Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0-only */
2 : /*
3 : * kernfs.h - pseudo filesystem decoupled from vfs locking
4 : */
5 :
6 : #ifndef __LINUX_KERNFS_H
7 : #define __LINUX_KERNFS_H
8 :
9 : #include <linux/err.h>
10 : #include <linux/list.h>
11 : #include <linux/mutex.h>
12 : #include <linux/idr.h>
13 : #include <linux/lockdep.h>
14 : #include <linux/rbtree.h>
15 : #include <linux/atomic.h>
16 : #include <linux/bug.h>
17 : #include <linux/types.h>
18 : #include <linux/uidgid.h>
19 : #include <linux/wait.h>
20 : #include <linux/rwsem.h>
21 :
22 : struct file;
23 : struct dentry;
24 : struct iattr;
25 : struct seq_file;
26 : struct vm_area_struct;
27 : struct vm_operations_struct;
28 : struct super_block;
29 : struct file_system_type;
30 : struct poll_table_struct;
31 : struct fs_context;
32 :
33 : struct kernfs_fs_context;
34 : struct kernfs_open_node;
35 : struct kernfs_iattrs;
36 :
37 : enum kernfs_node_type {
38 : KERNFS_DIR = 0x0001,
39 : KERNFS_FILE = 0x0002,
40 : KERNFS_LINK = 0x0004,
41 : };
42 :
43 : #define KERNFS_TYPE_MASK 0x000f
44 : #define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
45 : #define KERNFS_MAX_USER_XATTRS 128
46 : #define KERNFS_USER_XATTR_SIZE_LIMIT (128 << 10)
47 :
48 : enum kernfs_node_flag {
49 : KERNFS_ACTIVATED = 0x0010,
50 : KERNFS_NS = 0x0020,
51 : KERNFS_HAS_SEQ_SHOW = 0x0040,
52 : KERNFS_HAS_MMAP = 0x0080,
53 : KERNFS_LOCKDEP = 0x0100,
54 : KERNFS_SUICIDAL = 0x0400,
55 : KERNFS_SUICIDED = 0x0800,
56 : KERNFS_EMPTY_DIR = 0x1000,
57 : KERNFS_HAS_RELEASE = 0x2000,
58 : };
59 :
60 : /* @flags for kernfs_create_root() */
61 : enum kernfs_root_flag {
62 : /*
63 : * kernfs_nodes are created in the deactivated state and invisible.
64 : * They require explicit kernfs_activate() to become visible. This
65 : * can be used to make related nodes become visible atomically
66 : * after all nodes are created successfully.
67 : */
68 : KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
69 :
70 : /*
71 : * For regular files, if the opener has CAP_DAC_OVERRIDE, open(2)
72 : * succeeds regardless of the RW permissions. sysfs had an extra
73 : * layer of enforcement where open(2) fails with -EACCES regardless
74 : * of CAP_DAC_OVERRIDE if the permission doesn't have the
75 : * respective read or write access at all (none of S_IRUGO or
76 : * S_IWUGO) or the respective operation isn't implemented. The
77 : * following flag enables that behavior.
78 : */
79 : KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK = 0x0002,
80 :
81 : /*
82 : * The filesystem supports exportfs operation, so userspace can use
83 : * fhandle to access nodes of the fs.
84 : */
85 : KERNFS_ROOT_SUPPORT_EXPORTOP = 0x0004,
86 :
87 : /*
88 : * Support user xattrs to be written to nodes rooted at this root.
89 : */
90 : KERNFS_ROOT_SUPPORT_USER_XATTR = 0x0008,
91 : };
92 :
93 : /* type-specific structures for kernfs_node union members */
94 : struct kernfs_elem_dir {
95 : unsigned long subdirs;
96 : /* children rbtree starts here and goes through kn->rb */
97 : struct rb_root children;
98 :
99 : /*
100 : * The kernfs hierarchy this directory belongs to. This fits
101 : * better directly in kernfs_node but is here to save space.
