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_SUICIDAL         = 0x0400,
  47         KERNFS_SUICIDED         = 0x0800,
  48 };
  49
  50 /* @flags for kernfs_create_root() */
  51 enum kernfs_root_flag {
  52         /*
  53          * kernfs_nodes are created in the deactivated state and invisible.
  54          * They require explicit kernfs_activate() to become visible.  This
  55          * can be used to make related nodes become visible atomically
  56          * after all nodes are created successfully.
  57          */
  58         KERNFS_ROOT_CREATE_DEACTIVATED          = 0x0001,
  59
  60         /*
  61          * For regular flies, if the opener has CAP_DAC_OVERRIDE, open(2)
  62          * succeeds regardless of the RW permissions.  sysfs had an extra
  63          * layer of enforcement where open(2) fails with -EACCES regardless
  64          * of CAP_DAC_OVERRIDE if the permission doesn't have the
  65          * respective read or write access at all (none of S_IRUGO or
  66          * S_IWUGO) or the respective operation isn't implemented.  The
  67          * following flag enables that behavior.
  68          */
  69         KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK       = 0x0002,
  70 };
  71
  72 /* type-specific structures for kernfs_node union members */
  73 struct kernfs_elem_dir {
  74         unsigned long           subdirs;
  75         /* children rbtree starts here and goes through kn->rb */
  76         struct rb_root          children;
  77
  78         /*
  79          * The kernfs hierarchy this directory belongs to.  This fits
  80          * better directly in kernfs_node but is here to save space.
  81          */
  82         struct kernfs_root      *root;
  83 };
  84
  85 struct kernfs_elem_symlink {
  86         struct kernfs_node      *target_kn;
  87 };
  88
  89 struct kernfs_elem_attr {
  90         const struct kernfs_ops *ops;
  91         struct kernfs_open_node *open;
  92         loff_t                  size;
  93         struct kernfs_node      *notify_next;   /* for kernfs_notify() */
  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         char                    *prealloc_buf;
 182
 183         size_t                  atomic_write_len;
 184         bool                    mmapped;
 185         const struct vm_operations_struct *vm_ops;
 186 };
 187
 188 struct kernfs_ops {
 189         /*
 190          * Read is handled by either seq_file or raw_read().
 191          *
 192          * If seq_show() is present, seq_file path is active.  Other seq
 193          * operations are optional and if not implemented, the behavior is
 194          * equivalent to single_open().  @sf->private points to the
 195          * associated kernfs_open_file.
 196          *
 197          * read() is bounced through kernel buffer and a read larger than
 198          * PAGE_SIZE results in partial operation of PAGE_SIZE.
 199          */
 200         int (*seq_show)(struct seq_file *sf, void *v);
 201
 202         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 203         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 204         void (*seq_stop)(struct seq_file *sf, void *v);
 205
 206         ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
 207                         loff_t off);
 208
 209         /*
 210          * write() is bounced through kernel buffer.  If atomic_write_len
 211          * is not set, a write larger than PAGE_SIZE results in partial
 212          * operations of PAGE_SIZE chunks.  If atomic_write_len is set,
 213          * writes upto the specified size are executed atomically but
 214          * larger ones are rejected with -E2BIG.
 215          */
 216         size_t atomic_write_len;
 217         /*
 218          * "prealloc" causes a buffer to be allocated at open for
 219          * all read/write requests.  As ->seq_show uses seq_read()
 220          * which does its own allocation, it is incompatible with
 221          * ->prealloc.  Provide ->read and ->write with ->prealloc.
 222          */
 223         bool prealloc;
 224         ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
 225                          loff_t off);
 226
 227         int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
 228
 229 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 230         struct lock_class_key   lockdep_key;
 231 #endif
 232 };
 233
 234 #ifdef CONFIG_KERNFS
 235
 236 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 237 {
 238         return kn->flags & KERNFS_TYPE_MASK;
 239 }
 240
 241 /**
 242  * kernfs_enable_ns - enable namespace under a directory
 243  * @kn: directory of interest, should be empty
 244  *
 245  * This is to be called right after @kn is created to enable namespace
 246  * under it.  All children of @kn must have non-NULL namespace tags and
 247  * only the ones which match the super_block's tag will be visible.
 248  */
 249 static inline void kernfs_enable_ns(struct kernfs_node *kn)
 250 {
 251         WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
 252         WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
 253         kn->flags |= KERNFS_NS;
 254 }
 255
 256 /**
 257  * kernfs_ns_enabled - test whether namespace is enabled
 258  * @kn: the node to test
 259  *
 260  * Test whether namespace filtering is enabled for the children of @ns.
