linux-kernel - Re: [PATCH] kbuild: link vmlinux only once for CONFIG_TRIM_UNUSED

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Date:   Thu, 23 Jun 2022 12:50:19 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Pitre <nico@...xnic.net>
Subject: Re: [PATCH] kbuild: link vmlinux only once for CONFIG_TRIM_UNUSED_KSYMS
 (2nd attempt)

On Thu, Jun 23, 2022 at 12:12 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> If CONFIG_TRIM_UNUSED_KSYMS is enabled and the kernel is built from
> a pristine state, the vmlinux is linked twice.
>
> Commit 3fdc7d3fe4c0 ("kbuild: link vmlinux only once for
> CONFIG_TRIM_UNUSED_KSYMS") explains why this happens, but it did not fix
> the issue at all.
>
> Now I realized I had applied a wrong patch.
>
> In v1 patch [1], the autoksyms_recursive target correctly recurses to
> "$(MAKE) -f $(srctree)/Makefile autoksyms_recursive".
>
> In v2 patch [2], I accidentally dropped the diff line, and it recurses to
> "$(MAKE) -f $(srctree)/Makefile vmlinux".
>
> Restore the code I intended in v1.
>
> [1]: https://lore.kernel.org/linux-kbuild/1521045861-22418-8-git-send-email-yamada.masahiro@socionext.com/
> [2]: https://lore.kernel.org/linux-kbuild/1521166725-24157-8-git-send-email-yamada.masahiro@socionext.com/
>
> Fixes: 3fdc7d3fe4c0 ("kbuild: link vmlinux only once for CONFIG_TRIM_UNUSED_KSYMS")
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 513c1fbf7888..a3ff166c5035 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1141,7 +1141,7 @@ KBUILD_MODULES := 1
>
>  autoksyms_recursive: descend modules.order
>         $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \
> -         "$(MAKE) -f $(srctree)/Makefile vmlinux"
> +         "$(MAKE) -f $(srctree)/Makefile autoksyms_recursive"
>  endif
>
>  autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h)

Thanks for looking into this, Masahiro! I can confirm that this patch
fixes the issue with vmlinux getting linked twice in our use case.

Tested-by: Sami Tolvanen <samitolvanen@...gle.com>

Sami