From f7a6b9eaff3e6693ba3b19c5812e28538049bbf2 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Fri, 17 Apr 2026 15:30:18 +0100 Subject: bpf: Extend BTF UAPI vlen, kinds to use unused bits BTF maximum vlen is encoded using 16 bits with a maximum vlen of 65535. This has sufficed for structs, function parameters and enumerated type values. However, with upcoming BTF location information - in particular information about inline sites - this limit is surpassed. Use bits 16-23 - currently unused in BTF info - to extend to 24 bits, giving a max vlen of (2^24 - 1), or 16 million. Also extend BTF kind encoding from 5 to 7 bits, giving a maximum available number of kinds of 128. Since with the BTF location work we use another 3 kinds, we are fast approaching the current limit of 32. Convert BTF_MAX_* values to enums to allow them to be encoded in kernel BTF; this will allow us to detect if the running kernel supports a 24-bit vlen or not. Add one for max _possible_ (not used) kind. Fix up a few places in the kernel where a 16-bit vlen is assumed; remove BTF_INFO_MASK as now all bits are used. The vlen expansion was suggested by Andrii in [1]; the kind expansion is tackled here too as it may be needed also to support new kinds in BTF. [1] https://lore.kernel.org/bpf/CAEf4BzZx=X6vGqcA8SPU6D+v6k+TR=ZewebXMuXtpmML058piw@mail.gmail.com/ Suggested-by: Andrii Nakryiko Signed-off-by: Alan Maguire Acked-by: Mykyta Yatsenko Link: https://lore.kernel.org/r/20260417143023.1551481-2-alan.maguire@oracle.com Signed-off-by: Alexei Starovoitov --- include/linux/btf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/btf.h b/include/linux/btf.h index 48108471c5b1..c82d0d689059 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -415,12 +415,12 @@ static inline bool btf_type_is_array(const struct btf_type *t) return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY; } -static inline u16 btf_type_vlen(const struct btf_type *t) +static inline u32 btf_type_vlen(const struct btf_type *t) { return BTF_INFO_VLEN(t->info); } -static inline u16 btf_vlen(const struct btf_type *t) +static inline u32 btf_vlen(const struct btf_type *t) { return btf_type_vlen(t); } -- cgit v1.2.3