On Wed, Apr 24, 2024 at 8:48 AM Alan Maguire <alan.maguire@xxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
> ---
> 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..44afae098369 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, sizeof(__u64), 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,
one can argue that having BTF_FWD_ENUM64 isn't necessary if we allow
to use BTF_KIND_ENUM and BTF_KIND_ENUM64 interchangeably (when
resolving such fwd declarations). "Original" enum can record size 8,
so you can have enum64 forwarding with just BTF_KIND_ENUM vlen=0
size=8? Would that be sufficient?
> };
>
> LIBBPF_API int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind);
> --
> 2.31.1
>
