shim_handle.h

/* SPDX-License-Identifier: LGPL-3.0-or-later */
/* Copyright (C) 2014 Stony Brook University */

/*
 * Definitions of types and functions for file/handle bookkeeping.
 */

#ifndef _SHIM_HANDLE_H_
#define _SHIM_HANDLE_H_

#include <asm/fcntl.h>
#include <asm/resource.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/shm.h>
#include <linux/un.h>
#include <stdalign.h>
#include <stdbool.h>
#include <stdint.h>

#include "atomic.h"  // TODO: migrate to stdatomic.h
#include "list.h"
#include "pal.h"
#include "shim_defs.h"
#include "shim_sysv.h"
#include "shim_types.h"

/* Handle types. Many of these are used by a single filesystem. */
enum shim_handle_type {
    /* Files: */
    TYPE_FILE,       /* host files, used by `chroot` filesystem */
    TYPE_DEV,        /* emulated devices, used by `dev` filesystem */
    TYPE_STR,        /* string-based files, handled by `str_*` functions, used by several
                      * filesystems */
    TYPE_PSEUDO,     /* pseudo nodes (currently directories), handled by `pseudo_*` functions, used
                      * by several filesystems */

    /* Pipes and sockets: */
    TYPE_PIPE,       /* pipes, used by `pipe` filesystem */
    TYPE_SOCK,       /* sockets, used by `socket` filesystem */

    /* Special handles: */
    TYPE_SEM,        /* System V semaphores, see `shim_semget.c` */
    TYPE_MSG,        /* System V messages, see `shim_msgget.c` */
    TYPE_EPOLL,      /* epoll handles, see `shim_epoll.c` */
    TYPE_EVENTFD,    /* eventfd handles, used by `eventfd` filesystem */
};

struct shim_handle;
struct shim_thread;
struct shim_vma;

enum shim_file_type {
    FILE_UNKNOWN,
    FILE_REGULAR,
    FILE_DIR,
    FILE_DEV,
    FILE_TTY,
};

struct shim_file_data {
    struct shim_lock lock;
    struct atomic_int version;
    bool queried;
    enum shim_file_type type;
    mode_t mode;
    struct atomic_int size;
    struct shim_qstr host_uri;
    unsigned long atime;
    unsigned long mtime;
    unsigned long ctime;
    unsigned long nlink;
};

struct shim_file_handle {
    unsigned int version;
    struct shim_file_data* data;

    enum shim_file_type type;
    off_t size;
    off_t marker;
};

#define FILE_HANDLE_DATA(hdl)  ((hdl)->info.file.data)
#define FILE_DENTRY_DATA(dent) ((struct shim_file_data*)(dent)->data)

struct shim_dev_ops {
    /* open: provide a filename relative to the mount point and flags,
       modify the shim handle */
    int (*open)(struct shim_handle* hdl, const char* name, int flags);

    /* close: clean up the file state inside the handle */
    int (*close)(struct shim_handle* hdl);

    /* read: the content from the file opened as handle */
    ssize_t (*read)(struct shim_handle* hdl, void* buf, size_t count);

    /* write: the content from the file opened as handle */
    ssize_t (*write)(struct shim_handle* hdl, const void* buf, size_t count);

    /* flush: flush out user buffer */
    int (*flush)(struct shim_handle* hdl);

    /* seek: the content from the file opened as handle */
    off_t (*seek)(struct shim_handle* hdl, off_t offset, int whence);

    int (*truncate)(struct shim_handle* hdl, uint64_t len);

    int (*mode)(const char* name, mode_t* mode);

    /* stat, hstat: get status of the file */
    int (*stat)(const char* name, struct stat* buf);
    int (*hstat)(struct shim_handle* hdl, struct stat* buf);
};

int dev_update_dev_ops(struct shim_handle* hdl);

struct shim_dev_handle {
    struct shim_dev_ops dev_ops;
};

struct shim_pipe_handle {
    bool ready_for_ops; /* true for pipes, false for FIFOs that were mknod'ed but not open'ed */
    char name[PIPE_URI_SIZE];
};

#define SOCK_STREAM   1
#define SOCK_DGRAM    2
#define SOCK_NONBLOCK 04000
#define SOCK_CLOEXEC  02000000

#define SOL_TCP 6

#define PF_LOCAL 1
#define PF_UNIX  PF_LOCAL
#define PF_FILE  PF_LOCAL
#define PF_INET  2
#define PF_INET6 10

