Re: [PATCH bpf-next 4/5] bpf: simplify the bpf_is_reg64() signature

> bpf: simplify the bpf_is_reg64() signature
>
> After the previous commit this function is only used in a context
> where destination register's property is queried.
> Hence, simplify the function by removing the 'regno' and 't'
> parameters.

The changelog appears to undercount the removed parameters. Looking at the
actual signature change:

include/linux/bpf_verifier.h:
-bool bpf_is_reg64(struct bpf_insn *insn, u32 regno, struct bpf_reg_state *reg, enum bpf_reg_arg_type t);
+bool bpf_is_reg64(struct bpf_insn *insn);

Three parameters are dropped: regno, reg, and t. The message mentions only
'regno' and 't', omitting 'struct bpf_reg_state *reg'.

The reg parameter isn't incidental: it was the only pointer argument, both
call sites passed NULL for it, and its removal retires the contract that
the BPF_STX SRC_OP arm relied on. The fixups.c comment at line 622
explicitly documented this:

kernel/bpf/fixups.c:
    /* NOTE: arg "reg" (the fourth one) is only used for
     *       BPF_STX + SRC_OP, so it is safe to pass NULL
     *       here.
     */
    if (bpf_is_reg64(&insn)) {

Could the message say 'removing the regno, reg and t parameters' (or
'removing all parameters except insn') so readers following the series can
account for all three removals?


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