[PATCH v4 bpf-next 2/2] selftests/bpf: add dump type data tests to btf dump tests

[Alan Maguire <alan.maguire@oracle.com>]

Test various type data dumping operations by comparing expected
format with the dumped string; an snprintf-style printf function
is used to record the string dumped.  Also verify overflow handling
where the data passed does not cover the full size of a type,
such as would occur if a tracer has a portion of the 8k
"struct task_struct".

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
 tools/testing/selftests/bpf/prog_tests/btf_dump.c | 638 ++++++++++++++++++++++
 1 file changed, 638 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
index 1b90e68..b78c308 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
@@ -232,6 +232,642 @@ void test_btf_dump_incremental(void)
 	btf__free(btf);
 }
 
+#define STRSIZE				4096
+
+void btf_dump_snprintf(void *ctx, const char *fmt, va_list args)
+{
+	char *s = ctx, new[STRSIZE];
+
+	vsnprintf(new, STRSIZE, fmt, args);
+	strncat(s, new, STRSIZE);
+}
+
+/* skip "enum "/"struct " prefixes */
+#define SKIP_PREFIX(_typestr, _prefix)					\
+	do {								\
+		if (strncmp(_typestr, _prefix, strlen(_prefix)) == 0)	\
+			_typestr += strlen(_prefix) + 1;		\
+	} while (0)
+
+int btf_dump_data(struct btf *btf, struct btf_dump *d,
+		  char *name, __u64 flags, void *ptr,
+		  size_t ptrsize, char *str, const char *expectedval)
+{
+	DECLARE_LIBBPF_OPTS(btf_dump_type_data_opts, opts);
+	int ret = 0, cmp;
+	size_t typesize;
+	__s32 type_id;
+
+	if (flags & BTF_F_COMPACT)
+		opts.compact = true;
+	if (flags & BTF_F_NONAME)
+		opts.skip_names = true;
+	if (flags & BTF_F_ZERO)
+		opts.emit_zeroes = true;
+	SKIP_PREFIX(name, "enum");
+	SKIP_PREFIX(name, "struct");
+	SKIP_PREFIX(name, "union");
+	type_id = btf__find_by_name(btf, name);
+	if (CHECK(type_id <= 0, "find type id",
+		  "no '%s' in BTF: %d\n", name, type_id)) {
+		ret = -ENOENT;
+		goto err;
+	}
+	typesize = btf__resolve_size(btf, type_id);
+	str[0] = '\0';
+	ret = btf_dump__dump_type_data(d, type_id, ptr, ptrsize, &opts);
+	if (typesize <= ptrsize) {
+		if (CHECK(ret != typesize, "btf_dump__dump_type_data",
+			  "failed/unexpected typesize: %d\n", ret))
+			goto err;
+	} else {
+		if (CHECK(ret != -E2BIG, "btf_dump__dump_type_data -E2BIG",
+			  "failed to return -E2BIG: %d\n", ret))
+			goto err;
+		ret = 0;
+	}
+
+	cmp = strcmp(str, expectedval);
+	if (CHECK(cmp, "ensure expected/actual match",
+		  "'%s' does not match expected '%s': %d\n",
+		  str, expectedval, cmp))
+		ret = -EFAULT;
+err:
+	if (ret < 0)
+		btf_dump__free(d);
+	return ret;
+}
+
+#define TEST_BTF_DUMP_DATA(_b, _d, _str, _type, _flags, _expected, ...)	\
+	do {								\
+		char __ptrtype[64] = #_type;				\
+		char *_ptrtype = (char *)__ptrtype;			\
+		_type _ptrdata = __VA_ARGS__;				\
+		void *_ptr = &_ptrdata;					\
+		int _err;						\
+									\
+		_err = btf_dump_data(_b, _d, _ptrtype, _flags, _ptr,	\
+				     sizeof(_type), _str, _expected);	\
+		if (_err < 0)						\
+			return _err;					\
+	} while (0)
+
+/* Use where expected data string matches its stringified declaration */
+#define TEST_BTF_DUMP_DATA_C(_b, _d, _str, _type, _flags, ...)		\
+	TEST_BTF_DUMP_DATA(_b, _d, _str, _type, _flags,			\
+			   "(" #_type ")" #__VA_ARGS__,	__VA_ARGS__)
+
+/* overflow test; pass typesize < expected type size, ensure E2BIG returned */
