xref: /openbmc/linux/include/linux/kernfs.h (revision b34e08d5)
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 	KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
54 };
55 
56 /* type-specific structures for kernfs_node union members */
57 struct kernfs_elem_dir {
58 	unsigned long		subdirs;
59 	/* children rbtree starts here and goes through kn->rb */
60 	struct rb_root		children;
61 
62 	/*
63 	 * The kernfs hierarchy this directory belongs to.  This fits
64 	 * better directly in kernfs_node but is here to save space.
65 	 */
66 	struct kernfs_root	*root;
67 };
68 
69 struct kernfs_elem_symlink {
70 	struct kernfs_node	*target_kn;
71 };
72 
73 struct kernfs_elem_attr {
74 	const struct kernfs_ops	*ops;
75 	struct kernfs_open_node	*open;
76 	loff_t			size;
77 };
78 
79 /*
80  * kernfs_node - the building block of kernfs hierarchy.  Each and every
81  * kernfs node is represented by single kernfs_node.  Most fields are
82  * private to kernfs and shouldn't be accessed directly by kernfs users.
83  *
84  * As long as s_count reference is held, the kernfs_node itself is
85  * accessible.  Dereferencing elem or any other outer entity requires
86  * active reference.
87  */
88 struct kernfs_node {
89 	atomic_t		count;
90 	atomic_t		active;
91 #ifdef CONFIG_DEBUG_LOCK_ALLOC
92 	struct lockdep_map	dep_map;
93 #endif
94 	/*
95 	 * Use kernfs_get_parent() and kernfs_name/path() instead of
96 	 * accessing the following two fields directly.  If the node is
97 	 * never moved to a different parent, it is safe to access the
98 	 * parent directly.
99 	 */
100 	struct kernfs_node	*parent;
101 	const char		*name;
102 
103 	struct rb_node		rb;
104 
105 	const void		*ns;	/* namespace tag */
106 	unsigned int		hash;	/* ns + name hash */
107 	union {
108 		struct kernfs_elem_dir		dir;
109 		struct kernfs_elem_symlink	symlink;
110 		struct kernfs_elem_attr		attr;
111 	};
112 
113 	void			*priv;
114 
115 	unsigned short		flags;
116 	umode_t			mode;
117 	unsigned int		ino;
118 	struct kernfs_iattrs	*iattr;
119 };
120 
121 /*
122  * kernfs_syscall_ops may be specified on kernfs_create_root() to support
123  * syscalls.  These optional callbacks are invoked on the matching syscalls
124  * and can perform any kernfs operations which don't necessarily have to be
125  * the exact operation requested.  An active reference is held for each
126  * kernfs_node parameter.
127  */
128 struct kernfs_syscall_ops {
129 	int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
130 	int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
131 
132 	int (*mkdir)(struct kernfs_node *parent, const char *name,
133 		     umode_t mode);
134 	int (*rmdir)(struct kernfs_node *kn);
135 	int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
136 		      const char *new_name);
137 };
138 
139 struct kernfs_root {
140 	/* published fields */
141 	struct kernfs_node	*kn;
142 	unsigned int		flags;	/* KERNFS_ROOT_* flags */
143 
144 	/* private fields, do not use outside kernfs proper */
145 	struct ida		ino_ida;
146 	struct kernfs_syscall_ops *syscall_ops;
147 	wait_queue_head_t	deactivate_waitq;
148 };
149 
150 struct kernfs_open_file {
151 	/* published fields */
152 	struct kernfs_node	*kn;
153 	struct file		*file;
154 	void			*priv;
155 
156 	/* private fields, do not use outside kernfs proper */
157 	struct mutex		mutex;
158 	int			event;
159 	struct list_head	list;
160 
161 	size_t			atomic_write_len;
162 	bool			mmapped;
163 	const struct vm_operations_struct *vm_ops;
164 };
165 
166 struct kernfs_ops {
167 	/*
168 	 * Read is handled by either seq_file or raw_read().
169 	 *
170 	 * If seq_show() is present, seq_file path is active.  Other seq
171 	 * operations are optional and if not implemented, the behavior is
172 	 * equivalent to single_open().  @sf->private points to the
173 	 * associated kernfs_open_file.
