Date:   Fri, 27 Jan 2023 13:56:56 -0800
From:   William McVicker <willmcvicker@google.com>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>
Subject: Re: [PATCH v2] kbuild: do not automatically add -w option to modpost
Message-ID: <Y9RIqNnzkhfsm0dC@google.com>
References: <20230126022643.3664548-1-masahiroy@kernel.org>
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On 01/26/2023, Masahiro Yamada wrote:
> When there is a missing input file (vmlinux.o or Module.symvers), you
> are likely to get a ton of unresolved symbols.
> 
> Currently, Kbuild automatically adds the -w option to allow module builds
> to continue with warnings instead of errors.
> 
> This may not be what the user expects because it is generally more useful
> to catch all possible issues at build time instead of at run time.
> 
> Let's not do what the user did not ask.
> 
> If you still want to build modules anyway, you can proceed by explicitly
> setting KBUILD_MODPOST_WARN=1. Since you may miss a real issue, you need
> to be aware of what you are doing.
> 
> Suggested-by: William McVicker <willmcvicker@google.com>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
> Changes in v2:
>   - Fix the closing parenthesis
> 
>  scripts/Makefile.modpost | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index 43343e13c542..0980c58d8afc 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -121,16 +121,14 @@ modpost-args += -e $(addprefix -i , $(KBUILD_EXTRA_SYMBOLS))
>  
>  endif # ($(KBUILD_EXTMOD),)
>  
> -ifneq ($(missing-input),)
> -modpost-args += -w
> -endif
> -
>  quiet_cmd_modpost = MODPOST $@
>        cmd_modpost = \
>  	$(if $(missing-input), \
>  		echo >&2 "WARNING: $(missing-input) is missing."; \
>  		echo >&2 "         Modules may not have dependencies or modversions."; \
> -		echo >&2 "         You may get many unresolved symbol warnings.";) \
> +		echo >&2 "         You may get many unresolved symbol errors."; \
> +		echo >&2 "         You can set KBUILD_MODPOST_WARN=1 to turn errors into warning"; \
> +		echo >&2 "         if you want to proceed at your own risk.";) \
>  	$(MODPOST) $(modpost-args)
>  
>  targets += $(output-symdump)
> -- 
> 2.34.1
> 

Thanks for putting this together. I verified it's working as expected
for me. Feel free to add:

Tested-by: Will McVicker <willmcvicker@google.com>

Regards,
Will