linux-kernel - Re: [PATCH v5 14/21] modpost: remove is_shndx_special() check from section

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Date:   Wed, 17 May 2023 14:23:16 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nicolas Pitre <npitre@...libre.com>,
        Nicolas Schier <nicolas@...sle.eu>
Subject: Re: [PATCH v5 14/21] modpost: remove is_shndx_special() check from section_rel(a)

On Sun, May 14, 2023 at 8:28 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> This check is unneeded. Without it, sec_name() will returns the null
> string "", then section_mismatch() will return immediately.
>
> Anyway, special section indices do not appear quite often in these
> loops.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Could almost eliminate is_shndx_special after this. I think there's
only one callsite after this? (I should check with the series applied;
this patch fails to apply on mainline if that's relevant for potential
merge conflicts).

Does doing that additional work speed things up though?

> ---
>
>  scripts/mod/modpost.c | 16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 0ef9d6964b6a..28db215ecc71 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1370,7 +1370,6 @@ static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
>  static void section_rela(const char *modname, struct elf_info *elf,
>                          Elf_Shdr *sechdr)
>  {
> -       Elf_Sym  *sym;
>         Elf_Rela *rela;
>         Elf_Rela r;
>         unsigned int r_sym;
> @@ -1413,11 +1412,8 @@ static void section_rela(const char *modname, struct elf_info *elf,
>                                 continue;
>                         break;
>                 }
> -               sym = elf->symtab_start + r_sym;
> -               /* Skip special sections */
> -               if (is_shndx_special(sym->st_shndx))
> -                       continue;
> -               check_section_mismatch(modname, elf, sym,
> +
> +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
>                                        fsecndx, fromsec, r.r_offset, r.r_addend);
>         }
>  }
> @@ -1425,7 +1421,6 @@ static void section_rela(const char *modname, struct elf_info *elf,
>  static void section_rel(const char *modname, struct elf_info *elf,
>                         Elf_Shdr *sechdr)
>  {
> -       Elf_Sym *sym;
>         Elf_Rel *rel;
>         Elf_Rela r;
>         unsigned int r_sym;
> @@ -1472,11 +1467,8 @@ static void section_rel(const char *modname, struct elf_info *elf,
>                 default:
>                         fatal("Please add code to calculate addend for this architecture\n");
>                 }
> -               sym = elf->symtab_start + r_sym;
> -               /* Skip special sections */
> -               if (is_shndx_special(sym->st_shndx))
> -                       continue;
> -               check_section_mismatch(modname, elf, sym,
> +
> +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
>                                        fsecndx, fromsec, r.r_offset, r.r_addend);
>         }
>  }
> --
> 2.39.2
>


-- 
Thanks,
~Nick Desaulniers