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Date: Tue, 12 Jul 2022 19:32:00 +0800 From: Pu Lehui <pulehui@...wei.com> To: Quentin Monnet <quentin@...valent.com>, <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org> CC: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Jean-Philippe Brucker <jean-philippe@...aro.org> Subject: Re: [PATCH bpf-next 1/3] samples: bpf: Fix cross-compiling error by using bootstrap bpftool On 2022/7/12 18:11, Quentin Monnet wrote: > On 12/07/2022 04:08, Pu Lehui wrote: >> Currently, when cross compiling bpf samples, the host side cannot >> use arch-specific bpftool to generate vmlinux.h or skeleton. Since >> samples/bpf use bpftool for vmlinux.h, skeleton, and static linking >> only, we can use lightweight bootstrap version of bpftool to handle >> these, and it's always host-native. >> >> Signed-off-by: Pu Lehui <pulehui@...wei.com> >> Suggested-by: Andrii Nakryiko <andrii@...nel.org> >> --- >> samples/bpf/Makefile | 16 +++++++++++----- >> 1 file changed, 11 insertions(+), 5 deletions(-) >> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile >> index 5002a5b9a7da..57012b8259d2 100644 >> --- a/samples/bpf/Makefile >> +++ b/samples/bpf/Makefile >> @@ -282,12 +282,18 @@ $(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 := $(BPFTOOL_OUTPUT)/bootstrap/bpftool >> +ifeq ($(CROSS_COMPILE),) >> $(BPFTOOL): $(LIBBPF) $(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)/ >> + $(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../ \ >> + OUTPUT=$(BPFTOOL_OUTPUT)/ \ >> + LIBBPF_BOOTSTRAP_OUTPUT=$(LIBBPF_OUTPUT)/ \ >> + LIBBPF_BOOTSTRAP_DESTDIR=$(LIBBPF_DESTDIR)/ bootstrap >> +else >> +$(BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT) > > Thanks for this! Just trying to fully understand the details here. When > cross-compiling, you leave aside the dependency on target-arch-libbpf, > so that "make -C <bpftool-dir> bootstrap" rebuilds its own host-arch > libbpf, is this correct? > You're right. libbpf may does get out-of-sync. So the best way is to compile both arch-specific libbpf simultaneously, and then attach to bpftool. But it will make this job more complicated. Could we just add back $(LIBBPF) to handle this? >> + $(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../ \ >> + OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap >> +endif >> >> $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT): >> $(call msg,MKDIR,$@) > > . >
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