linux-kernel - Re: [PATCH v6 01/20] Revert "modpost: skip ELF local symbols during section mismatch check"

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Message-ID: <CAKwvOd=Bq2j4-t9VXvNLodcZEM3P_m=z-NSkegR-gbHSr1=qnA@mail.gmail.com>
Date:   Mon, 22 May 2023 10:42:27 -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 v6 01/20] Revert "modpost: skip ELF local symbols during
 section mismatch check"

On Sun, May 21, 2023 at 9:05 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> This reverts commit a4d26f1a0958bb1c2b60c6f1e67c6f5d43e2647b.

a4d26f1a0958 mentions -fsection-anchors which I see used in:
arch/arc/Makefile
41:cflags-y += -fsection-anchors

Though based on the below, it looks like is_mapping_symbol() will
catch this case.

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> The variable 'fromsym' never starts with ".L" since commit 87e5b1e8f257
> ("module: Sync code of is_arm_mapping_symbol()").
>
> In other words, Pattern 6 is now dead code.
>
> Previously, the .LANCHOR1 hid the symbols listed in Pattern 2, but
> a4d26f1a0958 was a cheesy workaround.
>
> 87e5b1e8f257 addressed the issue in a much better way.

is_arm_mapping_symbol is gone from scripts/mod/modpost.c. It was moved
then renamed to is_mapping_symbol.  Maybe not relevant for the commit
message, but maybe helpful to other reviewers.

commit 987d2e0aaa55 ("module: Move is_arm_mapping_symbol() to module_symbol.h")
commit 0a3bf86092c3 ("module: Ignore L0 and rename is_arm_mapping_symbol()")


>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  scripts/mod/modpost.c | 12 ------------
>  1 file changed, 12 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 0d2c2aff2c03..71de14544432 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1034,14 +1034,6 @@ static const struct sectioncheck *section_mismatch(
>   *   fromsec = text section
>   *   refsymname = *.constprop.*
>   *
> - * Pattern 6:
> - *   Hide section mismatch warnings for ELF local symbols.  The goal
> - *   is to eliminate false positive modpost warnings caused by
> - *   compiler-generated ELF local symbol names such as ".LANCHOR1".
> - *   Autogenerated symbol names bypass modpost's "Pattern 2"
> - *   whitelisting, which relies on pattern-matching against symbol
> - *   names to work.  (One situation where gcc can autogenerate ELF
> - *   local symbols is when "-fsection-anchors" is used.)
>   **/
>  static int secref_whitelist(const struct sectioncheck *mismatch,
>                             const char *fromsec, const char *fromsym,
> @@ -1092,10 +1084,6 @@ static int secref_whitelist(const struct sectioncheck *mismatch,
>             match(fromsym, optim_symbols))
>                 return 0;
>
> -       /* Check for pattern 6 */
> -       if (strstarts(fromsym, ".L"))
> -               return 0;
> -
>         return 1;
>  }
>
> --
> 2.39.2
>


-- 
Thanks,
~Nick Desaulniers