linux-kernel - Re: [PATCH 24/27] modpost: generate linker script to collect symbol versions

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Date:   Thu, 28 Apr 2022 14:49:04 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Schier <nicolas@...sle.eu>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH 24/27] modpost: generate linker script to collect symbol versions

On Sun, Apr 24, 2022 at 12:10 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> Merge version CRCs per vmlinux or per module.
>
> These linker scripts will be fed to the final link stage.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  .gitignore            |  1 +
>  Makefile              |  1 +
>  scripts/mod/modpost.c | 27 +++++++++++++++++++++++++++
>  3 files changed, 29 insertions(+)
>
> diff --git a/.gitignore b/.gitignore
> index 265959544978..f9dad6b917e6 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -42,6 +42,7 @@
>  *.so.dbg
>  *.su
>  *.symtypes
> +*.symver.lds
>  *.symversions
>  *.tab.[ch]
>  *.tar
> diff --git a/Makefile b/Makefile
> index 235d68fa1470..0779db3d1c0c 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1859,6 +1859,7 @@ clean: $(clean-dirs)
>                 -o -name '*.c.[012]*.*' \
>                 -o -name '*.ll' \
>                 -o -name '*.gcno' \
> +               -o -name '*.symver.lds' \
>                 -o -name '*.*.symversions' \) -type f -print | xargs rm -f
>
>  # Generate tags for editors
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 43ab4f000ae3..ef779ada04c6 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -2577,6 +2577,30 @@ static void write_dump(const char *fname)
>         free(buf.p);
>  }
>
> +static void write_symversions_lds(struct module *mod)
> +{
> +       struct buffer buf = { };
> +       struct symbol *sym;
> +       char lds_file[PATH_MAX];
> +       int ret;
> +
> +       ret = snprintf(lds_file, sizeof(lds_file), "%s.symver.lds", mod->name);
> +       if (ret >= sizeof(lds_file)) {
> +               error("%s: too long path was truncated\n", lds_file);
> +               return;

If this exceptional case occurs, we should probably halt or return an
error code to main?

> +       }
> +
> +       list_for_each_entry(sym, &mod->exported_symbols, list) {
> +               if (!sym->crc_valid)
> +                       continue;
> +
> +               buf_printf(&buf, "__crc_%s = 0x%08x;\n", sym->name, sym->crc);
> +       }
> +
> +       write_if_changed(&buf, lds_file);
> +       free(buf.p);
> +}
> +
>  static void write_namespace_deps_files(const char *fname)
>  {
>         struct module *mod;
> @@ -2673,6 +2697,9 @@ int main(int argc, char **argv)
>                 char fname[PATH_MAX];
>                 int ret;
>
> +               if (modversions && !mod->from_dump)
> +                       write_symversions_lds(mod);
> +
>                 if (mod->is_vmlinux || mod->from_dump)
>                         continue;
>
> --
> 2.32.0
>


-- 
Thanks,
~Nick Desaulniers