[PATCH bpf-next 4/4] selftests/bpf: Test static data relocation

[Joe Stringer <joe@wand.net.nz>]

Add tests for libbpf relocation of static variable references into the
.data and .bss sections of the ELF.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
---
 tools/testing/selftests/bpf/Makefile          |  2 +-
 tools/testing/selftests/bpf/test_progs.c      | 44 +++++++++++++++++
 .../selftests/bpf/test_static_data_kern.c     | 47 +++++++++++++++++++
 3 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/test_static_data_kern.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index c7e1e3255448..ef52a58e2368 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -36,7 +36,7 @@ BPF_OBJ_FILES = \
 	get_cgroup_id_kern.o socket_cookie_prog.o test_select_reuseport_kern.o \
 	test_skb_cgroup_id_kern.o bpf_flow.o netcnt_prog.o test_xdp_vlan.o \
 	xdp_dummy.o test_map_in_map.o test_spin_lock.o test_map_lock.o \
-	test_sock_fields_kern.o
+	test_sock_fields_kern.o test_static_data_kern.o
 
 # Objects are built with default compilation flags and with sub-register
 # code-gen enabled.
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index c52bd90fbb34..72899d58a77c 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -736,6 +736,49 @@ static void test_pkt_md_access(void)
 	bpf_object__close(obj);
 }
 
+static void test_static_data_access(void)
+{
+	const char *file = "./test_static_data_kern.o";
+	struct bpf_object *obj;
+	__u32 duration = 0, retval;
+	int i, err, prog_fd, map_fd;
+	uint32_t value;
+
+	err = bpf_prog_load(file, BPF_PROG_TYPE_SCHED_CLS, &obj, &prog_fd);
+	if (CHECK(err, "load program", "error %d loading %s\n", err, file))
+		return;
+
+	map_fd = bpf_find_map(__func__, obj, "result");
+	if (map_fd < 0) {
+		error_cnt++;
+		goto close_prog;
+	}
+
+	err = bpf_prog_test_run(prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
+				NULL, NULL, &retval, &duration);
+	CHECK(err || retval, "pass packet",
+	      "err %d errno %d retval %d duration %d\n",
+	      err, errno, retval, duration);
+
+	struct {
+		char *name;
+		uint32_t key;
+		uint32_t value;
+	} tests[] = {
+		{ "relocate .bss reference", 0, 0 },
+		{ "relocate .data reference", 1, 42 },
+	};
+	for (i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+		err = bpf_map_lookup_elem(map_fd, &tests[i].key, &value);
+		CHECK (err || value != tests[i].value, tests[i].name,
+		       "err %d result %d expected %d\n",
+		       err, value, tests[i].value);
+	}
+
+close_prog:
+	bpf_object__close(obj);
+}
+
 static void test_obj_name(void)
 {
 	struct {
@@ -2138,6 +2181,7 @@ int main(void)
 	test_flow_dissector();
 	test_spinlock();
 	test_map_lock();
+	test_static_data_access();
 
 	printf("Summary: %d PASSED, %d FAILED\n", pass_cnt, error_cnt);
 	return error_cnt ? EXIT_FAILURE : EXIT_SUCCESS;
diff --git a/tools/testing/selftests/bpf/test_static_data_kern.c b/tools/testing/selftests/bpf/test_static_data_kern.c
new file mode 100644
index 000000000000..f2485af6bd0b
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_static_data_kern.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Isovalent, Inc.
+
+#include <linux/bpf.h>
+#include <linux/pkt_cls.h>
+
+#include <string.h>
+
+#include "bpf_helpers.h"
+
+#define NUM_CGROUP_LEVELS	4
+
+struct bpf_map_def SEC("maps") result = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u32),
+	.max_entries = 2,
+};
+
+#define __fetch(x) (__u32)(&(x))
+
+static __u32 static_bss = 0;	/* Reloc reference to .bss section */
+static __u32 static_data = 42;	/* Reloc reference to .data section */
+
+/**
+ * Load a u32 value from a static variable into a map, for the userland test
+ * program to validate.
+ */
+SEC("static_data_load")
+int load_static_data(struct __sk_buff *skb)
+{
+	__u32 key, value;
+
+	key = 0;
+	value = __fetch(static_bss);
+	bpf_map_update_elem(&result, &key, &value, 0);
+
+	key = 1;
+	value = __fetch(static_data);
+	bpf_map_update_elem(&result, &key, &value, 0);
+
+	return TC_ACT_OK;
+}
+
+int _version SEC("version") = 1;
+
+char _license[] SEC("license") = "GPL";
-- 
2.19.1