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125 lines
3.3 KiB
C
125 lines
3.3 KiB
C
/*
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* MTD splitter for MikroTik NOR devices
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*
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* Copyright (C) 2017 Thibaut VARENE <varenet@parisc-linux.org>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*
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* The rootfs is expected at erase-block boundary due to the use of
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* mtd_find_rootfs_from(). We use a trimmed down version of the yaffs header
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* for two main reasons:
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* - the original header uses weakly defined types (int, enum...) which can
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* vary in length depending on build host (and the struct is not packed),
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* and the name field can have a different total length depending on
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* whether or not the yaffs code was _built_ with unicode support.
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* - the only field that could be of real use here (file_size_low) contains
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* invalid data in the header generated by kernel2minor, so we cannot use
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* it to infer the exact position of the rootfs and do away with
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* mtd_find_rootfs_from() (and thus have non-EB-aligned rootfs).
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/mtd/mtd.h>
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#include <linux/mtd/partitions.h>
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#include <linux/string.h>
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#include "mtdsplit.h"
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#define YAFFS_OBJECT_TYPE_FILE 0x1
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#define YAFFS_OBJECTID_ROOT 0x1
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#define YAFFS_SUM_UNUSED 0xFFFF
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#define YAFFS_NAME "kernel"
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#define MINOR_NR_PARTS 2
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/*
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* This structure is based on yaffs_obj_hdr from yaffs_guts.h
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* The weak types match upstream. The fields have cpu-endianness
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*/
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struct minor_header {
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int yaffs_type;
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int yaffs_obj_id;
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u16 yaffs_sum_unused;
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char yaffs_name[sizeof(YAFFS_NAME)];
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};
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static int mtdsplit_parse_minor(struct mtd_info *master,
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const struct mtd_partition **pparts,
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struct mtd_part_parser_data *data)
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{
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struct minor_header hdr;
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size_t hdr_len, retlen;
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size_t rootfs_offset;
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struct mtd_partition *parts;
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int err;
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hdr_len = sizeof(hdr);
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err = mtd_read(master, 0, hdr_len, &retlen, (void *) &hdr);
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if (err)
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return err;
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if (retlen != hdr_len)
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return -EIO;
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/* match header */
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if (hdr.yaffs_type != YAFFS_OBJECT_TYPE_FILE)
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return -EINVAL;
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if (hdr.yaffs_obj_id != YAFFS_OBJECTID_ROOT)
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return -EINVAL;
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if (hdr.yaffs_sum_unused != YAFFS_SUM_UNUSED)
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return -EINVAL;
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if (memcmp(hdr.yaffs_name, YAFFS_NAME, sizeof(YAFFS_NAME)))
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return -EINVAL;
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err = mtd_find_rootfs_from(master, master->erasesize, master->size,
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&rootfs_offset, NULL);
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if (err)
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return err;
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parts = kzalloc(MINOR_NR_PARTS * sizeof(*parts), GFP_KERNEL);
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if (!parts)
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return -ENOMEM;
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parts[0].name = KERNEL_PART_NAME;
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parts[0].offset = 0;
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parts[0].size = rootfs_offset;
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parts[1].name = ROOTFS_PART_NAME;
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parts[1].offset = rootfs_offset;
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parts[1].size = master->size - rootfs_offset;
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*pparts = parts;
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return MINOR_NR_PARTS;
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}
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static const struct of_device_id mtdsplit_minor_of_match_table[] = {
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{ .compatible = "mikrotik,minor" },
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{},
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};
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MODULE_DEVICE_TABLE(of, mtdsplit_minor_of_match_table);
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static struct mtd_part_parser mtdsplit_minor_parser = {
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.owner = THIS_MODULE,
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.name = "minor-fw",
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.of_match_table = mtdsplit_minor_of_match_table,
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.parse_fn = mtdsplit_parse_minor,
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.type = MTD_PARSER_TYPE_FIRMWARE,
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};
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static int __init mtdsplit_minor_init(void)
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{
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register_mtd_parser(&mtdsplit_minor_parser);
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return 0;
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}
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subsys_initcall(mtdsplit_minor_init);
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