Re: [PATCH] ppc: Fix BPF JIT for ABIv2

[Alexei Starovoitov]

On 6/21/16 7:47 AM, Thadeu Lima de Souza Cascardo wrote:
> > > The calling convention is different with ABIv2 and so we'll need changes
> > > in bpf_slow_path_common() and sk_negative_common().
> >
> > How big would those changes be? Do we know?
> >
> > How come no one reported this was broken previously? This is the first I've
> > heard of it being broken.
>
> I just heard of it less than two weeks ago, and only could investigate it last
> week, when I realized mainline was also affected.
>
> It looks like the little-endian support for classic JIT were done before the
> conversion to ABIv2. And as JIT is disabled by default, no one seems to have
> exercised it.

it's not a surprise unfortunately. The JITs that were written before
test_bpf.ko was developed were missing corner cases. Typical tcpdump
would be fine, but fragmented packets, negative offsets and
out-out-bounds wouldn't be handled correctly.
I'd suggest to validate the stable backport with test_bpf as well.