377 void *priv
, const void *ns
);
378 struct kernfs_node
*kernfs_create_empty_dir(struct kernfs_node
*parent
,
380 struct kernfs_node
*__kernfs_create_file(struct kernfs_node
*parent
,
381 const char *name
, umode_t mode
,
382 kuid_t uid
, kgid_t gid
,
384 const struct kernfs_ops
*ops
,
385 void *priv
, const void *ns
,
386 struct lock_class_key
*key
);
387 struct kernfs_node
*kernfs_create_link(struct kernfs_node
*parent
,
389 struct kernfs_node
*target
);
390 void kernfs_activate(struct kernfs_node
*kn
);
391 void kernfs_remove(struct kernfs_node
*kn
);
392 void kernfs_break_active_protection(struct kernfs_node
*kn
);
393 void kernfs_unbreak_active_protection(struct kernfs_node
*kn
);
394 bool kernfs_remove_self(struct kernfs_node
*kn
);
395 int kernfs_remove_by_name_ns(struct kernfs_node
*parent
, const char *name
,
397 int kernfs_rename_ns(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
398 const char *new_name
, const void *new_ns
);
399 int kernfs_setattr(struct kernfs_node
*kn
, const struct iattr
*iattr
);
400 __poll_t
kernfs_generic_poll(struct kernfs_open_file
*of
,
401 struct poll_table_struct
*pt
);
402 void kernfs_notify(struct kernfs_node
*kn
);
404 int kernfs_xattr_get(struct kernfs_node
*kn
, const char *name
,
405 void *value
, size_t size
);
406 int kernfs_xattr_set(struct kernfs_node
*kn
, const char *name
,
407 const void *value
, size_t size
, int flags
);
409 const void *kernfs_super_ns(struct super_block
*sb
);
410 int kernfs_get_tree(struct fs_context
*fc
);
411 void kernfs_free_fs_context(struct fs_context
*fc
);
412 void kernfs_kill_sb(struct super_block
*sb
);
414 void kernfs_init(void);
416 struct kernfs_node
*kernfs_find_and_get_node_by_id(struct kernfs_root
*root
,
418 #else /* CONFIG_KERNFS */
420 static inline enum kernfs_node_type
kernfs_type(struct kernfs_node
*kn
)
421 { return 0; } /* whatever */
423 static inline void kernfs_enable_ns(struct kernfs_node
*kn
) { }
425 static inline bool kernfs_ns_enabled(struct kernfs_node
*kn
)
428 static inline int kernfs_name(struct kernfs_node
*kn
, char *buf
, size_t buflen
)
431 static inline int kernfs_path_from_node(struct kernfs_node
*root_kn
,
432 struct kernfs_node
*kn
,
433 char *buf
, size_t buflen
)
436 static inline void pr_cont_kernfs_name(struct kernfs_node
*kn
) { }
437 static inline void pr_cont_kernfs_path(struct kernfs_node
*kn
) { }
439 static inline struct kernfs_node
*kernfs_get_parent(struct kernfs_node
*kn
)
442 static inline struct kernfs_node
*
443 kernfs_find_and_get_ns(struct kernfs_node
*parent
, const char *name
,
446 static inline struct kernfs_node
*
447 kernfs_walk_and_get_ns(struct kernfs_node
*parent
, const char *path
,
451 static inline void kernfs_get(struct kernfs_node
*kn
) { }
452 static inline void kernfs_put(struct kernfs_node
*kn
) { }
454 static inline struct kernfs_node
*kernfs_node_from_dentry(struct dentry
*dentry
)
457 static inline struct kernfs_root
*kernfs_root_from_sb(struct super_block
*sb
)
460 static inline struct inode
*
461 kernfs_get_inode(struct super_block
*sb
, struct kernfs_node
*kn
)
464 static inline struct kernfs_root
*
465 kernfs_create_root(struct kernfs_syscall_ops
*scops
, unsigned int flags
,
467 { return ERR_PTR(-ENOSYS
); }
469 static inline void kernfs_destroy_root(struct kernfs_root
*root
) { }
471 static inline struct kernfs_node
*
472 kernfs_create_dir_ns(struct kernfs_node
*parent
, const char *name
,
473 umode_t mode
, kuid_t uid
, kgid_t gid
,
474 void *priv
, const void *ns
)
475 { return ERR_PTR(-ENOSYS
); }
477 static inline struct kernfs_node
*
478 __kernfs_create_file(struct kernfs_node
*parent
, const char *name
,
479 umode_t mode
, kuid_t uid
, kgid_t gid
,
480 loff_t size
, const struct kernfs_ops
*ops
