drivers/firmware/efi/libstub/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
   9 typedef union efi_smbios_protocol efi_smbios_protocol_t;
  10
  11 union 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
  36 const 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
  51 const 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 }