OpenWrt – Rev 4

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/*
 *  Copyright (C) 2012 John Crispin <blogic@openwrt.org>
 *  Copyright (C) 2015 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 2 as published
 *  by the Free Software Foundation.
 *
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/byteorder/generic.h>

#include "mtdsplit.h"

#define BRNIMAGE_NR_PARTS       2

#define BRNIMAGE_ALIGN_BYTES    0x400
#define BRNIMAGE_FOOTER_SIZE    12

#define BRNIMAGE_MIN_OVERHEAD   (BRNIMAGE_FOOTER_SIZE)
#define BRNIMAGE_MAX_OVERHEAD   (BRNIMAGE_ALIGN_BYTES + BRNIMAGE_FOOTER_SIZE)

static int mtdsplit_parse_brnimage(struct mtd_info *master,
                                const struct mtd_partition **pparts,
                                struct mtd_part_parser_data *data)
{
        struct mtd_partition *parts;
        uint32_t buf;
        unsigned long rootfs_offset, rootfs_size, kernel_size;
        size_t len;
        int ret = 0;

        for (rootfs_offset = 0; rootfs_offset < master->size;
             rootfs_offset += BRNIMAGE_ALIGN_BYTES) {
                ret = mtd_check_rootfs_magic(master, rootfs_offset, NULL);
                if (!ret)
                        break;
        }

        if (ret)
                return ret;

        if (rootfs_offset >= master->size)
                return -EINVAL;

        ret = mtd_read(master, rootfs_offset - BRNIMAGE_FOOTER_SIZE, 4, &len,
                        (void *)&buf);
        if (ret)
                return ret;

        if (len != 4)
                return -EIO;

        kernel_size = le32_to_cpu(buf);

        if (kernel_size > (rootfs_offset - BRNIMAGE_MIN_OVERHEAD))
                return -EINVAL;

        if (kernel_size < (rootfs_offset - BRNIMAGE_MAX_OVERHEAD))
                return -EINVAL;

        /*
         * The footer must be untouched as it contains the checksum of the
         * original brnImage (kernel + squashfs)!
         */
        rootfs_size = master->size - rootfs_offset - BRNIMAGE_FOOTER_SIZE;

        parts = kzalloc(BRNIMAGE_NR_PARTS * sizeof(*parts), GFP_KERNEL);
        if (!parts)
                return -ENOMEM;

        parts[0].name = KERNEL_PART_NAME;
        parts[0].offset = 0;
        parts[0].size = kernel_size;

        parts[1].name = ROOTFS_PART_NAME;
        parts[1].offset = rootfs_offset;
        parts[1].size = rootfs_size;

        *pparts = parts;
        return BRNIMAGE_NR_PARTS;
}

static struct mtd_part_parser mtdsplit_brnimage_parser = {
        .owner = THIS_MODULE,
        .name = "brnimage-fw",
        .parse_fn = mtdsplit_parse_brnimage,
        .type = MTD_PARSER_TYPE_FIRMWARE,
};

static int __init mtdsplit_brnimage_init(void)
{
        register_mtd_parser(&mtdsplit_brnimage_parser);

        return 0;
}

subsys_initcall(mtdsplit_brnimage_init);