s390/kexec_file: Disable kexec_load when IPLed secure

A kernel loaded via kexec_load cannot be verified. Thus disable kexec_load
systemcall in kernels which where IPLed securely. Use the IMA mechanism to
do so.
Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/Makefile

@@ -77,6 +77,8 @@ 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_PERF_EVENTS)	+= perf_event.o perf_cpum_cf_common.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_cpum_cf.o perf_cpum_sf.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_cpum_cf_events.o perf_regs.o

arch/s390/kernel/ima_arch.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/ima.h>
+#include <asm/boot_data.h>
+
+bool arch_ima_get_secureboot(void)
+{
+	return ipl_secure_flag;
+}
+
+const char * const *arch_get_ima_policy(void)
+{
+	return NULL;
+}

include/linux/ima.h

@@ -31,7 +31,7 @@ extern void ima_post_path_mknod(struct dentry *dentry);
 extern void ima_add_kexec_buffer(struct kimage *image);
 #endif
 
-#if defined(CONFIG_X86) && defined(CONFIG_EFI)
+#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390)
 extern bool arch_ima_get_secureboot(void);
 extern const char * const *arch_get_ima_policy(void);
 #else