linux-kernel - Re: [PATCH v3 0/4] LoongArch: Support new relocation types

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Date:   Fri, 29 Jul 2022 10:23:24 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Xi Ruoyao <xry111@...111.site>, loongarch@...ts.linux.dev
Cc:     linux-kernel@...r.kernel.org, WANG Xuerui <kernel@...0n.name>,
        Huacai Chen <chenhuacai@...nel.org>,
        Jinyang He <hejinyang@...ngson.cn>
Subject: Re: [PATCH v3 0/4] LoongArch: Support new relocation types

Hi, Ruoyao

On 07/29/2022 10:07 AM, Xi Ruoyao wrote:
> The version 2.00 of LoongArch ELF ABI specification introduced new
> relocation types, and the development tree of Binutils and GCC has
> started to use them.  If the kernel is built with the latest snapshot of
> Binutils or GCC, it will fail to load the modules because of unrecognized
> relocation types in modules.
>
> Add support for GOT and new relocation types for the module loader, so
> the kernel (with modules) can be built with the "normal" code model and
> function properly.
>
> This series does not break the compatibility with old toolchain using
> stack-based relocation types, so with the patches applied the kernel can
> be be built with both old and new toolchains.
>
> Tested by building the kernel with both Binutils & GCC master branch and
> my system Binutils & GCC (without new relocation type support), running
> both the builds with 35 in-tree modules loaded, and loading one module
> with 20 GOT loads (loaded addresses verified by comparing with
> /proc/kallsyms).
>
> Changes from v2 to v3:
>
> - Use `union loongarch_instruction` instead of explicit bit shifts
>   applying the relocation.  Suggested by Youling.
> - For R_LARCH_B26, move the alignment check before the range check to be
>   consistent with stack pop relocations.  Suggested by Youling.
> - Reword the commit message of the 3rd patch.  Suggested by Huacai.

The log of changes from v1 to v2 should be preserved.

Thanks,
Youling
>
> Xi Ruoyao (4):
>   LoongArch: Add section of GOT for kernel module
>   LoongArch: Support R_LARCH_SOP_PUSH_GPREL relocation type in kernel
>     module
>   LoongArch: Remove -fplt and -Wa,-mla-* from CFLAGS
>   LoongArch: Support modules with new relocation types
>
>  arch/loongarch/Makefile                 |  4 --
>  arch/loongarch/include/asm/elf.h        | 37 ++++++++++
>  arch/loongarch/include/asm/module.h     | 23 ++++++
>  arch/loongarch/include/asm/module.lds.h |  1 +
>  arch/loongarch/kernel/head.S            | 10 +--
>  arch/loongarch/kernel/module-sections.c | 51 +++++++++++--
>  arch/loongarch/kernel/module.c          | 96 +++++++++++++++++++++++++
>  7 files changed, 209 insertions(+), 13 deletions(-)
>