linux-kernel - Re: [PATCH v3 2/3] samples/bpf: fix broken vmlinux path for VMLINUX

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Message-ID: <CAEf4BzY7yML7=C8Z+T8_RdzZt1Ab+rwK0g7b0GKf99T-uaGpxQ@mail.gmail.com>
Date: Wed, 5 Feb 2025 16:54:29 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Jinghao Jia <jinghao7@...inois.edu>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Jiri Kosina <jikos@...nel.org>, 
	Benjamin Tissoires <bentiss@...nel.org>, Masahiro Yamada <masahiroy@...nel.org>, 
	Nicolas Schier <n.schier@....de>, Ruowen Qin <ruqin@...hat.com>, bpf@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v3 2/3] samples/bpf: fix broken vmlinux path for VMLINUX_BTF

On Mon, Feb 3, 2025 at 12:55 AM Jinghao Jia <jinghao7@...inois.edu> wrote:
>
> Commit 13b25489b6f8 ("kbuild: change working directory to external
> module directory with M=") changed kbuild working directory of bpf
> sample programs to samples/bpf, which broke the vmlinux path for
> VMLINUX_BTF, as the Makefiles assume the current work directory to be
> the kernel output directory and use a relative path (i.e., ./vmlinux):
>
>   Makefile:316: *** Cannot find a vmlinux for VMLINUX_BTF at any of "  /path/to/linux/samples/bpf/vmlinux", build the kernel or set VMLINUX_BTF like "VMLINUX_BTF=/sys/kernel/btf/vmlinux" or VMLINUX_H variable.  Stop.
>
> Correctly refer to the kernel output directory using $(objtree).
>
> Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
> Tested-by: Ruowen Qin <ruqin@...hat.com>
> Signed-off-by: Jinghao Jia <jinghao7@...inois.edu>
> ---
>  samples/bpf/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>

Applied this patch to bpf-next. I presume HID ones will go through the
respective tree. Thanks!

> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index dd9944a97b7e..5b632635e00d 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -307,7 +307,7 @@ $(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check=
>
>  VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux))                                \
>                      $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)) \
> -                    $(abspath ./vmlinux)
> +                    $(abspath $(objtree)/vmlinux)
>  VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
>
>  $(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
> --
> 2.48.1
>