On Mon, Jul 29, 2019 at 6:16 PM Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> wrote:
>
> CLANG_FLAGS is initialized by the following line:
>
> CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
>
> ..., which is run only when CROSS_COMPILE is set.
>
> Some build targets (bindeb-pkg etc.) recurse to the top Makefile.
>
> When you build the kernel with Clang but without CROSS_COMPILE,
> the same compiler flags such as -no-integrated-as are accumulated
> into CLANG_FLAGS.
>
> If you run 'make CC=clang' and then 'make CC=clang bindeb-pkg',
> Kbuild will recompile everything needlessly due to the build command
> change.
>
> Fix this by correctly initializing CLANG_FLAGS.
>
> Fixes: 238bcbc4e07f ("kbuild: consolidate Clang compiler flags")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.20+
> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> ---
Applied to linux-kbuild.
>
> Makefile | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index fa0fbe7851ea..5ee6f6889869 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -472,6 +472,7 @@ KBUILD_CFLAGS_MODULE := -DMODULE
> KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
> KBUILD_LDFLAGS :=
> GCC_PLUGINS_CFLAGS :=
> +CLANG_FLAGS :=
>
> export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
> export CPP AR NM STRIP OBJCOPY OBJDUMP PAHOLE KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
> @@ -519,7 +520,7 @@ endif
>
> ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
> ifneq ($(CROSS_COMPILE),)
> -CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
> +CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
> GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
> CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)
> GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)
> --
> 2.17.1
>
--
Best Regards
Masahiro Yamada
