On Tue, Apr 13, 2021 at 3:27 PM Yonghong Song <yhs@xxxxxx> wrote: > > > > On 4/13/21 3:13 PM, Nick Desaulniers wrote: > > On Tue, Apr 13, 2021 at 3:05 PM Andrii Nakryiko > > <andrii.nakryiko@xxxxxxxxx> wrote: > >> > >> On Tue, Apr 13, 2021 at 8:34 AM Yonghong Song <yhs@xxxxxx> wrote: > >>> > >>> selftests/bpf/Makefile includes lib.mk. With the following command > >>> make -j60 LLVM=1 LLVM_IAS=1 <=== compile kernel > >>> make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1 V=1 > >>> some files are still compiled with gcc. This patch > >>> fixed lib.mk issue which sets CC to gcc in all cases. > >>> > >>> Cc: Sedat Dilek <sedat.dilek@xxxxxxxxx> > >>> Signed-off-by: Yonghong Song <yhs@xxxxxx> > >>> --- > >>> tools/testing/selftests/lib.mk | 4 ++++ > >>> 1 file changed, 4 insertions(+) > >>> > >>> diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk > >>> index a5ce26d548e4..9a41d8bb9ff1 100644 > >>> --- a/tools/testing/selftests/lib.mk > >>> +++ b/tools/testing/selftests/lib.mk > >>> @@ -1,6 +1,10 @@ > >>> # This mimics the top-level Makefile. We do it explicitly here so that this > >>> # Makefile can operate with or without the kbuild infrastructure. > >>> +ifneq ($(LLVM),) > >>> +CC := clang > >> > >> Does this mean that cross-compilation with Clang doesn't work at all > >> or is achieved in some other way? > > > > Right, this probably doesn't support cross compilation w/ Clang. > > Rather than invoke `$(CROSS_COMPILE) clang`, you'd do `clang > > --target=$(CROSS_COMPILE)`. Even then, cross linking executables is > > hairy. But at least this should enable native compilation, which is a > > start. > > See https://clang.llvm.org/docs/CrossCompilation.html. > As Nick said, clang prefers --target=$(CROSS_COMPILE) to > indicate cross compilation. User can pass additional > flags (CFLAGS) for cross compilation for the time being. > This is the same as main kernel Makefile. > > ifneq ($(LLVM),) > CC = clang > LD = ld.lld > AR = llvm-ar > NM = llvm-nm > OBJCOPY = llvm-objcopy > OBJDUMP = llvm-objdump > READELF = llvm-readelf > STRIP = llvm-strip > else > CC = $(CROSS_COMPILE)gcc > LD = $(CROSS_COMPILE)ld > AR = $(CROSS_COMPILE)ar > NM = $(CROSS_COMPILE)nm > OBJCOPY = $(CROSS_COMPILE)objcopy > OBJDUMP = $(CROSS_COMPILE)objdump > READELF = $(CROSS_COMPILE)readelf > STRIP = $(CROSS_COMPILE)strip > endif Right, then later in the top level Makefile to achieve cross compilation support 569 ifneq ($(CROSS_COMPILE),) 570 CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) ... The top level Makefile has this all wired up correctly; I wonder if tools/ could make use of the existing exports, rather than redoing all of that work? > > >> > >> > >>> +else > >>> CC := $(CROSS_COMPILE)gcc > >>> +endif > >>> > >>> ifeq (0,$(MAKELEVEL)) > >>> ifeq ($(OUTPUT),) > >>> -- > >>> 2.30.2 > >>> > > > > > > -- Thanks, ~Nick Desaulniers
