From: Viktor Malik on
gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/2749#note_1617...
Argh, compiler/linker arguments in BPF Makefiles are sometimes a mess.
But, since the error occurs when linking `libbpf.a` for `samples/bpf/bpftool`,
let's take the same approach as we do for selftests and reuse the bpftool that
we've already built.
This will require one more patch to `samples/bpf/Makefile`:
```diff
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4ccf4236031c..ce9c2eea82d4 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -253,8 +253,9 @@ $(LIBBPF): $(wildcard $(LIBBPF_SRC)/*.[ch]
$(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU
BPFTOOLDIR := $(TOOLS_PATH)/bpf/bpftool
BPFTOOL_OUTPUT := $(abspath $(BPF_SAMPLES_PATH))/bpftool
-BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool
-$(BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) |
$(BPFTOOL_OUTPUT)
+DEFAULT_BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool
+BPFTOOL ?= $(DEFAULT_BPFTOOL)
+$(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) |
$(BPFTOOL_OUTPUT)
$(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../
\
OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap
```
and the specfile change:
```suggestion:-0+0
%{make} %{?_smp_mflags} TPROGS_USER_CFLAGS="%{?build_hostcflags}"
TPROGS_USER_LDFLAGS="%{?build_ldflags}"
BPFTOOL="$(pwd)/tools/bpf/bpftool/bpftool" ARCH=$Arch V=1 M=samples/bpf/
VMLINUX_H="${RPM_VMLINUX_H}" || true
```
This way, the samples successfully build for me. Unfortunately, rpmbuild fails
later when stripping the BPF programs `samples/bpf/*_kern.o` (another binutils
problem?), but we should be able to resolve that by just not stripping them.