On Tue, Jul 12, 2022 at 4:32 AM Pu Lehui <pulehui@xxxxxxxxxx> wrote: > > > > 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@xxxxxxxxxx> > >> Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > >> --- > >> 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? > Maybe let's keep it simple and let bpftool's Makefile deal with cross-compile issue and building its own libbpf? So just request bootstrap, but not try to share libbpf between samples/bpf and bpftool? Especially that is this "samples", such complexity in Makefile seems like a micro-optimization. > >> + $(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../ \ > >> + OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap > >> +endif > >> > >> $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT): > >> $(call msg,MKDIR,$@) > > > > . > >
