[PATCH v7 2/8] powerpc: add support to initialize ima policy rules

[Nayna Jain <nayna@xxxxxxxxxxxxx>]

PowerNV systems uses kernel based bootloader, thus its secure boot
implementation uses kernel IMA security subsystem to verify the kernel
before kexec. Since the verification policy might differ based on the
secure boot mode of the system, the policies are defined at runtime.

This patch implements the arch-specific support to define the IMA policy
rules based on the runtime secure boot mode of the system.

This patch provides arch-specific IMA policies if PPC_SECURE_BOOT
config is enabled.

Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
---
 arch/powerpc/Kconfig           |  2 ++
 arch/powerpc/kernel/Makefile   |  2 +-
 arch/powerpc/kernel/ima_arch.c | 33 +++++++++++++++++++++++++++++++++
 include/linux/ima.h            |  3 ++-
 4 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 arch/powerpc/kernel/ima_arch.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b4a221886fcf..deb19ec6ba3d 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -938,6 +938,8 @@ config PPC_SECURE_BOOT
 	prompt "Enable secure boot support"
 	bool
 	depends on PPC_POWERNV
+	depends on IMA
+	depends on IMA_ARCH_POLICY
 	help
 	  Systems with firmware secure boot enabled needs to define security
 	  policies to extend secure boot to the OS. This config allows user
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index e2a54fa240ac..e8eb2955b7d5 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -161,7 +161,7 @@ ifneq ($(CONFIG_PPC_POWERNV)$(CONFIG_PPC_SVM),)
 obj-y				+= ucall.o
 endif
 
-obj-$(CONFIG_PPC_SECURE_BOOT)	+= secure_boot.o
+obj-$(CONFIG_PPC_SECURE_BOOT)	+= secure_boot.o ima_arch.o
 
 # Disable GCOV, KCOV & sanitizers in odd or sensitive code
 GCOV_PROFILE_prom_init.o := n
diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
new file mode 100644
index 000000000000..c22d82965eb4
--- /dev/null
+++ b/arch/powerpc/kernel/ima_arch.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ */
+
+#include <linux/ima.h>
+#include <asm/secure_boot.h>
+
+bool arch_ima_get_secureboot(void)
+{
+	return is_powerpc_os_secureboot_enabled();
+}
+
+/* Defines IMA appraise rules for secureboot */
+static const char *const arch_rules[] = {
+	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
+#if !IS_ENABLED(CONFIG_MODULE_SIG_FORCE)
+	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
+#endif
+	NULL
+};
+
+/*
+ * Returns the relevant IMA arch policies based on the system secureboot state.
+ */
+const char *const *arch_get_ima_policy(void)
+{
+	if (is_powerpc_os_secureboot_enabled())
+		return arch_rules;
+
+	return NULL;
+}
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 1c37f17f7203..6d904754d858 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -29,7 +29,8 @@ 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)
+#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390) \
+	|| defined(CONFIG_PPC_SECURE_BOOT)
 extern bool arch_ima_get_secureboot(void);
 extern const char * const *arch_get_ima_policy(void);
 #else
-- 
2.20.1