Re: [External] Re: [PATCH bpf-next 0/5] bpf: make tracing program support multi-attach

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On Wed, Feb 21, 2024 at 11:02 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Tue, Feb 20, 2024 at 6:45 PM 梦龙董 <dongmenglong.8@xxxxxxxxxxxxx> wrote:
> >
> > On Wed, Feb 21, 2024 at 10:35 AM 梦龙董 <dongmenglong.8@xxxxxxxxxxxxx> wrote:
> > >
> > > Hello,
> > >
> > > On Wed, Feb 21, 2024 at 9:24 AM Alexei Starovoitov
> > > <alexei.starovoitov@xxxxxxxxx> wrote:
> > > >
> > > > On Mon, Feb 19, 2024 at 7:51 PM Menglong Dong
> > > > <dongmenglong.8@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > For now, the BPF program of type BPF_PROG_TYPE_TRACING is not allowed to
> > > > > be attached to multiple hooks, and we have to create a BPF program for
> > > > > each kernel function, for which we want to trace, even through all the
> > > > > program have the same (or similar) logic. This can consume extra memory,
> > > > > and make the program loading slow if we have plenty of kernel function to
> > > > > trace.
> > > >
> > > > Should this be combined with multi link ?
> > > > (As was recently done for kprobe_multi and uprobe_multi).
> > > > Loading fentry prog once and attaching it through many bpf_links
> > > > to multiple places is a nice addition,
> > > > but we should probably add a multi link right away too.
> > >
> > > I was planning to implement the multi link for tracing after this
> > > series in another series. I can do it together with this series
> > > if you prefer.
> > >
> >
> > Should I introduce the multi link for tracing first, then this series?
> > (Furthermore, this series seems not necessary.)
>
> What do you mean "not necessary" ?
> Don't you want to still check that bpf prog access only N args
> and BTF for these args matches across all attach points ?

No, I means that if we should keep the

"Loading fentry prog once and attaching it through many bpf_links to
multiple places"

and only keep the multi link.

Both methods need to check the accessed args of the target.





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