[PATCH bpf-next 17/17] sleftests/bpf: add map linking selftest

[Andrii Nakryiko <andrii@kernel.org>]

Add selftest validating various aspects of statically linking BTF-defined map
definitions. Legacy map definitions do not support extern resolution between
object files. Some of the aspects validated:
  - correct resolution of extern maps against concrete map definitions;
  - extern maps can currently only specify map type and key/value size and/or
    type information;
  - weak concrete map definitions are resolved properly.

Static map definitions are not yet supported by libbpf, so they are not
explicitly tested, though manual testing showes that BPF linker handles them
properly.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/testing/selftests/bpf/Makefile          |   4 +-
 .../selftests/bpf/prog_tests/linked_maps.c    |  33 ++++++
 .../selftests/bpf/progs/linked_maps1.c        | 102 ++++++++++++++++
 .../selftests/bpf/progs/linked_maps2.c        | 112 ++++++++++++++++++
 4 files changed, 250 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/linked_maps.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_maps1.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_maps2.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index a690fd125c6d..bd6d60644275 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -303,11 +303,13 @@ endef
 
 SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
 
-LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h linked_vars.skel.h
+LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h		\
+		linked_vars.skel.h linked_maps.skel.h
 
 test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o
 linked_funcs.skel.h-deps := linked_funcs1.o linked_funcs2.o
 linked_vars.skel.h-deps := linked_vars1.o linked_vars2.o
+linked_maps.skel.h-deps := linked_maps1.o linked_maps2.o
 
 LINKED_BPF_SRCS := $(patsubst %.o,%.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps)))
 
