selftests/bpf: Add C tests for kptr

This uses the __kptr and __kptr_ref macros as well, and tries to test
the stuff that is supposed to work, since we have negative tests in
test_verifier suite. Also include some code to test map-in-map support,
such that the inner_map_meta matches the kptr_off_tab of map added as
element.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-12-memxor@gmail.com

tools/testing/selftests/bpf/prog_tests/map_kptr.c

+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+
+#include "map_kptr.skel.h"
+
+void test_map_kptr(void)
+{
+	struct map_kptr *skel;
+	int key = 0, ret;
+	char buf[24];
+
+	skel = map_kptr__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "map_kptr__open_and_load"))
+		return;
+
+	ret = bpf_map_update_elem(bpf_map__fd(skel->maps.array_map), &key, buf, 0);
+	ASSERT_OK(ret, "array_map update");
+	ret = bpf_map_update_elem(bpf_map__fd(skel->maps.array_map), &key, buf, 0);
+	ASSERT_OK(ret, "array_map update2");
+
+	ret = bpf_map_update_elem(bpf_map__fd(skel->maps.hash_map), &key, buf, 0);
+	ASSERT_OK(ret, "hash_map update");
+	ret = bpf_map_delete_elem(bpf_map__fd(skel->maps.hash_map), &key);
+	ASSERT_OK(ret, "hash_map delete");
+
+	ret = bpf_map_update_elem(bpf_map__fd(skel->maps.hash_malloc_map), &key, buf, 0);
+	ASSERT_OK(ret, "hash_malloc_map update");
+	ret = bpf_map_delete_elem(bpf_map__fd(skel->maps.hash_malloc_map), &key);
+	ASSERT_OK(ret, "hash_malloc_map delete");
+
+	ret = bpf_map_update_elem(bpf_map__fd(skel->maps.lru_hash_map), &key, buf, 0);
+	ASSERT_OK(ret, "lru_hash_map update");
+	ret = bpf_map_delete_elem(bpf_map__fd(skel->maps.lru_hash_map), &key);
+	ASSERT_OK(ret, "lru_hash_map delete");
+
+	map_kptr__destroy(skel);
+}

