Re: [Buildroot] [PATCH 07/11] package/dropbear: disable ML-KEM768 on m68k

From: Baruch Siach via buildroot <buildroot@buildroot.org>
To: Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>
Cc: buildroot@buildroot.org,  Bernd Kuhls <bernd@kuhls.net>,
	 Fabrice Fontaine <fontaine.fabrice@gmail.com>,
	 Giulio Benetti <giulio.benetti@benettiengineering.com>,
	 Ismael Luceno <ismael@iodev.co.uk>,
	 Romain Naour <romain.naour@gmail.com>,
	 Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [Buildroot] [PATCH 07/11] package/dropbear: disable ML-KEM768 on m68k
Date: Fri, 24 Apr 2026 17:11:07 +0300	[thread overview]
Message-ID: <87mrys30uc.fsf@tarshish> (raw)
In-Reply-To: <20260424132326.825570-8-jeanmichel.hautbois@yoseli.org> (Jean-Michel Hautbois's message of "Fri, 24 Apr 2026 15:23:22 +0200")

Hi Jean-Michel,

On Fri, Apr 24 2026, Jean-Michel Hautbois wrote:
> ML-KEM768 post-quantum key exchange code (in the vendored header
> src/libcrux_mlkem768_sha3.h) triggers a GCC internal compiler error
> (ICE) in cselib_record_set during the postreload CSE pass on m68k.
> Reproduced on m68k-buildroot-linux-uclibc (cf5441x, -O2) with both
> GCC 14.3.0 (the current Buildroot default for m68k) and GCC 15.2.0.
>
> The failing pass backtrace is:
>   reload_cse_regs_1
>   -> pass_postreload_cse::execute
>      -> cselib_process_insn
>         -> cselib_record_sets
>            -> cselib_record_set  (cselib.cc:2869 on gcc 15)
>
> Disable ML-KEM768 via localoptions.h on m68k until the GCC bug is
> resolved. Standard key exchange algorithms remain available.

Common practice for GCC bugs is to add a BR2_TOOLCHAIN_HAS_GCC_BUG_[id]
config symbol to toolchain/Config.in, and use that symbol to activate
bug specific workaround. [id] refers to GCC Bugzilla bug ID. This makes
it easier to track the GCC versions this bug affects.

baruch

>
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>
> ---
>  package/dropbear/dropbear.mk | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/package/dropbear/dropbear.mk b/package/dropbear/dropbear.mk
> index e4e42cf994..52bc15e346 100644
> --- a/package/dropbear/dropbear.mk
> +++ b/package/dropbear/dropbear.mk
> @@ -62,6 +62,13 @@ endef
>  DROPBEAR_POST_EXTRACT_HOOKS += DROPBEAR_SVR_PASSWORD_AUTH
>  endif
>  
> +ifeq ($(BR2_m68k),y)
> +define DROPBEAR_DISABLE_MLKEM
> +	echo '#define DROPBEAR_MLKEM768 0'               >> $(@D)/localoptions.h
> +endef
> +DROPBEAR_POST_EXTRACT_HOOKS += DROPBEAR_DISABLE_MLKEM
> +endif
> +
>  ifeq ($(BR2_PACKAGE_DROPBEAR_LEGACY_CRYPTO),y)
>  define DROPBEAR_ENABLE_LEGACY_CRYPTO
>  	echo '#define DROPBEAR_3DES 1'                  >> $(@D)/localoptions.h

-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -
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