[PATCH] elf: Handle the section flag 'o' linked to special sections

[H.J. Lu]

On Sat, Jan 10, 2026 at 6:23 PM Zheng Bao <fishbaoz@hotmail.com> wrote:
>
> Updated, including bugzilla ticket.
>
> Zheng
>
> ________________________________
> From: H.J. Lu <hjl.tools@gmail.com>
> Sent: Saturday, January 10, 2026 9:31 AM
> To: Zheng Bao <fishbaoz@hotmail.com>
> Cc: Binutils <binutils@sourceware.org>
> Subject: Re: [PATCH 33744] Check if a section has non-zero linked_to before using it
>
> On Sat, Jan 10, 2026, 2:54 PM Zheng Bao <fishbaoz@hotmail.com> wrote:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=33744
>
>     gas:bfd: Check if a section has non-zero linked_to before using it
>
>     The symbol in the section header should be assigned at
>     building stage. So it should be section like ".data".
>     The section where the symbol is defined should have output
>     section. But it is not enough. The common section has output
>     section which will not be written into any target section.
>     If the symbol is in common section, the linked_to is pointer
>     NULL and a segmentation fault comes up.
>
>     Test suite:
>     .section __patchable_funrtion_entries,"awo",%progbits,foo
>             .dc.a   .LPFE1
>             .comm   foo,8
>
>
> This test should be included in the patch.
>
>
>     The changes in _bfd_elf_copy_special_section_fields is a similar
>     change. It also need to check before using it.
>
>     Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33744
>     Signed-off-by: Zheng Bao <fishbaoz@hotmail.com>
>

The patch is wrong.  Here is a simple fix with tests.

--
H.J.

Call _bfd_elf_section_from_bfd_section to get the sh_link value from
the section flag 'o' directive, which may point to special sections,
like SHN_ABS or SHN_COMM.  Update readelf to print the special section
names in the sh_link field.

bfd/

PR gas/33744
* elf.c (assign_section_numbers): Call
_bfd_elf_section_from_bfd_section to get the sh_link value.

binutils/

PR gas/33744
* readelf.c (special_defined_section_index): New.
(get_32bit_section_headers): Don't warn special section indexes
in the sh_link field.
(get_64bit_section_headers): Likewise.
(process_section_headers): Print special section names.

gas/

PR gas/33744
* testsuite/gas/elf/elf.exp: Run PR gas/33744 tests.
* testsuite/gas/elf/sh-link-abs-1.d: New file.
* testsuite/gas/elf/sh-link-abs-2.d: Likewise.
* testsuite/gas/elf/sh-link-abs-3-32.d: Likewise.
* testsuite/gas/elf/sh-link-abs-3-64.d: Likewise.
* testsuite/gas/elf/sh-link-abs-4-32.d: Likewise.
* testsuite/gas/elf/sh-link-abs-4-64.d: Likewise.
* testsuite/gas/elf/sh-link-abs.s: Likewise.
* testsuite/gas/elf/sh-link-common-1.d: Likewise.
* testsuite/gas/elf/sh-link-common-2.d: Likewise.
* testsuite/gas/elf/sh-link-common-3-32.d: Likewise.
* testsuite/gas/elf/sh-link-common-3-64.d: Likewise.
* testsuite/gas/elf/sh-link-common-4-32.d: Likewise.
* testsuite/gas/elf/sh-link-common-4-64.d: Likewise.
* testsuite/gas/elf/sh-link-common.s: Likewise.
* testsuite/gas/elf/sh-link-large-common-1.d: Likewise.
* testsuite/gas/elf/sh-link-large-common-2.d: Likewise.
* testsuite/gas/elf/sh-link-large-common-3.d: Likewise.
* testsuite/gas/elf/sh-link-large-common-4.d: Likewise.
* testsuite/gas/elf/sh-link-large-common.s: Likewise.
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