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1 /*
2 * kernfs.h - pseudo filesystem decoupled from vfs locking
3 *
4 * This file is released under the GPLv2.
5 */
6
7 #ifndef __LINUX_KERNFS_H
8 #define __LINUX_KERNFS_H
9
10 #include <linux/kernel.h>
11 #include <linux/err.h>
12 #include <linux/list.h>
13 #include <linux/mutex.h>
14 #include <linux/idr.h>
15 #include <linux/lockdep.h>
16 #include <linux/rbtree.h>
17 #include <linux/atomic.h>
18 #include <linux/wait.h>
19
20 struct file;
21 struct dentry;
22 struct iattr;
23 struct seq_file;
24 struct vm_area_struct;
25 struct super_block;
26 struct file_system_type;
27
28 struct kernfs_open_node;
29 struct kernfs_iattrs;
30
31 enum kernfs_node_type {
32 KERNFS_DIR = 0x0001,
33 KERNFS_FILE = 0x0002,
34 KERNFS_LINK = 0x0004,
35 };
36
37 #define KERNFS_TYPE_MASK 0x000f
38 #define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
39
40 enum kernfs_node_flag {
41 KERNFS_ACTIVATED = 0x0010,
42 KERNFS_NS = 0x0020,
43 KERNFS_HAS_SEQ_SHOW = 0x0040,
44 KERNFS_HAS_MMAP = 0x0080,
45 KERNFS_LOCKDEP = 0x0100,
46 KERNFS_STATIC_NAME = 0x0200,
47 KERNFS_SUICIDAL = 0x0400,
48 KERNFS_SUICIDED = 0x0800,
49 };
50
51 /* @flags for kernfs_create_root() */
52 enum kernfs_root_flag {
53 /*
54 * kernfs_nodes are created in the deactivated state and invisible.
55 * They require explicit kernfs_activate() to become visible. This
56 * can be used to make related nodes become visible atomically
57 * after all nodes are created successfully.
58 */
59 KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
60
61 /*
62 * For regular flies, if the opener has CAP_DAC_OVERRIDE, open(2)
63 * succeeds regardless of the RW permissions. sysfs had an extra
64 * layer of enforcement where open(2) fails with -EACCES regardless
65 * of CAP_DAC_OVERRIDE if the permission doesn't have the
66 * respective read or write access at all (none of S_IRUGO or
67 * S_IWUGO) or the respective operation isn't implemented. The
68 * following flag enables that behavior.
69 */
70 KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK = 0x0002,
71 };
72
73 /* type-specific structures for kernfs_node union members */
74 struct kernfs_elem_dir {
75 unsigned long subdirs;
76 /* children rbtree starts here and goes through kn->rb */
77 struct rb_root children;
78
79 /*
80 * The kernfs hierarchy this directory belongs to. This fits
81 * better directly in kernfs_node but is here to save space.
82 */
83 struct kernfs_root *root;
84 };
85
86 struct kernfs_elem_symlink {
87 struct kernfs_node *target_kn;
88 };
89
90 struct kernfs_elem_attr {
91 const struct kernfs_ops *ops;
92 struct kernfs_open_node *open;
93 loff_t size;
94 };
95
96 /*
97 * kernfs_node - the building block of kernfs hierarchy. Each and every
98 * kernfs node is represented by single kernfs_node. Most fields are
99 * private to kernfs and shouldn't be accessed directly by kernfs users.
100 *
101 * As long as s_count reference is held, the kernfs_node itself is
102 * accessible. Dereferencing elem or any other outer entity requires
103 * active reference.
104 */
105 struct kernfs_node {
106 atomic_t count;
107 atomic_t active;
108 #ifdef CONFIG_DEBUG_LOCK_ALLOC
109 struct lockdep_map dep_map;
110 #endif
111 /*
112 * Use kernfs_get_parent() and kernfs_name/path() instead of
113 * accessing the following two fields directly. If the node is
114 * never moved to a different parent, it is safe to access the
115 * parent directly.
116 */
117 struct kernfs_node *parent;
118 const char *name;
119
120 struct rb_node rb;
121
122 const void *ns; /* namespace tag */
123 unsigned int hash; /* ns + name hash */
124 union {
125 struct kernfs_elem_dir dir;
126 struct kernfs_elem_symlink symlink;
127 struct kernfs_elem_attr attr;
128 };
129
130 void *priv;
131
132 unsigned short flags;
133 umode_t mode;
134 unsigned int ino;
135 struct kernfs_iattrs *iattr;
136 };
137
138 /*
139 * kernfs_syscall_ops may be specified on kernfs_create_root() to support
140 * syscalls. These optional callbacks are invoked on the matching syscalls
141 * and can perform any kernfs operations which don't necessarily have to be
142 * the exact operation requested. An active reference is held for each
143 * kernfs_node parameter.