+#define TEST_BTF_DUMP_DATA_OVER(_b, _d, _str, _type, _typesize, _expected, ...)\
+	do {								\
+		char __ptrtype[64] = #_type;				\
+		char *_ptrtype = (char *)__ptrtype;			\
+		_type _ptrdata = __VA_ARGS__;				\
+		void *_ptr = &_ptrdata;					\
+		int _err;						\
+									\
+		_err = btf_dump_data(_b, _d, _ptrtype, 0, _ptr,		\
+				     _typesize, _str, _expected);	\
+		if (_err < 0)						\
+			return _err;					\
+	} while (0)
+
+#define TEST_BTF_DUMP_VAR(_b, _d, _str, _var, _type, _flags, _expected, ...) \
+	do {								\
+		_type _ptrdata = __VA_ARGS__;				\
+		void *_ptr = &_ptrdata;					\
+		int _err;						\
+									\
+		_err = btf_dump_data(_b, _d, _var, _flags, _ptr,	\
+				     sizeof(_type), _str, _expected);	\
+		if (_err < 0)						\
+			return _err;					\
+	} while (0)
+
+int test_btf_dump_int_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+	/* simple int */
+	TEST_BTF_DUMP_DATA_C(btf, d, str, int, BTF_F_COMPACT, 1234);
+	TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_NONAME,
+			   "1234", 1234);
+	TEST_BTF_DUMP_DATA(btf, d, str, int, 0, "(int)1234\n", 1234);
+
+	/* zero value should be printed at toplevel */
+	TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT, "(int)0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_NONAME,
+			   "0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_ZERO,
+			   "(int)0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, int,
+			   BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+			   "0", 0);
+	TEST_BTF_DUMP_DATA_C(btf, d, str, int, BTF_F_COMPACT, -4567);
+	TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_NONAME,
+			   "-4567", -4567);
+	TEST_BTF_DUMP_DATA(btf, d, str, int, 0, "(int)-4567\n", -4567);
+
+	TEST_BTF_DUMP_DATA_OVER(btf, d, str, int, sizeof(int)-1, "", 1);
+
+	return 0;
+}
+
+/* since the kernel does not likely have any float types in its BTF, we
+ * will need to add some of various sizes.
+ */
+#define TEST_ADD_FLOAT(_btf, _name, _sz)				\
+	do {								\
+		int _err;						\
+									\
+		_err = btf__add_float(_btf, _name, _sz);		\
+		if (CHECK(_err < 0, "btf__add_float",			\
+			  "could not add float of size %d: %d",		\
+			  _sz, _err))					\
+			return _err;					\
+	} while (0)
+
+#define TEST_DUMP_FLOAT(_b, _d, _str, _type, _flags, _data, _sz,	\
+			_expectedval)					\
+	do {								\
+		int _err;						\
+									\
+		_err = btf_dump_data(_b, _d, _type, _flags,		\
+				     _data, _sz, _str, _expectedval);	\
+		if (CHECK(_err < 0, "btf_dump float",			\
+			  "could not dump float data: %d\n", _err))	\
+			return _err;					\
+	} while (0)
+
+int test_btf_dump_float_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+	float t1 = 1.234567;
+	float t2 = -1.234567;
+	float t3 = 0.0;
+	double t4 = 5.678912;
+	double t5 = -5.678912;
+	double t6 = 0.0;
+	long double t7 = 9.876543;
+	long double t8 = -9.876543;
+	long double t9 = 0.0;
+
+	TEST_ADD_FLOAT(btf, "test_float", 4);
+	TEST_DUMP_FLOAT(btf, d, str, "test_float", 0, &t1, 4,
+			"(test_float)1.234567\n");
+	TEST_DUMP_FLOAT(btf, d, str, "test_float", 0, &t2, 4,
+			"(test_float)-1.234567\n");
+	TEST_DUMP_FLOAT(btf, d, str, "test_float", 0, &t3, 4,
+			"(test_float)0.000000\n");
+
+	TEST_ADD_FLOAT(btf, "test_double", 8);
+	TEST_DUMP_FLOAT(btf, d, str, "test_double", 0, &t4, 8,
+			"(test_double)5.678912\n");
+	TEST_DUMP_FLOAT(btf, d, str, "test_double", 0, &t5, 8,
+			"(test_double)-5.678912\n");
+	TEST_DUMP_FLOAT(btf, d, str, "test_double", 0, &t6, 8,
+			"(test_double)0.000000\n");
+
+	TEST_ADD_FLOAT(btf, "test_long_double", 16);
+	TEST_DUMP_FLOAT(btf, d, str, "test_long_double", 0, &t7, 16,
+			"(test_long_double)9.876543\n");
+	TEST_DUMP_FLOAT(btf, d, str, "test_long_double", 0, &t8, 16,
+			"(test_long_double)-9.876543\n");
+	TEST_DUMP_FLOAT(btf, d, str, "test_long_double", 0, &t9, 16,
+			"(test_long_double)0.000000\n");
+
+	return 0;
+}
+
+int test_btf_dump_char_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+	/* simple char */
+	TEST_BTF_DUMP_DATA_C(btf, d, str, char, BTF_F_COMPACT, 100);
+	TEST_BTF_DUMP_DATA(btf, d, str, char, BTF_F_COMPACT | BTF_F_NONAME,
+			   "100", 100);
+	TEST_BTF_DUMP_DATA(btf, d, str, char, 0, "(char)100\n", 100);
+	/* zero value should be printed at toplevel */
+	TEST_BTF_DUMP_DATA(btf, d, str, char, BTF_F_COMPACT, "(char)0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, char, BTF_F_COMPACT | BTF_F_NONAME,
+			   "0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, char, BTF_F_COMPACT | BTF_F_ZERO,
+			   "(char)0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, char,
+			   BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+			   "0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, char, 0, "(char)0\n", 0);
+
+	TEST_BTF_DUMP_DATA_OVER(btf, d, str, char, sizeof(char)-1, "", 100);
+
+	return 0;
+}
+
+int test_btf_dump_typedef_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+	/* simple typedef */
+	TEST_BTF_DUMP_DATA_C(btf, d, str, uint64_t, BTF_F_COMPACT, 100);
+	TEST_BTF_DUMP_DATA(btf, d, str, u64, BTF_F_COMPACT | BTF_F_NONAME,
+			   "1", 1);
+	TEST_BTF_DUMP_DATA(btf, d, str, u64, 0, "(u64)1\n", 1);
+	/* zero value should be printed at toplevel */
+	TEST_BTF_DUMP_DATA(btf, d, str, u64, BTF_F_COMPACT, "(u64)0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, u64, BTF_F_COMPACT | BTF_F_NONAME,
+			   "0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, u64, BTF_F_COMPACT | BTF_F_ZERO,
+			   "(u64)0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, u64,
+			   BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+			   "0", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, u64, 0, "(u64)0\n", 0);
+
+	/* typedef struct */
+	TEST_BTF_DUMP_DATA_C(btf, d, str, atomic_t, BTF_F_COMPACT,
+			     {.counter = (int)1,});
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t, BTF_F_COMPACT | BTF_F_NONAME,
+			   "{1,}", { .counter = 1 });
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t, 0,
+			   "(atomic_t){\n\t.counter = (int)1,\n}\n",
+			   {.counter = 1,});
+	/* typedef with 0 value should be printed at toplevel */
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t, BTF_F_COMPACT, "(atomic_t){}",
+			   {.counter = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t, BTF_F_COMPACT | BTF_F_NONAME,
+			   "{}", {.counter = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t, 0,
+			   "(atomic_t){\n}\n", {.counter = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t, BTF_F_COMPACT | BTF_F_ZERO,
+			   "(atomic_t){.counter = (int)0,}",
+			   {.counter = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t,
+			   BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+			   "{0,}", {.counter = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, atomic_t, BTF_F_ZERO,
