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Re: [PATCH] Exclude zero size section for RELRO segment match
On Sat, Feb 17, 2018 at 03:19:26PM -0800, H.J. Lu wrote:
> On Fri, Feb 16, 2018 at 3:44 PM, Alan Modra <amodra@gmail.com> wrote:
> > --- a/bfd/elf.c
> > +++ b/bfd/elf.c
> > @@ -5897,6 +5897,7 @@ assign_file_positions_for_non_load_sections (bfd *abfd,
> > lm = lm->next, lp++)
> > {
> > if (lp->p_type == PT_LOAD
> > + && lp->p_memsz != 0
> > && lm->count != 0
> > && lm->sections[lm->count - 1]->vma >= start
> > && lm->sections[0]->vma < end)
> >
>
> This patch isn't sufficient. On x86, with this patch, I got
>
> [hjl@gnu-tools-1 ld]$ ../gas/as-new
> -I/export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-elf -o
> tmpdir/tbss.o /export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-elf/tbss.s
> [hjl@gnu-tools-1 ld]$ ../gas/as-new
> -I/export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-elf -o
> tmpdir/frame.o /export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-elf/frame.s
> [hjl@gnu-tools-1 ld]$ ./ld-new -o tmpdir/frame.so -z separate-code
> --shared tmpdir/frame.o tmpdir/tbss.o
> ./ld-new: BFD (GNU Binutils) 2.30.51.20180217 assertion fail
> /export/gnu/import/git/sources/binutils-gdb/bfd/elf.c:5917
> [hjl@gnu-tools-1 ld]$
>
> My original patch fixes them.
You're correct, but the real underlying problem is that my load
section end calculation was wrong. That can be fixed without a loop
scanning back through sections.
BTW, the testsuite changes will need some tweaks before they can be
committed, eg.
/home/alan/build/gas/d30v-elf/ld/ld-new: unrecognized option '-z'
PR 22845
* elf.c (IS_TBSS): Define.
(_bfd_elf_map_sections_to_segments): Use IS_TBSS.
(assign_file_positions_for_non_load_sections): Revert last change.
Properly calculate load segment limits to compare against relro limits.
diff --git a/bfd/elf.c b/bfd/elf.c
index b069b59..f3a70f1 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -4542,6 +4542,9 @@ elf_modify_segment_map (bfd *abfd,
return TRUE;
}
+#define IS_TBSS(s) \
+ ((s->flags & (SEC_THREAD_LOCAL | SEC_LOAD)) == SEC_THREAD_LOCAL)
+
/* Set up a mapping from BFD sections to program segments. */
bfd_boolean
@@ -4801,11 +4804,7 @@ _bfd_elf_map_sections_to_segments (bfd *abfd, struct bfd_link_info *info)
executable = TRUE;
last_hdr = hdr;
/* .tbss sections effectively have zero size. */
- if ((hdr->flags & (SEC_THREAD_LOCAL | SEC_LOAD))
- != SEC_THREAD_LOCAL)
- last_size = hdr->size;
- else
- last_size = 0;
+ last_size = !IS_TBSS (hdr) ? hdr->size : 0;
continue;
}
@@ -4831,10 +4830,7 @@ _bfd_elf_map_sections_to_segments (bfd *abfd, struct bfd_link_info *info)
last_hdr = hdr;
/* .tbss sections effectively have zero size. */
- if ((hdr->flags & (SEC_THREAD_LOCAL | SEC_LOAD)) != SEC_THREAD_LOCAL)
- last_size = hdr->size;
- else
- last_size = 0;
+ last_size = !IS_TBSS (hdr) ? hdr->size : 0;
phdr_index = i;
phdr_in_segment = FALSE;
}
@@ -4843,8 +4839,7 @@ _bfd_elf_map_sections_to_segments (bfd *abfd, struct bfd_link_info *info)
for .tbss. */
if (last_hdr != NULL
&& (i - phdr_index != 1
- || ((last_hdr->flags & (SEC_THREAD_LOCAL | SEC_LOAD))
- != SEC_THREAD_LOCAL)))
+ || !IS_TBSS (last_hdr)))
{
m = make_mapping (abfd, sections, phdr_index, i, phdr_in_segment);
if (m == NULL)
@@ -5897,9 +5892,11 @@ assign_file_positions_for_non_load_sections (bfd *abfd,
lm = lm->next, lp++)
{
if (lp->p_type == PT_LOAD
- && lp->p_memsz != 0
&& lm->count != 0
- && lm->sections[lm->count - 1]->vma >= start
+ && (lm->sections[lm->count - 1]->vma
+ + (!IS_TBSS (lm->sections[lm->count - 1])
+ ? lm->sections[lm->count - 1]->size
+ : 0)) > start
&& lm->sections[0]->vma < end)
break;
}
--
Alan Modra
Australia Development Lab, IBM