1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 2020, Bachmann electronic GmbH
4 */
5
6 #include <common.h>
7 #include <smbios.h>
8
verify_checksum(const struct smbios_entry * e)9 static inline int verify_checksum(const struct smbios_entry *e)
10 {
11 /*
12 * Checksums for SMBIOS tables are calculated to have a value, so that
13 * the sum over all bytes yields zero (using unsigned 8 bit arithmetic).
14 */
15 u8 *byte = (u8 *)e;
16 u8 sum = 0;
17
18 for (int i = 0; i < e->length; i++)
19 sum += byte[i];
20
21 return sum;
22 }
23
smbios_entry(u64 address,u32 size)24 const struct smbios_entry *smbios_entry(u64 address, u32 size)
25 {
26 const struct smbios_entry *entry = (struct smbios_entry *)(uintptr_t)address;
27
28 if (!address | !size)
29 return NULL;
30
31 if (memcmp(entry->anchor, "_SM_", 4))
32 return NULL;
33
34 if (verify_checksum(entry))
35 return NULL;
36
37 return entry;
38 }
39
next_header(const struct smbios_header * curr)40 static const struct smbios_header *next_header(const struct smbios_header *curr)
41 {
42 u8 *pos = ((u8 *)curr) + curr->length;
43
44 /* search for _double_ NULL bytes */
45 while (!((*pos == 0) && (*(pos + 1) == 0)))
46 pos++;
47
48 /* step behind the double NULL bytes */
49 pos += 2;
50
51 return (struct smbios_header *)pos;
52 }
53
smbios_header(const struct smbios_entry * entry,int type)54 const struct smbios_header *smbios_header(const struct smbios_entry *entry, int type)
55 {
56 const unsigned int num_header = entry->struct_count;
57 const struct smbios_header *header = (struct smbios_header *)entry->struct_table_address;
58
59 for (unsigned int i = 0; i < num_header; i++) {
60 if (header->type == type)
61 return header;
62
63 header = next_header(header);
64 }
65
66 return NULL;
67 }
68
string_from_smbios_table(const struct smbios_header * header,int idx)69 static const char *string_from_smbios_table(const struct smbios_header *header,
70 int idx)
71 {
72 unsigned int i = 1;
73 u8 *pos;
74
75 if (!header)
76 return NULL;
77
78 pos = ((u8 *)header) + header->length;
79
80 while (i < idx) {
81 if (*pos == 0x0)
82 i++;
83
84 pos++;
85 }
86
87 return (const char *)pos;
88 }
89
smbios_string(const struct smbios_header * header,int index)90 const char *smbios_string(const struct smbios_header *header, int index)
91 {
92 if (!header)
93 return NULL;
94
95 return string_from_smbios_table(header, index);
96 }
97