[PATCH] kbuild: check arch/$(SRCARCH)/include/generated before out-of-tree build

From: Masahiro Yamada
Date: Sun Apr 07 2019 - 06:44:43 EST


After cross-compiling the kernel, "make mrproper" should be executed
with the proper ARCH= option. Otherwise, stale objects will remain
under arch/$(SRCARCH)/.

One bad scenario is like this:

$ make ARCH=arm defconfig all # cross-compile the kernel for arm
$ make mrproper # mrproper for host-arch (i.e. x86)
$ make ARCH=arm O=build_dir defconfig all

If you miss ARCH= for mrproper and cross-compile the kernel with O=
and ARCH= options, Kbuild will happily start to build, but may fail
due to stale objects in the srctree.

If $(srctree)/arch/$(SRCARCH)/include/generated/ exists, let's stop
the out-of-tree build. To detect this, mrproper should clean only
arch/$(SRCARCH)/include/generated/.

Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---

Makefile | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 10643c3..17945ce 100644
--- a/Makefile
+++ b/Makefile
@@ -1091,7 +1091,9 @@ PHONY += prepare archprepare prepare1 prepare3
prepare3: include/config/kernel.release
ifneq ($(srctree),.)
@$(kecho) ' Using $(srctree) as source for kernel'
- $(Q)if [ -f $(srctree)/.config -o -d $(srctree)/include/config ]; then \
+ $(Q)if [ -f $(srctree)/.config -o \
+ -d $(srctree)/include/config -o \
+ -d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
echo >&2 " $(srctree) is not clean, please run 'make mrproper'"; \
echo >&2 " in the '$(srctree)' directory.";\
/bin/false; \
@@ -1350,7 +1352,7 @@ CLEAN_DIRS += $(MODVERDIR) include/ksym

# Directories & files removed with 'make mrproper'
MRPROPER_DIRS += include/config usr/include include/generated \
- arch/*/include/generated .tmp_objdiff
+ arch/$(SRCARCH)/include/generated .tmp_objdiff
MRPROPER_FILES += .config .config.old .version \
Module.symvers tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS \
signing_key.pem signing_key.priv signing_key.x509 \
--
2.7.4