target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit.c

   1 /*
   2  * Copyright (C) 2009-2013 Felix Fietkau <nbd@openwrt.org>
   3  * Copyright (C) 2009-2013 Gabor Juhos <juhosg@openwrt.org>
   4  * Copyright (C) 2012 Jonas Gorski <jogo@openwrt.org>
   5  * Copyright (C) 2013 Hauke Mehrtens <hauke@hauke-m.de>
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published
   9  * by the Free Software Foundation.
  10  *
  11  */
  12
  13 #define pr_fmt(fmt)     "mtdsplit: " fmt
  14
  15 #include <linux/export.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/magic.h>
  19 #include <linux/mtd/mtd.h>
  20 #include <linux/mtd/partitions.h>
  21 #include <linux/byteorder/generic.h>
  22
  23 #include "mtdsplit.h"
  24
  25 struct squashfs_super_block {
  26         __le32 s_magic;
  27         __le32 pad0[9];
  28         __le64 bytes_used;
  29 };
  30
  31 int mtd_get_squashfs_len(struct mtd_info *master,
  32                          size_t offset,
  33                          size_t *squashfs_len)
  34 {
  35         struct squashfs_super_block sb;
  36         size_t retlen;
  37         int err;
  38
  39         err = mtd_read(master, offset, sizeof(sb), &retlen, (void *)&sb);
  40         if (err || (retlen != sizeof(sb))) {
  41                 pr_alert("error occured while reading from \"%s\"\n",
  42                          master->name);
  43                 return -EIO;
  44         }
  45
  46         if (le32_to_cpu(sb.s_magic) != SQUASHFS_MAGIC) {
  47                 pr_alert("no squashfs found in \"%s\"\n", master->name);
  48                 return -EINVAL;
  49         }
  50
  51         retlen = le64_to_cpu(sb.bytes_used);
  52         if (retlen <= 0) {
  53                 pr_alert("squashfs is empty in \"%s\"\n", master->name);
  54                 return -ENODEV;
  55         }
  56
  57         if (offset + retlen > master->size) {
  58                 pr_alert("squashfs has invalid size in \"%s\"\n",
  59                          master->name);
  60                 return -EINVAL;
  61         }
  62
  63         *squashfs_len = retlen;
  64         return 0;
  65 }
  66 EXPORT_SYMBOL_GPL(mtd_get_squashfs_len);
  67
  68 static ssize_t mtd_next_eb(struct mtd_info *mtd, size_t offset)
  69 {
  70         return mtd_rounddown_to_eb(offset, mtd) + mtd->erasesize;
  71 }
  72
  73 int mtd_check_rootfs_magic(struct mtd_info *mtd, size_t offset)
  74 {
  75         u32 magic;
  76         size_t retlen;
  77         int ret;
  78
  79         ret = mtd_read(mtd, offset, sizeof(magic), &retlen,
  80                        (unsigned char *) &magic);
  81         if (ret)
  82                 return ret;
  83
  84         if (retlen != sizeof(magic))
  85                 return -EIO;
  86
  87         if (le32_to_cpu(magic) != SQUASHFS_MAGIC &&
  88             magic != 0x19852003)
  89                 return -EINVAL;
  90
  91         return 0;
  92 }
  93 EXPORT_SYMBOL_GPL(mtd_check_rootfs_magic);
  94
  95 int mtd_find_rootfs_from(struct mtd_info *mtd,
  96                          size_t from,
  97                          size_t limit,
  98                          size_t *ret_offset)
  99 {
 100         size_t offset;
 101         int err;
 102
 103         for (offset = from; offset < limit;
 104              offset = mtd_next_eb(mtd, offset)) {
 105                 err = mtd_check_rootfs_magic(mtd, offset);
 106                 if (err)
 107                         continue;
 108
 109                 *ret_offset = offset;
 110                 return 0;
 111         }
 112
 113         return -ENODEV;
 114 }
 115 EXPORT_SYMBOL_GPL(mtd_find_rootfs_from);
 116