smbios.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2// Copyright 2022 Google LLC
 3// Author: Ard Biesheuvel <ardb@google.com>
 4
 5#include <linux/efi.h>
 6
 7#include "efistub.h"
 8
 9typedef union efi_smbios_protocol efi_smbios_protocol_t;
10
11union efi_smbios_protocol {
12	struct {
13		efi_status_t (__efiapi *add)(efi_smbios_protocol_t *, efi_handle_t,
14					     u16 *, struct efi_smbios_record *);
15		efi_status_t (__efiapi *update_string)(efi_smbios_protocol_t *, u16 *,
16						       unsigned long *, u8 *);
17		efi_status_t (__efiapi *remove)(efi_smbios_protocol_t *, u16);
18		efi_status_t (__efiapi *get_next)(efi_smbios_protocol_t *, u16 *, u8 *,
19						  struct efi_smbios_record **,
20						  efi_handle_t *);
21
22		u8 major_version;
23		u8 minor_version;
24	};
25	struct {
26		u32 add;
27		u32 update_string;
28		u32 remove;
29		u32 get_next;
30
31		u8 major_version;
32		u8 minor_version;
33	} mixed_mode;
34};
35
36const struct efi_smbios_record *efi_get_smbios_record(u8 type)
37{
38	struct efi_smbios_record *record;
39	efi_smbios_protocol_t *smbios;
40	efi_status_t status;
41	u16 handle = 0xfffe;
42
43	status = efi_bs_call(locate_protocol, &EFI_SMBIOS_PROTOCOL_GUID, NULL,
44			     (void **)&smbios) ?:
45		 efi_call_proto(smbios, get_next, &handle, &type, &record, NULL);
46	if (status != EFI_SUCCESS)
47		return NULL;
48	return record;
49}
50
51const u8 *__efi_get_smbios_string(const struct efi_smbios_record *record,
52				  const u8 *offset)
53{
54	const u8 *strtable;
55
56	if (!record)
57		return NULL;
58
59	strtable = (u8 *)record + record->length;
60	for (int i = 1; i < *offset; i++) {
61		int len = strlen(strtable);
62
63		if (!len)
64			return NULL;
65		strtable += len + 1;
66	}
67	return strtable;
68}