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References: <20230514152739.962109-1-masahiroy@kernel.org> <20230514152739.962109-8-masahiroy@kernel.org>
In-Reply-To: <20230514152739.962109-8-masahiroy@kernel.org>
From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Wed, 17 May 2023 13:55:45 -0700
Message-ID: <CAKwvOdnve7EAPzdTy1eMnGwYgXpNj+dFAwB-t+7PFASDiaM_iw@mail.gmail.com>
Subject: Re: [PATCH v5 07/21] modpost: squash extable_mismatch_handler() into default_mismatch_handler()
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        Nathan Chancellor <nathan@kernel.org>,
        Nicolas Pitre <npitre@baylibre.com>,
        Nicolas Schier <nicolas@fjasle.eu>
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On Sun, May 14, 2023 at 8:28=E2=80=AFAM Masahiro Yamada <masahiroy@kernel.o=
rg> wrote:
>
> Merging these two reduces several lines of code. The extable section
> mismatch is already distinguished by EXTABLE_TO_NON_TEXT.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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

> ---
>
>  scripts/mod/modpost.c | 84 ++++++++++++++-----------------------------
>  1 file changed, 26 insertions(+), 58 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 0bda2f22c985..49357a716519 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -881,27 +881,14 @@ enum mismatch {
>   * targeting sections in this array (white-list).  Can be empty.
>   *
>   * @mismatch: Type of mismatch.
> - *
> - * @handler: Specific handler to call when a match is found.  If NULL,
> - * default_mismatch_handler() will be called.
> - *
>   */
>  struct sectioncheck {
>         const char *fromsec[20];
>         const char *bad_tosec[20];
>         const char *good_tosec[20];
>         enum mismatch mismatch;
> -       void (*handler)(const char *modname, struct elf_info *elf,
> -                       const struct sectioncheck* const mismatch,
> -                       Elf_Rela *r, Elf_Sym *sym, const char *fromsec);
> -
>  };
>
> -static void extable_mismatch_handler(const char *modname, struct elf_inf=
o *elf,
> -                                    const struct sectioncheck* const mis=
match,
> -                                    Elf_Rela *r, Elf_Sym *sym,
> -                                    const char *fromsec);
> -
>  static const struct sectioncheck sectioncheck[] =3D {
>  /* Do not reference init/exit code/data from
>   * normal code and data
> @@ -974,7 +961,6 @@ static const struct sectioncheck sectioncheck[] =3D {
>         .bad_tosec =3D { ".altinstr_replacement", NULL },
>         .good_tosec =3D {ALL_TEXT_SECTIONS , NULL},
>         .mismatch =3D EXTABLE_TO_NON_TEXT,
> -       .handler =3D extable_mismatch_handler,
>  }
>  };
>
> @@ -1255,60 +1241,42 @@ static void default_mismatch_handler(const char *=
modname, struct elf_info *elf,
>                      modname, tosym, tosec);
>                 break;
>         case EXTABLE_TO_NON_TEXT:
> -               fatal("There's a special handler for this mismatch type, =
we should never get here.\n");
> +               warn("%s(%s+0x%lx): Section mismatch in reference to the =
%s:%s\n",
> +                    modname, fromsec, (long)r->r_offset, tosec, tosym);
> +
> +               if (match(tosec, mismatch->bad_tosec))
> +                       fatal("The relocation at %s+0x%lx references\n"
> +                             "section \"%s\" which is black-listed.\n"
> +                             "Something is seriously wrong and should be=
 fixed.\n"
> +                             "You might get more information about where=
 this is\n"
> +                             "coming from by using scripts/check_extable=
.sh %s\n",
> +                             fromsec, (long)r->r_offset, tosec, modname)=
;
> +               else if (is_executable_section(elf, get_secindex(elf, sym=
)))
> +                       warn("The relocation at %s+0x%lx references\n"
> +                            "section \"%s\" which is not in the list of\=
n"
> +                            "authorized sections.  If you're adding a ne=
w section\n"
> +                            "and/or if this reference is valid, add \"%s=
\" to the\n"
> +                            "list of authorized sections to jump to on f=
ault.\n"
> +                            "This can be achieved by adding \"%s\" to\n"
> +                            "OTHER_TEXT_SECTIONS in scripts/mod/modpost.=
c.\n",
> +                            fromsec, (long)r->r_offset, tosec, tosec, to=
sec);
> +               else
> +                       error("%s+0x%lx references non-executable section=
 '%s'\n",
> +                             fromsec, (long)r->r_offset, tosec);
>                 break;
>         }
>  }
>
> -static void extable_mismatch_handler(const char* modname, struct elf_inf=
o *elf,
> -                                    const struct sectioncheck* const mis=
match,
> -                                    Elf_Rela* r, Elf_Sym* sym,
> -                                    const char *fromsec)
> -{
> -       const char* tosec =3D sec_name(elf, get_secindex(elf, sym));
> -       Elf_Sym *tosym =3D find_elf_symbol(elf, r->r_addend, sym);
> -       const char *tosym_name =3D sym_name(elf, tosym);
> -
> -       sec_mismatch_count++;
> -
> -       warn("%s(%s+0x%lx): Section mismatch in reference to the %s:%s\n"=
,
> -            modname, fromsec, (long)r->r_offset, tosec, tosym_name);
> -
> -       if (match(tosec, mismatch->bad_tosec))
> -               fatal("The relocation at %s+0x%lx references\n"
> -                     "section \"%s\" which is black-listed.\n"
> -                     "Something is seriously wrong and should be fixed.\=
n"
> -                     "You might get more information about where this is=
\n"
> -                     "coming from by using scripts/check_extable.sh %s\n=
",
> -                     fromsec, (long)r->r_offset, tosec, modname);
> -       else if (is_executable_section(elf, get_secindex(elf, sym)))
> -               warn("The relocation at %s+0x%lx references\n"
> -                    "section \"%s\" which is not in the list of\n"
> -                    "authorized sections.  If you're adding a new sectio=
n\n"
> -                    "and/or if this reference is valid, add \"%s\" to th=
e\n"
> -                    "list of authorized sections to jump to on fault.\n"
> -                    "This can be achieved by adding \"%s\" to\n"
> -                    "OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.\n",
> -                    fromsec, (long)r->r_offset, tosec, tosec, tosec);
> -       else
> -               error("%s+0x%lx references non-executable section '%s'\n"=
,
> -                     fromsec, (long)r->r_offset, tosec);
> -}
> -
>  static void check_section_mismatch(const char *modname, struct elf_info =
*elf,
>                                    Elf_Rela *r, Elf_Sym *sym, const char =
*fromsec)
>  {
>         const char *tosec =3D sec_name(elf, get_secindex(elf, sym));
>         const struct sectioncheck *mismatch =3D section_mismatch(fromsec,=
 tosec);
>
> -       if (mismatch) {
> -               if (mismatch->handler)
> -                       mismatch->handler(modname, elf,  mismatch,
> -                                         r, sym, fromsec);
> -               else
> -                       default_mismatch_handler(modname, elf, mismatch,
> -                                                r, sym, fromsec);
> -       }
> +       if (!mismatch)
> +               return;
> +
> +       default_mismatch_handler(modname, elf, mismatch, r, sym, fromsec)=
;
>  }
>
>  static unsigned int *reloc_location(struct elf_info *elf,
> --
> 2.39.2
>


--=20
Thanks,
~Nick Desaulniers