target/linux/ar71xx/files/arch/mips/ath79/routerboot.c

   1 /*
   2  *  RouterBoot helper routines
   3  *
   4  *  Copyright (C) 2012 Gabor Juhos <juhosg@openwrt.org>
   5  *
   6  *  This program is free software; you can redistribute it and/or modify it
   7  *  under the terms of the GNU General Public License version 2 as published
   8  *  by the Free Software Foundation.
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/routerboot.h>
  14
  15 #include "routerboot.h"
  16
  17 static u32 get_u32(void *buf)
  18 {
  19         u8 *p = buf;
  20
  21         return ((u32) p[3] + ((u32) p[2] << 8) + ((u32) p[1] << 16) +
  22                ((u32) p[0] << 24));
  23 }
  24
  25 static u16 get_u16(void *buf)
  26 {
  27         u8 *p = buf;
  28
  29         return (u16) p[1] + ((u16) p[0] << 8);
  30 }
  31
  32 __init int
  33 routerboot_find_magic(u8 *buf, unsigned int buflen, u32 *offset, bool hard)
  34 {
  35         u32 magic_ref = hard ? RB_MAGIC_HARD : RB_MAGIC_SOFT;
  36         u32 magic;
  37         u32 cur = *offset;
  38
  39         while (cur < buflen) {
  40                 magic = get_u32(buf + cur);
  41                 if (magic == magic_ref) {
  42                         *offset = cur;
  43                         return 0;
  44                 }
  45
  46                 cur += 0x1000;
  47         }
  48
  49         return -ENOENT;
  50 }
  51
  52 __init int
  53 routerboot_find_tag(u8 *buf, unsigned int buflen, u16 tag_id,
  54                     u8 **tag_data, u16 *tag_len)
  55 {
  56         uint32_t magic;
  57         int ret;
  58
  59         if (buflen < 4)
  60                 return -EINVAL;
  61
  62         magic = get_u32(buf);
  63         switch (magic) {
  64         case RB_MAGIC_HARD:
  65                 /* skip magic value */
  66                 buf += 4;
  67                 buflen -= 4;
  68                 break;
  69
  70         case RB_MAGIC_SOFT:
  71                 if (buflen < 8)
  72                         return -EINVAL;
  73
  74                 /* skip magic and CRC value */
  75                 buf += 8;
  76                 buflen -= 8;
  77
  78                 break;
  79
  80         default:
  81                 return -EINVAL;
  82         }
  83
  84         ret = -ENOENT;
  85         while (buflen > 2) {
  86                 u16 id;
  87                 u16 len;
  88
  89                 len = get_u16(buf);
  90                 buf += 2;
  91                 buflen -= 2;
  92
  93                 if (buflen < 2)
  94                         break;
  95
  96                 id = get_u16(buf);
  97                 buf += 2;
  98                 buflen -= 2;
  99
 100                 if (id == RB_ID_TERMINATOR)
 101                         break;
 102
 103                 if (buflen < len)
 104                         break;
 105
 106                 if (id == tag_id) {
 107                         if (tag_len)
 108                                 *tag_len = len;
 109                         if (tag_data)
 110                                 *tag_data = buf;
 111                         ret = 0;
 112                         break;
 113                 }
 114
 115                 buf += len;
 116                 buflen -= len;
 117         }
 118
 119         return ret;
 120 }