include/linux/kernfs.h

   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         wait_queue_head_t       deactivate_waitq;
 165 };
 166
 167 struct kernfs_open_file {
 168         /* published fields */
 169         struct kernfs_node      *kn;
 170         struct file             *file;
 171         void                    *priv;
 172
 173         /* private fields, do not use outside kernfs proper */
 174         struct mutex            mutex;
 175         int                     event;
 176         struct list_head        list;
 177
 178         size_t                  atomic_write_len;
 179         bool                    mmapped;
 180         const struct vm_operations_struct *vm_ops;
 181 };
 182
 183 struct kernfs_ops {
 184         /*
 185          * Read is handled by either seq_file or raw_read().
 186          *
 187          * If seq_show() is present, seq_file path is active.  Other seq
 188          * operations are optional and if not implemented, the behavior is
 189          * equivalent to single_open().  @sf->private points to the
 190          * associated kernfs_open_file.
 191          *
 192          * read() is bounced through kernel buffer and a read larger than
 193          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 194          */
 195         int (*seq_show)(struct seq_file *sf, void *v);
 196
 197         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 198         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 199         void (*seq_stop)(struct seq_file *sf, void *v);
 200
 201         ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
 202                         loff_t off);
 203
 204         /*
 205          * write() is bounced through kernel buffer.  If atomic_write_len
 206          * is not set, a write larger than PAGE_SIZE results in partial
 207          * operations of PAGE_SIZE chunks.  If atomic_write_len is set,
 208          * writes upto the specified size are executed atomically but
 209          * larger ones are rejected with -E2BIG.
 210          */
 211         size_t atomic_write_len;
 212         ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
 213                          loff_t off);
 214
 215         int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
 216
 217 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 218         struct lock_class_key   lockdep_key;
 219 #endif
 220 };
 221
 222 #ifdef CONFIG_KERNFS
 223
 224 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 225 {
 226         return kn->flags & KERNFS_TYPE_MASK;
 227 }
 228
 229 /**
 230  * kernfs_enable_ns - enable namespace under a directory
 231  * @kn: directory of interest, should be empty
 232  *
 233  * This is to be called right after @kn is created to enable namespace
 234  * under it.  All children of @kn must have non-NULL namespace tags and
 235  * only the ones which match the super_block's tag will be visible.
 236  */
 237 static inline void kernfs_enable_ns(struct kernfs_node *kn)
 238 {
 239         WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 240         WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
 241         kn->flags |= KERNFS_NS;
 242 }
 243
 244 /**
 245  * kernfs_ns_enabled - test whether namespace is enabled
 246  * @kn: the node to test
 247  *
 248  * Test whether namespace filtering is enabled for the children of @ns.
 249  */
 250 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 251 {
 252         return kn->flags & KERNFS_NS;
 253 }
 254
 255 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
 256 char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 257                                 size_t buflen);
 258 void pr_cont_kernfs_name(struct kernfs_node *kn);
 259 void pr_cont_kernfs_path(struct kernfs_node *kn);
 260 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
 261 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
 262                                            const char *name, const void *ns);
 263 void kernfs_get(struct kernfs_node *kn);
 264 void kernfs_put(struct kernfs_node *kn);
 265
 266 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
 267 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
 268
 269 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
 270                                        unsigned int flags, void *priv);
 271 void kernfs_destroy_root(struct kernfs_root *root);
 272
 273 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 274                                          const char *name, umode_t mode,
 275                                          void *priv, const void *ns);
 276 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 277                                          const char *name,
 278                                          umode_t mode, loff_t size,
 279                                          const struct kernfs_ops *ops,
 280                                          void *priv, const void *ns,
 281                                          bool name_is_static,
 282                                          struct lock_class_key *key);
 283 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
 284                                        const char *name,
 285                                        struct kernfs_node *target);
 286 void kernfs_activate(struct kernfs_node *kn);
 287 void kernfs_remove(struct kernfs_node *kn);
 288 void kernfs_break_active_protection(struct kernfs_node *kn);
 289 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
 290 bool kernfs_remove_self(struct kernfs_node *kn);
 291 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
 292                              const void *ns);
 293 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 294                      const char *new_name, const void *new_ns);
 295 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 296 void kernfs_notify(struct kernfs_node *kn);
 297
