linux-kernel - Re: [PATCH v2] riscv module: remove (NOLOAD)

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Date:   Mon, 21 Mar 2022 18:49:12 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Fangrui Song <maskray@...gle.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH v2] riscv module: remove (NOLOAD)

On Mon, Mar 21, 2022 at 06:26:17PM -0700, Fangrui Song wrote:
> On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
> inappropriate for .plt, .got, and .got.plt sections which are always
> SHT_PROGBITS.
> 
> In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
> and (NOLOAD) will be essentially ignored. In ld.lld, since
> https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
> customize the output section type"), ld.lld will report a `section type
> mismatch` error (later changed to a warning). Just remove (NOLOAD) to
> fix the warning.
> 
> [1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
> section should be marked as not loadable" on
> https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
> outdated for ELF.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1597
> Fixes: ab1ef68e5401 ("RISC-V: Add sections of PLT and GOT for kernel module")
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Signed-off-by: Fangrui Song <maskray@...gle.com>

Thank you for the resend! I think the Fixes: tag you chose is more
accurate than Palmer's suggested one. Same tags as v1, if Palmer would
not mind taking them while applying:

Cc: stable@...r.kernel.org
Reviewed-by: Nathan Chancellor <nathan@...nel.org>
Tested-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  arch/riscv/include/asm/module.lds.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/module.lds.h b/arch/riscv/include/asm/module.lds.h
> index 4254ff2ff049..1075beae1ac6 100644
> --- a/arch/riscv/include/asm/module.lds.h
> +++ b/arch/riscv/include/asm/module.lds.h
> @@ -2,8 +2,8 @@
>  /* Copyright (C) 2017 Andes Technology Corporation */
>  #ifdef CONFIG_MODULE_SECTIONS
>  SECTIONS {
> -	.plt (NOLOAD) : { BYTE(0) }
> -	.got (NOLOAD) : { BYTE(0) }
> -	.got.plt (NOLOAD) : { BYTE(0) }
> +	.plt : { BYTE(0) }
> +	.got : { BYTE(0) }
> +	.got.plt : { BYTE(0) }
>  }
>  #endif
> -- 
> 2.35.1.894.gb6a874cedc-goog
>