[PATCH v2] readelf: Save and dump the original section header values

[H.J. Lu]

On Sat, Jul 4, 2026 at 8:39 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Sat, Jul 4, 2026 at 7:49 AM Alan Modra <amodra@gmail.com> wrote:
> >
> > On Fri, Jul 03, 2026 at 10:30:14PM +0800, H.J. Lu wrote:
> > > validate_section_info clears the garbage values in the section header
> > > to avoid crash later.  Save and dump the original section header values
> > > to make the garbage values in the section header visible when dumping
> > > section headers.
> >
> > I think this would be better done the other way around.  ie. have a
> > Elf_Internal_Shdr **sane_section_headers that is initialised to point
> > at entries in section_headers, with sane_section_headers[i] allocated
> > as necessary when needing to correct a bogus header.
> >
>
> I have thought about something similar and decided against it
> since filedata->section_headers is used in many places.   However,
> I can change filedata->orig_section_headers to on demand.
>
> --
> H.J.

Changes in v2:

1.  filedata->orig_section_headers is changed to on demand.

-- 
H.J.
---
validate_section_info clears the garbage values in the section header
to avoid crash later.  Save and dump the original section header values
to make the garbage values in the section header visible when dumping
section headers.

Note: orig_section_headers, instead of sane_section_headers, is added to
filedata since filedata->section_headers is used in many places.  Replace
filedata->section_headers with filedata->sane_section_headers requires
a much bigger change.

* readelf.c (filedata): Add orig_section_headers.
(save_original_section_header_values): New.
(validate_section_info): Add a pointer to the original section
header and call save_original_section_header_values to save the
original section header values before clearing the section header
fields.
(get_32bit_section_headers): Allocate the original section header
buffer.  Pass the original section header pointer to
validate_section_info.
(get_64bit_section_headers): Likewise.
(process_section_headers): Dump the original section header
values if they exist.
(process_relocs): Pass a dummy original section pointer to
validate_section_info.
(free_filedata): Free filedata->orig_section_headers.
* testsuite/binutils-all/corrupt-1.elf.bz2: New file.
* testsuite/binutils-all/corrupt-1.r: Likewise.
* testsuite/binutils-all/readelf.exp: Run corrupt-1.elf test.
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