Re: [PATCH v2 20/20] arm64: vdso32: Enable Clang Compilation

Vincenzo Frascino
2020-03-13T12:01:36Z

On 3/10/20 1:40 AM, Nathan Chancellor wrote:
> On Fri, Mar 06, 2020 at 01:32:42PM +0000, Vincenzo Frascino wrote:
>> Enable Clang Compilation for the vdso32 library.
>>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> ---
>> arch/arm64/kernel/vdso32/Makefile | 13 ++++++++++++-
>> 1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
>> index 04df57b43cb1..650cfc5757eb 100644
>> --- a/arch/arm64/kernel/vdso32/Makefile
>> +++ b/arch/arm64/kernel/vdso32/Makefile
>> @@ -10,7 +10,18 @@ include $(srctree)/lib/vdso/Makefile
>>
>> # Same as cc-*option, but using CC_COMPAT instead of CC
>> ifeq ($(CONFIG_CC_IS_CLANG), y)
>> -CC_COMPAT ?= $(CC)
>> +COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
>> +COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
>> +
>> +CLANG_CC_COMPAT := $(CC)
>> +CLANG_CC_COMPAT += --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
>> +CLANG_CC_COMPAT += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)
>> +CLANG_CC_COMPAT += -no-integrated-as -Qunused-arguments
>> +ifneq ($(COMPAT_GCC_TOOLCHAIN),)
>> +CLANG_CC_COMPAT += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
>> +endif
>> +
>> +CC_COMPAT ?= $(CLANG_CC_COMPAT)
>> else
>> CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
>> endif
>> --
>> 2.25.1
>>
> If CC_COMPAT is ever specified on the command line as clang (maybe by
> some unsuspecting user), we'd loose all of the above flags. Maybe it
> would be better to build a set of COMPAT_CLANG_FLAGS and append them to
> CC_COMPAT, maybe like below?
>

Fine by me.

> Regardless, the current approach works in my testing with clang 9.0.1
> and master (clang 11.0.0). This patch specifically is:
>

Good to hear. I will add your tags to the patch.

> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build
>
> ==================================================================================
>
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index 650cfc5757eb..df5145fab287 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -13,15 +13,16 @@ ifeq ($(CONFIG_CC_IS_CLANG), y)
> COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
> COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
>
> -CLANG_CC_COMPAT := $(CC)
> -CLANG_CC_COMPAT += --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> -CLANG_CC_COMPAT += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)
> -CLANG_CC_COMPAT += -no-integrated-as -Qunused-arguments
> +COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> +COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)
> +COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
> ifneq ($(COMPAT_GCC_TOOLCHAIN),)
> -CLANG_CC_COMPAT += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
> +COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
> endif
>
> -CC_COMPAT ?= $(CLANG_CC_COMPAT)
> +CC_COMPAT ?= $(CC)
> +CC_COMPAT += $(COMPAT_CLANG_FLAGS)
> +
> else
> CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
> endif
>

--
Regards,
Vincenzo