Re: [PATCH RFC 2/6] libbpf: Add BTF_KIND_FLOAT support

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Tue, Feb 9, 2021 at 7:04 PM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>
> The logic follows that of BTF_KIND_INT most of the time, some functions
> are even unified to work on both. Sanitization replaces BTF_KIND_FLOATs
> with equally-sized BTF_KIND_INTs on older kernels.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  tools/lib/bpf/btf.c             | 85 +++++++++++++++++++++++----------
>  tools/lib/bpf/btf.h             | 13 +++++
>  tools/lib/bpf/btf_dump.c        |  4 ++
>  tools/lib/bpf/libbpf.c          | 32 ++++++++++++-
>  tools/lib/bpf/libbpf.map        |  5 ++
>  tools/lib/bpf/libbpf_internal.h |  4 ++
>  6 files changed, 118 insertions(+), 25 deletions(-)
>

[...]

> @@ -2445,6 +2450,12 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
>                 } else if (!has_func_global && btf_is_func(t)) {
>                         /* replace BTF_FUNC_GLOBAL with BTF_FUNC_STATIC */
>                         t->info = BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0);
> +               } else if (!has_float && btf_is_float(t)) {
> +                       /* replace FLOAT with INT */
> +                       __u8 nr_bits = btf_float_bits(t);
> +

nit: no need for extra variable, just use it inline below

> +                       t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
> +                       *(int *)(t + 1) = BTF_INT_ENC(0, 0, nr_bits);
>                 }
>         }
>  }
> @@ -3882,6 +3893,18 @@ static int probe_kern_btf_datasec(void)
>                                              strs, sizeof(strs)));
>  }

[...]