kernel: require backporting

Most kernel builders have to touch their kernel source code anyway so
we might as well tell them to backport things to achieve some sort
of feature parity.

path_umount:
	backslashxx/mojito_krenol@2d51422
get_cred_rcu:
	introduced by tiann#2320
	backport examples
	backslashxx/mojito_krenol@c1df3e5
	backslashxx/msm8953-kernel@95903fb

Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>

kernel/Makefile

@@ -56,11 +56,12 @@ $(info -- KernelSU Manager signature hash: $(KSU_EXPECTED_HASH))
 ccflags-y += -DEXPECTED_SIZE=$(KSU_EXPECTED_SIZE)
 ccflags-y += -DEXPECTED_HASH=\"$(KSU_EXPECTED_HASH)\"
 
-ifeq ($(shell grep -q "int path_umount" $(srctree)/fs/namespace.c; echo $$?),0)
-ccflags-y += -DKSU_UMOUNT
-else
-$(info -- Did you know you can backport path_umount to fs/namespace.c from 5.9?)
-$(info -- Read: https://kernelsu.org/guide/how-to-integrate-for-non-gki.html#how-to-backport-path-umount)
+ifneq ($(shell grep -q "int path_umount" $(srctree)/fs/namespace.c; echo $$?),0)
+$(error You must backport path_umount - https://github.com/tiann/KernelSU/pull/1464 )
+endif
+
+ifneq ($(shell grep -q "get_cred_rcu" $(srctree)/include/linux/cred.h; echo $$?),0)
+$(error You must backport get_cred_rcu - https://github.com/gregkh/linux/commit/97d0fb239c041f5f99655af74812c3ab75cc4346 )
 endif
 
 ccflags-y += -Wno-implicit-function-declaration -Wno-strict-prototypes -Wno-int-conversion -Wno-gcc-compat