On Wed, 7 Sep 2022 17:02:51 -0700 Joanne Koong <joannelkoong@xxxxxxxxx> wrote:
> Add a new helper, bpf_dynptr_clone, which clones a dynptr.
>
> The cloned dynptr will point to the same data as its parent dynptr,
> with the same type, offset, size and read-only properties.
[...]
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 4ca07cf500d2..16973fa4d073 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -5508,6 +5508,29 @@ union bpf_attr {
> * Return
> * The offset of the dynptr on success, -EINVAL if the dynptr is
> * invalid.
> + *
> + * long bpf_dynptr_clone(struct bpf_dynptr *ptr, struct bpf_dynptr *clone)
> + * Description
> + * Clone an initialized dynptr *ptr*. After this call, both *ptr*
> + * and *clone* will point to the same underlying data.
> + *
How about adding 'off' and 'len' parameters so that a view ("slice") of
the dynptr can be created in a single call?
Otherwise, for a simple slice creation, ebpf user needs to:
bpf_dynptr_clone(orig, clone)
bpf_dynptr_advance(clone, off)
trim_len = bpf_dynptr_get_size(clone) - len
bpf_dynptr_trim(clone, trim_len)
This fits the usecase described here:
https://lore.kernel.org/bpf/20220830231349.46c49c50@blondie/
