Re: [Buildroot] [PATCH v2 3/9] arch: make FDPIC dependent on toolchain support

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

Hello Dario,

Thanks for reposting this patch series after our discussion last
week-end!

On Sun, 22 Sep 2024 11:23:06 +0200
Dario Binacchi <dario.binacchi@amarulasolutions.com> wrote:

> From: Ben Wolsieffer <ben.wolsieffer@hefring.com>
> 
> FDPIC support on ARM requires a certain target name, and therefore is
> only currently available with the Buildroot toolchain. In addition,
> only uClibc-ng supports FDPIC on ARM at the moment.
> 
> This may need to become more complicated if we end up in a situation
> where each libc supports FDPIC on a different set of architectures.

However, I think this patch is incorrect, or more precisely it's not
how we want to handle things. Instead, what we want is:

- For internal toolchains, that C libraries that don't support FDPIC
  are made unavailable when FDPIC is selected. So basically I would add
  a depends on BR2_BINFMT_ELF to BR2_PACKAGE_GLIBC_ARCH_SUPPORTS and
  BR2_PACKAGE_MUSL_ARCH_SUPPORTS. In practice this will be a no-op as
  glibc and musl already have a "depends on BR2_USE_MMU", and FDPIC can
  only be selected on noMMU systems.

- For external toolchains, I would make sure that the ARM toolchains
  properly depend on the relevant BR2_BINFMT_* option.

Best regards,

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