[Crash-utility] [PATCH v2 2/2] memory_driver: Support overriding kernel directory

[Mathias Krause]

Support compiling the module against a different kernel version than the
currently running one by allowing to set either KVER or KDIR variables
on the make commandline.

Also modernize the makefile slightly and make use of the kernel's
'clean' target to ensure to remove all generated files.

Signed-off-by: Mathias Krause <minipli at grsecurity.net>
---
v2:
- test kernel build directory existence first to avoid generating
  spurious error messages

 memory_driver/Makefile | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/memory_driver/Makefile b/memory_driver/Makefile
index b494aa3cd184..269a41cfc2ae 100644
--- a/memory_driver/Makefile
+++ b/memory_driver/Makefile
@@ -8,8 +8,13 @@
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
+ifneq ($(KERNELRELEASE),)
 obj-m := crash.o
+else
+KVER ?= $(shell uname -r)
+KDIR ?= /lib/modules/${KVER}/build
 all:
-	make -C /lib/modules/`uname -r`/build M=${PWD} SUBDIRS=${PWD} modules
+	${MAKE} -C ${KDIR} M=${PWD} SUBDIRS=${PWD} modules
 clean:
-	rm -f *.mod.c *.ko *.o Module.*
+	test -e ${KDIR}/Makefile && ${MAKE} -C ${KDIR} M=${PWD} SUBDIRS=${PWD} clean || ${RM} *.mod.c *.ko *.o Module.*
+endif
-- 
2.30.2