If Makefile cannot find any of the vmlinux's in its VMLINUX_BTF_PATHS list, it tries to run btftool incorrectly, with VMLINUX_BTF unset:
bpftool btf dump file $(VMLINUX_BTF) format c
Such that the keyword 'format' is misinterpreted as the path to vmlinux. The resulting build error message is fairly cryptic:
GEN vmlinux.h Error: failed to load BTF from format: No such file or directory
This patch makes the failure reason clearer by yielding this instead:
Makefile:...: *** cannot find a vmlinux for VMLINUX_BTF at any of "{paths}". Stop.
Fixes: acbd06206bbb ("selftests/bpf: Add vmlinux.h selftest exercising tracing of syscalls") Cc: stable@vger.kernel.org # 5.7+ Signed-off-by: Kamal Mostafa kamal@canonical.com --- tools/testing/selftests/bpf/Makefile | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 542768f5195b..93ed34ef6e3f 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -196,6 +196,9 @@ $(BUILD_DIR)/libbpf $(BUILD_DIR)/bpftool $(BUILD_DIR)/resolve_btfids $(INCLUDE_D $(INCLUDE_DIR)/vmlinux.h: $(VMLINUX_BTF) | $(BPFTOOL) $(INCLUDE_DIR) ifeq ($(VMLINUX_H),) $(call msg,GEN,,$@) +ifeq ($(VMLINUX_BTF),) +$(error cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)") +endif $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@ else $(call msg,CP,,$@)