In bpftool's Makefile, libbpf has a FORCE dependency, to make sure we
rebuild it in case its source files changed. Let's instead make the
rebuild depend on the source files directly, through a call to the
"$(wildcard ...)" function. This avoids descending into libbpf's
directory if there is nothing to update.
Do the same for the bootstrap libbpf version.
This results in a slightly faster operation and less verbose output when
running make a second time in bpftool's directory.
Before:
Auto-detecting system features:
... libbfd: [ on ]
... disassembler-four-args: [ on ]
... zlib: [ on ]
... libcap: [ on ]
... clang-bpf-co-re: [ on ]
make[1]: Entering directory '/root/dev/linux/tools/lib/bpf'
make[1]: Entering directory '/root/dev/linux/tools/lib/bpf'
make[1]: Nothing to be done for 'install_headers'.
make[1]: Leaving directory '/root/dev/linux/tools/lib/bpf'
make[1]: Leaving directory '/root/dev/linux/tools/lib/bpf'
After:
Auto-detecting system features:
... libbfd: [ on ]
... disassembler-four-args: [ on ]
... zlib: [ on ]
... libcap: [ on ]
... clang-bpf-co-re: [ on ]
Other ways to clean up the output could be to pass the "-s" option, or
to redirect the output to >/dev/null, when calling make recursively to
descend into libbpf's directory. However, this would suppress some
useful output if something goes wrong during the build. A better
alternative would be to pass "--no-print-directory" to the recursive
make, but that would still leave us with some noise for
"install_headers". Skipping the descent into libbpf's directory if no
source file has changed works best, and seems the most logical option
overall.
Reported-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
---
tools/bpf/bpftool/Makefile | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 2c510293f32b..4acec74f459b 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -43,7 +43,7 @@ endif
$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT):
$(QUIET_MKDIR)mkdir -p $@
-$(LIBBPF): FORCE | $(LIBBPF_OUTPUT)
+$(LIBBPF): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_OUTPUT)
$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) \
DESTDIR=$(LIBBPF_DESTDIR) prefix= $(LIBBPF) install_headers
@@ -51,7 +51,7 @@ $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h $(LIBBPF)
$(call QUIET_INSTALL, $@)
$(Q)install -m 644 -t $(LIBBPF_HDRS_DIR) $<
-$(LIBBPF_BOOTSTRAP): FORCE | $(LIBBPF_BOOTSTRAP_OUTPUT)
+$(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
ARCH= CC=$(HOSTCC) LD=$(HOSTLD) $@
--
2.30.2
