Hi Bjorn,

Thanks for the patch, I've tested it and it works for me.

I have a minor suggestion but otherwise happy to see this getting fixed.

On 10/02/2023 08:43, Björn Töpel wrote:

From: Björn Töpel bjorn@rivosinc.com

When the BPF selftests are cross-compiled, only the a host version of bpftool is built. This version of bpftool is used to generate various intermediates, e.g., skeletons.

The test runners are also using bpftool. The Makefile will symlink bpftool from the selftest/bpf root, where the test runners will look for the tool:

| ... | $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \ | $(OUTPUT)/$(if $2,$2/)bpftool

There are two issues for cross-compilation builds:

1. There is no native (cross-compilation target) build of bpftool
2. The bootstrap variant of bpftool is never cross-compiled (by design)

Make sure that a native/cross-compiled version of bpftool is built, and if CROSS_COMPILE is set, symlink to the native/non-bootstrap version.

Signed-off-by: Björn Töpel bjorn@rivosinc.com

tools/testing/selftests/bpf/Makefile | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index b2eb3201b85a..b706750f71e2 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -157,8 +157,9 @@ $(notdir $(TEST_GEN_PROGS) \ $(TEST_CUSTOM_PROGS)): %: $(OUTPUT)/% ; # sort removes libbpf duplicates when not cross-building -MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf \

•       $(HOST_BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/resolve_btfids      \
  

+MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf \

•       $(BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/bpftool		\
  

•       $(HOST_BUILD_DIR)/resolve_btfids				\
      $(RUNQSLOWER_OUTPUT) $(INCLUDE_DIR))
  

$(MAKE_DIRS): $(call msg,MKDIR,,$@) @@ -208,6 +209,14 @@ $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_tes $(Q)cp bpf_testmod/bpf_testmod.ko $@ DEFAULT_BPFTOOL := $(HOST_SCRATCH_DIR)/sbin/bpftool +ifneq ($(CROSS_COMPILE),) +CROSS_BPFTOOL := $(SCRATCH_DIR)/sbin/bpftool +TRUNNER_BPFTOOL := $(CROSS_BPFTOOL) +USE_BOOTSTRAP := "" +else +TRUNNER_BPFTOOL := $(DEFAULT_BPFTOOL) +USE_BOOTSTRAP := "bootstrap" +endif $(OUTPUT)/runqslower: $(BPFOBJ) | $(DEFAULT_BPFTOOL) $(RUNQSLOWER_OUTPUT) $(Q)$(MAKE) $(submake_extras) -C $(TOOLSDIR)/bpf/runqslower \

...

-TEST_GEN_PROGS_EXTENDED += $(DEFAULT_BPFTOOL) +TEST_GEN_PROGS_EXTENDED += $(TRUNNER_BPFTOOL)

Ensure the target arch bpftool is copied into the kselftest_bpf_install dir by selftests/lib.mk instead of always the default/host version.

Thanks, Zach

@@ -255,6 +264,18 @@ $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) \ LIBBPF_DESTDIR=$(HOST_SCRATCH_DIR)/ \ prefix= DESTDIR=$(HOST_SCRATCH_DIR)/ install-bin +ifneq ($(CROSS_COMPILE),) +$(CROSS_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) \

•     $(BPFOBJ) | $(BUILD_DIR)/bpftool
  

• $(Q)$(MAKE) $(submake_extras) -C $(BPFTOOLDIR) \

•     ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE)			\
  

•     EXTRA_CFLAGS='-g -O0'					\
  

•     OUTPUT=$(BUILD_DIR)/bpftool/				\
  

•     LIBBPF_OUTPUT=$(BUILD_DIR)/libbpf/				\
  

•     LIBBPF_DESTDIR=$(SCRATCH_DIR)/				\
  

•     prefix= DESTDIR=$(SCRATCH_DIR)/ install-bin
  

+endif

all: docs docs: @@ -518,11 +539,12 @@ endif $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TESAT_OBJS) \ $(TRUNNER_EXTRA_OBJS) $$(BPFOBJ) \ $(RESOLVE_BTFIDS) related to \

• 	     $(TRUNNER_BPFTOOL)				\
       | $(TRUNNER_BINARY)-extras
  

  $$(call msg,BINARY,,$$@) $(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@ $(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@

• $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \

• $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/$(USE_BOOTSTRAP)/bpftool > $(OUTPUT)/$(if $2,$2/)bpftool

endef

base-commit: 06744f24696e1e7598412c3df61a538b57ebec22