174 	 *
175 	 * read() is bounced through kernel buffer and a read larger than
176 	 * PAGE_SIZE results in partial operation of PAGE_SIZE.
177 	 */
178 	int (*seq_show)(struct seq_file *sf, void *v);
179 
180 	void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
181 	void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
182 	void (*seq_stop)(struct seq_file *sf, void *v);
183 
184 	ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
185 			loff_t off);
186 
187 	/*
188 	 * write() is bounced through kernel buffer.  If atomic_write_len
189 	 * is not set, a write larger than PAGE_SIZE results in partial
190 	 * operations of PAGE_SIZE chunks.  If atomic_write_len is set,
191 	 * writes upto the specified size are executed atomically but
192 	 * larger ones are rejected with -E2BIG.
193 	 */
194 	size_t atomic_write_len;
195 	ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
196 			 loff_t off);
197 
198 	int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
199 
200 #ifdef CONFIG_DEBUG_LOCK_ALLOC
201 	struct lock_class_key	lockdep_key;
202 #endif
203 };
204 
205 #ifdef CONFIG_KERNFS
206 
207 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
208 {
209 	return kn->flags & KERNFS_TYPE_MASK;
210 }
211 
212 /**
213  * kernfs_enable_ns - enable namespace under a directory
214  * @kn: directory of interest, should be empty
215  *
216  * This is to be called right after @kn is created to enable namespace
217  * under it.  All children of @kn must have non-NULL namespace tags and
218  * only the ones which match the super_block's tag will be visible.
219  */
220 static inline void kernfs_enable_ns(struct kernfs_node *kn)
221 {
222 	WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
223 	WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
224 	kn->flags |= KERNFS_NS;
225 }
226 
227 /**
228  * kernfs_ns_enabled - test whether namespace is enabled
229  * @kn: the node to test
230  *
231  * Test whether namespace filtering is enabled for the children of @ns.
232  */
233 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
234 {
235 	return kn->flags & KERNFS_NS;
236 }
237 
238 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
239 char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
240 				size_t buflen);
241 void pr_cont_kernfs_name(struct kernfs_node *kn);
242 void pr_cont_kernfs_path(struct kernfs_node *kn);
243 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
244 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
245 					   const char *name, const void *ns);
246 void kernfs_get(struct kernfs_node *kn);
247 void kernfs_put(struct kernfs_node *kn);
248 
249 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
250 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
251 
252 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
253 				       unsigned int flags, void *priv);
254 void kernfs_destroy_root(struct kernfs_root *root);
255 
256 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
257 					 const char *name, umode_t mode,
258 					 void *priv, const void *ns);
259 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
260 					 const char *name,
261 					 umode_t mode, loff_t size,
262 					 const struct kernfs_ops *ops,
263 					 void *priv, const void *ns,
264 					 bool name_is_static,
265 					 struct lock_class_key *key);
266 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
267 				       const char *name,
268 				       struct kernfs_node *target);
269 void kernfs_activate(struct kernfs_node *kn);
270 void kernfs_remove(struct kernfs_node *kn);
271 void kernfs_break_active_protection(struct kernfs_node *kn);
272 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
273 bool kernfs_remove_self(struct kernfs_node *kn);
274 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
275 			     const void *ns);
276 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
277 		     const char *new_name, const void *new_ns);
278 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
279 void kernfs_notify(struct kernfs_node *kn);
280 
281 const void *kernfs_super_ns(struct super_block *sb);
282 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
283 			       struct kernfs_root *root, bool *new_sb_created,
284 			       const void *ns);
285 void kernfs_kill_sb(struct super_block *sb);
286 
287 void kernfs_init(void);
288 
289 #else	/* CONFIG_KERNFS */
290 
291 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
292 { return 0; }	/* whatever */
293 
294 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
295 
296 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
297 { return false; }
298 
299 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
