Re: Overlapping program headers/segments

[Max Larsson <max.larsson@gmx.de>]

> You didn't provide the linker script, which may have the observed effect together
> with your code change: If it puts .text and .rodata together, then the overlap is
> to be expected (as would frequently happen for NOTE segments and .note sections),
> I think.

Forget to mention. I using a slight modified elf.sc script, but even
using the plain elf.sc linker
script gives me overlapping  segments. But i think i found the
issue/solution. Read below.

>> So my question why do I get such a result, and how can I avoid it?
>
> If you want to avoid the overlap you need to provide enough padding
> between TEXT and RODATA.  See the handling of SEPARATE_CODE in
> scripttempl/elf.sc.

I tried that, but it doesn't give me the desired result. I need more a
result delivered
be enabling WRITABLE_RODATA. But a writable .rodata section isn't
liked as primer
solution. It's a possible the backup plan.

Nevertheless your hint with SEPARATE_CODE did lead to a solution, even
if I  cannot
reconstruct how i got there.
As mention I copied the solution from
elfxx-mips.c:_bfd_mips_elf_modify_segment_map to
put the .rodata section in its own segment. What I wondered about was
that the code
just looks for the section and just puts it in a new segment, but it
did not remove the section
from the origin segment.

Now I copied the code and adopted it from elf32-spu.c:
spu_elf_modify_segment_map, which not only put the section in its own
segment but
even removes it from the origin segment. Doing so gives me no
overlapping segments.

Thus the code I used in the first place may not have used the internal
data structures in the "correct"
way, leaving a section somehow in two segments, which gives wrong
calculated addresses and offsets?

Anyway thanks for the help.

kind regards

Max



On Mon, Sep 25, 2023 at 9:24 AM Andreas Schwab <schwab@suse.de> wrote:
>
> On Sep 24 2023, Max Larsson via Binutils wrote:
>
> > So my question why do I get such a result, and how can I avoid it?
>
> If you want to avoid the overlap you need to provide enough padding
> between TEXT and RODATA.  See the handling of SEPARATE_CODE in
> scripttempl/elf.sc.
>
> --
> 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."