/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Filesystem access notification for Linux
 *
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 */

#ifndef __LINUX_FSNOTIFY_BACKEND_H
#define __LINUX_FSNOTIFY_BACKEND_H

#ifdef __KERNEL__

#include <linux/idr.h> /* inotify uses this */
#include <linux/fs.h> /* struct inode */
#include <linux/list.h>
#include <linux/path.h> /* struct path */
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/user_namespace.h>
#include <linux/refcount.h>

/*
 * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
 * convert between them.  dnotify only needs conversion at watch creation
 * so no perf loss there.  fanotify isn't defined yet, so it can use the
 * wholes if it needs more events.
 */
#define FS_ACCESS               0x00000001      /* File was accessed */
#define FS_MODIFY               0x00000002      /* File was modified */
#define FS_ATTRIB               0x00000004      /* Metadata changed */
#define FS_CLOSE_WRITE          0x00000008      /* Writtable file was closed */
#define FS_CLOSE_NOWRITE        0x00000010      /* Unwrittable file closed */
#define FS_OPEN                 0x00000020      /* File was opened */
#define FS_MOVED_FROM           0x00000040      /* File was moved from X */
#define FS_MOVED_TO             0x00000080      /* File was moved to Y */
#define FS_CREATE               0x00000100      /* Subfile was created */
#define FS_DELETE               0x00000200      /* Subfile was deleted */
#define FS_DELETE_SELF          0x00000400      /* Self was deleted */
#define FS_MOVE_SELF            0x00000800      /* Self was moved */

#define FS_UNMOUNT              0x00002000      /* inode on umount fs */
#define FS_Q_OVERFLOW           0x00004000      /* Event queued overflowed */
#define FS_IN_IGNORED           0x00008000      /* last inotify event here */

#define FS_OPEN_PERM            0x00010000      /* open event in an permission hook */
#define FS_ACCESS_PERM          0x00020000      /* access event in a permissions hook */

#define FS_EXCL_UNLINK          0x04000000      /* do not send events if object is unlinked */
#define FS_ISDIR                0x40000000      /* event occurred against dir */
#define FS_IN_ONESHOT           0x80000000      /* only send event once */

#define FS_DN_RENAME            0x10000000      /* file renamed */
#define FS_DN_MULTISHOT         0x20000000      /* dnotify multishot */

/* This inode cares about things that happen to its children.  Always set for
 * dnotify and inotify. */
#define FS_EVENT_ON_CHILD       0x08000000

/* This is a list of all events that may get sent to a parernt based on fs event
 * happening to inodes inside that directory */
#define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
                                   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
                                   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
                                   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)

#define FS_MOVE                 (FS_MOVED_FROM | FS_MOVED_TO)

#define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM)

#define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
                             FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
                             FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
                             FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
                             FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
                             FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \
                             FS_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \
                             FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)

struct fsnotify_group;
struct fsnotify_event;
struct fsnotify_mark;
struct fsnotify_event_private_data;
struct fsnotify_fname;
struct fsnotify_iter_info;

/*
 * Each group much define these ops.  The fsnotify infrastructure will call
 * these operations for each relevant group.
 *
 * handle_event - main call for a group to handle an fs event
 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
 * freeing_mark - called when a mark is being destroyed for some reason.  The group
 *              MUST be holding a reference on each mark and that reference must be
 *              dropped in this function.  inotify uses this function to send
 *              userspace messages that marks have been removed.
 */
struct fsnotify_ops {
        int (*handle_event)(struct fsnotify_group *group,
                            struct inode *inode,
                            struct fsnotify_mark *inode_mark,
                            struct fsnotify_mark *vfsmount_mark,
                            u32 mask, const void *data, int data_type,
                            const unsigned char *file_name, u32 cookie,
                            struct fsnotify_iter_info *iter_info);
        void (*free_group_priv)(struct fsnotify_group *group);
        void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
        void (*free_event)(struct fsnotify_event *event);
        /* called on final put+free to free memory */
        void (*free_mark)(struct fsnotify_mark *mark);
};

/*
 * all of the information about the original object we want to now send to
 * a group.  If you want to carry more info from the accessing task to the
 * listener this structure is where you need to be adding fields.
 */
struct fsnotify_event {
        struct list_head list;
        /* inode may ONLY be dereferenced during handle_event(). */
        struct inode *inode;    /* either the inode the event happened to or its parent */
        u32 mask;               /* the type of access, bitwise OR for FS_* event types */
};