+			   "(atomic_t){\n\t.counter = (int)0,\n}\n",
+			   { .counter = 0,});
+
+	/* overflow should show type but not value since it overflows */
+	TEST_BTF_DUMP_DATA_OVER(btf, d, str, atomic_t, sizeof(atomic_t)-1,
+				"(atomic_t){\n", { .counter = 1});
+
+	return 0;
+}
+
+int test_btf_dump_enum_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+	/* enum where enum value does (and does not) exist */
+	TEST_BTF_DUMP_DATA_C(btf, d, str, enum bpf_cmd, BTF_F_COMPACT,
+			     BPF_MAP_CREATE);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd, BTF_F_COMPACT,
+			   "(enum bpf_cmd)BPF_MAP_CREATE", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "BPF_MAP_CREATE",
+			   BPF_MAP_CREATE);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd, 0,
+			   "(enum bpf_cmd)BPF_MAP_CREATE\n",
+			   BPF_MAP_CREATE);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd,
+			   BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+			   "BPF_MAP_CREATE", 0);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd,
+			   BTF_F_COMPACT | BTF_F_ZERO,
+			   "(enum bpf_cmd)BPF_MAP_CREATE",
+			   BPF_MAP_CREATE);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd,
+			   BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+			   "BPF_MAP_CREATE", BPF_MAP_CREATE);
+	TEST_BTF_DUMP_DATA_C(btf, d, str, enum bpf_cmd, BTF_F_COMPACT, 2000);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "2000", 2000);
+	TEST_BTF_DUMP_DATA(btf, d, str, enum bpf_cmd, 0,
+			   "(enum bpf_cmd)2000\n", 2000);
+
+	TEST_BTF_DUMP_DATA_OVER(btf, d, str, enum bpf_cmd,
+				sizeof(enum bpf_cmd) - 1, "", BPF_MAP_CREATE);
+
+	return 0;
+}
+
+int test_btf_dump_struct_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+	DECLARE_LIBBPF_OPTS(btf_dump_type_data_opts, opts);
+	char zerodata[512] = { 0 };
+	char typedata[512];
+	void *fops = typedata;
+	void *skb = typedata;
+	size_t typesize;
+	__s32 type_id;
+	int ret, cmp;
+	char *cmpstr;
+
+	memset(typedata, 255, sizeof(typedata));
+
+	/* simple struct */
+	TEST_BTF_DUMP_DATA_C(btf, d, str, struct btf_enum, BTF_F_COMPACT,
+			     {.name_off = (__u32)3,.val = (__s32)-1,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "{3,-1,}",
+			   { .name_off = 3, .val = -1,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum, 0,
+			   "(struct btf_enum){\n\t.name_off = (__u32)3,\n\t.val = (__s32)-1,\n}\n",
+			   { .name_off = 3, .val = -1,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "{-1,}",
+			   { .name_off = 0, .val = -1,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+			   BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+			   "{0,-1,}",
+			   { .name_off = 0, .val = -1,});
+	/* empty struct should be printed */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum, BTF_F_COMPACT,
+			   "(struct btf_enum){}",
+			   { .name_off = 0, .val = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "{}",
+			   { .name_off = 0, .val = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum, 0,
+			   "(struct btf_enum){\n}\n",
+			   { .name_off = 0, .val = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+			   BTF_F_COMPACT | BTF_F_ZERO,
+			   "(struct btf_enum){.name_off = (__u32)0,.val = (__s32)0,}",
+			   { .name_off = 0, .val = 0,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+			   BTF_F_ZERO,
