/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2001 Dag-Erling Smørgrav
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _PSEUDOFS_H_INCLUDED
#define _PSEUDOFS_H_INCLUDED

#include <sys/jail.h>

/*
 * Opaque structures
 */
struct mntarg;
struct mount;
struct nameidata;
struct proc;
struct sbuf;
struct statfs;
struct thread;
struct uio;
struct vfsconf;
struct vnode;

/*
 * Limits and constants
 */
#define PFS_NAMELEN             128
#define PFS_FSNAMELEN           16      /* equal to MFSNAMELEN */
#define PFS_DELEN               (offsetof(struct dirent, d_name) + PFS_NAMELEN)

typedef enum {
        pfstype_none = 0,
        pfstype_root,
        pfstype_dir,
        pfstype_this,
        pfstype_parent,
        pfstype_file,
        pfstype_symlink,
        pfstype_procdir
} pfs_type_t;

/*
 * Flags
 */
#define PFS_RD          0x0001  /* readable */
#define PFS_WR          0x0002  /* writeable */
#define PFS_RDWR        (PFS_RD|PFS_WR)
#define PFS_RAWRD       0x0004  /* raw reader */
#define PFS_RAWWR       0x0008  /* raw writer */
#define PFS_RAW         (PFS_RAWRD|PFS_RAWWR)
#define PFS_PROCDEP     0x0010  /* process-dependent */
#define PFS_NOWAIT      0x0020 /* allow malloc to fail */
#define PFS_AUTODRAIN   0x0040  /* sbuf_print can sleep to drain */

/*
 * Data structures
 */
struct pfs_info;
struct pfs_node;

/*
 * Init / uninit callback
 */
#define PFS_INIT_ARGS \
        struct pfs_info *pi, struct vfsconf *vfc
#define PFS_INIT_ARGNAMES \
        pi, vfc
#define PFS_INIT_PROTO(name) \
        int name(PFS_INIT_ARGS);
typedef int (*pfs_init_t)(PFS_INIT_ARGS);

/*
 * Filler callback
 * Called with proc held but unlocked
 */
#define PFS_FILL_ARGS \
        struct thread *td, struct proc *p, struct pfs_node *pn, \
        struct sbuf *sb, struct uio *uio
#define PFS_FILL_ARGNAMES \
        td, p, pn, sb, uio
#define PFS_FILL_PROTO(name) \
        int name(PFS_FILL_ARGS);
typedef int (*pfs_fill_t)(PFS_FILL_ARGS);

/*
 * Attribute callback
 * Called with proc locked
 */
struct vattr;
#define PFS_ATTR_ARGS \
        struct thread *td, struct proc *p, struct pfs_node *pn, \
        struct vattr *vap
#define PFS_ATTR_ARGNAMES \
        td, p, pn, vap
#define PFS_ATTR_PROTO(name) \
        int name(PFS_ATTR_ARGS);
typedef int (*pfs_attr_t)(PFS_ATTR_ARGS);

/*
 * Visibility callback
 * Called with proc locked
 */
#define PFS_VIS_ARGS \
        struct thread *td, struct proc *p, struct pfs_node *pn
#define PFS_VIS_ARGNAMES \
        td, p, pn
#define PFS_VIS_PROTO(name) \
        int name(PFS_VIS_ARGS);
typedef int (*pfs_vis_t)(PFS_VIS_ARGS);

/*
 * Ioctl callback
 * Called with proc locked
 */
#define PFS_IOCTL_ARGS \
        struct thread *td, struct proc *p, struct pfs_node *pn, \
        unsigned long cmd, void *data
#define PFS_IOCTL_ARGNAMES \
        td, p, pn, cmd, data
#define PFS_IOCTL_PROTO(name) \
        int name(PFS_IOCTL_ARGS);
typedef int (*pfs_ioctl_t)(PFS_IOCTL_ARGS);

/*
 * Getextattr callback
 * Called with proc locked
 */
#define PFS_GETEXTATTR_ARGS \
        struct thread *td, struct proc *p, struct pfs_node *pn, \
        int attrnamespace, const char *name, struct uio *uio,   \
        size_t *size, struct ucred *cred
#define PFS_GETEXTATTR_ARGNAMES \
        td, p, pn, attrnamespace, name, uio, size, cred
#define PFS_GETEXTATTR_PROTO(name) \
        int name(PFS_GETEXTATTR_ARGS);
struct ucred;
typedef int (*pfs_getextattr_t)(PFS_GETEXTATTR_ARGS);

/*
 * Last-close callback
 * Called with proc locked
 */
#define PFS_CLOSE_ARGS \
        struct thread *td, struct proc *p, struct pfs_node *pn
#define PFS_CLOSE_ARGNAMES \
        td, p, pn
#define PFS_CLOSE_PROTO(name) \
        int name(PFS_CLOSE_ARGS);
typedef int (*pfs_close_t)(PFS_CLOSE_ARGS);

/*
 * Destroy callback
 */
#define PFS_DESTROY_ARGS \
        struct pfs_node *pn
#define PFS_DESTROY_ARGNAMES \
        pn
#define PFS_DESTROY_PROTO(name) \
        int name(PFS_DESTROY_ARGS);
typedef int (*pfs_destroy_t)(PFS_DESTROY_ARGS);

