diff mbox series

[bpf-next,2/3] bpftool: do not FORCE-build libbpf

Message ID 20211009210341.6291-3-quentin@isovalent.com (mailing list archive)
State Accepted
Delegated to: BPF
Headers show
Series fixes for bpftool's Makefile | expand

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netdev/fixes_present success Fixes tag not required for -next series
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for bpf-next
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netdev/cc_maintainers warning 10 maintainers not CCed: irogers@google.com llvm@lists.linux.dev songliubraving@fb.com yhs@fb.com ndesaulniers@google.com john.fastabend@gmail.com kafai@fb.com nathan@kernel.org jean-philippe@linaro.org kpsingh@kernel.org
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success No Fixes tag
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 16 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success No static functions without inline keyword in header files
bpf/vmtest-bpf-next-PR success PR summary
bpf/vmtest-bpf-next success VM_Test

Commit Message

Quentin Monnet Oct. 9, 2021, 9:03 p.m. UTC 
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@kernel.org>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
---
 tools/bpf/bpftool/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

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) $@