On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote: > 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 $(LIBBPF) later in the Makefile, see at the end > of this email... > > > > > INSTALL ?= install > > RM ?= rm -f > > @@ -64,6 +73,23 @@ FEATURE_USER = .bpftool > > FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib > > FEATURE_DISPLAY = libbfd disassembler-four-args zlib > > > > +ifdef LIBBPF_DYNAMIC > > + # Add libbpf check with the flags to ensure bpftool > > + # specific version is detected. > > Nit: We do not check for a specific bpftool version, we check for a > recent enough libbpf version? hi, we check for a version that has the latest exported function that bpftool needs, which is currently libbpf_netlink_open please check the '#ifdef BPFTOOL' in feature/test-libbpf.c it's like that because there's currently no support to check for particular library version in the build/features framework I'll make that comment more clear > > > + FEATURE_CHECK_CFLAGS-libbpf := -DBPFTOOL > > + FEATURE_TESTS += libbpf > > + FEATURE_DISPLAY += libbpf > > + > > + # for linking with debug library run: > > + # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf > > + ifdef LIBBPF_DIR > > + LIBBPF_CFLAGS := -I$(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? sure, actually in perf we use both package names like: Error: No libbpf devel library found, please install libbpf-devel or libbpf-dev. or we can go with generic message: Error: No libbpf devel library found, please install. > > > + 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) could you please paste the build error? I don't see any on Fedora, anyway I can make the change you're proposing > > 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. cool, had no idea there was such test ;-) thanks, jirka
