Re: [Buildroot] [PATCH v2 1/4] Revert "arch: drop now useless support for FDPIC"

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Hello Ben,

On Tue,  2 Aug 2022 16:21:39 -0400
Ben Wolsieffer <ben.wolsieffer@hefring.com> wrote:

> This reverts commit 58dcd28dfbed481becb822b009583a63efbc6ffa.
> 
> ARM supports FDPIC, so this code is needed once again.
> 
> Signed-off-by: Ben Wolsieffer <Ben.Wolsieffer@hefring.com>
> ---
>  arch/Config.in           | 14 ++++++++++++++
>  package/uclibc/uclibc.mk |  8 ++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/arch/Config.in b/arch/Config.in
> index 1c0c400a98..c5d481b9e5 100644
> --- a/arch/Config.in
> +++ b/arch/Config.in
> @@ -12,6 +12,9 @@ config BR2_SOFT_FLOAT
>  config BR2_USE_MMU
>  	bool
>  
> +config BR2_ARCH_HAS_FDPIC_SUPPORT
> +	bool
> +
>  choice
>  	prompt "Target Architecture"
>  	default BR2_i386
> @@ -418,6 +421,7 @@ endif
>  choice
>  	prompt "Target Binary Format"
>  	default BR2_BINFMT_ELF if BR2_USE_MMU
> +	default BR2_BINFMT_FDPIC if BR2_ARCH_HAS_FDPIC_SUPPORT

This default means that existing defconfigs for ARM noMMU, which
currently use FLAT binaries will "automatically" switch to FDPIC.

On another topic, I am wondering what happens with external toolchains?
For example at https://toolchains.bootlin.com/releases_armv7m.html we
have ARMv7-M toolchains that produce FLAT binaries. So probably it
means that the toolchain-external-bootlin package needs to be amended
to only offer the existing ARMv7-M toolchain when FLAT binaries are
selected.

I haven't really thought of all the implications, but to me it seems
like the case of external toolchains should be considered, to see what
is the impact of the FDPIC support.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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