On Thu, Nov 2, 2023 at 9:14 AM Vadim Fedorenko
<vadim.fedorenko@xxxxxxxxx> wrote:
>
> On 02/11/2023 15:36, Alexei Starovoitov wrote:
> > On Thu, Nov 2, 2023 at 6:44 AM Vadim Fedorenko
> > <vadim.fedorenko@xxxxxxxxx> wrote:
> >>
> >> On 01/11/2023 23:41, Martin KaFai Lau wrote:
> >>> On 11/1/23 3:50 PM, Vadim Fedorenko wrote:
> >>>>>> +static void *__bpf_dynptr_data_ptr(const struct bpf_dynptr_kern *ptr)
> >>>>>> +{
> >>>>>> + enum bpf_dynptr_type type;
> >>>>>> +
> >>>>>> + if (!ptr->data)
> >>>>>> + return NULL;
> >>>>>> +
> >>>>>> + type = bpf_dynptr_get_type(ptr);
> >>>>>> +
> >>>>>> + switch (type) {
> >>>>>> + case BPF_DYNPTR_TYPE_LOCAL:
> >>>>>> + case BPF_DYNPTR_TYPE_RINGBUF:
> >>>>>> + return ptr->data + ptr->offset;
> >>>>>> + case BPF_DYNPTR_TYPE_SKB:
> >>>>>> + return skb_pointer_if_linear(ptr->data, ptr->offset,
> >>>>>> __bpf_dynptr_size(ptr));
> >>>>>> + case BPF_DYNPTR_TYPE_XDP:
> >>>>>> + {
> >>>>>> + void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset,
> >>>>>> __bpf_dynptr_size(ptr));
> >>>>>
> >>>>> I suspect what it is doing here (for skb and xdp in particular) is
> >>>>> very similar to bpf_dynptr_slice. Please check if
> >>>>> bpf_dynptr_slice(ptr, 0, NULL, sz) will work.
> >>>>>
> >>>>
> >>>> Well, yes, it's simplified version of bpf_dynptr_slice. The problem is
> >>>> that bpf_dynptr_slice bpf_kfunc which cannot be used in another
> >>>> bpf_kfunc. Should I refactor the code to use it in both places? Like
> >>>
> >>> Sorry, scrolled too fast in my earlier reply :(
> >>>
> >>> I am not aware of this limitation. What error does it have?
> >>> The bpf_dynptr_slice_rdwr kfunc() is also calling the bpf_dynptr_slice()
> >>> kfunc.
> >>>
> >>>> create __bpf_dynptr_slice() which will be internal part of bpf_kfunc?
> >>
> >> Apparently Song has a patch to expose these bpf_dynptr_slice* functions
> >> ton in-kernel users.
> >>
> >> https://lore.kernel.org/bpf/20231024235551.2769174-2-song@xxxxxxxxxx/
> >>
> >> Should I wait for it to be merged before sending next version?
> >
> > If you need something from another developer it's best to ask them
> > explicitly :)
> > In this case Song can respin with just that change that you need.
>
> Got it. I actually need 2 different changes from the same patchset, I'll
> ping Song in the appropriate thread, thanks!
>
Please also check my ramblings in [0]
[0] https://patchwork.kernel.org/project/netdevbpf/patch/20231024235551.2769174-2-song@xxxxxxxxxx/
