On Thu, Jan 16, 2020 at 5:23 AM Toke Høiland-Jørgensen toke@redhat.com wrote:
From: Toke Høiland-Jørgensen toke@redhat.com
The runqslower tool refuses to build without a file to read vmlinux BTF from. The build fails with an error message to override the location by setting the VMLINUX_BTF variable if autodetection fails. However, the Makefile doesn't actually work with that override - the error message is still emitted.
Fix this by including the value of VMLINUX_BTF in the expansion, and only emitting the error message if the *result* is empty. Also permit running 'make clean' even though no VMLINUX_BTF is set.
Fixes: 9c01546d26d2 ("tools/bpf: Add runqslower tool to tools/bpf") Signed-off-by: Toke Høiland-Jørgensen toke@redhat.com
tools/bpf/runqslower/Makefile | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile index cff2fbcd29a8..89fb7cd30f1a 100644 --- a/tools/bpf/runqslower/Makefile +++ b/tools/bpf/runqslower/Makefile @@ -10,12 +10,14 @@ CFLAGS := -g -Wall
# Try to detect best kernel BTF source KERNEL_REL := $(shell uname -r) -ifneq ("$(wildcard /sys/kernel/btf/vmlinux)","") -VMLINUX_BTF := /sys/kernel/btf/vmlinux -else ifneq ("$(wildcard /boot/vmlinux-$(KERNEL_REL))","") -VMLINUX_BTF := /boot/vmlinux-$(KERNEL_REL) -else -$(error "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly") +VMLINUX_BTF_PATHS := $(VMLINUX_BTF) /sys/kernel/btf/vmlinux /boot/vmlinux-$(KERNEL_REL) +VMLINUX_BTF_PATH := $(firstword $(wildcard $(VMLINUX_BTF_PATHS)))
If user specifies VMLINUX_BTF pointing to non-existing file, but the system has /sys/kernel/btf/vmlinux, the latter will still be used, which is a very surprising behavior.
Also MAKECMDGOALS feels like a fragile hack to me. How about we move this VMLINUX_BTF guessing (without $(error)) into vmlinux.h rule itself and use shell if conditional after it to check for file existance and print nice error. That way we'll be checking VMLINUX_BTF only when it's really needed.
+ifeq ("$(VMLINUX_BTF_PATH)","") +ifneq ($(MAKECMDGOALS),clean) +$(error Could not find kernel BTF file (tried: $(VMLINUX_BTF_PATHS)). \
Try setting $$VMLINUX_BTF)+endif endif
abs_out := $(abspath $(OUTPUT)) @@ -67,9 +69,9 @@ $(OUTPUT): $(call msg,MKDIR,$@) $(Q)mkdir -p $(OUTPUT)
-$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF) | $(OUTPUT) $(BPFTOOL) +$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF_PATH) | $(OUTPUT) $(BPFTOOL) $(call msg,GEN,$@)
$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF_PATH) format c > $@$(OUTPUT)/libbpf.a: | $(OUTPUT) $(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) \