/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Filesystem superblock creation and reconfiguration context.
 *
 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#ifndef _LINUX_FS_CONTEXT_H
#define _LINUX_FS_CONTEXT_H

#include <linux/kernel.h>
#include <linux/refcount.h>
#include <linux/errno.h>
#include <linux/security.h>
#include <linux/mutex.h>

struct cred;
struct dentry;
struct file_operations;
struct file_system_type;
struct mnt_namespace;
struct net;
struct pid_namespace;
struct super_block;
struct user_namespace;
struct vfsmount;
struct path;

enum fs_context_purpose {
        FS_CONTEXT_FOR_MOUNT,           /* New superblock for explicit mount */
        FS_CONTEXT_FOR_SUBMOUNT,        /* New superblock for automatic submount */
        FS_CONTEXT_FOR_RECONFIGURE,     /* Superblock reconfiguration (remount) */
};

/*
 * Userspace usage phase for fsopen/fspick.
 */
enum fs_context_phase {
        FS_CONTEXT_CREATE_PARAMS,       /* Loading params for sb creation */
        FS_CONTEXT_CREATING,            /* A superblock is being created */
        FS_CONTEXT_AWAITING_MOUNT,      /* Superblock created, awaiting fsmount() */
        FS_CONTEXT_AWAITING_RECONF,     /* Awaiting initialisation for reconfiguration */
        FS_CONTEXT_RECONF_PARAMS,       /* Loading params for reconfiguration */
        FS_CONTEXT_RECONFIGURING,       /* Reconfiguring the superblock */
        FS_CONTEXT_FAILED,              /* Failed to correctly transition a context */
};

/*
 * Type of parameter value.
 */
enum fs_value_type {
        fs_value_is_undefined,
        fs_value_is_flag,               /* Value not given a value */
        fs_value_is_string,             /* Value is a string */
        fs_value_is_blob,               /* Value is a binary blob */
        fs_value_is_filename,           /* Value is a filename* + dirfd */
        fs_value_is_file,               /* Value is a file* */
};

/*
 * Configuration parameter.
 */
struct fs_parameter {
        const char              *key;           /* Parameter name */
        enum fs_value_type      type:8;         /* The type of value here */
        union {
                char            *string;
                void            *blob;
                struct filename *name;
                struct file     *file;
        };
        size_t  size;
        int     dirfd;
};

struct p_log {
        const char *prefix;
        struct fc_log *log;
};

/*
 * Filesystem context for holding the parameters used in the creation or
 * reconfiguration of a superblock.
 *
 * Superblock creation fills in ->root whereas reconfiguration begins with this
 * already set.
 *
 * See Documentation/filesystems/mount_api.rst
 */
struct fs_context {
        const struct fs_context_operations *ops;
        struct mutex            uapi_mutex;     /* Userspace access mutex */
        struct file_system_type *fs_type;
        void                    *fs_private;    /* The filesystem's context */
        void                    *sget_key;
        struct dentry           *root;          /* The root and superblock */
        struct user_namespace   *user_ns;       /* The user namespace for this mount */
        struct net              *net_ns;        /* The network namespace for this mount */
        const struct cred       *cred;          /* The mounter's credentials */
        struct p_log            log;            /* Logging buffer */
        const char              *source;        /* The source name (eg. dev path) */
        void                    *security;      /* LSM options */
        void                    *s_fs_info;     /* Proposed s_fs_info */
        unsigned int            sb_flags;       /* Proposed superblock flags (SB_*) */
        unsigned int            sb_flags_mask;  /* Superblock flags that were changed */
        unsigned int            s_iflags;       /* OR'd with sb->s_iflags */
        enum fs_context_purpose purpose:8;
        enum fs_context_phase   phase:8;        /* The phase the context is in */
        bool                    need_free:1;    /* Need to call ops->free() */
        bool                    global:1;       /* Goes into &init_user_ns */
        bool                    oldapi:1;       /* Coming from mount(2) */
        bool                    exclusive:1;    /* create new superblock, reject existing one */
};

struct fs_context_operations {
        void (*free)(struct fs_context *fc);
        int (*dup)(struct fs_context *fc, struct fs_context *src_fc);
        int (*parse_param)(struct fs_context *fc, struct fs_parameter *param);
        int (*parse_monolithic)(struct fs_context *fc, void *data);
        int (*get_tree)(struct fs_context *fc);
        int (*reconfigure)(struct fs_context *fc);
};

