2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@xxxxxxxxxx> > Currently we support only static linking with kernel's libbpf > (tools/lib/bpf). This patch adds LIBBPF_DYNAMIC compile variable > that triggers libbpf detection and bpf dynamic linking: > > $ make -C tools/bpf/bpftool make LIBBPF_DYNAMIC=1 > > If libbpf is not installed, build (with LIBBPF_DYNAMIC=1) stops with: > > $ make -C tools/bpf/bpftool LIBBPF_DYNAMIC=1 > Auto-detecting system features: > ... libbfd: [ on ] > ... disassembler-four-args: [ on ] > ... zlib: [ on ] > ... libbpf: [ OFF ] > > Makefile:102: *** Error: libbpf-devel is missing, please install it. Stop. > > Adding specific bpftool's libbpf check for libbpf_netlink_open (LIBBPF_0.0.6) > which is the latest we need for bpftool at the moment. > > Adding LIBBPF_DIR compile variable to allow linking with > libbpf installed into specific directory: > > $ make -C tools/lib/bpf/ prefix=/tmp/libbpf/ install_lib install_headers > $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/ > > It might be needed to clean build tree first because features > framework does not detect the change properly: > > $ make -C tools/build/feature clean > $ make -C tools/bpf/bpftool/ clean > > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > --- > tools/bpf/bpftool/Makefile | 40 ++++++++++++++++++++++++++++++- > tools/build/feature/test-libbpf.c | 9 +++++++ > 2 files changed, 48 insertions(+), 1 deletion(-) > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile > index 39bc6f0f4f0b..2b6ed08cb31e 100644 > --- a/tools/bpf/bpftool/Makefile > +++ b/tools/bpf/bpftool/Makefile > @@ -55,7 +64,7 @@ ifneq ($(EXTRA_LDFLAGS),) > LDFLAGS += $(EXTRA_LDFLAGS) > endif > > -LIBS = $(LIBBPF) -lelf -lz > +LIBS = -lelf -lz Hi Jiri, This change seems to be breaking the build with the static library for me. I know you add back $(LIBBPF) later in the Makefile, see at the end of this email... > > INSTALL ?= install > RM ?= rm -f > @@ -64,6 +73,23 @@ FEATURE_USER = .bpftool > FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib > FEATURE_DISPLAY = libbfd disassembler-four-args zlib > > +ifdef LIBBPF_DYNAMIC > + # Add libbpf check with the flags to ensure bpftool > + # specific version is detected. Nit: We do not check for a specific bpftool version, we check for a recent enough libbpf version? > + FEATURE_CHECK_CFLAGS-libbpf := -DBPFTOOL > + FEATURE_TESTS += libbpf > + FEATURE_DISPLAY += libbpf > + > + # for linking with debug library run: > + # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf > + ifdef LIBBPF_DIR > + LIBBPF_CFLAGS := -I$(LIBBPF_DIR)/include > + LIBBPF_LDFLAGS := -L$(LIBBPF_DIR)/$(libdir_relative) > + FEATURE_CHECK_CFLAGS-libbpf := $(LIBBPF_CFLAGS) > + FEATURE_CHECK_LDFLAGS-libbpf := $(LIBBPF_LDFLAGS) > + endif > +endif > + > check_feat := 1 > NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall > ifdef MAKECMDGOALS > @@ -88,6 +114,18 @@ ifeq ($(feature-reallocarray), 0) > CFLAGS += -DCOMPAT_NEED_REALLOCARRAY > endif > > +ifdef LIBBPF_DYNAMIC > + ifeq ($(feature-libbpf), 1) > + LIBS += -lbpf > + CFLAGS += $(LIBBPF_CFLAGS) > + LDFLAGS += $(LIBBPF_LDFLAGS) > + else > + dummy := $(error Error: No libbpf devel library found, please install libbpf-devel) libbpf-devel sounds like a RH/Fedora package name, but other distributions might have different names (Debian/Ubuntu would go by libbpf-dev I suppose, although I don't believe such package exists at the moment). Maybe use a more generic message? > + endif > +else > + LIBS += $(LIBBPF) ... I believe the order of the libraries is relevant, and it seems the static libbpf should be passed before the dynamic libs. Here I could fix the build with the static library on my setup by prepending the library path instead, like this: LIBS := $(LIBBPF) $(LIBS) On the plus side, all build attempts from tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on my setup with dynamic linking from your branch. > +endif > + > include $(wildcard $(OUTPUT)*.d) > > all: $(OUTPUT)bpftool Thanks, Quentin
