Re: [PATCH] loongarch: Only select HAVE_OBJTOOL and allow ORC unwinder if the inline assembler supports R_LARCH_{32,64}_PCREL

[Xi Ruoyao]

On Wed, 2024-06-05 at 09:52 +0800, Huacai Chen wrote:
> Hi, Ruoyao,
> 
> On Tue, Jun 4, 2024 at 11:08 PM Xi Ruoyao <xry111@xxxxxxxxxxx> wrote:
> > 
> > GAS <= 2.41 does not support generating R_LARCH_{32,64}_PCREL for
> > "label - ." and it generates R_LARCH_{ADD,SUB}{32,64} pairs instead.
> > objtool cannot handle R_LARCH_{ADD,SUB}{32,64} pair in __jump_table
> > (static key implementation) and etc. so it will produce some warnings.
> > This is causing the kernel CI systems to complain everywhere.
> > 
> > For GAS we can check if -mthin-add-sub option is available to know if
> > R_LARCH_{32,64}_PCREL are supported.
> I think we should give a chance to toolchains without the
> -mthin-add-sub option, so I hope Tiezhu can resubmit this patch to
> solve this problem.
> https://lore.kernel.org/loongarch/1690272910-11869-6-git-send-email-yangtiezhu@xxxxxxxxxxx/

It only handles .discard.{un,}reachable but not __jump_table. 
__jump_table is our main issue here.  And I don't see a quick way to
make -mno-thin-add-sub work for __jump_table because we really need to
resolve the relocation for __jump_table instead of simply skipping it.

-- 
Xi Ruoyao <xry111@xxxxxxxxxxx>
School of Aerospace Science and Technology, Xidian University