1 files changed, 76 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
new file mode 100644
index 000000000..a2be3a71b
--- /dev/null
+++ b/drivers/firmware/efi/libstub/secureboot.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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>
+ */
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+#include "efistub.h"
+
+/* BIOS variables */
+static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
+static const efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
+static const efi_char16_t efi_SetupMode_name[] = L"SetupMode";
+
+/* SHIM variables */
+static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
+static const efi_char16_t shim_MokSBState_name[] = L"MokSBStateRT";
+
+/*
+ * Determine whether we're in secure boot mode.
+ *
+ * Please keep the logic in sync with
+ * arch/x86/xen/efi.c:xen_efi_get_secureboot().
+ */
+enum efi_secureboot_mode efi_get_secureboot(void)
+{
+	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_NOT_FOUND)
+		return efi_secureboot_mode_disabled;
+	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 non-volatile 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_NON_VOLATILE) && moksbstate == 1)
+		return efi_secureboot_mode_disabled;
+
+secure_boot_enabled:
+	efi_info("UEFI Secure Boot is enabled.\n");
+	return efi_secureboot_mode_enabled;
+
+out_efi_err:
+	efi_err("Could not determine UEFI Secure Boot status.\n");
+	return efi_secureboot_mode_unknown;
+}