linux-kernel - Re: [PATCH 0/8] LoongArch: Support toolchain with new relocation types

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Date:   Sun, 28 Aug 2022 22:15:24 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Xi Ruoyao <xry111@...111.site>
Cc:     loongarch@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Youling Tang <tangyouling@...ngson.cn>,
        Jinyang He <hejinyang@...ngson.cn>
Subject: Re: [PATCH 0/8] LoongArch: Support toolchain with new relocation types

Hi, Ruoyao,

On Sun, Aug 28, 2022 at 1:55 AM Xi Ruoyao <xry111@...111.site> 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 the following combinations:
>
> - GCC 12 and Binutils 2.39
> - GCC 12 and Binutils trunk
> - GCC trunk and Binutils trunk
>
> and running the builds with 35 in-tree modules loaded, and loading one
> module with 20 GOT loads and a per-CPU variable (loaded addresses
> verified by comparing with /proc/kallsyms).
>
> This superseds "LoongArch: Support new relocation types" series.  I
> don't make it a "v5" because too much things have changed so it's better
> to treat this as a new series.
1, You can still call it v5, even if it has changed a lot;
2, In my opinion, patch 4,5,7,8 can be combined, but I don't insist if
you have a good reason to separate.
3, If possible, I still prefer to remove old relocation types support,
in order to make life easier, especially for objtool that is queued
for upstream.



Huacai

>
> Xi Ruoyao (8):
>   LoongArch: Add CONFIG_CC_HAS_EXPLICIT_RELOCS
>   LoongArch: Only use -Wa,-mla-* options for
>     !CONFIG_CC_HAS_EXPLICIT_RELOCS
>   LoongArch: Define ELF relocation types added in v2.00 ABI
>   LoongArch: Support R_LARCH_B26 in modules
>   LoongArch: Support R_LARCH_ABS* in modules
>   LoongArch: Use model("extreme") attribute for per-CPU variables in
>     module if CONFIG_CC_HAS_EXPLICIT_RELOCS
>   LoongArch: Support R_LARCH_PCALA* in modules
>   LoongArch: Support R_LARCH_GOT_PC* in modules
>
>  arch/loongarch/Kconfig                  |   3 +
>  arch/loongarch/Makefile                 |  15 ++-
>  arch/loongarch/include/asm/elf.h        |  37 +++++++
>  arch/loongarch/include/asm/module.h     |  23 ++++
>  arch/loongarch/include/asm/module.lds.h |   1 +
>  arch/loongarch/include/asm/percpu.h     |  13 +++
>  arch/loongarch/kernel/head.S            |  10 +-
>  arch/loongarch/kernel/module-sections.c |  56 +++++++++-
>  arch/loongarch/kernel/module.c          | 138 +++++++++++++++++++++++-
>  9 files changed, 285 insertions(+), 11 deletions(-)
>
> --
> 2.37.0
>