Re: [PATCH] PR ld/16322: ld fails to generate GNU_RELRO segment

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Dec 12, 2013 at 10:58 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> Hi,
>
> There are 2 bugs:
>
> 1. lang_size_sections didn't properly align base to the maximum
> alignment power of sections between DATA_SEGMENT_ALIGN and
> DATA_SEGMENT_RELRO_END.
> 2. ld failed to adjust LOAD segment to generate GNU_RELRO segment
> when LOAD segment doesn't fit GNU_RELRO segment.  This is
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=14207
>
> We "fixed" ld by not generating GNU_RELRO segment.  This patch
> adjusts LOAD segment to generate GNU_RELRO segment.  It fixes
> PR ld/16322 and at the same time it also fixes PR binutils/16323
> since now we can adjust LOAD segment if it is too small.  OK
> to install?
>
> Thanks.
>
>
> H.J.
> ---
> bfd/
>
> 2013-12-12  H.J. Lu  <hongjiu.lu@intel.com>
>
>         PR ld/14207
>         PR ld/16322
>         PR binutils/16323
>         * elf.c (_bfd_elf_map_sections_to_segments): Don't check section
>         size for PT_GNU_RELRO segment.
>         (assign_file_positions_for_load_sections): If PT_LOAD segment
>         doesn't fit PT_GNU_RELRO segment, adjust its p_filesz and p_memsz.
>
> ld/
>
> 2013-12-12  H.J. Lu  <hongjiu.lu@intel.com>
>
>         PR ld/14207
>         PR ld/16322
>         PR binutils/16323
>         * ldlang.c (lang_size_sections): Properly align RELRO base.
>
> ld/testsuite/
>
> 2013-12-12  H.J. Lu  <hongjiu.lu@intel.com>
>
>         PR ld/14207
>         PR ld/16322
>         PR binutils/16323
>         * ld-elf/pr16322.d: New file.
>         * ld-elf/pr16322.s: Likewise.
>
>         * ld-x86-64/pr14207.d: Expect PT_GNU_RELRO segment.
>
> diff --git a/bfd/elf.c b/bfd/elf.c
> index 66d9644..65d579b 100644
> --- a/bfd/elf.c
> +++ b/bfd/elf.c
> @@ -4176,11 +4176,7 @@ _bfd_elf_map_sections_to_segments (bfd *abfd, struct bfd_link_info *info)
>                         == (SEC_LOAD | SEC_HAS_CONTENTS))
>                       break;
>
> -                 if (i == (unsigned) -1)
> -                   continue;
> -
> -                 if (m->sections[i]->vma + m->sections[i]->size
> -                     >= info->relro_end)
> +                 if (i != (unsigned) -1)
>                     break;
>                 }
>             }
> @@ -4369,6 +4365,7 @@ assign_file_positions_for_load_sections (bfd *abfd,
>    unsigned int alloc;
>    unsigned int i, j;
>    bfd_vma header_pad = 0;
> +  bfd_vma relro_start = 0, relro_end = 0;
>
>    if (link_info == NULL
>        && !_bfd_elf_map_sections_to_segments (abfd, link_info))
> @@ -4439,6 +4436,23 @@ assign_file_positions_for_load_sections (bfd *abfd,
>      header_pad -= off;
>    off += header_pad;
>
> +  /* Get start and end of PT_GNU_RELRO segment.  */
> +  if (link_info != NULL)
> +    {
> +      relro_start = link_info->relro_start;
> +      relro_end = link_info->relro_end;
> +    }
> +  else
> +    {
> +      for (m = elf_seg_map (abfd); m != NULL; m = m->next)
> +       if (m->p_type == PT_GNU_RELRO)
> +         {
> +           relro_start = m->p_paddr;
> +           relro_end = relro_start + m->p_size;
> +           break;
> +         }
> +    }
> +
>    for (m = elf_seg_map (abfd), p = phdrs, j = 0;
>         m != NULL;
>         m = m->next, p++, j++)
> @@ -4781,6 +4795,23 @@ assign_file_positions_for_load_sections (bfd *abfd,
>                 p->p_flags |= PF_W;
>             }
>         }
> +
> +      if (relro_start != 0
> +         && p->p_type == PT_LOAD
> +         && p->p_vaddr >= relro_start)
> +       {
> +         /* If PT_LOAD segment doesn't fit PT_GNU_RELRO segment,
> +            adjust its p_filesz and p_memsz.  */
> +         if (p->p_vaddr + p->p_filesz < relro_end)
> +           {
> +             bfd_vma adjust = relro_end - (p->p_vaddr + p->p_filesz);
> +             p->p_filesz += adjust;
> +             off += adjust;
> +           }
> +         if (p->p_vaddr + p->p_memsz < relro_end)
> +           p->p_memsz += relro_end - (p->p_vaddr + p->p_memsz);
> +       }
> +
>        off -= off_adjust;
>
>        /* Check that all sections are in a PT_LOAD segment.
> diff --git a/ld/ldlang.c b/ld/ldlang.c
> index ba7f493..7851615 100644
> --- a/ld/ldlang.c
> +++ b/ld/ldlang.c
> @@ -5407,7 +5407,8 @@ lang_size_sections (bfd_boolean *relax, bfd_boolean check_regions)
>             {
>               if (expld.dataseg.base - (1 << max_alignment_power) < old_base)
>                 expld.dataseg.base += expld.dataseg.pagesize;
> -             expld.dataseg.base -= (1 << max_alignment_power);
> +             /* Properly align base to max_alignment_power.  */
> +             expld.dataseg.base &= ~((1 << max_alignment_power) - 1);
>               lang_reset_memory_regions ();
>               one_lang_size_sections_pass (relax, check_regions);
>             }

Are there any objections to this patch?

-- 
H.J.