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

[Ben Wolsieffer <ben.wolsieffer@hefring.com>]

On Wed, Aug 03, 2022 at 12:12:03AM +0200, Thomas Petazzoni wrote:
> Hello Ben,
> 
> On Tue,  2 Aug 2022 16:21:39 -0400
> Ben Wolsieffer <ben.wolsieffer@hefring.com> wrote:
> 
> > @@ -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.
> 

I didn't look too closely at this revert before, but yes, it probably
doesn't make sense to enable it by default when adding support for FDPIC
to an existing architecture.

> 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.

The fact that FDPIC requires a certain toolchain target unfortunately
means that the existing prebuilt toolchains can't support it. Perhaps I
should add a BR2_TOOLCHAIN_HAS_FDPIC_SUPPORT option?
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