On Fri, Nov 17, 2023 at 1:53 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> On Fri, 2023-11-17 at 11:47 -0500, Andrii Nakryiko wrote:
> [...]
> > > +SEC("?raw_tp")
> > > +__success __log_level(2)
> > > +/* Check that last verified exit from the program visited each
> > > + * callback expected number of times: one visit per callback for each
> > > + * top level bpf_loop call.
> > > + */
> > > +__msg("r1 = *(u64 *)(r10 -16) ; R1_w=111111 R10=fp0 fp-16=111111")
> > > +/* Ensure that read above is the last one by checking that there are
> > > + * no more reads for ctx.i.
> > > + */
> > > +__not_msg("r1 = *(u64 *)(r10 -16) ; R1_w=")
> >
> > can't you enforce that we don't go above 111111 just by making sure to
> > use r1 - 111111 + 1 as an index into choice_arr()?
> >
> > We can then simplify the patch set by dropping __not_msg() parts (and
> > can add them separately).
>
> Well, r1 could be 0 as well, so idx would be out of bounds.
> But I like the idea, it is possible to check that r1 is either 00000,
> 100000, ..., 111111 and do something unsafe otherwise.
then why not `return choice_arr[r <= 111111 ? (r & 1) : -1];` or
something along those lines?
> Thank you. I'll drop __not_msg() then.
yep, thanks
>
>
