selftests/bpf: Add tests for type tag order validation

Add a few test cases that ensure we catch cases of badly ordered type
tags in modifier chains.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220419164608.1990559-3-memxor@gmail.com

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

@@ -3973,6 +3973,105 @@ static struct btf_raw_test raw_tests[] = {
 	.value_type_id = 1,
 	.max_entries = 1,
 },
+{
+	.descr = "type_tag test #2, type tag order",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_CONST_ENC(3),				/* [2] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 1),			/* [3] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0tag"),
+	.map_type = BPF_MAP_TYPE_ARRAY,
+	.map_name = "tag_type_check_btf",
+	.key_size = sizeof(int),
+	.value_size = 4,
+	.key_type_id = 1,
+	.value_type_id = 1,
+	.max_entries = 1,
+	.btf_load_err = true,
+	.err_str = "Type tags don't precede modifiers",
+},
+{
+	.descr = "type_tag test #3, type tag order",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 3),			/* [2] */
+		BTF_CONST_ENC(4),				/* [3] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 1),			/* [4] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0tag\0tag"),
+	.map_type = BPF_MAP_TYPE_ARRAY,
+	.map_name = "tag_type_check_btf",
+	.key_size = sizeof(int),
+	.value_size = 4,
+	.key_type_id = 1,
+	.value_type_id = 1,
+	.max_entries = 1,
+	.btf_load_err = true,
+	.err_str = "Type tags don't precede modifiers",
+},
+{
+	.descr = "type_tag test #4, type tag order",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_TYPEDEF_ENC(NAME_TBD, 3),			/* [2] */
+		BTF_CONST_ENC(4),				/* [3] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 1),			/* [4] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0tag\0tag"),
+	.map_type = BPF_MAP_TYPE_ARRAY,
+	.map_name = "tag_type_check_btf",
+	.key_size = sizeof(int),
+	.value_size = 4,
+	.key_type_id = 1,
+	.value_type_id = 1,
+	.max_entries = 1,
+	.btf_load_err = true,
+	.err_str = "Type tags don't precede modifiers",
+},
+{
+	.descr = "type_tag test #5, type tag order",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 3),			/* [2] */
+		BTF_CONST_ENC(1),				/* [3] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 2),			/* [4] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0tag\0tag"),
+	.map_type = BPF_MAP_TYPE_ARRAY,
+	.map_name = "tag_type_check_btf",
+	.key_size = sizeof(int),
+	.value_size = 4,
+	.key_type_id = 1,
+	.value_type_id = 1,
+	.max_entries = 1,
+},
+{
+	.descr = "type_tag test #6, type tag order",
+	.raw_types = {
+		BTF_PTR_ENC(2),					/* [1] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 3),			/* [2] */
+		BTF_CONST_ENC(4),				/* [3] */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [4] */
+		BTF_PTR_ENC(6),					/* [5] */
+		BTF_CONST_ENC(2),				/* [6] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0tag"),
+	.map_type = BPF_MAP_TYPE_ARRAY,
+	.map_name = "tag_type_check_btf",
+	.key_size = sizeof(int),
+	.value_size = 4,
+	.key_type_id = 1,
+	.value_type_id = 1,
+	.max_entries = 1,
+	.btf_load_err = true,
+	.err_str = "Type tags don't precede modifiers",
+},
 
 }; /* struct btf_raw_test raw_tests[] */