Re: [PATCH bpf-next v2 13/18] bpf: Distinguish fixed- and variable-size kfunc mem args with MEM_FIXED_SIZE

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2026-07-24 at 12:08 -0700, Amery Hung wrote:
> A kfunc memory-pointer argument comes in two flavors: a fixed-size buffer
> whose access size is derived from the pointed-to BTF type, and a
> variable-size buffer paired with a following __sz/__szk size argument.
> Both were represented by separate kfunc_ptr_arg_type values
> (KF_ARG_PTR_TO_MEM vs KF_ARG_PTR_TO_MEM_SIZE) with the pointer classified
> as the latter when a size argument followed.
> 
> Mirror how helpers describe the same distinction: classify both as
> KF_ARG_PTR_TO_MEM and OR in MEM_FIXED_SIZE for the fixed-size case, just
> as helpers use ARG_PTR_TO_MEM | MEM_FIXED_SIZE. The switches now key on
> base_type(kf_arg_type) so the flag rides along, and the KF_ARG_PTR_TO_MEM
> handler either resolves the size from BTF (MEM_FIXED_SIZE) or falls
> through to the mem/size-pair check, which validates the buffer against the
> following size register and skips it. No functional change.
> 
> Signed-off-by: Amery Hung <ameryhung@gmail.com>
> ---

Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>

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