2019-11-28 15:53 UTC+0100 ~ Toke Høiland-Jørgensen <toke@xxxxxxxxxx> > From: 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: No libbpf devel library found, please install-devel or libbpf-dev. > > 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 > > Since bpftool uses bits of libbpf that are not exported as public API in > the .so version, we also pass in libbpf.a to the linker, which allows it to > pick up the private functions from the static library without having to > expose them as ABI. > > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> > --- > v2: > - Pass .a file to linker when dynamically linking, so bpftool can use > private functions from libbpf without exposing them as API. > > tools/bpf/bpftool/Makefile | 38 +++++++++++++++++++++++++++++++++++++- > 1 file changed, 37 insertions(+), 1 deletion(-) > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile > index 39bc6f0f4f0b..397051ed9e41 100644 > --- a/tools/bpf/bpftool/Makefile > +++ b/tools/bpf/bpftool/Makefile > @@ -1,6 +1,15 @@ > # SPDX-License-Identifier: GPL-2.0-only > +# LIBBPF_DYNAMIC to enable libbpf dynamic linking. > + > include ../../scripts/Makefile.include > include ../../scripts/utilities.mak > +include ../../scripts/Makefile.arch > + > +ifeq ($(LP64), 1) > + libdir_relative = lib64 > +else > + libdir_relative = lib > +endif > > ifeq ($(srctree),) > srctree := $(patsubst %/,%,$(dir $(CURDIR))) > @@ -55,7 +64,7 @@ ifneq ($(EXTRA_LDFLAGS),) > LDFLAGS += $(EXTRA_LDFLAGS) > endif > > -LIBS = $(LIBBPF) -lelf -lz > +LIBS = -lelf -lz Hi Toke, You don't need to remove $(LIBBPF) here, because you add it in both cases below (whether $(LIBBPF_DYNAMIC) is defined or not). > > INSTALL ?= install > RM ?= rm -f > @@ -63,6 +72,19 @@ RM ?= rm -f > FEATURE_USER = .bpftool > FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib > FEATURE_DISPLAY = libbfd disassembler-four-args zlib > +ifdef LIBBPF_DYNAMIC > + FEATURE_TESTS += libbpf > + FEATURE_DISPLAY += libbpf > + > + # for linking with debug library run: > + # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf > + ifdef LIBBPF_DIR > + LIBBPF_CFLAGS := -I$(LIBBPF_DIR)/include > + LIBBPF_LDFLAGS := -L$(LIBBPF_DIR)/$(libdir_relative) > + FEATURE_CHECK_CFLAGS-libbpf := $(LIBBPF_CFLAGS) > + FEATURE_CHECK_LDFLAGS-libbpf := $(LIBBPF_LDFLAGS) > + endif > +endif > > check_feat := 1 > NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall > @@ -88,6 +110,20 @@ ifeq ($(feature-reallocarray), 0) > CFLAGS += -DCOMPAT_NEED_REALLOCARRAY > endif > > +ifdef LIBBPF_DYNAMIC > + ifeq ($(feature-libbpf), 1) > + # bpftool uses non-exported functions from libbpf, so pass both dynamic and > + # static versions and let the linker figure it out > + LIBS := -lbpf $(LIBBPF) $(LIBS) [$(LIBBPF) added to $(LIBS) here...] > + CFLAGS += $(LIBBPF_CFLAGS) > + LDFLAGS += $(LIBBPF_LDFLAGS) > + else > + dummy := $(error Error: No libbpf devel library found, please install-devel or libbpf-dev.) “install-devel” :) > + endif > +else > + LIBS := $(LIBBPF) $(LIBS) [... and here] > +endif > + > include $(wildcard $(OUTPUT)*.d) > > all: $(OUTPUT)bpftool > Thanks, Quentin