/*
 * A group is a "thing" that wants to receive notification about filesystem
 * events.  The mask holds the subset of event types this group cares about.
 * refcnt on a group is up to the implementor and at any moment if it goes 0
 * everything will be cleaned up.
 */
struct fsnotify_group {
        /*
         * How the refcnt is used is up to each group.  When the refcnt hits 0
         * fsnotify will clean up all of the resources associated with this group.
         * As an example, the dnotify group will always have a refcnt=1 and that
         * will never change.  Inotify, on the other hand, has a group per
         * inotify_init() and the refcnt will hit 0 only when that fd has been
         * closed.
         */
        refcount_t refcnt;              /* things with interest in this group */

        const struct fsnotify_ops *ops; /* how this group handles things */

        /* needed to send notification to userspace */
        spinlock_t notification_lock;           /* protect the notification_list */
        struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
        wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
        unsigned int q_len;                     /* events on the queue */
        unsigned int max_events;                /* maximum events allowed on the list */
        /*
         * Valid fsnotify group priorities.  Events are send in order from highest
         * priority to lowest priority.  We default to the lowest priority.
         */
        #define FS_PRIO_0       0 /* normal notifiers, no permissions */
        #define FS_PRIO_1       1 /* fanotify content based access control */
        #define FS_PRIO_2       2 /* fanotify pre-content access */
        unsigned int priority;
        bool shutdown;          /* group is being shut down, don't queue more events */

        /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
        struct mutex mark_mutex;        /* protect marks_list */
        atomic_t num_marks;             /* 1 for each mark and 1 for not being
                                         * past the point of no return when freeing
                                         * a group */
        struct list_head marks_list;    /* all inode marks for this group */

        struct fasync_struct *fsn_fa;    /* async notification */

        struct fsnotify_event *overflow_event;  /* Event we queue when the
                                                 * notification list is too
                                                 * full */
        atomic_t user_waits;            /* Number of tasks waiting for user
                                         * response */

        /* groups can define private fields here or use the void *private */
        union {
                void *private;
#ifdef CONFIG_INOTIFY_USER
                struct inotify_group_private_data {
                        spinlock_t      idr_lock;
                        struct idr      idr;
                        struct ucounts *ucounts;
                } inotify_data;
#endif
#ifdef CONFIG_FANOTIFY
                struct fanotify_group_private_data {
                        /* allows a group to block waiting for a userspace response */
                        struct list_head access_list;
                        wait_queue_head_t access_waitq;
                        int f_flags;
                        unsigned int max_marks;
                        struct user_struct *user;
                        bool audit;
                } fanotify_data;
#endif /* CONFIG_FANOTIFY */
        };
};

/* when calling fsnotify tell it if the data is a path or inode */
#define FSNOTIFY_EVENT_NONE     0
#define FSNOTIFY_EVENT_PATH     1
#define FSNOTIFY_EVENT_INODE    2

/*
 * Inode / vfsmount point to this structure which tracks all marks attached to
 * the inode / vfsmount. The reference to inode / vfsmount is held by this
 * structure. We destroy this structure when there are no more marks attached
 * to it. The structure is protected by fsnotify_mark_srcu.
 */
struct fsnotify_mark_connector {
        spinlock_t lock;
#define FSNOTIFY_OBJ_TYPE_INODE         0x01
#define FSNOTIFY_OBJ_TYPE_VFSMOUNT      0x02
#define FSNOTIFY_OBJ_ALL_TYPES          (FSNOTIFY_OBJ_TYPE_INODE | \
                                         FSNOTIFY_OBJ_TYPE_VFSMOUNT)
        unsigned int flags;     /* Type of object [lock] */
        union { /* Object pointer [lock] */
                struct inode *inode;
                struct vfsmount *mnt;
        };
        union {
                struct hlist_head list;
                /* Used listing heads to free after srcu period expires */
                struct fsnotify_mark_connector *destroy_next;
        };
};

/*
 * A mark is simply an object attached to an in core inode which allows an
 * fsnotify listener to indicate they are either no longer interested in events
 * of a type matching mask or only interested in those events.
 *
 * These are flushed when an inode is evicted from core and may be flushed
 * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
 * users (such as dnotify) will flush these when the open fd is closed and not
 * at inode eviction or modification.
 *
 * Text in brackets is showing the lock(s) protecting modifications of a
 * particular entry. obj_lock means either inode->i_lock or
 * mnt->mnt_root->d_lock depending on the mark type.
 */
struct fsnotify_mark {
        /* Mask this mark is for [mark->lock, group->mark_mutex] */
        __u32 mask;
        /* We hold one for presence in g_list. Also one ref for each 'thing'
         * in kernel that found and may be using this mark. */
        refcount_t refcnt;
        /* Group this mark is for. Set on mark creation, stable until last ref
         * is dropped */
        struct fsnotify_group *group;
        /* List of marks by group->i_fsnotify_marks. Also reused for queueing
         * mark into destroy_list when it's waiting for the end of SRCU period
         * before it can be freed. [group->mark_mutex] */
        struct list_head g_list;
        /* Protects inode / mnt pointers, flags, masks */
        spinlock_t lock;
        /* List of marks for inode / vfsmount [connector->lock, mark ref] */
        struct hlist_node obj_list;
        /* Head of list of marks for an object [mark ref] */
        struct fsnotify_mark_connector *connector;
        /* Events types to ignore [mark->lock, group->mark_mutex] */
        __u32 ignored_mask;
#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x01
#define FSNOTIFY_MARK_FLAG_ALIVE                0x02
#define FSNOTIFY_MARK_FLAG_ATTACHED             0x04
        unsigned int flags;             /* flags [mark->lock] */
};

