From: David Howells <dhowells@redhat.com>
Date: Wed, 8 Nov 2017 15:11:37 +0000
Subject: [28/29] efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=eb4a8603eb727afaeb9c6123eda2eda4b2757bf3

UEFI machines can be booted in Secure Boot mode.  Add an EFI_SECURE_BOOT
flag that can be passed to efi_enabled() to find out whether secure boot is
enabled.

Move the switch-statement in x86's setup_arch() that inteprets the
secure_boot boot parameter to generic code and set the bit there.

Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc: linux-efi@vger.kernel.org
---
 arch/x86/kernel/setup.c           | 14 +-------------
 drivers/firmware/efi/Makefile     |  1 +
 drivers/firmware/efi/secureboot.c | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/efi.h               | 16 ++++++++++------
 4 files changed, 50 insertions(+), 19 deletions(-)
 create mode 100644 drivers/firmware/efi/secureboot.c

Index: linux/arch/x86/kernel/setup.c
===================================================================
--- linux.orig/arch/x86/kernel/setup.c
+++ linux/arch/x86/kernel/setup.c
@@ -1159,19 +1159,7 @@ void __init setup_arch(char **cmdline_p)
 	/* Allocate bigger log buffer */
 	setup_log_buf(1);
 
-	if (efi_enabled(EFI_BOOT)) {
-		switch (boot_params.secure_boot) {
-		case efi_secureboot_mode_disabled:
-			pr_info("Secure boot disabled\n");
-			break;
-		case efi_secureboot_mode_enabled:
-			pr_info("Secure boot enabled\n");
-			break;
-		default:
-			pr_info("Secure boot could not be determined\n");
-			break;
-		}
-	}
+	efi_set_secure_boot(boot_params.secure_boot);
 
 	reserve_initrd();
 
Index: linux/drivers/firmware/efi/Makefile
===================================================================
--- linux.orig/drivers/firmware/efi/Makefile
+++ linux/drivers/firmware/efi/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_EFI_FAKE_MEMMAP)		+= fake_m
 obj-$(CONFIG_EFI_BOOTLOADER_CONTROL)	+= efibc.o
 obj-$(CONFIG_EFI_TEST)			+= test/
 obj-$(CONFIG_EFI_DEV_PATH_PARSER)	+= dev-path-parser.o
+obj-$(CONFIG_EFI)			+= secureboot.o
 obj-$(CONFIG_APPLE_PROPERTIES)		+= apple-properties.o
 
 arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o
Index: linux/drivers/firmware/efi/secureboot.c
===================================================================
--- /dev/null
+++ linux/drivers/firmware/efi/secureboot.c
@@ -0,0 +1,38 @@
+/* Core kernel secure boot support.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/efi.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+
+/*
+ * Decide what to do when UEFI secure boot mode is enabled.
+ */
+void __init efi_set_secure_boot(enum efi_secureboot_mode mode)
+{
+	if (efi_enabled(EFI_BOOT)) {
+		switch (mode) {
+		case efi_secureboot_mode_disabled:
+			pr_info("Secure boot disabled\n");
+			break;
+		case efi_secureboot_mode_enabled:
+			set_bit(EFI_SECURE_BOOT, &efi.flags);
+			pr_info("Secure boot enabled\n");
+			break;
+		default:
+			pr_warning("Secure boot could not be determined (mode %u)\n",
+				   mode);
+			break;
+		}
+	}
+}
Index: linux/include/linux/efi.h
===================================================================
--- linux.orig/include/linux/efi.h
+++ linux/include/linux/efi.h
@@ -1152,6 +1152,14 @@ extern int __init efi_setup_pcdp_console
 #define EFI_DBG			8	/* Print additional debug info at runtime */
 #define EFI_NX_PE_DATA		9	/* Can runtime data regions be mapped non-executable? */
 #define EFI_MEM_ATTR		10	/* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */
+#define EFI_SECURE_BOOT		11	/* Are we in Secure Boot mode? */
+
+enum efi_secureboot_mode {
+	efi_secureboot_mode_unset,
+	efi_secureboot_mode_unknown,
+	efi_secureboot_mode_disabled,
+	efi_secureboot_mode_enabled,
+};
 
 #ifdef CONFIG_EFI
 /*
@@ -1164,6 +1172,7 @@ static inline bool efi_enabled(int featu
 extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused);
 
 extern bool efi_is_table_address(unsigned long phys_addr);
+extern void __init efi_set_secure_boot(enum efi_secureboot_mode mode);
 #else
 static inline bool efi_enabled(int feature)
 {
@@ -1182,6 +1191,7 @@ static inline bool efi_is_table_address(
 {
 	return false;
 }
+static inline void efi_set_secure_boot(enum efi_secureboot_mode mode) {}
 #endif
 
 extern int efi_status_to_err(efi_status_t status);
@@ -1572,12 +1582,6 @@ static inline bool efi_runtime_disabled(
 
 extern void efi_call_virt_check_flags(unsigned long flags, const char *call);
 
-enum efi_secureboot_mode {
-	efi_secureboot_mode_unset,
-	efi_secureboot_mode_unknown,
-	efi_secureboot_mode_disabled,
-	efi_secureboot_mode_enabled,
-};
 enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table);
 
 #ifdef CONFIG_RESET_ATTACK_MITIGATION
