cregit-Linux how code gets into the kernel

Release 4.12 include/linux/kernfs.h

Directory: include/linux
/*
 * kernfs.h - pseudo filesystem decoupled from vfs locking
 *
 * This file is released under the GPLv2.
 */

#ifndef __LINUX_KERNFS_H

#define __LINUX_KERNFS_H

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/lockdep.h>
#include <linux/rbtree.h>
#include <linux/atomic.h>
#include <linux/wait.h>

struct file;
struct dentry;
struct iattr;
struct seq_file;
struct vm_area_struct;
struct super_block;
struct file_system_type;

struct kernfs_open_node;
struct kernfs_iattrs;


enum kernfs_node_type {
	
KERNFS_DIR		= 0x0001,
	
KERNFS_FILE		= 0x0002,
	
KERNFS_LINK		= 0x0004,
};


#define KERNFS_TYPE_MASK	0x000f

#define KERNFS_FLAG_MASK	~KERNFS_TYPE_MASK


enum kernfs_node_flag {
	
KERNFS_ACTIVATED	= 0x0010,
	
KERNFS_NS		= 0x0020,
	
KERNFS_HAS_SEQ_SHOW	= 0x0040,
	
KERNFS_HAS_MMAP		= 0x0080,
	
KERNFS_LOCKDEP		= 0x0100,
	
KERNFS_SUICIDAL		= 0x0400,
	
KERNFS_SUICIDED		= 0x0800,
	
KERNFS_EMPTY_DIR	= 0x1000,
	
KERNFS_HAS_RELEASE	= 0x2000,
};

/* @flags for kernfs_create_root() */

enum kernfs_root_flag {
	/*
         * kernfs_nodes are created in the deactivated state and invisible.
         * They require explicit kernfs_activate() to become visible.  This
         * can be used to make related nodes become visible atomically
         * after all nodes are created successfully.
         */
	
KERNFS_ROOT_CREATE_DEACTIVATED		= 0x0001,

	/*
         * For regular flies, if the opener has CAP_DAC_OVERRIDE, open(2)
         * succeeds regardless of the RW permissions.  sysfs had an extra
         * layer of enforcement where open(2) fails with -EACCES regardless
         * of CAP_DAC_OVERRIDE if the permission doesn't have the
         * respective read or write access at all (none of S_IRUGO or
         * S_IWUGO) or the respective operation isn't implemented.  The
         * following flag enables that behavior.
         */
	
KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK	= 0x0002,
};

/* type-specific structures for kernfs_node union members */

struct kernfs_elem_dir {
	
unsigned long		subdirs;
	/* children rbtree starts here and goes through kn->rb */
	
struct rb_root		children;

	/*
         * The kernfs hierarchy this directory belongs to.  This fits
         * better directly in kernfs_node but is here to save space.
         */
	
struct kernfs_root	*root;
};


struct kernfs_elem_symlink {
	
struct kernfs_node	*target_kn;
};


struct kernfs_elem_attr {
	
const struct kernfs_ops	*ops;
	
struct kernfs_open_node	*open;
	
loff_t			size;
	
struct kernfs_node	*notify_next;	/* for kernfs_notify() */
};

/*
 * kernfs_node - the building block of kernfs hierarchy.  Each and every
 * kernfs node is represented by single kernfs_node.  Most fields are
 * private to kernfs and shouldn't be accessed directly by kernfs users.
 *
 * As long as s_count reference is held, the kernfs_node itself is
 * accessible.  Dereferencing elem or any other outer entity requires
 * active reference.
 */

struct kernfs_node {
	
atomic_t		count;
	
atomic_t		active;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	
struct lockdep_map	dep_map;
#endif
	/*
         * Use kernfs_get_parent() and kernfs_name/path() instead of
         * accessing the following two fields directly.  If the node is
         * never moved to a different parent, it is safe to access the
         * parent directly.
         */
	
struct kernfs_node	*parent;
	
const char		*name;

	
struct rb_node		rb;

	
const void		*ns;	/* namespace tag */
	
unsigned int		hash;	/* ns + name hash */
	union {
		
struct kernfs_elem_dir		dir;
		
struct kernfs_elem_symlink	symlink;
		
struct kernfs_elem_attr		attr;
	};

	
void			*priv;

	
unsigned short		flags;
	
umode_t			mode;
	
unsigned int		ino;
	
struct kernfs_iattrs	*iattr;
};

/*
 * kernfs_syscall_ops may be specified on kernfs_create_root() to support
 * syscalls.  These optional callbacks are invoked on the matching syscalls
 * and can perform any kernfs operations which don't necessarily have to be
 * the exact operation requested.  An active reference is held for each
 * kernfs_node parameter.
 */

struct kernfs_syscall_ops {
	
int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
	
int (*show_options)(struct seq_file *sf, struct kernfs_root *root);

	
int (*mkdir)(struct kernfs_node *parent, const char *name,
		     umode_t mode);
	
int (*rmdir)(struct kernfs_node *kn);
	
int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
		      const char *new_name);
	
int (*show_path)(struct seq_file *sf, struct kernfs_node *kn,
			 struct kernfs_root *root);
};


struct kernfs_root {
	/* published fields */
	
struct kernfs_node	*kn;
	
unsigned int		flags;	/* KERNFS_ROOT_* flags */

	/* private fields, do not use outside kernfs proper */
	
struct ida		ino_ida;
	
struct kernfs_syscall_ops *syscall_ops;

	/* list of kernfs_super_info of this root, protected by kernfs_mutex */
	
struct list_head	supers;

	
wait_queue_head_t	deactivate_waitq;
};


struct kernfs_open_file {
	/* published fields */
	
struct kernfs_node	*kn;
	
struct file		*file;
	
struct seq_file		*seq_file;
	
void			*priv;

	/* private fields, do not use outside kernfs proper */
	
struct mutex		mutex;
	
struct mutex		prealloc_mutex;
	
int			event;
	
struct list_head	list;
	
char			*prealloc_buf;

	
size_t			atomic_write_len;
	
bool			mmapped:1;
	
bool			released:1;
	
const struct vm_operations_struct *vm_ops;
};


struct kernfs_ops {
	/*
         * Optional open/release methods.  Both are called with
         * @of->seq_file populated.
         */
	
int (*open)(struct kernfs_open_file *of);
	
void (*release)(struct kernfs_open_file *of);

	/*
         * Read is handled by either seq_file or raw_read().
         *
         * If seq_show() is present, seq_file path is active.  Other seq
         * operations are optional and if not implemented, the behavior is
         * equivalent to single_open().  @sf->private points to the
         * associated kernfs_open_file.
         *
         * read() is bounced through kernel buffer and a read larger than
         * PAGE_SIZE results in partial operation of PAGE_SIZE.
         */
	
int (*seq_show)(struct seq_file *sf, void *v);

	
void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
	
void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
	
void (*seq_stop)(struct seq_file *sf, void *v);

	
ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
			loff_t off);

	/*
         * write() is bounced through kernel buffer.  If atomic_write_len
         * is not set, a write larger than PAGE_SIZE results in partial
         * operations of PAGE_SIZE chunks.  If atomic_write_len is set,
         * writes upto the specified size are executed atomically but
         * larger ones are rejected with -E2BIG.
         */
	
size_t atomic_write_len;
	/*
         * "prealloc" causes a buffer to be allocated at open for
         * all read/write requests.  As ->seq_show uses seq_read()
         * which does its own allocation, it is incompatible with
         * ->prealloc.  Provide ->read and ->write with ->prealloc.
         */
	
bool prealloc;
	
ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
			 loff_t off);

	
int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);

#ifdef CONFIG_DEBUG_LOCK_ALLOC
	
struct lock_class_key	lockdep_key;
#endif
};

#ifdef CONFIG_KERNFS


static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn) { return kn->flags & KERNFS_TYPE_MASK; }

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/** * kernfs_enable_ns - enable namespace under a directory * @kn: directory of interest, should be empty * * This is to be called right after @kn is created to enable namespace * under it. All children of @kn must have non-NULL namespace tags and * only the ones which match the super_block's tag will be visible. */
static inline void kernfs_enable_ns(struct kernfs_node *kn) { WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR); WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children)); kn->flags |= KERNFS_NS; }

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/** * kernfs_ns_enabled - test whether namespace is enabled * @kn: the node to test * * Test whether namespace filtering is enabled for the children of @ns. */
static inline bool kernfs_ns_enabled(struct kernfs_node *kn) { return kn->flags & KERNFS_NS; }

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int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen); int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn, char *buf, size_t buflen); void pr_cont_kernfs_name(struct kernfs_node *kn); void pr_cont_kernfs_path(struct kernfs_node *kn); struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn); struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name, const void *ns); struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path, const void *ns); void kernfs_get(struct kernfs_node *kn); void kernfs_put(struct kernfs_node *kn); struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry); struct kernfs_root *kernfs_root_from_sb(struct super_block *sb); struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn); struct dentry *kernfs_node_dentry(struct kernfs_node *kn, struct super_block *sb); struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags, void *priv); void kernfs_destroy_root(struct kernfs_root *root); struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent, const char *name, umode_t mode, void *priv, const void *ns); struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent, const char *name); struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode, loff_t size, const struct kernfs_ops *ops, void *priv, const void *ns, struct lock_class_key *key); struct kernfs_node *kernfs_create_link(struct kernfs_node *parent, const char *name, struct kernfs_node *target); void kernfs_activate(struct kernfs_node *kn); void kernfs_remove(struct kernfs_node *kn); void kernfs_break_active_protection(struct kernfs_node *kn); void kernfs_unbreak_active_protection(struct kernfs_node *kn); bool kernfs_remove_self(struct kernfs_node *kn); int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name, const void *ns); int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent, const char *new_name, const void *new_ns); int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr); void kernfs_notify(struct kernfs_node *kn); const void *kernfs_super_ns(struct super_block *sb); struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, struct kernfs_root *root, unsigned long magic, bool *new_sb_created, const void *ns); void kernfs_kill_sb(struct super_block *sb); struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns); void kernfs_init(void); #else /* CONFIG_KERNFS */
static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn) { return 0; }

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/* whatever */
static inline void kernfs_enable_ns(struct kernfs_node *kn) { }

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static inline bool kernfs_ns_enabled(struct kernfs_node *kn) { return false; }

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static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen) { return -ENOSYS; }

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static inline int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn, char *buf, size_t buflen) { return -ENOSYS; }

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static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }

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static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }

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static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn) { return NULL; }

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static inline struct kernfs_node * kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name, const void *ns) { return NULL; }

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static inline struct kernfs_node * kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path, const void *ns) { return NULL; }

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static inline void kernfs_get(struct kernfs_node *kn) { }

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static inline void kernfs_put(struct kernfs_node *kn) { }

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static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry) { return NULL; }

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static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) { return NULL; }

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static inline struct inode * kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn) { return NULL; }

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static inline struct kernfs_root * kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags, void *priv) { return ERR_PTR(-ENOSYS); }

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static inline void kernfs_destroy_root(struct kernfs_root *root) { }

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static inline struct kernfs_node * kernfs_create_dir_ns(struct kernfs_node *parent, const char *name, umode_t mode, void *priv, const void *ns) { return ERR_PTR(-ENOSYS); }

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static inline struct kernfs_node * __kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode, loff_t size, const struct kernfs_ops *ops, void *priv, const void *ns, struct lock_class_key *key) { return ERR_PTR(-ENOSYS); }

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static inline struct kernfs_node * kernfs_create_link(struct kernfs_node *parent, const char *name, struct kernfs_node *target) { return ERR_PTR(-ENOSYS); }

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static inline void kernfs_activate(struct kernfs_node *kn) { }

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static inline void kernfs_remove(struct kernfs_node *kn) { }

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static inline bool kernfs_remove_self(struct kernfs_node *kn) { return false; }

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static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn, const char *name, const void *ns) { return -ENOSYS; }

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static inline int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent, const char *new_name, const void *new_ns) { return -ENOSYS; }

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static inline int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) { return -ENOSYS; }

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static inline void kernfs_notify(struct kernfs_node *kn) { }

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static inline const void *kernfs_super_ns(struct super_block *sb) { return NULL; }

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static inline struct dentry * kernfs_mount_ns(struct file_system_type *fs_type, int flags, struct kernfs_root *root, unsigned long magic, bool *new_sb_created, const void *ns) { return ERR_PTR(-ENOSYS); }

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static inline void kernfs_kill_sb(struct super_block *sb) { }

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static inline void kernfs_init(void) { }

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#endif /* CONFIG_KERNFS */ /** * kernfs_path - build full path of a given node * @kn: kernfs_node of interest * @buf: buffer to copy @kn's name into * @buflen: size of @buf * * Builds and returns the full path of @kn in @buf of @buflen bytes. The * path is built from the end of @buf so the returned pointer usually * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated * and %NULL is returned. */
static inline int kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen) { return kernfs_path_from_node(kn, NULL, buf, buflen); }

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static inline struct kernfs_node * kernfs_find_and_get(struct kernfs_node *kn, const char *name) { return kernfs_find_and_get_ns(kn, name, NULL); }

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static inline struct kernfs_node * kernfs_walk_and_get(struct kernfs_node *kn, const char *path) { return kernfs_walk_and_get_ns(kn, path, NULL); }

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static inline struct kernfs_node * kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode, void *priv) { return kernfs_create_dir_ns(parent, name, mode, priv, NULL); }

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static inline struct kernfs_node * kernfs_create_file_ns(struct kernfs_node *parent, const char *name, umode_t mode, loff_t size, const struct kernfs_ops *ops, void *priv, const void *ns) { struct lock_class_key *key = NULL; #ifdef CONFIG_DEBUG_LOCK_ALLOC key = (struct lock_class_key *)&ops->lockdep_key; #endif return __kernfs_create_file(parent, name, mode, size, ops, priv, ns, key); }

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static inline struct kernfs_node * kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode, loff_t size, const struct kernfs_ops *ops, void *priv) { return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL); }

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static inline int kernfs_remove_by_name(struct kernfs_node *parent, const char *name) { return kernfs_remove_by_name_ns(parent, name, NULL); }

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static inline int kernfs_rename(struct kernfs_node *kn, struct kernfs_node *new_parent, const char *new_name) { return kernfs_rename_ns(kn, new_parent, new_name, NULL); }

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static inline struct dentry * kernfs_mount(struct file_system_type *fs_type, int flags, struct kernfs_root *root, unsigned long magic, bool *new_sb_created) { return kernfs_mount_ns(fs_type, flags, root, magic, new_sb_created, NULL); }

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#endif /* __LINUX_KERNFS_H */

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