Re: [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill

[Daniel Borkmann]

On 1/12/21 4:35 PM, Gilad Reti wrote:
> On Tue, Jan 12, 2021 at 4:56 PM KP Singh <kpsingh@xxxxxxxxxx> wrote:
> > On Tue, Jan 12, 2021 at 10:16 AM Gilad Reti <gilad.reti@xxxxxxxxx> wrote:
> > > Add test to check that the verifier is able to recognize spilling of
> > > PTR_TO_MEM registers.
> >
> > It would be nice to have some explanation of what the test does to
> > recognize the spilling of the PTR_TO_MEM registers in the commit
> > log as well.
> >
> > Would it be possible to augment an existing test_progs
> > program like tools/testing/selftests/bpf/progs/test_ringbuf.c to test
> > this functionality?

How would you guarantee that LLVM generates the spill/fill, via inline asm?

> It may be possible, but from what I understood from Daniel's comment here
>
> https://lore.kernel.org/bpf/17629073-4fab-a922-ecc3-25b019960f44@xxxxxxxxxxxxx/
>
> the test should be a part of the verifier tests (which is reasonable
> to me since it is
> a verifier bugfix)

Yeah, the test_verifier case as you have is definitely the most straight
forward way to add coverage in this case.