 298 const void *kernfs_super_ns(struct super_block *sb);
 299 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 300                                struct kernfs_root *root, bool *new_sb_created,
 301                                const void *ns);
 302 void kernfs_kill_sb(struct super_block *sb);
 303
 304 void kernfs_init(void);
 305
 306 #else   /* CONFIG_KERNFS */
 307
 308 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 309 { return 0; }   /* whatever */
 310
 311 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
 312
 313 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 314 { return false; }
 315
 316 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
 317 { return -ENOSYS; }
 318
 319 static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 320                                               size_t buflen)
 321 { return NULL; }
 322
 323 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
 324 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
 325
 326 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
 327 { return NULL; }
 328
 329 static inline struct kernfs_node *
 330 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
 331                        const void *ns)
 332 { return NULL; }
 333
 334 static inline void kernfs_get(struct kernfs_node *kn) { }
 335 static inline void kernfs_put(struct kernfs_node *kn) { }
 336
 337 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
 338 { return NULL; }
 339
 340 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
 341 { return NULL; }
 342
 343 static inline struct kernfs_root *
 344 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
 345                    void *priv)
 346 { return ERR_PTR(-ENOSYS); }
 347
 348 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
 349
 350 static inline struct kernfs_node *
 351 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 352                      umode_t mode, void *priv, const void *ns)
 353 { return ERR_PTR(-ENOSYS); }
 354
 355 static inline struct kernfs_node *
 356 __kernfs_create_file(struct kernfs_node *parent, const char *name,
 357                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
 358                      void *priv, const void *ns, bool name_is_static,
 359                      struct lock_class_key *key)
 360 { return ERR_PTR(-ENOSYS); }
 361
 362 static inline struct kernfs_node *
 363 kernfs_create_link(struct kernfs_node *parent, const char *name,
 364                    struct kernfs_node *target)
 365 { return ERR_PTR(-ENOSYS); }
 366
 367 static inline void kernfs_activate(struct kernfs_node *kn) { }
 368
 369 static inline void kernfs_remove(struct kernfs_node *kn) { }
 370
 371 static inline bool kernfs_remove_self(struct kernfs_node *kn)
 372 { return false; }
 373
 374 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
 375                                            const char *name, const void *ns)
 376 { return -ENOSYS; }
 377
 378 static inline int kernfs_rename_ns(struct kernfs_node *kn,
 379                                    struct kernfs_node *new_parent,
 380                                    const char *new_name, const void *new_ns)
 381 { return -ENOSYS; }
 382
 383 static inline int kernfs_setattr(struct kernfs_node *kn,
 384                                  const struct iattr *iattr)
 385 { return -ENOSYS; }
 386
 387 static inline void kernfs_notify(struct kernfs_node *kn) { }
 388
 389 static inline const void *kernfs_super_ns(struct super_block *sb)
 390 { return NULL; }
 391
 392 static inline struct dentry *
 393 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 394                 struct kernfs_root *root, bool *new_sb_created, const void *ns)
 395 { return ERR_PTR(-ENOSYS); }
 396
 397 static inline void kernfs_kill_sb(struct super_block *sb) { }
 398
 399 static inline void kernfs_init(void) { }
 400
 401 #endif  /* CONFIG_KERNFS */
 402
 403 static inline struct kernfs_node *
 404 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
 405 {
 406         return kernfs_find_and_get_ns(kn, name, NULL);
 407 }
 408
 409 static inline struct kernfs_node *
 410 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
 411                   void *priv)
 412 {
 413         return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
 414 }
 415
 416 static inline struct kernfs_node *
 417 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
 418                       umode_t mode, loff_t size, const struct kernfs_ops *ops,
 419                       void *priv, const void *ns)
 420 {
 421         struct lock_class_key *key = NULL;
 422
 423 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 424         key = (struct lock_class_key *)&ops->lockdep_key;
 425 #endif
 426         return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
 427                                     false, key);
 428 }
 429
 430 static inline struct kernfs_node *
 431 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
 432                    loff_t size, const struct kernfs_ops *ops, void *priv)
 433 {
 434         return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
 435 }
 436
 437 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
 438                                         const char *name)
 439 {
 440         return kernfs_remove_by_name_ns(parent, name, NULL);
 441 }
 442
 443 static inline int kernfs_rename(struct kernfs_node *kn,
 444                                 struct kernfs_node *new_parent,
 445                                 const char *new_name)
 446 {
 447         return kernfs_rename_ns(kn, new_parent, new_name, NULL);
 448 }
 449
 450 static inline struct dentry *
 451 kernfs_mount(struct file_system_type *fs_type, int flags,
 452              struct kernfs_root *root, bool *new_sb_created)
 453 {
 454         return kernfs_mount_ns(fs_type, flags, root, new_sb_created, NULL);
 455 }
 456
 457 #endif  /* __LINUX_KERNFS_H */