[PATCH v2] elf: Add optimization barrier for __ehdr_start and _end

[Jakub Jelinek]

On Mon, Jun 16, 2025 at 09:55:38AM +0300, Alexander Monakov wrote:
> > So just make it
> >    _dl_rtld_map.l_map_start = (ElfW(Addr)) &__ehdr_start;
> > +  asm ("" : "=m" (_dl_rtld_map) : "m" (_dl_rtld_map));
> >    _dl_rtld_map.l_map_end = (ElfW(Addr)) _end;
> > +  asm ("" : "=m" (_dl_rtld_map) : "m" (_dl_rtld_map));
> 
> In this case, either just the first asm is sufficient to break up this
> vectorizable pair, or additional such asm is necessary in the beginning to
> prevent forming a pair with l_map_start and the preceding field, just like
> the second asm prevents forming a pair out of l_map_end and the next field.

Yes.  Just one in the middle will fix the current problem.
And as the preceding and following members are l_origin and l_scope_mem,
neither of which is stored in rtld.c, I think just one will be enough for
the stores in that area.

	Jakub