102 : */
103 : struct kernfs_root *root;
104 : /*
105 : * Monotonic revision counter, used to identify if a directory
106 : * node has changed during negative dentry revalidation.
107 : */
108 : unsigned long rev;
109 : };
110 :
111 : struct kernfs_elem_symlink {
112 : struct kernfs_node *target_kn;
113 : };
114 :
115 : struct kernfs_elem_attr {
116 : const struct kernfs_ops *ops;
117 : struct kernfs_open_node *open;
118 : loff_t size;
119 : struct kernfs_node *notify_next; /* for kernfs_notify() */
120 : };
121 :
122 : /*
123 : * kernfs_node - the building block of kernfs hierarchy. Each and every
124 : * kernfs node is represented by single kernfs_node. Most fields are
125 : * private to kernfs and shouldn't be accessed directly by kernfs users.
126 : *
127 : * As long as count reference is held, the kernfs_node itself is
128 : * accessible. Dereferencing elem or any other outer entity requires
129 : * active reference.
130 : */
131 : struct kernfs_node {
132 : atomic_t count;
133 : atomic_t active;
134 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
135 : struct lockdep_map dep_map;
136 : #endif
137 : /*
138 : * Use kernfs_get_parent() and kernfs_name/path() instead of
139 : * accessing the following two fields directly. If the node is
140 : * never moved to a different parent, it is safe to access the
141 : * parent directly.
142 : */
143 : struct kernfs_node *parent;
144 : const char *name;
145 :
146 : struct rb_node rb;
147 :
148 : const void *ns; /* namespace tag */
149 : unsigned int hash; /* ns + name hash */
150 : union {
151 : struct kernfs_elem_dir dir;
152 : struct kernfs_elem_symlink symlink;
153 : struct kernfs_elem_attr attr;
154 : };
155 :
156 : void *priv;
157 :
158 : /*
159 : * 64bit unique ID. On 64bit ino setups, id is the ino. On 32bit,
160 : * the low 32bits are ino and upper generation.
161 : */
162 : u64 id;
163 :
164 : unsigned short flags;
165 : umode_t mode;
166 : struct kernfs_iattrs *iattr;
167 : };
168 :
169 : /*
170 : * kernfs_syscall_ops may be specified on kernfs_create_root() to support
171 : * syscalls. These optional callbacks are invoked on the matching syscalls
172 : * and can perform any kernfs operations which don't necessarily have to be
173 : * the exact operation requested. An active reference is held for each
174 : * kernfs_node parameter.
175 : */
176 : struct kernfs_syscall_ops {
177 : int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
178 :
179 : int (*mkdir)(struct kernfs_node *parent, const char *name,
180 : umode_t mode);
181 : int (*rmdir)(struct kernfs_node *kn);
182 : int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
183 : const char *new_name);
184 : int (*show_path)(struct seq_file *sf, struct kernfs_node *kn,
185 : struct kernfs_root *root);
186 : };
187 :
188 : struct kernfs_node *kernfs_root_to_node(struct kernfs_root *root);
189 :
190 : struct kernfs_open_file {
191 : /* published fields */
192 : struct kernfs_node *kn;
193 : struct file *file;
194 : struct seq_file *seq_file;
195 : void *priv;
196 :
197 : /* private fields, do not use outside kernfs proper */
198 : struct mutex mutex;
199 : struct mutex prealloc_mutex;
200 : int event;
201 : struct list_head list;
202 : char *prealloc_buf;
203 :
204 : size_t atomic_write_len;
205 : bool mmapped:1;
206 : bool released:1;
207 : const struct vm_operations_struct *vm_ops;
208 : };
209 :
210 : struct kernfs_ops {
211 : /*
212 : * Optional open/release methods. Both are called with
213 : * @of->seq_file populated.
214 : */
215 : int (*open)(struct kernfs_open_file *of);
216 : void (*release)(struct kernfs_open_file *of);
217 :
218 : /*
219 : * Read is handled by either seq_file or raw_read().
220 : *
221 : * If seq_show() is present, seq_file path is active. Other seq
222 : * operations are optional and if not implemented, the behavior is
223 : * equivalent to single_open(). @sf->private points to the
224 : * associated kernfs_open_file.
225 : *
226 : * read() is bounced through kernel buffer and a read larger than
227 : * PAGE_SIZE results in partial operation of PAGE_SIZE.
228 : */
229 : int (*seq_show)(struct seq_file *sf, void *v);
230 :
231 : void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
232 : void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
233 : void (*seq_stop)(struct seq_file *sf, void *v);
234 :
235 : ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
236 : loff_t off);
237 :
238 : /*
239 : * write() is bounced through kernel buffer. If atomic_write_len
240 : * is not set, a write larger than PAGE_SIZE results in partial
241 : * operations of PAGE_SIZE chunks. If atomic_write_len is set,
242 : * writes upto the specified size are executed atomically but
243 : * larger ones are rejected with -E2BIG.
244 : */
245 : size_t atomic_write_len;
246 : /*
247 : * "prealloc" causes a buffer to be allocated at open for
248 : * all read/write requests. As ->seq_show uses seq_read()
249 : * which does its own allocation, it is incompatible with
250 : * ->prealloc. Provide ->read and ->write with ->prealloc.
251 : */
252 : bool prealloc;
253 : ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
254 : loff_t off);
255 :
256 : __poll_t (*poll)(struct kernfs_open_file *of,
257 : struct poll_table_struct *pt);
258 :
259 : int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
260 : };
261 :
262 : /*
263 : * The kernfs superblock creation/mount parameter context.
264 : */
265 : struct kernfs_fs_context {
266 : struct kernfs_root *root; /* Root of the hierarchy being mounted */
267 : void *ns_tag; /* Namespace tag of the mount (or NULL) */
268 : unsigned long magic; /* File system specific magic number */
269 :
270 : /* The following are set/used by kernfs_mount() */
271 : bool new_sb_created; /* Set to T if we allocated a new sb */
272 : };
273 :
274 : #ifdef CONFIG_KERNFS
275 :
276 : static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
277 : {
278 26751 : return kn->flags & KERNFS_TYPE_MASK;
279 : }
280 :
281 : static inline ino_t kernfs_id_ino(u64 id)
282 : {
283 : /* id is ino if ino_t is 64bit; otherwise, low 32bits */
284 : if (sizeof(ino_t) >= sizeof(u64))
285 : return id;
286 : else
287 : return (u32)id;
288 : }
289 :
290 : static inline u32 kernfs_id_gen(u64 id)
291 : {
292 : /* gen is fixed at 1 if ino_t is 64bit; otherwise, high 32bits */
293 : if (sizeof(ino_t) >= sizeof(u64))
294 : return 1;
295 : else
296 : return id >> 32;
297 : }
298 :
299 : static inline ino_t kernfs_ino(struct kernfs_node *kn)
300 : {
301 2325 : return kernfs_id_ino(kn->id);
302 : }
303 :
304 : static inline ino_t kernfs_gen(struct kernfs_node *kn)
305 : {
306 0 : return kernfs_id_gen(kn->id);
307 : }
308 :
309 : /**
310 : * kernfs_enable_ns - enable namespace under a directory
311 : * @kn: directory of interest, should be empty
312 : *
313 : * This is to be called right after @kn is created to enable namespace
314 : * under it. All children of @kn must have non-NULL namespace tags and
315 : * only the ones which match the super_block's tag will be visible.
316 : */
317 0 : static inline void kernfs_enable_ns(struct kernfs_node *kn)
318 : {
319 0 : WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
320 0 : WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
321 0 : kn->flags |= KERNFS_NS;
322 0 : }
323 :
324 : /**
325 : * kernfs_ns_enabled - test whether namespace is enabled
326 : * @kn: the node to test
327 : *
328 : * Test whether namespace filtering is enabled for the children of @ns.
