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/*
* Secure boot handling.
*
* Copyright (C) 2013,2014 Linaro Limited
* Roy Franz <roy.franz@linaro.org
* Copyright (C) 2013 Red Hat, Inc.
* Mark Salter <msalter@redhat.com>
*
* This file is part of the Linux kernel, and is made available under the
* terms of the GNU General Public License version 2.
*/
#include <linux/efi.h>
#include <asm/efi.h>
/* BIOS variables */
static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
static const efi_char16_t const efi_SecureBoot_name[] = {
'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0
};
static const efi_char16_t const efi_SetupMode_name[] = {
'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0
};
/* SHIM variables */
static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
static efi_char16_t const shim_MokSBState_name[] = {
'M', 'o', 'k', 'S', 'B', 'S', 't', 'a', 't', 'e', 0
};
#define get_efi_var(name, vendor, ...) \
efi_call_runtime(get_variable, \
(efi_char16_t *)(name), (efi_guid_t *)(vendor), \
__VA_ARGS__);
/*
* Determine whether we're in secure boot mode.
*/
enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg)
{
u32 attr;
u8 secboot, setupmode, moksbstate;
unsigned long size;
efi_status_t status;
size = sizeof(secboot);
status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
NULL, &size, &secboot);
if (status != EFI_SUCCESS)
goto out_efi_err;
size = sizeof(setupmode);
status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
NULL, &size, &setupmode);
if (status != EFI_SUCCESS)
goto out_efi_err;
if (secboot == 0 || setupmode == 1)
return efi_secureboot_mode_disabled;
/*
* See if a user has put the shim into insecure mode. If so, and if the
* variable doesn't have the runtime attribute set, we might as well
* honor that.
*/
size = sizeof(moksbstate);
status = get_efi_var(shim_MokSBState_name, &shim_guid,
&attr, &size, &moksbstate);
/* If it fails, we don't care why. Default to secure */
if (status != EFI_SUCCESS)
goto secure_boot_enabled;
if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1)
return efi_secureboot_mode_disabled;
secure_boot_enabled:
pr_efi(sys_table_arg, "UEFI Secure Boot is enabled.\n");
return efi_secureboot_mode_enabled;
out_efi_err:
pr_efi_err(sys_table_arg, "Could not determine UEFI Secure Boot status.\n");
if (status == EFI_NOT_FOUND)
return efi_secureboot_mode_disabled;
return efi_secureboot_mode_unknown;
}
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