Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1/*
2 * Secure boot handling.
3 *
4 * Copyright (C) 2013,2014 Linaro Limited
5 * Roy Franz <roy.franz@linaro.org
6 * Copyright (C) 2013 Red Hat, Inc.
7 * Mark Salter <msalter@redhat.com>
8 *
9 * This file is part of the Linux kernel, and is made available under the
10 * terms of the GNU General Public License version 2.
11 */
12#include <linux/efi.h>
13#include <asm/efi.h>
14
15#include "efistub.h"
16
17/* BIOS variables */
18static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
19static const efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
20static const efi_char16_t efi_SetupMode_name[] = L"SetupMode";
21
22/* SHIM variables */
23static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
24static const efi_char16_t shim_MokSBState_name[] = L"MokSBState";
25
26#define get_efi_var(name, vendor, ...) \
27 efi_call_runtime(get_variable, \
28 (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
29 __VA_ARGS__);
30
31/*
32 * Determine whether we're in secure boot mode.
33 */
34enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table_arg)
35{
36 u32 attr;
37 u8 secboot, setupmode, moksbstate;
38 unsigned long size;
39 efi_status_t status;
40
41 size = sizeof(secboot);
42 status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
43 NULL, &size, &secboot);
44 if (status == EFI_NOT_FOUND)
45 return efi_secureboot_mode_disabled;
46 if (status != EFI_SUCCESS)
47 goto out_efi_err;
48
49 size = sizeof(setupmode);
50 status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
51 NULL, &size, &setupmode);
52 if (status != EFI_SUCCESS)
53 goto out_efi_err;
54
55 if (secboot == 0 || setupmode == 1)
56 return efi_secureboot_mode_disabled;
57
58 /*
59 * See if a user has put the shim into insecure mode. If so, and if the
60 * variable doesn't have the runtime attribute set, we might as well
61 * honor that.
62 */
63 size = sizeof(moksbstate);
64 status = get_efi_var(shim_MokSBState_name, &shim_guid,
65 &attr, &size, &moksbstate);
66
67 /* If it fails, we don't care why. Default to secure */
68 if (status != EFI_SUCCESS)
69 goto secure_boot_enabled;
70 if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1)
71 return efi_secureboot_mode_disabled;
72
73secure_boot_enabled:
74 pr_efi(sys_table_arg, "UEFI Secure Boot is enabled.\n");
75 return efi_secureboot_mode_enabled;
76
77out_efi_err:
78 pr_efi_err(sys_table_arg, "Could not determine UEFI Secure Boot status.\n");
79 return efi_secureboot_mode_unknown;
80}