Hi Matthias, 2017-04-11 6:09 GMT+09:00 Matthias Kaehlcke <mka@xxxxxxxxxxxx>: > COMPILER is previously set to "clang" if CC=clang was set from the > make command line. So -target and -gcc-toolchain can be added to CC, > since we already know that it is set. Can you reword or delete this paragraph? I think this is confusing because COMPILER was replaced with cc-name by commit 5631d9c4. > Clang will fallback to using things like ld, as, and libgcc if > (respectively) one of the llvm linkers isn't available, the integrated > assembler is turned off, or an appropriately cross-compiled version of > compiler-rt isn't available. To this end, you can specify the path to > this fallback gcc toolchain with GCC_TOOLCHAIN. > > From: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx> > Reviewed-by: Jan-Simon Möller <dl9pf@xxxxxx> > Reviewed-by: Mark Charlebois <charlebm@xxxxxxxxx> > Signed-off-by: Greg Hackmann <ghackmann@xxxxxxxxxx> > Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> > --- > Changes in v2: > - Fix GCC_TOOLCHAIN definition. $(LD) is needed to link the kernel, use > its path to determine the installation prefix of the toolchain. > (From: Greg Hackmann <ghackmann@xxxxxxxxxx>) > > Makefile | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/Makefile b/Makefile > index e11989d36c87..d3a02786bb53 100644 > --- a/Makefile > +++ b/Makefile > @@ -375,6 +375,16 @@ LDFLAGS_vmlinux = > CFLAGS_GCOV = -fprofile-arcs -ftest-coverage -fno-tree-loop-im -Wno-maybe-uninitialized > CFLAGS_KCOV := $(call cc-option,-fsanitize-coverage=trace-pc,) > > +ifeq ($(cc-name),clang) > +ifneq ($(CROSS_COMPILE),) > +CLANG_TARGET := -target $(notdir $(CROSS_COMPILE:%-=%)) > +GCC_TOOLCHAIN := $(realpath $(dir $(shell which $(LD)))/..) > +endif > +ifneq ($(GCC_TOOLCHAIN),) > +CLANG_GCC_TC := -gcc-toolchain $(GCC_TOOLCHAIN) > +endif > +CLANG_FLAGS := $(CLANG_TARGET) $(CLANG_GCC_TC) > +endif > > # Use USERINCLUDE when you must reference the UAPI directories only. > USERINCLUDE := \ > @@ -395,18 +405,18 @@ LINUXINCLUDE := \ > > LINUXINCLUDE += $(filter-out $(LINUXINCLUDE),$(USERINCLUDE)) > > -KBUILD_CPPFLAGS := -D__KERNEL__ > +KBUILD_CPPFLAGS := -D__KERNEL__ $(CLANG_FLAGS) > > KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \ > -fno-strict-aliasing -fno-common \ > -Werror-implicit-function-declaration \ > -Wno-format-security \ > - -std=gnu89 $(call cc-option,-fno-PIE) > - > + -std=gnu89 $(call cc-option,-fno-PIE) \ > + $(CLANG_FLAGS) > > KBUILD_AFLAGS_KERNEL := > KBUILD_CFLAGS_KERNEL := > -KBUILD_AFLAGS := -D__ASSEMBLY__ $(call cc-option,-fno-PIE) > +KBUILD_AFLAGS := -D__ASSEMBLY__ $(call cc-option,-fno-PIE) $(CLANG_FLAGS) This adds multiple -gcc-toolchain because both KBUILD_CPPFLAGS and KBUILD_CFLAGS are added to c_flags. See scripts/Makefile.lib orig_c_flags = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(KBUILD_SUBDIR_CCFLAGS) \ $(ccflags-y) $(CFLAGS_$(basetarget).o) Pre-processing is related to the front-end part, so -target and -gcc-toolchain are not necessary for KBUILD_CPPFLAGS? Maybe, adding it to KBUILD_CFLAGS and KBUILD_AFLAGS could be enough? Is it possible to move these to around line 700? ifeq ($(cc-name),clang) < add here ? > KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,) I do not want to sprinkle ugly ifeq ($(cc-name,clang). -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html