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?
+ $(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../ \
+ OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap
+endif
$(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):
$(call msg,MKDIR,$@)
.
