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Re: Question on BIGGEST_ALIGNMENT in GCC on NetBSD/m68k



Hi Jason,

On Mon, 2025-06-16 at 07:43 -0700, Jason Thorpe wrote:
> > On Jun 16, 2025, at 2:10 AM, Laurent Vivier <laurent@vivier.eu> wrote:
> > 
> > I think you need to change the ABI type in the ELF header:
> > https://fr.wikipedia.org/wiki/Executable_and_Linkable_Format
> 
> 4-byte alignment binaries should have ELFOSABI_SYSV (0) (since that ABI spec
> is where the 4 byte alignment comes from).  If Linux/m68k is already using that,
> then those binaries are broken by definition.

Unfortunately, that's exactly the case:

root@mitchy:~# uname -a
Linux mitchy 6.15.0-rc2-virt #1 Thu May  1 10:27:28 UTC 2025 m68k GNU/Linux
root@mitchy:~# readelf -h /bin/bash |grep "OS/ABI"
  OS/ABI:                            UNIX - System V
root@mitchy:~#

> Let’s hope existing Linux/m68k binaries are using ELFOSABI_LINUX / ELFOSABI_GNU (3)
> (sorry, I don’t have any handy to check).

hppa is using it:

glaubitz@panama:~$ 
glaubitz@panama:~$ uname -a
Linux panama 6.12.32-parisc64 #1 SMP Debian 6.12.32-1 (2025-06-07) parisc64 GNU/Linux
glaubitz@panama:~$ readelf -h /bin/bash|grep "OS/ABI"
  OS/ABI:                            UNIX - GNU
glaubitz@panama:~$

> If the existing binaries correctly label themselves has having the Linux-specific ABI,
> then this is trivial and there’s no reason to use a note to differentiate them.

I don't have a strong preference as both of them are used in the Linux kernel.

Adrian

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