netdev - Re: [PATCH bpf-next] libbpf: fix call relocation offset calculation bug

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Date:   Tue, 19 Nov 2019 14:30:34 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next] libbpf: fix call relocation offset calculation bug

On Tue, Nov 19, 2019 at 2:16 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Mon, Nov 18, 2019 at 10:21:51PM -0800, Andrii Nakryiko wrote:
> >
> > -static __attribute__ ((noinline))
> > -int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb)
> > +__attribute__ ((noinline))
> > +int test_pkt_access_subprog2(int val, struct __sk_buff *skb)
> >  {
> >       return skb->len * val;
> >  }
>
> Did you run test_progs -n 8?

I ran all of them, but missed that number of failing tests increased.

>
> Above breaks it with:
> 10: (61) r1 = *(u32 *)(r6 +40)
> func 'test_pkt_access_subprog2' doesn't have 6-th argument
> invalid bpf_context access off=40 size=4
>
> The point of the subprog2 is to test the scenario where BTF disagress with llvm
> optimizations.
>

Yeah, right. I should keep test_pkt_access_subprog2 as static then.
Will post v2 with that change.