300 { return -ENOSYS; }
301 
302 static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
303 					      size_t buflen)
304 { return NULL; }
305 
306 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
307 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
308 
309 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
310 { return NULL; }
311 
312 static inline struct kernfs_node *
313 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
314 		       const void *ns)
315 { return NULL; }
316 
317 static inline void kernfs_get(struct kernfs_node *kn) { }
318 static inline void kernfs_put(struct kernfs_node *kn) { }
319 
320 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
321 { return NULL; }
322 
323 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
324 { return NULL; }
325 
326 static inline struct kernfs_root *
327 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
328 		   void *priv)
329 { return ERR_PTR(-ENOSYS); }
330 
331 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
332 
333 static inline struct kernfs_node *
334 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
335 		     umode_t mode, void *priv, const void *ns)
336 { return ERR_PTR(-ENOSYS); }
337 
338 static inline struct kernfs_node *
339 __kernfs_create_file(struct kernfs_node *parent, const char *name,
340 		     umode_t mode, loff_t size, const struct kernfs_ops *ops,
341 		     void *priv, const void *ns, bool name_is_static,
342 		     struct lock_class_key *key)
343 { return ERR_PTR(-ENOSYS); }
344 
345 static inline struct kernfs_node *
346 kernfs_create_link(struct kernfs_node *parent, const char *name,
347 		   struct kernfs_node *target)
348 { return ERR_PTR(-ENOSYS); }
349 
350 static inline void kernfs_activate(struct kernfs_node *kn) { }
351 
352 static inline void kernfs_remove(struct kernfs_node *kn) { }
353 
354 static inline bool kernfs_remove_self(struct kernfs_node *kn)
355 { return false; }
356 
357 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
358 					   const char *name, const void *ns)
359 { return -ENOSYS; }
360 
361 static inline int kernfs_rename_ns(struct kernfs_node *kn,
362 				   struct kernfs_node *new_parent,
363 				   const char *new_name, const void *new_ns)
364 { return -ENOSYS; }
365 
366 static inline int kernfs_setattr(struct kernfs_node *kn,
367 				 const struct iattr *iattr)
368 { return -ENOSYS; }
369 
370 static inline void kernfs_notify(struct kernfs_node *kn) { }
371 
372 static inline const void *kernfs_super_ns(struct super_block *sb)
373 { return NULL; }
374 
375 static inline struct dentry *
376 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
377 		struct kernfs_root *root, bool *new_sb_created, const void *ns)
378 { return ERR_PTR(-ENOSYS); }
379 
380 static inline void kernfs_kill_sb(struct super_block *sb) { }
381 
382 static inline void kernfs_init(void) { }
383 
384 #endif	/* CONFIG_KERNFS */
385 
386 static inline struct kernfs_node *
387 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
388 {
389 	return kernfs_find_and_get_ns(kn, name, NULL);
390 }
391 
392 static inline struct kernfs_node *
393 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
394 		  void *priv)
395 {
396 	return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
397 }
398 
399 static inline struct kernfs_node *
400 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
401 		      umode_t mode, loff_t size, const struct kernfs_ops *ops,
402 		      void *priv, const void *ns)
403 {
404 	struct lock_class_key *key = NULL;
405 
406 #ifdef CONFIG_DEBUG_LOCK_ALLOC
407 	key = (struct lock_class_key *)&ops->lockdep_key;
408 #endif
409 	return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
410 				    false, key);
411 }
412 
413 static inline struct kernfs_node *
414 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
415 		   loff_t size, const struct kernfs_ops *ops, void *priv)
416 {
417 	return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
418 }
419 
420 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
421 					const char *name)
422 {
423 	return kernfs_remove_by_name_ns(parent, name, NULL);
424 }
425 
426 static inline int kernfs_rename(struct kernfs_node *kn,
427 				struct kernfs_node *new_parent,
428 				const char *new_name)
429 {
430 	return kernfs_rename_ns(kn, new_parent, new_name, NULL);
431 }
432 
433 static inline struct dentry *
434 kernfs_mount(struct file_system_type *fs_type, int flags,
435 	     struct kernfs_root *root, bool *new_sb_created)
436 {
437 	return kernfs_mount_ns(fs_type, flags, root, new_sb_created, NULL);
438 }
439 
440 #endif	/* __LINUX_KERNFS_H */
441