[v2,bpf-next,01/13] libbpf: add support to btf__add_fwd() for ENUM64

Commit Message

Alan Maguire April 24, 2024, 3:47 p.m. UTC

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 <[e-mail]>
---
 tools/lib/bpf/btf.c | 7 ++++++-
 tools/lib/bpf/btf.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

Comments

Andrii Nakryiko April 26, 2024, 10:56 p.m. UTC | #1

On Wed, Apr 24, 2024 at 8:48 AM Alan Maguire <[e-mail]> 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 <[e-mail]>
> ---
>  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
>

Patch

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,
 };
 
 LIBBPF_API int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind);