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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* kernfs.h - pseudo filesystem decoupled from vfs locking
*/
#ifndef __LINUX_KERNFS_H
#define __LINUX_KERNFS_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/bug.h>
#include <linux/types.h>
#include <linux/uidgid.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
#include <linux/cache.h>
struct file;
struct dentry;
struct iattr;
struct seq_file;
struct vm_area_struct;
struct vm_operations_struct;
struct super_block;
struct file_system_type;
struct poll_table_struct;
struct fs_context;
struct kernfs_fs_context;
struct kernfs_open_node;
struct kernfs_iattrs;
/*
* NR_KERNFS_LOCK_BITS determines size (NR_KERNFS_LOCKS) of hash
* table of locks.
* Having a small hash table would impact scalability, since
* more and more kernfs_node objects will end up using same lock
* and having a very large hash table would waste memory.
*
* At the moment size of hash table of locks is being set based on
* the number of CPUs as follows:
*
* NR_CPU NR_KERNFS_LOCK_BITS NR_KERNFS_LOCKS
* 1 1 2
* 2-3 2 4
* 4-7 4 16
* 8-15 6 64
* 16-31 8 256
* 32 and more 10 1024
*
* The above relation between NR_CPU and number of locks is based
* on some internal experimentation which involved booting qemu
* with different values of smp, performing some sysfs operations
* on all CPUs and observing how increase in number of locks impacts
* completion time of these sysfs operations on each CPU.
*/
#ifdef CONFIG_SMP
#define NR_KERNFS_LOCK_BITS (2 * (ilog2(NR_CPUS < 32 ? NR_CPUS : 32)))
#else
#define NR_KERNFS_LOCK_BITS 1
#endif
#define NR_KERNFS_LOCKS (1 << NR_KERNFS_LOCK_BITS)
/*
* There's one kernfs_open_file for each open file and one kernfs_open_node
* for each kernfs_node with one or more open files.
*
* filp->private_data points to seq_file whose ->private points to
* kernfs_open_file.
*
* kernfs_open_files are chained at kernfs_open_node->files, which is
* protected by kernfs_global_locks.open_file_mutex[i].
*
* To reduce possible contention in sysfs access, arising due to single
* locks, use an array of locks (e.g. open_file_mutex) and use kernfs_node
* object address as hash keys to get the index of these locks.
*
* Hashed mutexes are safe to use here because operations using these don't
* rely on global exclusion.
*
* In future we intend to replace other global locks with hashed ones as well.
* kernfs_global_locks acts as a holder for all such hash tables.
*/
struct kernfs_global_locks {
struct mutex open_file_mutex[NR_KERNFS_LOCKS];
};
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
#define KERNFS_MAX_USER_XATTRS 128
#define KERNFS_USER_XATTR_SIZE_LIMIT (128 << 10)
enum kernfs_node_flag {
KERNFS_ACTIVATED = 0x0010,
KERNFS_NS = 0x0020,
KERNFS_HAS_SEQ_SHOW = 0x0040,
KERNFS_HAS_MMAP = 0x0080,
KERNFS_LOCKDEP = 0x0100,
KERNFS_HIDDEN = 0x0200,
KERNFS_SUICIDAL = 0x0400,
KERNFS_SUICIDED = 0x0800,
KERNFS_EMPTY_DIR = 0x1000,
KERNFS_HAS_RELEASE = 0x2000,
KERNFS_REMOVING = 0x4000,
};
/* @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 files, 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,
/*
* The filesystem supports exportfs operation, so userspace can use
* fhandle to access nodes of the fs.
*/
KERNFS_ROOT_SUPPORT_EXPORTOP = 0x0004,
/*
* Support user xattrs to be written to nodes rooted at this root.
*/
KERNFS_ROOT_SUPPORT_USER_XATTR = 0x0008,
};
/* 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;
/*
* Monotonic revision counter, used to identify if a directory
* node has changed during negative dentry revalidation.
*/
unsigned long rev;
};
struct kernfs_elem_symlink {
struct kernfs_node *target_kn;
};
struct kernfs_elem_attr {
const struct kernfs_ops *ops;
struct kernfs_open_node __rcu *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 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;
/*
* 64bit unique ID. On 64bit ino setups, id is the ino. On 32bit,
* the low 32bits are ino and upper generation.
*/
u64 id;
unsigned short flags;
umode_t mode;
struct kernfs_iattrs *iattr;
struct rcu_head rcu;
};
/*
* 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 (*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_node *kernfs_root_to_node(struct kernfs_root *root);
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);
__poll_t (*poll)(struct kernfs_open_file *of,
struct poll_table_struct *pt);
int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
loff_t (*llseek)(struct kernfs_open_file *of, loff_t offset, int whence);
};
/*
* The kernfs superblock creation/mount parameter context.