#ifdef CONFIG_FSNOTIFY

/* called from the vfs helpers */

/* main fsnotify call to send events */
extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
                    const unsigned char *name, u32 cookie);
extern int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask);
extern void __fsnotify_inode_delete(struct inode *inode);
extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
extern u32 fsnotify_get_cookie(void);

static inline int fsnotify_inode_watches_children(struct inode *inode)
{
        /* FS_EVENT_ON_CHILD is set if the inode may care */
        if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
                return 0;
        /* this inode might care about child events, does it care about the
         * specific set of events that can happen on a child? */
        return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
}

/*
 * Update the dentry with a flag indicating the interest of its parent to receive
 * filesystem events when those events happens to this dentry->d_inode.
 */
static inline void fsnotify_update_flags(struct dentry *dentry)
{
        assert_spin_locked(&dentry->d_lock);

        /*
         * Serialisation of setting PARENT_WATCHED on the dentries is provided
         * by d_lock. If inotify_inode_watched changes after we have taken
         * d_lock, the following __fsnotify_update_child_dentry_flags call will
         * find our entry, so it will spin until we complete here, and update
         * us with the new state.
         */
        if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
                dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
        else
                dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
}

/* called from fsnotify listeners, such as fanotify or dnotify */

/* create a new group */
extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
/* get reference to a group */
extern void fsnotify_get_group(struct fsnotify_group *group);
/* drop reference on a group from fsnotify_alloc_group */
extern void fsnotify_put_group(struct fsnotify_group *group);
/* group destruction begins, stop queuing new events */
extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
/* destroy group */
extern void fsnotify_destroy_group(struct fsnotify_group *group);
/* fasync handler function */
extern int fsnotify_fasync(int fd, struct file *file, int on);
/* Free event from memory */
extern void fsnotify_destroy_event(struct fsnotify_group *group,
                                   struct fsnotify_event *event);
/* attach the event to the group notification queue */
extern int fsnotify_add_event(struct fsnotify_group *group,
                              struct fsnotify_event *event,
                              int (*merge)(struct list_head *,
                                           struct fsnotify_event *));
/* true if the group notification queue is empty */
extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
/* return, but do not dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
/* return AND dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);

/* functions used to manipulate the marks attached to inodes */

/* Calculate mask of events for a list of marks */
extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn);
extern void fsnotify_init_mark(struct fsnotify_mark *mark,
                               struct fsnotify_group *group);
/* Find mark belonging to given group in the list of marks */
extern struct fsnotify_mark *fsnotify_find_mark(
                                struct fsnotify_mark_connector __rcu **connp,
                                struct fsnotify_group *group);
/* attach the mark to the inode or vfsmount */
extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct inode *inode,
                             struct vfsmount *mnt, int allow_dups);
extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
                                    struct inode *inode, struct vfsmount *mnt, int allow_dups);
/* given a group and a mark, flag mark to be freed when all references are dropped */
extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
                                  struct fsnotify_group *group);
/* detach mark from inode / mount list, group list, drop inode reference */
extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
/* free mark */
extern void fsnotify_free_mark(struct fsnotify_mark *mark);
/* run all the marks in a group, and clear all of the marks attached to given object type */
extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group, unsigned int type);
/* run all the marks in a group, and clear all of the vfsmount marks */
static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
{
        fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT);
}
/* run all the marks in a group, and clear all of the inode marks */
static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
{
        fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE);
}
extern void fsnotify_get_mark(struct fsnotify_mark *mark);
extern void fsnotify_put_mark(struct fsnotify_mark *mark);
extern void fsnotify_unmount_inodes(struct super_block *sb);
extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);

/* put here because inotify does some weird stuff when destroying watches */
extern void fsnotify_init_event(struct fsnotify_event *event,
                                struct inode *to_tell, u32 mask);

#else

static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
                           const unsigned char *name, u32 cookie)
{
        return 0;
}

static inline int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask)
{
        return 0;
}

static inline void __fsnotify_inode_delete(struct inode *inode)
{}

static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
{}

static inline void fsnotify_update_flags(struct dentry *dentry)
{}

static inline u32 fsnotify_get_cookie(void)
{
        return 0;
}

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

#endif  /* CONFIG_FSNOTIFY */

#endif  /* __KERNEL __ */

#endif  /* __LINUX_FSNOTIFY_BACKEND_H */