[PATCH 1/5] efi: Move the x86 secure boot switch to generic code

[David Howells]

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

Suggested-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 arch/x86/kernel/setup.c           |   14 +-------------
 drivers/firmware/efi/Kconfig      |   23 +++++++++++++++++++++++
 drivers/firmware/efi/Makefile     |    1 +
 drivers/firmware/efi/secureboot.c |   34 ++++++++++++++++++++++++++++++++++
 include/linux/efi.h               |    6 ++++++
 5 files changed, 65 insertions(+), 13 deletions(-)
 create mode 100644 drivers/firmware/efi/secureboot.c

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0b4d3c686b1e..8bffbd8d2c1c 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1177,19 +1177,7 @@ 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();
 
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 394db40ed374..c40fdeaf9a45 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -84,6 +84,29 @@ config EFI_PARAMS_FROM_FDT
 config EFI_RUNTIME_WRAPPERS
 	bool
 
+config EFI_SECURE_BOOT
+	bool "Support UEFI Secure Boot and lock down the kernel in secure boot mode"
+	default n
+	help
+	  UEFI Secure Boot provides a mechanism for ensuring that the firmware
+	  will only load signed bootloaders and kernels.  Secure boot mode may
+	  be determined from EFI variables provided by the system firmware if
+	  not indicated by the boot parameters.
+
+	  Enabling this option turns on support for UEFI secure boot in the
+	  kernel.  This will result in various kernel facilities being locked
+	  away from userspace if the kernel detects that it has been booted in
+	  secure boot mode.  If it hasn't been booted in secure boot mode, or
+	  this cannot be determined, the lock down doesn't occur.
+
+	  The kernel facilities that get locked down include:
+	  - Viewing or changing the kernel's memory
+	  - Directly accessing ioports
+	  - Directly specifying ioports and other hardware parameters to drivers
+	  - Storing the kernel image unencrypted for hibernation
+	  - Loading unsigned modules
+	  - Kexec'ing unsigned images
+
 config EFI_ARMSTUB
 	bool
 
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 0329d319d89a..9dfd8530063f 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -23,6 +23,7 @@ obj-$(CONFIG_EFI_FAKE_MEMMAP)		+= fake_mem.o
 obj-$(CONFIG_EFI_BOOTLOADER_CONTROL)	+= efibc.o
 obj-$(CONFIG_EFI_TEST)			+= test/
 obj-$(CONFIG_EFI_DEV_PATH_PARSER)	+= dev-path-parser.o
+obj-$(CONFIG_EFI_SECURE_BOOT)		+= secureboot.o
 obj-$(CONFIG_APPLE_PROPERTIES)		+= apple-properties.o
 
 arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o
diff --git a/drivers/firmware/efi/secureboot.c b/drivers/firmware/efi/secureboot.c
new file mode 100644
index 000000000000..cf5bccae15e8
--- /dev/null
+++ b/drivers/firmware/efi/secureboot.c
@@ -0,0 +1,34 @@
+/* Core kernel secure boot support.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ *
+ * 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.
+ */
+
+#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:
+			pr_info("Secure boot enabled\n");
+			break;
+		default:
+			pr_info("Secure boot could not be determined\n");
+			break;
+		}
+	}
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 8269bcb8ccf7..e2f53edccf15 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1497,6 +1497,12 @@ enum efi_secureboot_mode {
 };
 enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table);
 
+#ifdef CONFIG_EFI_SECURE_BOOT
+void __init efi_set_secure_boot(enum efi_secureboot_mode mode);
+#else
+static inline void efi_set_secure_boot(enum efi_secureboot_mode mode) {}
+#endif
+
 /*
  * Arch code can implement the following three template macros, avoiding
  * reptition for the void/non-void return cases of {__,}efi_call_virt():