linux-kernel - Re: [PATCH 1/3] modpost: factor out inst location calculation to section

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Message-ID: <CAKwvOdmSUkyb_fwDJ-_bKxo65MRWUShc25L5itWt4m4MTYi=yQ@mail.gmail.com>
Date:   Thu, 22 Jun 2023 11:25:04 -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 1/3] modpost: factor out inst location calculation to section_rel()

On Tue, Jun 20, 2023 at 5:05 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> All the addend_*_rel() functions calculate the instruction location in
> the same way.
>
> Factor out the similar code to the caller. Squash reloc_location() too.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  scripts/mod/modpost.c | 28 ++++++++++++----------------
>  1 file changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 6e0b8be32648..2551ac9d5bd3 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1256,16 +1256,9 @@ static void check_section_mismatch(struct module *mod, struct elf_info *elf,
>                                  tosec, taddr);
>  }
>
> -static unsigned int *reloc_location(struct elf_info *elf,
> -                                   Elf_Shdr *sechdr, Elf_Rela *r)
> -{
> -       return sym_get_data_by_offset(elf, sechdr->sh_info, r->r_offset);
> -}
> -
> -static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
> +static int addend_386_rel(uint32_t *location, Elf_Rela *r)
>  {
>         unsigned int r_typ = ELF_R_TYPE(r->r_info);
> -       unsigned int *location = reloc_location(elf, sechdr, r);
>
>         switch (r_typ) {
>         case R_386_32:
> @@ -1302,11 +1295,10 @@ static int32_t sign_extend32(int32_t value, int index)
>         return (int32_t)(value << shift) >> shift;
>  }
>
> -static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
> +static int addend_arm_rel(void *loc, struct elf_info *elf, Elf_Rela *r)
>  {
>         unsigned int r_typ = ELF_R_TYPE(r->r_info);
>         Elf_Sym *sym = elf->symtab_start + ELF_R_SYM(r->r_info);
> -       void *loc = reloc_location(elf, sechdr, r);
>         uint32_t inst, upper, lower, sign, j1, j2;
>         int32_t offset;
>
> @@ -1396,11 +1388,10 @@ static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
>         return 0;
>  }
>
> -static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
> +static int addend_mips_rel(uint32_t *location, Elf_Rela *r)
>  {
>         unsigned int r_typ = ELF_R_TYPE(r->r_info);
> -       unsigned int *location = reloc_location(elf, sechdr, r);
> -       unsigned int inst;
> +       uint32_t inst;
>
>         if (r_typ == R_MIPS_HI16)
>                 return 1;       /* skip this */
> @@ -1502,6 +1493,8 @@ static void section_rel(struct module *mod, struct elf_info *elf,
>                 return;
>
>         for (rel = start; rel < stop; rel++) {
> +               void *loc;
> +
>                 r.r_offset = TO_NATIVE(rel->r_offset);
>  #if KERNEL_ELFCLASS == ELFCLASS64
>                 if (elf->hdr->e_machine == EM_MIPS) {
> @@ -1519,17 +1512,20 @@ static void section_rel(struct module *mod, struct elf_info *elf,
>                 r_sym = ELF_R_SYM(r.r_info);
>  #endif
>                 r.r_addend = 0;
> +
> +               loc = sym_get_data_by_offset(elf, fsecndx, r.r_offset);

Can we compute `loc` only for the three machine types?

> +
>                 switch (elf->hdr->e_machine) {
>                 case EM_386:
> -                       if (addend_386_rel(elf, sechdr, &r))
> +                       if (addend_386_rel(loc, &r))
>                                 continue;
>                         break;
>                 case EM_ARM:
> -                       if (addend_arm_rel(elf, sechdr, &r))
> +                       if (addend_arm_rel(loc, elf, &r))
>                                 continue;
>                         break;
>                 case EM_MIPS:
> -                       if (addend_mips_rel(elf, sechdr, &r))
> +                       if (addend_mips_rel(loc, &r))
>                                 continue;
>                         break;
>                 default:
> --
> 2.39.2
>


-- 
Thanks,
~Nick Desaulniers