linux-kernel - Re: [PATCH 2/2] kallsyms: expand symbol name into comment for debugging

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Date:   Tue, 7 Mar 2023 10:57:47 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     linux-kbuild@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 2/2] kallsyms: expand symbol name into comment for debugging

On Mon, Mar 6, 2023 at 7:15 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> The assembler output of kallsyms.c is not meant for people to understand,
> and is generally not helpful when debugging "Inconsistent kallsyms data"
> warnings. I have previously struggled with these, but found it helpful
> to list which symbols changed between the first and second pass in the
> .tmp_vmlinux.kallsyms*.S files.
>
> As this file is preprocessed, it's possible to add a C-style multiline
> comment with the full type/name tuple.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> No idea if there is already a better way to debug this kind of problem,
> or if this causes a notable slowdown.
> ---
>  scripts/kallsyms.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index a239a87e7bec..ea1e3d3aaa6b 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -525,7 +525,8 @@ static void write_src(void)
>                                         table[i]->addr);
>                                 exit(EXIT_FAILURE);
>                         }
> -                       printf("\t.long\t%#x\n", (int)offset);
> +                       expand_symbol(table[i]->sym, table[i]->len, buf);
> +                       printf("\t.long\t%#x    /* %s */\n", (int)offset, buf);




This is printed only for base_relative,
but ia64 will go away sooner or later,
so this seems good to me.

Applied to linux-kbuild. Thanks.











>                 } else if (!symbol_absolute(table[i])) {
>                         output_address(table[i]->addr);
>                 } else {
> --
> 2.39.2
>


-- 
Best Regards
Masahiro Yamada