bpftool: Reset map info between queries

index 20d59eab09a1..f84311fa640d 100644
@@ -647,6 +647,8 @@ static int do_show_subset(int argc, char **argv)
 	if (json_output && nb_fds > 1)
 		jsonw_start_array(json_wtr);	/* root array */
 	for (i = 0; i < nb_fds; i++) {
+		memset(&info, 0, sizeof(info));
+		len = sizeof(info);
 		err = bpf_map_get_info_by_fd(fds[i], &info, &len);
 		if (err) {
 			p_err("can't get map info: %s",

@@ -718,6 +720,8 @@ static int do_show(int argc, char **argv)
 			break;
 		}
 
+		memset(&info, 0, sizeof(info));
+		len = sizeof(info);
 		err = bpf_map_get_info_by_fd(fd, &info, &len);
 		if (err) {
 			p_err("can't get map info: %s", strerror(errno));

@@ -774,6 +778,8 @@ static int maps_have_btf(int *fds, int nb_fds)
 	int err, i;
 
 	for (i = 0; i < nb_fds; i++) {
+		memset(&info, 0, sizeof(info));
+		len = sizeof(info);
 		err = bpf_map_get_info_by_fd(fds[i], &info, &len);
 		if (err) {
 			p_err("can't get map info: %s", strerror(errno));

@@ -952,6 +958,8 @@ static int do_dump(int argc, char **argv)
 	if (wtr && nb_fds > 1)
 		jsonw_start_array(wtr);	/* root array */
 	for (i = 0; i < nb_fds; i++) {
+		memset(&info, 0, sizeof(info));
+		len = sizeof(info);
 		if (bpf_map_get_info_by_fd(fds[i], &info, &len)) {
 			p_err("can't get map info: %s", strerror(errno));
 			err = -1;

