Re: [PATCH bpf-next v5 1/6] bpf: Introduce load-acquire and store-release instructions

Alexei Starovoitov
2025-03-04T00:24:25Z

On Mon, Mar 3, 2025 at 4:13 PM Peilin Ye <yepeilin@google.com> wrote:
>
> switch (insn->imm) {
> @@ -7780,6 +7813,24 @@ static int check_atomic(struct bpf_verifier_env *env, struct bpf_insn *insn)
> case BPF_XCHG:
> case BPF_CMPXCHG:
> return check_atomic_rmw(env, insn);
> + case BPF_LOAD_ACQ:
> +#ifndef CONFIG_64BIT
> + if (BPF_SIZE(insn->code) == BPF_DW) {
> + verbose(env,
> + "64-bit load-acquires are only supported on 64-bit arches\n");
> + return -EOPNOTSUPP;
> + }
> +#endif

Your earlier proposal of:
if (BPF_SIZE(insn->code) == BPF_DW && BITS_PER_LONG != 64) {

was cleaner.
Why did you pick ifndef ?

> + return check_atomic_load(env, insn);
> + case BPF_STORE_REL:
> +#ifndef CONFIG_64BIT
> + if (BPF_SIZE(insn->code) == BPF_DW) {
> + verbose(env,
> + "64-bit store-releases are only supported on 64-bit arches\n");
> + return -EOPNOTSUPP;
> + }
> +#endif