tc-testing: fix build of eBPF programs

rely on uAPI headers in the current kernel tree, rather than requiring the
correct version installed on the test system. While at it, group all
sections in a single binary and test the 'section' parameter.

Reported-by: Lucas Bates <lucasb@mojatatu.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/tc-testing/bpf/Makefile

@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: GPL-2.0
+
+APIDIR := ../../../../include/uapi
+TEST_GEN_FILES = action.o
+
+top_srcdir = ../../../../..
+include ../../lib.mk
+
+CLANG ?= clang
+LLC   ?= llc
+PROBE := $(shell $(LLC) -march=bpf -mcpu=probe -filetype=null /dev/null 2>&1)
+
+ifeq ($(PROBE),)
+  CPU ?= probe
+else
+  CPU ?= generic
+endif
+
+CLANG_SYS_INCLUDES := $(shell $(CLANG) -v -E - </dev/null 2>&1 \
+	| sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }')
+
+CLANG_FLAGS = -I. -I$(APIDIR) \
+	      $(CLANG_SYS_INCLUDES) \
+	      -Wno-compare-distinct-pointer-types
+
+$(OUTPUT)/%.o: %.c
+	$(CLANG) $(CLANG_FLAGS) \
+		 -O2 -target bpf -emit-llvm -c $< -o - |      \
+	$(LLC) -march=bpf -mcpu=$(CPU) $(LLC_FLAGS) -filetype=obj -o $@

tools/testing/selftests/tc-testing/bpf/action.c

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0
+ * Copyright (c) 2018 Davide Caratti, Red Hat inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+
+#include <linux/bpf.h>
+#include <linux/pkt_cls.h>
+
+__attribute__((section("action-ok"),used)) int action_ok(struct __sk_buff *s)
+{
+	return TC_ACT_OK;
+}
+
+__attribute__((section("action-ko"),used)) int action_ko(struct __sk_buff *s)
+{
+	s->data = 0x0;
+	return TC_ACT_OK;
+}
+
+char _license[] __attribute__((section("license"),used)) = "GPL";