Re: [PATCH 04/16] net: bpfilter: use 'userprogs' syntax to build bpfilter_umh

From: Michal Kubecek <mkubecek@suse.cz>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild@vger.kernel.org, bpf@vger.kernel.org,
	Sam Ravnborg <sam@ravnborg.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andriin@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>, Martin KaFai Lau <kafai@fb.com>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH 04/16] net: bpfilter: use 'userprogs' syntax to build bpfilter_umh
Date: Mon, 8 Jun 2020 13:56:28 +0200	[thread overview]
Message-ID: <20200608115628.osizkpo76cgn2ci7@lion.mk-sys.cz> (raw)
In-Reply-To: <20200423073929.127521-5-masahiroy@kernel.org>

On Thu, Apr 23, 2020 at 04:39:17PM +0900, Masahiro Yamada wrote:
> The user mode helper should be compiled for the same architecture as
> the kernel.
> 
> This Makefile reuses the 'hostprogs' syntax by overriding HOSTCC with CC.
> 
> Now that Kbuild provides the syntax 'userprogs', use it to fix the
> Makefile mess.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Reported-by: kbuild test robot <lkp@intel.com>
> ---
> 
>  net/bpfilter/Makefile | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
> index 36580301da70..6ee650c6badb 100644
> --- a/net/bpfilter/Makefile
> +++ b/net/bpfilter/Makefile
> @@ -3,17 +3,14 @@
>  # Makefile for the Linux BPFILTER layer.
>  #
>  
> -hostprogs := bpfilter_umh
> +userprogs := bpfilter_umh
>  bpfilter_umh-objs := main.o
> -KBUILD_HOSTCFLAGS += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi
> -HOSTCC := $(CC)
> +user-ccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi
>  
> -ifeq ($(CONFIG_BPFILTER_UMH), y)
> -# builtin bpfilter_umh should be compiled with -static
> +# builtin bpfilter_umh should be linked with -static
>  # since rootfs isn't mounted at the time of __init
>  # function is called and do_execv won't find elf interpreter
> -KBUILD_HOSTLDFLAGS += -static
> -endif
> +bpfilter_umh-ldflags += -static
>  
>  $(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh

Hello,

I just noticed that this patch (now in mainline as commit 8a2cc0505cc4)
drops the test if CONFIG_BPFILTER_UMH is "y" so that -static is now
passed to the linker even if bpfilter_umh is built as a module which
wasn't the case in v5.7.

This is not mentioned in the commit message and the comment still says
"*builtin* bpfilter_umh should be linked with -static" so this change
doesn't seem to be intentional. Did I miss something?

Michal Kubecek