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

[Geert Uytterhoeven <geert%linux-m68k.org@localhost>]

Hi Arnd,

On Wed, 11 Feb 2026 at 11:41, Geert Uytterhoeven <geert%linux-m68k.org@localhost> wrote:
> On Tue, 6 Jan 2026 at 16:38, Arnd Bergmann <arnd%arndb.de@localhost> wrote:
> > --- a/include/uapi/linux/rseq.h
> > +++ b/include/uapi/linux/rseq.h
> > @@ -142,9 +142,13 @@ struct rseq {
> >         __u32 mm_cid;
> >
> >         /*
> > -        * Flexible array member at end of structure, after last feature field.
> > +        * Flexible array member at end of structure, after last feature field,
> > +        * but overlapping with the padding.
> >          */
> > -       char end[];
> > +       union {
> > +               __u32 :32;
> > +               __DECLARE_FLEX_ARRAY(char, end);
> > +       };
>
> After commit d6200245c75e832a ("rseq: Allow registering RSEQ with
> slice extension"), the padding must be removed again.

And after commit 3b68df978133ac3d ("rseq: slice ext: Ensure rseq
feature size differs from original rseq size"), we need (different)
padding again:

    -    __u32 :32;
    +    __u8 pad[31];

>
> >  } __attribute__((aligned(4 * sizeof(__u64))));
> >
> >  #endif /* _UAPI_LINUX_RSEQ_H */

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert%linux-m68k.org@localhost

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds