selftests/bpf: Add bpf_lookup_and_delete_elem tests

Add bpf selftests and extend existing ones for a new function
bpf_lookup_and_delete_elem() for (percpu) hash and (percpu) LRU hash map
types.
In test_lru_map and test_maps we add an element, lookup_and_delete it,
then check whether it's deleted.
The newly added lookup_and_delete prog tests practically do the same
thing but additionally use a BPF program to change the value of the
element for LRU maps.

Signed-off-by: Denis Salopek <denis.salopek@sartura.hr>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/d30d3e0060c1f750e133579623cf1c60ff58f3d9.1620763117.git.denis.salopek@sartura.hr

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

@@ -0,0 +1,288 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <test_progs.h>
+#include "test_lookup_and_delete.skel.h"
+
+#define START_VALUE 1234
+#define NEW_VALUE 4321
+#define MAX_ENTRIES 2
+
+static int duration;
+static int nr_cpus;
+
+static int fill_values(int map_fd)
+{
+	__u64 key, value = START_VALUE;
+	int err;
+
+	for (key = 1; key < MAX_ENTRIES + 1; key++) {
+		err = bpf_map_update_elem(map_fd, &key, &value, BPF_NOEXIST);
+		if (!ASSERT_OK(err, "bpf_map_update_elem"))
+			return -1;
+	}
+
+	return 0;
+}
+
+static int fill_values_percpu(int map_fd)
+{
+	__u64 key, value[nr_cpus];
+	int i, err;
+
+	for (i = 0; i < nr_cpus; i++)
+		value[i] = START_VALUE;
+
+	for (key = 1; key < MAX_ENTRIES + 1; key++) {
+		err = bpf_map_update_elem(map_fd, &key, value, BPF_NOEXIST);
+		if (!ASSERT_OK(err, "bpf_map_update_elem"))
+			return -1;
+	}
+
+	return 0;
+}
+
+static struct test_lookup_and_delete *setup_prog(enum bpf_map_type map_type,
+						 int *map_fd)
+{
+	struct test_lookup_and_delete *skel;
+	int err;
+
+	skel = test_lookup_and_delete__open();
+	if (!ASSERT_OK_PTR(skel, "test_lookup_and_delete__open"))
+		return NULL;
+
+	err = bpf_map__set_type(skel->maps.hash_map, map_type);
+	if (!ASSERT_OK(err, "bpf_map__set_type"))
+		goto cleanup;
+
+	err = bpf_map__set_max_entries(skel->maps.hash_map, MAX_ENTRIES);
+	if (!ASSERT_OK(err, "bpf_map__set_max_entries"))
+		goto cleanup;
+
+	err = test_lookup_and_delete__load(skel);
+	if (!ASSERT_OK(err, "test_lookup_and_delete__load"))
+		goto cleanup;
+
+	*map_fd = bpf_map__fd(skel->maps.hash_map);
+	if (!ASSERT_GE(*map_fd, 0, "bpf_map__fd"))
+		goto cleanup;
+
+	return skel;
+
+cleanup:
+	test_lookup_and_delete__destroy(skel);
+	return NULL;
+}
+
+/* Triggers BPF program that updates map with given key and value */
+static int trigger_tp(struct test_lookup_and_delete *skel, __u64 key,
+		      __u64 value)
+{
+	int err;
+
+	skel->bss->set_pid = getpid();
+	skel->bss->set_key = key;
+	skel->bss->set_value = value;
+
+	err = test_lookup_and_delete__attach(skel);
+	if (!ASSERT_OK(err, "test_lookup_and_delete__attach"))
+		return -1;
+
+	syscall(__NR_getpgid);
+
+	test_lookup_and_delete__detach(skel);
+
+	return 0;
+}
+
+static void test_lookup_and_delete_hash(void)
+{
+	struct test_lookup_and_delete *skel;
+	__u64 key, value;
+	int map_fd, err;
+
+	/* Setup program and fill the map. */
+	skel = setup_prog(BPF_MAP_TYPE_HASH, &map_fd);
+	if (!ASSERT_OK_PTR(skel, "setup_prog"))
+		return;
+
+	err = fill_values(map_fd);
+	if (!ASSERT_OK(err, "fill_values"))
+		goto cleanup;
+
+	/* Lookup and delete element. */
+	key = 1;
+	err = bpf_map_lookup_and_delete_elem(map_fd, &key, &value);
+	if (!ASSERT_OK(err, "bpf_map_lookup_and_delete_elem"))
+		goto cleanup;
+
+	/* Fetched value should match the initially set value. */
+	if (CHECK(value != START_VALUE, "bpf_map_lookup_and_delete_elem",
+		  "unexpected value=%lld\n", value))
+		goto cleanup;
+
+	/* Check that the entry is non existent. */
+	err = bpf_map_lookup_elem(map_fd, &key, &value);
+	if (!ASSERT_ERR(err, "bpf_map_lookup_elem"))
+		goto cleanup;
+
+cleanup:
+	test_lookup_and_delete__destroy(skel);
+}
+
+static void test_lookup_and_delete_percpu_hash(void)
+{
+	struct test_lookup_and_delete *skel;
+	__u64 key, val, value[nr_cpus];
+	int map_fd, err, i;
+
+	/* Setup program and fill the map. */
+	skel = setup_prog(BPF_MAP_TYPE_PERCPU_HASH, &map_fd);
+	if (!ASSERT_OK_PTR(skel, "setup_prog"))
+		return;
+
+	err = fill_values_percpu(map_fd);
+	if (!ASSERT_OK(err, "fill_values_percpu"))
+		goto cleanup;
+
+	/* Lookup and delete element. */
+	key = 1;
+	err = bpf_map_lookup_and_delete_elem(map_fd, &key, value);
+	if (!ASSERT_OK(err, "bpf_map_lookup_and_delete_elem"))
+		goto cleanup;
+
+	for (i = 0; i < nr_cpus; i++) {
+		val = value[i];
+
+		/* Fetched value should match the initially set value. */
+		if (CHECK(val != START_VALUE, "map value",
+			  "unexpected for cpu %d: %lld\n", i, val))
+			goto cleanup;
+	}
+
+	/* Check that the entry is non existent. */
+	err = bpf_map_lookup_elem(map_fd, &key, value);
+	if (!ASSERT_ERR(err, "bpf_map_lookup_elem"))
+		goto cleanup;
+
+cleanup:
+	test_lookup_and_delete__destroy(skel);
+}
+
+static void test_lookup_and_delete_lru_hash(void)
+{
+	struct test_lookup_and_delete *skel;
+	__u64 key, value;
+	int map_fd, err;
+
+	/* Setup program and fill the LRU map. */
+	skel = setup_prog(BPF_MAP_TYPE_LRU_HASH, &map_fd);
+	if (!ASSERT_OK_PTR(skel, "setup_prog"))
+		return;
+
+	err = fill_values(map_fd);
+	if (!ASSERT_OK(err, "fill_values"))
+		goto cleanup;
+
+	/* Insert new element at key=3, should reuse LRU element. */
+	key = 3;
+	err = trigger_tp(skel, key, NEW_VALUE);
+	if (!ASSERT_OK(err, "trigger_tp"))
+		goto cleanup;
+
+	/* Lookup and delete element 3. */
+	err = bpf_map_lookup_and_delete_elem(map_fd, &key, &value);
+	if (!ASSERT_OK(err, "bpf_map_lookup_and_delete_elem"))
+		goto cleanup;
+
+	/* Value should match the new value. */
+	if (CHECK(value != NEW_VALUE, "bpf_map_lookup_and_delete_elem",
+		  "unexpected value=%lld\n", value))
+		goto cleanup;
+
+	/* Check that entries 3 and 1 are non existent. */
+	err = bpf_map_lookup_elem(map_fd, &key, &value);
+	if (!ASSERT_ERR(err, "bpf_map_lookup_elem"))
+		goto cleanup;
+
+	key = 1;
+	err = bpf_map_lookup_elem(map_fd, &key, &value);
+	if (!ASSERT_ERR(err, "bpf_map_lookup_elem"))
+		goto cleanup;
+
+cleanup:
+	test_lookup_and_delete__destroy(skel);
+}
+
+static void test_lookup_and_delete_lru_percpu_hash(void)
+{
+	struct test_lookup_and_delete *skel;
+	__u64 key, val, value[nr_cpus];
+	int map_fd, err, i, cpucnt = 0;
+
+	/* Setup program and fill the LRU map. */
+	skel = setup_prog(BPF_MAP_TYPE_LRU_PERCPU_HASH, &map_fd);
+	if (!ASSERT_OK_PTR(skel, "setup_prog"))
+		return;
+
+	err = fill_values_percpu(map_fd);
+	if (!ASSERT_OK(err, "fill_values_percpu"))
+		goto cleanup;
+
+	/* Insert new element at key=3, should reuse LRU element 1. */
+	key = 3;
+	err = trigger_tp(skel, key, NEW_VALUE);
+	if (!ASSERT_OK(err, "trigger_tp"))
+		goto cleanup;
+
+	/* Clean value. */
+	for (i = 0; i < nr_cpus; i++)
+		value[i] = 0;
+
+	/* Lookup and delete element 3. */
+	err = bpf_map_lookup_and_delete_elem(map_fd, &key, value);
+	if (!ASSERT_OK(err, "bpf_map_lookup_and_delete_elem")) {
+		goto cleanup;
+	}
+
+	/* Check if only one CPU has set the value. */
+	for (i = 0; i < nr_cpus; i++) {
+		val = value[i];
+		if (val) {
+			if (CHECK(val != NEW_VALUE, "map value",
+				  "unexpected for cpu %d: %lld\n", i, val))
+				goto cleanup;
+			cpucnt++;
+		}
+	}
+	if (CHECK(cpucnt != 1, "map value", "set for %d CPUs instead of 1!\n",
+		  cpucnt))
+		goto cleanup;
+
+	/* Check that entries 3 and 1 are non existent. */
+	err = bpf_map_lookup_elem(map_fd, &key, &value);
+	if (!ASSERT_ERR(err, "bpf_map_lookup_elem"))
+		goto cleanup;
+
+	key = 1;
+	err = bpf_map_lookup_elem(map_fd, &key, &value);
+	if (!ASSERT_ERR(err, "bpf_map_lookup_elem"))
+		goto cleanup;
+
+cleanup:
+	test_lookup_and_delete__destroy(skel);
+}
+
+void test_lookup_and_delete(void)
+{
+	nr_cpus = bpf_num_possible_cpus();
+
+	if (test__start_subtest("lookup_and_delete"))
+		test_lookup_and_delete_hash();
+	if (test__start_subtest("lookup_and_delete_percpu"))
+		test_lookup_and_delete_percpu_hash();
+	if (test__start_subtest("lookup_and_delete_lru"))
+		test_lookup_and_delete_lru_hash();
+	if (test__start_subtest("lookup_and_delete_lru_percpu"))
+		test_lookup_and_delete_lru_percpu_hash();
+}

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

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+__u32 set_pid = 0;
+__u64 set_key = 0;
+__u64 set_value = 0;
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 2);
+	__type(key, __u64);
+	__type(value, __u64);
+} hash_map SEC(".maps");
+
+SEC("tp/syscalls/sys_enter_getpgid")
+int bpf_lookup_and_delete_test(const void *ctx)
+{
+	if (set_pid == bpf_get_current_pid_tgid() >> 32)
+		bpf_map_update_elem(&hash_map, &set_key, &set_value, BPF_NOEXIST);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_lru_map.c

@@ -231,6 +231,14 @@ static void test_lru_sanity0(int map_type, int map_flags)
 	assert(bpf_map_lookup_elem(lru_map_fd, &key, value) == -1 &&
 	       errno == ENOENT);
 
+	/* lookup elem key=1 and delete it, then check it doesn't exist */
+	key = 1;
+	assert(!bpf_map_lookup_and_delete_elem(lru_map_fd, &key, &value));
+	assert(value[0] == 1234);
+
+	/* remove the same element from the expected map */
+	assert(!bpf_map_delete_elem(expected_map_fd, &key));
+
 	assert(map_equal(lru_map_fd, expected_map_fd));
 
 	close(expected_map_fd);

tools/testing/selftests/bpf/test_maps.c

@@ -65,6 +65,13 @@ static void test_hashmap(unsigned int task, void *data)
 	assert(bpf_map_lookup_elem(fd, &key, &value) == 0 && value == 1234);
 
 	key = 2;
+	value = 1234;
+	/* Insert key=2 element. */
+	assert(bpf_map_update_elem(fd, &key, &value, BPF_ANY) == 0);
+
+	/* Check that key=2 matches the value and delete it */
+	assert(bpf_map_lookup_and_delete_elem(fd, &key, &value) == 0 && value == 1234);
+
 	/* Check that key=2 is not found. */
 	assert(bpf_map_lookup_elem(fd, &key, &value) == -1 && errno == ENOENT);
 
@@ -166,6 +173,16 @@ static void test_hashmap_percpu(unsigned int task, void *data)
 	/* Insert key=1 element. */
 	assert(!(expected_key_mask & key));
 	assert(bpf_map_update_elem(fd, &key, value, BPF_ANY) == 0);
+
+	/* Lookup and delete elem key=1 and check value. */
+	assert(bpf_map_lookup_and_delete_elem(fd, &key, value) == 0 &&
+	       bpf_percpu(value,0) == 100);
+
+	for (i = 0; i < nr_cpus; i++)
+		bpf_percpu(value,i) = i + 100;
+
+	/* Insert key=1 element which should not exist. */
+	assert(bpf_map_update_elem(fd, &key, value, BPF_NOEXIST) == 0);
 	expected_key_mask |= key;
 
 	/* BPF_NOEXIST means add new element if it doesn't exist. */