Re: [PATCH v3] scripts: check-function-names: propagate nm failures

[Nathan Chancellor <nathan@kernel.org>]

Hi Hamdy,

On Wed, Nov 04, 2026 at 01:07:33PM +0100, Hamdy Abou El Anein wrote:
> From: Hamdy Abou El Anein <hamdy.aea@protonmail.com>
> 
> The symbol-name check pipes nm through awk and grep. If nm cannot read
> an object file, its failure status is lost and the script reports
> success without checking any symbols.

If nm fails because vmlinux.o is malformed, surely that means that $(LD)
is going to choke on it too? This feels like unnecessary complication
and hardening for little gain. Were you able to reproduce a situation
where $(NM) failed but the rest of the build succeeded?

> Keep nm output streaming while carrying its exit status through the
> filter. This avoids buffering the full vmlinux.o symbol table in a
> shell variable during the serial kernel link, as the v2 did.

Just a work of advice for the future, avoid mentioning revisions within
the commit message, they won't make sense once the patch is applied.
Place differential notes below the '---' after your signoff and make
sure the commit message makes sense on its own.

> Tested with a malformed object (failure), a valid object (success), an
> object defining startup (failure), and a synthetic large nm stream
> (success).
> 
> AI assistance: ChatGPT/Codex identified the issue and prepared the
> change, commit message and executable regression tests.
> 
> Signed-off-by: Hamdy Abou El Anein <hamdy.aea@protonmail.com>
> ---
>  scripts/check-function-names.sh | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/check-function-names.sh b/scripts/check-function-names.sh
> index 94883e690627..b25e630cc594 100755
> --- a/scripts/check-function-names.sh
> +++ b/scripts/check-function-names.sh
> @@ -13,9 +13,28 @@ if [ ! -f "$objfile" ]; then
>  	exit 1
>  fi
>  
> -bad_symbols=$(${NM:-nm} -p "$objfile" | awk '$2 ~ /^[TtWw]$/ {print $3}' |
> -	      grep -E '^(startup|exit|split|unlikely|hot|unknown)(\.|$)')
> -
> +# Keep nm output streaming while preserving its exit status.
> +bad_symbols=$(
> +	{
> +		${NM:-nm} -p "$objfile"
> +		nm_status=$?
> +		printf '\n#nm_status %s\n' "$nm_status"
> +	} |
> +	awk '
> +		$1 == "#nm_status" {
> +			if ($2 != 0)
> +				nm_failed = 1
> +			next
> +		}
> +		$2 ~ /^[TtWw]$/ && $3 ~ /^(startup|exit|split|unlikely|hot|unknown)(\.|$)/ {
> +			print $3
> +		}
> +		END {
> +			if (nm_failed)
> +				exit 1
> +		}
> +	'
> +) || exit 1
>  if [ -n "$bad_symbols" ]; then
>  	echo "$bad_symbols" | while read -r sym; do
>  		echo "$objfile: error: $sym() function name creates ambiguity with -ffunction-sections" >&2
> -- 
> 2.56.0
> 

-- 
Cheers,
Nathan