linux-kernel - Re: [PATCH] ARM: disable FDPIC ABI

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Date:   Mon, 8 Aug 2022 10:49:25 +0100
From:   Vladimir Murzin <vladimir.murzin@....com>
To:     Ben Wolsieffer <ben.wolsieffer@...ring.com>
Cc:     Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ardb@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Nick Hawkins <nick.hawkins@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: disable FDPIC ABI

On 8/1/22 20:17, Ben Wolsieffer wrote:
> When building with an arm-*-uclinuxfdpiceabi toolchain, the FDPIC ABI is
> enabled by default but should not be used to build the kernel.
> Therefore, pass -mno-fdpic if supported by the compiler.
> 
> Signed-off-by: Ben Wolsieffer <Ben.Wolsieffer@...ring.com>
> ---
>  arch/arm/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index c8e3633f5434..88be49b71d40 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -22,6 +22,9 @@ GZFLAGS		:=-9
>  # Never generate .eh_frame
>  KBUILD_CFLAGS	+= $(call cc-option,-fno-dwarf2-cfi-asm)
>  
> +# Disable FDPIC ABI
> +KBUILD_CFLAGS	+= $(call cc-option,-mno-fdpic)
> +
>  # This should work on most of the modern platforms
>  KBUILD_DEFCONFIG := multi_v7_defconfig
>  

Without patch I'm getting

scripts/link-vmlinux.sh: line 52: 312779 Segmentation fault      (core dumped) ${ld} ${ldflags} -o ${output} ${wl}--whole-archive ${objs} ${wl}--no-whole-archive ${wl}--start-group ${libs} ${wl}--end-group $@ ${ldlibs}

So, FWIW:

Reviewed-by: Vladimir Murzin <vladimir.murzin@....com>
Tested-by: Vladimir Murzin <vladimir.murzin@....com>

Unless you get any other comments, please, drop it into RMK's patch system [1].
 
[1] https://www.armlinux.org.uk/developer/patches/

P.S. 
Extra thanks for Buildroot patches, they were handy to build FDPIC toolchain and
test the patch!

Cheers
Vladimir