linux-kernel - Re: [PATCH] kbuild: Fix 'no symbols' warning when CONFIG_TRIM_UNUSD

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Date:   Sat, 14 Aug 2021 18:15:33 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Pitre <nico@...xnic.net>,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] kbuild: Fix 'no symbols' warning when
 CONFIG_TRIM_UNUSD_KSYMS=y

On 8/14/2021 4:41 PM, Masahiro Yamada wrote:
> When CONFIG_TRIM_UNUSED_KSYMS is enabled, I see some warnings like this:
> 
>    nm: arch/x86/entry/vdso/vdso32/note.o: no symbols
> 
> $NM (both GNU nm and llvm-nm) warns when no symbol is found in the
> object. Suppress the stderr.
> 
> Fixes: bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
> 
>   scripts/gen_ksymdeps.sh | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/gen_ksymdeps.sh b/scripts/gen_ksymdeps.sh
> index 1324986e1362..5493124e8ee6 100755
> --- a/scripts/gen_ksymdeps.sh
> +++ b/scripts/gen_ksymdeps.sh
> @@ -4,7 +4,10 @@
>   set -e
>   
>   # List of exported symbols
> -ksyms=$($NM $1 | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)
> +#
> +# If the object has no symbol, $NM warns 'no symbols'.
> +# Suppress the stdout.
> +ksyms=$($NM $1 2>/dev/null | sed -n 's/.*__ksym_marker_\(.*\)/\1/p' | tr A-Z a-z)
>   
>   if [ -z "$ksyms" ]; then
>   	exit 0
>