linux-kernel - Re: [PATCH 2/2] modpost: factor out the common boilerplate of section

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Message-ID: <CAKwvOdk=dpEzqzyNvKuUaev+qJ4gyhXnhuFDgF+dxSqMkVfpcw@mail.gmail.com>
Date:   Mon, 2 Oct 2023 09:01:27 -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 Schier <nicolas@...sle.eu>
Subject: Re: [PATCH 2/2] modpost: factor out the common boilerplate of section_rel(a)

On Sat, Sep 30, 2023 at 10:47 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> The first few lines of section_rel() and section_rela() are the same.
> They both retrieve the index of the section to which the relocaton

s/relocaton/relocation/

> applies, and skip known-good sections. This common code should be moved
> to check_sec_ref().
>
> Avoid ugly casts when computing 'start' and 'stop', and also make the
> Elf_Rel and Elf_Rela pointers const.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>
>  scripts/mod/modpost.c | 50 ++++++++++++++++++++++---------------------
>  1 file changed, 26 insertions(+), 24 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 15d78fe152ac..0e18fe617ed1 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1425,17 +1425,10 @@ static void get_rel_type_and_sym(struct elf_info *elf, uint64_t r_info,
>  }
>
>  static void section_rela(struct module *mod, struct elf_info *elf,
> -                        Elf_Shdr *sechdr)
> +                        unsigned int fsecndx, const char *fromsec,
> +                        const Elf_Rela *start, const Elf_Rela *stop)
>  {
> -       Elf_Rela *rela;
> -       unsigned int fsecndx = sechdr->sh_info;
> -       const char *fromsec = sec_name(elf, fsecndx);
> -       Elf_Rela *start = (void *)elf->hdr + sechdr->sh_offset;
> -       Elf_Rela *stop  = (void *)start + sechdr->sh_size;
> -
> -       /* if from section (name) is know good then skip it */
> -       if (match(fromsec, section_white_list))
> -               return;
> +       const Elf_Rela *rela;
>
>         for (rela = start; rela < stop; rela++) {
>                 Elf_Addr taddr, r_offset;
> @@ -1465,17 +1458,10 @@ static void section_rela(struct module *mod, struct elf_info *elf,
>  }
>
>  static void section_rel(struct module *mod, struct elf_info *elf,
> -                       Elf_Shdr *sechdr)
> +                       unsigned int fsecndx, const char *fromsec,
> +                       const Elf_Rel *start, const Elf_Rel *stop)
>  {
> -       Elf_Rel *rel;
> -       unsigned int fsecndx = sechdr->sh_info;
> -       const char *fromsec = sec_name(elf, fsecndx);
> -       Elf_Rel *start = (void *)elf->hdr + sechdr->sh_offset;
> -       Elf_Rel *stop  = (void *)start + sechdr->sh_size;
> -
> -       /* if from section (name) is know good then skip it */
> -       if (match(fromsec, section_white_list))
> -               return;
> +       const Elf_Rel *rel;
>
>         for (rel = start; rel < stop; rel++) {
>                 Elf_Sym *tsym;
> @@ -1530,10 +1516,26 @@ static void check_sec_ref(struct module *mod, struct elf_info *elf)
>
>                 check_section(mod->name, elf, sechdr);
>                 /* We want to process only relocation sections and not .init */
> -               if (sechdr->sh_type == SHT_RELA)
> -                       section_rela(mod, elf, sechdr);
> -               else if (sechdr->sh_type == SHT_REL)
> -                       section_rel(mod, elf, sechdr);
> +               if (sechdr->sh_type == SHT_REL || sechdr->sh_type == SHT_RELA) {
> +                       /* section to which the relocation applies */
> +                       unsigned int secndx = sechdr->sh_info;
> +                       const char *secname = sec_name(elf, secndx);
> +                       const void *start, *stop;
> +
> +                       /* If the section is known good, skip it */
> +                       if (match(secname, section_white_list))
> +                               continue;
> +
> +                       start = sym_get_data_by_offset(elf, i, 0);
> +                       stop = start + sechdr->sh_size;
> +
> +                       if (sechdr->sh_type == SHT_RELA)
> +                               section_rela(mod, elf, secndx, secname,
> +                                            start, stop);
> +                       else
> +                               section_rel(mod, elf, secndx, secname,
> +                                           start, stop);
> +               }
>         }
>  }
>
> --
> 2.39.2
>


-- 
Thanks,
~Nick Desaulniers