Re: [Buildroot] [PATCH 03/11] package/Makefile.in: add global ColdFire workaround flags

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

Hello Jean-Michel,

On Fri, Apr 24, 2026 at 03:23:18PM +0200, Jean-Michel Hautbois wrote:
> GCC's instruction scheduler on m68k ColdFire reorders memory accesses
> in ways that break code assuming sequential memory ordering. This was
> observed in uClibc-ng's elf_machine_relative and in OpenSSL's internal
> state management after fork().
> 
> Additionally, ColdFire uses 16-bit offsets for switch statement jump
> tables by default. Large functions such as pcre2_match() and nftables
> rule evaluation overflow this limit, causing assembler errors.
> 
> Add -fno-schedule-insns, -fno-schedule-insns2, and
> -mlong-jump-table-offsets globally for BR2_m68k_cf, alongside the
> existing -fno-dwarf2-cfi-asm workaround.
> 
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>
> ---
>  package/Makefile.in | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/package/Makefile.in b/package/Makefile.in
> index 5ebb5f9ba8..42dd79118d 100644
> --- a/package/Makefile.in
> +++ b/package/Makefile.in
> @@ -211,6 +211,10 @@ TARGET_FCFLAGS = $(TARGET_ABI) $(TARGET_OPTIMIZATION) $(TARGET_DEBUGGING)
>  ifeq ($(BR2_m68k_cf),y)
>  TARGET_CFLAGS += -fno-dwarf2-cfi-asm
>  TARGET_CXXFLAGS += -fno-dwarf2-cfi-asm
> +TARGET_CFLAGS += -fno-schedule-insns -fno-schedule-insns2
> +TARGET_CXXFLAGS += -fno-schedule-insns -fno-schedule-insns2
> +TARGET_CFLAGS += -mlong-jump-table-offsets
> +TARGET_CXXFLAGS += -mlong-jump-table-offsets

I'm not against this, but you're changing those flags for everyone
using Coldfire, not only for your new Coldfire processor. Is this the
right thing to do? Are those issues also affecting other Coldfire
processors, and nobody noticed until now because almost nobody uses
Coldfire?

I think this is the part that's a bit missing in your description:
give confidence that the BR2_m68k_cf is the right condition for this.

Regarding -mlong-jump-table-offsets should we do this globally, or on
a per package basis, like we do with -mxgot?

Best regards,

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