Copy the code from s390x

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/Kconfig        | 11 +++++++++++
 arch/powerpc/kexec/elf_64.c | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ac0c515552fd..ecc1227a77f1 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -561,6 +561,17 @@ config KEXEC_FILE
 config ARCH_HAS_KEXEC_PURGATORY
 	def_bool KEXEC_FILE

+config KEXEC_SIG
+	bool "Verify kernel signature during kexec_file_load() syscall"
+	depends on KEXEC_FILE && MODULE_SIG_FORMAT

After manually applying the patch, the build is failing with the following error:

build failed with error "arch/powerpc/kexec/elf_64.o: In function `elf64_verify_sig':
/root/kernel/linus/linux/arch/powerpc/kexec/elf_64.c:160: undefined reference to `verify_appended_signature'"

I see it happened because I didn't have MODULE_SIG enabled. Enabling MODULE_SIG fixes it.

I wonder why not to add "depends on MODULE_SIG" rather than on MODULE_SIG_FORMAT.

Thanks & Regards,

     - Nayna