linux-kernel - Re: [PATCH bpf-next v1] scripts/gen-btf.sh: Use CONFIG

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Message-Id: <DFUH7UI3MM6F.1B30NTZ5NFSKR@garyguo.net>
Date: Wed, 21 Jan 2026 18:24:59 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "Ihor Solodrai" <ihor.solodrai@...ux.dev>, "Alexei Starovoitov"
 <ast@...nel.org>, "Daniel Borkmann" <daniel@...earbox.net>, "Andrii
 Nakryiko" <andrii@...nel.org>, "Martin KaFai Lau" <martin.lau@...ux.dev>
Cc: "Gary Guo" <gary@...yguo.net>, Thomas Weißschuh
 <linux@...ssschuh.net>, "Nathan Chancellor" <nathan@...nel.org>, "Nicolas
 Schier" <nsc@...nel.org>, <bpf@...r.kernel.org>,
 <linux-kbuild@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v1] scripts/gen-btf.sh: Use CONFIG_SHELL for
 execution

On Wed Jan 21, 2026 at 6:16 PM GMT, Ihor Solodrai wrote:
> According to the docs [1], kernel build scripts should be executed via
> CONFIG_SHELL, which is sh by default.
>
> Fixup gen-btf.sh to be runnable with sh, and use CONFIG_SHELL at every
> invocation site.
>
> See relevant discussion for context [2].
>
> [1] https://docs.kernel.org/kbuild/makefiles.html#script-invocation
> [2] https://lore.kernel.org/bpf/CAADnVQ+dxmSNoJAGb6xV89ffUCKXe5CJXovXZt22nv5iYFV5mw@mail.gmail.com/
>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@...ux.dev>

I can indeed build again when applying this on top of linux-next. Thanks.

Tested-by: Gary Guo <gary@...yguo.net>

You probably also want to carry some Reported-by, Suggested-by and Fixes tags here.

Best,
Gary

> ---
>  scripts/Makefile.modfinal | 2 +-
>  scripts/gen-btf.sh        | 8 ++++----
>  scripts/link-vmlinux.sh   | 2 +-
>  3 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index 422c56dc878e..adcbcde16a07 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -43,7 +43,7 @@ quiet_cmd_btf_ko = BTF [M] $@
>  	if [ ! -f $(objtree)/vmlinux ]; then				\
>  		printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
>  	else	\
> -		$(srctree)/scripts/gen-btf.sh --btf_base $(objtree)/vmlinux $@; \
> +		$(CONFIG_SHELL) $(srctree)/scripts/gen-btf.sh --btf_base $(objtree)/vmlinux $@; \
>  	fi;
>  
>  # Same as newer-prereqs, but allows to exclude specified extra dependencies
> diff --git a/scripts/gen-btf.sh b/scripts/gen-btf.sh
> index be21ccee3487..8ca96eb10a69 100755
> --- a/scripts/gen-btf.sh
> +++ b/scripts/gen-btf.sh
> @@ -1,4 +1,4 @@
> -#!/bin/bash
> +#!/bin/sh
>  # SPDX-License-Identifier: GPL-2.0
>  # Copyright (c) 2025 Meta Platforms, Inc. and affiliates.
>  #
> @@ -81,7 +81,7 @@ gen_btf_data()
>  
>  gen_btf_o()
>  {
> -	local btf_data=${ELF_FILE}.btf.o
> +	btf_data=${ELF_FILE}.btf.o
>  
>  	# Create ${btf_data} which contains just .BTF section but no symbols. Add
>  	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
> @@ -107,11 +107,11 @@ embed_btf_data()
>  	${OBJCOPY} --add-section .BTF=${ELF_FILE}.BTF ${ELF_FILE}
>  
>  	# a module might not have a .BTF_ids or .BTF.base section
> -	local btf_base="${ELF_FILE}.BTF.base"
> +	btf_base="${ELF_FILE}.BTF.base"
>  	if [ -f "${btf_base}" ]; then
>  		${OBJCOPY} --add-section .BTF.base=${btf_base} ${ELF_FILE}
>  	fi
> -	local btf_ids="${ELF_FILE}.BTF_ids"
> +	btf_ids="${ELF_FILE}.BTF_ids"
>  	if [ -f "${btf_ids}" ]; then
>  		${RESOLVE_BTFIDS} --patch_btfids ${btf_ids} ${ELF_FILE}
>  	fi
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index 08cd8e25c65c..16d6a048e07c 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -206,7 +206,7 @@ fi
>  
>  if is_enabled CONFIG_DEBUG_INFO_BTF; then
>  	info BTF .tmp_vmlinux1
> -	if ! ${srctree}/scripts/gen-btf.sh .tmp_vmlinux1; then
> +	if ! ${CONFIG_SHELL} ${srctree}/scripts/gen-btf.sh .tmp_vmlinux1; then
>  		echo >&2 "Failed to generate BTF for vmlinux"
>  		echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
>  		exit 1