#define AF_UNIX  PF_UNIX
#define AF_INET  PF_INET
#define AF_INET6 PF_INET6

#define SOCK_URI_SIZE 108

enum shim_sock_state {
    SOCK_CREATED,
    SOCK_BOUND,
    SOCK_CONNECTED,
    SOCK_BOUNDCONNECTED,
    SOCK_LISTENED,
    SOCK_ACCEPTED,
    SOCK_SHUTDOWN,
};

struct shim_sock_handle {
    int domain;
    int sock_type;
    int protocol;
    int error;

    enum shim_sock_state sock_state;

    union shim_sock_addr {
        // INET addr
        struct {
            struct addr_inet {
                unsigned short port;
                unsigned short ext_port;
                union {
                    struct in_addr v4;
                    struct in6_addr v6;
                } addr;
            } bind, conn;
        } in;
        // UNIX addr
        struct addr_unix {
            struct shim_dentry* dentry;
            char name[PIPE_URI_SIZE];
        } un;
    } addr;

    struct shim_sock_option {
        struct shim_sock_option* next;
        int level;
        int optname;
        int optlen;
        char optval[];
    }* pending_options;

    struct shim_peek_buffer {
        size_t size;             /* total size (capacity) of buffer `buf` */
        size_t start;            /* beginning of buffered but yet unread data in `buf` */
        size_t end;              /* end of buffered but yet unread data in `buf` */
        char uri[SOCK_URI_SIZE]; /* cached URI for recvfrom(udp_socket) case */
        char buf[];              /* peek buffer of size `size` */
    }* peek_buffer;
};

struct shim_dirent {
    struct shim_dirent* next;
    unsigned long ino; /* Inode number */
    unsigned char type;
    char name[]; /* File name (null-terminated) */
};

#define SHIM_DIRENT_SIZE      offsetof(struct shim_dirent, name)
#define SHIM_DIRENT_ALIGNMENT alignof(struct shim_dirent)
/* Size of struct shim_dirent instance together with alignment,
 * which might be different depending on the length of the name field */
#define SHIM_DIRENT_ALIGNED_SIZE(len) ALIGN_UP(SHIM_DIRENT_SIZE + (len), SHIM_DIRENT_ALIGNMENT)

struct shim_dir_handle {
    int offset;
    struct shim_dentry* dotdot;
    struct shim_dentry* dot;
    struct shim_dentry** buf;
    struct shim_dentry** ptr;
};

struct msg_type;
struct msg_item;
struct msg_client;

#define MAX_SYSV_CLIENTS 32

DEFINE_LIST(shim_msg_handle);
struct shim_msg_handle {
    unsigned long msqkey; /* msg queue key from user */
    IDTYPE msqid;         /* msg queue identifier */
    bool owned;           /* owned by current process */
    int perm;        /* access permissions */
    bool deleted;    /* marking the queue deleted */
    int nmsgs;       /* number of msgs */
    int currentsize; /* current size in bytes */
    struct msg_qobj* queue;
    int queuesize;
    int queueused;
    struct msg_qobj* freed;
    PAL_HANDLE event; /* event for waiting */
    int ntypes;
    int maxtypes;
    struct msg_type* types;
    LIST_TYPE(shim_msg_handle) key_hlist;
    LIST_TYPE(shim_msg_handle) qid_hlist;
};

struct sem_objs;

DEFINE_LIST(shim_sem_handle);
struct shim_sem_handle {
    unsigned long semkey;
    IDTYPE semid;
    bool owned;
    int perm;
    bool deleted;
    PAL_HANDLE event;
    int nsems;
    struct sem_obj* sems;
    int nreqs;
    LISTP_TYPE(sem_ops) migrated;
    LIST_TYPE(shim_sem_handle) list;
    LIST_TYPE(shim_sem_handle) key_hlist;
    LIST_TYPE(shim_sem_handle) sid_hlist;
};

struct shim_str_data {
    REFTYPE ref_count;
    char* str;
    off_t len;
    size_t buf_size;
    bool dirty;
    int (*update)(struct shim_handle* hdl);
    int (*modify)(struct shim_handle* hdl);
};

struct shim_str_handle {
    struct shim_str_data* data; /* inode is stored in dentry, too.
                                   store pointer here for efficiency */
    char* ptr;
};

DEFINE_LIST(shim_epoll_item);
DEFINE_LISTP(shim_epoll_item);
struct shim_epoll_item {
    FDTYPE fd;
    uint64_t data;
    unsigned int events;
    unsigned int revents;
    /* The two references below are not ref-counted (to prevent cycles). When a handle is dropped
     * (ref-count goes to 0) it is also removed from all epoll instances. When an epoll instance is
     * destroyed, all handles that it traced are removed from it. */
    struct shim_handle* handle;      /* reference to monitored object (socket, pipe, file, etc) */
    struct shim_handle* epoll;       /* reference to epoll object that monitors handle object */
    LIST_TYPE(shim_epoll_item) list; /* list of shim_epoll_items, used by epoll object (via `fds`) */
    LIST_TYPE(shim_epoll_item) back; /* list of epolls, used by handle object (via `epolls`) */
};

struct shim_epoll_handle {
    size_t waiter_cnt;

