selftests/bpf: add selftest that use test_libbpf_open

This script test_libbpf.sh will be part of the 'make run_tests'
invocation, but can also be invoked manually in this directory,
and a verbose mode can be enabled via setting the environment
variable $VERBOSE like:

$ VERBOSE=yes ./test_libbpf.sh

The script contains some tests that are commented out, as they
currently fail. They are reminders about what we need to improve
for the libbpf loader library.

Signed-off-by: Jesper Dangaard Brouer <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>

tools/testing/selftests/bpf/Makefile

···
 CFLAGS += -Wall -O2 -I$(APIDIR) -I$(LIBDIR) -I$(GENDIR) $(GENFLAGS) -I../../../include
 LDLIBS += -lcap -lelf -lrt -lpthread
 
+# Order correspond to 'make run_tests' order
 TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
 	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user
 
···
 	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \
 	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o \
 	test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o \
-	sample_map_ret0.o test_tcpbpf_kern.o test_libbpf_open
+	sample_map_ret0.o test_tcpbpf_kern.o
 
-TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh \
+# Order correspond to 'make run_tests' order
+TEST_PROGS := test_kmod.sh \
+	test_libbpf.sh \
+	test_xdp_redirect.sh \
+	test_xdp_meta.sh \
 	test_offload.py
+
+# Compile but not part of 'make run_tests'
+TEST_GEN_PROGS_EXTENDED = test_libbpf_open
 
 include ../lib.mk
 
 BPFOBJ := $(OUTPUT)/libbpf.a cgroup_helpers.c
 
 $(TEST_GEN_PROGS): $(BPFOBJ)
+
+$(TEST_GEN_PROGS_EXTENDED): $(OUTPUT)/libbpf.a
 
 .PHONY: force
 

tools/testing/selftests/bpf/test_libbpf.sh

···
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+export TESTNAME=test_libbpf
+
+# Determine selftest success via shell exit code
+exit_handler()
+{
+	if (( $? == 0 )); then
+		echo "selftests: $TESTNAME [PASS]";
+	else
+		echo "$TESTNAME: failed at file $LAST_LOADED" 1>&2
+		echo "selftests: $TESTNAME [FAILED]";
+	fi
+}
+
+libbpf_open_file()
+{
+	LAST_LOADED=$1
+	if [ -n "$VERBOSE" ]; then
+	    ./test_libbpf_open $1
+	else
+	    ./test_libbpf_open --quiet $1
+	fi
+}
+
+# Exit script immediately (well catched by trap handler) if any
+# program/thing exits with a non-zero status.
+set -e
+
+# (Use 'trap -l' to list meaning of numbers)
+trap exit_handler 0 2 3 6 9
+
+libbpf_open_file test_l4lb.o
+
+# TODO: fix libbpf to load noinline functions
+# [warning] libbpf: incorrect bpf_call opcode
+#libbpf_open_file test_l4lb_noinline.o
+
+# TODO: fix test_xdp_meta.c to load with libbpf
+# [warning] libbpf: test_xdp_meta.o doesn't provide kernel version
+#libbpf_open_file test_xdp_meta.o
+
+# TODO: fix libbpf to handle .eh_frame
+# [warning] libbpf: relocation failed: no section(10)
+#libbpf_open_file ../../../../samples/bpf/tracex3_kern.o
+
+# Success
+exit 0