Quentin Monnet <quentin.monnet@xxxxxxxxxxxxx> writes: > 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). Oh, right, good point; will fix :)
