linux-kernel - Re: [PATCH v4 bpf-next 3/5] kbuild: build kernel module BTFs if BTF is enabled and pahole supports it

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Message-ID: <f52c83a9-c350-5ba8-e178-10a0d7d0fed6@gmail.com>
Date:   Mon, 16 Nov 2020 20:44:15 -0700
From:   David Ahern <dsahern@...il.com>
To:     Andrii Nakryiko <andrii@...nel.org>
Cc:     kernel-team@...com, linux-kernel@...r.kernel.org,
        rafael@...nel.org, jeyu@...nel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net
Subject: Re: [PATCH v4 bpf-next 3/5] kbuild: build kernel module BTFs if BTF
 is enabled and pahole supports it

On 11/9/20 6:19 PM, Andrii Nakryiko wrote:
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index d7a7bc3b6098..1e78faaf20a5 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -274,6 +274,15 @@ config DEBUG_INFO_BTF
>  	  Turning this on expects presence of pahole tool, which will convert
>  	  DWARF type info into equivalent deduplicated BTF type info.
>  
> +config PAHOLE_HAS_SPLIT_BTF
> +	def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")
> +
> +config DEBUG_INFO_BTF_MODULES
> +	def_bool y
> +	depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
> +	help
> +	  Generate compact split BTF type information for kernel modules.
> +
>  config GDB_SCRIPTS
>  	bool "Provide GDB scripts for kernel debugging"
>  	help

Thank you for adding a config option for this feature vs bumping the
required pahole version in scripts/link-vmlinux.sh. This is a much more
friendly way of handling kernel features that require support from build
tools.