[PATCH bpf-next 4/5] bpf: allow kind_flag for BTF type and decl tags

[Ihor Solodrai <ihor.solodrai@xxxxx>]

BTF type tags and decl tags now may have info->kflag set to 1,
changing the semantics of the tag.

Change BTF verification to permit BTF that makes use of this feature:
  * remove kflag check in btf_decl_tag_check_meta(), as both values
    are valid
  * allow kflag to be set for BTF_KIND_TYPE_TAG type in
    btf_ref_type_check_meta()

Modify a selftest checking for kflag in decl_tag accordingly.

Signed-off-by: Ihor Solodrai <ihor.solodrai@xxxxx>
---
 kernel/bpf/btf.c                             | 7 +------
 tools/testing/selftests/bpf/prog_tests/btf.c | 4 +---
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 8396ce1d0fba..becdec583e00 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -2575,7 +2575,7 @@ static int btf_ref_type_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
-	if (btf_type_kflag(t)) {
+	if (btf_type_kflag(t) && BTF_INFO_KIND(t->info) != BTF_KIND_TYPE_TAG) {
 		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
 		return -EINVAL;
 	}
@@ -4944,11 +4944,6 @@ static s32 btf_decl_tag_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
-	if (btf_type_kflag(t)) {
-		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
-		return -EINVAL;
-	}
-
 	component_idx = btf_type_decl_tag(t)->component_idx;
 	if (component_idx < -1) {
 		btf_verifier_log_type(env, t, "Invalid component_idx");
diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index e63d74ce046f..aab9ad88c845 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -3866,7 +3866,7 @@ static struct btf_raw_test raw_tests[] = {
 	.err_str = "vlen != 0",
 },
 {
-	.descr = "decl_tag test #8, invalid kflag",
+	.descr = "decl_tag test #8, tag with kflag",
 	.raw_types = {
 		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
 		BTF_VAR_ENC(NAME_TBD, 1, 0),			/* [2] */
@@ -3881,8 +3881,6 @@ static struct btf_raw_test raw_tests[] = {
 	.key_type_id = 1,
 	.value_type_id = 1,
 	.max_entries = 1,
-	.btf_load_err = true,
-	.err_str = "Invalid btf_info kind_flag",
 },
 {
 	.descr = "decl_tag test #9, var, invalid component_idx",
-- 
2.48.1