linux-kernel - Re: [PATCH 1/3] LoongArch: tools: Add relocs tool support

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Date:   Wed, 7 Sep 2022 18:19:10 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Xi Ruoyao <xry111@...111.site>, Jinyang He <hejinyang@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>
Cc:     linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev,
        Xuerui Wang <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: Re: [PATCH 1/3] LoongArch: tools: Add relocs tool support

Hi, Ruoyao

On 09/06/2022 01:17 PM, Xi Ruoyao wrote:
> On Tue, 2022-09-06 at 10:16 +0800, Youling Tang wrote:
>
>> Switch to relative exception tables:
>>
>> https://github.com/tangyouling/linux/commit/6525b8da
>> https://github.com/tangyouling/linux/commit/b6ac0827
>>
>> Will switch to the relative exception tables after applying the above
>> two patches. So there is no need to relocate the exception table
>> (remove relocate_exception_table).
>>
>> Now we can remove the relocation of la.abs , got and ex_table, but
>> still need to relocate LARCH_64. Is there anything else that needs to
>> be modified to eliminate this relocation?
>
> You may see the RISC-V patch as a reference:
>
> https://lore.kernel.org/all/20211009171259.2515351-2-alexandre.ghiti@canonical.com/
>
> Basically, make the linker to generate R_*_RELATIVE instead of R_*_64
> for pointers.  And, perform R_*_RELATIVE relocation loading the kernel.
>
> Something problematic IMO: RISC-V uses "-shared" to trick the linker to
> generate R_*_RELATIVE but I consider it ugly (if the kernel is a shared
> library, my grandma will be a wagon!)  I prefer "-pie -static", but our
> Glibc does not have static-pie support for now.  It won't really affect
> the kernel (we are -nostdlib), but we cannot learn how to handle
> R_*_RELATIVE in static pie from Glibc then.
>

After applying all the patches in the link [1], the implementation of 
the relocs tool can now be removed :).

commit: 244fb0971a ... ad45233ef6

[1] https://github.com/tangyouling/loongarch-next/commits/loongarch-next

Youling.