diff --git a/tools/testing/selftests/bpf/prog_tests/linked_maps.c b/tools/testing/selftests/bpf/prog_tests/linked_maps.c
new file mode 100644
index 000000000000..69e0ef34aff2
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/linked_maps.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <test_progs.h>
+#include <sys/syscall.h>
+#include "linked_maps.skel.h"
+
+void test_linked_maps(void)
+{
+	int err;
+	struct linked_maps* skel;
+
+	skel = linked_maps__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	err = linked_maps__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	/* trigger */
+	syscall(SYS_getpgid);
+
+	ASSERT_EQ(skel->bss->output_first1, 2000, "output_first1");
+	ASSERT_EQ(skel->bss->output_second1, 2, "output_second1");
+	ASSERT_EQ(skel->bss->output_weak1, 2, "output_weak1");
+	/*
+	ASSERT_EQ(skel->bss->output_static1, 2, "output_static1");
+	*/
+
+cleanup:
+	linked_maps__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/linked_maps1.c b/tools/testing/selftests/bpf/progs/linked_maps1.c
new file mode 100644
index 000000000000..6fb853043318
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_maps1.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct my_key { long x; };
+struct my_value { long x; };
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, struct my_key);
+	__type(value, struct my_value);
+	__uint(max_entries, 16);
+} map1 SEC(".maps");
+
+extern struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	/* no max_entries can be specified in extern map */
+} map2 SEC(".maps");
+
+/* This should be the winning map definition, but we have no way of verifying,
+ * so we just make sure that it links and works without errors
+ */
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 16);
+} map_weak __weak SEC(".maps");
+
+/* Once BPF skeleton can handle static maps with the same name, this map
+ * should be renamed to just map_static in both files. For now we just make
+ * sure that static map definitions work.
+ */
+/*
+static struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 4);
+} map_static1 SEC(".maps");
+*/
+
+int output_first1 = 0;
+int output_second1 = 0;
+int output_weak1 = 0;
+/*
+int output_static1 = 0;
+*/
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler_enter1)
+{
+	/* update values with key = 1 */
+	int key = 1, val = 1;
+	struct my_key key_struct = { .x = 1 };
+	struct my_value val_struct = { .x = 1000 };
+
+	bpf_map_update_elem(&map1, &key_struct, &val_struct, 0);
+	bpf_map_update_elem(&map2, &key, &val, 0);
+	bpf_map_update_elem(&map_weak, &key, &val, 0);
+	/*
+	bpf_map_update_elem(&map_static1, &key, &val, 0);
+	*/
+
+	return 0;
+}
+
+SEC("raw_tp/sys_exit")
+int BPF_PROG(handler_exit1)
+{
+	/* lookup values with key = 2, set in another file */
+	int key = 2, *val;
+	struct my_key key_struct = { .x = 2 };
+	struct my_value *value_struct;
+
+	value_struct = bpf_map_lookup_elem(&map1, &key_struct);
+	if (value_struct)
+		output_first1 = value_struct->x;
+
+	val = bpf_map_lookup_elem(&map2, &key);
+	if (val)
+		output_second1 = *val;
+
+	val = bpf_map_lookup_elem(&map_weak, &key);
+	if (val)
+		output_weak1 = *val;
+	
+	/*
+	val = bpf_map_lookup_elem(&map_static1, &key);
+	if (val)
+		output_static1 = *val;
+	*/
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/linked_maps2.c b/tools/testing/selftests/bpf/progs/linked_maps2.c
new file mode 100644
index 000000000000..93ac7c4f90d2
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_maps2.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+/* modifiers and typedefs are ignored when comparing key/value types */
+typedef struct my_key { long x; } key_type;
+typedef struct my_value { long x; } value_type;
+
+extern struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, key_type);
+	__type(value, value_type);
+	/* no max_entries on extern map definitions */
+} map1 SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 8);
+} map2 SEC(".maps");
+
+/* this definition will lose, but it has to exactly match the winner */
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 16);
+} map_weak __weak SEC(".maps");
+
+/* Once BPF skeleton can handle static maps with the same name, this map
+ * should be renamed to just map_static in both files. For now we just make
+ * sure that static map definitions work.
+ */
+/*
+static struct {
+*/
+	/* different type */
+/*
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+*/
+	/* key and value are kept int for convenience, they don't have to
+	 * match with map_static1
+	 */
+/*
+	__type(key, int);
+	__type(value, int);
+*/
+	/* different max_entries */
+/*
+	__uint(max_entries, 20);
+} map_static2 SEC(".maps");
+*/
+
+int output_first2 = 0;
+int output_second2 = 0;
+int output_weak2 = 0;
+/*
+int output_static2 = 0;
+*/
+
+SEC("raw_tp/sys_enter")
+int BPF_PROG(handler_enter2)
+{
+	/* update values with key = 2 */
+	int key = 2, val = 2;
+	key_type key_struct = { .x = 2 };
+	value_type val_struct = { .x = 2000 };
+
+	bpf_map_update_elem(&map1, &key_struct, &val_struct, 0);
+	bpf_map_update_elem(&map2, &key, &val, 0);
+	bpf_map_update_elem(&map_weak, &key, &val, 0);
+	/*
+	bpf_map_update_elem(&map_static2, &key, &val, 0);
+	*/
+
+	return 0;
+}
+
+SEC("raw_tp/sys_exit")
+int BPF_PROG(handler_exit2)
+{
+	/* lookup values with key = 1, set in another file */
+	int key = 1, *val;
+	key_type key_struct = { .x = 1 };
+	value_type *value_struct;
+
+	value_struct = bpf_map_lookup_elem(&map1, &key_struct);
+	if (value_struct)
+		output_first2 = value_struct->x;
+
+	val = bpf_map_lookup_elem(&map2, &key);
+	if (val)
+		output_second2 = *val;
+
+	val = bpf_map_lookup_elem(&map_weak, &key);
+	if (val)
+		output_weak2 = *val;
+	
+	/*
+	val = bpf_map_lookup_elem(&map_static2, &key);
+	if (val)
+		output_static2 = *val;
+	*/
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
-- 
2.30.2