[PATCH] PR30592 objcopy: allow --set-section-flags to add or remove SHF_X86_64_LARGE

[Fangrui Song]

On Wed, Jun 28, 2023 at 12:29 AM Andreas Schwab <schwab@suse.de> wrote:
>
> On Jun 27 2023, Fangrui Song via Binutils wrote:
>
> > diff --git a/bfd/elf.c b/bfd/elf.c
> > index 8f6d7d1adba..d6e21b11419 100644
> > --- a/bfd/elf.c
> > +++ b/bfd/elf.c
> > @@ -1034,6 +1034,10 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
> >    if ((hdr->sh_flags & SHF_EXCLUDE) != 0)
> >      flags |= SEC_EXCLUDE;
> >
> > +  if (get_elf_backend_data (abfd)->elf_machine_code == EM_X86_64)
> > +    if ((hdr->sh_flags & SHF_X86_64_LARGE) != 0)
> > +      flags |= SEC_ELF_LARGE;
> > +
> >    switch (elf_elfheader (abfd)->e_ident[EI_OSABI])
> >      {
> >        /* FIXME: We should not recognize SHF_GNU_MBIND for ELFOSABI_NONE,
> > @@ -3351,6 +3355,8 @@ elf_fake_sections (bfd *abfd, asection *asect, void *fsarg)
> >      }
> >    if ((asect->flags & (SEC_GROUP | SEC_EXCLUDE)) == SEC_EXCLUDE)
> >      this_hdr->sh_flags |= SHF_EXCLUDE;
> > +  if (asect->flags & SEC_ELF_LARGE)
> > +    this_hdr->sh_flags |= SHF_X86_64_LARGE;
>
> Doesn't that need to be conditional on EM_X86_64 as well?  I don't see
> anything that blocks SEC_ELF_LARGE from being set on incompatible
> objects.
>
> > diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi
> > index 8c14d1121d9..4dd7b83aaa6 100644
> > --- a/binutils/doc/binutils.texi
> > +++ b/binutils/doc/binutils.texi
> > @@ -1740,13 +1740,14 @@ Set the flags for any sections matching @var{sectionpattern}.  The
> >  @var{flags} argument is a comma separated string of flag names.  The
> >  recognized names are @samp{alloc}, @samp{contents}, @samp{load},
> >  @samp{noload}, @samp{readonly}, @samp{code}, @samp{data}, @samp{rom},
> > -@samp{exclude}, @samp{share}, and @samp{debug}.  You can set the
> > -@samp{contents} flag for a section which does not have contents, but it
> > -is not meaningful to clear the @samp{contents} flag of a section which
> > -does have contents--just remove the section instead.  Not all flags are
> > -meaningful for all object file formats.  In particular the
> > -@samp{share} flag is only meaningful for COFF format files and not for
> > -ELF format files.
> > +@samp{exclude}, @samp{share}, @samp{debug}, and @samp{large}.
> > +You can set the @samp{contents} flag for a section which does not have
> > +contents, but it is not meaningful to clear the @samp{contents} flag of a
> > +section which does have contents--just remove the section instead.  Not all
> > +flags are meaningful for all object file formats.  In particular the
> > +@samp{share} flag is only meaningful for COFF format files and not for ELF
> > +format files.  @samp{large} is an ELF x86-64 specific flag that corresponds to
> > +SHF_X86_64_LARGE.
>
> The last sentence needs to be rearranged so that it doesn't start with a
> lower case word.
>
> --
> Andreas Schwab, SUSE Labs, schwab@suse.de
> GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
> "And now for something completely different."

Thanks for the comments. Uploaded v2
https://sourceware.org/pipermail/binutils/2023-June/128078.html


-- 
宋方睿