 261  */
 262 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 263 {
 264         return kn->flags & KERNFS_NS;
 265 }
 266
 267 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
 268 char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 269                                 size_t buflen);
 270 void pr_cont_kernfs_name(struct kernfs_node *kn);
 271 void pr_cont_kernfs_path(struct kernfs_node *kn);
 272 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
 273 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
 274                                            const char *name, const void *ns);
 275 void kernfs_get(struct kernfs_node *kn);
 276 void kernfs_put(struct kernfs_node *kn);
 277
 278 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
 279 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
 280
 281 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
 282                                        unsigned int flags, void *priv);
 283 void kernfs_destroy_root(struct kernfs_root *root);
 284
 285 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 286                                          const char *name, umode_t mode,
 287                                          void *priv, const void *ns);
 288 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 289                                          const char *name,
 290                                          umode_t mode, loff_t size,
 291                                          const struct kernfs_ops *ops,
 292                                          void *priv, const void *ns,
 293                                          struct lock_class_key *key);
 294 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
 295                                        const char *name,
 296                                        struct kernfs_node *target);
 297 void kernfs_activate(struct kernfs_node *kn);
 298 void kernfs_remove(struct kernfs_node *kn);
 299 void kernfs_break_active_protection(struct kernfs_node *kn);
 300 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
 301 bool kernfs_remove_self(struct kernfs_node *kn);
 302 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
 303                              const void *ns);
 304 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 305                      const char *new_name, const void *new_ns);
 306 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 307 void kernfs_notify(struct kernfs_node *kn);
 308
 309 const void *kernfs_super_ns(struct super_block *sb);
 310 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 311                                struct kernfs_root *root, unsigned long magic,
 312                                bool *new_sb_created, const void *ns);
 313 void kernfs_kill_sb(struct super_block *sb);
 314 struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);
 315
 316 void kernfs_init(void);
 317
 318 #else   /* CONFIG_KERNFS */
 319
 320 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 321 { return 0; }   /* whatever */
 322
 323 static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
 324
 325 static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 326 { return false; }
 327
 328 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
 329 { return -ENOSYS; }
 330
 331 static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 332                                               size_t buflen)
 333 { return NULL; }
 334
 335 static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
 336 static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
 337
 338 static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
 339 { return NULL; }
 340
 341 static inline struct kernfs_node *
 342 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
 343                        const void *ns)
 344 { return NULL; }
 345
 346 static inline void kernfs_get(struct kernfs_node *kn) { }
 347 static inline void kernfs_put(struct kernfs_node *kn) { }
 348
 349 static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
 350 { return NULL; }
 351
 352 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
 353 { return NULL; }
 354
 355 static inline struct kernfs_root *
 356 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
 357                    void *priv)
 358 { return ERR_PTR(-ENOSYS); }
 359
 360 static inline void kernfs_destroy_root(struct kernfs_root *root) { }
 361
 362 static inline struct kernfs_node *
 363 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 364                      umode_t mode, void *priv, const void *ns)
 365 { return ERR_PTR(-ENOSYS); }
 366
 367 static inline struct kernfs_node *
 368 __kernfs_create_file(struct kernfs_node *parent, const char *name,
 369                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
 370                      void *priv, const void *ns, struct lock_class_key *key)
 371 { return ERR_PTR(-ENOSYS); }
 372
 373 static inline struct kernfs_node *
 374 kernfs_create_link(struct kernfs_node *parent, const char *name,
 375                    struct kernfs_node *target)
 376 { return ERR_PTR(-ENOSYS); }
 377
 378 static inline void kernfs_activate(struct kernfs_node *kn) { }
 379
 380 static inline void kernfs_remove(struct kernfs_node *kn) { }
 381
 382 static inline bool kernfs_remove_self(struct kernfs_node *kn)
 383 { return false; }
 384
 385 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
 386                                            const char *name, const void *ns)
 387 { return -ENOSYS; }
 388
 389 static inline int kernfs_rename_ns(struct kernfs_node *kn,
 390                                    struct kernfs_node *new_parent,
 391                                    const char *new_name, const void *new_ns)
 392 { return -ENOSYS; }
 393
 394 static inline int kernfs_setattr(struct kernfs_node *kn,
 395                                  const struct iattr *iattr)
 396 { return -ENOSYS; }
 397
 398 static inline void kernfs_notify(struct kernfs_node *kn) { }
 399
 400 static inline const void *kernfs_super_ns(struct super_block *sb)
 401 { return NULL; }
 402
 403 static inline struct dentry *
 404 kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 405                 struct kernfs_root *root, unsigned long magic,
 406                 bool *new_sb_created, const void *ns)
 407 { return ERR_PTR(-ENOSYS); }
 408
 409 static inline void kernfs_kill_sb(struct super_block *sb) { }
 410
 411 static inline void kernfs_init(void) { }
 412
 413 #endif  /* CONFIG_KERNFS */
 414
 415 static inline struct kernfs_node *
 416 kernfs_find_and_get(struct kernfs_node *kn, const char *name)
 417 {
 418         return kernfs_find_and_get_ns(kn, name, NULL);
 419 }
 420
 421 static inline struct kernfs_node *
 422 kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
 423                   void *priv)
 424 {
 425         return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
 426 }
 427
 428 static inline struct kernfs_node *
 429 kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
 430                       umode_t mode, loff_t size, const struct kernfs_ops *ops,
 431                       void *priv, const void *ns)
 432 {
 433         struct lock_class_key *key = NULL;
 434
 435 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 436         key = (struct lock_class_key *)&ops->lockdep_key;
 437 #endif
 438         return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
 439                                     key);
 440 }
 441
 442 static inline struct kernfs_node *
 443 kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
 444                    loff_t size, const struct kernfs_ops *ops, void *priv)
 445 {
 446         return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
 447 }
 448
 449 static inline int kernfs_remove_by_name(struct kernfs_node *parent,
 450                                         const char *name)
 451 {
 452         return kernfs_remove_by_name_ns(parent, name, NULL);
 453 }
 454
 455 static inline int kernfs_rename(struct kernfs_node *kn,
 456                                 struct kernfs_node *new_parent,
 457                                 const char *new_name)
 458 {
 459         return kernfs_rename_ns(kn, new_parent, new_name, NULL);
 460 }
 461
 462 static inline struct dentry *
 463 kernfs_mount(struct file_system_type *fs_type, int flags,
 464                 struct kernfs_root *root, unsigned long magic,
 465                 bool *new_sb_created)
 466 {
 467         return kernfs_mount_ns(fs_type, flags, root,
 468                                 magic, new_sb_created, NULL);
 469 }
 470
 471 #endif  /* __LINUX_KERNFS_H */