linux-kernel - Re: [PATCH] arch/x86: Propagate $(CLANG_FLAGS) to $(REALMODE

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Message-ID: <37DE7046-5096-4C0C-A96D-FD168A849DFD@zytor.com>
Date:   Fri, 25 Dec 2020 23:35:28 -0800
From:   hpa@...or.com
To:     John Millikin <jmillikin@...il.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
CC:     clang-built-linux@...glegroups.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        John Millikin <john@...n-millikin.com>
Subject: Re: [PATCH] arch/x86: Propagate $(CLANG_FLAGS) to $(REALMODE_FLAGS)

On December 25, 2020 11:29:30 PM PST, John Millikin <jmillikin@...il.com> wrote:
>When compiling with Clang, the `$(CLANG_FLAGS)' variable contains
>additional flags needed to cross-compile C and Assembly sources:
>
>* `-no-integrated-as' tells clang to assemble with GNU Assembler
>  instead of its built-in LLVM assembler. This flag is set by default
>  unless `LLVM_IAS=1' is set, because the LLVM assembler can't yet
>  parse certain GNU extensions.
>
>* `--target' sets the target architecture when cross-compiling. This
>  flag must be set for both compilation and assembly (`KBUILD_AFLAGS')
>  to support architecture-specific assembler directives.
>
>Signed-off-by: John Millikin <john@...n-millikin.com>
>---
> arch/x86/Makefile | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>index 7116da3980be..725c65532482 100644
>--- a/arch/x86/Makefile
>+++ b/arch/x86/Makefile
>@@ -33,6 +33,11 @@ REALMODE_CFLAGS += -ffreestanding
> REALMODE_CFLAGS += -fno-stack-protector
> REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS),
>-Wno-address-of-packed-member)
> REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS),
>$(cc_stack_align4))
>+
>+ifdef CONFIG_CC_IS_CLANG
>+REALMODE_CFLAGS += $(CLANG_FLAGS)
>+endif
>+
> export REALMODE_CFLAGS
> 
> # BITS is used as extension for files which are available in a 32 bit

Why is CLANG_FLAGS non-null when unused? It would be better to centralize that.
-- 
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