libbpf: add libelf dependency to shared library build

The DPDK project is moving forward with its AF_XDP PMD, and during
that process some libbpf issues surfaced [1]: When libbpf was built
as a shared library, libelf was not included in the linking phase.
Since libelf is an internal depedency to libbpf, libelf should be
included. This patch adds '-lelf' to resolve that.

  [1] https://patches.dpdk.org/patch/50704/#93571

Fixes: 1b76c13e4b36 ("bpf tools: Introduce 'bpf' library and add bpf feature check")
Suggested-by: Luca Boccassi <bluca@debian.org>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 279589c..7beec4d 100644 (file)
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -177,7 +177,7 @@ $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
 
 $(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN)
        $(QUIET_LINK)$(CC) --shared -Wl,-soname,libbpf.so.$(VERSION) \
-                                   -Wl,--version-script=$(VERSION_SCRIPT) $^ -o $@
+                                   -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@
        @ln -sf $(@F) $(OUTPUT)libbpf.so
        @ln -sf $(@F) $(OUTPUT)libbpf.so.$(VERSION)