144 */
145 struct kernfs_syscall_ops {
146 int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
147 int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
148
149 int (*mkdir)(struct kernfs_node *parent, const char *name,
150 umode_t mode);
151 int (*rmdir)(struct kernfs_node *kn);
152 int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
153 const char *new_name);
154 };
155
156 struct kernfs_root {
157 /* published fields */
158 struct kernfs_node *kn;
159 unsigned int flags; /* KERNFS_ROOT_* flags */
160
161 /* private fields, do not use outside kernfs proper */
162 struct ida ino_ida;
163 struct kernfs_syscall_ops *syscall_ops;
164
165 /* list of kernfs_super_info of this root, protected by kernfs_mutex */
166 struct list_head supers;
167
168 wait_queue_head_t deactivate_waitq;
169 };
170
171 struct kernfs_open_file {
172 /* published fields */
173 struct kernfs_node *kn;
174 struct file *file;
175 void *priv;
176
177 /* private fields, do not use outside kernfs proper */
178 struct mutex mutex;
179 int event;
180 struct list_head list;
181
182 size_t atomic_write_len;
183 bool mmapped;
184 const struct vm_operations_struct *vm_ops;
185 };
186
187 struct kernfs_ops {
188 /*
189 * Read is handled by either seq_file or raw_read().
190 *
191 * If seq_show() is present, seq_file path is active. Other seq
192 * operations are optional and if not implemented, the behavior is
193 * equivalent to single_open(). @sf->private points to the
194 * associated kernfs_open_file.
195 *
196 * read() is bounced through kernel buffer and a read larger than
197 * PAGE_SIZE results in partial operation of PAGE_SIZE.
198 */
199 int (*seq_show)(struct seq_file *sf, void *v);
200
201 void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
202 void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
203 void (*seq_stop)(struct seq_file *sf, void *v);
204
205 ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
206 loff_t off);
207
208 /*
209 * write() is bounced through kernel buffer. If atomic_write_len
210 * is not set, a write larger than PAGE_SIZE results in partial
211 * operations of PAGE_SIZE chunks. If atomic_write_len is set,
212 * writes upto the specified size are executed atomically but
213 * larger ones are rejected with -E2BIG.
214 */
215 size_t atomic_write_len;
216 ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
217 loff_t off);
218
219 int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
220
221 #ifdef CONFIG_DEBUG_LOCK_ALLOC
222 struct lock_class_key lockdep_key;
223 #endif
224 };
225
226 #ifdef CONFIG_KERNFS
227
228 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
229 {
230 return kn->flags & KERNFS_TYPE_MASK;
231 }
232
233 /**
234 * kernfs_enable_ns - enable namespace under a directory
235 * @kn: directory of interest, should be empty
236 *
237 * This is to be called right after @kn is created to enable namespace
238 * under it. All children of @kn must have non-NULL namespace tags and
239 * only the ones which match the super_block's tag will be visible.
240 */
241 static inline void kernfs_enable_ns(struct kernfs_node *kn)
242 {
243 WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
244 WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
245 kn->flags |= KERNFS_NS;
246 }
247
248 /**
249 * kernfs_ns_enabled - test whether namespace is enabled
250 * @kn: the node to test
251 *
252 * Test whether namespace filtering is enabled for the children of @ns.
