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SubjectRe: [PATCH v2 4/4] arm64: vdso32: require CROSS_COMPILE_COMPAT for gcc+bfd
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On 10/20/21 12:36 AM, Nick Desaulniers wrote:
> Similar to
> commit 231ad7f409f1 ("Makefile: infer --target from ARCH for CC=clang")
> There really is no point in setting --target based on
> $CROSS_COMPILE_COMPAT for clang when the integrated assembler is being
> used, since
> commit ef94340583ee ("arm64: vdso32: drop -no-integrated-as flag").
>
> Allows COMPAT_VDSO to be selected without setting $CROSS_COMPILE_COMPAT
> when using clang and lld together.
>
> Before:
> $ ARCH=arm64 CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make -j72 LLVM=1 defconfig
> $ grep CONFIG_COMPAT_VDSO .config
> CONFIG_COMPAT_VDSO=y
> $ ARCH=arm64 make -j72 LLVM=1 defconfig
> $ grep CONFIG_COMPAT_VDSO .config
> $
>
> After:
> $ ARCH=arm64 CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make -j72 LLVM=1 defconfig
> $ grep CONFIG_COMPAT_VDSO .config
> CONFIG_COMPAT_VDSO=y
> $ ARCH=arm64 make -j72 LLVM=1 defconfig
> $ grep CONFIG_COMPAT_VDSO .config
> CONFIG_COMPAT_VDSO=y
>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Suggested-by: Nathan Chancellor <nathan@kernel.org>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> ---
> Changes v1 -> v2:
> * Cite ef94340583ee as per Nathan.
> * Add parens to Kconfig expression as per Nathan.
> * Pick up Nathan's RB, TB, and SB tags.
>
> arch/arm64/Kconfig | 3 ++-
> arch/arm64/kernel/vdso32/Makefile | 17 +++++------------
> 2 files changed, 7 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 5c7ae4c3954b..f0f2c95aa4c8 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1264,7 +1264,8 @@ config KUSER_HELPERS
>
> config COMPAT_VDSO
> bool "Enable vDSO for 32-bit applications"
> - depends on !CPU_BIG_ENDIAN && "$(CROSS_COMPILE_COMPAT)" != ""
> + depends on !CPU_BIG_ENDIAN
> + depends on (CC_IS_CLANG && LD_IS_LLD) || "$(CROSS_COMPILE_COMPAT)" != ""
> select GENERIC_COMPAT_VDSO
> default y
> help
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index e478cebb9891..c8fec493a450 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -10,18 +10,15 @@ include $(srctree)/lib/vdso/Makefile
>
> # Same as cc-*option, but using CC_COMPAT instead of CC
> ifeq ($(CONFIG_CC_IS_CLANG), y)
> -CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> -
> CC_COMPAT ?= $(CC)
> -CC_COMPAT += $(CC_COMPAT_CLANG_FLAGS)
> -
> -ifneq ($(LLVM),)
> -LD_COMPAT ?= $(LD)
> +CC_COMPAT += --target=arm-linux-gnueabi
> else
> -LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)ld
> +CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
> endif
> +
> +ifeq ($(CONFIG_LD_IS_LLD), y)
> +LD_COMPAT ?= $(LD)
> else
> -CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
> LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)ld
> endif
>
> @@ -45,10 +42,6 @@ VDSO_CPPFLAGS += $(LINUXINCLUDE)
> # Common C and assembly flags
> # From top-level Makefile
> VDSO_CAFLAGS := $(VDSO_CPPFLAGS)
> -ifneq ($(shell $(CC_COMPAT) --version 2>&1 | head -n 1 | grep clang),)
> -VDSO_CAFLAGS += --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> -endif
> -
> VDSO_CAFLAGS += $(call cc32-option,-fno-PIE)
> ifdef CONFIG_DEBUG_INFO
> VDSO_CAFLAGS += -g
>

--
Regards,
Vincenzo

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