,
481 void *priv
, const void *ns
, struct lock_class_key
*key
)
482 { return ERR_PTR(-ENOSYS
); }
484 static inline struct kernfs_node
*
485 kernfs_create_link(struct kernfs_node
*parent
, const char *name
,
486 struct kernfs_node
*target
)
487 { return ERR_PTR(-ENOSYS
); }
489 static inline void kernfs_activate(struct kernfs_node
*kn
) { }
491 static inline void kernfs_remove(struct kernfs_node
*kn
) { }
493 static inline bool kernfs_remove_self(struct kernfs_node
*kn
)
496 static inline int kernfs_remove_by_name_ns(struct kernfs_node
*kn
,
497 const char *name
, const void *ns
)
500 static inline int kernfs_rename_ns(struct kernfs_node
*kn
,
501 struct kernfs_node
*new_parent
,
502 const char *new_name
, const void *new_ns
)
505 static inline int kernfs_setattr(struct kernfs_node
*kn
,
506 const struct iattr
*iattr
)
509 static inline void kernfs_notify(struct kernfs_node
*kn
) { }
511 static inline int kernfs_xattr_get(struct kernfs_node
*kn
, const char *name
,
512 void *value
, size_t size
)
515 static inline int kernfs_xattr_set(struct kernfs_node
*kn
, const char *name
,
516 const void *value
, size_t size
, int flags
)
519 static inline const void *kernfs_super_ns(struct super_block
*sb
)
522 static inline int kernfs_get_tree(struct fs_context
*fc
)
525 static inline void kernfs_free_fs_context(struct fs_context
*fc
) { }
527 static inline void kernfs_kill_sb(struct super_block
*sb
) { }
529 static inline void kernfs_init(void) { }
531 #endif /* CONFIG_KERNFS */
534 * kernfs_path - build full path of a given node
535 * @kn: kernfs_node of interest
536 * @buf: buffer to copy @kn's name into
537 * @buflen: size of @buf
539 * If @kn is NULL result will be "(null)".
541 * Returns the length of the full path. If the full length is equal to or
542 * greater than @buflen, @buf contains the truncated path with the trailing
543 * '\0'. On error, -errno is returned.
545 static inline int kernfs_path(struct kernfs_node
*kn
, char *buf
, size_t buflen
)
547 return kernfs_path_from_node(kn
, NULL
, buf
, buflen
);
550 static inline struct kernfs_node
*
551 kernfs_find_and_get(struct kernfs_node
*kn
, const char *name
)
553 return kernfs_find_and_get_ns(kn
, name
, NULL
);
556 static inline struct kernfs_node
*
557 kernfs_walk_and_get(struct kernfs_node
*kn
, const char *path
)
559 return kernfs_walk_and_get_ns(kn
, path
, NULL
);
562 static inline struct kernfs_node
*
563 kernfs_create_dir(struct kernfs_node
*parent
, const char *name
, umode_t mode
,
566 return kernfs_create_dir_ns(parent
, name
, mode
,
567 GLOBAL_ROOT_UID
, GLOBAL_ROOT_GID
,
571 static inline struct kernfs_node
*
572 kernfs_create_file_ns(struct kernfs_node
*parent
, const char *name
,
573 umode_t mode
, kuid_t uid
, kgid_t gid
,
574 loff_t size
, const struct kernfs_ops
*ops
,
575 void *priv
, const void *ns
)
577 struct lock_class_key
*key
= NULL
;
579 #ifdef CONFIG_DEBUG_LOCK_ALLOC
580 key
= (struct lock_class_key
*)&ops
->lockdep_key
;
582 return __kernfs_create_file(parent
, name
, mode
, uid
, gid
,
583 size
, ops
, priv
, ns
, key
);
586 static inline struct kernfs_node
*
587 kernfs_create_file(struct kernfs_node
*parent
, const char *name
, umode_t mode
,
588 loff_t size
, const struct kernfs_ops
*ops
, void *priv
)
590 return kernfs_create_file_ns(parent
, name
, mode
,
591 GLOBAL_ROOT_UID
, GLOBAL_ROOT_GID
,
592 size
, ops
, priv
, NULL
);
595 static inline int kernfs_remove_by_name(struct kernfs_node
*parent
,
598 return kernfs_remove_by_name_ns(parent
, name
, NULL
);
601 static inline int kernfs_rename(struct kernfs_node
*kn
,
602 struct kernfs_node
*new_parent
,
603 const char *new_name
)
605 return kernfs_rename_ns(kn
, new_parent
, new_name
, NULL
);
608 #endif /* __LINUX_KERNFS_H */