/*
 * fs_context manipulation functions.
 */
extern struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
                                                unsigned int sb_flags);
extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
                                                unsigned int sb_flags,
                                                unsigned int sb_flags_mask);
extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,
                                                struct dentry *reference);

extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
extern int vfs_parse_fs_qstr(struct fs_context *fc, const char *key,
                                const struct qstr *value);
static inline int vfs_parse_fs_string(struct fs_context *fc, const char *key,
                               const char *value)
{
        return vfs_parse_fs_qstr(fc, key, value ? &QSTR(value) : NULL);
}
int vfs_parse_monolithic_sep(struct fs_context *fc, void *data,
                             char *(*sep)(char **));
extern int generic_parse_monolithic(struct fs_context *fc, void *data);
extern int vfs_get_tree(struct fs_context *fc);
extern void put_fs_context(struct fs_context *fc);
extern int vfs_parse_fs_param_source(struct fs_context *fc,
                                     struct fs_parameter *param);
extern void fc_drop_locked(struct fs_context *fc);

extern int get_tree_nodev(struct fs_context *fc,
                         int (*fill_super)(struct super_block *sb,
                                           struct fs_context *fc));
extern int get_tree_single(struct fs_context *fc,
                         int (*fill_super)(struct super_block *sb,
                                           struct fs_context *fc));
extern int get_tree_keyed(struct fs_context *fc,
                         int (*fill_super)(struct super_block *sb,
                                           struct fs_context *fc),
                         void *key);

int setup_bdev_super(struct super_block *sb, int sb_flags,
                struct fs_context *fc);

#define GET_TREE_BDEV_QUIET_LOOKUP              0x0001
int get_tree_bdev_flags(struct fs_context *fc,
                int (*fill_super)(struct super_block *sb,
                                  struct fs_context *fc), unsigned int flags);

extern int get_tree_bdev(struct fs_context *fc,
                               int (*fill_super)(struct super_block *sb,
                                                 struct fs_context *fc));

extern const struct file_operations fscontext_fops;

/*
 * Mount error, warning and informational message logging.  This structure is
 * shareable between a mount and a subordinate mount.
 */
struct fc_log {
        refcount_t      usage;
        u8              head;           /* Insertion index in buffer[] */
        u8              tail;           /* Removal index in buffer[] */
        u8              need_free;      /* Mask of kfree'able items in buffer[] */
        struct module   *owner;         /* Owner module for strings that don't then need freeing */
        char            *buffer[8];
};

extern __attribute__((format(printf, 4, 5)))
void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...);

#define __logfc(fc, l, fmt, ...) \
        logfc((fc)->log.log, NULL, (l), (fmt), ## __VA_ARGS__)
#define __plogp(p, prefix, l, fmt, ...) \
        logfc((p)->log, (prefix), (l), (fmt), ## __VA_ARGS__)
#define __plog(p, l, fmt, ...) __plogp(p, (p)->prefix, l, fmt, ## __VA_ARGS__)

/**
 * infof - Store supplementary informational message
 * @fc: The context in which to log the informational message
 * @fmt: The format string
 *
 * Store the supplementary informational message for the process if the process
 * has enabled the facility.
 */
#define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__)
#define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__)
#define infofc(fc, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__)
#define infofcp(fc, prefix, fmt, ...) \
        __plogp((&(fc)->log), prefix, 'i', fmt, ## __VA_ARGS__)

/**
 * warnf - Store supplementary warning message
 * @fc: The context in which to log the error message
 * @fmt: The format string
 *
 * Store the supplementary warning message for the process if the process has
 * enabled the facility.
 */
#define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__)
#define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__)
#define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__)
#define warnfcp(fc, prefix, fmt, ...) \
        __plogp((&(fc)->log), prefix, 'w', fmt, ## __VA_ARGS__)

/**
 * errorf - Store supplementary error message
 * @fc: The context in which to log the error message
 * @fmt: The format string
 *
 * Store the supplementary error message for the process if the process has
 * enabled the facility.
 */
#define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__)
#define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__)
#define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS__)
#define errorfcp(fc, prefix, fmt, ...) \
        __plogp((&(fc)->log), prefix, 'e', fmt, ## __VA_ARGS__)

/**
 * invalf - Store supplementary invalid argument error message
 * @fc: The context in which to log the error message
 * @fmt: The format string
 *
 * Store the supplementary error message for the process if the process has
 * enabled the facility and return -EINVAL.
 */
#define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL)
#define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINVAL)
#define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL)
#define invalfcp(fc, prefix, fmt, ...) \
        (errorfcp(fc, prefix, fmt, ## __VA_ARGS__), -EINVAL)

#endif /* _LINUX_FS_CONTEXT_H */