new file mode 100644
index 000000000000..5bcfef952619
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <test_progs.h>
+#include <bpftool_helpers.h>
+#include <bpf/btf.h>
+
+#define OUTPUT_SIZE (1024 * 1024)
+
+static void check_show(char *output, struct bpf_map_info *info)
+{
+	char id[32];
+	char *map, *end, *btf;
+
+	snprintf(id, sizeof(id), "{\"id\":%u,", info->id);
+	map = strstr(output, id);
+	if (!ASSERT_OK_PTR(map, "map_in_output"))
+		return;
+	end = strchr(map, '}');
+	if (!ASSERT_OK_PTR(end, "map_object_end"))
+		return;
+	btf = strstr(map, "\"btf_id\":");
+	if (info->btf_id) {
+		ASSERT_TRUE(btf && btf < end, "typed_map_btf");
+		if (btf && btf < end)
+			ASSERT_EQ(strtoul(btf + strlen("\"btf_id\":"), NULL, 10),
+				  info->btf_id, "btf_id");
+	} else {
+		ASSERT_TRUE(!btf || btf > end, "raw_map_no_btf");
+	}
+}
+
+static void test_map_info(const char *operation)
+{
+	LIBBPF_OPTS(bpf_map_create_opts, opts);
+	struct bpf_map_info info[2] = {};
+	char command[MAX_BPFTOOL_CMD_LEN], name[BPF_OBJ_NAME_LEN];
+	char elements[2][1024] = {}, expected[4096];
+	struct btf *btf = NULL;
+	int fds[] = { -1, -1 };
+	__u64 wide_key = 0, wide_value = 1;
+	__u32 key = 0, value = 2;
+	char *output;
+	int i;
+
+	output = malloc(OUTPUT_SIZE);
+	if (!ASSERT_OK_PTR(output, "output"))
+		return;
+	snprintf(name, sizeof(name), "info_%u", getpid());
+	btf = btf__new_empty();
+	if (!ASSERT_OK_PTR(btf, "create_btf") ||
+	    !ASSERT_EQ(btf__add_int(btf, "unsigned long long", 8, 0), 1, "btf_int") ||
+	    !ASSERT_OK(btf__load_into_kernel(btf), "load_btf"))
+		goto out;
+	opts.btf_fd = btf__fd(btf);
+	opts.btf_key_type_id = 1;
+	opts.btf_value_type_id = 1;
+	/* Query the typed map before a smaller map without BTF. */
+	fds[0] = bpf_map_create(BPF_MAP_TYPE_HASH, name, 8, 8, 1, &opts);
+	fds[1] = bpf_map_create(BPF_MAP_TYPE_HASH, name, 4, 4, 1, NULL);
+	if (!ASSERT_OK_FD(fds[0], "create_typed") ||
+	    !ASSERT_OK_FD(fds[1], "create_raw") ||
+	    !ASSERT_OK(bpf_map_update_elem(fds[0], &wide_key, &wide_value, BPF_ANY),
+		       "populate_typed") ||
+	    !ASSERT_OK(bpf_map_update_elem(fds[1], &key, &value, BPF_ANY), "populate_raw"))
+		goto out;
+	for (i = 0; i < ARRAY_SIZE(fds); i++) {
+		__u32 len = sizeof(info[i]);
+
+		if (!ASSERT_OK(bpf_map_get_info_by_fd(fds[i], &info[i], &len), "map_info"))
+			goto out;
+	}
+	if (!ASSERT_LT(info[0].id, info[1].id, "map_order"))
+		goto out;
+
+	if (!strcmp(operation, "show_all"))
+		snprintf(command, sizeof(command), "-j map show");
+	else if (!strcmp(operation, "show_name"))
+		snprintf(command, sizeof(command), "-j map show name %s", name);
+	else
+		snprintf(command, sizeof(command), "%s map dump name %s",
+			 !strcmp(operation, "dump_json") ? "-j" : "", name);
+	output[0] = '\0';
+	if (!ASSERT_OK(get_bpftool_command_output(command, output, OUTPUT_SIZE), operation))
+		goto out;
+	if (!strncmp(operation, "show_", 5)) {
+		check_show(output, &info[0]);
+		check_show(output, &info[1]);
+	} else if (!strcmp(operation, "dump_json")) {
+		for (i = 0; i < ARRAY_SIZE(fds); i++) {
+			snprintf(command, sizeof(command), "-j map dump id %u", info[i].id);
+			if (!ASSERT_OK(get_bpftool_command_output(command, elements[i],
+							 sizeof(elements[i])), "single_dump"))
+				goto out;
+			elements[i][strcspn(elements[i], "\n")] = '\0';
+		}
+		snprintf(expected, sizeof(expected),
+			 "[{\"id\":%u,\"type\":\"hash\",\"name\":\"%s\",\"flags\":0,"
+			 "\"elements\":%s},{\"id\":%u,\"type\":\"hash\",\"name\":\"%s\","
+			 "\"flags\":0,\"elements\":%s}]\n",
+			 info[0].id, name, elements[0], info[1].id, name, elements[1]);
+		ASSERT_STREQ(output, expected, "independent_map_formatting");
+	} else {
+		char *count = strstr(output, "Found 1 element\n");
+
+		ASSERT_NULL(strstr(output, "\"value\":"), "mixed_maps_use_raw_output");
+		if (ASSERT_OK_PTR(count, "first_map_count"))
+			ASSERT_HAS_SUBSTR(count + 1, "Found 1 element\n", "second_map_count");
+	}
+out:
+	for (i = 0; i < ARRAY_SIZE(fds); i++)
+		if (fds[i] >= 0)
+			close(fds[i]);
+	btf__free(btf);
+	free(output);
+}
+
+void serial_test_bpftool_map_info(void)
+{
+	if (test__start_subtest("show_all"))
+		test_map_info("show_all");
+	if (test__start_subtest("show_name"))
+		test_map_info("show_name");
+	if (test__start_subtest("dump_json"))
+		test_map_info("dump_json");
+	if (test__start_subtest("dump_plain"))
+		test_map_info("dump_plain");
+}