On Mon, Dec 20, 2021 at 10:51 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu:
>
> > We need to set larger p_align > sh_addralign for huge page executables.
> > My current algorithm to decide if p_align should be used as the maximum
> > page size for objcopy is
> >
> > static bool
> > elf_is_p_align_valid (bfd *abfd)
> > {
> > unsigned int i;
> > Elf_Internal_Phdr *segment;
> > unsigned int num_segments;
> > const struct elf_backend_data *bed = get_elf_backend_data (abfd);
> > bfd_size_type maxpagesize = bed->maxpagesize;
> > bfd_size_type commonpagesize = bed->commonpagesize;
> >
> > if (commonpagesize == maxpagesize)
> > return true;
> >
> > /* When the common page size != the maximum page size, p_align may
> > be set to the common page size while segments are aligned to
> > the maximum page size. In this case, the input p_align will be
> > ignored and the maximum page size will be used to align the output
> > segments. */
> > segment = elf_tdata (abfd)->phdr;
> > num_segments = elf_elfheader (abfd)->e_phnum;
> > for (i = 0; i < num_segments; i++, segment++)
> > if (segment->p_type == PT_LOAD
> > && (segment->p_align != commonpagesize
> > || vma_page_aligned_bias (segment->p_vaddr,
> > segment->p_offset,
> > maxpagesize) != 0))
> > return true;
> >
> > return false;
> > }
> >
> > It should cover all cases.
>
> Will this switch from 64K to 4K on POWER and AArch64? I think this will
It will set p_align to ELF_COMMONPAGESIZE. It glibc doesn't support
p_align == ELF_COMMONPAGESIZE, the ELF_COMMONPAGESIZE
is wrong.
> then produce binaries which cannot be loaded by current glibc in all
> cases:
>
> PT_LOAD p_align check is too strict
> <https://sourceware.org/bugzilla/show_bug.cgi?id=28688>
>
> Thanks,
> Florian
>
--
H.J.