Re: [Buildroot] [PATCH v2 1/2] Config.in: ban textrels on musl toolchains

["J. Neuschäfer via buildroot" <buildroot@buildroot.org>]

Hello Yann, sorry for the delay,

On Sat, Jun 01, 2024 at 10:59:53PM +0200, Yann E. MORIN wrote:
> On 2024-05-29 20:22 +0200, J. Neuschäfer via buildroot spake thusly:
> > musl-libc doesn't support TEXTRELs[1] and programs with TEXTRELs will
> > crash on start-up under musl.
> >
> > This patch forbids the use of TEXTRELs on musl, but adds an option to
> > either forbid them on other libcs as well, or allow them on musl.
>
> In your v1, Thomas suggested that textrels be simply always disabled for
> musl, because there is no way they can work. Allowing people to enable
> them on musl will only make things reak at runtime, rather than at build
> time.
>
> I'm on the same page as Thomas here: if textrels are unsupported on
> musl, then let's not allow them at all.

Alright, I wasn't fully certain about it, but I'll change the Kconfig
logic accordingly.

>
> > [1]: https://www.openwall.com/lists/musl/2020/09/25/4
> >
> > Signed-off-by: J. Neuschäfer <j.neuschaefer@gmx.net>
> > ---
> [--SNIP--]
> > diff --git a/Config.in b/Config.in
> > index b5a94325c4..92e89ed32d 100644
> > --- a/Config.in
> > +++ b/Config.in
> > @@ -910,6 +910,20 @@ endchoice
> >  comment "RELocation Read Only (RELRO) needs shared libraries"
> >  	depends on !BR2_SHARED_LIBS
> >
> > +config BR2_LINK_ZTEXT
> > +	bool "Disallow text section relocations (TEXTRELs)"
>
> We prefer positive logic:
>
>     config BR2_LINK_ZTEXT
>         bool "Allow text section relocations (TEXTRELs)"
>         default y  # Legacy
>         depends on !BR2_TOOLCHAIN_USES_MUSL
>         depends on !BR2_STATIC_LIBS

Good idea, this looks a bit easier to understand.

>
> and in the .mk:
>
>     ifeq ($(BR2_LINK_ZTEXT),)
>     TARGET_LDFLAGS += -z text
>     endif
>
> (Note the 'default y': textrels were previously always allowed, so we
> want to keep that behaviour by default)
>
> Regards,
> Yann E. MORIN.

Thanks for your review!
--jn
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