Hi Ard,
On Thu, Aug 25, 2022 at 2:56 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> On Thu, 25 Aug 2022 at 14:21, Yann Sionneau <ysionneau@xxxxxxxxx> wrote:
> > Well, I am not completely sure about that. See my cover letter, previous
> > mechanism for symbol CRC was actually enforcing the section alignment to
> > 4 bytes boundary as well.
Yes, because else it may become 2-byte aligned on m68k.
> > Also, I'm not sure it is forbidden for an architecture/compiler
> > implementation to actually enforce a stronger alignment on u32, which in
> > theory would not break anything.
> >
>
> u32 is a Linux type, and Linux expects natural alignment (and padding).
Is it? You probably mean its alignment should not be larger than
4 bytes? Less has been working since basically forever.
> So if your toolchain/architecture violates this rule, I suggest you
> typedef u32 to 'unsigned int __aligned(4)' explicitly. so that things
> don't break in other places.
>
> However, even then, I am highly skeptical. This really seems like an
> issue in your toolchain that could cause problems all over the place.
>
> > But in this precise case it does break something since it will cause
> > "gaps" in the end result vmlinux binary segment. For this to work I
> > think we really want to enforce a 4 bytes alignment on the section.
>
> You are addressing one of many potential issues that could be caused
> by this, so I don't think this patch is a good idea tbh.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