    /* Number of items on fds list. */
    size_t fds_count;

    AEVENTTYPE event;
    LISTP_TYPE(shim_epoll_item) fds;
};

struct shim_mount;
struct shim_qstr;
struct shim_dentry;

/* The epolls list links to the back field of the shim_epoll_item structure
 */
struct shim_handle {
    enum shim_handle_type type;
    bool is_dir;

    REFTYPE ref_count;

    char fs_type[8];
    struct shim_mount* fs;
    struct shim_qstr path;
    struct shim_dentry* dentry;

    /* If this handle is registered for any epoll handle, this list contains
     * a shim_epoll_item object in correspondence with the epoll handle. */
    LISTP_TYPE(shim_epoll_item) epolls;

    struct shim_qstr uri; /* URI representing this handle, it is not
                           * necessary to be set. */

    PAL_HANDLE pal_handle;

    /* Type-specific fields: when accessing, ensure that `type` field is appropriate first (at least
     * by using assert()) */
    union {
        struct shim_file_handle file;    /* TYPE_FILE */
        struct shim_dev_handle dev;      /* TYPE_DEV */
        struct shim_str_handle str;      /* TYPE_STR */
        /* (no data) */                  /* TYPE_PSEUDO */

        struct shim_pipe_handle pipe;    /* TYPE_PIPE */
        struct shim_sock_handle sock;    /* TYPE_SOCK */

        struct shim_sem_handle sem;      /* TYPE_SEM */
        struct shim_msg_handle msg;      /* TYPE_MSG */
        struct shim_epoll_handle epoll;  /* TYPE_EPOLL */
        /* (no data) */                  /* TYPE_EVENTFD */
    } info;

    struct shim_dir_handle dir_info;

    int flags; /* Linux' O_* flags */
    int acc_mode;
    IDTYPE owner;
    struct shim_lock lock;
};

/* allocating / manage handle */
struct shim_handle* get_new_handle(void);
void get_handle(struct shim_handle* hdl);
void put_handle(struct shim_handle* hdl);

/* Set handle to non-blocking or blocking mode. */
int set_handle_nonblocking(struct shim_handle* hdl, bool on);

/* file descriptor table */
struct shim_fd_handle {
    FDTYPE vfd; /* virtual file descriptor */
    int flags;  /* file descriptor flags, only FD_CLOEXEC */

    struct shim_handle* handle;
};

struct shim_handle_map {
    /* the top of created file descriptors */
    FDTYPE fd_size;
    FDTYPE fd_top;

    /* refrence count and lock */
    REFTYPE ref_count;
    struct shim_lock lock;

    /* An array of file descriptor belong to this mapping */
    struct shim_fd_handle** map;
};

/* allocating file descriptors */
#define FD_NULL                     ((FDTYPE)-1)
#define HANDLE_ALLOCATED(fd_handle) ((fd_handle) && (fd_handle)->vfd != FD_NULL)

struct shim_handle* __get_fd_handle(FDTYPE fd, int* flags, struct shim_handle_map* map);
struct shim_handle* get_fd_handle(FDTYPE fd, int* flags, struct shim_handle_map* map);

/*!
 * \brief Assign new fd to a handle.
 *
 * \param hdl A handle to be mapped to the new fd.
 * \param flags Flags assigned to new shim_fd_handle.
 * \param handle_map Handle map to be used. If NULL is passed, current thread's handle map is used.
 *
 * Creates mapping for the given handle to a new file descriptor which is then returned.
 * Uses the lowest, non-negative available number for the new fd.
 */
int set_new_fd_handle(struct shim_handle* hdl, int fd_flags, struct shim_handle_map* map);
int set_new_fd_handle_by_fd(FDTYPE fd, struct shim_handle* hdl, int fd_flags,
                            struct shim_handle_map* map);
int set_new_fd_handle_above_fd(FDTYPE fd, struct shim_handle* hdl, int fd_flags,
                               struct shim_handle_map* map);
struct shim_handle* __detach_fd_handle(struct shim_fd_handle* fd, int* flags,
                                       struct shim_handle_map* map);
struct shim_handle* detach_fd_handle(FDTYPE fd, int* flags, struct shim_handle_map* map);

/* manage handle mapping */
int dup_handle_map(struct shim_handle_map** new_map, struct shim_handle_map* old_map);
void get_handle_map(struct shim_handle_map* map);
void put_handle_map(struct shim_handle_map* map);
int walk_handle_map(int (*callback)(struct shim_fd_handle*, struct shim_handle_map*),
                    struct shim_handle_map* map);

int init_handle(void);
int init_important_handles(void);

int get_file_size(struct shim_handle* file, uint64_t* size);

int do_handle_read(struct shim_handle* hdl, void* buf, int count);
int do_handle_write(struct shim_handle* hdl, const void* buf, int count);

#endif /* _SHIM_HANDLE_H_ */