source: mainline/uspace/srv/bd/file_bd/file_bd.c@ 1cbed6b

/*
 * Copyright (c) 2009 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - 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.
 */

/** @addtogroup bd
 * @{
 */

/**
 * @file
 * @brief File-backed block device driver
 *
 * Allows accessing a file as a block device. Useful for, e.g., mounting
 * a disk image.
 */

#include <stdio.h>
#include <unistd.h>
#include <ipc/ipc.h>
#include <ipc/bd.h>
#include <async.h>
#include <as.h>
#include <futex.h>
#include <devmap.h>
#include <sys/types.h>
#include <errno.h>
#include <bool.h>

#define NAME "file_bd"

static size_t comm_size;
static FILE *img;

static dev_handle_t dev_handle;
static atomic_t dev_futex = FUTEX_INITIALIZER;

static int file_bd_init(const char *fname);
static void file_bd_connection(ipc_callid_t iid, ipc_call_t *icall);
static int file_bd_read(off_t blk_idx, off_t size, void *buf);
static int file_bd_write(off_t blk_idx, off_t size, void *buf);

int main(int argc, char **argv)
{
        int rc;

        printf(NAME ": File-backed block device driver\n");

        if (argc != 3) {
                printf("Expected two arguments (image name, device name).\n");
                return -1;
        }

        if (file_bd_init(argv[1]) != EOK)
                return -1;

        rc = devmap_device_register(argv[2], &dev_handle);
        if (rc != EOK) {
                devmap_hangup_phone(DEVMAP_DRIVER);
                printf(NAME ": Unable to register device %s.\n",
                        argv[2]);
                return rc;
        }

        printf(NAME ": Accepting connections\n");
        async_manager();

        /* Not reached */
        return 0;
}

static int file_bd_init(const char *fname)
{
        int rc;

        rc = devmap_driver_register(NAME, file_bd_connection);
        if (rc < 0) {
                printf(NAME ": Unable to register driver.\n");
                return rc;
        }

        img = fopen(fname, "rb+");
        if (img == NULL)
                return EINVAL;

        return EOK;
}

static void file_bd_connection(ipc_callid_t iid, ipc_call_t *icall)
{
        void *fs_va = NULL;
        ipc_callid_t callid;
        ipc_call_t call;
        ipcarg_t method;
        int flags;
        int retval;
        off_t idx;
        off_t size;

        /* Answer the IPC_M_CONNECT_ME_TO call. */
        ipc_answer_0(iid, EOK);

        if (!ipc_share_out_receive(&callid, &comm_size, &flags)) {
                ipc_answer_0(callid, EHANGUP);
                return;
        }

        fs_va = as_get_mappable_page(comm_size);
        if (fs_va == NULL) {
                ipc_answer_0(callid, EHANGUP);
                return;
        }

        (void) ipc_share_out_finalize(callid, fs_va);

        while (1) {
                callid = async_get_call(&call);
                method = IPC_GET_METHOD(call);
                switch (method) {
                case IPC_M_PHONE_HUNGUP:
                        /* The other side has hung up. */
                        ipc_answer_0(callid, EOK);
                        return;
                case BD_READ_BLOCK:
                case BD_WRITE_BLOCK:
                        idx = IPC_GET_ARG1(call);
                        size = IPC_GET_ARG2(call);
                        if (size > comm_size) {
                                retval = EINVAL;
                                break;
                        }
                        if (method == BD_READ_BLOCK)
                                retval = file_bd_read(idx, size, fs_va);
                        else
                                retval = file_bd_write(idx, size, fs_va);
                        break;
                default:
                        retval = EINVAL;
                        break;
                }
                ipc_answer_0(callid, retval);
        }
}

static int file_bd_read(off_t blk_idx, off_t size, void *buf)
{
        size_t n_rd;

        printf("file_bd_read\n");
        futex_down(&dev_futex);

        printf("seek\n");
        fseek(img, blk_idx * size, SEEK_SET);
        printf("read\n");
        n_rd = fread(buf, 1, size, img);
        printf("done\n");

        printf("done\n");

        if (ferror(img)) {
                futex_up(&dev_futex);
                return EIO;     /* Read error */
        }

        futex_up(&dev_futex);

        if (n_rd < size) 
                return EINVAL;  /* Read beyond end of disk */

        return EOK;
}

static int file_bd_write(off_t blk_idx, off_t size, void *buf)
{
        size_t n_wr;

        futex_down(&dev_futex);

        fseek(img, blk_idx * size, SEEK_SET);
        n_wr = fread(buf, 1, size, img);

        if (ferror(img) || n_wr < size) {
                futex_up(&dev_futex);
                return EIO;     /* Write error */
        }

        futex_up(&dev_futex);

        return EOK;
}

/**
 * @}
 */