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_tag(u8 *buf, unsigned int buflen, u16 tag_id,
  34                     u8 **tag_data, u16 *tag_len)
  35 {
  36         uint32_t magic;
  37         int ret;
  38
  39         if (buflen < 4)
  40                 return -EINVAL;
  41
  42         magic = get_u32(buf);
  43         switch (magic) {
  44         case RB_MAGIC_HARD:
  45                 /* skip magic value */
  46                 buf += 4;
  47                 buflen -= 4;
  48                 break;
  49
  50         case RB_MAGIC_SOFT:
  51                 if (buflen < 8)
  52                         return -EINVAL;
  53
  54                 /* skip magic and CRC value */
  55                 buf += 8;
  56                 buflen -= 8;
  57
  58                 break;
  59
  60         default:
  61                 return -EINVAL;
  62         }
  63
  64         ret = -ENOENT;
  65         while (buflen > 2) {
  66                 u16 id;
  67                 u16 len;
  68
  69                 len = get_u16(buf);
  70                 buf += 2;
  71                 buflen -= 2;
  72
  73                 if (buflen < 2)
  74                         break;
  75
  76                 id = get_u16(buf);
  77                 buf += 2;
  78                 buflen -= 2;
  79
  80                 if (id == RB_ID_TERMINATOR)
  81                         break;
  82
  83                 if (buflen < len)
  84                         break;
  85
  86                 if (id == tag_id) {
  87                         if (tag_len)
  88                                 *tag_len = len;
  89                         if (tag_data)
  90                                 *tag_data = buf;
  91                         ret = 0;
  92                         break;
  93                 }
  94
  95                 buf += len;
  96                 buflen -= len;
  97         }
  98
  99         return ret;
 100 }