Re: Preliminary results - was: Re: Question on BIGGEST_ALIGNMENT in GCC on NetBSD/m68k

[John Paul Adrian Glaubitz <glaubitz%physik.fu-berlin.de@localhost>]

Hi Kolbjørn,

On Tue, 2026-01-06 at 14:34 +0100, Kolbjørn Barmen wrote:
> On Mon, 16 Jun 2025, John Paul Adrian Glaubitz wrote:
> 
> > To summarize:
> > 
> > - the ELF header provides provides the e_ident and e_flags fields which could be
> >   used for identifying a Linux/m68k system using the 4 bytes alignment ABI
> > - MIPS uses e_flags for differentiating its ABIs
> > - PA-RISC sets e_ident to 0x03 (Linux) while every other arch uses 0x00 (SysV ABI)
> > - qemu-user needs to be patched to deal with the changed alignment (include/user/abitypes.h)
> > - the kernel needs to be patched to deal with the changed alignment (arch/m68k/kernel/signal.c)
> 
> 
> Does this patch exist somewhere? I ask because I am migrating to
> 32bit-aligned userland (https://www.gentoo.org/downloads/#m68k) and the
> gcc provided fails building kernel, stopping at arch/m68k/kernel/signal.c

I haven't created that patch yet as my work on this effort is currently paused. However, it should
be straight-forward to update the asserts in the kernel code.

According to Geert, Arnd Bergmann made some changes to the kernel uapi that would allow the kernel
to be built with either alignment. Not sure what the current state of things is.

Let's CC Arnd to find out.

Adrian

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