329 : */
330 : static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
331 : {
332 14000 : return kn->flags & KERNFS_NS;
333 : }
334 :
335 : int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
336 : int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn,
337 : char *buf, size_t buflen);
338 : void pr_cont_kernfs_name(struct kernfs_node *kn);
339 : void pr_cont_kernfs_path(struct kernfs_node *kn);
340 : struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
341 : struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
342 : const char *name, const void *ns);
343 : struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
344 : const char *path, const void *ns);
345 : void kernfs_get(struct kernfs_node *kn);
346 : void kernfs_put(struct kernfs_node *kn);
347 :
348 : struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
349 : struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
350 : struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
351 :
352 : struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
353 : struct super_block *sb);
354 : struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
355 : unsigned int flags, void *priv);
356 : void kernfs_destroy_root(struct kernfs_root *root);
357 :
358 : struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
359 : const char *name, umode_t mode,
360 : kuid_t uid, kgid_t gid,
361 : void *priv, const void *ns);
362 : struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
363 : const char *name);
364 : struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
365 : const char *name, umode_t mode,
366 : kuid_t uid, kgid_t gid,
367 : loff_t size,
368 : const struct kernfs_ops *ops,
369 : void *priv, const void *ns,
370 : struct lock_class_key *key);
371 : struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
372 : const char *name,
373 : struct kernfs_node *target);
374 : void kernfs_activate(struct kernfs_node *kn);
375 : void kernfs_remove(struct kernfs_node *kn);
376 : void kernfs_break_active_protection(struct kernfs_node *kn);
377 : void kernfs_unbreak_active_protection(struct kernfs_node *kn);
378 : bool kernfs_remove_self(struct kernfs_node *kn);
379 : int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
380 : const void *ns);
381 : int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
382 : const char *new_name, const void *new_ns);
383 : int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
384 : __poll_t kernfs_generic_poll(struct kernfs_open_file *of,
385 : struct poll_table_struct *pt);
386 : void kernfs_notify(struct kernfs_node *kn);
387 :
388 : int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
389 : void *value, size_t size);
390 : int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
391 : const void *value, size_t size, int flags);
392 :
393 : const void *kernfs_super_ns(struct super_block *sb);
394 : int kernfs_get_tree(struct fs_context *fc);
395 : void kernfs_free_fs_context(struct fs_context *fc);
396 : void kernfs_kill_sb(struct super_block *sb);
397 :
398 : void kernfs_init(void);
399 :
400 : struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
401 : u64 id);
402 : #else /* CONFIG_KERNFS */
403 :
404 : static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
405 : { return 0; } /* whatever */
406 :
407 : static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
408 :
409 : static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
410 : { return false; }
411 :
412 : static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
413 : { return -ENOSYS; }
414 :
415 : static inline int kernfs_path_from_node(struct kernfs_node *root_kn,
416 : struct kernfs_node *kn,
417 : char *buf, size_t buflen)
418 : { return -ENOSYS; }
419 :
420 : static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
421 : static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
422 :
423 : static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
424 : { return NULL; }
425 :
426 : static inline struct kernfs_node *
427 : kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
428 : const void *ns)
429 : { return NULL; }
430 : static inline struct kernfs_node *
431 : kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
432 : const void *ns)
433 : { return NULL; }
434 :
435 : static inline void kernfs_get(struct kernfs_node *kn) { }
436 : static inline void kernfs_put(struct kernfs_node *kn) { }
437 :
438 : static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
