[LLVMdev] [lld] Relocation sections format: .rela / .rel

Simon Atanasyan simon at atanasyan.com
Thu Jan 23 00:59:43 PST 2014

I create a patch which adds new virtual function to the
ELFLinkingContext class and calls this function everywhere where we
need to select a relocation table format, dynamic table tags etc.


On Mon, Jan 20, 2014 at 1:36 AM, Shankar Easwaram <shankarke at gmail.com> wrote:
> I think the linking context should decide whether to use rel (or) rela. This is also needed if --emit-relocations option is chosen (or) -r option is used.
> Thoughts ?
> Sent from my iPhone
>> On Jan 19, 2014, at 15:01, Simon Atanasyan <simon at atanasyan.com> wrote:
>> Hi,
>> Now lld writes relocations to the ".rela" sections only. Mips requires
>> to use the "rel" format. So we need to be able to select format and
>> names of relocation section, names of symbols like __rela_iplt_* /
>> __rel_iplt_*, dynamic table tag DT_RELA / DT_REL.
>> My current idea:
>> - Add two virtual functions
>> DefaultLayout::createDynamicRelocationTable() and
>> DefaultLayout::getPLTRelocationTable(). Call these functions when we
>> need to create relocation tables. By default these function create
>> .rela.* sections.
>> - Override createDynamicRelocationTable() and getPLTRelocationTable()
>> in the MipsTargetLayout to create .rel.* sections.
>> - Add support for writing Elf_Rel entries to the RelocationTable
>> class. Maybe it's better to inherit form RelocationTable two separate
>> classes deal with lf_Rela / Elf_Rel entries.
>> - It's unclear to me how to select names of symbols like __rela_iplt_*
>> / __rel_iplt_* and dynamic table tag DT_RELA / DT_REL.
>> Is it an appropriate solution? Any objections or suggestions?
>> Thanks.

Simon Atanasyan

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