*/
struct kernfs_fs_context {
struct kernfs_root *root; /* Root of the hierarchy being mounted */
void *ns_tag; /* Namespace tag of the mount (or NULL) */
unsigned long magic; /* File system specific magic number */
/* The following are set/used by kernfs_mount() */
bool new_sb_created; /* Set to T if we allocated a new sb */
};
#ifdef CONFIG_KERNFS
static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
{
return kn->flags & KERNFS_TYPE_MASK;
}
static inline ino_t kernfs_id_ino(u64 id)
{
/* id is ino if ino_t is 64bit; otherwise, low 32bits */
if (sizeof(ino_t) >= sizeof(u64))
return id;
else
return (u32)id;
}
static inline u32 kernfs_id_gen(u64 id)
{
/* gen is fixed at 1 if ino_t is 64bit; otherwise, high 32bits */
if (sizeof(ino_t) >= sizeof(u64))
return 1;
else
return id >> 32;
}
static inline ino_t kernfs_ino(struct kernfs_node *kn)
{
return kernfs_id_ino(kn->id);
}
static inline ino_t kernfs_gen(struct kernfs_node *kn)
{
return kernfs_id_gen(kn->id);
}
/**
* 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;
}
/**
* 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;
}
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,
kuid_t uid, kgid_t gid,
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,
kuid_t uid, kgid_t gid,
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_show(struct kernfs_node *kn, bool show);
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);
__poll_t kernfs_generic_poll(struct kernfs_open_file *of,
struct poll_table_struct *pt);
void kernfs_notify(struct kernfs_node *kn);
int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
void *value, size_t size);
int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
const void *value, size_t size, int flags);
const void *kernfs_super_ns(struct super_block *sb);
int kernfs_get_tree(struct fs_context *fc);
void kernfs_free_fs_context(struct fs_context *fc);
void kernfs_kill_sb(struct super_block *sb);
void kernfs_init(void);
struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
u64 id);
#else /* CONFIG_KERNFS */
static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
{ return 0; } /* whatever */
static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
{ return false; }
static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
{ return -ENOSYS; }
static inline int kernfs_path_from_node(struct kernfs_node *root_kn,
struct kernfs_node *kn,
char *buf, size_t buflen)
{ return -ENOSYS; }
static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
{ return NULL; }
static inline struct kernfs_node *
kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{ return NULL; }
static inline struct kernfs_node *
kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
const void *ns)
{ return NULL; }
static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
{ return NULL; }
static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
{ return NULL; }
static inline struct inode *
kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
{ return NULL; }
static inline struct kernfs_root *
kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
void *priv)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_destroy_root(struct kernfs_root *root) { }
static inline struct kernfs_node *
kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
umode_t mode, kuid_t uid, kgid_t gid,
void *priv, const void *ns)
{ return ERR_PTR(-ENOSYS); }
static inline struct kernfs_node *
__kernfs_create_file(struct kernfs_node *parent, const char *name,
umode_t mode, kuid_t uid, kgid_t gid,
loff_t size, const struct kernfs_ops *ops,
void *priv, const void *ns, struct lock_class_key *key)
{ return ERR_PTR(-ENOSYS); }
static inline struct kernfs_node *
kernfs_create_link(struct kernfs_node *parent, const char *name,
struct kernfs_node *target)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_activate(struct kernfs_node *kn) { }
static inline void kernfs_remove(struct kernfs_node *kn) { }
static inline bool kernfs_remove_self(struct kernfs_node *kn)
{ return false; }
static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
const char *name, const void *ns)
{ return -ENOSYS; }
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; }
static inline int kernfs_setattr(struct kernfs_node *kn,
const struct iattr *iattr)
{ return -ENOSYS; }
static inline __poll_t kernfs_generic_poll(struct kernfs_open_file *of,
struct poll_table_struct *pt)
{ return -ENOSYS; }
static inline void kernfs_notify(struct kernfs_node *kn) { }
static inline int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
void *value, size_t size)
{ return -ENOSYS; }
static inline int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
const void *value, size_t size, int flags)
{ return -ENOSYS; }
static inline const void *kernfs_super_ns(struct super_block *sb)
{ return NULL; }
static inline int kernfs_get_tree(struct fs_context *fc)
{ return -ENOSYS; }
static inline void kernfs_free_fs_context(struct fs_context *fc) { }
static inline void kernfs_kill_sb(struct super_block *sb) { }
static inline void kernfs_init(void) { }
#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
*
* If @kn is NULL result will be "(null)".
*
* Returns the length of the full path. If the full length is equal to or
* greater than @buflen, @buf contains the truncated path with the trailing
* '\0'. On error, -errno 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);
}
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);
}
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);
}
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,
GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
priv, NULL);
}
static inline int kernfs_remove_by_name(struct kernfs_node *parent,
const char *name)
{
return kernfs_remove_by_name_ns(parent, name, NULL);
}
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);
}
#endif /* __LINUX_KERNFS_H */