[RFC bpf-next 01/13] libbpf: add support to btf__add_fwd() for ENUM64

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

Forward declaration of BTF_KIND_ENUM64 is added by supporting BTF_FWD_ENUM64
as an enumerated value for btf_fwd_kind; an ENUM64 forward is an 8-byte
signed enum64 with no values.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
 tools/lib/bpf/btf.c | 7 ++++++-
 tools/lib/bpf/btf.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 2d0840ef599a..dcff6c29c851 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -2418,7 +2418,7 @@ int btf__add_enum64_value(struct btf *btf, const char *name, __u64 value)
  * Append new BTF_KIND_FWD type with:
  *   - *name*, non-empty/non-NULL name;
  *   - *fwd_kind*, kind of forward declaration, one of BTF_FWD_STRUCT,
- *     BTF_FWD_UNION, or BTF_FWD_ENUM;
+ *     BTF_FWD_UNION, BTF_FWD_ENUM or BTF_FWD_ENUM64;
  * Returns:
  *   - >0, type ID of newly added BTF type;
  *   - <0, on error.
@@ -2446,6 +2446,11 @@ int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind)
 		 * values; we also assume a standard 4-byte size for it
 		 */
 		return btf__add_enum(btf, name, sizeof(int));
+	case BTF_FWD_ENUM64:
+		/* enum64 forward is similarly just an enum64 with no enum
+		 * values; assume 8 byte size, signed.
+		 */
+		return btf__add_enum64(btf, name, 8, true);
 	default:
 		return libbpf_err(-EINVAL);
 	}
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 8e6880d91c84..47d3e00b25c7 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -194,6 +194,7 @@ enum btf_fwd_kind {
 	BTF_FWD_STRUCT = 0,
 	BTF_FWD_UNION = 1,
 	BTF_FWD_ENUM = 2,
+	BTF_FWD_ENUM64 = 3,
 };
 
 LIBBPF_API int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind);
-- 
2.39.3