Hi Nick,
2017-11-16 5:42 GMT+09:00 Nick Desaulniers <ndesaulniers@xxxxxxxxxx>:
> From: Chris Fries <cfries@xxxxxxxxxx>
>
> Set the clang KBUILD_CFLAGS up before including arch/ Makefiles,
> so that ld-options (etc.) can work correctly.
>
> This fixes errors with clang such as ld-options trying to CC
> against your host architecture, but LD trying to link against
> your target architecture.
>
> Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> Signed-off-by: Chris Fries <cfries@xxxxxxxxxx>
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Suggested-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> ---
> Changes since v2:
> * Move clang block lower in Makefile, so as not to run it when running
> configuration, per Masahiro.
> * Remove paragraphs from commit message, per Masahiro.
> * Add Masahiro to Suggested-by line in commit message.
>
> Makefile | 64 ++++++++++++++++++++++++++++++++--------------------------------
> 1 file changed, 32 insertions(+), 32 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index a7476e6934f1..b3352becc7df 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -608,6 +608,38 @@ CFLAGS_GCOV := -fprofile-arcs -ftest-coverage -fno-tree-loop-im $(call cc-disabl
> CFLAGS_KCOV := $(call cc-option,-fsanitize-coverage=trace-pc,)
> export CFLAGS_GCOV CFLAGS_KCOV
>
> +ifeq ($(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
> +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
> +
> # The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default
> # values of the respective KBUILD_* variables
> ARCH_CPPFLAGS :=
> @@ -682,38 +714,6 @@ ifdef CONFIG_CC_STACKPROTECTOR
> endif
> KBUILD_CFLAGS += $(stackp-flag)
>
> -ifeq ($(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
> -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 += $(call cc-disable-warning, unused-const-variable)
> -endif
> -
> ifdef CONFIG_FRAME_POINTER
> KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
> else
> --
> 2.15.0.448.gf294e3d99a-goog
>
BTW, I notice another issue.
If we move clang settings before including arch Makefile,
"ifneq ($(CROSS_COMPILE),)" comes early.
Some arch Makefiles (arch/mips/Makefile, arch/blackfin/Makefile, etc.)
set CROSS_COMPILE there if CROSS_COMPILE is not given.
Then, we have a conflict between two requirements among arch.
[1] arm64, powerpc use ld-option in their Makefile.
So, clang flags must be set before inc. arch Makefile.
[2] mips, blackfin, etc. may set CROSS_COMPILE in their Makefile.
So, we want to reference CROSS_COMPILE only after inc. arch Makefile
I have no idea how to solve it.
At this moment, I guess clang is intended to support
only limited architectures.
It might be OK to be compromised here.
--
Best Regards
Masahiro Yamada
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