linux-kernel - Re: [PATCH 2/2] kbuild: remove libelf checks from top Makefile

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Date:   Wed, 12 May 2021 12:36:15 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Martin KaFai Lau <kafai@...com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/2] kbuild: remove libelf checks from top Makefile

On Tue, May 11, 2021 at 11:52 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> I do not see a good reason why only the libelf development package must
> be so carefully checked.
>
> Kbuild generally does not check host tools or libraries.
>
> For example, x86_64 defconfig fails to build with no libssl development
> package installed.
>
> scripts/extract-cert.c:21:10: fatal error: openssl/bio.h: No such file or directory
>    21 | #include <openssl/bio.h>
>       |          ^~~~~~~~~~~~~~~
>
> To solve the build error, you need to install libssl-dev or openssl-devel
> package, depending on your distribution.
>
> 'apt-file search', 'dnf provides', etc. is your frined to find a proper
> package to install.
>
> This commit removes all the libelf checks from the top Makefile.
>
> If libelf is missing, objtool will fail to build in a similar pattern:
>
> .../linux/tools/objtool/include/objtool/elf.h:10:10: fatal error: gelf.h: No such file or directory
>    10 | #include <gelf.h>
>
> You need to install libelf-dev, libelf-devel, or elfutils-libelf-devel
> to proceed.
>
> Another remarkable change is, CONFIG_STACK_VALIDATION (without
> CONFIG_UNWINDER_ORC) previously continued to build with a warning,
> but now it will treat missing libelf as an error.
>
> This is just a one-time installation, so it should not matter to break
> a build and make a user install the package.
>
> BTW, the traditional way to handle such checks is autotool, but according
> to [1], I do not expect the kernel build would have similar scripting
> like './configure' does.
>
> [1]: https://lore.kernel.org/lkml/CA+55aFzr2HTZVOuzpHYDwmtRJLsVzE-yqg2DHpHi_9ePsYp5ug@mail.gmail.com/
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>

resolve_btfids part looks good to me:

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>  Makefile                  | 78 +++++++++++----------------------------
>  scripts/Makefile.build    |  2 -
>  scripts/Makefile.modfinal |  2 -
>  3 files changed, 22 insertions(+), 60 deletions(-)
>

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