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From:   Song Liu <songliubraving@fb.com>
To:     Pu Lehui <pulehui@huawei.com>
CC:     bpf <bpf@vger.kernel.org>, Networking <netdev@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>, Martin Lau <kafai@fb.com>,
        Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>
Subject: Re: [PATCH bpf-next] samples: bpf: Fix cross-compiling error about
 bpftool
Thread-Topic: [PATCH bpf-next] samples: bpf: Fix cross-compiling error about
 bpftool
Thread-Index: AQHYkga7HcKsl6ueBUOt13UUFx+YDK1zRwcA
Date:   Thu, 7 Jul 2022 19:12:47 +0000
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References: <20220707140811.603590-1-pulehui@huawei.com>
In-Reply-To: <20220707140811.603590-1-pulehui@huawei.com>
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> On Jul 7, 2022, at 7:08 AM, Pu Lehui <pulehui@huawei.com> wrote:
> 
> Currently, when cross compiling bpf samples, the host side
> cannot use arch-specific bpftool to generate vmlinux.h or
> skeleton. We need to compile the bpftool with the host
> compiler.
> 
> Signed-off-by: Pu Lehui <pulehui@huawei.com>
> ---
> samples/bpf/Makefile | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 5002a5b9a7da..fe54a8c8f312 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -1,4 +1,5 @@
> # SPDX-License-Identifier: GPL-2.0
> +-include tools/scripts/Makefile.include

Why do we need the -include here? 

Thanks,
Song

> 
> BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
> TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools
> @@ -283,11 +284,10 @@ $(LIBBPF): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU
> BPFTOOLDIR := $(TOOLS_PATH)/bpf/bpftool
> BPFTOOL_OUTPUT := $(abspath $(BPF_SAMPLES_PATH))/bpftool
> BPFTOOL := $(BPFTOOL_OUTPUT)/bpftool
> -$(BPFTOOL): $(LIBBPF) $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT)
> +$(BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT)
> 	    $(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../ \
> -		OUTPUT=$(BPFTOOL_OUTPUT)/ \
> -		LIBBPF_OUTPUT=$(LIBBPF_OUTPUT)/ \
> -		LIBBPF_DESTDIR=$(LIBBPF_DESTDIR)/
> +		ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) \
> +		OUTPUT=$(BPFTOOL_OUTPUT)/
> 
> $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):
> 	$(call msg,MKDIR,$@)
> -- 
> 2.25.1
>