| 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 | } |
| 101 | |