253 */
254 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
255 {
256 return kn->flags & KERNFS_NS;
257 }
258
259 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
260 char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
261 size_t buflen);
262 void pr_cont_kernfs_name(struct kernfs_node *kn);
263 void pr_cont_kernfs_path(struct kernfs_node *kn);
264 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
265 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
266 const char *name, const void *ns);
267 void kernfs_get(struct kernfs_node *kn);
268 void kernfs_put(struct kernfs_node *kn);
269
270 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
271 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
272
273 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
274 unsigned int flags, void *priv);
275 void kernfs_destroy_root(struct kernfs_root *root);
276
277 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
278 const char *name, umode_t mode,
279 void *priv, const void *ns);
280 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
281 const char *name,
282 umode_t mode, loff_t size,
283 const struct kernfs_ops *ops,
284 void *priv, const void *ns,
285 bool name_is_static,
286 struct lock_class_key *key);
287 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
288 const char *name,
289 struct kernfs_node *target);
290 void kernfs_activate(struct kernfs_node *kn);
291 void kernfs_remove(struct kernfs_node *kn);
292 void kernfs_break_active_protection(struct kernfs_node *kn);
293 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
294 bool kernfs_remove_self(struct kernfs_node *kn);
295 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
296 const void *ns);
297 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
298 const char *new_name, const void *new_ns);
299 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
300 void kernfs_notify(struct kernfs_node *kn);
301
302 const void *kernfs_super_ns(struct super_block *sb);
303 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
304 struct kernfs_root *root, unsigned long magic,
305 bool *new_sb_created, const void *ns);
306 void kernfs_kill_sb(struct super_block *sb);
307
308 void kernfs_init(void);
309
310 #else /* CONFIG_KERNFS */
311
312 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
313 { return 0; } /* whatever */
314
315 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
316
317 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
318 { return false; }
319
320 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
321 { return -ENOSYS; }
322
323 static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
324 size_t buflen)
325 { return NULL; }
326
327 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
328 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
329
330 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
331 { return NULL; }
332
333 static inline struct kernfs_node *
334 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
335 const void *ns)
336 { return NULL; }
337
338 static inline void kernfs_get(struct kernfs_node *kn) { }
339 static inline void kernfs_put(struct kernfs_node *kn) { }
340
341 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
342 { return NULL; }
343
344 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
345 { return NULL; }
346
347 static inline struct kernfs_root *
348 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
349 void *priv)
350 { return ERR_PTR(-ENOSYS); }
351
352 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
353
354 static inline struct kernfs_node *
355 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
356 umode_t mode, void *priv, const void *ns)
357 { return ERR_PTR(-ENOSYS); }
358
359 static inline struct kernfs_node *
360 __kernfs_create_file(struct kernfs_node *parent, const char *name,
361 umode_t mode, loff_t size, const struct kernfs_ops *ops,
362 void *priv, const void *ns, bool name_is_static,
363 struct lock_class_key *key)
364 { return ERR_PTR(-ENOSYS); }
365
366 static inline struct kernfs_node *
367 kernfs_create_link(struct kernfs_node *parent, const char *name,
368 struct kernfs_node *target)
369 { return ERR_PTR(-ENOSYS); }
370
371 static inline void kernfs_activate(struct kernfs_node *kn) { }
372
373 static inline void kernfs_remove(struct kernfs_node *kn) { }
374
375 static inline bool kernfs_remove_self(struct kernfs_node *kn)
376 { return false; }
377
378 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
379 const char *name, const void *ns)
380 { return -ENOSYS; }
381
382 static inline int kernfs_rename_ns(struct kernfs_node *kn,
383 struct kernfs_node *new_parent,
384 const char *new_name, const void *new_ns)
385 { return -ENOSYS; }
386
387 static inline int kernfs_setattr(struct kernfs_node *kn,
388 const struct iattr *iattr)
389 { return -ENOSYS; }
390
391 static inline void kernfs_notify(struct kernfs_node *kn) { }
392
393 static inline const void *kernfs_super_ns(struct super_block *sb)
394 { return NULL; }
395
396 static inline struct dentry *
397 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
398 struct kernfs_root *root, unsigned long magic,
399 bool *new_sb_created, const void *ns)
400 { return ERR_PTR(-ENOSYS); }
401
402 static inline void kernfs_kill_sb(struct super_block *sb) { }
403
404 static inline void kernfs_init(void) { }
405
406 #endif /* CONFIG_KERNFS */
407
408 static inline struct kernfs_node *
409 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
410 {
411 return kernfs_find_and_get_ns(kn, name, NULL);
412 }
413
414 static inline struct kernfs_node *
415 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
416 void *priv)
417 {
418 return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
419 }
420
421 static inline struct kernfs_node *
422 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
423 umode_t mode, loff_t size, const struct kernfs_ops *ops,
424 void *priv, const void *ns)
425 {
426 struct lock_class_key *key = NULL;
427
428 #ifdef CONFIG_DEBUG_LOCK_ALLOC
429 key = (struct lock_class_key *)&ops->lockdep_key;
430 #endif
431 return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
432 false, key);
433 }
434
435 static inline struct kernfs_node *
436 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
437 loff_t size, const struct kernfs_ops *ops, void *priv)
438 {
439 return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
440 }
441
442 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
443 const char *name)
444 {
445 return kernfs_remove_by_name_ns(parent, name, NULL);
446 }
447
448 static inline int kernfs_rename(struct kernfs_node *kn,
449 struct kernfs_node *new_parent,
450 const char *new_name)
451 {
452 return kernfs_rename_ns(kn, new_parent, new_name, NULL);
453 }
454
455 static inline struct dentry *
456 kernfs_mount(struct file_system_type *fs_type, int flags,
457 struct kernfs_root *root, unsigned long magic,
458 bool *new_sb_created)
459 {
460 return kernfs_mount_ns(fs_type, flags, root,
461 magic, new_sb_created, NULL);
462 }
463
464 #endif /* __LINUX_KERNFS_H */