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bpf@vger.kernel.org Archived-At: List-Archive: List-Post: On 2/19/21 5:00 AM, Ilya Leoshkevich wrote: > On Thu, 2021-02-18 at 21:41 -0800, Yonghong Song wrote: >> >> >> On 2/18/21 6:25 PM, Ilya Leoshkevich wrote: >>> Also document the expansion of the kind bitfield. >>> >>> Signed-off-by: Ilya Leoshkevich >>> --- >>>   Documentation/bpf/btf.rst | 17 +++++++++++++++-- >>>   1 file changed, 15 insertions(+), 2 deletions(-) >>> >>> diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst >>> index 44dc789de2b4..4f25c992d442 100644 >>> --- a/Documentation/bpf/btf.rst >>> +++ b/Documentation/bpf/btf.rst >>> @@ -84,6 +84,7 @@ sequentially and type id is assigned to each >>> recognized type starting from id >>>       #define BTF_KIND_FUNC_PROTO     13      /* Function >>> Proto       */ >>>       #define BTF_KIND_VAR            14      /* Variable     */ >>>       #define BTF_KIND_DATASEC        15      /* Section      */ >>> +    #define BTF_KIND_FLOAT          16      /* Floating >>> point       */ >>> >>>   Note that the type section encodes debug info, not just pure >>> types. >>>   ``BTF_KIND_FUNC`` is not a type, and it represents a defined >>> subprogram. >>> @@ -95,8 +96,8 @@ Each type contains the following common data:: >>>           /* "info" bits arrangement >>>            * bits  0-15: vlen (e.g. # of struct's members) >>>            * bits 16-23: unused >>> -         * bits 24-27: kind (e.g. int, ptr, array...etc) >>> -         * bits 28-30: unused >>> +         * bits 24-28: kind (e.g. int, ptr, array...etc) >>> +         * bits 29-30: unused >>>            * bit     31: kind_flag, currently used by >>>            *             struct, union and fwd >>>            */ >>> @@ -452,6 +453,18 @@ map definition. >>>     * ``offset``: the in-section offset of the variable >>>     * ``size``: the size of the variable in bytes >>> >>> +2.2.16 BTF_KIND_FLOAT >>> +~~~~~~~~~~~~~~~~~~~~~ >>> + >>> +``struct btf_type`` encoding requirement: >>> + * ``name_off``: any valid offset >>> + * ``info.kind_flag``: 0 >>> + * ``info.kind``: BTF_KIND_FLOAT >>> + * ``info.vlen``: 0 >>> + * ``size``: the size of the float type in bytes. >> >> I would be good to specify the allowed size in bytes 2, multiple of >> 4. >> currently we do not have a maximum value, maybe 128. have a float >> type >> something like 2^10 seems strange. > > I tried to write this all down and realized it's simpler to enumerate > the allowed values: 2, 4, 8, 12 and 16. I don't think there are 32-byte > floats on any of the architectures supported by the kernel. This make senses. My above 128 means 128bits (sorry!), which is 16 bytes, align with what you suggested. >