2022-08-01 20:00:05

by Ben Wolsieffer

Subject: [PATCH] ARM: disable FDPIC ABI

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 <[email protected]>
---
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

--
2.37.0

2022-08-08 10:03:18

by Vladimir Murzin

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 <[email protected]>
> ---
> 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 <[email protected]>
Tested-by: Vladimir Murzin <[email protected]>

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