tools/testing/selftests/bpf/progs/map_kptr.c

+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+
+struct map_value {
+	struct prog_test_ref_kfunc __kptr *unref_ptr;
+	struct prog_test_ref_kfunc __kptr_ref *ref_ptr;
+};
+
+struct array_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} array_map SEC(".maps");
+
+struct hash_map {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} hash_map SEC(".maps");
+
+struct hash_malloc_map {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+} hash_malloc_map SEC(".maps");
+
+struct lru_hash_map {
+	__uint(type, BPF_MAP_TYPE_LRU_HASH);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} lru_hash_map SEC(".maps");
+
+#define DEFINE_MAP_OF_MAP(map_type, inner_map_type, name)       \
+	struct {                                                \
+		__uint(type, map_type);                         \
+		__uint(max_entries, 1);                         \
+		__uint(key_size, sizeof(int));                  \
+		__uint(value_size, sizeof(int));                \
+		__array(values, struct inner_map_type);         \
+	} name SEC(".maps") = {                                 \
+		.values = { [0] = &inner_map_type },            \
+	}
+
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_ARRAY_OF_MAPS, array_map, array_of_array_maps);
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_ARRAY_OF_MAPS, hash_map, array_of_hash_maps);
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_ARRAY_OF_MAPS, hash_malloc_map, array_of_hash_malloc_maps);
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_ARRAY_OF_MAPS, lru_hash_map, array_of_lru_hash_maps);
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_HASH_OF_MAPS, array_map, hash_of_array_maps);
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_HASH_OF_MAPS, hash_map, hash_of_hash_maps);
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_HASH_OF_MAPS, hash_malloc_map, hash_of_hash_malloc_maps);
+DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_HASH_OF_MAPS, lru_hash_map, hash_of_lru_hash_maps);
+
+extern struct prog_test_ref_kfunc *bpf_kfunc_call_test_acquire(unsigned long *sp) __ksym;
+extern struct prog_test_ref_kfunc *
+bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b) __ksym;
+extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
+
+static void test_kptr_unref(struct map_value *v)
+{
+	struct prog_test_ref_kfunc *p;
+
+	p = v->unref_ptr;
+	/* store untrusted_ptr_or_null_ */
+	v->unref_ptr = p;
+	if (!p)
+		return;
+	if (p->a + p->b > 100)
+		return;
+	/* store untrusted_ptr_ */
+	v->unref_ptr = p;
+	/* store NULL */
+	v->unref_ptr = NULL;
+}
+
+static void test_kptr_ref(struct map_value *v)
+{
+	struct prog_test_ref_kfunc *p;
+
+	p = v->ref_ptr;
+	/* store ptr_or_null_ */
+	v->unref_ptr = p;
+	if (!p)
+		return;
+	if (p->a + p->b > 100)
+		return;
+	/* store NULL */
+	p = bpf_kptr_xchg(&v->ref_ptr, NULL);
+	if (!p)
+		return;
+	if (p->a + p->b > 100) {
+		bpf_kfunc_call_test_release(p);
+		return;
+	}
+	/* store ptr_ */
+	v->unref_ptr = p;
+	bpf_kfunc_call_test_release(p);
+
+	p = bpf_kfunc_call_test_acquire(&(unsigned long){0});
+	if (!p)
+		return;
+	/* store ptr_ */
+	p = bpf_kptr_xchg(&v->ref_ptr, p);
+	if (!p)
+		return;
+	if (p->a + p->b > 100) {
+		bpf_kfunc_call_test_release(p);
+		return;
+	}
+	bpf_kfunc_call_test_release(p);
+}
+
+static void test_kptr_get(struct map_value *v)
+{
+	struct prog_test_ref_kfunc *p;
+
+	p = bpf_kfunc_call_test_kptr_get(&v->ref_ptr, 0, 0);
+	if (!p)
+		return;
+	if (p->a + p->b > 100) {
+		bpf_kfunc_call_test_release(p);
+		return;
+	}
+	bpf_kfunc_call_test_release(p);
+}
+
+static void test_kptr(struct map_value *v)
+{
+	test_kptr_unref(v);
+	test_kptr_ref(v);
+	test_kptr_get(v);
+}
+
+SEC("tc")
+int test_map_kptr(struct __sk_buff *ctx)
+{
+	struct map_value *v;
+	int i, key = 0;
+
+#define TEST(map)					\
+	v = bpf_map_lookup_elem(&map, &key);		\
+	if (!v)						\
+		return 0;				\
+	test_kptr(v)
+
+	TEST(array_map);
+	TEST(hash_map);
+	TEST(hash_malloc_map);
+	TEST(lru_hash_map);
+
+#undef TEST
+	return 0;
+}
+
+SEC("tc")
+int test_map_in_map_kptr(struct __sk_buff *ctx)
+{
+	struct map_value *v;
+	int i, key = 0;
+	void *map;
+
+#define TEST(map_in_map)                                \
+	map = bpf_map_lookup_elem(&map_in_map, &key);   \
+	if (!map)                                       \
+		return 0;                               \
+	v = bpf_map_lookup_elem(map, &key);		\
+	if (!v)						\
+		return 0;				\
+	test_kptr(v)
+
+	TEST(array_of_array_maps);
+	TEST(array_of_hash_maps);
+	TEST(array_of_hash_malloc_maps);
+	TEST(array_of_lru_hash_maps);
+	TEST(hash_of_array_maps);
+	TEST(hash_of_hash_maps);
+	TEST(hash_of_hash_malloc_maps);
+	TEST(hash_of_lru_hash_maps);
+
+#undef TEST
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";