On Tue, Feb 9, 2021 at 7:03 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote:
>
> Add a new kind value, expand the kind bitfield, add a macro for
> parsing the additional u32.
>
> Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> ---
> include/uapi/linux/btf.h | 10 ++++++++--
> tools/include/uapi/linux/btf.h | 10 ++++++++--
> 2 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/include/uapi/linux/btf.h b/include/uapi/linux/btf.h
> index 5a667107ad2c..e713430cb033 100644
> --- a/include/uapi/linux/btf.h
> +++ b/include/uapi/linux/btf.h
> @@ -52,7 +52,7 @@ struct btf_type {
> };
> };
>
> -#define BTF_INFO_KIND(info) (((info) >> 24) & 0x0f)
> +#define BTF_INFO_KIND(info) (((info) >> 24) & 0x1f)
> #define BTF_INFO_VLEN(info) ((info) & 0xffff)
> #define BTF_INFO_KFLAG(info) ((info) >> 31)
>
> @@ -72,7 +72,8 @@ struct btf_type {
> #define BTF_KIND_FUNC_PROTO 13 /* Function Proto */
> #define BTF_KIND_VAR 14 /* Variable */
> #define BTF_KIND_DATASEC 15 /* Section */
> -#define BTF_KIND_MAX BTF_KIND_DATASEC
> +#define BTF_KIND_FLOAT 16 /* Floating point */
> +#define BTF_KIND_MAX BTF_KIND_FLOAT
> #define NR_BTF_KINDS (BTF_KIND_MAX + 1)
>
> /* For some specific BTF_KIND, "struct btf_type" is immediately
> @@ -169,4 +170,9 @@ struct btf_var_secinfo {
> __u32 size;
> };
>
> +/* BTF_KIND_FLOAT is followed by a u32 and the following
what's the point of that u32, if BTF_FLOAT_BITS() is just t->size * 8?
Why adding this complexity. BTF_KIND_INT has bits because we had an
inconvenient bitfield encoding as a special BTF_KIND_INT types, which
we since stopped using in favor of encoding bitfield sizes and offsets
inside struct/union fields. I don't think there is any need for that
with FLOAT, so why waste space and add complexity and possibility for
inconsistencies?
Disclaimer: I'm in a "just BTF_KIND_INT encoding bit for
floating-point numbers" camp.
> + * is the 32 bits arrangement:
> + */
> +#define BTF_FLOAT_BITS(VAL) ((VAL) & 0x000000ff)
> +
> #endif /* _UAPI__LINUX_BTF_H__ */
> diff --git a/tools/include/uapi/linux/btf.h b/tools/include/uapi/linux/btf.h
> index 5a667107ad2c..e713430cb033 100644
> --- a/tools/include/uapi/linux/btf.h
> +++ b/tools/include/uapi/linux/btf.h
> @@ -52,7 +52,7 @@ struct btf_type {
> };
> };
>
> -#define BTF_INFO_KIND(info) (((info) >> 24) & 0x0f)
> +#define BTF_INFO_KIND(info) (((info) >> 24) & 0x1f)
> #define BTF_INFO_VLEN(info) ((info) & 0xffff)
> #define BTF_INFO_KFLAG(info) ((info) >> 31)
>
> @@ -72,7 +72,8 @@ struct btf_type {
> #define BTF_KIND_FUNC_PROTO 13 /* Function Proto */
> #define BTF_KIND_VAR 14 /* Variable */
> #define BTF_KIND_DATASEC 15 /* Section */
> -#define BTF_KIND_MAX BTF_KIND_DATASEC
> +#define BTF_KIND_FLOAT 16 /* Floating point */
> +#define BTF_KIND_MAX BTF_KIND_FLOAT
> #define NR_BTF_KINDS (BTF_KIND_MAX + 1)
>
> /* For some specific BTF_KIND, "struct btf_type" is immediately
> @@ -169,4 +170,9 @@ struct btf_var_secinfo {
> __u32 size;
> };
>
> +/* BTF_KIND_FLOAT is followed by a u32 and the following
> + * is the 32 bits arrangement:
> + */
> +#define BTF_FLOAT_BITS(VAL) ((VAL) & 0x000000ff)
> +
> #endif /* _UAPI__LINUX_BTF_H__ */
> --
> 2.29.2
>