439 : { return NULL; }
440 :
441 : static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
442 : { return NULL; }
443 :
444 : static inline struct inode *
445 : kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
446 : { return NULL; }
447 :
448 : static inline struct kernfs_root *
449 : kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
450 : void *priv)
451 : { return ERR_PTR(-ENOSYS); }
452 :
453 : static inline void kernfs_destroy_root(struct kernfs_root *root) { }
454 :
455 : static inline struct kernfs_node *
456 : kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
457 : umode_t mode, kuid_t uid, kgid_t gid,
458 : void *priv, const void *ns)
459 : { return ERR_PTR(-ENOSYS); }
460 :
461 : static inline struct kernfs_node *
462 : __kernfs_create_file(struct kernfs_node *parent, const char *name,
463 : umode_t mode, kuid_t uid, kgid_t gid,
464 : loff_t size, const struct kernfs_ops *ops,
465 : void *priv, const void *ns, struct lock_class_key *key)
466 : { return ERR_PTR(-ENOSYS); }
467 :
468 : static inline struct kernfs_node *
469 : kernfs_create_link(struct kernfs_node *parent, const char *name,
470 : struct kernfs_node *target)
471 : { return ERR_PTR(-ENOSYS); }
472 :
473 : static inline void kernfs_activate(struct kernfs_node *kn) { }
474 :
475 : static inline void kernfs_remove(struct kernfs_node *kn) { }
476 :
477 : static inline bool kernfs_remove_self(struct kernfs_node *kn)
478 : { return false; }
479 :
480 : static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
481 : const char *name, const void *ns)
482 : { return -ENOSYS; }
483 :
484 : static inline int kernfs_rename_ns(struct kernfs_node *kn,
485 : struct kernfs_node *new_parent,
486 : const char *new_name, const void *new_ns)
487 : { return -ENOSYS; }
488 :
489 : static inline int kernfs_setattr(struct kernfs_node *kn,
490 : const struct iattr *iattr)
491 : { return -ENOSYS; }
492 :
493 : static inline void kernfs_notify(struct kernfs_node *kn) { }
494 :
495 : static inline int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
496 : void *value, size_t size)
497 : { return -ENOSYS; }
498 :
499 : static inline int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
500 : const void *value, size_t size, int flags)
501 : { return -ENOSYS; }
502 :
503 : static inline const void *kernfs_super_ns(struct super_block *sb)
504 : { return NULL; }
505 :
506 : static inline int kernfs_get_tree(struct fs_context *fc)
507 : { return -ENOSYS; }
508 :
509 : static inline void kernfs_free_fs_context(struct fs_context *fc) { }
510 :
511 : static inline void kernfs_kill_sb(struct super_block *sb) { }
512 :
513 : static inline void kernfs_init(void) { }
514 :
515 : #endif /* CONFIG_KERNFS */
516 :
517 : /**
518 : * kernfs_path - build full path of a given node
519 : * @kn: kernfs_node of interest
520 : * @buf: buffer to copy @kn's name into
521 : * @buflen: size of @buf
522 : *
523 : * If @kn is NULL result will be "(null)".
524 : *
525 : * Returns the length of the full path. If the full length is equal to or
526 : * greater than @buflen, @buf contains the truncated path with the trailing
527 : * '\0'. On error, -errno is returned.
528 : */
529 : static inline int kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
530 : {
531 0 : return kernfs_path_from_node(kn, NULL, buf, buflen);
532 : }
533 :
534 : static inline struct kernfs_node *
535 : kernfs_find_and_get(struct kernfs_node *kn, const char *name)
536 : {
537 633 : return kernfs_find_and_get_ns(kn, name, NULL);
538 : }
539 :
540 : static inline struct kernfs_node *
541 : kernfs_walk_and_get(struct kernfs_node *kn, const char *path)
542 : {
543 : return kernfs_walk_and_get_ns(kn, path, NULL);
544 : }
545 :
546 : static inline struct kernfs_node *
547 : kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
548 : void *priv)
549 : {
550 : return kernfs_create_dir_ns(parent, name, mode,
551 : GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
552 : priv, NULL);
553 : }
554 :
555 : static inline int kernfs_remove_by_name(struct kernfs_node *parent,
556 : const char *name)
557 : {
558 2315 : return kernfs_remove_by_name_ns(parent, name, NULL);
559 : }
560 :
561 : static inline int kernfs_rename(struct kernfs_node *kn,
562 : struct kernfs_node *new_parent,
563 : const char *new_name)
564 : {
565 : return kernfs_rename_ns(kn, new_parent, new_name, NULL);
566 : }
567 :
568 : #endif /* __LINUX_KERNFS_H */
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