Re: [Buildroot] [PATCH v3 0/9] add ARM FDPIC support

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Cc: Giulio Benetti <giulio.benetti@benettiengineering.com>,
	Romain Naour <romain.naour@gmail.com>,
	buildroot@buildroot.org
Subject: Re: [Buildroot] [PATCH v3 0/9] add ARM FDPIC support
Date: Wed, 2 Oct 2024 22:39:31 +0200	[thread overview]
Message-ID: <20241002223931.4df9dde4@windsurf> (raw)
In-Reply-To: <20240929201459.1761285-1-dario.binacchi@amarulasolutions.com>

Hello Dario,

On Sun, 29 Sep 2024 22:14:50 +0200
Dario Binacchi <dario.binacchi@amarulasolutions.com> wrote:

> Ben Wolsieffer (6):
>   Revert: "arch: drop now useless support for FDPIC"
>   arch: don't enable FDPIC binaries by default
>   arch/arm: add support for FDPIC
>   boot/uboot: pass -mno-fdpic if FDPIC is enabled
>   linux: pass -mno-fdpic if FDPIC is enabled
>   package/uclibc: enable NPTL on no-MMU ARM w/ FDPIC
> 
> Dario Binacchi (2):
>   Add the right dependencies on BR2_BINFMT_* to the toolchains
>   configs/stm32f746_disco_sd: new defconfig
> 
> Waldemar Brodkorb (1):
>   package/busybox: remove STATIC from busybox-minimal.config

Thanks for this new iteration, which I have applied, but with some
changes.

Essentially, I changed a bit my mind on PATCH 3/9, and I believe adding
BR2_BINFMT_ELF everywhere was a bit unneeded. And your patch was
actually not sufficient: it still allowed to select the Bootlin ARMv7-M
FLAT toolchain when ARMv7-M FDPIC was selected as the target
architecture in Buildroot.

So I simplified the patch, and only made sure that the Bootlin ARMv7-M
FLAT toolchain can only be selected when BR2_BINFMT_FLAT=y. BTW, in
this patch, you had modified directly
toolchain/toolchain-external/toolchain-external-bootlin/Config.in.options,
but as explained at the beginning of this file, this file is
auto-generated, so modifying it without changing
support/scripts/gen-bootlin-toolchains is somewhat useless.

Also, on the patch actually enabling FDPIC on ARM, I restricted that to
ARMv7-M. I know it in theory works on MMU-capable ARM systems, but
FDPIC really doesn't make any sense in such cases (ELF works just
fine), so nobody will ever use FDPIC on such systems... making the
support of this configuration a bit useless.

Thanks for your persistence with this work!

Best regards,

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