On Mon, Sep 1, 2025 at 6:34 AM Puranjay Mohan <puranjay@xxxxxxxxxx> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> writes:
>
> > On Fri, Aug 29, 2025 at 3:30 AM Xu Kuohai <xukuohai@xxxxxxxxxxxxxxx> wrote:
> >>
> >> > +
> >> > +void bpf_prog_report_arena_violation(bool write, unsigned long addr)
> >> > +{
> >> > + struct bpf_stream_stage ss;
> >> > + struct bpf_prog *prog;
> >> > + u64 user_vm_start;
> >> > +
> >> > + prog = bpf_prog_find_from_stack();
> >>
> >> bpf_prog_find_from_stack depends on arch_bpf_stack_walk, which isn't available
> >> on all archs. How about switching to bpf_prog_ksym_find with the fault pc?
> >
> > Out of archs that support bpf arena only riscv doesn't
> > support arch_bpf_stack_walk(), which is probably fixable.
> > But I agree that direct bpf_prog_ksym_find() is cleaner here.
> > We need to make sure it works for subprogs, since streams[2] are
> > valid only for main prog.
> > I think we can add:
> > struct bpf_prog_aux {
> > ...
> > struct bpf_prog_aux *main_prog;
> > };
> > init it during jit_subprogs() and use it for stream access.
> > We can also remove skipping of subprogs in find_from_stack_cb() then.
> >
> > Kumar, wdyt?
>
> So, IIUC, after adding struct bpf_prog_aux *main_prog_aux in struct
> bpf_prog_aux,
>
> We can do in bpf_prog_alloc_no_stats():
> fp->aux->main_prog_aux = aux;
>
> and in jit_subprogs():
> func[i]->aux->main_prog_aux = prog->aux;
>
> and then all users of bpf_stream_get() can do
> bpf_stream_get(stream_id, prog->aux->main_prog_aux);
>
> with above we can allow find_from_stack_cb() to return subprogs.
> and bpf_prog_ksym_find() can be used in
> bpf_prog_report_arena_violation() without any other changes.
Yes. That's exactly the proposal.
