drivers/firmware/efi/libstub/smbios.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 // Copyright 2022 Google LLC
   3 // Author: Ard Biesheuvel <[email protected]>
   4
   5 #include <linux/efi.h>
   6
   7 #include "efistub.h"
   8
   9 typedef struct efi_smbios_protocol efi_smbios_protocol_t;
  10
  11 struct efi_smbios_protocol {
  12         efi_status_t (__efiapi *add)(efi_smbios_protocol_t *, efi_handle_t,
  13                                      u16 *, struct efi_smbios_record *);
  14         efi_status_t (__efiapi *update_string)(efi_smbios_protocol_t *, u16 *,
  15                                                unsigned long *, u8 *);
  16         efi_status_t (__efiapi *remove)(efi_smbios_protocol_t *, u16);
  17         efi_status_t (__efiapi *get_next)(efi_smbios_protocol_t *, u16 *, u8 *,
  18                                           struct efi_smbios_record **,
  19                                           efi_handle_t *);
  20
  21         u8 major_version;
  22         u8 minor_version;
  23 };
  24
  25 const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize)
  26 {
  27         struct efi_smbios_record *record;
  28         efi_smbios_protocol_t *smbios;
  29         efi_status_t status;
  30         u16 handle = 0xfffe;
  31         const u8 *strtable;
  32
  33         status = efi_bs_call(locate_protocol, &EFI_SMBIOS_PROTOCOL_GUID, NULL,
  34                              (void **)&smbios) ?:
  35                  efi_call_proto(smbios, get_next, &handle, &type, &record, NULL);
  36         if (status != EFI_SUCCESS)
  37                 return NULL;
  38
  39         strtable = (u8 *)record + recsize;
  40         for (int i = 1; i < ((u8 *)record)[offset]; i++) {
  41                 int len = strlen(strtable);
  42
  43                 if (!len)
  44                         return NULL;
  45                 strtable += len + 1;
  46         }
  47         return strtable;
  48 }