bpf: btf: Remove unused bits from uapi/linux/btf.h
This patch does the followings:
1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can
raise it later.
2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are
currently encoded at the highest bit of a u32.
It is because the current use case does not require supporting
parent type (i.e type_id referring to a type in another BTF file).
It also does not support referring to a string in ELF.
The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced
by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are
defined in btf.c instead of uapi/linux/btf.h.
3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough.
There is unused bits headroom if we ever needed it later.
4. The root bit in BTF_INFO is also removed because it is not
used in the current use case.
5. Remove BTF_INT_VARARGS since func type is not supported now.
The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits.
The above can be added back later because the verifier
ensures the unused bits are zeros.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2 files changed