[PATCH] MIPS: VDSO: Use CLANG_FLAGS instead of filtering out '--target='

[PATCH] MIPS: VDSO: Use CLANG_FLAGS instead of filtering out '--target='

[Nathan Chancellor]

Commit ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO
cflags") allowed the '--target=' flag from the main Makefile to filter
through to the vDSO. However, it did not bring any of the other clang
specific flags for controlling the integrated assembler and the GNU
tools locations (--prefix=, --gcc-toolchain=, and -no-integrated-as).
Without these, we will get a warning (visible with tinyconfig):

arch/mips/vdso/elf.S:14:1: warning: DWARF2 only supports one section per
compilation unit
.pushsection .note.Linux, "a",@note ; .balign 4 ; .long 2f - 1f ; .long
4484f - 3f ; .long 0 ; 1:.asciz "Linux" ; 2:.balign 4 ; 3:
^
arch/mips/vdso/elf.S:34:2: warning: DWARF2 only supports one section per
compilation unit
 .section .mips_abiflags, "a"
 ^

All of these flags are bundled up under CLANG_FLAGS in the main Makefile
and exported so that they can be added to Makefiles that set their own
CFLAGS. Use this value instead of filtering out '--target=' so there is
no warning and all of the tools are properly used.

Cc: stable@vger.kernel.org
Fixes: ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO cflags")
Link: https://github.com/ClangBuiltLinux/linux/issues/1256
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 arch/mips/vdso/Makefile | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
index 5810cc12bc1d..2131d3fd7333 100644
--- a/arch/mips/vdso/Makefile
+++ b/arch/mips/vdso/Makefile
@@ -16,16 +16,13 @@ ccflags-vdso := \
 	$(filter -march=%,$(KBUILD_CFLAGS)) \
 	$(filter -m%-float,$(KBUILD_CFLAGS)) \
 	$(filter -mno-loongson-%,$(KBUILD_CFLAGS)) \
+	$(CLANG_FLAGS) \
 	-D__VDSO__
 
 ifndef CONFIG_64BIT
 ccflags-vdso += -DBUILD_VDSO32
 endif
 
-ifdef CONFIG_CC_IS_CLANG
-ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
-endif
-
 #
 # The -fno-jump-tables flag only prevents the compiler from generating
 # jump tables but does not prevent the compiler from emitting absolute

base-commit: 7b490a8ab0f2d3ab8d838a4ff22ae86edafd34a1
-- 
2.30.0

Re: [PATCH] MIPS: VDSO: Use CLANG_FLAGS instead of filtering out '--target='

[Anders Roxell]

On Fri, 15 Jan 2021 at 20:26, Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> Commit ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO
> cflags") allowed the '--target=' flag from the main Makefile to filter
> through to the vDSO. However, it did not bring any of the other clang
> specific flags for controlling the integrated assembler and the GNU
> tools locations (--prefix=, --gcc-toolchain=, and -no-integrated-as).
> Without these, we will get a warning (visible with tinyconfig):
>
> arch/mips/vdso/elf.S:14:1: warning: DWARF2 only supports one section per
> compilation unit
> .pushsection .note.Linux, "a",@note ; .balign 4 ; .long 2f - 1f ; .long
> 4484f - 3f ; .long 0 ; 1:.asciz "Linux" ; 2:.balign 4 ; 3:
> ^
> arch/mips/vdso/elf.S:34:2: warning: DWARF2 only supports one section per
> compilation unit
>  .section .mips_abiflags, "a"
>  ^
>
> All of these flags are bundled up under CLANG_FLAGS in the main Makefile
> and exported so that they can be added to Makefiles that set their own
> CFLAGS. Use this value instead of filtering out '--target=' so there is
> no warning and all of the tools are properly used.
>
> Cc: stable@vger.kernel.org
> Fixes: ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO cflags")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1256
> Reported-by: Anders Roxell <anders.roxell@linaro.org>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Tested-by: Anders Roxell <anders.roxell@linaro.org>

Cheers,
Anders

> ---
>  arch/mips/vdso/Makefile | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
> index 5810cc12bc1d..2131d3fd7333 100644
> --- a/arch/mips/vdso/Makefile
> +++ b/arch/mips/vdso/Makefile
> @@ -16,16 +16,13 @@ ccflags-vdso := \
>         $(filter -march=%,$(KBUILD_CFLAGS)) \
>         $(filter -m%-float,$(KBUILD_CFLAGS)) \
>         $(filter -mno-loongson-%,$(KBUILD_CFLAGS)) \
> +       $(CLANG_FLAGS) \
>         -D__VDSO__
>
>  ifndef CONFIG_64BIT
>  ccflags-vdso += -DBUILD_VDSO32
>  endif
>
> -ifdef CONFIG_CC_IS_CLANG
> -ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
> -endif
> -
>  #
>  # The -fno-jump-tables flag only prevents the compiler from generating
>  # jump tables but does not prevent the compiler from emitting absolute
>
> base-commit: 7b490a8ab0f2d3ab8d838a4ff22ae86edafd34a1
> --
> 2.30.0
>

Re: [PATCH] MIPS: VDSO: Use CLANG_FLAGS instead of filtering out '--target='

[Thomas Bogendoerfer]

On Fri, Jan 15, 2021 at 12:26:22PM -0700, Nathan Chancellor wrote:
> Commit ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO
> cflags") allowed the '--target=' flag from the main Makefile to filter
> through to the vDSO. However, it did not bring any of the other clang
> specific flags for controlling the integrated assembler and the GNU
> tools locations (--prefix=, --gcc-toolchain=, and -no-integrated-as).
> Without these, we will get a warning (visible with tinyconfig):
> 
> arch/mips/vdso/elf.S:14:1: warning: DWARF2 only supports one section per
> compilation unit
> .pushsection .note.Linux, "a",@note ; .balign 4 ; .long 2f - 1f ; .long
> 4484f - 3f ; .long 0 ; 1:.asciz "Linux" ; 2:.balign 4 ; 3:
> ^
> arch/mips/vdso/elf.S:34:2: warning: DWARF2 only supports one section per
> compilation unit
>  .section .mips_abiflags, "a"
>  ^
> 
> All of these flags are bundled up under CLANG_FLAGS in the main Makefile
> and exported so that they can be added to Makefiles that set their own
> CFLAGS. Use this value instead of filtering out '--target=' so there is
> no warning and all of the tools are properly used.
> 
> Cc: stable@vger.kernel.org
> Fixes: ee67855ecd9d ("MIPS: vdso: Allow clang's --target flag in VDSO cflags")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1256
> Reported-by: Anders Roxell <anders.roxell@linaro.org>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>  arch/mips/vdso/Makefile | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]