+			   "(struct btf_enum){\n\t.name_off = (__u32)0,\n\t.val = (__s32)0,\n}\n",
+			   { .name_off = 0, .val = 0,});
+
+	/* struct with pointers */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, BTF_F_COMPACT,
+			   "(struct list_head){.next = (struct list_head *)0x1,}",
+			   { .next = (struct list_head *)1 });
+	TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, 0,
+			   "(struct list_head){\n\t.next = (struct list_head *)0x1,\n}\n",
+			   { .next = (struct list_head *)1 });
+	/* NULL pointer should not be displayed */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, BTF_F_COMPACT,
+			   "(struct list_head){}",
+			   { .next = (struct list_head *)0 });
+	TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, 0,
+			   "(struct list_head){\n}\n",
+			   { .next = (struct list_head *)0 });
+
+	/* struct with function pointers */
+	type_id = btf__find_by_name(btf, "file_operations");
+	if (CHECK(type_id <= 0, "find type id",
+		  "no 'struct file_operations' in BTF: %d\n", type_id))
+		return -ENOENT;
+	typesize = btf__resolve_size(btf, type_id);
+	str[0] = '\0';
+
+	ret = btf_dump__dump_type_data(d, type_id, fops, typesize, &opts);
+	if (CHECK(ret != typesize,
+		  "dump file_operations is successful",
+		  "unexpected return value dumping file_operations '%s': %d\n",
+		  str, ret))
+		return -EINVAL;
+
+	cmpstr = "(struct file_operations){\n\t.owner = (struct module *)0xffffffffffffffff,\n\t.llseek = (loff_t(*)(struct file *, loff_t, int))0xffffffffffffffff,";
+	cmp = strncmp(str, cmpstr, strlen(cmpstr));
+	if (CHECK(cmp != 0, "check file_operations dump",
+		  "file_operations '%s' did not match expected\n",
+		  str))
+		return -EINVAL;
+
+	/* struct with char array */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, BTF_F_COMPACT,
+			   "(struct bpf_prog_info){.name = (char[])['f','o','o',],}",
+			   { .name = "foo",});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "{['f','o','o',],}",
+			   {.name = "foo",});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, 0,
+			   "(struct bpf_prog_info){\n\t.name = (char[])[\n\t\t'f',\n\t\t\'o',\n\t\t'o',\n\t],\n}\n",
+			   {.name = "foo",});
+	/* leading null char means do not display string */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, BTF_F_COMPACT,
+			   "(struct bpf_prog_info){}",
+			   {.name = {'\0', 'f', 'o', 'o'}});
+	/* handle non-printable characters */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, BTF_F_COMPACT,
+			   "(struct bpf_prog_info){.name = (char[])[1,2,3,],}",
+			   { .name = {1, 2, 3, 0}});
+
+	/* struct with non-char array */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, BTF_F_COMPACT,
+			   "(struct __sk_buff){.cb = (__u32[])[1,2,3,4,5,],}",
+			   { .cb = {1, 2, 3, 4, 5,},});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "{[1,2,3,4,5,],}",
+			   { .cb = { 1, 2, 3, 4, 5},});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, 0,
+			   "(struct __sk_buff){\n\t.cb = (__u32[])[\n\t\t1,\n\t\t2,\n\t\t3,\n\t\t4,\n\t\t5,\n\t],\n}\n",
+			   { .cb = { 1, 2, 3, 4, 5},});
+	/* For non-char, arrays, show non-zero values only */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, BTF_F_COMPACT,
+			   "(struct __sk_buff){.cb = (__u32[])[0,0,1,0,0,],}",
+			   { .cb = { 0, 0, 1, 0, 0},});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, 0,
+			   "(struct __sk_buff){\n\t.cb = (__u32[])[\n\t\t0,\n\t\t0,\n\t\t1,\n\t\t0,\n\t\t0,\n\t],\n}\n",
+			   { .cb = { 0, 0, 1, 0, 0},});
+
+	/* struct with bitfields */
+	TEST_BTF_DUMP_DATA_C(btf, d, str, struct bpf_insn, BTF_F_COMPACT,
+		{.code = (__u8)1,.dst_reg = (__u8)0x2,.src_reg = (__u8)0x3,.off = (__s16)4,.imm = (__s32)5,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_insn,
+			   BTF_F_COMPACT | BTF_F_NONAME,
+			   "{1,0x2,0x3,4,5,}",
+			   { .code = 1, .dst_reg = 0x2, .src_reg = 0x3, .off = 4,
+			     .imm = 5,});
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_insn, 0,
+			   "(struct bpf_insn){\n\t.code = (__u8)1,\n\t.dst_reg = (__u8)0x2,\n\t.src_reg = (__u8)0x3,\n\t.off = (__s16)4,\n\t.imm = (__s32)5,\n}\n",
+			   {.code = 1, .dst_reg = 2, .src_reg = 3, .off = 4, .imm = 5});
+
+	/* zeroed bitfields should not be displayed */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_insn, BTF_F_COMPACT,
+			   "(struct bpf_insn){.dst_reg = (__u8)0x1,}",
+			   { .code = 0, .dst_reg = 1});
+
+	/* struct with enum bitfield */
+	type_id = btf__find_by_name(btf, "nft_cmp_expr");
+	if (CHECK(type_id <= 0, "find nft_cmp_expr",
+		  "no 'struct nft_cmp_expr' in BTF: %d\n", type_id))
+		return -ENOENT;
+	typesize = btf__resolve_size(btf, type_id);
+	str[0] = '\0';
+
+	opts.emit_zeroes = true;
+	ret = btf_dump__dump_type_data(d, type_id, zerodata, typesize, &opts);
+	if (CHECK(ret != typesize,
+		  "dump nft_cmp_expr is successful",
+		  "unexpected return value dumping nft_cmp_expr '%s': %d\n",
+		  str, ret))
+		return -EINVAL;
+
+	if (CHECK(strstr(str, "NFT_CMP_EQ") == NULL,
+		  "verify enum value shown for bitfield",
+		  "bitfield value not present in '%s'\n", str))
+		return -EINVAL;
+
+	/* struct with nested anon union */
+	TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_sock_ops, BTF_F_COMPACT,
+			   "(struct bpf_sock_ops){.op = (__u32)1,(union){.args = (__u32[])[1,2,3,4,],.reply = (__u32)1,.replylong = (__u32[])[1,2,3,4,],},}",
+			   { .op = 1, .args = { 1, 2, 3, 4}});
+
+	/* union with nested struct */
+	TEST_BTF_DUMP_DATA(btf, d, str, union bpf_iter_link_info, BTF_F_COMPACT,
+			   "(union bpf_iter_link_info){.map = (struct){.map_fd = (__u32)1,},}",
+			   { .map = { .map_fd = 1 }});
+
+	/* struct skb with nested structs/unions; because type output is so
+	 * complex, we don't do a string comparison, just verify we return
+	 * the type size as the amount of data displayed.
+	 */
+	type_id = btf__find_by_name(btf, "sk_buff");
+	if (CHECK(type_id <= 0, "find type id",
+		  "no 'struct sk_buff' in BTF: %d\n", type_id))
+		return -ENOENT;
+	typesize = btf__resolve_size(btf, type_id);
+	str[0] = '\0';
+
+	ret = btf_dump__dump_type_data(d, type_id, skb, typesize, &opts);
+	if (CHECK(ret != typesize,
+		  "dump sk_buff is successful",
+		  "unexpected return value dumping sk_buff '%s': %d\n",
+		  str, ret))
+		return -EINVAL;
+
+	/* overflow bpf_sock_ops struct with final element nonzero/zero.
+	 * Regardless of the value of the final field, we don't have all the
+	 * data we need to display it, so we should trigger an overflow.
+	 * In other words oveflow checking should trump "is field zero?"
+	 * checks because if we've overflowed, it shouldn't matter what the
+	 * field is - we can't trust its value so shouldn't display it.
+	 */
+	TEST_BTF_DUMP_DATA_OVER(btf, d, str, struct bpf_sock_ops,
+				sizeof(struct bpf_sock_ops) - 1,
+				"(struct bpf_sock_ops){\n\t.op = (__u32)1,\n",
+				{ .op = 1, .skb_tcp_flags = 2});
+	TEST_BTF_DUMP_DATA_OVER(btf, d, str, struct bpf_sock_ops,
+				sizeof(struct bpf_sock_ops) - 1,
+				"(struct bpf_sock_ops){\n\t.op = (__u32)1,\n",
+				{ .op = 1, .skb_tcp_flags = 0});
+
+	return 0;
+}
+
+int test_btf_dump_var_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+
+	TEST_BTF_DUMP_VAR(btf, d, str, "cpu_number", int, BTF_F_COMPACT,
+			  "int cpu_number = (int)100", 100);
+	TEST_BTF_DUMP_VAR(btf, d, str, "cpu_profile_flip", int, BTF_F_COMPACT,
+			  "static int cpu_profile_flip = (int)2", 2);
+
+	return 0;
+}
+
+int test_btf_datasec(struct btf *btf, struct btf_dump *d, char *str,
+		     const char *name, const char *expectedval,
+		     void *data, size_t data_sz)
+{
+	DECLARE_LIBBPF_OPTS(btf_dump_type_data_opts, opts);
+	int ret = 0, cmp;
+	size_t secsize;
+	__s32 type_id;
+
+	opts.compact = true;
+
+	type_id = btf__find_by_name(btf, name);
+	if (CHECK(type_id <= 0, "find type id",
+		  "no '%s' in BTF: %d\n", name, type_id))
+		return -ENOENT;
+
+	secsize = btf__resolve_size(btf, type_id);
+	if (CHECK(secsize != 0, "verify section size",
+		  "unexpected section size %ld for %s\n", secsize, name))
+		return -EINVAL;
+
+	str[0] = '\0';
+	ret = btf_dump__dump_type_data(d, type_id, data, data_sz, &opts);
+	if (CHECK(ret != 0, "btf_dump__dump_type_data",
+		  "failed/unexpected return value: %d\n", ret))
+		return ret;
+
+	cmp = strcmp(str, expectedval);
+	if (CHECK(cmp, "ensure expected/actual match",
+		  "'%s' does not match expected '%s': %d\n",
+		  str, expectedval, cmp))
+		ret = -EFAULT;
+
+	return ret;
+}
+
+int test_btf_dump_datasec_data(char *str)
+{
+	struct btf *btf = btf__parse("xdping_kern.o", NULL);
+	struct btf_dump_opts opts = { .ctx = str };
+	char license[4] = "GPL";
+	struct btf_dump *d;
+
+	if (CHECK(!btf, "get prog BTF", "xdping_kern.o BTF not found"))
+		return -ENOENT;
+
+	d = btf_dump__new(btf, NULL, &opts, btf_dump_snprintf);
+
+	if (CHECK(!d, "new dump", "could not create BTF dump"))
+		return -ENOENT;
+
+	if (test_btf_datasec(btf, d, str, "license",
+			     "SEC(\"license\") char[] _license = (char[])['G','P','L',];",
+			     license, sizeof(license)))
+		return -EINVAL;
+
+	return 0;
+}
+
+void test_btf_dump_data(void)
+{
+	struct btf *btf = libbpf_find_kernel_btf();
+	char str[STRSIZE];
+	struct btf_dump_opts opts = { .ctx = str };
+	struct btf_dump *d;
+
+	if (CHECK(!btf, "get kernel BTF", "no kernel BTF found"))
+		return;
+
+	d = btf_dump__new(btf, NULL, &opts, btf_dump_snprintf);
+
+	if (CHECK(!d, "new dump", "could not create BTF dump"))
+		return;
+
+	/* Verify type display for various types. */
+	if (test_btf_dump_int_data(btf, d, str))
+		return;
+	if (test_btf_dump_float_data(btf, d, str))
+		return;
+	if (test_btf_dump_char_data(btf, d, str))
+		return;
+	if (test_btf_dump_typedef_data(btf, d, str))
+		return;
+	if (test_btf_dump_enum_data(btf, d, str))
+		return;
+	if (test_btf_dump_struct_data(btf, d, str))
+		return;
+	if (test_btf_dump_var_data(btf, d, str))
+		return;
+	btf_dump__free(d);
+	btf__free(btf);
+
+	/* verify datasec display */
+	if (test_btf_dump_datasec_data(str))
+		return;
+
+}
+
 void test_btf_dump() {
 	int i;
 
@@ -245,4 +881,6 @@ void test_btf_dump() {
 	}
 	if (test__start_subtest("btf_dump: incremental"))
 		test_btf_dump_incremental();
+	if (test__start_subtest("btf_dump: data"))
+		test_btf_dump_data();
 }
-- 
1.8.3.1