1 /*
2  * vpd_decode.c
3  *
4  * Google VPD decoding routines.
5  *
6  * Copyright 2017 Google Inc.
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License v2.0 as published by
10  * the Free Software Foundation.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  */
17 
18 #include <linux/export.h>
19 
20 #include "vpd_decode.h"
21 
22 static int vpd_decode_len(const s32 max_len, const u8 *in,
23 			  s32 *length, s32 *decoded_len)
24 {
25 	u8 more;
26 	int i = 0;
27 
28 	if (!length || !decoded_len)
29 		return VPD_FAIL;
30 
31 	*length = 0;
32 	do {
33 		if (i >= max_len)
34 			return VPD_FAIL;
35 
36 		more = in[i] & 0x80;
37 		*length <<= 7;
38 		*length |= in[i] & 0x7f;
39 		++i;
40 	} while (more);
41 
42 	*decoded_len = i;
43 
44 	return VPD_OK;
45 }
46 
47 int vpd_decode_string(const s32 max_len, const u8 *input_buf, s32 *consumed,
48 		      vpd_decode_callback callback, void *callback_arg)
49 {
50 	int type;
51 	int res;
52 	s32 key_len;
53 	s32 value_len;
54 	s32 decoded_len;
55 	const u8 *key;
56 	const u8 *value;
57 
58 	/* type */
59 	if (*consumed >= max_len)
60 		return VPD_FAIL;
61 
62 	type = input_buf[*consumed];
63 
64 	switch (type) {
65 	case VPD_TYPE_INFO:
66 	case VPD_TYPE_STRING:
67 		(*consumed)++;
68 
69 		/* key */
70 		res = vpd_decode_len(max_len - *consumed, &input_buf[*consumed],
71 				     &key_len, &decoded_len);
72 		if (res != VPD_OK || *consumed + decoded_len >= max_len)
73 			return VPD_FAIL;
74 
75 		*consumed += decoded_len;
76 		key = &input_buf[*consumed];
77 		*consumed += key_len;
78 
79 		/* value */
80 		res = vpd_decode_len(max_len - *consumed, &input_buf[*consumed],
81 				     &value_len, &decoded_len);
82 		if (res != VPD_OK || *consumed + decoded_len > max_len)
83 			return VPD_FAIL;
84 
85 		*consumed += decoded_len;
86 		value = &input_buf[*consumed];
87 		*consumed += value_len;
88 
89 		if (type == VPD_TYPE_STRING)
90 			return callback(key, key_len, value, value_len,
91 					callback_arg);
92 		break;
93 
94 	default:
95 		return VPD_FAIL;
96 	}
97 
98 	return VPD_OK;
99 }
100