On Mon, Apr 25, 2022 at 03:18:51AM +0530, Kumar Kartikeya Dwivedi wrote:
> +
> +static u32 bpf_kptr_xchg_btf_id;
> +
> +const struct bpf_func_proto bpf_kptr_xchg_proto = {
> + .func = bpf_kptr_xchg,
> + .gpl_only = false,
> + .ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
> + .ret_btf_id = &bpf_kptr_xchg_btf_id,
> + .arg1_type = ARG_PTR_TO_KPTR,
> + .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL | OBJ_RELEASE,
> + .arg2_btf_id = &bpf_kptr_xchg_btf_id,
> +};
I've tweaked above with:
+/* Unlike other PTR_TO_BTF_ID helpers the btf_id in bpf_kptr_xchg()
+ * helper is determined dynamically by the verifier.
+ */
+#define BPF_PTR_POISON ((void *)((0xeB9FUL << 2) + POISON_POINTER_DELTA))
+
+const struct bpf_func_proto bpf_kptr_xchg_proto = {
+ .func = bpf_kptr_xchg,
+ .gpl_only = false,
+ .ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
+ .ret_btf_id = BPF_PTR_POISON,
+ .arg1_type = ARG_PTR_TO_KPTR,
+ .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL | OBJ_RELEASE,
+ .arg2_btf_id = BPF_PTR_POISON,
