[PATCH] perf tools: Allow to link with libbpf dynamicaly

Jiri Olsa
2019-11-26T12:13:13Z

Currently we support only static linking with kernel's
libbpf (tools/lib/bpf). This patch adds libbpf package
detection and support to link perf with it dynamically.

The libbpf package status is displayed with:

$ make VF=1
Auto-detecting system features:
...
... libbpf: [ on ]

It's not checked by default, because it's quite new.
Once it's on most distros we can switch it on.

For the same reason it's not added to the test-all check.

Perf does not need advanced version of libbpf, so we can
check just for the base bpf_object__open function.

Adding new compile variable to detect libbpf package and
link bpf dynamically:

$ make LIBBPF_DYNAMIC=1
...
LINK perf
$ ldd perf | grep bpf
libbpf.so.0 => /lib64/libbpf.so.0 (0x00007f46818bc000)

If libbpf is not installed, build stops with:

Makefile.config:486: *** Error: No libbpf devel library found,\
please install libbpf-devel. Stop.

Link: http://lkml.kernel.org/n/tip-kjdr6k37nuoiwbl0yltla1nh@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/build/Makefile.feature | 3 ++-
tools/build/feature/Makefile | 4 ++++
tools/build/feature/test-libbpf.c | 7 +++++++
tools/perf/Makefile.config | 10 ++++++++++
tools/perf/Makefile.perf | 6 +++++-
5 files changed, 28 insertions(+), 2 deletions(-)
create mode 100644 tools/build/feature/test-libbpf.c

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 8a19753cc26a..574c2e0b9d20 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -96,7 +96,8 @@ FEATURE_TESTS_EXTRA := \
cxx \
llvm \
llvm-version \
- clang
+ clang \
+ libbpf

FEATURE_TESTS ?= $(FEATURE_TESTS_BASIC)

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 8499385365c0..f30a89046aa3 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -53,6 +53,7 @@ FILES= \
test-zlib.bin \
test-lzma.bin \
test-bpf.bin \
+ test-libbpf.bin \
test-get_cpuid.bin \
test-sdt.bin \
test-cxx.bin \
@@ -270,6 +271,9 @@ $(OUTPUT)test-get_cpuid.bin:
$(OUTPUT)test-bpf.bin:
$(BUILD)

+$(OUTPUT)test-libbpf.bin:
+ $(BUILD) -lbpf
+
$(OUTPUT)test-sdt.bin:
$(BUILD)

diff --git a/tools/build/feature/test-libbpf.c b/tools/build/feature/test-libbpf.c
new file mode 100644
index 000000000000..a508756cf4cc
--- /dev/null
+++ b/tools/build/feature/test-libbpf.c
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <bpf/libbpf.h>
+
+int main(void)
+{
+ return bpf_object__open("test") ? 0 : -1;
+}
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 1783427da9b0..c90f4146e5a2 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -483,6 +483,16 @@ ifndef NO_LIBELF
ifeq ($(feature-bpf), 1)
CFLAGS += -DHAVE_LIBBPF_SUPPORT
$(call detected,CONFIG_LIBBPF)
+
+ # detecting libbpf without LIBBPF_DYNAMIC, so make VF=1 shows libbpf detection status
+ $(call feature_check,libbpf)
+ ifdef LIBBPF_DYNAMIC
+ ifeq ($(feature-libbpf), 1)
+ EXTLIBS += -lbpf
+ else
+ dummy := $(error Error: No libbpf devel library found, please install libbpf-devel);
+ endif
+ endif
endif

ifndef NO_DWARF
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 1cd294468a1f..eae5d5e95952 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -116,6 +116,8 @@ include ../scripts/utilities.mak
#
# Define TCMALLOC to enable tcmalloc heap profiling.
#
+# Define LIBBPF_DYNAMIC to enable libbpf dynamic linking.
+#

# As per kernel Makefile, avoid funny character set dependencies
unexport LC_ALL
@@ -360,7 +362,9 @@ export PERL_PATH

PERFLIBS = $(LIBAPI) $(LIBTRACEEVENT) $(LIBSUBCMD) $(LIBPERF)
ifndef NO_LIBBPF
- PERFLIBS += $(LIBBPF)
+ ifndef LIBBPF_DYNAMIC
+ PERFLIBS += $(LIBBPF)
+ endif
endif

# We choose to avoid "if .. else if .. else .. endif endif"
--
2.21.0