/*
 * pfs_info: describes a pseudofs instance
 *
 * The pi_mutex is only used to avoid using the global subr_unit lock
 * for unrhdr.  The rest of struct pfs_info is only modified during
 * vfs_init() and vfs_uninit() of the consumer filesystem.
 */
struct pfs_info {
        char                     pi_name[PFS_FSNAMELEN];
        pfs_init_t               pi_init;
        pfs_init_t               pi_uninit;

        /* members below this line are initialized at run time */
        struct pfs_node         *pi_root;
        struct mtx               pi_mutex;
        struct unrhdr           *pi_unrhdr;
};

/*
 * pfs_node: describes a node (file or directory) within a pseudofs
 *
 * - Fields marked (o) are protected by the node's own mutex.
 * - Fields marked (p) are protected by the node's parent's mutex.
 * - Remaining fields are not protected by any lock and are assumed to be
 *   immutable once the node has been created.
 *
 * To prevent deadlocks, if a node's mutex is to be held at the same time
 * as its parent's (e.g. when adding or removing nodes to a directory),
 * the parent's mutex must always be acquired first.  Unfortunately, this
 * is not enforcable by WITNESS.
 */
struct pfs_node {
        pfs_type_t               pn_type;
        int                      pn_flags;
        struct mtx               pn_mutex;
        void                    *pn_data;               /* (o) */

        pfs_fill_t               pn_fill;
        pfs_ioctl_t              pn_ioctl;
        pfs_close_t              pn_close;
        pfs_attr_t               pn_attr;
        pfs_vis_t                pn_vis;
        pfs_getextattr_t         pn_getextattr;
        pfs_destroy_t            pn_destroy;

        struct pfs_info         *pn_info;
        u_int32_t                pn_fileno;             /* (o) */

        struct pfs_node         *pn_parent;             /* (o) */
        struct pfs_node         *pn_nodes;              /* (o) */
        struct pfs_node         *pn_last_node;          /* (o) */
        struct pfs_node         *pn_next;               /* (p) */
        char                     pn_name[];             /* Keep it last */
};

/*
 * VFS interface
 */
int              pfs_mount      (struct pfs_info *pi, struct mount *mp);
int              pfs_cmount     (struct mntarg *ma, void *data, uint64_t flags);
int              pfs_unmount    (struct mount *mp, int mntflags);
int              pfs_root       (struct mount *mp, int flags,
                                 struct vnode **vpp);
int              pfs_statfs     (struct mount *mp, struct statfs *sbp);
int              pfs_init       (struct pfs_info *pi, struct vfsconf *vfc);
int              pfs_uninit     (struct pfs_info *pi, struct vfsconf *vfc);

/*
 * Directory structure construction and manipulation
 */
int pfs_create_dir              (struct pfs_node *parent, struct pfs_node **opn,
                                 const char *name, pfs_attr_t attr,
                                 pfs_vis_t vis, pfs_destroy_t destroy,
                                 int flags);
int pfs_create_file             (struct pfs_node *parent, struct pfs_node **opn,
                                 const char *name, pfs_fill_t fill,
                                 pfs_attr_t attr, pfs_vis_t vis,
                                 pfs_destroy_t destroy, int flags);
int pfs_create_link             (struct pfs_node *parent, struct pfs_node **opn,
                                 const char *name, pfs_fill_t fill,
                                 pfs_attr_t attr, pfs_vis_t vis,
                                 pfs_destroy_t destroy, int flags);
struct pfs_node *pfs_find_node  (struct pfs_node *parent, const char *name);
void             pfs_purge      (struct pfs_node *pn);
int              pfs_destroy    (struct pfs_node *pn);

/*
 * Now for some initialization magic...
 */
#define PSEUDOFS(name, version, flags)                                  \
                                                                        \
static struct pfs_info name##_info = {                                  \
        #name,                                                          \
        name##_init,                                                    \
        name##_uninit,                                                  \
};                                                                      \
                                                                        \
static int                                                              \
_##name##_mount(struct mount *mp) {                                     \
        return (pfs_mount(&name##_info, mp));                           \
}                                                                       \
                                                                        \
static int                                                              \
_##name##_init(struct vfsconf *vfc) {                                   \
        return (pfs_init(&name##_info, vfc));                           \
}                                                                       \
                                                                        \
static int                                                              \
_##name##_uninit(struct vfsconf *vfc) {                                 \
        return (pfs_uninit(&name##_info, vfc));                         \
}                                                                       \
                                                                        \
static struct vfsops name##_vfsops = {                                  \
        .vfs_cmount =           pfs_cmount,                             \
        .vfs_init =             _##name##_init,                         \
        .vfs_mount =            _##name##_mount,                        \
        .vfs_root =             pfs_root,                               \
        .vfs_statfs =           pfs_statfs,                             \
        .vfs_uninit =           _##name##_uninit,                       \
        .vfs_unmount =          pfs_unmount,                            \
};                                                                      \
VFS_SET(name##_vfsops, name, VFCF_SYNTHETIC | flags);                   \
MODULE_VERSION(name, version);                                          \
MODULE_DEPEND(name, pseudofs, 1, 1, 1);

#endif