ima: add a new CONFIG for loading arch-specific policies

Every time a new architecture defines the IMA architecture specific
functions - arch_ima_get_secureboot() and arch_ima_get_policy(), the IMA
include file needs to be updated. To avoid this "noise", this patch
defines a new IMA Kconfig IMA_SECURE_AND_OR_TRUSTED_BOOT option, allowing
the different architectures to select it.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Philipp Rudo <prudo@linux.ibm.com> (s390)
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

arch/powerpc/Kconfig

@@ -979,6 +979,7 @@ config PPC_SECURE_BOOT
 	bool
 	depends on PPC_POWERNV
 	depends on IMA_ARCH_POLICY
+	imply IMA_SECURE_AND_OR_TRUSTED_BOOT
 	help
 	  Systems with firmware secure boot enabled need to define security
 	  policies to extend secure boot to the OS. This config allows a user

arch/s390/Kconfig

@@ -195,6 +195,7 @@ config S390
 	select ARCH_HAS_FORCE_DMA_UNENCRYPTED
 	select SWIOTLB
 	select GENERIC_ALLOCATOR
+	imply IMA_SECURE_AND_OR_TRUSTED_BOOT
 
 
 config SCHED_OMIT_FRAME_POINTER

arch/s390/kernel/Makefile

@@ -70,7 +70,7 @@ obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_image.o
 obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o
 
-obj-$(CONFIG_IMA)		+= ima_arch.o
+obj-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT)	+= ima_arch.o
 
 obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_cpum_cf_common.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_cpum_cf.o perf_cpum_sf.o

arch/x86/Kconfig

@@ -230,6 +230,7 @@ config X86
 	select VIRT_TO_BUS
 	select X86_FEATURE_NAMES		if PROC_FS
 	select PROC_PID_ARCH_STATUS		if PROC_FS
+	imply IMA_SECURE_AND_OR_TRUSTED_BOOT    if EFI
 
 config INSTRUCTION_DECODER
 	def_bool y

arch/x86/kernel/Makefile

@@ -154,6 +154,4 @@ ifeq ($(CONFIG_X86_64),y)
 	obj-y				+= vsmp_64.o
 endif
 
-ifdef CONFIG_EFI
+obj-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT)	+= ima_arch.o
-obj-$(CONFIG_IMA)			+= ima_arch.o
-endif

include/linux/ima.h

@@ -30,8 +30,7 @@ extern void ima_kexec_cmdline(const void *buf, int size);
 extern void ima_add_kexec_buffer(struct kimage *image);
 #endif
 
-#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390) \
+#ifdef CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT
-	|| defined(CONFIG_PPC_SECURE_BOOT)
 extern bool arch_ima_get_secureboot(void);
 extern const char * const *arch_get_ima_policy(void);
 #else

security/integrity/ima/Kconfig

@@ -327,3 +327,10 @@ config IMA_QUEUE_EARLY_BOOT_KEYS
 	depends on IMA_MEASURE_ASYMMETRIC_KEYS
 	depends on SYSTEM_TRUSTED_KEYRING
 	default y
+
+config IMA_SECURE_AND_OR_TRUSTED_BOOT
+       bool
+       depends on IMA_ARCH_POLICY
+       help
+          This option is selected by architectures to enable secure and/or
+          trusted boot based on IMA runtime policies.