Merge branch 'bpf-libbpf-relo-fix-and-tests'

Jesper Dangaard Brouer says:

====================
While playing with using libbpf for the Suricata project, we had
issues LLVM >= 4.0.1 generating ELF files that could not be loaded
with libbpf (tools/lib/bpf/).

During the troubleshooting phase, I wrote a test program and improved
the debugging output in libbpf.  I turned this into a selftests
program, and it also serves as a code example for libbpf in itself.

I discovered that there are at least three ELF load issues with
libbpf.  I left them as TODO comments in (tools/testing/selftests/bpf)
test_libbpf.sh. I've only fixed the load issue with eh_frames, and
other types of relo-section that does not have exec flags.  We can
work on the other issues later.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

3 files changed, 210 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 566d6adc172a..5c43c187f27c 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -13,6 +13,7 @@ endif
 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
 
@@ -22,15 +23,24 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
 	test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o \
 	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
 
 # force a rebuild of BPFOBJ when its dependencies are updated
diff --git a/tools/testing/selftests/bpf/test_libbpf.sh b/tools/testing/selftests/bpf/test_libbpf.sh
new file mode 100755
index 000000000000..d97dc914cd49
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_libbpf.sh
@@ -0,0 +1,49 @@
+#!/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
diff --git a/tools/testing/selftests/bpf/test_libbpf_open.c b/tools/testing/selftests/bpf/test_libbpf_open.c
new file mode 100644
index 000000000000..8fcd1c076add
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_libbpf_open.c
@@ -0,0 +1,150 @@
+/* SPDX-License-Identifier: GPL-2.0
+ * Copyright (c) 2018 Jesper Dangaard Brouer, Red Hat Inc.
+ */
+static const char *__doc__ =
+	"Libbpf test program for loading BPF ELF object files";
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+#include <bpf/libbpf.h>
+#include <getopt.h>
+
+static const struct option long_options[] = {
+	{"help",	no_argument,		NULL, 'h' },
+	{"debug",	no_argument,		NULL, 'D' },
+	{"quiet",	no_argument,		NULL, 'q' },
+	{0, 0, NULL,  0 }
+};
+
+static void usage(char *argv[])
+{
+	int i;
+
+	printf("\nDOCUMENTATION:\n%s\n\n", __doc__);
+	printf(" Usage: %s (options-see-below) BPF_FILE\n", argv[0]);
+	printf(" Listing options:\n");
+	for (i = 0; long_options[i].name != 0; i++) {
+		printf(" --%-12s", long_options[i].name);
+		printf(" short-option: -%c",
+		       long_options[i].val);
+		printf("\n");
+	}
+	printf("\n");
+}
+
+#define DEFINE_PRINT_FN(name, enabled) \
+static int libbpf_##name(const char *fmt, ...)  	\
+{							\
+        va_list args;					\
+        int ret;					\
+							\
+        va_start(args, fmt);				\
+	if (enabled) {					\
+		fprintf(stderr, "[" #name "] ");	\
+		ret = vfprintf(stderr, fmt, args);	\
+	}						\
+        va_end(args);					\
+        return ret;					\
+}
+DEFINE_PRINT_FN(warning, 1)
+DEFINE_PRINT_FN(info, 1)
+DEFINE_PRINT_FN(debug, 1)
+
+#define EXIT_FAIL_LIBBPF EXIT_FAILURE
+#define EXIT_FAIL_OPTION 2
+
+int test_walk_progs(struct bpf_object *obj, bool verbose)
+{
+	struct bpf_program *prog;
+	int cnt = 0;
+
+	bpf_object__for_each_program(prog, obj) {
+		cnt++;
+		if (verbose)
+			printf("Prog (count:%d) section_name: %s\n", cnt,
+			       bpf_program__title(prog, false));
+	}
+	return 0;
+}
+
+int test_walk_maps(struct bpf_object *obj, bool verbose)
+{
+	struct bpf_map *map;
+	int cnt = 0;
+
+	bpf_map__for_each(map, obj) {
+		cnt++;
+		if (verbose)
+			printf("Map (count:%d) name: %s\n", cnt,
+			       bpf_map__name(map));
+	}
+	return 0;
+}
+
+int test_open_file(char *filename, bool verbose)
+{
+	struct bpf_object *bpfobj = NULL;
+	long err;
+
+	if (verbose)
+		printf("Open BPF ELF-file with libbpf: %s\n", filename);
+
+	/* Load BPF ELF object file and check for errors */
+	bpfobj = bpf_object__open(filename);
+	err = libbpf_get_error(bpfobj);
+	if (err) {
+		char err_buf[128];
+		libbpf_strerror(err, err_buf, sizeof(err_buf));
+		if (verbose)
+			printf("Unable to load eBPF objects in file '%s': %s\n",
+			       filename, err_buf);
+		return EXIT_FAIL_LIBBPF;
+	}
+	test_walk_progs(bpfobj, verbose);
+	test_walk_maps(bpfobj, verbose);
+
+	if (verbose)
+		printf("Close BPF ELF-file with libbpf: %s\n",
+		       bpf_object__name(bpfobj));
+	bpf_object__close(bpfobj);
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	char filename[1024] = { 0 };
+	bool verbose = 1;
+	int longindex = 0;
+	int opt;
+
+	libbpf_set_print(libbpf_warning, libbpf_info, NULL);
+
+	/* Parse commands line args */
+	while ((opt = getopt_long(argc, argv, "hDq",
+				  long_options, &longindex)) != -1) {
+		switch (opt) {
+		case 'D':
+			libbpf_set_print(libbpf_warning, libbpf_info,
+					 libbpf_debug);
+			break;
+		case 'q': /* Use in scripting mode */
+			verbose = 0;
+			break;
+		case 'h':
+		default:
+			usage(argv);
+			return EXIT_FAIL_OPTION;
+		}
+	}
+	if (optind >= argc) {
+		usage(argv);
+		printf("ERROR: Expected BPF_FILE argument after options\n");
+		return EXIT_FAIL_OPTION;
+	}
+	snprintf(filename, sizeof(filename), "%s", argv[optind]);
+
+	return test_open_file(filename, verbose);
+}