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
22static 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
47int 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}