Hi Masahiro, On 27.11.2017 13:15, Masahiro Yamada wrote: > Geert reported commit ae6b289a3789 ("kbuild: Set KBUILD_CFLAGS before > incl. arch Makefile") broke cross-compilation using a cross-compiler > that supports less compiler options than the host compiler. > > For example, > > cc1: error: unrecognized command line option "-Wno-unused-but-set-variable" > > This problem happens on architectures that setup CROSS_COMPILE in their > arch/*/Makefile. > > Move the cc-option and cc-disable-warning back to the original position, > but keep the Clang target options. This seems to break arm (32-bit) clang support for me. It seems to break correct compiler flag detection in some way. Just moving no-integrated-as back to before including the arch Makefile seems to fix the issue: --- a/Makefile +++ b/Makefile @@ -487,6 +487,7 @@ CLANG_GCC_TC := --gcc-toolchain=$(GCC_TOOLCHAIN) endif KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) +KBUILD_CFLAGS += $(call cc-option, -no-integrated-as) endif RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register @@ -744,7 +745,6 @@ KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare) # See modpost pattern 2 KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,) KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior) -KBUILD_CFLAGS += $(call cc-option, -no-integrated-as) KBUILD_AFLAGS += $(call cc-option, -no-integrated-as) else Does that sound like a reasonable fix? Note that arm support is not completely upstream yet, but only few patches are necessary currently: http://git.agner.ch/gitweb/?p=linux.git;a=shortlog;h=refs/heads/v4.16-rc5-clang-arm-no-revert -- Stefan > > Fixes: ae6b289a3789 ("kbuild: Set KBUILD_CFLAGS before incl. arch Makefile") > Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > Tested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > --- > > Makefile | 43 +++++++++++++++++++++++-------------------- > 1 file changed, 23 insertions(+), 20 deletions(-) > > diff --git a/Makefile b/Makefile > index aa67428..ac2d4e1 100644 > --- a/Makefile > +++ b/Makefile > @@ -484,26 +484,6 @@ CLANG_GCC_TC := --gcc-toolchain=$(GCC_TOOLCHAIN) > endif > KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) > KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) > -KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) > -KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable) > -KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) > -KBUILD_CFLAGS += $(call cc-disable-warning, gnu) > -KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) > -# Quiet clang warning: comparison of unsigned expression < 0 is always false > -KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare) > -# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the > -# source of a reference will be _MergedGlobals and not on of the > whitelisted names. > -# See modpost pattern 2 > -KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,) > -KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior) > -KBUILD_CFLAGS += $(call cc-option, -no-integrated-as) > -KBUILD_AFLAGS += $(call cc-option, -no-integrated-as) > -else > - > -# These warnings generated too much noise in a regular build. > -# Use make W=1 to enable them (see scripts/Makefile.extrawarn) > -KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) > -KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) > endif > > ifeq ($(config-targets),1) > @@ -715,6 +695,29 @@ ifdef CONFIG_CC_STACKPROTECTOR > endif > KBUILD_CFLAGS += $(stackp-flag) > > +ifeq ($(cc-name),clang) > +KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) > +KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable) > +KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) > +KBUILD_CFLAGS += $(call cc-disable-warning, gnu) > +KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) > +# Quiet clang warning: comparison of unsigned expression < 0 is always false > +KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare) > +# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the > +# source of a reference will be _MergedGlobals and not on of the > whitelisted names. > +# See modpost pattern 2 > +KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,) > +KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior) > +KBUILD_CFLAGS += $(call cc-option, -no-integrated-as) > +KBUILD_AFLAGS += $(call cc-option, -no-integrated-as) > +else > + > +# These warnings generated too much noise in a regular build. > +# Use make W=1 to enable them (see scripts/Makefile.extrawarn) > +KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) > +KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) > +endif > + > ifdef CONFIG_FRAME_POINTER > KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls > else -- 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