linux-kernel - Re: [PATCH v2 0/4] LoongArch: Support new relocation types

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Date:   Thu, 28 Jul 2022 20:33:51 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Xi Ruoyao <xry111@...111.site>, Arnd Bergmann <arnd@...db.de>
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 v2 0/4] LoongArch: Support new relocation types

Hi, Arnd,


On Thu, Jul 28, 2022 at 7:49 PM 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.
>
> Tested by building the kernel with Binutils & GCC master branch,
> running the kernel with 35 in-tree modules loaded, and loading one
> module with 20 GOT loads (both old SOP_PUSH_GPREL and new
> GOT_PC_HI20/GOT_PC_LO12 relocations tested, and loaded addresses
> verified by comparing with /proc/kallsyms).
>
> Link: https://github.com/loongson/LoongArch-Documentation/pull/57
> Link: https://gcc.gnu.org/r13-1834
> Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f09482a
Could you update the cross-compilers here [1] to make this series be
possible upstream in the 5.20 cycle? Or we can only do that until new
binutils/gcc be released?

[1] https://mirrors.edge.kernel.org/pub/tools/crosstool/

Huacai
>
> Changes from v1 to v2:
>
> - Fix a stupid programming error (confusion between the number of PLT
>   entries and the number of GOT entries).  (Bug spotted by Youling).
> - Synthesize the _GLOBAL_OFFSET_TABLE_ symbol with module.lds, instead
>   of faking it at runtime.  The 3rd patch from V1 is now merged into
>   the 1st patch because it would be a one-line change.  (Suggested by
>   Jinyang).
> - Keep reloc_rela_handlers[] ordered by the relocation type ID.
>   (Suggested by Youling).
> - Remove -fplt along with -Wa,-mla-* options because it's the default.
>   (Suggested by 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: Stop using undocumented assembler options
>   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          | 94 +++++++++++++++++++++++++
>  7 files changed, 207 insertions(+), 13 deletions(-)
>
> --
> 2.37.0
>