1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * vpd_decode.c
4 *
5 * Google VPD decoding routines.
6 *
7 * Copyright 2017 Google Inc.
8 */
9
10#include "vpd_decode.h"
11
12static int vpd_decode_len(const u32 max_len, const u8 *in,
13 u32 *length, u32 *decoded_len)
14{
15 u8 more;
16 int i = 0;
17
18 if (!length || !decoded_len)
19 return VPD_FAIL;
20
21 *length = 0;
22 do {
23 if (i >= max_len)
24 return VPD_FAIL;
25
26 more = in[i] & 0x80;
27 *length <<= 7;
28 *length |= in[i] & 0x7f;
29 ++i;
30 } while (more);
31
32 *decoded_len = i;
33 return VPD_OK;
34}
35
36static int vpd_decode_entry(const u32 max_len, const u8 *input_buf,
37 u32 *_consumed, const u8 **entry, u32 *entry_len)
38{
39 u32 decoded_len;
40 u32 consumed = *_consumed;
41
42 if (vpd_decode_len(max_len: max_len - consumed, in: &input_buf[consumed],
43 length: entry_len, decoded_len: &decoded_len) != VPD_OK)
44 return VPD_FAIL;
45 if (max_len - consumed < decoded_len)
46 return VPD_FAIL;
47
48 consumed += decoded_len;
49 *entry = input_buf + consumed;
50
51 /* entry_len is untrusted data and must be checked again. */
52 if (max_len - consumed < *entry_len)
53 return VPD_FAIL;
54
55 consumed += *entry_len;
56 *_consumed = consumed;
57 return VPD_OK;
58}
59
60int vpd_decode_string(const u32 max_len, const u8 *input_buf, u32 *consumed,
61 vpd_decode_callback callback, void *callback_arg)
62{
63 int type;
64 u32 key_len;
65 u32 value_len;
66 const u8 *key;
67 const u8 *value;
68
69 /* type */
70 if (*consumed >= max_len)
71 return VPD_FAIL;
72
73 type = input_buf[*consumed];
74
75 switch (type) {
76 case VPD_TYPE_INFO:
77 case VPD_TYPE_STRING:
78 (*consumed)++;
79
80 if (vpd_decode_entry(max_len, input_buf, consumed: consumed, entry: &key,
81 entry_len: &key_len) != VPD_OK)
82 return VPD_FAIL;
83
84 if (vpd_decode_entry(max_len, input_buf, consumed: consumed, entry: &value,
85 entry_len: &value_len) != VPD_OK)
86 return VPD_FAIL;
87
88 if (type == VPD_TYPE_STRING)
89 return callback(key, key_len, value, value_len,
90 callback_arg);
91 break;
92
93 default:
94 return VPD_FAIL;
95 }
96
97 return VPD_OK;
98}
99

source code of linux/drivers/firmware/google/vpd_decode.c